# The Closest Star

 The closest star to the sun is Proxima Centauri, but its brighter neighbor Alpha Centauri, a double star, is so nearly the same distance that data about it are usually given. It is about 4 light years distance, or about 3.8x1016 m.

If our sun, which has diameter 1.392 x 109 meters were scaled down to the size of a period on a printed page, which is nominally about 0.5 mm, then the distance to Alpha Centauri would be about 13.6 km or about 8 miles away. If the Earth were scaled to 0.5 mm diameter, then the Sun would be a ball of diameter 5.4 cm ( a little smaller than a tennis ball) at a distance of 5.9 m (19 ft). On this scale, Alpha Centauri would be 1.48 x 106 meters or about 890 miles away. If the sun were scaled to a 1 foot radius, then Alpha Centauri would be about 10,300 miles away. The parallax ofProxima Centauri as the Earth orbits the sun is about equivalent to that of a dime at a distance of 6 kilometers.

There are 40 stars within 16 light years of the Earth.

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# Alpha Centauri

The closest star to the sun is Proxima Centauri, but its brighter neighbor Alpha Centauri, a double star, is so nearly the same distance that data about it are usually given. It is about 4 light years distance, or about 3.8x1016 m.If our sun, which has diameter 1.392 x 109 meters were scaled down to the size of a period on a printed page, which is nominally about 0.5 mm, then the distance to Alpha Centauri would be about 13.6 km or about 8 miles away. If the Earth were scaled to 0.5 mm diameter, then the Sun would be a ball of diameter 5.4 cm ( a little smaller than a tennis ball) at a distance of 5.9 m (19 ft). On this scale, Alpha Centauri would be 1.48 x 106 meters or about 890 miles away. If the sun were scaled to a 1 foot radius, then Alpha Centauri would be about 10,300 miles away.

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# Proxima Centauri

This star is notable for being the closest star to the sun, but its brighter neighbor Alpha Centauri, a double star, is so nearly the same distance that data about it are usually given. It is about 4 light years distance, or about 3.8x1016 m from the sun.

With its unique status as the closest star, Proxima Centauri, is an often quoted example of parallax distance measurement. The apparent ellipse in which Proxima Centauri moves during the year as a result of the Earth's orbit around the sun is about the size of a dime observed at three miles distance. Its parallax is 0.762 arcsec, corresponding to a distance of 1.31 parsecs.

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# Barnard's Star

Barnard's star is remarkable as a close star which is thought to have planets. The variations in its position indicate the presence of at least one and probably more than one non-luminous body orbiting it.

This star is also remarkable because it exhibits the largest proper motion, moving against the background of more distant stars by 10.3 arcseconds per year. Its distance is 5.9 light years.

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