His research topic, a massive intergalactic gas cloud known as Complex A, is destined to crash into the Milky Way's disk as a high-velocity cloud
, triggering a burst of star formation (S&T: Jan.
Astronomers believe that without this protective shell, the high-velocity cloud
(HVC) known as the Smith Cloud would have disintegrated long ago when it first collided with the disk of our Galaxy.
Afterward, a slower-moving yet still high-velocity cloud
of dust, debris and molten material swept over North America, ``adding more insult,'' Schultz said.
Astronomers had assumed the body was a so-called high-velocity cloud
, a type of fast-moving mass of atomic hydrogen commonly found far from the galaxy.
Benjamin (University of Wisconsin, Whitewater) says Smith's Cloud is the closest known high-velocity cloud
to the Milky Way's disk.
The Andromeda finding strengthens the case that the high-velocity clouds
surrounding the Milky Way include remnant gas from the galaxy's origin, says Thilker.
Instead, astronomers suspect that some of them were created by high-velocity clouds
Also known as Smith's Cloud, it's one of thousands of high-velocity clouds
of hydrogen gas flying around the outskirts of our Galaxy.
The Smith Cloud is unique among high-velocity clouds
because it is so clearly interacting with and merging with the Milky Way," said Felix J.
The halo clouds move in tandem with the rotating Galaxy, while the high-velocity clouds
scud along much faster.
Judging from models of structure formation in which small objects in the cosmos coalesce to form larger ones, "there ought to be clouds of dark matter and gas falling into our galaxy, and that's what we believe these high-velocity clouds
are," he says.
The origin of these so-called high-velocity clouds
had been uncertain since they were first detected by Dutch astronomer Jan Oort in 1961.