Huge Hydrogen Cloud Will Hit Milky Way 220
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."
Shot in the Dark (Score:5, Interesting)
fuel for the fire (Score:2, Interesting)
Re:I don't think it means what you think it means. (Score:3, Interesting)
Re:I don't think it means what you think it means. (Score:3, Interesting)
Re:furlongs and donkey forthnights (Score:3, Interesting)
So this "collision" will be quite soft in terms of energy density: One feather landing on an area the size of the earth.
Right at first, yes. But there will be collisions, there will be gravity interaction.
There also is the fact that (1000000 suns x 2e30 kg = 2e37 kg) of mass coming in at 150 miles/second contain a *lot* of energy...
Some of that mass will combine with the gas in milkyway and push some areas over the threshold into collapsing and forming stars.
Hope this helps ;-)
Ulli
P.S.: I might have gotten confused with the numbers for the suns...
Re:Shot in the Dark (Score:3, Interesting)
Has this happened before - in "recent" times? (Score:5, Interesting)
I don't. (At least not until I find out the relative masses and densities of the gas cloud vs. both the sections of the Milky Way it's about to encounter and the interstellar-gas components of them.)
The cloud may be a very hard vacuum - only slightly softer than the intergalactic space around it. But at galactic scales it still amounts to something quite dense and massive, which will not pass through the interstellar gas and solar winds of our galaxy without interacting repeatedly - let alone through the magnetic fields of the galaxy and the stars and planets that compose it.
I'd expect it to coalesce with the galaxy. That much mass at that much relative velocity will dump enormous amounts of energy into compression and heat at the shock front (similar to the graduation of "falling pebble" to something akin to a bomb when the pebble is falling at cometary speed, or a nuclear bomb when the "pebble" is also a couple miles in diameter). The energy density might be small, but over half the sky the radiant temperature can add up. Over that much matter, even at near-vacuum densities, even fusion events could be non-trivial - especially since magnetic effects could produce concentrations.
In gas clouds I'd expect it, at a minimum, to kick off a round of star formation. Also to sweep the gas and dust out from between existing stars and their planetary systems (and fractionate it), as dense accumulations are accellerated little while gas and dust encounter something of comparable density.
Even if the density is so low that the above effects aren't significant for planetary systems like ours, the passage of the cloud (especially the shock front) would wreak non-trivial havoc on the solar wind and magnetosphere - and thus planetary radiation shielding. Because the solar wind -> radiation shielding -> water condensation nucleation -> cloud cover -> solar heat reflection connection seems to be a major contributor to (geologically) short-term planetary temperature changes, the arrival and passage of the gas cloud could have a major effect on climate. (Even if its impact on the magnetosphere doesn't "stir up" some change in activity on the solar surface or modify the sunspot cycle.)
Which brings up the questions:
- Have similar events occurred in the geologically "recent" past?
- If so, do they have any relation to ice ages and interglacial periods or to mass extinction events?
What next? A Cloud of Oxygen. (Score:3, Interesting)
If a cloud of oxygen of the same size were to come at the Milky Way from the opposite size, would the resulting cloud of water be enough to put out all of the stars?