How bright is the Milky Way’s core?

The core of the Milky Way galaxy is obscured from Earth by a dust cloud. Without dust in the way, how big and bright would the galaxy’s core appear on sky’s dome?

The Milky Way galaxy is a collection of hundreds of billions of stars, and this island of stars contains our sun and planets. Astronomers have estimated that the total luminosity of the central dozen or so light-years of our galaxy is equal to about 10 million suns.

That sounds big and bright – until you recall that the center of our galaxy is 25,000 light-years away. At that distance, if interstellar dust weren’t in the way, our unaided eyes would see a central glow no bigger than the planet Venus – and no brighter than one of the stars of the Big Dipper.

Of course, interstellar dust obscures more than just this central region. It also dims the light of billions of foreground stars – as well as stars surrounding the core itself.

If there were no dust, the light of all these stars in the direction of the galactic center would easily exceed that of a full moon. If you looked in that direction, you wouldn’t see much else but the combined glow of billions of stars.

September 4, 2008

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