Antares
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- This article is about the star. For other meanings, see Antares (disambiguation)
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| Observation data Equinox J2000 |
|
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 29m 24s[1] |
| Declination | -26° 25′ 55″[1] |
| Apparent magnitude (V) | 1.09[1] |
| Characteristics | |
| Spectral type | M1.5Iab-b / B2.5V[1] |
| U-B color index | 1.34 |
| B-V color index | 1.87 |
| Variable type | LC-type |
| Astrometry | |
| Radial velocity (Rv) | −3.4[1] km/s |
| Proper motion (μ) | RA: −10.16[1] mas/yr Dec.: −23.21[1] mas/yr |
| Parallax (π) | 5.40 ± 1.68[1] mas |
| Distance | approx. 600 ly (approx. 190 pc) |
| Absolute magnitude (MV) | −5.28 |
| Details | |
| Mass | 15.5 M☉ |
| Radius | 700 R☉ |
| Luminosity | 65,000(bolometric) L☉ |
| Temperature | 3,500 K |
| Metallicity | - |
| Rotation | - |
| Age | - years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Antares (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.
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[edit] Antares in ancient cultures
Antares' name derives from the Greek Αντάρης, 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. According to ancient Arab tradition, Antares is the warrior-poet Antar's star. Many of the old Egyptian temples are oriented so that the light of Antares plays a role in the ceremonies performed there. Some writers claim that it is the "lance star" referred to in the Biblical book of Job. Antares was also known as Satevis in ancient Persia and was one of the four "royal stars" of the Persians around 3000 BC. It is also known as Jyeshtha in ancient India. 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 
. Antares is the 15th brightest star that we know of.
[edit] Properties
Antares is a class M supergiant star, with a diameter of approximately 700 times solar. I.e., if in place of our sun, its outer surface would extend between the orbit of Mars and Jupiter. Antares is approximately 600 light years from our solar system. 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 equals roughly 65,000 times that of the Sun. The mass of the star is calculated to be 15 to 18 solar masses.[2] Its large size and relatively small 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 (this of course depends entirely on your own position on the globe). 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 significantly south of the ecliptic.
[edit] Companion star
Antares has a hot blue companion star (Antares B) at a distance of about 2.9″--or 550 AUs at Antares' estimated distance--of spectral type B2.5.[2] At magnitude 5.5, it is 1/370th as bright visually as Antares itself, yet still 170 times brighter than the Sun. It is normally difficult to see in small telescopes due to Antares' glare, but becomes easy in apertures over 150 mm (6 in.).[3] The companion is often described as green, but this is probably a contrast effect.[2] Antares B can be observed with a small telescope 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 orbit is poorly known, with an estimated period of 878 years.
[edit] Position on the ecliptic
Antares is one of the 4 first magnitude stars which lie within 5° of the ecliptic and therefore can be occulted by the Moon and rarely by the planets. On 17 Nov 2400 Antares will be occulted by Venus.
Of the 21 first-magnitude stars, Antares now lies further in angular distance from any other first-magnitude star; i.e. it is possible to 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.
[edit] See also
[edit] External links
- http://www.co-intelligence.org/newsletter/comparisons.html - A comparison of the size of Antares to other solar objects.
- EXPLORING THE FULL STELLAR POPULATION OF THE UPPER SCORPIUS OB ASSOCIATION
[edit] References
- ^ a b c d e f g h i j k l m n o p q SIMBAD Astronomical Database. Results for CCDM J16294-2626A/B. Retrieved on October 23, 2006.
- ^ a b c James Kaler, "Antares". http://www.astro.uiuc.edu/~kaler/sow/antares.html Accessed 2/3/07.
- ^ Robert Burnham Jr., Burnham's Celestial Handbook",(New York: Dover Publications Inc., 1978), p. 1666.
