Ronn!Blankenship wrote: > > I'm not sure about _accelerations_, > That's the problem, isn't it? But maybe if we don't expect any two stars to get close enough,
Well, let's see: the distance from the Sun to alpha Centauri is about 30,000,000 solar diameters or 60,000,000 solar radii, so what is the attraction between the two stars?
An illustration I have heard (not necessarily precise) is that two stars in our Galaxy have about the same chance of colliding as two flies which start from opposite ends of the Grand Canyon.
they will just follow some 200 or so million year orbit around the Galaxy, which will reduce to an almost straight line in anything of the order of 10 million years.
That is clearly what the author of the S&T article (below) did. 10my/225my = 0.28 radians or 16�, a little large for using the small angle formulas (although technically the angle is only +/- 8� from the present position). I suppose one might try approximating the path as an arc of a circle rather than a straight line, though the particular curve fit one used might be as likely to make it less accurate as more accurate than the straight-line approximation.
> but the Hipparcos/Tycho catalog has the > best currently available information on the motions of > the stars it lists > Ok
> There was an article in _Sky and > Telescope_ within the past few years in which that data was used to > determine which star was the apparently brightest star as seen from Earth > at any given time during the interval 5 mybp to 5 myap.
I believe this is the article:
Computers in Astronomy � Once and Future Celestial Kings By Jocelyn Tomkin | April 1998, p. 59-63 (PDF: 255 kilobytes)
To purchase a copy of the article in PDF format for $2.95US, go to: <<http://skyandtelescope.com/shopatsky/_additem.asp?aaid=199804059063>>
Also, here's an item about a red dwarf which will come within 1 ly of the Sun about a million years from now:
<<http://antwrp.gsfc.nasa.gov/apod/ap970626.html>>
m = 1/1000. Do you mean My or ky?
"mybp" is frequently used by geologists as an abbreviation for "million years before present."
(Frex, Alberio >will be the brightest star in the sky about 4.5 my from now.)
> Does this sound like what you need? > Yep - ** if ** they explicitly give an error
> If so, are you familiar with the Hip/Tyc catalog > and its data format, or do you need more information? > No; but I guess I can find it quickly with a google search. It's free, isn't it? Probably some Megabytes of data
Home page: <<http://astro.estec.esa.nl/SA-general/Projects/Hipparcos/hipparcos.html>>
I've been using the Gliese3 catalog for some time
Unless they've updated it with Hipparcos data, the parallax/proper motion data is out of date.
-- Ronn! :)
Ronn Blankenship Instructor of Astronomy/Planetary Science University of Montevallo Montevallo, AL
Disclaimer: Unless specifically stated otherwise, any opinions contained herein are the personal opinions of the author and do not represent the official position of the University of Montevallo.
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