Magnitude

Definition

Magnitude measures the brightness of a star or other celestial object as seen from Earth. It can be expressed in apparent magnitude (how bright the object appears) or absolute magnitude (the intrinsic brightness of the object at a standard distance).

5 Must Know Facts For Your Next Test

1. The lower the magnitude number, the brighter the star appears.
2. Apparent magnitude measures how bright a star appears from Earth, while absolute magnitude measures its intrinsic brightness at a fixed distance of 10 parsecs.
3. A difference of 5 magnitudes corresponds to a factor of 100 in brightness.
4. The scale for stellar magnitudes was initially developed by Hipparchus and later refined with more precise measurements.
5. Negative magnitudes are assigned to very bright objects, such as Sirius and the Sun.

Review Questions

• What is the difference between apparent magnitude and absolute magnitude?
• How does the magnitude scale quantify differences in star brightness?
• Why might two stars with the same apparent magnitude appear differently if viewed from different distances?

Related terms

Luminosity:

The total amount of energy emitted by a star per unit time.

Parsec:

A unit of distance used in astronomy, equal to about 3.26 light-years.

Hipparchus:

An ancient Greek astronomer who created one of the first known catalogs of star positions and magnitudes.