Real and apparent magnitude of a star

How big and bright a light looks depends on how bright it is and how far away we are from it.

A small star which is close to us will look similar to a large star which is far away. The brightness of the star as it appears to us from Earth is called “The Apparent Magnitude”.

Real and apparent brightness things look brighter just because they are close

Since light, like all radiation, spreads out according to the "Inverse Square Law" the apparent magnitude depends on one divided by distance squared.

The apparent magnitude of a star is how bright it looks fro Earth. The real magnitude is how bright we calculate that the star would be if it were 10 parsecs away.

The standard distance for assessing real magnitude is 10 parsecs.





To properly compare the brightness or magnitude of different stars we assess how bright they would seem to be if we were 10 parsecs away.




Other pages of notes and video on astronomy which may be useful are:

Units of distance notes and video    Measuring distance by parallax/triangulation notes and video     Life cycle of stars    Geostationary and polar satellites notes and video     Big Bang theory and evidence     Development of the Universe after the Big Bang       Hubble's Law and measuring distance notes and video     The age of the universe notes and video     Using Hertzsprung Russell diagrams notes and video     Cepheid variable stars      Type 1A supernova