Antares is a red supergiant star in the Milky WayGalaxy and the sixteenth brightest star in the night time sky. It is sometimes listed as 15th brightest, if the two brighter components of the Capella quadruple star system are counted as one star. Along with Aldebaran, Regulus, and Fomalhaut, Antares comprises the group known as the 'Royal stars of Persia'. It is one of the four brightest stars near the ecliptic. It is the brightest star in the constellation Scorpius, and is often referred to as "the heart of the scorpion". Antares is a slow irregular variable star with an average magnitude of +1.09.[3] Antares is the brightest, most massive, and most evolved stellar member of the nearest OB association. Antares is a member of the Upper Scorpius subgroup of the Scorpius-Centaurus Association, which contains thousands of stars with mean age 11 million years at a distance of approximately 145 parsecs (470 light years).
Antares is visible in the sky all night around May 31 of each year, when the star is atopposition to the Sun. At this time, Antares rises at dusk and sets at dawn as seen at the equator. For approximately two to three weeks on either side of November 30, Antares is not visible in the night sky, because it is near conjunction with the Sun;[13] this period of invisibility is longer in the Northern Hemisphere than in the Southern Hemisphere, since the star'sdeclination is significantly south of the celestial equator.
Antares has a secondary, or companion star, Antares B, that changed from an angular separation (from its primary, Antares A) of 3.3 arcseconds in 1854 to 2.86 arcseconds in 1990. The last is equal to a projected separation of about 529 Astronomical Units (AU) at the estimated distance of Antares, giving a minimum value for the separation of the pair. Spectroscopic examination of the energy states in the outflow of matter from the companion star suggests that it is about 224 AU beyond the primary,[6] giving a combined separation of about 574 AU.[14] The stellar classification of this star is B2.5,[11] with numerous spectral lines suggesting it has been polluted by matter ejected by Antares A.[6] At magnitude 5.5, it is only 1/370th as bright visually as Antares A, although it shines with 170 times the Sun's luminosity.[11]
The companion star is normally difficult to see in small telescopes due to glare from Antares A, but can sometimes be seen in apertures over 150 mm (5.9 in).[15] The companion is often described as green, but this is probably either a contrast effect[11] or the result of the mixing of light from the two stars when they are seen together through a telescope and are too close to be completely resolved. Antares B can sometimes be observed with a small telescope for a few seconds during lunar occultations while Antares A is hidden by the Moon. It was discovered byJohann Tobias Bürg during one such occultation on April 13, 1819,[16] but until its existence was confirmed in 1846 it was thought by some to be merely the light of Antares viewed through the Moon's atmosphere (which at the time was theorized to exist).[17] When observed by itself during such an occultation, the companion appears a profound blue or bluish-green color.[17]

Antares is one of the 4 first magnitude stars that lies within 5° of the ecliptic (like Spica, Regulus and Aldebaran) and therefore can beocculted by the Moon and, though rarely, by Venus. The last occultation of Antares by Venus took place on September 17, 525BC; the next one will take place on November 17, 2400. Other planets did not occult Antares in the last millennium nor will they do so in the next millennium, as they pass as a result of their actual node position and inclination always northward of Antares. On 31 July 2009, Antares was occulted by the Moon. The event was visible in much of southern Asia and the Middle East.[20][21] Every year around December 2 the Sun passes 5° north of Antares.

Antares, the proper name of this star, derives from the Ancient Greek Άντάρης, meaning "anti-Ares" ("anti-Mars"), due to the similarity of its reddish hue to the appearance of the planet Mars.[22] The comparison of Antares with Mars may have originated with earlyMesopotamian astronomers.

Antares, also called alpha Scorpii, is a prominent star in Scorpius (the Scorpion), a constellation that is visible in the southern night sky of most locations in the Northern Hemisphere. Antares is about 604 light-years from Earth. It is 700 times the sun's diameter, large enough to engulf the orbit of Mars, if the solar system were centered on it.
Antares is a two-stage launch vehicle designed to provide responsive, low-cost, and reliable access to space for medium-class payloads weighing up to 6120 kg. Initially developed to demonstrate commercial re-supply of the International Space Station under a NASA Commercial Orbital Transportation Services (COTS) contract, the Antares launch system utilizes many management approaches, engineering standards, production and test processes common to Orbital's family of highly successful small-class Pegasus®, Taurus®, and Minotaur launch vehicles. These proven launch technologies, along with hardware from some of the world's leading aerospace suppliers, combine to provide cost-effective access to a variety of orbits for civil, commercial and military Delta II-class payloads. The first launch of Antares took place on April 21, 2013.

Antares is a star that is in the constellation Scorpius. It is somewhere between 10,000,000 and 15,000,000 years old. In spite of this, it is almost at an end of its life. This is because it is a very massive star.