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All About Astronomy
|Our Solar System||Stars||Glossary||Printables, Worksheets, and Activities|
|The Sun||The Planets||The Moon||Asteroids||Kuiper Belt||Comets||Meteors||Astronomers|
|Lifecycle||Nuclear Fusion||Brightest Stars||Galaxies||Other Solar Systems||Constellations||Why Stars Twinkle|
|Birth||Death||Star Types||Closest Stars||Nebulae||Major Stars||The Zodiac||Activities, Links|
Aldebaran is the brightest star in the constellation Taurus (it is one of the bull's eyes) and is the 13th brightest star in the sky. Aldebaran is seen along the ecliptic. Aldebaran means "the Follower" in Arabic (since it seems to follow the stars in the Pleiades. Aldebaran is an giant, old, orange star that is cooler than the Sun; it is under 4,000 Kelvin (the Sun is 5,800 Kelvin). Aldebaran is about 40 times as big as the Sun.
Alnitak (Zeta Orionis) is a star at the eastern end of the Orion's belt (in the constellation Orion). Alnitak means belt. Alnitak is spectral Type O9.7Ib. It is also known as Alnitah.
Alpha Centauri is the star system that is closest to the Earth. The dimmest star in the system, Proxima Centauri (Alpha Centauri C), is the closest star to us (other than our sun). The stars Alpha Centauri A and Alpha Centauri B are close binary stars.
(Alpha Scorpii) Antares (meaning "Rival of Mars") is the brightest star in Scorpius, one of the constellations in the zodiac. Antares is a M1.5Iab variable red supergiant star that is about 520 light-years from Earth and is about 230 times as big as the Sun. This incredibly massive, old, low-temperature (3500 K) star is the 15th brightest star in the sky; it has a visual (apparent) magnitude of +0.96 (var.) and an absolute magnitude of -5.2.
(Alpha Boötis) Arcturus is the brightest star in the constellation Boötes (the herdsman). It is a red giant (spectral type K1.5IIIp) that is the fourth brightest star in the sky. Arcturus is 34 light-years from Earth. It has an apparent magnitude of -0.04 and an absolute magnitude of 0.2.
(pronounced "beetle juice") Betelgeuse (alpha Orionis) is the second-brightest star in the constellation Orion and one of the brightest stars in the sky. It is a supergiant star, reddish in color, and over 600 million miles in diameter (almost 1,000 times bigger than the Sun but cooler than the Sun). Betelgeuse is about 14,000 times brighter than the Sun. If Betelgeuse were at the center of our Solar System, it would extend beyond the orbit of Jupiter. It is 520 light-years from Earth. It is a variable star, varying in magnitude from 0.3 to 1.2 over a period of about 7 years, averaging about 0.70. It is the only star (other than our sun) for which we have surface images.
Boötes (the herdsman) is a large constellation in the northern hemisphere. The brightest star in Boötes is Arcturus, a red giant that is the fourth brightest star in the sky.
Canis major (The Great Dog) is a constellation near Orion. The brightest star in Canis Major (and the brightest star in the sky) is Sirius, also known as the dog star. Canis Major is one of the constellation Orion's hunting dogs (together with Canis Minor).
Capella is a multiple star system containing at least 9 stars. This bright system is in the Northern Hemisphere, 45 degrees from Polaris (the northern pole star); it is in the constellation Auriga. The two brightest stars in Capella are a binary star system. They are both yellow (like our Sun) with masses 2.6 times and 2.7 times that of the Sun. One is 9 times as large as the Sun, the other is 12 times as large. Each gives off roughly 78 times the light as the Sun. These two stars are about 43 light years from Earth.
Deneb (which means "tail" in Arabic) is the brightest star in the constellation Cygnus (the swan); Deneb is also referred to as alpha Cygni, and is the tail of the swan. This young, bright, white supergiant star is perhaps 1,500 light years away. Deneb is about 60,000 times more luminous than the sun!
Mira (Omicron Ceti) is a well-known variable red giant star in the constellation called Cetus. It was discovered in 1596 by David Fabricus, an amateur Dutch astronomer. Mira (meaning "wonderful") was named by Johannes Hevelius in 1662. Its mass is about the same as our Sun but it varies in size and brightness over a period of 332 days (about 11 months). During this period, its magnitude varies from 3.4 to 9.3.
Nemesis is a hypothetical companion dark star to our Sun. Once every 30 million years, this dark star would pass through the Oort cloud, triggering comets that perhaps cause periodic mass extinctions on Earth.
The north star is a star that is located almost due north and is useful for navigation. Polaris is currently the pole star of the Northern Hemisphere.
Polaris (alpha UMi) is the current pole star for the Northern Hemisphere; it is 1 degree from the exact Northern celestial pole. In 1780, Sir William Herschel discovered that Polaris was a double star with a faint companion star. Polaris is a blue-green Cepheid variable star (its size brightness changes periodically, with period of 3.969778 days; it varyies between mag 1.92 and 2.07). Polaris has a relatively dim companion star (9th magnitude). Polaris' distance from Earth has been estimated to be from 360 to 820 light years. At its brightest, Polairs is about 6,000 to 10,000 times brighter than our Sun. It is the larger star at the end of the handle of the Little Dipper (Ursa Minor). Polaris is also called the Lodestar or the Cynosure.
The closest star to us is the Sun. Other than that, the closest star is Proxima Centauri, aka Alpha Centauri C (the dimmest star in the Alpha centauri system). Proxima Centauri is about 4.2 light-years from the Sun. It has an absolute magnitude of 15.5 and an apparent magnitude of +11.05 (variable). Spectral type M5.5Vc.
Rigel (beta Orionis) is the brightest star in the constellation Orion and one of the brightest stars in the sky. It is a blue (very hot) supergiant, over 60 million miles in diameter (almost 100 times bigger than the sun). It is more than 50,000 times more luminous than the Sun. It has an absolute magnitude of -7.1 and an apparent magnitude of +0.12. It is over 900 light-years from Earth.
Sirius (meaning "scorching" in Greek), also known as the dog star, is the brightest star in the sky (except for the sun). It is in the constellation Canis Major (The Great Dog). Sirius is a main sequence star that is about 70 times more luminous than the sun. It is about 8.6 light-years from Earth. It has an apparent magnitude of -1.46 and an absolute magnitude of +1.4. Sirius has a companion star (called the Pup), which is a white dwarf.
The Sun is a star at the center of our solar system. Our Sun is a medium-sized yellow star that is 93,026,724 miles (149,680,000 km) from Earth. Its diameter is 865,121 miles (1,391,980 km). At its core, nuclear reactions produce enormous amounts of energy, through the process of converting hydrogen atoms into helium atoms (nuclear fusion). Its absolute magnitude is +4.83. The solar mass is 1.99 x 1030 kg.
Upsilon Andromedae is a star in the constellation Andromeda. Astronomers Geoffrey W. Marcy and R. Paul Butler discovered a massive planet orbiting this star (with each orbit taking only 4.6 days.) in 1996. Recently, 2 even more massive planets have been discovered orbiting this star. The three planets orbit within 2.5 Astronomical Units of the star.
Vega (Alpha Lyrae) is a very bright star in the constellation Lyra. It is also known as the Harp Star and Fidis. Vega is the 5th brightest star in the sky and is pale blue. It is about 25 light years from Earth. Its spectral type is A0Va. A disk of dust surrounds Vega, from which planets might form. Vega, together with Deneb and Altair form the Summer Triangle.
Zeta Orionis (Alnitak) is a star at the eastern end of the Orion's belt (in the constellation Orion). Alnitak means belt. Alnitak is spectral Type O9.7Ib. It is also known as Alnitah.
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