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Winter Milky Way

February 17, 2015

The subtle glow of the Milky Way arcs high across the sky early this evening. If you’re away from pesky city lights, look for it stretching from the southeast to almost directly overhead and then down to the northwest.

The band of light we see as the Milky Way is the combined glow of millions of stars in the disk of our home galaxy. The disk is about a hundred thousand light-years wide, and we’re more than half way out toward its edge.

On summer evenings, we face the heavily populated center of the galaxy, so the Milky Way is brighter and thicker. At this time of year, though, it’s far less impressive because we’re looking away from the center of the galaxy and toward its thinly settled outskirts. In fact, the point that’s directly opposite the galactic center is high overhead in early evening, between the bright stars Capella and Aldebaran.

Even though the Milky Way looks relatively thin at this time of year, we do see a collection of some of the brightest stars in the night sky. Many of those stars are in the Orion spiral arm — the same one that holds our own solar system. The spiral arms are where most of the galaxy’s stars are being born, so they include many bright young stars. More about the Orion Arm tomorrow.

For now, look for the Milky Way arcing high overhead this evening. It’s brightest in the northwest, with a thinner band passing overhead and to the southeast, against the brilliant stars of Orion.


Script by Damond Benningfield, Copyright 2014

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