SUMMARY OF KEY IDEAS

Magnitude Scales

The Temperatures of Stars

Types of Stars

Stellar Masses

WHAT DID YOU THINK?

  • How near to us is the closest star other than the Sun? The closest star, Proxima Centauri, is about 40 trillion km (25 trillion mi) away. Light from there takes about 4 years to reach Earth.

  • How luminous is the Sun compared with other stars? The most luminous stars are about a million times brighter, and the least luminous stars are about a hundred thousand times dimmer than the Sun.

  • What colors are stars, and why do they have these colors? Stars are found in a wide range of colors, from red through violet as well as white. They have these colors because they have different surface temperatures.

  • Are brighter stars hotter than dimmer stars? Not necessarily. Many brighter stars (such as red giants) are cooler but larger than hotter, dimmer stars (such as white dwarfs).

  • Compared to the Sun, what sizes are other stars? Stars range from more than 1000 times the Sun’s diameter to less than 1/100 of the Sun’s diameter.

  • Are most stars isolated from other stars, as the Sun is? Yes. In the vicinity of the Sun, one-third of stars are found in gravitationally bound pairs or larger groups.