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== The star ==

== The star ==

The Antares system is actually a binary star system even though the unaided eye sees only the primary star.  The system itself is estimated to be some 600 light years from [[Earth]]; despite this distance Antares still has an apparent luminosity of +0.9 to +1.8, as it is a variable star.

The Antares system is actually a binary star system even though the unaided eye sees only the primary star.  The system itself is estimated to be some 600 light years from [[Earth]]; despite this distance Antares still has an average apparent luminosity of 1.09.  However Antares is a [[variable star]] and thus its luminousity ranges from  0.9 to 1.8 over a period of years.

The primary, Antares, is a class M1.5Iab-b [[supergiant]]<ref>http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=antares&submit=SIMBAD+search</ref> with a radius of 34 AUs, or some 700 times the radius of our own sun, if the star was at the center of our [[solar system]], it would extend to between the orbits of [[Mars]] and [[Jupiter]].  Despite Antares’ size, it contains only 15 to 18 times the mass of the sun; giving Antares a very low average density.  Its visual luminosity is some 10,000 time that of the sun, with an absolute luminosity of 60,000 times, much of which is in the infrared.  Like all M class stars, its surface is relativity cool in comparison to other stars, at 3600K<ref name="Illinois">http://www.astro.illinois.edu/~jkaler/sow/antares.html</ref>.

The primary star, Antares (also called '''Antares A'''), is a class M1.5Iab-b [[supergiant]].<ref>http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=antares&submit=SIMBAD+search</ref> The star is so large, that its diameter was calculated using its [[parallax]], and angular diameter, which lead to a radius of 822 ±80 that of our Sun.<ref>http://adsabs.harvard.edu/abs/1990A&A...230..355R</ref> If the star was at the center of our [[solar system]], it would extend to between the orbits of [[Mars]] and [[Jupiter]].  Despite Antares’ size, it contains only 15 to 18 times the mass of the sun; giving Antares a very low average density.  Its visual luminosity is some 10,000 time that of the sun, with an absolute luminosity of 60,000 times, much of which is in the [[infrared]].  Like all M class stars, its surface is relativity cool in comparison to other stars, at 3600K<ref name="Illinois">http://www.astro.illinois.edu/~jkaler/sow/antares.html</ref>.

Antares b, the companion star, is a blue star of spectral type B2.5V.  Although much dimmer then it’s giant companion, Antares b is still 170 times as luminous as our [[sun]].  By itself the star could be seen by the unaided eye, but because of the glare of its neighbor a small [[telescope]] is required to see the star at all.  It is estimated that the two stars are some 550AUs from each other, but their orbit is still poorly understood.

'''Antares B''', the companion star, is a blue star of spectral type B2.5V.  Although much dimmer then it’s giant companion, Antares B is still 170 times as luminous as our [[Sun]].  By itself the star could be seen by the unaided eye, but because of the glare of its neighbor, a small [[telescope]] is required to resolve the star at all.  It is estimated that the two stars are some 550AUs from each other, taking 878 years to complete an mutual orbit, but their orbit is still poorly understood.

Antares is coming towards the end of its [[stellar evolution]] and will soon develop an [[iron]] core, the last stage for a star of its mass before exploding into a [[supernova]]<ref name="Illinois">http://www.astro.illinois.edu/~jkaler/sow/antares.html</ref>.

Antares is coming towards the end of its [[stellar evolution]] and will soon develop an [[iron]] core, the last stage for a star of its mass before exploding into a [[supernova]]<ref name="Illinois">http://www.astro.illinois.edu/~jkaler/sow/antares.html</ref>.