A few weeks ago astronomers told us that our Milky Way galaxy is part of a much bigger cosmic structure: the Laniakea Galactic Supercluster. But if this is the block the Milky Way plays on, then the Milky Way is the bully of the block (or one of them, at least). As Ian O'Neill says for Discovery News, the Milky Way has a tendency to steal from the smaller kids: “our Milky Way galaxy has been ransacking nearby dwarf galaxies, stealing their precious star-forming gases.”
As Smart News has written before, the life of a galaxy isn't an easy one. It's an existence full of explosions and collisions with other galaxies, of supernova and supermassive black holes that leave it twisted and deformed.
There are a bevy of dwarf galaxies that surround the Milky Way, writes O'Neill, but most of them are low on hydrogen gas, the stuff that makes new stars.
Surrounding our galaxy is a halo of hot hydrogen plasma and, as the dwarf spheroids orbit the Milky way at speeds in excess of a million miles per hour, the neutral hydrogen gas is stripped from within the dwarfs. Therefore, there appears to be a “danger zone” surrounding the Milky Way where neutral hydrogen is stripped away, shutting down star formation in these dwarf galaxies. Beyond 1,000 light-years, however, dwarf galaxies’ neutral hydrogen is retained and fuels star formation.
But if the Milky Way is a bully, stealing hydrogen from nearby galaxies, it's certainly not the biggest bully around. The biggest bully we've ever seen, says Elizabeth Howell for Universe Today, is a black hole 3.9 billion light-years away. That black hole is hoarding so much hydrogen gas that it's “stopping trillions of stars from coming to be,” says Howell.