Only a few of the closest stars can be seen without a telescope.
The Sun has 33 stars within 12.5 light years from it. Many of these are tiny dwarf stars that cannot be seen by the naked eye, but some, such as the Alpha Centauri and Sirius binary systems, are extremely bright stars when viewed from Earth. Their proximity to the Sun makes these stars very interesting to astronomers because they could conceivably be visited one day by space probes or even humans.
Proxima Centauri
Proxima Centauri is the closest star to planet Earth. It is a red dwarf star, which means it is a relatively cool star with a mass of less than half the Sun. Proxima is 4.2 light years away, but, because of its size, it is too dim to be seen by the naked eye. Robert Thorburn Ayton Innes discovered Proxima Centauri in 1915 by using a telescope.
Alpha Centauri
Alpha Centauri is actually a binary star system, composed of Alpha Centauri A and Alpha Centauri B. This system is visible to the naked eye as a single star in the constellation Centaurus, the Centaur. Together they are the third-brightest "star" in the sky. They are 4.3 light years away from the Sun, slightly farther than Proxima Centauri, which may also be a part of this gravitationally bound system. Alpha Centauri A is approximately 110 percent of the Sun's mass and is about 50 percent brighter. Alpha Centauri B is approximately 90 percent of the Sun's mass and 50 percent as bright, making the pair relatively similar to the Sun.
Barnard's Star
Barnard's star is the next-closest star after the three Centauri stars. It is a small red dwarf star that is not visible to the naked eye. E.E. Barnard discovered the star in 1916. Currently it is 6 light years away from the Sun, although it is rapidly moving in the Sun's direction, at 140 kilometers per second. In several thousand years, it will become the closest star to the Sun and will reach 3.8 light years in 8,000 to 9,000 years.
Sirius
Sirius, the Dog Star of the constellation Canis Major, is the closest visible star after the Alpha Centauri system, although Barnard's Star, Wolf 359 and Lalande 21185, three red dwarf stars invisible to the naked eye, are all closer. Sirius is the brightest star in the night sky, about twice as massive as the Sun and 25 times more luminous. It is 8.6 light years away. Sirius is actually a two-star system, with the bright Sirius A orbited by the small white dwarf Sirius B, which is invisible to the naked eye.
Tags: Alpha Centauri, light years, light years away, Proxima Centauri, years away, Alpha Centauri Alpha
