120 Do star maps (or galaxy maps) correct for the motions of the stars?
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This article is from the Astronomy FAQ, by Joseph Lazio (jlazio@patriot.net) with numerous contributions by others.
120 Do star maps (or galaxy maps) correct for the motions of the stars?
By Joseph Lazio <jlazio@patriot.net>
In general, no.
The reason is that stellar distances are so large. Over human time
spans, the typical velocity of a star is so low that its distance does
not change appreciably.
Let's consider a star with a velocity of 10 km/s, typical of most
stars. In 1000 yrs, this star moves about 300 million kilometers.
Suppose the star is 100 light years (about 1E15 km or 1000 trillion
kilometers) distant. Thus, in 1000 yrs, the star moves about 0.00003%
of its distance from the Sun. This is such a small change, it's not
worth worrying about it.
The situation is even more extreme in the case of galaxies. Typical
galaxy velocities might be hundreds to thousands of kilometers per
second. However, their distances are measured in the millions to
billions of light years.e Earth is still generating heat by radioactive
decay in its interior. Some of this heat leaks out through
hydrothermal vents on the floors of the oceans. Thus, the lower
levels of the oceans would remain liquid, and the hydrothermal vents
would remain active. Organisms that depend only on the hydrothermal
vents could survive probably quite happily for several billion years
after the Earth was ejected from the solar system. (Indeed, since the
oceans will probably boil away in the next few billion years as the
Sun's luminosity increases, these organisms might prefer the Earth to
be ejected into interstellar space!)
For additional reading see "The Frozen Earth" by Adams & Laughlin,
<URL:
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999AAS...194.1511A
> and Stevenson, "Life-sustaining planets in interstellar space?",
Nature, v. 400, 1 Jul 1999, p. 32.
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