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2 Questions for Astronomers
Over the years I have heard astronomers repeatedly say two things to
the public so many times that they have become common knowledge. My studies have led me to believe that these are not actually the facts. Can somebody straighten me out ? A) Our sun is just an avergage star. It seems that the vast, vast majority of stars are class M7 at most, probably M2 is even more average. Aren't these stars far enough away from our sun in size and temperature to make the statement "our sun is average" highly inaccurate ? I am quite sure that M class stars are the norm in other galaxies as well. B) The earth will end when the sun burns out, and the orbit of earth will come close to or be enveloped by the edge of the sun, thereby burning it out of existence. The sun will burn out in about 5 to 7 billion years. However, the probablity is extremely high that the Andromeda galaxy will hit our galaxy in about 2 to 3 billion years. Every thing I have seen indicates that this will be a cataclysmic event. How come astronomers dont say "The earth will surely end when the Andromeda galaxy collides with the Milky way in a few billion years, and if that doesn't happen we will have to wait for the sun to burn out in about 6 billion years" I have heard astronomers talk about the Andromeda Milky Way collision, but usually it isn't mentioned when the demise of the earth is the subject. Shouldn't it be the first thing brought up? ----- Sorry, my email has been so destroyed by spam I don't even read it anymore. Please respond here |
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2 Questions for Astronomers
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2 Questions for Astronomers
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2 Questions for Astronomers
In message , BRAINIAC
writes Over the years I have heard astronomers repeatedly say two things to the public so many times that they have become common knowledge. My studies have led me to believe that these are not actually the facts. Can somebody straighten me out ? A) Our sun is just an avergage star. It seems that the vast, vast majority of stars are class M7 at most, probably M2 is even more average. Aren't these stars far enough away from our sun in size and temperature to make the statement "our sun is average" highly inaccurate ? I am quite sure that M class stars are the norm in other galaxies as well. Absolutely. In fact the more recent texts take account of observations of the nearest stars to the Earth and say that our sun is fairly exceptional. B) The earth will end when the sun burns out, and the orbit of earth will come close to or be enveloped by the edge of the sun, thereby burning it out of existence. The sun will burn out in about 5 to 7 billion years. However, the probablity is extremely high that the Andromeda galaxy will hit our galaxy in about 2 to 3 billion years. Every thing I have seen indicates that this will be a cataclysmic event. How come astronomers dont say "The earth will surely end when the Andromeda galaxy collides with the Milky way in a few billion years, and if that doesn't happen we will have to wait for the sun to burn out in about 6 billion years" I really should check this one, but I'm fairly sure that the collision with M31 isn't due for perhaps 10 billion years, well after the sun has become a red giant (assuming we haven't moved the Earth first) Also, it's not certain that the galaxies will collide, as no-one knows M31's transverse velocity. -- "It is written in mathematical language" |
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2 Questions for Astronomers
In message , BRAINIAC
writes Over the years I have heard astronomers repeatedly say two things to the public so many times that they have become common knowledge. My studies have led me to believe that these are not actually the facts. Can somebody straighten me out ? A) Our sun is just an avergage star. It seems that the vast, vast majority of stars are class M7 at most, probably M2 is even more average. Aren't these stars far enough away from our sun in size and temperature to make the statement "our sun is average" highly inaccurate ? I am quite sure that M class stars are the norm in other galaxies as well. Absolutely. In fact the more recent texts take account of observations of the nearest stars to the Earth and say that our sun is fairly exceptional. B) The earth will end when the sun burns out, and the orbit of earth will come close to or be enveloped by the edge of the sun, thereby burning it out of existence. The sun will burn out in about 5 to 7 billion years. However, the probablity is extremely high that the Andromeda galaxy will hit our galaxy in about 2 to 3 billion years. Every thing I have seen indicates that this will be a cataclysmic event. How come astronomers dont say "The earth will surely end when the Andromeda galaxy collides with the Milky way in a few billion years, and if that doesn't happen we will have to wait for the sun to burn out in about 6 billion years" I really should check this one, but I'm fairly sure that the collision with M31 isn't due for perhaps 10 billion years, well after the sun has become a red giant (assuming we haven't moved the Earth first) Also, it's not certain that the galaxies will collide, as no-one knows M31's transverse velocity. -- "It is written in mathematical language" |
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2 Questions for Astronomers
In article ,
Jonathan Silverlight writes: Absolutely. In fact the more recent texts take account of observations of the nearest stars to the Earth and say that our sun is fairly exceptional. Some trivia questions: 1. What's the nearest star that is more luminous than the Sun, and how far away is it? 2. How many stellar systems are nearer than the star in question 1? -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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2 Questions for Astronomers
In article ,
Jonathan Silverlight writes: Absolutely. In fact the more recent texts take account of observations of the nearest stars to the Earth and say that our sun is fairly exceptional. Some trivia questions: 1. What's the nearest star that is more luminous than the Sun, and how far away is it? 2. How many stellar systems are nearer than the star in question 1? -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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2 Questions for Astronomers
In article ,
(Steve Willner) writes: Some trivia questions: 1. What's the nearest star that is more luminous than the Sun, and how far away is it? That one turned out to be more trivial than I expected. As Bill pointed out, alpha Cen A is the answer. Somehow I had the mistaken impression that it is fainter than the Sun, but in fact it's half a magnitude brighter (in V). Bill also pointed out (in private correspondence, quoted by permission) that Sirius (2.64 pc) is the 6th closest star and 4th closest system, and Procyon (3.50 pc) is the 12th closest star. I had a look at the table of 100 nearest stars (not systems) in _Allen's Astrophysical Quantities_ and found two A stars (Sirius and Altair at 5.1 pc), one F star (Procyon), and nine of type G. (I don't promise not to have missed any!) All the rest are of fainter types. The most distant star in the list is at 7.6 pc. The early-type stars seem unexpectedly close to the Sun, but that's probably just statistics of small numbers. In absolute V magnitude, four of the nine G stars are brighter than the Sun, so it's about average for a G star. All in all, it seems fair to say the Sun is rather brighter than an average star but not so bright as to be considered a rare type. Bill also writes: If I remember my Galactic astronomy course, the frequency of G or earlier should be quite a bit less than 12%. Hmmm ... I'm looking at my 2nd edition Mihalas & Binney ... looks like there are about 6000 stars / 10^6 pc^3 brighter than the sun, or one per 170 pc^3. You're counting 12 in a volume of 1840 pc^3, or one per 150 pc^3. That doesn't strike me as too very different. I've learned a few things. Thanks to all who responded, especially Bill. -- Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA (Please email your reply if you want to be sure I see it; include a valid Reply-To address to receive an acknowledgement. Commercial email may be sent to your ISP.) |
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2 Questions for Astronomers
In message , Roger Stokes
writes "BRAINIAC" wrote in message ... A) Our sun is just an avergage star. There are 71 stars within 20 light years of the solar system, of which only 4 (Alpha Centauri A, Sirius, Procyon, and Altair) are brighter than the sun. Most are M dwarfs. Here's the list (from the hipparcos catalog) TYPE DISTANCE (LY) MAGNITUDE Name HIP70890 M5Ve 4.2 +/- 0.00 11.0 Alpha Centauri C (Proxima) HD128621 K1V 4.4 +/- 0.00 1.4 Alpha Centauri B HD128620 G2V 4.4 +/- 0.01 -0.0 Alpha Centauri A (Rigil Kent) HIP87937 sdM4 6.0 +/- 0.04 9.5 Barnard's star Isn't one of the better-known ones missing from that list? Wolf 359 was a TV star about 20 years before it featured in "Star Trek: TNG" (It's the title of an "Outer Limits" story) -- "It is written in mathematical language" |
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