One of the ways that astronomy is enriched and romanticized is through the stories behind how various stars in the night sky have received their names. Most of these tales are shrouded in mysteries that date back to the cultures of earliest antiquity. This summer, however, Northern Colorado observers will have a chance to view up close and personal how one of the bright stars in the summer heavens came to receive its name.
The star of note is a reddish star which occupies the heart of the well-known constellation of Scorpius the Scorpion. Rather than being named as the “Scorpion’s Heart” or some other similar designation, this star was named Antares, which means “The Rival of Mars.” Mars, of course, is the planet with its own set of myths and legends, albeit from more recent times, and every two years or so the Red Planet passes to the north of Antares in its journey through the constellations of the zodiac. Antares, meanwhile, is a red supergiant star which would engulf all of the planets out to Jupiter were it to be placed at the center of our solar system. The remarkable fact about these two disparate objects is that to the naked eye they seem to have the same deep reddish-orange color, a fact which has been confirmed from more precise photometric color measurements made by astronomers. In the eyes of ancient sky-watchers the nearly identical colors of these two objects undoubtedly fueled the idea that Antares was the naturally logical choice for a celestial rival to Mars.
Usually whenever there is a Mars-Antares conjunction, Mars glows as the brighter of the two objects. For there to be a true rivalry, however, Antares ought to win at least a few of its brightness duels with Mars as it passes by, and from time to time, Antares enjoys such photometric victories. There will, however, be no such win for Antares this year. Mars is now closer to the Earth than it has been in over a decade and blazes like a celestial garnet more than six times brighter than its stellar rival. Over the next few months Mars will begin to fade in brightness as the Earth pulls away from the Red Planet, but the decline in the Martian brightness will not cost the planet a brightness victory as it passes north of Antares later on in the summer. The entire encounter can be viewed throughout the summer months in the early evening Colorado sky as Mars slowly creeps night to night across eastern Libra and northern Scorpius.
Even though Mars is much brighter than Antares, the striking similarity in the colors of the two objects is still readily obvious to either naked eye or binocular observations. Because of the relative proximity of Mars to the Earth during June, small telescopes under steady atmospheric conditions should also reveal the north polar cap as well as the major dark features on the planet’s disk.
Elsewhere in the sky: The planet Saturn reaches opposition to the sun on June 3 and is visible all night long all month long. The Ringed Planet brightly shines to the east of Mars and above Antares, and Saturn’s famed ring system can easily be viewed even in small telescopes
As darkness descends, the planet Jupiter can be located as a prominent yellowish-white object toward the southwest about halfway between the horizon and the zenith and remains visible to the west throughout the first half of the night.
The planets Venus and Mercury are too close to the sun the be easily seen in June.