M2 - Diameter - 150 light-years, contains about 150,000 stars, and is "one of the richer and more compact globular clusters." At about 36,000 light years, it lies well beyond the Galactic Center. Its brightest stars are red and yellow giants of magnitude 13.1, while its horizontal branch stars have an apparent brightness of 16.1.  M2 was discovered by Maraldi on September 11, 1746; Messier independently rediscovered it exactly 14 years later, on September 11, 1760.

Globular Cluster in Canes Venatici.  One of the most outstanding globular clusters, containing an estimated half million stars! It is extremely rich in variable stars with 212 variables, more than in every other globular cluster in our Milky Way galaxy (and thus the most ever observed).

Globular Cluster in Scorpius is one of the nearest globular clusters in the sky; according to newer results its distance is perhaps only about 7,000 light years.  M4 can be detected by the naked eye under very dark skies and is prominent with the slightest optical aid.

As a remarkable detail, M4 displays a central "bar" structure. It is enshrouded in heavy clouds of dark stellar matter.  Otherwise it would be a spectacular cluster. Its angular diameter is nearly that of the full Moon or a linear diameter of about 55 light years.  It is one of the most open, or loose, globulars.   It is receding at 65 km/sec and contains at least 43 known variables. It was discovered by de Cheseaux in 1745-46.  In 1987, the first millisecond pulsar was discovered in this globular cluster. This pulsar, 1821-24, is a neutron star rotating (and pulsating) once every 3.0 milliseconds, or over 300 times per second, which is even 10 times faster than the Crab pulsar in M1.

Globular Cluster in Serpens  -  One of the oldest globular clusters, with a computed age of 13 billion years. Its diameter is about 130 light years. It's distance is 23,000 light years. M5 is receding from us at about 50 km/sec. M5 contains the considerably large number of 105 known variable stars, one of them is a dwarf nova.

is an Open Cluster in Scorpius called the Butterfly Cluster.   There are 80 cluster members in M6. The diameter is about 20 light years. Its age is estimated to 100 million years according to Burnham, and to 51 million years according to the Sky Catalog 2000.

"M7 is a large and brilliant group, easily detected with the naked eye... the cluster is seen projected on a background of numerous faint and distant Milky Way stars." (Burnham).

This cluster was found by Ptolemy in about 130 AD.  He described it as the "nebula following the sting of Scorpius".  It consists of 80 stars brighter than mag. 10 in a field of about 1.3 degrees apparent diameter, which at its distance of perhaps 800 light years and is approaching us at 14 km/sec. M7's is about  220 million years old, according to the Sky Catalog 2000.  M7's integrated apparent magnitude is between 3.3 and 5.0.

Diffuse Nebula M8 is an emission nebula, in Sagittarius and is commonly referred to as the  Lagoon Nebula.  It was discovered by Flamsteed about 1680. One of the remarkable features of the Lagoon Nebula is the presence of dark nebulae known as 'globules', which are collapsing proto-stellar clouds with diameters of about 10,000 AU. Within the brightest part of the Lagoon Nebula, a remarkable feature can be seen, which according to its shape is called the "Hourglass Nebula". This feature occurs in a region where a vivid star formation process appears to take place. The bright emission is caused by heavy excitation of very hot, young stars. Closely by this feature is the apparently brightest of the stars associated with the Lagoon Nebula, 9 Sagittarii (mag 5.97, spectral class O5), which surely contributes a lot of the high energy radiation which excites the nebula to shine. The young open cluster NGC 6530 associated with the Lagoon Nebula is detached but only weakly concentrated toward its center, its stars scatter in a moderate range of brightness, it is moderately rich (50--100 stars), and associated with nebulosity (certainly, with the Lagoon nebula). As the light of its member stars show little reddening by interstellar matter, this cluster is probably situated just in front of the Lagoon Nebula. Its brightest star is a 6.9 mag hot O5 star, and Eichler gives its age as 2 million years.

Globular Cluster M9 in Ophiuchus is one of the nearer globular clusters to the nucleus of our Galaxy, with a computed distance of 5500 light-years from the Galactic Center. Its diameter is 70 light years and its distance is about 26,000 light years from our Solar system. To the north and west, its light is significantly dimmed by interstellar dust, as it lies at the edge of a patch of dark nebula; its light is probably weakened by at least one magnitude (a factor of about 2.5). M9 is receding from us at the very high velocity of 224 km/sec. 13 variables have been found in this cluster.

Globular Cluster M10 in Ophiuchus is a 7th mag globular cluster about 15.1 arc minutes in diameter, more than half the diameter of the full moon. At its distance of 16,000 light years, this corresponds to a linear diameter of 70 light years. Its bright core, however, is only little more than half as large. It is receding at 69 km/sec. Its central region appears pear-shaped, with a grainy texture; the outer regions show brighter knots at medium magnification (120x).

Open Cluster M11 in Scutum is referred to as the Wild Duck Cluster.  It is "One of the richest and most compact of the galactic clusters." (Burnham). M11 contains an estimated 2900 stars, about 500 of which are brighter than mag 14. An observer at the center of M11 would see several hundred first magnitude stars! The age of the Wild Duck cluster has been estimated to around 220 million years. It is receding at 22 km/sec. M11 was discovered by the German astronomer Gottfried Kirch of the Berlin observatory in 1681.

Globular Cluster M12 (NGC 6218), class IX, in Ophiuchus

M12 is nearly a twin of its apparent neighbor, M10, and is only slightly larger and an idea fainter. Nevertheless, it was once believed to be an intermediate type between globular and dense open clusters (like M11), as it is not very concentrated. At its distance of about 18,000 light years, the apparent diameter of M12 of 14.5 arc minutes corresponds to about 75 light years. This stellar swarm is approaching us at 16 km/sec.

Globular Cluster M13 (NGC 6205), class V, in Hercules

Hercules Globular Cluster

M13, also called the `Great globular cluster in Hercules', is one of the most prominent and best known globulars of the Northern celestial hemisphere. It was discovered by Edmond Halley in 1714, who noted that `it shows itself to the naked eye when the sky is serene and the Moon absent.' It is of 22,200 light years distant, with a diameter of 150 light years. It contains several hundred thousand stars. Toward its center, stars are about 500 times more concentrated than in the solar neighborhood. The age of M13 has been determined to be 14 billion years old.

Globular cluster M13 was selected in 1974 as a target for one of the first radio messages addressed to possible extra-terrestrial intelligent races, and sent by the big radio telescope of the Arecibo Observatory. This message will take about 23,000 years to reach the cluster, so that an answer cannot be expected for 46,000 years. Nearby, about 40 arc minutes north-east, is the faint (mag 11) galaxy NGC 6207, visible in many large- and medium-size-field photographs of M13.

Globular Cluster M14 (NGC 6402), class VIII, in Ophiuchus

M14 is a slightly elliptically shaped stellar swarm, about 55 light years across and 23,000 light years away. It lacks a dense central condensation (Burnham), and contains a considerably large number of over 70 variables. It was the second known nova in a globular cluster after that of 1860 in M80, T Scorpii, and the first one ever photographed. Globular cluster M14 was the first CCD image taken, according to The Sky advertising.

Globular Cluster M15 (NGC 7078), class IV, in Pegasus

This cluster has the third rank in known variable star population, after M3 and Omega Centauri, with 112 variables identified. M15 is perhaps the densest of all (globular) star clusters in our Milky Way galaxy. The Hubble Space Telescope has photographically resolved its super-dense core. M15's core has undergone a process of contraction called "core collapse", which is common in the dynamical evolution of globular. Of the 147 known globular clusters within our Milky Way Galaxy, 21 have been found to contain a collapsed core. The one in M15 would be among the nearest and better observable to us, being only little more remote than the Galactic Center and much less obscured by interstellar matter. Although the true nature of these objects remains obscure for the moment, many scientists believe they are strong candidates for "Black Holes".

Open Cluster M16 (NGC 6611), type 'e', in Serpens

associated with the Eagle Nebula

Lying some 7,000 light years distant in the constellation Serpens and in the next inner spiral arm of the Milky Way galaxy from us, a great cloud of interstellar gas and dust has entered a vivid process of star formation. Open star cluster M16 has formed from this great gaseous and dusty cloud, the diffuse Eagle Nebula IC 4703, which is caused to shine by emission light, excited by the high-energy radiation of its massive hot, young stars. This stellar swarm is only about 5.5 million years old with star formation still active in the Eagle Nebula. This results in the presence of very hot young stars of spectral type O6.

Diffuse Nebula M17 (NGC 6618), an emission nebula, in Sagittarius

Omega, Swan, Horseshoe, or Lobster Nebula

The Omega Nebula M17, also called the Swan Nebula, the Horseshoe Nebula, or the Lobster Nebula, is a region of star formation and shines by excited emission, caused by the higher energy radiation of young stars. Star formation is either still active in this nebula, or ceased very recently. A small cluster of about 35 bright but obscured stars seems to be embedded in the nebulosity. The color of the Omega nebula is reddish, with some graduation to pink. This phenomenon is apparently a result of a mixture of emission light from the hottest gas, together with reflections of the bright starlight from the dust in this region. The nebula contains a large amount of dark obscuring material, which is obvious in its remarkable features. The mass of the gas has been estimated to about 800 times that of the Sun, enough for forming a conspicuous cluster. While the bright nebula seems to be roughly 15 light years in extension, the total gaseous cloud, including low-luminosity material, seems to extend to at least 40 light years. Distance estimates are spread over a wide range, but modern values are between 5,000 and 6,000 light years, thus little less than that of its apparent neighbor, M16 with the Eagle nebula -- apparently, these two star forming regions are indeed close together, in the same spiral arm of the Milky Way galaxy.

Open Cluster M18 (NGC 6613), type 'd', in Sagittarius

M18 is best observed in small telescopes, which show over a dozen of fairly bright stars (the Sky Catalog 2000 lists it with 20 members). Its distance is about according to Sky Catalog 2000 has 3,900 light years, which puts its linear diameter at about 17 light years. This cluster is quite young; its age is estimated at 32 million years.

Globular Cluster M19 (NGC 6273), class VIII, in Ophiuchus

M19 is the most oblate known globular cluster. While about 27,000 light years away from our Solar System, it is quite near to the Galactic Center, only about 4,600 light years. William Herschel was the first to resolve it into "countless stars of mag 14, 15, 16" (John Herschel).

Diffuse Nebulae M20 (NGC 6514), an emission and reflection nebula in Sagittarius also called the Trifid Nebula

The Trifid Nebula M20 is famous for its three-lobed appearance. That he numbered this object at all may have its reason in the fact that Messier merely described it as `Cluster of Stars'. The name `Trifid' was first used by John Herschel to describe this nebula. The red emission nebula with its young star cluster near its center is surrounded by a blue reflection nebula which is particularly conspicuous to the northern end. The nebula's distance is rather uncertain, with values between 2,200 light years and about 7,600 light years. All are extremely hot. The presence of a considerably bright triplet makes brightness estimates for the nebula difficult. In the sky M20 is situated roughly 2 degrees northwest of the larger Lagoon Nebula M8, so that both nebulae form a nice target for wide field photographs.

Open Cluster M21 (NGC 6531), type 'd', in Sagittarius

M21 is a cluster which shows quite a strong concentration toward its center. According to Burnham there are 57 stars. The cluster is very young at an estimated 4.6 million years. The distance of this cluster according to Sky Catalog 2000 puts it at 4,250 light years.

Globular Cluster M22 (NGC 6656), class VII, in Sagittarius

This was probably the first globular cluster discovered, by A. Ihle in 1665. M22 is a very remarkable object; lying 10,000 light years distant, with a width of about 65 light years. It is visible to the naked eye for observers at not too northern latitudes, as it is brighter than the Hercules globular cluster M13. M22 is one of the nearer globular clusters at 10,000 light years. There are over 70,000 stars in this great stellar swarm. The brightest stars are about mag 11. The stars are spread over a region roughly 200 light years in diameter, and receding from us at 144 km/sec.

Open Cluster M23 (NGC 6494), in Sagittarius

Open cluster M23 is another glorious sight for small telescopes and binoculars in the summer Milky Way. At a distance of 2,150 light years, the apparent diameter of this 6-7th mag object, 27 arc minutes, corresponds to about 15 light years.

Milky Way Patch M24 (contains NGC 6603) in Sagittarius

Sagittarius Star Cloud, Delle Caustiche

Messier object number 24 is not a "true" deep sky object, but a huge star cloud in Milky Way, a pseudo-cluster of stars spread thousands of light years along the line of sight, perceived through a chance tunnel in the interstellar dust. The interstellar dust generally dims the light of stars behind it. But the dust is patchy. For some unknown reason it clumps in clouds typically 25 light years across: many such clouds can be clearly distinguished, projected against the star cloud. There are typically two such clouds in a line of sight 1,000 light years long in the Milky Way. But even over the 30,000 light-years to the central regions of the Galaxy there could be, and by chance are, clearer windows than normal in the interstellar medium. M 24 is in effect one of these windows. Although this is what Messier discovered, it is interesting that, within this stellar cloud which is easily visible to the naked eye, there's a dim open cluster, NGC 6603, of magnitude 11. This 11.4 mag cluster consists of about 30 stars in a field of about 5 arc minutes in diameter, and is about 9400 light years remote. Thus its linear diameter should be about 14 light years. The hottest stars are about B9 (pointing to an intermediate age of several 100 million years).

Open Cluster M25 (IC 4725), in Sagittarius

Although a conspicuous cluster, even in the smallest telescopes or opera glasses, M25 has only obtained an IC number. This is because due to unknown reason, John Herschel did not include it in his General Catalog, although it had been observed by de Cheseaux in 1745-46, Messier in 1764, as well as by Bode (1774-77) and Admiral Smyth (1836). It was finally rediscovered by Schmidt in 1866 and added to the second Index Catalog in 1908, using a position obtained by Bailey. It moreover contains the Cepheid variable U Sagittarii, which has a period of 6.74 days, a typical period for these variables "in our neighborhood," as Cecilia Payne-Gaposhkin put it. It was discovered by J.B. Irwin in 1956, its membership was confirmed by radial velocity measurements conducted by M.W. Feast of Radcliffs Observatory. Its age may be about 90 million years (the Sky Catalog 2000 gives 89 million). The sources agree unusually good in this cluster's distance and give about 2,000 light years.

Open Cluster M26 (NGC 6694), type 'f', in Scutum

This is a tight, beautiful cluster with brightest stars of mag 11.9. Burnham mentions about 25 stars visible in 6-8 inch scopes and about 70 fainter members. Its diameter of 22 light-years appear as 15 arc minutes from the 5,000 light years distance. The Sky Catalogue 2000 gives a calculated age of 89 million years for this cluster.

Planetary Nebula M27 (NGC 6853), type 3a+2, in Vulpecula

Dumbbell Nebula

The Dumbbell Nebula M27 was the first planetary nebula ever discovered. On July 12, 1764, Charles Messier discovered this new and fascinating class of objects. We happen to see this one approximately from its equatorial plane; from near one pole, it would probably have the shape of a ring, and perhaps look like we view the Ring Nebula. This planetary nebula is certainly the most impressive object of its kind in the sky, as the angular diameter of the luminous body is nearly 6 arc minutes, with a faint halo extending out to over 15', half the apparent diameter of the Moon. It is also among the brightest, being at most little less luminous with its estimated apparent visual magnitude 7. The bright portion of the nebula is apparently expanding at a rate of 6.8 arc seconds per year, leading to an estimated age of 3000 to 4000 years, i.e. the shell ejection probably would have been observable this time ago (it actually happened earlier as the light had to travel all the distance of perhaps about 1000 light years). The central star of M27 is quite bright at mag 13.5, and an extremely hot blueish subdwarf-dwarf at about 85,000 K. As for most planetary nebulae, the distance of M27 (and thus true dimension and intrinsic luminosity) is not very well known. Current estimates reach from 490 to 3500 light years. Currently, investigations with the Hubble Space Telescope are under work to determine a more reliable and accurate value for the distance of the Dumbbell Nebula.

Globular Cluster M28 (NGC 6626), in Sagittarius

At about 15,000 or 19,000 light years distance, M28 with its linear diameter of 75 light years appears considerably smaller and more compressed than its more impressive neighbor, M22. It is slightly elliptical shaped. To resolve it into stars, larger instruments are required; it was William Herschel who first described it as a "star cloud". M28 was the second globular clusters where a millisecond pulsar was discovered, in 1987 (the first was M4). This one, 1620-26, is spinning around its axis once every 11 milliseconds.

Open Cluster M29 (NGC 6913), type 'd', in Cygnus

M29 is a rather coarse and less impressive cluster, situated in the highly crowded area of Milky Way near Gamma Cygni, at a distance of 4,000 to 7,200 light years. W.A. Hiltner of Yerkes Observatory, in 1954, found the light of its stars rather polarized by interstellar matter, which is apparently 1,000 times denser around this cluster and may absorb so much light that the cluster would be 3 magnitudes brighter if viewed "freely"! M29 is approaching us at 28 km/sec. Its age is estimated at 10 million years.

Globular cluster M30, at roughly 25,000 light years distance and about 70 light years across, has only about 12 known variables, and is approaching us at 164 km/sec. It is fairly dense and a fine object in even small scopes. M30 is less loved by Messier Marathoners, as it is often the last missed object of an almost-complete Messier Marathon, a tour for viewing all Messier objects in one night (which is possible near the end of March in moonless nights).

Spiral Galaxy M31 (NGC 224), type Sb, Andromeda Galaxy

M31 is the famous Andromeda galaxy, our nearest large neighbor galaxy, forming the Local Group of galaxies together with its companions (including M32 and M110, two bright dwarf elliptical galaxies), our Milky Way and its companions, M33, and others. Visible to the naked eye even under moderate conditions, this object was known as the "little cloud" to the Persian astronomer. Charles Messier was obviously unaware of this early report and ascribed its discovery to Simon Marius, who was the first to give a telescopic description in 1612. It was long believed that the "Great Andromeda Nebula" was one of the closest nebulae. In 1912, V.M. Slipher of Lowell Observatory measured the radial velocity of the Andromeda "nebula" and found it the highest velocity ever measured, about 300 km/sec in approach. The brightest of the more than 300 globular clusters of the Andromeda Galaxy M31, is also the most luminous globular in the Local Group of Galaxies; its apparent visual brightness from Earth is still about 13.72 magnitude. It outshines even the brightest globular in our Milky Way, Omega Centauri, and can be glimpsed even by better-equipped amateurs under very favorable conditions, with telescopes starting at 10-inch aperture. Its mass was estimated at 300 to 400 billion times that of the sun. Compared to the newer estimates for our Milky Way galaxy, this is considerably less than the mass of our galaxy, implying that the Milky Way may be much denser than M31. The Hubble Space Telescope has revealed that the Andromeda galaxy M31 has a double nucleus, probably because it has "eaten" a smaller galaxy, which once intruded its core.

Elliptical Galaxy M32 (NGC 221), type E2, in Andromeda

A Satellite of the Andromeda Galaxy, M31

M32 is the small yet bright companion of the Great Andromeda galaxy, M31, and a member of the Local Group of galaxies. It is an elliptical dwarf of only about 3 billion solar masses, and a linear diameter of some 8,000 light years, very small compared to its giant spiral-shaped neighbor. Nevertheless, its nucleus is of comparable properties as that of M31: About 100 million solar masses, are in rapid motion around a central super-massive object. M32 and the other bright companion of M31, M110, are the closest bright elliptical galaxies to us. Remarkably, M32 has no globular clusters. One recent nova was discovered in M32 on August 31, 1998 within the Lick Observatory Supernova Search Program by a team of astronomers from the University of California at Berkeley. M32 was the first elliptical galaxy ever discovered, by Le Gentil on October 29, 1749.

Spiral Galaxy M33 (NGC 598), type Sc, in Triangulum

Triangulum Galaxy

The Triangulum galaxy M33 is another prominent member of the Local Group of galaxies. M33 was probably first found by Hodierna before 1654 and independently rediscovered by Messier in 1764. This is one of the largest H II regions known at all: it has a diameter of nearly 1500 light years, and a spectrum similar to the Orion nebula M42. W.L. Freedman, C.D. Wilson, have revealed that M33 is at a slightly greater distance from us than the Andromeda Galaxy M31. It is about 50,000 light years, half the diameter of the Milky Way. However, the faintest out-layers seem to reach farther out, so that the true diameter may be at least 60,000 light years. The mass of the Triangulum Galaxy has been estimated between 10 and 40 billion solar masses. For the observer, this galaxy can be glanced with the naked eye under exceptionally good conditions; it is the most distant object visible to the naked eye. It is outstanding in good binoculars, but as its considerable total brightness is distributed quite evenly over an area of nearly four times that covered by the full Moon, its surface brightness is extremely low. Therefore, it is difficult to impossible to view this galaxy in telescopes which do not allow low magnification - lowest is best for this object!

Open Cluster M34 (NGC 1039), in Perseus

This intermediate aged (190 million years according to the Sky Catalog 2000) open cluster of about 100 stars lies about 1,400 light years with a diameter of 14 light years. The age of M34 was estimated at 190 million years by Sky Catalog 2000.

Open Cluster M35 (NGC 2168), type 'e', in Gemini

Open star cluster M35 consists of over 200 stars scattered over the area covered by the full Moon (30'). Its distance is 2,800 light years with a diameter of about 24 light years. It’s about 110 million years old and approaching at 5 km/sec. Even the naked eye finds this cluster easily near the 3 "foot stars" of Gemini under fairly good observing conditions. The slightest optical instrument will resolve the brighter stars and make it a splendid view at low magnifications, a nearly circular cluster with rather uniform stellar distribution. Amateurs with more powerful telescopes can view its fainter neighbor, NGC 2158.

Open Cluster M36 (NGC 1960), in Auriga

This is the first of three bright open clusters in the southern part of constellation Auriga, included in Messier's catalog (the other two are M37 and M38). All 3 were first recorded by Giovanni Batista Hodierna before 1654, however these discoveries came to light as late as 1984, so that Le Gentil has independently rediscovered it. M36 is about 4,100 light years distant with a diameter of about 14 light years. It has about 60 proven members. The luminosity of the brightest member is about 360 times that of the Sun. As it is quite young (about 25 million years), it contains no red giants.

Open Cluster M37 (NGC 2099), type 'f', in Auriga

M37. Charles Messier discovered it on September 2, 1764. M37 contains about 150 stars brighter than mag 12.5, and perhaps a total of over 500 stars. As indicated by the fact that it has a considerable number (at least a dozen) of red giants, it’s estimated age is about 300 million years. Its distance is given by Burnham at 4,700 light years. Its apparent diameter is about 20 to 25 light years.

Open Cluster M38 (NGC 1912), in Auriga

Lying only 2.5 degree northwest (preceding) of M36, this cluster was silently discovered by Hodierna before 1654, and independently found by Le Gentil in 1749. Its brightest stars form a pattern resembling the Greek letter Pi, or (according to Webb) an "oblique cross". At its distance of 4,200 light years, its diameter is about 25 light years. It is of intermediate age (about 220 million years according to the Sky Catalog 2000). Its brightest member has an absolute magnitude of -1.5, or a luminosity of 900 suns. For comparison, the Sun would appear as faint as only mag 15.3 from the distance of M38!

Open Cluster M39 (NGC 7092), in Cygnus

M39 is a very large but very loose open cluster, situated some 9 degrees east and a bit north of Deneb (Alpha Cygni). Its distance is only about 800 light years, and it is of intermediate age (estimates between 230 and 300 million years). 30 stars are proven members and contained in a volume of about 7 light years diameter. This cluster is best observed with lowest powers.

M 40 Double Star M40 (WNC 4) Ursa Major

This faint double star was found by Charles Messier in the 17th-century. M40 was apparently the last one he recorded when he was busy in checking the reports available to him in 1764. Receding at 2885 km/s corresponds to about 125 million light years distance.

Open Cluster M41 (NGC 2287), in Canis Major

M41 is lying about 4 degrees nearly exactly south of Sirius, the brightest star in the sky. It contains about 100 stars and situated near the cluster's center. This star is about 700 times more luminous than our Sun. The stars are distributed over a volume about 25 or 26 light years, and all receding from us at 34 km/sec. As they are at a distance of 2,300 light years, they appear scattered over an area of 38 arc minutes diameter. The age of M41 was estimated at 190 million years (Sky Catalog 2000). C.E. Barns mentions that M41 was "possibly" recorded by Aristotle about 325 B.C.; this would make it the "faintest object recorded in classical antiquity" (from Burnham).

Diffuse Nebula M42 (NGC 1976), an emission and reflection nebula

The Orion Nebula is one of the most interesting objects in the sky. To the naked eye, it looks like a star in the sword of the constellation Orion, but with binoculars or a telescope, you can see that it is actually a large glowing cloud of material. This is believed to be a huge star formation region about 1630 light years away. The bright part of the nebula is the glow of many luminous, newborn stars shining on the surrounding gas cloud that they collapsed from. The most important part of the Orion Nebula is the part we can't see: the opaque Orion Molecular Cloud. This is a huge clump of very cold gas that has a total mass of about 2000 times the mass of the Sun. The gas from this cloud slowly collapses due to gravity to form stars. Whenever a bright, new star is formed, its light evaporates the opaque gaseous "womb" it formed from, allowing us to see it. The stars that are being born in the Orion Nebula are part of what astronomers call an "open cluster." When all of the stars are done being born, what will remain is a clump of a few hundred to a thousand stars which are all roughly the same age (give or take a few tens of millions of years!). These stellar siblings are dominated by a few very massive, very very bright stars called the Trapezium. The Trapezium is made up of just a few stars, but it outshines all the rest of them combined. Astronomers believe that the majority of the glow from the gas in the nebula comes from light from the stars of the Trapezium. Maybe in a few hundred million years, there will be planets like the Earth forming around some of the new stars in the cluster.

Diffuse Nebula M43 (NGC 1982), an emission and reflection nebula, in Orion

De Mairan's Nebula, part of Orion Nebula

M43 is actually a part of the Great Orion Nebula, M42, which is separated from the main nebula by an impressive, turbulent dark lane. The diffuse nebula M43 surrounds the irregular young "nebula variable" NU Orionis of magnitude 6.5-7.6. It seems that M43 is excited to shine by this star, and contains its own, separate small cluster of stars, which have formed in this part of the Orion nebula. The dark features along its eastern border are well visible in telescopes starting at about 8 inch. The nebula itself is a fine view even in a 4-inch.

Open Cluster M44 (NGC 2632), type 'd', in Cancer

Beehive Cluster, Praesepe

This famous cluster, M44, is also called Praesepe (Latin for "manger"), or the Beehive cluster. It is also one of the objects easily visible to the naked eye, and thus known since prehistoric times. Galileo has first resolved this "nebulous" object, and reported: "The nebula called Praesepe, which is not one star only, but a mass of more than 40 small stars." With larger telescopes, more than 200 of the 350 stars in the cluster area have been confirmed as members. The cluster is 577 light years distant, and its age was estimated at about 400 million years.

M45 Open Cluster, type 'c', in Taurus

Pleiades

The Pleiades are among those objects which are known since the earliest times. At least 6 member stars are visible to the naked eye, while under moderate conditions this number increases to 9, and under clear dark skies jumps up to more than a dozen. Homer mentions them in his Odyssee, and the Bible has three references to the Pleiades. The Pleiades also carry the name "Seven Sisters". Their Japanese name is "Subaru", which was taken to christen the car of the same name. Burnham points out that the name `Pleiades' may be derived from either the Greek word for `to sail', or the word `pleios' meaning `full' or `many'. According to Greek mythology, the main, visible stars are named for the seven daughters of "father" Atlas and "mother" Pleione: Alcyone, Asterope (a double star), Electra, Maia, Merope, Taygeta and Celaeno. Modern observing methods have revealed that at least about 500 mostly faint stars belong to the Pleiades star cluster, spread over a 2 degree (four times the diameter of the Moon) field. Their density is pretty low, compared to other open clusters. This is one reason why the life expectation of the Pleiades cluster is also pretty low (see below). The age of the Pleiades star cluster amounts 100 million years. The distance of the Pleiades cluster are at a distance of 380 light years. Some of the Pleiades stars are rapidly rotating, at velocities of 150 to 300 km/sec at their surfaces, which is common among main sequence stars of a certain spectral type (A-B). Due to this rotation, they must be (oblate) spheroids rather than spherical bodies. From the theory of stellar evolution, it follows that white dwarfs cannot have masses above a limit of about 1.4 solar masses (the Chandrasekhar limit), as they would collapse due to their own gravitation if they were more massive. But stars with such a low mass evolve so slow that it takes them billions of years to evolve into that final state, not only the 100 million year age of the Pleiades cluster. The only possible explanation seems to be that these WD stars were once massive so that they evolved fast, but due to some reason (such as strong stellar winds, mass loss to close neighbors, or fast rotation) have lost the greatest part of their mass. Possibly they have, in consequence, lost another considerable percentage of their mass in a planetary nebula. Anyway, the final remaining stars (which was previously the star's core) must have come below the Chandrasekhar limit, so that they could go into the stable white dwarf end state, in which they are now observed. New observations of the Pleiades since 1995 have revealed several candidates of an exotic type of stars, or star-like bodies, the so-called Brown Dwarfs. These hitherto hypothetical objects are thought to have a mass intermediate between that of giant planets (like Jupiter) and small stars (the theory of stellar structure indicates that the smallest stars, i.e. bodies that produce energy by fusion somewhere in their lifetime, must have at least about 6 to7 percent of one solar mass, i.e. 60 to 70 Jupiter masses). So brown dwarfs should have 10 to about 60 times the mass of Jupiter. They are assumed to be visible in the infrared light, have a diameter of about or less that of Jupiter (143,000 km), and a density 10 to 100 times that of Jupiter, as their much stronger gravity presses them tougher together.

Open Cluster M46 (NGC 2437), type 'f', in Puppis

M46 was the first object Messier discovered after he had published the first edition of his list (M1-M45), on February 19, 1771, three days after presenting it to the academy.

The cluster is very rich, with 150 stars of mag 10-13 and probably a total population of over 500. The brightest of these stars are each about 100 times more luminous than the Sun (the brightest is of apparent magnitude 8.7). This indicates an age of about 300 million years. The members are scattered over 30 light years at a distance of 5,400 light years, and receding at 41.4 km/sec. As a special and famous feature a planetary nebula (NGC 2438, also FC 87) appears within the apparent borders of M46.

Open Cluster M47 (NGC 2422), type 'd', in Puppis

M47 was discovered before 1654 by Hodierna, remained secret until 1984 when his book came to light. Open cluster M47 is a bright cluster which can be glimpsed with the naked eye under good conditions as a dim nebulosity. It is a coarse cluster of bright stars, and contains about 50 stars in a region 12 light years in. Its distance is about 1,600 light years, so that the stars of M47 appear scattered over an area in the sky of the same size as the full moon, 30 arc minutes. It also contains two orange K giants with luminosity of about 200 times that of the Sun each. The Sky Catalog 2000 estimates the age of 78 million years for this stellar swarm and is receding from us at 9 km/sec.

Open Cluster M48 (NGC 2548), in Hydra

This open cluster was discovered by Charles Messier on February 19, 1771. However, as he did an error in data reduction, he gave a wrong position in his catalog so that the object was missing until 1959 when it was identified by T.F. Morris. M48 is a quite conspicuous object and should be a naked-eye object under good conditions. The smallest binocular, or telescopes, show a large group of about 50 stars brighter than mag 13, the total number being at least 80. The age of M48 was estimated to amount about 300 million years.

Elliptical Galaxy M49 (NGC 4472), type E4, in Virgo

Elliptical galaxy M49 was the first member of the Virgo cluster of galaxies discovered, by Charles Messier on February 19, 1771. It is also one of the brightest with its mag 8.5. Its distance is about 60 million light years. It is one of the giant elliptical galaxies in this great cluster (besides M60 and M87). It is an elliptical galaxy with the major axis of nearly 160,000 light years (we don't know the real extension along the line of sight toward us, of course, as we don't know the spatial orientation of the real ellipsoid axes), so it is actually a big ellipsoid.

This cluster was discovered on April 5, 1772 by Charles Messier. The open cluster M50 is probably about 3,000 light years distant. Its angular diameter of about 15x20' therefore corresponds to a linear extension of about 18 light years, the central dense part being only about 10' or 9 light years in diameter.

Spiral Galaxy M51 (NGC 5194), type Sc, in Canes Venaciti

Whirlpool Galaxy

The famous Whirlpool galaxy M51 was one of Messier's original discoveries: He discovered it on October 13, 1773, when observing a comet. For the amateur, it is easy and a showpiece if the sky is dark, but is quite sensitive for light pollution which easily makes it fade in the background. Under very cood conditions, even suggestions of its spiral arms can be glanced with telescopes starting from 4-inch. Low magnification is best for viewing this pair.

Open Cluster M52 (NGC 7654), type 'e', in Cassiopea

M52 is a fine open cluster located in a rich Milky Way field. Ake Wallenquist (1959) found 193 probable members in a region of 9' radius. The brightest main sequence star of this cluster is of mag 11.0 and spectral type B7. The Sky Catalog 2000 gives an age of only 35 million years. The distance of this cluster is not very well known. The Sky Catalog 2000 gives 5,200 light years. This uncertainty is mainly due to the high interstellar absorption its light has suffered on its way to us, which is complicated to estimate reasonably.

Globular Cluster M53 (NGC 5024), class V, in Coma Berenices

Globular star cluster M53 is one of the more outlying globulars, being about 60,000 light years away from the Galactic center, and slightly more (about 62,600 light years) from our Solar system. Its diameter is over 250 light years. It is rapidly approaching us at 112 km/s. As in all globular clusters, the stars of M53 are apparently "metal-poor", which means that they contain only little quantities of elements heavier than Helium (actually mainly elements like carbon and oxygen); those of M53 are even below the average globular cluster members in "metallicity". At only about 1 degree separation to the east, the faint and quite loose globular cluster NGC 5053 comes into the field of view, which is at nearly the same distance as M53 (55,000 light years), and contains significantly less stars so that its classification as globular was doubted in the past.

Globular Cluster M54 (NGC 6715), class III, in Sagittarius

M54 is a quite conspicuous cluster. It is easy to find as it is close to Zeta Sagittarii, the southernmost star of Sagittarius' "dipper" asterism of 4 or 5 stars (also called the "Milky Dipper" or "Teapot"), namely 0.5 degrees south and 1.5 degrees west. It is bright but small so that it may be overlooked in smaller binoculars (i.e. taken for a star), its bright core being only 2.1' in diameter. M54 has at least 82 known variables, but there are also two semi-regular red variables with periods of 77 and 101 days. In 1994, the exciting discovery was made that M54 was probably not a member of our Milky Way at all, but of a newly discovered dwarf galaxy 50 – 60,000ly distant! This galaxy is now called SagDEG, for Sagittarius Dwarf Elliptical Galaxy, and one of the most recently discovered Local Group galaxies. M54 is receding at about 130 km/sec. At this distance, M54 would be one of the most luminous known globular clusters, outshined only by spectacular Omega Centauri in our Milky Way. Also, its diameter would become as large as about 200 light years. And perhaps most interesting, it would make M54 the first extragalactic globular cluster ever discovered, by Charles Messier on July 24, 1778, and thus add an extra first to Messier's list of fame.

Globular Cluster M55 (NGC 6809), class XI, in Sagittarius

M55 is a quite large globular cluster (roughly 2/3 of the Moon's apparent diameter) but has a loose appearance. It is about 20,000 light years distant with a diameter of about 110 light years. M55 has only very few known variables, 5 or 6. Its total luminosity may be near 100,000 times that of the Sun. M55 was originally discovered by Lacaille in 1751-1752 (his Lac I.14), when he was observing in South Africa.

Globular Cluster M56 (NGC 6779), class X, in Lyra

M56 is located about half-way between Beta Cygni (Albireo) and Gamma Lyrae. It is one of the less bright globulars, especially lacking the bright core which most globulars have. Nevertheless it is not too difficult to resolve, even at its rather large distance. Its diameter is near 60 light years. This stellar swarm is approaching us at the high velocity of 145 km/sec. Only about a dozen of variables were identified in M56.

Planetary Nebula M57 (NGC 6720), type 4+3, in Lyra

The famous ring-nebula M57 is often regarded as the prototype of a planetary nebula, and a showpiece in the northern hemisphere summer sky. Recent research has confirmed that it is a ring of bright light-emitting material surrounding its central star, and not a spherical (or ellipsoidal) shell, as was first assumed by John Herschel. The Ring is exposing a decreasing ionization level with increasing distance from the 100,000 K hot central star. The innermost region appears dark as it emits merely UV radiation, while in the inner visible ring, greenish forbidden light of ionized oxygen and nitrogen dominates the color, and in the outer region, only the red light of hydrogen can be excited. As for most planetary nebulae, the distance to the Ring Nebula M57 is not very well known. As most planetary nebulae, the Ring is much brighter visually at magnitude 8.8 than photographically at only 9.7 mag; a consequence of the fact that most light is emitted in very few particular spectral lines (see the discussion in planetary nebulae at the end of this pamphlet).

Spiral Galaxy M58 (NGC 4579), type SBc, in Virgo

M58 is one of the 4 barred spiral galaxies in Messier's catalog, though it is sometimes classified as intermediate between normal and barred spirals. It is one of the brightest galaxies in the Virgo cluster. Under good conditions, 4-inch or larger scopes show a halo of uneven brightness with condensations, which seem to coincide with brighter areas of the spiral arms. A suggestion of M58's bar may be noticed with telescopes starting from 8-inch, as an "extension of the central nucleus in an EW direction".

Elliptical Galaxy M59 (NGC 4621), type E5, in Virgo

M59 is a member of the Virgo cluster of galaxies, and one of the larger elliptical galaxies there, although it is considerably less luminous and massive than the greatest ellipticals in this cluster, M49, M60 and, above all, M87. At an assumed distance of 60 million light years, its longer axis corresponds to almost 90,000 light years. M59 has a system of 1900 +/- 400 globular clusters, considerably less than the three giants listed above, but still an order of magnitude more than our Milky Way Galaxy.

M60 is one of the giant elliptical galaxies in the Virgo Cluster of galaxies. As the most (eastern) Messier galaxy in this cluster, it is the last in a row of 3 (M58, 59, and 60) which comes into the field of view of a telescope pointed to this region of the sky. At its distance of some 60 million light years, this galaxy's apparent diameter is 120,000 light years. Amateur telescopes, however, do only show its bright central region of about 4x3 arc minutes diameter. Its visually 9th apparent magnitude makes it a very bright galaxy of absolute magnitude -22.3, corresponding to an intrinsic luminosity of 60 billion suns.

Spiral Galaxy M61 (NGC 4303), type SABbc, in Virgo

M61 was discovered by Oriani on May 5, 1779, 6 days before Charles Messier's discovery, who had seen it on the same day as Oriani but mistaken it for the comet. Messier mistook it 2 times more until he realized that it did not move. M61 is one of the larger galaxies in the Virgo cluster with a diameter of about 100,000 light years. Three supernovae have been observed in M61: 1926A (12.8 mag), 1961I (mag 13), and 1964F (mag 12).

Globular Cluster M62 (NGC 6266), class IV, in Ophiuchus

M62 is one of the most irregular shaped globular clusters, as was first reported by Herschel. This deformation may be a result of the fact that M62 is one of the closest of Messier's globulars to the Galactic center (only about 6100 light years), so that it is deformed by tidal forces. M62 is 21,500 light years away. Also M62 has the large number of 89 known variables. The core of M62 is extremely dense and has possibly undergone a core collapse some time in its history. Messier found this cluster in 1771, but took an accurate position only at 1779, so that his entry had this date.

Spiral Galaxy M63 (NGC 5055), type Sb, in Canes Venaciti

Sunflower Galaxy M63 was the very first discovery of a Deep Sky object by Messier's friend, Pierre Mechain, who caught it up on June 14, 1779. The Sunflower galaxy M63 is a spiral displaying a patchy spiral pattern which can be traced well to the periphery of its only 6 arc seconds small smooth-textured central region. Although 6 degrees south, it apparently forms a physical group with M51 and several smaller galaxies, the M51 group, which is about 37 million light years distant. The spiral arms show up as a grainy background, which brightens slowly from outward and then rapidly to the nuclear region, which is still grainy.

Spiral Galaxy M64 (NGC 4826), type Sb, in Coma Berenices

Blackeye Galaxy

M64 is the famous Black Eye galaxy, sometimes also called the ``Sleeping Beauty galaxy". The conspicuous dark structure is a prominent dust feature obscuring the stars behind. M64 may be taken as prototype for a class of galaxies called "ESWAG", for Evolved Second Wave (star forming) Activity Galaxy. The dust feature is well visible even in smaller telescopes. M64 was recently shown to have two counter-rotating systems of stars and gas in its disk: The inner part of about 3,000 light years radius is rubbing along the inner edge of the outer disk, which rotates opposite and extends up to at least 40,000 light years, at about 300 km/sec. This rubbing process is probably the reason for the observed vigorous star formation process, which is currently under way, and can be observed as the blue knots imbedded in the peculiar dust lane on one side of the nucleus. The distance of this galaxy seems to be not very well determined. Burnham has "20-25" million light years. The radial velocity is 377 km/sec. That the distance is not yet better known is a bit strange, as Cepheid variables in this galaxy should be in the reach of current telescopes, perhaps even the largest Earth-bound ones.

Spiral Galaxy M65 (NGC 3623), type Sa, in Leo in the Leo Triplett

M65, together with its neighbors M66 and NGC 3628, forms a most conspicuous triplet of galaxies, the Leo Triplett or M66 group, located at a distance of about 35 million light years. Although it is close to and thus under the gravitational influence of its neighbors, M65 looks like a very "normal" spiral and seems to have felt little influence. It has a prominent central lens and tightly wound spiral arms, plus a prominent dust lane marking the facing edge. Near the lane, some knots are visible, which, may be associated with star forming regions.

Spiral Galaxy M66 (NGC 3627), type Sb, in Leo in the Leo Triplett

M66 is considerably larger than its neighbor, M65, and has a well developed but not well defined central bulge. Its spiral arms are deformed, probably because of the encounters with its neighbors. They are distorted and displaced above the galaxy plane. Much dust is visible as are a few pink nebulae, signs of star formation at the end of one of the arms. Three supernovae have appeared in this galaxy in 1973, 1989, & 1997.

Open Cluster M67 (NGC 2682), type 'f', in Cancer

M67 is one of the oldest known open clusters, and by far the oldest of Messier's open clusters, being aged at 3.2 billion years in the Star Catalog 2000. This is still less than the age of our Solar System, but open clusters usually get destructed much faster. It has been calculated that M67 can expect to exist as a cluster for about another 5 billion years. Few known open clusters have been found to be older such as NGC 6791, which is about 7 billion years old and is currently the oldest known open cluster in our Milky Way galaxy. At this later stage of evolution, the open cluster M67 shows a well-developed red giant branch, while the main sequence ends to the hot blue end. The total number of stars in M67 is probably at least about 500.

Globular Cluster M68 (NGC 4590), class X, in Hydra

This 8-8.4 mag globular cluster lies at 33-40,000 light years, and its members are spread over a volume of about 140 light years diameter. It has at least 42 known variables, and is approaching us at 112 km/sec.

Globular Cluster M69 (NGC 6637), class V, in Sagittarius

M69, similar as its neighbor M70, is one of the smaller and fainter globular clusters in Messier's catalog. M69 was discovered by Abbe Nicholas Louis de la Caille. M69 is roughly 55 light years and is 27,000 light years distance. Its stellar concentration is about average for a globular cluster. M69 is poor in variables.

M70 is 28,000 light years distant and close to the galactic center and is subject to quite strong tidal gravitational forces. It is roughly 65 light years in linear diameter. It is rapidly receding from us, at about 200 km/sec. Only 2 variables are known in this stellar swarm. Globular cluster M70 became famous in 1995 when the great comet Hale-Bopp was discovered near it by Alan Hale and Thomas Bopp as they were observing this globular.

Globular Cluster M71 (NGC 6838), class X-XI, in Sagitta

M71 is a loose globular. According to newer sources, it is 11,700 light years distant. Its denser, easily visible core is only about 5 to 6 arc minutes, corresponding to a linear extension of only 25 light years, small for a globular cluster. However, faint members have been detected out to a total diameter of 24', making it measure 90 light years.

Globular Cluster M72 (NGC 6981), class IX, in Aquarius

M72 is one of the more remote of Messier's globular clusters: At about 53,000 light years, it lies a considerably distance beyond the Galactic center. It is of 9th or 10th apparent magnitude, but as it is so distant it is one of the more intrinsically luminous globular cluster. However, M72 is not very concentrated. It is approaching us quite rapidly, at 255 km/sec, and has the considerable number of 42 known variables. Its diameter is a bit more than 90 light years.

Group or Asterism of 4 Stars M73 (NGC 6994) in Aquarius

M73 consists of 4 stars, 3 of them being of about 10th to 11th magnitude, the fourth (D) being of mag 12.0, it is obviously a true Messier object, as Charles Messier described it as a "Cluster of three or four small stars, which resembles a nebula at first glance, containing very little nebulosity. What remains to clear up to now, at least to the knowledge of the present author, is the check if the 4 stars in M73, or at least some of them, are physically related. There was always a great fraction of astronomers who believed that M73 is an asterism, a chance alignment of 4 stars at different distances. In their Catalog of the Universe: "[The authors] suspect in fact that M 73 might be a real little cluster, for the following reason. On average there are 60 stars per square degree which are brighter than magnitude 12, as are the four stars of M 73. The probability of finding four such stars by chance in a given area of sky one arc minute across (like M 73) is about two chances in a billion. However, there are 150 million such little areas on the sky, so the chances are only one in four that such random asterism exists on the sky. M 73 could be it, but we would gamble that it is a genuine multiple star of some kind."

Spiral Galaxy M74 (NGC 628), type Sc, in Pisces

This conspicuous spiral is a prototype of a grand-design Sc galaxy. Its distance may be about 30 to 40 million light years and recedes at 793 km/sec. Its spiral arms are about 1000 light years broad with a diameter of roughly 95,000 light years. The nucleus is small and bright. M74 is probably the chief member of a very small physical group of galaxies. For the amateur, very good conditions are needed to see more than this nucleus. But if they are given, suggestions of the magnificient spiral arms become apparent in telescopes starting at 4-inch. Messier marathoners often miss this galaxy in the evening, as it stands near the limit of the "Messier-Free Zone" in the sky. Only globular cluster M30 is missed more frequently than this galaxy.

Globular Cluster M75 (NGC 6864), class I, in Sagittarius

At a distance of nearly 60,000 light years, M75 is one of the more remote of Messier's globular clusters, lying well beyond the Galactic center. Some sources give even larger distances, up to as much as 100,000 light years! This would make it the most remote Messier globular, and the most remote galactic Messier object at all. M75 is one of the more compact, concentrated globulars. Because of this and its distance, larger scopes are required to resolve it into stars. Its angular diameter of 6' corresponds to a linear extension of well over 100 light years, and it is of high luminosity, perhaps about 160,000 times that of the Sun (Mag -8.3).

Planetary Nebula M76 (NGC 650), type 3+6, in Perseus

Little Dumbbell Nebula

M76 is among the fainter Messier objects. It is known under the names Little Dumbbell Nebula (the most common), Cork Nebula, Butterfly Nebula, and Barbell Nebula, and it was given two NGC numbers as it was suspected to be a double nebula with two components in contact, a hypothesis brought up by William Herschel. The appearance of M76 resembles to some degree that of the Dumbbell Nebula M27. Today the central star is of mag 16.6 and a high temperature of some 60,000 K, which will probably cool down as a white dwarf over the coming tens of billions of years. As usual for planetary nebulae, M76's visual magnitude is much brighter than photographically. This is due to the fact that most visual light is emitted in one spectral line, the green 5007 Angstrom forbidden line of doubly ionized oxygen, [O III]. The distance is poorly known, with estimates between 1,700 and 15,000 light years. Accordingly, the true dimensions of the cork is between 0.34x0.72 and 3.1x6.4 light years, while the wings extend up to between 1.3 and 11.3 light years, and the faint halo reaches out to between 2.4 and 21 light years.

Spiral Galaxy M77 (NGC 1068), type Sb, in Cetus

Cetus A

This magnificient galaxy is one of the biggest galaxies in Messier's catalog, its bright part measuring about 120,000 light years, but its faint extensions reach nearly 170,000 light years. Its appearance is that of a magnificient spiral with broad structured arms, which in the inner region show a quite young stellar population, but more away from the center, are dominated by a smooth yellowish older stellar population. M77 is about 60 million light years distant, approximately the same distance but another direction as the Virgo Cluster, and is receding from us at about 1100 km/sec, as was first measured by Vesto M. Slipher of Lowell Observatory in 1914; it was the second galaxy with a large measured redshift after the Sombrero galaxy, M104 (R. Brent Tully's Nearby Galaxies Catalog gives a somewhat smaller value for the distance, 47 million light years, and values in other sources are spread both below and above the Virgo Cluster value; the higher values would make M77 the most remote Messier object). This galaxy is unique and peculiar. First of all, its spectrum shows peculiar features in the form of broad emission lines, indicating that giant gas clouds are rapidly moving out of this galaxy's core, at several 100 km/sec. This remarkable class of galaxies is named after its discoverer, Carl K. Seyfert, who described them first in 1943 (Ap.J. 97, 28-40).

An enormous energy source is required to generate this velocity, which must sit in the galaxy's core. Infrared investigations with the 10-meter Keck telescope by Caltech astronomers have revealed a strong point-like source, less than 12 light-years in diameter, and surrounded by an elongated structure of 100 light years extension; these structures were not apparent in the Hubble images in the visible light. M77, as well as other Seyfert galaxies, has been known to be bright infrared radiators since some time.

Diffuse Nebula M78 (NGC 2068), a reflection nebula, in Orion

M78 is the brightest diffuse reflection nebula in the sky. It belongs to the Orion complex, a large cloud of gas and dust centered on the Orion Nebula M42/M43, and is about 1,600 light years distant. It is the brightest portion of a vast dust cloud, which includes NGC 2071, NGC 2067, and very faint NGC 2064. M78 measures almost 4 light years in extension.

Globular Cluster M79 (NGC 1904), class V, in Lepus

M79 is a beautiful globular cluster at a quite unusual location in the sky: Most globulars are grouped around the Galactic center, but this is one of the few which are situated in the other hemisphere, i.e. it is beyond us for hypothetical observers in the central stellar bulge of our Milky Way galaxy. It is little over 40,000 light years from us, but about 60,000 light years from the galactic center. M79's apparent diameter of 8.7 minutes of arc corresponds to a linear extension of over 100 light years. This cluster is slightly elliptical, extended at position angle 45 deg, and has only 7 known variables. It is receding at about 200 km/sec.

M80 is a fine 8th mag globular with an approximate diameter of 95 light years and a distance of 36,000 light years. Its appearance resembles very much that of a comet. On May 21, 1860, a nova occurred in M80, completely changing the appearance of this globular cluster for some days.

Spiral Galaxy M81 (NGC 3031), type Sb, in Ursa Major

Bode's Galaxy

M81 is one of the easiest and most rewarding galaxies to observe for the amateur astronomer on the northern hemisphere, because with its total visual brightness of about 6.8 magnitudes it can be found with small instruments. The pronounced grand-design spiral galaxy M81 forms a most conspicuous physical pair with its neighbor, M82, and is the brightest and probably dominant galaxy of a nearby group called M81 group. A few tens of million years ago, which is semi-recently on the cosmic time scale, a close encounter occurred between the galaxies M81 and M82. During this event, larger and more massive M81 has dramatically deformed M82 by gravitational interaction. The encounter has also left traces in the spiral pattern of the brighter and larger galaxy M81, first making it overall more pronounced, and second in the form of the dark linear feature in the lower left of the nuclear region. The galaxies are still close together, their centers separated by a linear distance of only about 150,000 light years.

Using the Hubble Space Telescope, a team under Wendy Freedman of the Carnegie Institution of Washington has investigated 32 Cepheid variables in M81 and determined the distance to be 11.0 million light years. M81 has probably only little dark matter, as its rotation curve was found to fall off in the outer regions; this is in contrast to many galaxies, including our own Milky Way, for which the rotation curve increases outward. To explain the velocity of the stars in these regions, the galaxy must have a certain amount of mass. However, the total mass observed in luminous matter - stars and nebulae - is insufficient to explain this behavior; thus it is assumed that there is a significant portion of mass in galaxies is non-luminous, dark matter.

Irregular Galaxy M82 (NGC 3034), type Ir-II, in Ursa Major

M82 is the prototype of an irregular of the second type, i.e. a "disk" irregular. Its core seems to have suffered dramatically from a semi-recent close encounter with M81, being in a heavy starburst and displaying conspicuous dark lanes. This turbulent explosive gas flow is also a strong source of radio noise. In the infrared light, M82 is the brightest galaxy in the sky; it exhibits a so-called infrared excess (it is much brighter at infrared wavelengths than in the visible part of the spectrum). As a member of the M81 group, M82 is 12 million light years distant.

Spiral Galaxy M83 (NGC 5236), type SABc, in Hydra

Southern Pinwheel

M83 is about 25 million light years away and is receding at 337 km. This galaxy is sometimes called the "Southern Pinwheel". Five or six supernovae were reported in M83 up to now, more than in any other Messier galaxy: 1923A, 1945B, 1950B, 1968L, 1983N. For years, M83 had been the galaxy with most discovered supernovae, but recently NGC 6946 came up with the same number of 6, or even one more if 1945B should be an error.

Lenticular (S0) Galaxy M84 (NGC 4374), type S0, in Virgo

M84 is situated in the heavily populated inner core of the Virgo Cluster of galaxies. M84 has a nice system of globular clusters, which is however much less crowded than the system of its giant neighbor 1/2 degree south and 2 degrees east, M87, which may mark the center of the Virgo cluster. As a peculiar feature, M84 contains a central machine which ejects two small but conspicuous jets, which can be seen in the radio light. This object was also target of a 1997 investigation of M84 by the Hubble Space Telescope it was found that the nucleus of M84 contains a massive central object of 300 million solar masses, concentrated in less than 26 light years from the galaxy's center.

Lenticular (S0) Galaxy M85 (NGC 4382), type S0, in Coma Berenices

M85 is the northernmost member of the Virgo Cluster in Messier's catalog, and thus situated in constellation Coma Berenices. It is a luminous lenticular (S0) galaxy; in many respects it seems to be a twin of M84. It seems to consist of an old yellow stellar population only. The luminous disk of this galaxy has a linear diameter of about 125,000 light years.

Lenticular (S0) Galaxy M86 (NGC 4406), type S0, in Virgo

This bright giant galaxy is either an elliptical or lenticular galaxy. Modern classifications apparently tend more to the lenticular classification. It has a conspicuous system of faint globular clusters. However, this system of globulars is far less populated than that of its giant neighbor to the SE, M87. M86 lies well in the heart of the Virgo Cluster of galaxies and forms a most conspicuous group with another giant, M84. M86 is the galaxy which has the fastest approaching velocity, and thus the highest blue shift, of all Messier galaxies (and thus all Messier objects): It is approaching us at 419 km/sec! Holmberg has therefore speculated that it should be a close foreground galaxy and not a Virgo cluster member. However, the present author thinks it is just this high approach velocity which indicates that M86 is most probably a true cluster member, because of the following reason: In this case, the high velocity value would indicate that M86 is moving at a peculiar velocity of more than 1500 km/sec, which points by chance in a direction toward us. But this is not totally uncommon in huge clusters of galaxies as the Virgo cluster, because due to its enormous mass, this huge agglomeration of mass has a strong gravitational field. This strong gravitational field could easily accelerate a galaxy to the high velocity observed for M86; it would be much more difficult to find an explanation for such a high velocity for a field galaxy

Elliptical Galaxy M87 (NGC 4486), type E1, in Virgo

The giant elliptical galaxy M87 is one of the most remarkable objects in the sky. It is perhaps the dominant galaxy in the closest big cluster to lying about 60 million light-years away. M87's diameter is about 120,000 light years. M87 contains much more stars (and mass) than our galaxy, certainly several trillion (10^12) solar masses. It is also of extreme luminosity, with an absolute magnitude of about -22. M87 is famous for two peculiar and perhaps unique features, a huge globular cluster system found on long exposures, and a spectacular jet which is better seen on short exposure photographs. This magnificient galaxy is perhaps the one with most known globular clusters. While our Milky Way has the modest number of roughly 150 to 200 globulars, M87 possesses a remarkable system of several thousands of these objects: Moderate estimates give numbers of at least 4,000, while more modern values go up to 15,000. The luminosity function of globular clusters (which describes the percentage of globulars in certain luminosity intervals) was used repeatedly in the past to estimate the distance of M87. They estimated a distance of roughly 55 million light years, in very good accordance with the 56 million light years obtained for M100 by Cepheid observations.

Spiral Galaxy M88 (NGC 4501), type Sc, in Coma Berenices

This bright member of the Virgo Cluster of galaxies is nicely symmetrical and of multiple-arm type. As its equatorial plane is inclined by about 30 degrees to the line of sight, and its outline is an elongated ellipse of angular dimension, corresponding to a linear diameter of about 130,000 light years. This is one of the more rewarding galaxies in the Virgo cluster for smaller instruments! This galaxy is one of the Virgo cluster members with a considerable peculiar velocity away from us, as it is receding with about 2000 km/sec.

Elliptical Galaxy M89 (NGC 4552), type E0, in Virgo

M89 is another member of the Virgo cluster of galaxies, and apparently one of Messier's own discoveries. It is of elliptical type and nearly exactly circular, and it appears to be smoothly textured. M89 was the first enveloped galaxy discovered, the envelope being extended to more than 150,000 light years from the galaxy. Moreover, a jet-like structure seems to extend to over 100,000 light years distance.

M90 is one of the larger spirals in the Virgo Cluster of Galaxies. It has tightly wounded, smooth bright spiral arms, which appear to be completely "fossil", meaning that currently no star formation appears to take place, with the only exception of the inner disk region, near the darker dust lanes. As it is approaching us at 383 km/sec, it must have the very high peculiar velocity of nearly 1500 km/sec through the Virgo cluster into the direction pointing to us, and possibly is just in process of escaping the cluster.

Spiral Galaxy M91 (NGC 4548), type SBb, in Coma Berenices

For a long time, M91 was a missing Messier object, as Messier had determined its position from M89 while he thought it was from M58, as the Texas amateur W.C. Williams has figured out in 1969. The barred spiral galaxy M91 is an appealing member of the Virgo Cluster of galaxies. Suggestions of this bar may be seen at medium power even in smaller telescopes, if the viewing conditions are good enough to see the galaxy at all. As its recession velocity is only about 400 km/sec, it has a considerable peculiar velocity toward us through the Virgo cluster, about 700 km/sec, as the cluster's recession velocity is about 1100 km/sec.

Globular Cluster M92 (NGC 6341), class IV, in Hercules

According to newer sources, M92 is about 26,000 light years distant. A semi-recent estimate of M92's age has given a value of about 16 billion years. M92 is a splendid object, visible to the naked eye under very good conditions and a showpiece for all optics. It is only slightly less bright but about 1/3 less extended than M13: its 11.2' angular extension corresponds to a true diameter of 85 light years, and may have a mass of up to 330,000 suns. M92 is approaching us at 112 km/sec.

Open Cluster M93 (NGC 2447), type 'g', in Puppis

M93 is one of the smaller but bright open clusters, the stars forming a triangular shape. At least about 80 members appear scattered over its 22' apparent diameter, which is of the order of 20-25 light years linearly at its distance of about 3,600 light years. The brightest stars of M93 are blue giants, its age has been estimated as roughly 100 million years.

Spiral Galaxy M94 (NGC 4736), type Sb, in Canes Venatici

Spiral galaxy M94 was classified Sab because of its extremely bright inner region. This bright circular disk is surrounded by a ring of active star-forming regions, traced by blue young star clusters in color images, which sharply separates it from a much less bright outer ring of an older yellowish stellar population. In the outskirts, this region however ends again in a ring with moderate star formation activity, so that M94 is one of the relatively rare galaxies in which two "waves" of stellar formation can be observed. The distance of M94 is not yet well-determined but estimated at 14 million light years.

Spiral Galaxy M95 (NGC 3351), type SBb, in Leo

M95 was one of the galaxies in the key project of the Hubble Space Telescope for the determination of the Hubble constant: the HST was employed to look for Cepheid variables

Spiral Galaxy M96 (NGC 3368), type Sa, in Leo

M96 is the brightest member of the Leo I group of galaxies, which is therefore also called the M96 group. Its distance was determined to be about 41 million light years. At this distance, the apparent diameter of its brighter central region, 6 arc minutes, corresponds to a linear dimension of 66,000 light years. According to J.D. Wray's Color Atlas of Galaxies, the bright inner disk is composed of a smooth yellow stellar population of old stars, which ends slightly beyond a ring of blue knots. These knots are probably clusters of young, hot stars. A bright supernova, SN 1998bu, was discovered by Mirko Villi on May 9, 1998 at 13th magnitude and was quickly brightening to 11.8 mag.

Planetary Nebula M97 (NGC 3587), type 3a, in Ursa Major

Owl Nebula The Owl Nebula M97 is one of the fainter objects in Messier's catalog, discovered by Pierre Mechain. Its appearance has been interpreted as that of a cylindrical torus shell, so that the projected matter-poor ends of the cylinder correspond to the owl's eyes. This shell is enveloped by a fainter nebula of lower ionization. The mass of the nebula has been estimated to amount 0.15 solar masses, while the 16 mag central star is believed to be of about 0.7 solar masses. Its dynamical age is about 6,000 years.

Spiral Galaxy M98 (NGC 4192), type Sb, in Coma Berenices

M98 is one of the more difficultly observable galaxies in the Virgo Cluster, although it is situated in constellation Coma. It is approaching us, at 125 km/sec. However, in the opinion of the present author, this is one of the strongest arguments that M98 is actually a Virgo member! M98 is nearly edge-on and displays a chaotic, diffuse disk, containing some blue regions of newly formed stars, and a huge quantity of occulting dust, which reddens considerably the light of the central small but bright nucleus.

Spiral Galaxy M99 (NGC 4254), type Sc, in Coma Berenices

M99, although situated in constellation Coma Berenices, is one of the bright spiral members of the Virgo Cluster of galaxies. It rotates clockwise (unlike the nearby spiral M100), and is unusually asymmetric. Its recession velocity is quite high for a Virgo Cluster member: 2324 km/sec according to the Sky Catalog 2000.0, the highest recession velocity measured for a Messier galaxy. This means that it is moving through the Virgo Cluster with a high proper (or peculiar) velocity of at least about 1200 km/sec, by chance in a direction pointing away from us. Taking into account that the relatively nearby (in the sky) galaxy M98 is approaching us at 125 km/sec, and thus moving at about the same peculiar velocity but, by chance, toward us, one may speculate that these two galaxies might have been involved in an encounter, but this is currently not much more than wild speculation.

The galaxy M100 is one of the brightest members of the Virgo Cluster of galaxies. The galaxy is in the spring constellation M100 is spiral shaped, like our Milky Way, and tilted nearly face-on as seen from earth. The galaxy has two prominent arms of bright blue stars and several fainter arms. The blue stars in the arms are young hot and massive stars, which formed recently from density perturbations caused by interactions with neighboring galaxies which are lying just outside our image. M100 has been imaged extensively by the Hubble Space Telescope, which finally led to the discovery of over 20 Cepheids and a distance determination of 56+/-6 million light years for M100, the first considerably reliable distance determination of a Virgo cluster galaxy. Amateurs can see the central regions of this galaxy as faint elliptical patch of uneven texture in small telescopes, or even in good binoculars. Under good observing conditions, suggestions of the inner spiral arms can be glimpsed in telescopes starting at 4 inch aperture (refractor or unobstructed reflector.

Spiral Galaxy M101 (NGC 5457), type Sc, in Ursa Major

The central region of this galaxy is visible in smaller telescopes, best at low powers. Suggestions of the spiral arms can be glimpsed in telescopes starting from 4 inch as nebulous patches. On photographs, however, the Pinwheel Galaxy M101 is revealed as one of the most prominent Grand Design spirals in the sky. While quite symmetric visually and in very short exposures, which show only the central region, it is of remarkable unsymmetry, its core being considerably displaced from the center of the disk. The distance of M101 has been determined 24 +/- 2 million light years . It has a linear diameter of over 170,000 light years and is thus among the biggest disk galaxies.

Evidently, M102 is the last possibly `missing', or doubty, Messier object. This means that two opinions on the identity of this object are common: M 102 may be a duplication of the Spiral Galaxy (NGC 5457) in Ursa Major, due to either an error with the catalog author, Messier, or its 'discoverer" Mechain.  In addition, M 102 may be the Lenticular Galaxy NGC 5866 in Draco, also sometimes called the Spindle Galaxy as Messier's catalog description indicates, together with the position he added later by hand.

Open Cluster M103 (NGC 581), type 'd', in Cassiopea

M103 is one of the "latest additions" (together with M101 and 102) which Messier included from Mechain's report, but had not the time to observe before publication. This cluster of at least 40 proven members is one of the more remote open clusters in Messier's catalog, at about 8,000 light years. 25 million years for M103. M103 is approaching us at 37 km/sec.

Spiral Galaxy M104 (NGC 4594), type Sa, in Virgo

M104 is numerically the first object of the catalog, which was not included in Messier's originally published catalog. However, Messier added it by hand in his personal copy on 11th May 1781 as a "very faint nebula." This brilliant galaxy was named the Sombrero Galaxy because of its appearance. It also has an unusually pronounced bulge with an extended and richly populated globular cluster system - several hundred can be counted in long exposures from big telescopes.

Elliptical Galaxy M105 (NGC 3379), type E1, in Leo

M105 is the brightest elliptical galaxy in the Leo I or M96 group of galaxies, and as such approximately 38 million light years distant. Investigations with the Hubble Space Telescope of the central region of M105 have revealed that this galaxy contains a massive central object of about 50 million solar masses.

Spiral Galaxy M106 (NGC 4258), type Sbp, in Canes Venaciti

The bright spiral galaxy M106 is perhaps about 21 to 25 million light years distant. It is receding at 537 km/sec. M106 is usually classified as peculiar "normal" spiral. As its equatorial plane is similarly inclined to the line of sight, many features resemble what we know from the Andromeda galaxy M31. In 1995, investigations with the Very Large Baseline Array radio telescope equipment gave evidence that M106 is possibly the home of a massive dark objects, which could be traced to the lowest distance from the center ever possible up to now: 36 million solar masses apparently reside within a volume of about 1/24 to 1/12 light year radius (27,000 to 54,000 AU). This was then the densest matter concentration ever detected.

Globular Cluster M107 (NGC 6171), class X, in Ophiuchus

M107 is another additional object found by Pierre Mechain in April, 1782. Herewith, it is probably the Messier object, which was the latest to be discovered. M107 apparently contains some dark obscured regions, which is unusual for globular clusters. The star distribution is called "very open" by Kenneth Glyn Jones, who points out that this cluster "enables the interstellar regions to be examined more easily, and globular clusters are important `laboratories' in which to study the process by which galaxies evolve." As its distance is about 20,000 light years, this corresponds to roughly 60 light years. M107 is approaching us at 147 km/sec, contains about 25 known variables, and as a globular cluster, is of intermediate metalicity.

Spiral Galaxy M108 (NGC 3556), type Sc, in Ursa Major

M108, together with M109 was probably discovered by Pierre Mechain in the same night when he found M97 (February 16, 1781. The object M108 was finally added to Messier's catalog by Owen Gingerich in 1953. The nearly edge-on galaxy M108 appears to have no bulge and no pronounced core at all, it is just a detail-rich mottled disk with heavy obscuration along the major axis. There's little evidence for a well-defined spiral pattern in this Sc galaxy, which is receding at 772 km/sec. According to Brent Tully, it is about 45 million light years distant, and a member of the Ursa Major cloud, a loose agglomeration of galaxies. M108 is quite easy for the amateur, easier than the published values of its brightness imply. It’s described as a "silver-white beauty, saucer-shaped and very well defined" with a quite bright and irregular central region, surrounded by "light and dark nodules. It is actually surprising how much detail can be seen in this galaxy with small instruments!

Spiral Galaxy M109 (NGC 3992), type SBc, in Ursa Major

M109 is one of the "Theta"-like barred spirals, which appears as a "hazy spot" situated just 40' SE of the mag 2.44 star Gamma Ursae Majoris (Phad, or Phecda). It was observed by Pierre Mechain on February 16, 1781. M109 appears pear-shaped in smaller telescopes, "with a strong suspicion of a granular texture". According to Brent Tully's Nearby Galaxies Catalog, M109 is about 55 million light years distant, as it is receding at 1142 km/sec, and a member of the Ursa Major Cloud, a giant but loose agglomeration of galaxies.

Elliptical Galaxy M110 (NGC 205), type E6p, in Andromeda

A Satellite of the Andromeda Galaxy, M31

M110 is the second brighter satellite galaxy of the Andromeda galaxy M31, together with M32, and thus a member of the Local Group. Curiously, this galaxy was discovered by Charles Messier on August 10, 1773, and depicted on his fine drawing of the "Great Andromeda Nebula" and its companions published in 1807, but Messier did never himself include this object in his catalog, due to unknown reasons, perhaps due to sloppiness in recording. It was the last additional object, added finally by Kenneth Glyn Jones in 1966. The small elliptical galaxy M110 is at about the same distance as the Andromeda galaxy M31, about 2.9 million light years. It is of type E5 or E6 and is designated "peculiar" because it shows some unusual dark structure (probably dust clouds); it is now often classified as a dwarf spheroid galaxy, not a generic elliptical one (this would make it the first ever known dwarf spheroid, of course). Its mass was estimated to be between 3.6 and 15 billion solar masses. Apparently, despite its comparatively small size, this dwarf elliptical galaxy has also a remarkable system of 8 globular clusters in a halo around it.