Stars {star} have different sizes and ages.
names
Famous stars are Aldebaran, Algol, Altair, Antares, Arcturus, Betelgeuse, Canopus, Capella, Deneb, Polaris or North Star, Pollux, Procyon, Regulus, Rigel, Sirius, Spica, and Vega. Sirius or Dog Star is brightest star. Six-star groups {Pleiades} can be in winter sky. Sky can have star clusters {Hyades}.
nearby stars
Nearest star is dwarf star Proxima Centauri, at 4.2 light years. The class-G star Alpha Centauri is at 4.3 light-years. Nearest single class-G star with possible life is Tau Ceti, at 11.2 light-years. The nearest stars lie in five general directions away from Earth.
planet
20% of stars have planets, typically one or two times Jupiter size.
first stars
The first stars formed 100,000,000 years after universe origin. They were 100 to 1000 times more massive than Sun. They were 4 to 14 times wider. They were 1 to 20 million times brighter. They had surface temperature 100,000 K. They lasted only 3 million years, forming big black holes.
first stars: reionization
Light from first stars ionized hydrogen and helium {reionization} and caused 5% to 17% of CMB.
Physical Sciences>Astronomy>Star
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Date Modified: 2022.0224