Antares (α Scorpii, α Sco, Alpha Scorpii) is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime 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?, Spica, and Regulus 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 variable star with an average magnitude of +1.09. Antares is the brightest, most massive, and most evolved stellar member of the nearest OB association (the Scorpius-Centaurus 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).
It has a radius of approximately 883 times that of the Sun; if it were placed in the center of our solar system, its outer surface would lie between the orbits of Mars and Jupiter. Based upon parallax measurements, Antares is approximately 550 light-years (170 parsecs) from the Earth. Its visual luminosity is about 10,000 times that of the Sun, but because the star radiates a considerable part of its energy in the infrared part of the spectrum, the bolometric luminosity equals roughly 65,000 times that of the Sun. The mass of the star has been calculated to be in the range of 15 to 18 solar masses. A recent analysis comparing the effective temperature and luminosity of Antares to theoretical evolutionary tracks for massive stars which include rotation and mass loss yielded a mass of approximately 17 solar masses and age of 12 million years old.
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, giving a combined separation of about 574 AU. The stellar classification of this star is B2.5, with numerous spectral lines suggesting it has been polluted by matter ejected by Antares A. 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.
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). The companion is often described as green, but this is probably either a contrast effect 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 by Johann Tobias Bürg during one such occultation on April 13, 1819, 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). When observed by itself during such an occultation, the companion appears a profound blue or bluish-green color.
The orbit of the companion star is poorly known, with an estimated period of 878 years.
Antares in Space Opera
- "The Conscience of the King?" (1966) et al, episodes of Star Trek: The Original Series?, written by Barry Trivers? et al, as part of the film, television, and print franchise originated by Gene Roddenberry?. In several episodes, Lt. Uhura sings the romantic song "Beyond Antares," including the stanza The skies are green and glowing/ Where my heart is/ Where my heart is/ Where....the scented lunar flower is blooming/ Somewhere, beyond the stars/ Beyond Antares /..., lyrics by Gene L. Coon.
- "A Piece of the Action?" (1968), episode of Star Trek: The Original Series, written by David P. Harmon? and Gene L. Coon?, as part of the film, television, and print franchise originated by Gene Roddenberry. Captain Kirk invents a fictional card game called fizzbin which he claims is played on Beta Antares IV?, as a ruse to escape from his captors on the planet Sigma Iota II? (Sigma Iota is a fictional star, with a twisted "Bayer designation" consisting of two Greek letters; the equally impossible designation Beta "Antares" is the product of a related twist).
- Star Trek II: The Wrath of Khan? (1982), film written by Jack B. Sowards? and directed by Nicholas Meyer?, as part of the film, television, and print franchise originated by Gene Roddenberry. Khan says that he will chase Admiral Kirk "around the ... Antares Maelstrom."
- Frontier: Elite II? (1993) and Frontier: First Encounters? (1995), computer games written by David Braben et al. Hundreds of light-years away from populated space, the Antares system will remain unpopulated for the foreseeable future since it has no planets.
- Master of Orion II: Battle at Antares? (1996), computer based strategy game designed by Steve Barcia and Ken Burd. A conflict occurs between the Orions and the Antarans, who come from a planet called Antares.
- Escape Velocity. Game by Ambrosia Software. Antares is a system with a planet called New Providence.