Saturday, June 27, 2009

Night of the Hunter . 1

Heralding the fall of the year, the great hunter Orion returns in October to dominate the nighttime sky. Then, just before Halloween, to clear the way for his climb to the top of the winter heavens, he shoots his arrows across the sky, every three minutes or so, in the Orionid meteor showers which peak around October 21.

Orion is one of the most conspicuous constellations in the sky. There he is below, seen through a telescope with lines connecting the main stars drawn to form the figure of The Hunter. Do you recognize him?

The hunter can be identified just by his glowing 'belt' of three medium brightness stars, evenly spaced in a straight line angling eastward.

Below the belt, pointing earthward, hangs his 'sword' of three more stars in a row. The fuzzy middle one is actually the Orion Nebula (M 42, pictured above), a vast stellar nursery.

In mid-October, Orion is just beginning to rise in the southeast at a typical backyard viewing time of 10:00 PM EST (mid-northern latitudes). The peak viewing dates - when Orion has fully risen in the south at the more reasonable hour of 10:00 PM - are in mid-January.

Four bright stars outline Orion's body (top left around to lower left) ... Betelgeuse, Bellatrix, Rigel and Saiph.

The jeweled belt consists of (left to right) ... Mintaka, Alnilam and Alnitak. Miessa forms the hunter's head.

Do these names sound exotic and maybe Arabic? They are. The Arabs were the first systematic observational astronomers in the west and as such had the privilege of naming many stars in the heavens, including seven of the main stars of Orion. Bellatrix is Greek for woman warrior and Orion himself is the hunter of Greek mythology.

The reddish-orangish star defining Orion's right shoulder (top left) is Betelgeuse, a red supergiant, one of the biggest and the brightest stars in the sky.

If this star replaced our sun this monster, 13th biggest in the universe, would extend out past the (former) orbit of Mars. It's the 9th brightest star in the heavens and usually the 2nd in Orion. It's a variable - a star who's light output varies significantly over time - and will sometimes out-shine the constellation's usually brightest star, Rigel, located in the left foot (lower right).

It's a hot young star, only several million years old, and possibly poised to explode quite soon on the cosmic stage as a supernova. If it does, or possibly already has (given the time light takes to travel), we will have front row seats as it's a mere 640 light years away. If it blew up in the late Middle Ages we should be hearing the news fairly soon.