Les Dalrymple, long time Observatory Guide, and experienced amateur astronomer, tells us about Ares (aka Mars) and the star Antares…
The mid-evening eastern sky in early April this year is dominated by the planet Mars, now only about seven weeks from opposition, growing in brightness and as each night passes, becoming a more inviting telescopic target. Currently found within the stars of western Scorpius, Mars is 6º (about half the width of a fist held at arm’s-length) north of a star with which it shares a long association: Antares or Alpha (α) Scorpii.
The red planet has been connected with the Roman god of war, or Mars, within European cultures for about two millennia. Mars is the Latinised version of the equivalent classical Greek god of war — Ares. The Greeks similarly connected their god of war with the red planet and the star name Ant-ares therefore means the “rival of” or “equal of” Ares. Mars frequently passes close-by to Antares, that is about 4º from the ecliptic (the plane of our solar system), shares its colour and for the most part the two are similarly bright.
Antares is a bright, bloated, red supergiant star with a relatively low surface temperature of 3,600º C marking the heart of the scorpion. Notice that its rusty-orange hue is very comparable to Mars. Weighing approximately fifteen times the mass of our Sun and probably only about twelve million years old, Antares has given up core-hydrogen burning in favour of fusing heavier elements like Helium, Carbon and Oxygen. This presages its finale: a supernova explosion. Its demise is imminent (within astronomical time scales) — sometime within the next few hundred thousand years. Seen from our distance of about 550 light-years such an explosion would illuminate the night sky with a “star” almost as bright as the full moon.
While the light from Antares takes about 550 years to reach us, the light from Mars presently makes a somewhat shorter journey: a mere six light minutes or 110 million kilometres. By the 22nd of May that distance will be cut to 78 million kilometres when Earth finally catches-up to Mars in its orbit and Mars reaches opposition.
Why not book a night tour at Sydney Observatory in late May or early June to see Ares and Antares through our telescopes? As a bonus, Jupiter and Saturn will also be available for viewing too!