MadSci Network: Astronomy
Query:

Re: Are 3D Universe Chart objects time-direction vector corrected?

Date: Fri Jul 9 16:20:51 2004
Posted By: Joseph Lazio, Radio Astronomer
Area of science: Astronomy
ID: 1089257243.As
Message:

Perhaps the best to answer this question is to quote from Section G of the sci.astro FAQ:

Subject: G.12 Do star maps (or galaxy maps) correct for the motions of the stars?

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 billion kilometers (or 3E11 km). Suppose the star is 100 light years (about 1E15 km or 1 quadrillion kilometers) distant. Thus, in 1000 yrs, the star moves about 0.03% 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.


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