Gigantic Gas Cloud on Collision Course With Our Galaxy

In case you didn’t know, a huge — like, on a galactic scale — cloud of gas is currently speeding toward our galaxy at 700,000 mph. It’s full of sulfur, over 11,000 light-years long and 2,500 light-years wide, contains as much mass as a million suns… and was very likely spat out of the Milky Way while T. rex was walking the Earth.

(The dinosaur, not the British rock band.)

And it’s a case of “what goes up must come down” — the cloud is on a ballistic trajectory after being blown out from our own galaxy, 70 million years ago.

Known about since 1963, the “Smith Cloud” — so-called after its discoverer Gail P. Smith — was first detected at the Dwingeloo Radio Observatory in the Netherlands. It’s since been repeatedly observed in radio wavelengths with the NRAO’s Green Bank Observatory in West Virginia and recently with the Hubble Space Telescope, which determined that it does in fact contain heavy elements like sulfur (contrary to some earlier analyses). This, along with its arcing trajectory, strongly indicates an origin from the star-enriched region along the outermost edges of our galaxy.

“The cloud is an example of how the galaxy is changing with time,” said Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland, leader of the research team. “It’s telling us that the Milky Way is a bubbling, very active place where gas can be thrown out of one part of the disk and then return back down into another.”

Diagram of the 100-million-year “boomerang” trajectory of the Smith Cloud.

The comet-shaped Smith Cloud contains no stars and so it’s not visible in optical wavelengths. But, if it were, it would span an area of night sky as large as the constellation Orion.

When the high-velocity cloud does impact the disc of the galaxy — in about another 30 million years or so — it will be on a different (albeit neighboring) arm than the one in which our solar system resides.

The collision will likely ignite an explosion of star formation around the impact site, perhaps with enough matter and energy to create two million new solar-mass stars.

Read more at Discovery News