- 2817 - STARS - residing in your neighborhood? - I am certain you have not thought about it. But, how well do you know the stars in your neighborhood? Not those stars! I mean, the stars like our Sun. The Sun is obviously the closest star, but, what would you see if you looked 15 lightyears in all directions? The closest star is 4 lightyears away. What about the rest?
--------------- 2817 - STARS - residing in your neighborhood?
- If you look out 15 lightyears you include the next planetary system we know that is similar to our Solar System. At least, what we have discovered at the time. Inside that sphere that is 30 lightyears diameter we have found 59 stars, so far.
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- Only 29 of these stars are single stars like our Sun. The rest all have companions. 18 stars are binaries, or double stars. 12 are triples, 3 stars orbiting around each other. So, 30 out of 59 stars in our neighborhood are in star systems.
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- That is 50% of stars have companions which seems to be consistent with all the stars that are out there. The nearest star to us is a 3 star system. The nearest 4 star system is 19 lightyears away and outside the neighborhood.
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- The volume of this sphere of space means the neighborhood of 42 star systems have 14,000 cubic lightyears to roam around in. Each star system has 336 cubic lightyears for a big yard to play around in. There is not much likelihood of them running into each other.
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- Stars are identified by their color. The color also tells us their surface temperature. White is hot, and the star “Sirius” is a white star at 8,700 Kelvin that is 8.6 lightyears away. Sirius is 22 times brighter than our Sun.
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- Another star nearby is “Procyon which is a yellow-white star, 6,700 Kelvin. Procyon is 11.4 lightyears away. These two are the big boys in the neighborhood.
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- Our Sun is a yellow star with a surface temperature of 5,600 Kelvin. There are 2 more yellow stars in the neighborhood. Alpha Centauri has on and Tau Ceti at 11.9 lightyears away has the other. Alpha Centauri is the 3 star system that is closest at only 4.2 lightyears away.
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- 38 of the stars are “red stars“, 3,100 Kelvin on average, with a range of temperature from 2,200 to 3,900 Kelvin. These stars are mostly Red-Dwarfs at 1/2 the size of our Sun. None of them are visible with the naked eye. Proxima Centauri, the third star in Alpha Centauri triple is one of them and our closest star.
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- Stars cooler than 1,200 Kelvin are infrared and are called Brown Dwarfs. There are 2 in our neighborhood that are 11.8 lightyears away, but, there may be more. They are very dim and hard to find.
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- Dead stars are White Dwarfs, the collapsed core of a planetary nebulae. Our Sun will become one of these stars in another 5 billion years when all its hydrogen fuel runs out.
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- White Dwarfs are the cinders left behind after the star collapses. They have no fusion and simply cool off as a hot rock. 2 of these White Dwarfs are in our neighborhood. Both are companion stars. One is orbiting Sirius and the other is orbiting Procyon.
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- There are 5 other stars found in our neighborhood but we have not learned enough about them to classify them.
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- The Milky Way is 120,000 lightyears across, so the 30 lightyears across our neighborhood is a small piece of the galaxy.
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- A review to follow will try to describe the whole galaxy that contains 200,000,000,000 stars and at least a trillion planets, including Earth.
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- September 8, 2020 1113 2817
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--------------------- --- September 9, 2020 --------------------------------------
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