If you take normal matter — something made of protons, neutrons and electrons — and compress it as far as it will go, something incredible happens. At high enough temperatures and densities, something requiring a tremendous amount of mass hundreds of thousands of times as great as planet Earth, nuclear fusion occurs, giving rise to […]

T The Milky Way enjoys a light drizzle throughout its galactic year. These cosmic raindrops are speedy clouds of mostly hydrogen gas that rain down onto our galaxy’s spiral disk. They fly through space at hundreds of kilometers per second (millions of miles per hour) and don’t rotate with the Milky Way. They’re appropriately named […]

Though hundreds of enormous high-velocity gas clouds whiz around the outskirts of our galaxy, this so-called “Smith Cloud” is unique because its trajectory is well known. Hubble Space Telescope astronomers are finding that the old adage, “What goes up, must come down” even applies to an immense cloud of hydrogen gas outside our Milky Way […]

Since astronomers discovered the Smith Cloud, a giant gas cloud plummeting toward the Milky Way, they have been unable to determine its composition, which would hold clues as to its origin. Astronomers have now determined that the cloud contains elements similar to our sun, which means the cloud originated in the Milky Way’s outer edges […]