This Week Look Up and Check Out Scorpius
The most beautiful zodiacal constellation is low in the southern sky at chart time: Scorpius, the Scorpion. Scorpions have two large claws in front, but this one seems to have had his claws clipped.
In 1930, the International Astronomical Union (the same consortium that demoted Pluto to dwarf planet status in 2006) made the two claws of Scorpius into the arms of Libra, the Balance. But in spite of this, two stars that now officially lie within the boundaries of Libra, still to this very day bear the tongue-twisting Arabic names Zubeneschamali (“Northern Claw”) and Zubenelgenubi (“Southern Claw”).
The whole figure of the scorpion is a magnificent sight and is best appreciated now, in a dark sky, without any interference from bright moonlight. It really looks like a huge scorpion, with its long stinging tail curled over its back.
One star clearly outshines the others, with a fiery tinge seemingly emphasizing the scorpion’s sinister appearance. That’s Antares, the so-called “rival of Mars,” (Ares being Greek for Mars). It is often referred to as “the heart of the scorpion.” Along with Aldebaran, Regulus, and Fomalhaut, Antares comprises the group known as the “Royal stars of Persia.” It is one of the four brightest stars near the ecliptic.
Antares is a supergiant, 883 times the Sun’s diameter. Consider this: if our Sun were shrink down to the size of a baseball, Antares would be a globe measuring 177 feet in diameter! If we replaced the Sun with Antares, its outer surface would lie between the orbits of Mars and Jupiter. It is 10,000 times as luminous as the Sun and located about 550 light years away.
In the general vicinity of Antares this week are two bright planets that will be visited by the Moon this week: On July 14, Mars, low in the southern evening sky, is a prominent yellow-orange object in Libra the Scales. It crosses the meridian soon after sunset and remains above the horizon for most of the night. This evening, the “god of war” can be found 8° below the waxing gibbous Moon. The very next night (July 15) Saturn lies just over 2° below the waxing gibbous Moon and is almost due south when night falls. It is about 6½° above Antares; these golden and reddish lights accent the softness of the summer Milky Way.
Last, but not least, the stars Shaula and Lesath are a close pair of stars in the Scorpion’s stinger. Astronomy popularizer Hans A. Rey (1898-1977) christened these stars the “Cat’s Eyes,” noting, “You will find the name quite fitting.”