Antares

From Free net encyclopedia

This article is about the star. For other meanings, see Antares (disambiguation)

Template:Starbox begin Template:Starbox observe Template:Starbox character Template:Starbox astrometry Template:Starbox catalog Template:Starbox end Antares (α Sco / α Scorpii / Alpha Scorpii) is the brightest star in the constellation Scorpius and one of the brightest stars in the nighttime sky. Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic. The similarly colored Aldebaran lies almost directly opposite Antares in the Zodiac.

Antares' name derives from the Greek ανταρης, meaning "(holds) against Ares (Mars)", due to the similarity of its reddish hue to the appearance of the planet Mars. This distinctive coloration has made the star an object of interest to many societies throughout history, and many of the old Egyptian temples are oriented so that the light of Antares plays a role in the ceremonies performed there. Antares was one of the four "royal stars" of the Persians around 3000 BC, and some writers claim that it is the "lance star" referred to in the Biblical book of Job. In the religion of Stregheria, Antares is a fallen angel and quarter guardian of the western gate. In astrology Antares is one of the Behenian fixed stars and has the symbol Image:Agrippa1531 corScorpii.png.

Antares is a class M giant star, with a diameter of approximately 9.24 × 10⁸ km, or slightly more than the distance from the Sun to Mars, and is approximately 600 light years from earth. Visually, its luminosity is about 10,000 times that of the Sun but overall, taking into account that the star radiates a considerable part of its energy in the infrared part of the spectrum the luminosity jumps to roughly 65,000 times that of the Sun. The mass of the star is calculated to be 15 to 18 solar masses. Its large size and relatively smaller mass give Antares a very low density.

The best time to view Antares is on or around May 31 of each year, when the star is at "opposition" to the Sun. At this time, Antares rises at dusk and sets at dawn, and is thus in view all night. For approximately two to three weeks on either side of November 30, Antares is not visible at all, being lost in the Sun's glare; this period of invisibility is longer in the Northern Hemisphere than in the Southern Hemisphere, since the star's declination is a few degrees south of the ecliptic.

Antares has a hot blue companion star (Antares B) at a distance of about 2.9″. Although it is 5th magnitude, it is normally difficult to see because of Antares' glare, but can be observed with the naked eye for a few seconds during lunar occultations while Antares itself is hidden by the Moon; it was discovered during one such occultation on April 13 1819. The orbital period is 878 years.

Of the 21 first-magnitude stars, Antares now lies further in angular distance from any first-magnitude star than any other first magnitude star, i.e. you could draw the largest circle centered around Antares without including any other first-magnitude star inside that circle. The nearest first-magnitude star to Antares is Alpha Centauri, lying approximately 39°6.75′ away. The high proper motion of Alpha Centauri is gradually increasing this angle. Before about March 2000, Achernar and Fomalhaut held this distinction.

In 1971, the crew of Apollo 14 named their lunar module after the star.als:Antares an:Antares ca:Antares da:Antares de:Antares es:Antares fr:Antarès gl:Antares it:Antares he:אנטארס lt:Antaris nl:Antares ja:アンタレス pl:Antares sk:Antares sv:Antares fi:Antares tr:Antares zh:心宿二