Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] absolute magnitude

One of the ways of measuring distance to stars is to use the astronomical parallax. The apparent shift in position of a star as it orbits the sun. The reciprocal of this measured in seconds of arc is the distance in Parsecs. The largest parallax is about 3/4 of a second of arc or a distance of 1.3 parsecs. So no star is within a parsec and most parallaxes are far smaller than this or the stars are much further away. Using 10 parsecs is thus a compromise and big enough to include all stars except the sun.
Hope this helps.
Gary Karshner
St. Mary's University

-----Original Message-----
From: Phys-l [] On Behalf Of Bill Nettles
Sent: Friday, September 14, 2012 3:09 PM
Subject: [Phys-L] absolute magnitude

I've done some searching, but obviously not in the right places:

How did astronomers arrive at 10 parsecs as the distance used for computing absolute magnitudes?

Bill Nettles
Union University
Forum for Physics Educators