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Re: [Phys-L] absolute magnitude

I searched for absolute magnitude history in Google and the first item shown was "The introduction of Absolute Magnitude (1902-1922)" by DW Hughes in Journal of Astronomical History and Heritage 9(2), 173-179 (2006).

Hughes addresses three questions about absolute magnitude. Who introduced the concept and when, who decided that the reference distance should be 10 pc and when was this commonly accepted?

Bruce McKay

On 16/09/2012, at 2:37 AM, Dan Schroeder <> wrote:

There isn't really a "typical" distance for the visible stars of the night sky. Most of them are between 100 and 1000 light-years away, but about 15% are closer, and about 10% are farther. The distance distribution is so broad that calling any value "typical" would be misleading. This is because the intrinsic luminosities of stars vary by many orders of magnitude, allowing the rare, very luminous stars to be seen over vast distances, while most of very closest stars can't be seen without a telescope. In any case, 10 parsecs (33 light-years) is closer than all but a couple percent of the naked-eye stars, and nearly half of the naked-eye stars are more than ten times as far away.

Dan Schroeder

From: John Mallinckrodt <>
Date: September 14, 2012 3:51:38 PM MDT

My guess would be that that is a typical distance for stars that actually ARE visible (there are ~400 stars within 10 parsecs) so adopting this standard means that most stars will have *absolute* magnitudes that line up nicely with familiar *visual* magnitudes.

John Mallinckrodt
Cal Poly Pomona

On Sep 14, 2012, at 1:09 PM, Bill Nettles wrote:

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

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