Monday, September 5, 2016
Stroll outside on any late summer evening, look straight up and three very bright stars will catch your eye. These stars are named Vega, Deneb and Altair, and their familiar pattern is nicknamed the Summer Triangle.
Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.
Find more columns by Westlake here.
The southern-most star in the Summer Triangle is Altair. It is the 12th brightest star visible in the night sky, primarily due to its close proximity to Earth. Altair is only 17 light years away, which means that when we gaze at Altair, we see it as it was 17 years ago. According to the Research Consortium on Nearby Stars, there are only 52 stars closer to us than Altair.
The name Altair comes from the Arabic words for “the flying eagle.” This is a reference to the constellation Altair adorns with its light: Aquila, the Eagle. Altair marks the Eagle’s head and beak and is flanked on either side by slightly fainter stars, Alshain and Tarazed. Apparently, both these star names come from the ancient Persian name for the whole constellation, Shahin Tara Zed, which means the Star-Striking Falcon.
This trio of stars — Alshain, Altair and Tarazed — remind me of the three stars of Orion’s Belt, visible in winter, except that Altair, in the middle, far outshines its two neighbors. When seen close to the horizon, these three stars of the Eagle look like wing lights on a low-flying airplane.
Altair is known as one of the fastest spinning stars in the galaxy. Our sun spins rather slowly, once every 28 days, but Altair spins at the astonishing rate of once every 10 hours. This might be an indication that Altair lacks a planetary system, because planets tend to slow a star’s rotation. Perhaps this is of little consequence, anyway, since Altair is such a hot star it would render its planets uninhabitable.
The sprinkling of stars just south of Altair was recognized for many centuries as a separate constellation named Antinous. The Roman Emperor Hadrian introduced the constellation of Antinous in the year 132 AD. It immortalized a young servant who drowned himself in the Nile River, believing it would prolong his emperor’s life. In 1922, the International Astronomical Union discarded Antinous, along with dozens of other obscure star patterns, when it adopted the 88 official constellations now recognized worldwide. The stars of Antinous were added permanently to the stars of Aquila, the Eagle.
Aquila the Eagle, with its alpha star Altair, reaches its highest point in the sky about 10 p.m. this week. Face directly south and look about two-thirds of the way up from the horizon to the zenith. There shines Altair, flanked by Alshain and Tarazed, its companion stars.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Steamboat Campus. His "Celestial News" column appears weekly in Steamboat Today. Check out Westlake’s astrophotography website at jwestlake.com.