Magnitude

From Slackerpedia Galactica

Explanation of Term

A generally awful unit of measuring brightness and flux, first devised by Hipparchus. The response of the human eye to light is logarithmic (not to mention all that twinkling) so the logarithmic units of flux have some basis in reality. But for those of us who like SI units, they're awful. Less bright stars have larger magnitudes, and the brightest stars have negative magnitudes.

The modern magnitude scale is calibrated to the brightness of the A0V star Vega, whose apparent magnitude at all visible wavelengths is defined as "0.0". The scaling factor is defined such that five magnitudes corresponds to a flux difference of 100. Thus a change of one magnitude corresponds to a change in flux of the fifth root of 100, or about 2.512. The few stars brighter than Vega (e.g. Sirius) have negative magnitudes.

Just awful.

One star is very, very bright: the Sun. It has a magnitude of about -26. To see it, you have to wait until morning.

Brightest Stars (Apparent Magnitude)

Note: v means the star's magnitude is really variable and the listed magnitude is an "average".
^Star is part of a multiple star system but is listed individually
Binary stars are cheaters but are listed because no one wants to see a slapfight between astronomers.

	Apparent magnitude	Proper name	Distance (ly)	Absolute magnitude	Star type
1	-26.73	The Sun, Sol	REALLY CLOSE (1 AU)	4.75 (lousy)	Single star (We think)
2	-1.47	Sirius	8.6	1.4	Binary Star
3	-0.62	Canopus	310	-5.53	Single star
4	-0.04v	Arcturus	37	-0.31	Single star
5	-0.01	Alpha Centauri A	4.4	4.38	Trinary Star^
6	0.03	Vega	32	0.58	Single star
7	0.07	Capella A	42	0.4	Binary Star^
8	0.12	Rigel	770	-7.3	Trinary Star
9	0.34	Procyon	711	2.65v	Binary Star
10	0.50	Achernar	140	-1.3	Single star

Luminous(est) Stars (Absolute Magnitude)

Absolute magnitude is more well-liked by astronomers specifically because it is more objective of a measurement although not too terribly useful except for braggin' rights. Luminosity (used here to avoid confusion with brightness, which is associated with apparent magnitude) of a star is given from an arbitrary distance, 10 parsecs in this case. The absolute magnitude is interestingly enough, very hard to nail down, because many of the stars on this poor excuse for a David Letterman Top 10 List are far outside the 200 light-year radius where measurements can be accurately obtained.

With the efforts of the Hubble Space Telescope and the new James Webb Space Telescope, this chart may finally become more absolute and snobby to look down on the Brightest Stars chart on top of it.

v stands for a star whose luminosity is hard to judge, even from an absolute viewpoint due to lack of data or the star's own temperamental state.
vv is a special footnote just for Eta Carinae who has went from being a very luminous star on this table to being nearly invisible over the past 3 centuries.
^ means we think it's a single star but can't tell for the same reason we have that lame v footnote.
The authoritative Hipparcos Catalog list is longer and probably more accurate than this one. Some enterprising, brave, non-slacking, and foolish person should try matching up the entries for the sake of academic consistency one of these days.

	Absolute Magnitude	Proper name	Distance (ly)	Star type
1	-12.3v	Pistol Star	25,000	Single star^
2	-12.2v	Cygnus OB2-12	Fill me in!	Single star^
3	-12.1v	HD 93129A	10,000	Single star^
4	-12.1vv	Eta Carinae	7,600	Binary Star
5	-12.0'	LBV 1806-20	35,000	Binary Star^