Leo Triplet

A three-way tug-of-war isn’t a common sight – unless you look toward the constellation Leo. Three galaxies there are tugging at one another, producing some spectacular results.

The galaxies are M65, M66, and NGC 3628 – the Leo Triplet. All three galaxies are about the same size as our home galaxy, the Milky Way. And each may resemble the Milky Way – a beautiful spiral with a long “bar” of stars across its middle.

The triplets are close enough together that the gravity of each galaxy exerts a strong pull on the others.

That’s given M66 a slightly “wonky” look. The galaxy’s core is a little off-center. Its spiral arms are loosely wound, and they aren’t symmetrical. And the arms are lined with knots of starbirth. Some of the stars in these regions are huge. Such a star burns out quickly, then explodes as a supernova. And since 1973, we’ve seen five supernovas in M66 – compared to zero in the Milky Way.

We see NGC 3628 edge-on, so it’s hard to know its exact shape. What we do see is a lane of dark dust sandwiched between brighter layers. We also see a “tail” that’s 300,000 light-years long – three times the size of the galaxy itself. It’s a ribbon of stars pulled out by the other galaxies in their ongoing “tug-of-war.”

Leo is in the east at nightfall. The triplet is to the upper right of Denebola, the star at the lion’s tail. It’s an easy target for a small telescope.

Script by Damond Benningfield