Like our Sun, when a star comes to age after burning away all the hydrogen to helium during its main sequence phase, then helium to carbon and oxygen, its nuclear reactions come to an end in its core, while helium burning goes on in a shell. The outer layers pulsate as the star expands and the star loses mass in strong stellar winds. A large amount of the stars mass is ejected leaving the stellar core, which is as an extremely hot, small central star, emitting high energy radiation. The emitted radiation causes the expanding shell to glow, which becomes visible as a planetary nebula.
Charles Messier discovered the first planetary nebula, The Dumbbell Nebula M27, on July 12, 1764. William Herschel called these objects "Planetary Nebula" when he classified them in 1784 after his discovery of Uranus. Our Sun might evolve to this state in a few billion years. The lifespan of a planetary nebulae is short when compared to stellar time scales. A typical planetary nebulae is visible for a few thousand or tens of thousands of years and then fades out.
The central star cools down to a white dwarf. Although there are billions of sun-like stars among the hundreds of billions in our Milky Way galaxy, there are only about 10,000 planetary nebula
The cooling process of the white dwarf goes on until all thermal energy is radiated. At that point the star becomes a black dwarf as it approaches a final stable end state. It is believed that the universe is probably still much too young to contain any "cooled-out" black dwarf.
The Virgo Cluster of Galaxies
Also: Coma-Virgo cluster of Galaxies
The Virgo Cluster is a
combination of many galaxies and is the largest structure in our intergalactic
neighborhood. This structure is
another discovery by Charles Messier, who noted behind his entry for M91, "The constellation Virgo and
especially the northern wing is one of the constellations which encloses the
most nebulae. This catalogue contains 13, which have been determined viz.
Nos. 49, 58, 59, 60, 61, 84, 85, 86, 87, 88, 89, 90, and 91. All these
nebulae appear to be without stars and can be seen only in a good sky and near
meridian passage. Most of these nebulae have been pointed out to me by Mechain".
Messier galaxies which are Virgo cluster members: M49, M58, M59, M60, M61,
M84, M85, M86, M87, M88, M89, M90, M91, M98, M99, and M100.
The Virgo Cluster has about 2000 member galaxies and represents the physical center of our Local Supercluster (also called Virgo or Coma-Virgo Supercluster), and influences all the galaxies and galaxy groups by the gravitational attraction of its enormous mass. It has slowed down the escape velocities (due to cosmic expansion, the `Hubble effect') of all the galaxies and galaxy groups around it, thus causing an effective matter flow towards itself. Eventually many of these galaxies have fallen, or will fall in the future, into this giant cluster, which will increase in size due to this effect. Our Local Group is speeding toward the Virgo cluster.
The Magnitude System
Magnitude Example Comments
-12 Full Moon
-5 Venus Brightest Star like object. Can cast shadows.
-1.5 Sirius Brightest Star.
0 Vega Only 8 stars are this bright or brighter.
1 Antares Twenty stars are this bright.
2 Polaris Medium bright: 60 stars.
3 Dull medium: 150 stars.
6 Borderline visible: 6,000 stars.
9 Binocular limit: 50,000 Stars.
12 Barely visible through small telescope; 60,000 times fainter than Vega.
20 Visual limit of Hale telescope, 100 million times fainter than Vega.
25 Faintest Hale telescope stars using electronic amplification
29 Detection limit of Hubble Space telescope; 250 Billion times fainter than Vega!!
The system is set up so that a 5-magnitude change corresponds to a hundred-fold shift in brightness.
Betelgeuse – Translated literally it means "The armpit of the sheep"? How big is Betelgeuse? Monstrous! If you could imagine this leviathan as a globe big enough to encapsulate a building twenty-stories high – consider this for a moment – then on the same scale our planet, Earth, would be the period at the end of this sentence. If that star were an empty jelly jar and we could unscrew its lid to pour in balls the size of our planet at the rate of a hundred a second, it would take 30,000 years to fill Betelgeuse.
Under normal circumstances it's gigantic! It's volume is almost 200 million times bigger than the sun. Bursts of energy at its core balloons its surface outward until it becomes a billion miles wide! So huge that if it sat in our solar system where the sun sits it would eat Mercury, Venus, Earth, Mars and Jupiter! A star that giant can't sustain its size. Eventually its central furnace loses the battle against the force of gravity, which forces the surface to collapse. This process continues until it shrinks to a point where so much heat is generated that the surface begins to expand and start the process all over.
Betelgeuse displays an irregular fourteen-month period when its brightness rises and falls greatly like a cosmic tide. At its crest it can become heavens sixth brightest, while its average brilliance still places it respectably in eleventh place. Ordinary red stars are so faint that we can’t see them at all, not one example, with the naked eye. Therefore if we do notice a reddish star – and there are dozens whose ruddy tint is obvious to the naked eye- we can conclude that it’s a giant. Only a star with a huge radiating surface can compensate for its dimness per square foot.
Even though Betelgeuse is over 500 light-years distant, it is so monstrous that it can be directly detected using telescopic interferometry. Betelgeuse is so huge that it looks like a disk through the Hubble Space Telescope. This is incredible when you realize that alll other stars remain points of light no matter what magnification is used. But it should be remembered that resolving even this largest of all stars stretches modern technology to its limits: The globe of Betelgeuse appears the size of a basketball seen from 800 miles away.
The tenuous shell of material discovered in 1978 that encases the star like a cocoon. It is made of potassium. This immense globe extends eleven thousand times farther from Betelgeuse than we ourselves sit from our sun. It is nearly three hundred times the diameter of our entire solar system out to the orbit of Pluto. To construct a scale model of this potassium shell would require it to be a ball three hundred times the height of the Empire State Building, a globe so high that it would extend nearly to outer space and cover the area from New York to Philadelphia. Only then could our Earth be placed alongside it for comparison – once again merely the size of the period ending this sentence.
Rigel (RYE-j’l) – is a super giant. But with Rigel the astonishing characteristic is brightness rather than size. Rigel is quite possibly the most luminous star the unaided eye can behold. A blue-white arc welder in winter’s icy night, it shines with the same light as fifty-eight thousand suns, nearly twice as far as Betelgeuse, it still outshines all but five of the nights stars. Four of these – Sirius, Alpha Centauri, Arcturus, and Capella – are all nearer than 50 light years, yet Rigel gives them competition from a perch almost 1,000 light years farther away, so remote that it sits on the next spiral arm of the Galaxy! If Rigel were, as close to us as the others, our nocturnal landscape would tingle with sharp, alien Rigel shadows, and the night sky would always be as bright as when a full moon is out. Most of the universe would disappear from view.
Betelgeuse, condemned to an early passing, has a further lifetime of less than a quarter-billion years, 5% of the time until our own sun’s retirement.
Still that’s long enough – more than ample to enjoy it every winter of our lives, and to reveal to our children and grandchildren the topaz flame in Orion’s shoulder that is the largest single thing they will ever see!
Want to take a vacation to outer space? You’d better pack some good "age reducing" skin cream and plenty of vitamins.
Let’s start by taking a walk around the Solar system. If we decided to start jogging at 5 miles an hour and traveled in a straight line to the moon, which is 238,000 miles away would take 47,000 hours, 1,983 days, or 5.43 years to get there. Of course, that’s assuming you ran 24 hours a day, 365 days a year! To arrive to the closest planet Venus, which is 25 million miles away it would take 593 years. Mars? Its only 50 million miles away, which means we’d need a couple extra changes of tennis shoes and 1117 years of travel. Jupiter, which is 391 million miles away, would take 8,920 years. It would take a couple extra shakes to make the trip. Pluto, which sits at the outskirts of our tiny solar system is about 3.6 billion miles away; that’s 3.6 with 9 zeros. It would take about 81,500 years to make the trek.
How about if we took the space shuttle? Could we get to Pluto in an hour or so traveling at 18,600 miles an hour? Let’s see. If you traveled in a straight line to the moon, which is about 238,800 miles away, you’d get there in about 13 ˝ hours.
Venus, which is about 25 million miles, would take about 57 days! Mars, 50 million miles away would take 114 days traveling at 18,000 miles per hour. Jupiter, which is a mere 400 million miles away from us, would only take 2.5 years. Saturn, 795 million miles away, just under 5 years. Uranus, 1 billion, 689 million miles, 10.4 years. Neptune, 2.7 billion miles, 16 ˝ years. Pluto, 3.6 billion miles would only take about 22 years give or take a month.
If we could move at light speed the trip would be a little more manageable because we’d be traveling at about 186,000 miles per second or about 670 million miles an hour. WOW! At this speed we could get to the moon in 1 ˝ seconds. A 25 million mile trip to venus would take about 138 seconds. A 1.7 billion mile trip to Saturn would take a mere 71 minutes. A trip to the outer reaches of our solar system, to Pluto, 3,573,000,000 miles would only take about 5 1/3 hours. The Alpha Centauri system, which is the second closest star to our planet after the sun is 4.4 light years away or about 25,800,000,000,000 miles or twenty five trillion-eight hundred billion miles. If you could catch a ride on the space shuttle traveling at 18,600 miles per hour, you could make the trip in about 35,975 years.
If you decided to put on the jogging shoes and ran the marathon at a 5 mph pace, 24 hours a day, 365 days a year it would take you 133,828,336.8 years or one hundred-thirty three million, eight hundred twenty eight thousand, three hundred thirty six years. Be sure to pack a toothbrush!!!
Are you Serious or are you "Sirius"
Sirius is the brightest star in the heavens. In fact the only objects that are brighter are Venus and Jupiter. Many civilizations throughout history worshipped Sirius as a god, and acclaimed its rising and setting with monuments, or aligned pyramids or passageways to mark its highest nightly position.
In ancient Egypt, Sirius was revered as a manifestation of Isis. Back in the second millennium B.C., when the constellations were oriented differently from today because of the slow wobble of Earth’s axis, the Dog Star first appeared each year in late June, during the hot weather auspicious by the Egyptians, as it occurred just before the rains upon which their lives depended. Its godly position was further reinforced by the popular belief both there and in ancient Greece that the scorching weather was actually caused by Sirius, the result of an alliance between the Dog Star’s dazzling light and the sun’s rays. Even today we still use the expression dog days to mean sultry weather – though few realize that its origins echo distantly from those vanished centuries.
When viewing Sirius we are actually seeing the combined light of two separate stars. The difficulty is that the companion, Sirius B, is often lost in the dazzling glare of the intensely luminous primary, Sirius A. The two are presently swinging the part of their lopsided orbit where they’re closest together. Although they are generally some 2 billion miles apart.
One of the observational challenges is the extreme disparity in the brightness of the two stars. At first the companion’s remarkable dimness caused bewilderment; with a high surface temperature it should radiate plenty of light. The explanation for the paradox is stunning: Sirius B is a tiny sphere – a star only about the size of Earth, yet with a mass some 350,000 times greater. It is dim because it has 7,000 times less surface area than the sun.
The combination of toy size and large mass means that a white dwarfs material is packed to a density that challenges comprehension. A pail-ful of Sirius B weighs more than 6 million pounds, as much as the thirty-six story Saturn 5 rocket that sent the astronauts to the moon. A cupful weighs as much as two cement trucks. A lollipop of Sirius B would outweigh a car!! It is a white dwarf and is a member of a surprisingly common fraternity of stars. They are almost invisible. They are strange in every way. With gravity 150,000 times greater than the pull one experiences on Earth’s surface, if you weigh 150 pounds here, you’d tip the scales at 22 million on Sirius B. Sirius A is 11,000 times brighter than it’s companion: a floodlight vs. a candle.
A typical white dwarf rotates in just an hour (the sun spins once every 25 days).
Eventually such balls of condensed fire cool enough to assume a solid structure. Indeed, they essentially become single crystals. Since the process takes about 10 billion years, these impenetrable floating jewels will be a common feature only in the old age of the Galaxy.
Over time it will cool, becoming progressively redder and dimmer until a temperature is reached where one could theoretically land on its surface. Unfortunately, that would qualify as a serious lapse of judgment, since the white dwarf’s original high density and overpowering gravitational field would remain. The ship and crew would succumb instantly to this viselike pull. Against such an awesome force one’s motion would freeze like a frame in a hammed projector. Not a single breath co9uld be taken, nor could one lift a finger to warn others. And a beacon pointed upward would have its beam reddened as its light’s waves, struggling against the tug of gravity, stretched out and changed color. Simply put, the light loses energy (red shift) in its upward fight against the star’s gravity. While light’s constant speed is preserved (the light cannot be slowed by the struggle) its waves are robbed of energy and lengthened, and thus appear redder.
Which way is North?
First off, the North Star is not an ordinary star, but a giant! At 600 light years’ distance from us, it lies some six times farther away than the Big Dippers’ "pointer" stars, which guide our eyes to it. In fact, Polaris shines with the same light as sixteen hundred suns.
For a truly snappy spin, you can look beyond the solar system to the tiny collapsed pulsar in the Crab Nebula. There the night’s stars traverse the sky in a dizzying blur every 33rd of a second. The mad streaking of the stars around their north celestial pole would appear to fashion a series of solid concentric rings. Other ultra dense crystalline stars spin so frantically that everything in their sky rises, crosses the heavens, sets, and rises anew hundreds of times each second.
Readers who have small telescopes with lenses or mirrors at least 3 inches in diameter are able to detect a small companion star to Polaris, a wonderful sight. Studies of the light of Polaris indicate a third, unseen star as well, so that the North Star is actually a triplet.
Arcturus is an amazing, unique object, the only celestial body to open a world’s fair. An the only major star that will soon…..disappear! Its pumpkin colored rays emanate from a sphere so large that 25 billion earths could fit inside.
Arcturus is Latin for "guardian of the bear". Arcturus is an immense orange sun. It was the very first star ever seen in broad daylight through a telescope, an event occurring nearly four centuries ago. It is easy to imagine its scorching nuclear intensity, a solitary ruddy ember emitting more than a hundred times the brilliance of our own sun.
The warmth we get from Arcturus is equal to a single candle located five miles away. But that energy was put to good use back in 1933 from the opening of the famous Chicago World’s Fair. Arcturus’ light was focused through a telescope onto a photocell (a newfangled device back then) that tripped the lights to start the festivities. Arcturus was chosen because it was thought to lie 40 light-years away, so that the same light that had left the star forty years earlier – when a previous Chicago fair was closing – would open the new one. It is actually about 36 light years away.
Instead of traveling along together with our galaxy, Arcturus is plunging down at us from 100 million light years away. Just 500,000 light years ago – Arcturus was invisible. It’s been steadily approaching us ever since, and is 1,000 miles nearer since you started reading the page. Skimming though our neighborhood, it’s now almost at it’s closest and brightest point. Then, half a million years from now, before our Earth and sun have revolved even a two-hundredth of the way round the Galaxy’s center, Arcturus will have faded into oblivion forever. So greet it warmly and pay it a salute during the one cycle in time when our paths cross. For we will never meet again.
There are over 10 billion galaxies within view today. M87 is among the largest galaxies known, a gargantuan elliptical blob that will never win a beauty award. Still, it’s the largest ball in the known universe. It consists of several trillion suns, give or take a few, and probably the same number of planets. This means that if you were given the task of counting its stars – not visiting them, or cataloging their characteristics, but merely counting them – and managed to run through ten every second, the assignment would last from the last ice age until the present time.
An enormous black hole sits at the center of M87. Thousands of globular clusters of stars, each with hundreds of thousands of suns, orbit around it. M87 is virtually its own complete cosmos. To any of its possible inhabitants, it would be more than could be explored, ever. The rest of the universe, including our Local Group, would seem utterly irrelevant, thoroughly unnecessary.
Spraying out of M87 is a fiercely violent double jet of material rushing at nearly the speed of light. From this bizarre dual structure comes radiation and energy of such power that it can be loudly heard (with radio telescopes) across the gap of 50 million light-years that safely separates us from it. Its origin may be that colossal black hole hiding in the galaxy’s core.
M87’s central black hole is no mere collapsed star. Its mass has been calculated to equal somewhere between 10 million and 100 million suns.
Where are we going and how fast?
Absolute motion was shown to be an invalid concept a century ago. And since there’s no constant grid in space to tell us where we stand, we are always forced to express our velocity relative to something else.
For starters, the Earth circles the Sun at 18 miles per second. We are also moving with the sun toward the bright star Vega at about 12 miles per second (44,000 miles an hour), so that we never really "complete" an orbit in the sense of returning to where we started. Our path through space is not a loop but a spiral, like an endless bedspring.
Additionally, we’re on an even faster journey around the center of the Galaxy at almost 200 miles per second as some 400 times faster than a rifle bullet. Additionally, our galaxy itself is rushing toward Andromeda at some 50 miles per second.
Are you hungry? Get out the Big Dipper!
Inside the big dipper lie 2 beautiful galaxies M81 and M82. They lie about 10 million light-years beyond the stars of the big dipper. If you could travel fast enough to make 10 round trips between New York to Tokyo in one second, you’d need 10 million years to reach these cities of suns. Yet they are among our closest galactic neighbors, hovering nearer than all but a hundredth of 1 percent of the 10 billion galaxies detectable through today’s telescopes.
The Ursa Major Group lies much further in that same direction. That cluster of galaxies is so remote that the glow of its quadrillion suns, departing just as the last dinosaurs gazed upward, will not reach us for another 700 million years!
The big dippers stars are really neat and fun to learn about. We can name them by using a little bit of visualization. Let’s say you are looking at a frying pan from its side. Let the pan handle face to the left. Now put that pan "dipper" in the sky. The stars would name this way. Look to the top right of the pan. The star is called Dubhe "dubby" and Merak "mee-rack" would be directly below it. These are the famous pointer stars that guide the celestial beginner to the North Star.
Continuing around the big dipper in order, we pass Megrez, the faintest of the seven stars, then we find Phecda at the junction of the bowl and handle, and then the three handle stars: Alioth, Mizar, and Alkaid at the tip. All the dippers names come to us from the Arabic, and the favoritism toward "Al" is because Al means "the" in that language. Alkaid, for instance, translates as "the leader". Aldebaran, Algol, Altair, Alphard, and so on originally meant "the this" or "the that".
The star that is typically seen with Mizar is named Alcor. The "Al" in Alcor means "the abandoned one". The ancient Arabs often tested their sight with this duo, believing the ability to see Alcor indicated keen vision. Indeed, fourteenth century Arabic writings sometimes referred to this star as the Riddle.
Today that title is as appropriate as ever – for a different reason. Either "the abandoned one" has brightened over the centuries or the ancient desert dwellers had vision problems, because Alcor is obvious today even from polluted cities. The riddle is how anyone can fail to see it.
Spectrographic studies have shown that Mizar has a couple of unseen suns circling it as well, making it a five-star system, three of whose members lie too close together for telescopic detection.
In fact, most of the Dipper’s stars are gravitationally linked. Not simply lying in random line-of-sight alignments the way nearly all other constellations are, they’re family members forming a large and unconfined cluster, or association. Of the thousands of such star groups known, the Dipper is the nearest to Earth, which is why it appears so large. The distance to this Big Bear Brotherhood is about 80 light-years; nearby as such things go but still a formidable expanse to travel. Even if the vehicle you were hitchhiking on were the space shuttle, traveling at 18,600 miles per hour, a journey to the Bear would take 2 million years.
Did you know?
not shine due to friction. A meteor moves so fast that the air in front of
it is compressed and heated by a phenomenon called ram pressure, which is the
same thing that warms a hand-held pump when you use it to fill a bike tire.
The heated air, in turn, scorches the meteor. Temperatures can exceed 3,000
degrees Fahrenheit (1,650 Celsius).
Meteors leave behind a trail of ionized gas. Signals from distant FM radio stations or TV stations come in loud and clear as they bounce off this trail, overcoming the Earth’s curvature, clouds and city lights. They can be heard if you tune in to a non-interrupted frequency below 91.1 KHZ. On rare occasions, large meteors have generated loud whistling or buzzing sounds, which “earwitnesses” have detected before visual detection.
Meteors strike the moon, too, and are visible from the Earth. However, the moon has no atmosphere to vaporize the grains, so the tiny bits of comet debris slam into the surface and explode.
During the Apollo Era, seismic recorders were left on the moon. These recorders detected the Leonid strikes in the 1970s. Scientists first confirmed their occurrence with visual observations during the 1999 Leonid meteor shower.
In 2001, three separate stargazers saw one of these lunar Leonids, using telescopes. They observed a brief flash of light equal in brightness to a dim star that would be visible to the naked eye under reasonably dark skies.
How does a
particle slightly larger than a dust particle and weighing only a few ounces
create light, which can be seen from 238,900 miles away? In recent years,
scientists have determined that Leonids travel so fast relative to the Earth and
moon that the impact per unit of mass is 10,000 times greater than dynamite.
Moon dust for a few yards around the impact area is vaporized.
The Leonids are orbiting the sun in the opposite direction as the Earth. They strike Earth’s upper atmosphere at a considerable speed than most meteors at more than 160,000 mph (72 kilometers per second). A typical bullet from a rifle creeps along by comparison at just 2,240 mph (1,000 meters per second). The faintest visible meteors are a mere 0.5 millimeters across, or about the size of a sand grain. The Leonids also create bright fireballs, which are generated by marble sized particles nearly a centimeter in diamter. It creates about 1 million joules of power, or about the same punch as a small car moving at 60 mph.