Huge Hydrogen Cloud Will Hit Milky Way

diewlasing points us to a story about a hydrogen cloud, eleven thousand light-years long, which will collide with the Milky Way in a devastating crossfire of shock waves and star formation...in 20-40 million years. Mark your calendars. At least it will give us something to watch while we're waiting for Andromeda to hit us in a few billion years. Hopefully, it will look at least this cool. "The detailed GBT study dramatically changed the astronomers' understanding of the cloud. Its velocity shows that it is falling into the Milky Way, not leaving it, and the new data show that it is plowing up Milky Way gas before it as it falls. 'Its shape, somewhat similar to that of a comet, indicates that it's already hitting gas in our Galaxy's outskirts,' Lockman said. 'It is also feeling a tidal force from the gravity of the Milky Way and may be in the process of being torn apart. Our Galaxy will get a rain of gas from this cloud, then in about 20 to 40 million years, the cloud's core will smash into the Milky Way's plane,' Lockman explained."

Comments

Re:I don't think it means what you think it means.

[maxwell demon]

Does anyone else have a problem with the word "smashing" to describe the contact of two bits of not-quite-vacuum passing through each other?

You mean, like a stone smashing into a window? You don't actually think the electrons or atomic nuclei of the stone actually come into contact with the electrons or atomic nuclei of the window, do you?

furlongs and donkey forthnights

[viking80]

Here is just some useful unit conversations:
suns = 2E30 kg
light year = 1E16 meters
So this cloud has a density of 28 H2 molecules per liter.
That is pretty good vacuum. Actually about a million times better vacuum than "deep vacuum" in outer space here in our solar system, which again is much better vacuum than what is achievable here on earth.

So this "collision" will be quite soft in terms of energy density: One feather landing on an area the size of the earth.