Download 18.3 NOTES What is magnitude? Objective: Compare apparent

18.3 NOTES
What is magnitude?
Objective: Compare apparent magnitude and absolute magnitude
Without a telescope, you can see about 2000 stars in the night sky. Some appear
brighter than others. One way to measure a star’s brightness is by magnitude.
The brightness of a star depends on its temperature, size, and distance from
Earth. A hot star is usually brighter than a cool star. A large star is usually
brighter than a small star. The closer it is to earth, the brighter it appears to us.
The brightness of a star as
seen from Earth is called
the star’s apparent
magnitude. Planets can be
classified this way, too.
However, they shine only
with reflected light.
Using the scale of
apparent magnitude, a
star with a low number
appears brighter than a
star with a high number.
Very bright stars can even
have negative numbers.
For example, the apparent
magnitude of the Sun (a
bright star), is -26.8.
Absolute magnitude of a star is its actual brightness. It describes how bright a
star would appear to us if all the stars were the same distance from Earth. For
example, if the Sun were farther away from us, it would not appear as bright. A
dim star close to Earth would appear brighter than a bright star that is far away.
All stars have both an apparent magnitude and an absolute magnitude.