Fast, mysterious clouds swarm around our galaxy
The Milky Way’s forecast: mostly cloudy. But the origin of these cosmic clouds is unclear
Beyond the bright swirling arms of our Milky Way galaxy, something enormous, mysterious and shadowy barrels toward us. It’s called Smith’s Cloud. And it isn’t like any cloud you’ve seen before.
From head to tail, it extends more than 11,000 light-years. That’s roughly 2,500 times the distance from the sun to its closest stellar neighbor.
And Smith’s Cloud is fast. It covers 300 kilometers (nearly 200 miles) every second. That would be fast enough to zoom from Earth to the moon and back in less than an hour.
Instead of ice or water vapor, Smith’s Cloud is a cold gas made mostly of hydrogen.
Most peculiar, though, is where it’s going. Smith’s Cloud doesn’t move in the same direction, or at the same speed, as the stars that make up our galaxy.
