Winter Milky Way

On summer nights, Earth faces the heart of the Milky Way Galaxy. That part of the Milky Way features dense clouds of stars. Under dark skies, it’s quite a sight. But during the long, cold nights of winter, we’re facing the opposite direction – toward the galaxy’s edge. So the Milky Way looks thin and faint – a bare ghost of its summer glory.

No matter which direction you face, the hazy band of light known as the Milky Way represents the combined glow of millions of stars that outline the galaxy’s disk. The disk is about a hundred thousand light-years wide, but only a few thousand light-years thick. It contains a few hundred billion stars.

The center of the galaxy is densely packed, like the downtown of a major city. But its outskirts are like the suburbs. There are fewer stars, and they’re more widely spread. And the closer to the galaxy’s edge, the more thinly spread the stars become.

The Milky Way doesn’t end at the edge of the disk. The disk is surrounded by a “halo” of stars and dark matter. It extends hundreds of thousands of light-years into space in every direction. But the halo is like the countryside – a few solitary residents spread far and wide. So nothing in the halo is visible without a good telescope – far outside the galaxy’s disk.

The Milky Way arcs high across the sky on February evenings. You need nice dark skies to see it – the thin but still beautiful glow of our home galaxy.

Script by Damond Benningfield