2. Properties of Stars: Temperature, Color, and Brightness

Not all stars look the same in the night sky — some are bright, some dim, some bluish-white, some orange-red. These differences reflect real physical properties.

Temperature and Color:
A star's surface temperature controls its color. This follows the same physics as a heating metal:

Brightness — Luminosity vs. Apparent Magnitude:

• Luminosity is the total energy a star actually emits — its true brightness.
• Apparent magnitude is how bright a star looks from Earth. A very luminous star far away can look dimmer than a less luminous star nearby.

A star appears bright if it is intrinsically luminous, or if it is close to Earth — or both.

Size matters too: a star of the same temperature but larger surface area emits more total light. Giant and supergiant stars can be hundreds of times larger than the Sun.