M101

Not all galaxies are created equal. Many are featureless blobs of light. But others feature spectacular spiral arms that make them look like glowing celestial hurricanes. We live in one such galaxy, the Milky Way. And the constellation Ursa Major features another, known as M101.

Galactically speaking, M101 is a close neighbor — it’s about 22 million light-years away. It’s visible through a telescope near the handle of the Big Dipper, which is high in the north this evening. We see the galaxy face-on, so it’s one of the most beautiful spirals in all the night sky.

But the spiral arms of M101 are more than just beautiful. They also serve an important function: They squeeze interstellar clouds of gas and dust, causing them to collapse and give birth to new stars. Some of these newborn stars are quite bright, so they outline the galaxy’s spiral pattern.

These bright stars don’t live long, though — they quickly explode as supernovae. But M101’s most recent supernova, in 2011, came from a