Wednesday 26 August 2020

Astrognome 100 Great Stars No. 12 Antares



Antares is the brightest star in the constellation of the Scorpion, the constellation is well named because it looks for all the world liked the feared arachnid, its curved deadly tail swooping downwards. Antares marks the heart of the scorpion. Antares can be seen in late spring and early summer evenings from Britain. It will always be seen low in the sky. If you travel down to the Mediterranean area Antares and the rest of the scorpion will be much higher in the sky.

Antares or the ‘Rival of Mars’ due to its very red colour is an M1 supergiant star with a surface temperature of only around 3,500 degrees centigrade, cooler that the Sun at 5,800 degrees. It lies at a distance of about 550 light years. Antares is so big that if it was placed where the Sun is all the planets out to Uranus would actually be inside Antares.

In ancient Greece the constellation of the scorpion was much larger and covered the area which is now occupied by the constellation of Libra. Alpha and Beta Librae are known respectively as the ‘southern claw’ and the ‘northern claw’ confirming their link with the scorpion. It was the Romans who separated the stars and formed Libra.

Antares appears as a single star but it does have a companion star with a magnitude 5.5 however Antares is so bright that its light drowns out that from its companion. It cannot be seen with the naked eye or even a small telescope. A star with a magnitude of 5.5 could just be seen with the naked eye if you are observing from a very dark site. The companion star is a B2 class star with a surface temperature of around 18,000 degrees.

Antares is one of the largest stars that can be seen with the naked eye, however things will change in the next few tens of thousands of years when Antares will destroy itself in a supernova explosion. This Antares supernova could become as bright as the full moon and even be visible in the day time sky.

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