MICHELE NORRIS, host:
We're awfully early with this next one. In about 20 million years or so, astronomers are predicting that a giant cloud of gas will collide with our home galaxy, the Milky Way.
NPR's Richard Harris has more on this galactic surprise.
RICHARD HARRIS: In 1963, a young astronomer in Holland named Gail Smith discovered a giant cloud of hydrogen gas lurking just beyond our galaxy. She went on to do other things and the Smith Cloud was more or less forgotten. But recently, Jay Lockman at the National Radio Astronomy Observatory in Green Bank, West Virginia, decided to take a look. He got interested, obsessively interested. Using a radio telescope, he mapped 40,000 locations in the Smith Cloud in order to cobble together a picture of what the Smith Cloud looks like.
Dr. JAY LOCKMAN (Research Scientist, National Radio Astronomy Observatory ): It really looks like a comet. It has a very condensed head and these trails of gas billowing out behind it.
HARRIS: Lockman unveiled the image today at the American Astronomical Society meeting in Austin, Texas.
Dr. LOCKMAN: Just one look at the image and you know it's falling into the Milky Way, there's no question about which way it's going.
HARRIS: And it's huge. If you could actually see that cloud of gas in the sky, it would appear to be much bigger than the moon. When it gets here, blam. Lockman says it's going to collide with other gas clouds that, at the moment, are sitting rather peacefully out in the nether reaches of the galaxy.
Dr. LOCKMAN: And new stars might pop out of them kind of like raindrops condensing out of a cloud. So the result could actually be quite spectacular.
HARRIS: But don't bother to set up your lawn chair just yet. We still have a little bit of a wait for it to collide with the Milky Way. Hard to say if it will slow down from its current speed.
Dr. LOCKMAN: But if it's in freefall, then in about 20 million years or so, it's going to hit. It's very close right now as distances go.
HARRIS: But if you're worried about your progeny, 20 millions years hence, relax. Looks like the Smith Cloud is not going to hit our particular arm of the Milky Way.
Dr. LOCKMAN: It's going to be about a quarter of the way around the Milky Way from the sun when it hits.
HARRIS: So you're saying we don't have to send Bruce Willis out there to stop it or anything?
Dr. LOCKMAN: No, no, no. But I tell you, somewhere out, around a quarter of the way around the galaxy, there is some astronomer who is probably just now looking up and saying, oh, wow, when is this thing coming toward us?
HARRIS: There is a more local astronomer also interested in this news. And that would be Gail Smith, now Gail Beeger-Smith, who discovered the cloud decades ago. She settled in Holland and is no longer an astronomer, but she's thrilled to hear that her cloud turned out to be exciting.
Ms. GAIL BEEGER-SMITH (Retired Astronomer; Discoverer, Smith Cloud): Well, if it's going to cause a catastrophe, I don't know, maybe I shouldn't be so happy about it. But of course it is exciting.
HARRIS: Yeah. In 20 million years, who's going to blame you.
Ms. BEEGER-SMITH: Yeah, well, I guess so.
HARRIS: Richard Harris, NPR News.