Antares - Properties

Properties

Antares is a supergiant star with a stellar classification of M1.5Iab-b. 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.

The size of Antares may be calculated using its parallax and angular diameter. The parallax angle is given in the box to the right, and the angular diameter is known from lunar occultation measurements (41.3 ± 0.1 mas). This leads to a radius of 822 ± 80 solar radii.

Antares is a type LC slow irregular variable star, whose apparent magnitude slowly varies from +0.88 to +1.16.

Antares is visible in the sky all night 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. 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; 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 celestial equator.