Similar to the relief many of us felt when the sun returned after this summer’s total solar eclipse is our mood after the winter solstice, when we celebrate the year’s shortest span of daylight. The days begin to lengthen, heralding the promise of spring yet to come. But the December solstice is officially just the beginning of the winter season, which is typically quite rainy here in the mid-Willamette Valley.
Amateur astronomers, however, take advantage of the long nights when the occasional clear skies permit brilliant views of some of the more impressive constellations. By 6 p.m. the sky is dark.
In Taurus, about a third of the way from the eastern horizon to the zenith, you’ll see a compact group of moderately bright stars. Often confused with the Little Dipper (Ursa Minor), these are the Pleiades, also known as the Seven Sisters, an open cluster of hot blue-white stars about 400 light years distant. The light we now see left the cluster around the time that Galileo, using his telescope, was just beginning to revolutionize astronomy and the way we view ourselves with respect to the cosmos.
Orion, the mighty hunter, a son of Neptune, is well above the eastern horizon by 8 p.m. Perhaps the most conspicuous of constellations, Orion’s seven brightest stars, all hot, blue-white giants save for one, form an hourglass shape. His two most luminous are named Rigel and Betelgeuse.
The obviously red and bright Betelgeuse marks his right shoulder. A monster of a star, Betelgeuse is a super-giant with a diameter greater than the orbit of Mars. At a distance of 500 light years it’s slightly farther away than the dimmer Pleiades.
Rigel, his left foot, is a hot, super-giant, blue-white star, and like Betelgeuse, is more than 100,000 times more luminous than our sun. Even at its distance of 860 light years, Rigel shines as the seventh brightest in our sky.
Bellatrix and Saiph mark Orion’s left shoulder and right foot, respectively. But the most obvious parts of this constellation have to be the belt and sword of the great hunter. Between Betelgeuse and Rigel, the Belt of Orion is a striking line of three bright stars, vertically aligned in the early evening. On top is Mintaka, the middle is Alnilam and on the bottom, Alnitak. All seven star names, except for the Latin Bellatrix, are Arabic.
To the lower right of his belt, Orion’s sword at first glance appears to be a line of three, somewhat fainter points of light. On closer inspection, however, the middle one reveals itself to be a fuzzy, reddish patch of nebulosity. Obvious in binoculars and spectacular in a telescope, this is none other than the great Orion Nebula, a stellar nursery of gas, dust and newborn stars about 1,300 light years away. It’s best seen around midnight, when the big hunter stands upright high in the southern sky.
Resource: HVA club
The Heart of the Valley Astronomers is a group of amateur astronomers dedicated to sharing our passion for the sky with the local community. We meet on the second Tuesday of each month (next: January 9 at 7 p.m.) at the Walnut Community Room, 4950 NW Fair Oaks Drive, Corvallis. Meetings are free and open to everyone. For more information, see www.hvaastronomy.com, or visit us on Facebook.
Astronomy Question of the Month
In which constellation is the famous Horsehead Nebula located?
Answer to Last Month’s Question: Venus is the planet that comes closest to the Earth.