Antares

 

Scorpius (the Scorpion) is the mos elegant constellation in the sky. At the moment we are in a very good position to look at it because it raises just after sunset and if you look at the Eastern sky then, you just can’t miss it. The tail on the right hand side forms a beautiful curve in then Milky Way and the triangle on the left represents the head and the claws. Just on the right of that triangle is the eye of the scorpion, the brightest star in it: Antares. Its distinctly red-orange colour is easily visible by naked eye.

Antares is a red giant. In the past we talked about Betelgeuse in Orion. There is another one called Aldebaran in Taurus. But Antares is bigger. To give you an idea of its size, just visualise the orbit of Mars around the Sun. Our Earth is at 150 millions kilometres from the Sun, Mars orbits the Sun at about 1.5 times that distance, or 225 millions kilometres. Antares’s radius is 473 million km, more than twice the orbital radius of Mars. In comparison our Sun is a tiny little thing with a radius of only 696,340 km.

In 1952 the American Association of Variable Star Observers discovered that Antares varies in brightness. The brightness period seems to be around 1733 days. Interestingly, the “Ngarrindjeri Aboriginal people from South Australia observed the variability of Antares and incorporated it into their oral traditions as Waiyungari (meaning 'red man'). Long before the western science woke up to it.

References:

Sky map: https://stellarium-web.org/

The picture is taken from that website.

Wikipedia: https://en.wikipedia.org/wiki/Antares

Hamacher, D.W. (2018). "Observations of red–giant variable stars by Aboriginal Australians". The Australian Journal of Anthropology.