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.
As Cannan explained during his presentation, radio observations made with the Green Bank Telescope show that diffuse gas is lagging behind this high-velocity cloud, and it's also being ionized by ultraviolet light from stars in the galaxy's disk.
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.
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.
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 (HVC).
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 are distinct from a larger population of '
high-velocity clouds' that also sail outside the galaxy.
The fact is, many other "
high-velocity clouds" are also falling toward the galactic plane with no one noticing except specialists.
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.