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How many stars are in the Universe?
----------------- #1228 - How Many Stars are in the Universe?
- Press Democrat 12-2-10 AP has an estimate of the number of stars in the Universe. Thinking all galaxies were similar to our Milky Way they undercounted the number of Red Dwarf stars. The new number is 3 times larger. Our Milky Way Galaxy is unique. Here is how:
- Attachments - Milky Way.
- The newspaper article estimate for the number of stars in the Universe is 3 *10^23. To take away the exponent, the number is 300,000,000,000,000,000,000,000,000 stars.
I did not even know the AP was counting. I thought Wikileaks would release the data.
But, there you have it. The earlier estimate was 1*10^23 now it is 3 times larger. Why?
Astronomers have discovered that all galaxies are not like our Milky Way in star density.
- Red Dwarf stars are the most common stars because they live the longest. Our Sun is yellow - green and it lives for about 10,000,000,000 years. Red Dwarf stars are red because they burn at a lower energy because they have 20% the mass of the Sun. Burning slower allows them to live much longer. Really big stars live very short lives.
- Astronomers were using the same estimate for Red Dwarf stars in all the galaxies. However, recent discoveries are that Elliptical Galaxies have more Red Dwarf stars than Spiral Galaxies, like our Milky Way Spiral Galaxy. 30% of the galaxies are Ellipticals and they have up to 20 times more Red Dwarf stars.
- The longer stars have been around the more of the heavier elements they contain. Supernovae explosions create the heavier elements blowing the heavy elements into the interstellar medium. The next generation stars to follow form from this medium and contain these heavier elements. The more generations that were previous the more of the heavier elements they contain.
- In 2005 a halo star was discovered in the Constellation Libra the Scales that contained only 0.1% the amount of iron that the Sun contains. This meant that the star was one of the 1st generations of stars probably only enriched by a single supernova generation ahead of it.
- This one supernova had exploded spreading some of the heaviest elements, radioactive thorium and uranium. These heavy elements have unique radioactive decay rates. By comparing the abundance in the star today astronomers could calculate the star with 0.1% iron to be 13,200,000,000 years old.
- The Universe is 13,700,000,000 years old so this 2nd generation star must have formed when the Universe was only 500,000,000 years old. Stars must have started forming very soon after the Big Bang.
- Our Sun is 4,600,000,000 years old so it must have formed when the Universe was ˝ as old as it is today.
- Our Sun is one of over 100,000,000,000 stars that are gravitationally held together by the Milky Way Galaxy. It is a starry disk 120,000 lightyears across. It is encircled by another disk of hydrogen gas seen only by radio telescopes. It encircled again by an enormous halo of Dark Matter that has 5 times more mass than the starry disk. The disk we can see is 2,000,000,000,000 Solar Mass.
- There are dozens of lesser galaxies orbiting our Milky Way like moons orbiting a giant planet. Our Milky Way contains a rich supply of the heavy elements allowing terrestrial planets like ours to form. At least one even formed with life. This planet formed with the oxygen we breath, the iron in our blood, and the calcium in our bones. All these heavier elements were originally formed from the interstellar medium polluted by previous generations of exploding supernovae. Our Galaxy’s immense gravity has slowed the escape speed of exploding star debris and colleted enriched gas and dust clouds from which the Sun and Earth were formed.
- Central to our Galaxy’s immense gravity about which all the stars revolve is a Blackhole, named “Sagittarius A”. It is 27,000 lightyears away and we orbit it every 230,000,000 years. The mass of this Blackhole is 4,000,000 Solar Mass.
- In 2004 astronomers saw an X-Ray echo bubble 350 light years away from Sagittarius A indicating that a planet-size mass had fallen into the Blackhole 350 years ago.
- In 2005 astronomers found other stars that had been thrown out of their Blackhole orbits at tremendous speeds. The hypervelocity star was 200,000 lightyears away traveling at 1,600,000 miles per hour. Since then astronomers have found 15 more of these hypervelocity stars thrown out by Sagittarius A.
- How do these stars get ejected rather than being eaten by the gravity of the Blackhole?
- In 1998 Jack Hill of Los Alamos Labs predicted that if a binary star approaches a Blackhole too closely and one of the stars was sucked in by the enormous gravity, the Conservation of Energy would dictate that the other star would be thrown out with an equal and opposite amount of energy. These companion stars are flying away at such high velocities that some will escape the gravity pull of the Milky Way altogether and go flying into interstellar space.
- Over 100,000 stars orbit Sagittarius A at less that 1 lightyear distance. Some complete their orbits in only a few years. Maybe we will see another X-Ray echo or a hypervelocity star sent our way in the near future. Our Galaxy’s Blackhole while still active is considered very mild by galactic standards. We have found a near perfect galactic environment in which to live. How lucky can you get?
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707-536-3272, [email protected] Thursday, December 2, 2010
