Orion the Hunter has taken to the late autumn skies. One of the loveliest and easiest recognized constellations will be stalking the heavens till he slides into the daytime sky early next spring. Astronomers believe the Hunter, in his present form, is more than a million years old and think he will continue to stalk the heavens for another couple million years.
Look for Orion to start climbing above the south-southwestern horizon between 8 p.m. and 9 p.m. Orion’s belt – three relatively bright stars in a straight line – is pretty easy to pick out. The Hunter appears on his side, facing us, the belt pointing upwards from the horizon. Two bright stars to the north – Betelgeuse marks Orion’s left shoulder and Bellatrix, the right. Below the belt (to the southwest) is the brightest star in the constellation, Rigel, which marks Orion’s left foot.
These two stars are both supergiants – largest of stars. Betelgeuse is a red supergiant and Rigel is a blue supergiant. Both of these stars are much larger than our sun (perhaps 20 times more massive) and put out about 100,000 times as much heat and energy. Betelgeuse and Rigel are about 640 and 800 light-years from earth respectively.
Extending south from Orion’s belt is a smaller, fainter line of stars that create the Hunter’s sword. One of the glowing orbs in this sword isn’t truly a star at all. It is M42 – the Orion Nebula. A nebula is a giant complex of interstellar gas and dust. This gas and dust is continuously collapsing and creating new stars. Images from the Hubble Space Telescope have revealed as many as 3,000 stars in M42 and many of them youngsters, less than 10,000 years old.
The huge supergiants, Betelgeuse and Rigel have to defer to the Dog Star (Sirius) when it comes to brightness. Sirius will share the night sky with Orion all winter – and you can use Orion to find the Dog Star. If you draw an imaginary line through Orion’s belt downward (to the east) it will point to Sirius, the brightest star in the night sky, called the Dog Star because it is located in the constellation Canis Major. Although Sirius is only about 30 times brighter than the sun, it is only about nine light-years away making it brighter than the two supergiants. Canis Major and Sirius will follow the Hunter by about an hour or so.
Venus will also cozy up to the new moon for the next couple of days, making its brightest evening-star appearance. We may not be so lucky when it comes time for the Geminids, (December’s premier meteor shower) as the waxing moon will light up the night sky. The nights of December 12 and 13 are forecast to be peak for the Geminids this year and the best viewing will likely be just before dawn. The moon should set around 4 a.m. on the morning of Dec. 13 and around 5 a.m. on the 14th leaving a few hours before sunrise for a little meteor gazing.