Absolute brightness

the absolute brightness is an auxiliary variable in the astronomy, in order to be able to compare the actual brightness of celestial objects (usually stars).

From the earth one sees a star with its apparent brightness, there it by its distance and interstellar subject one affects.

In order to be able to compare the actual brightness, one imagines the stars at uniform distance. This amounts to ten Parsec (1 PC = 3.26 light-years). One calls the brightness, which an observer from this standard distance would measure, absolute brightness. With stars, thoseless than ten Parsec are distant, the apparent brightness more largely than the absolute brightness and turned around. As also with the apparent brightness a small numerical value means larger luminosity.

The way of writing in the astronomy reads (with a star of third size class) [itex] 3^M.0< /math>. With the absoluteBrightness is put up contrary to the apparent brightness a large “M”.

The absolutely brightest fixed stars reach about [itex] -9^M< /math> (over 100.000-fache luminosity of the sun), the faintest against it [itex] +17^M< /math> (about a ten thousandth of sun luminosity).

Bolometri brightness

major item: Bolometri brightness

this indicates the brightness of a star in the entire electromagnetic spectrum. The for this necessary correction depends on the sensitivity range of the measuring instrument as well as on the spectral type of the object concerned. Thosephotographic brightness of the sun amounts to [itex] 5^M.16< /math>, the bolometrische brightness against it [itex] 4^M.74< /math>.

distance module

the difference between absolute brightness M and apparent brightness m is called distance module. The formula for the distance module reads:

[itex] m - M = -5 + 5 \ log_ {10} r =-5 -5 \ log_ {10} \ pi [/itex]

R is the distance of the star in Parsec, π its parallax. With the help of this formula important for the astronomy can for stars, whose luminosity admits is (z. B. Cepheiden or Supernovae of the type Ia), which computes distancebecome. (In this way 1923 the distance of the Andromedanebels could be determined.)

objects in the solar system

with comets and Asteroiden the term absolute brightness is deviating defined, since they reflect only light. Here the situation impossible in the reality is accepted that thoseEarth and the sun in a place are and the object (the comet or Asteroid) exactly an astronomical unit far away stand. The brightness, with which the object would be to be seen then, is called absolute brightness.

comparison apparent one/absolute brightness of someHeavenly body

heavenly body apparent H. ([itex] m_V [/itex]) absolute H. ([itex] M_V [/itex]) distance
sun [itex] -26^m.73< /math> [itex] +4^M.84< /math> [itex] 4,85*10^ {- 6}< /math> Parsec
Sirius [itex] -1^m.5< /math> [itex] +1^M.4< /math> 2.76 Parsec
latch plates [itex] +0^m.1< /math> [itex] -6^M.2< /math> To 199.26 Parsec