How Do They Know How Far It Is?
By armie1013
@armie1013 (23)
Philippines
May 31, 2010 10:09pm CST
When astronomers tell us that Andromeda galaxy is two million light-years away, they are really giving us an educated guess. No one has come up with a way to measure such mind-boggling distance directly. The famous red supergiant Betelgeuse in Orion, are subject to guesswork, with estimated distances for it ranging from 300 light-years to over 1,000. But how those astronomers determined how far it is?
1 response
@qianyun6 (2067)
• China
1 Jun 10
There are many ways to measure it. One simple way I know is:
measure the angle position a1 of the galaxy in celestial sphere one day, and another angle position a2 half a year later. Because the earth is in the opposite side of obrit, a triangle has been made. Suppose that the galaxy moves little, you can simplely estimate the distance by geometric calculation.
