Category Archives: Universe

The Cartwheel Galaxy is the site of a galactic car crash. A smaller galaxy passed through a larger one and produced shock waves of gas and dust that turned into blue regions, where lots of stars are formed.

The Pinwheel Galaxy has a Milky Way look and at 170,000 light years across, pretty close to a Milky Way size. At 21 million light years away, it’s relatively close to us by galactic standards, and it’s conveniently staring at us face-on. In 2006, NASA and ESA stitched Hubble Telescope shots of the galaxy together into the most detailed galaxy image yet.

Our house. Imagine we scale down the Milky Way, making it 400 trillion times smaller until it’s the size of the United States, and we lay it out flat across the US. Now about 5,000 km or 3,000 miles across, it would take you two months to walk across our miniature Milky Way if you walked every waking hour of every day. If you were walking around, looking for stars, you wouldn’t actually see very much. The very biggest stars would be about the size of a pea. Our Sun would be so small, its diameter 1/20 of a human hair, you’d need to use a microscope to see it. And stars would be few and far between. If you were standing on our Sun, the closest star would be a football field away. Only from far away do galaxies look like busy places. When you’re inside of one, it’s almost all emptiness.

For a long time, astronomers estimated that the Milky Way stretched about 100,000 light years across, but that estimate has about doubled in recent years, and it may still be a work in progress.

Andromeda is our BFF galaxy. At 2.5 million light years away, you’d need to line up 12 Milky Ways in a row to stretch from us to Andromeda. If Andromeda were a bit brighter, it would look huge in our night sky, about 5 times bigger than the moon looks. The Universe is expanding, meaning almost all galaxies are moving farther away from all other galaxies — but Andromeda’s proximity to us means gravity is actually pulling it closer to us. About 4.5 billion years from now, the two galaxies will collide. That sounds stressful, but since galaxies are mostly empty space, it will actually be pretty uneventful for us if we’re still here.

All space stuff is far away. But NGC 4889, also known as Caldwell 35, is really, really, really far away: 300 million light years. That means the light from this galaxy that reaches Earth today is 300 million years old.

This largest known galaxy, IC 1101, contains 100 trillion stars, almost 1,000 times more than the Milky Way.

Virgo A, also called M87, has everything a self-respecting galaxy needs: a couple trillion stars, a supermassive black hole and a few thousand globular star clusters. Our own Milky Way with its few billion stars looks quaint in comparison.

Andromeda is 2.5 million light years away from us, about 12 Milky Way diameters. Since light takes 2.5 million years to pass between the two galaxies, if some super high—tech Andromeda alien is viewing us with a telescope right now, they’re seeing a bunch of Austrolopithecus walking around being unappealing.

At one billion years away, this cluster hides away the largest galaxy known, IC 1101, in an amount of dark matter equivalent to more than a hundred trillion Suns. If we were to take Abell 2029 as a representative sample of the Universe, 70 to 90% of it would be cold dark matter.

If the observable Universe is our world and the Milky Way is our house, the local group is our neighborhood. There are at least 80 galaxies in the neighborhood, but the Milky Way and Andromeda are the two biggest, with all the rest swarming around them like paparazzi.