NASA’s Hubble Space Telescope has captured a stunning dance happening in the outer reaches of our Milky Way galaxy. The Large Magellanic Cloud, also called the LMC — a dwarf galaxy, believed to be 20 times the apparent diameter of the full Moon, has had the majority of its mass blown away due to coming in contact with the Milky Way, which is acting like a ‘hairdryer’. Scientists posit that LMC is not in orbit around our galaxy, but is just passing by. However, its closest approach to the much more massive Milky Way has led to most of its spherical halo of gas blown away.
“I like to think of the Milky Way as this giant hairdryer, and it’s blowing gas off the LMC as it comes into us,” said Andrew Fox of the European Space Agency in Baltimore, who was principal investigator on the observations.
“The Milky Way is pushing back so forcefully that the ram pressure has stripped off most of the original mass of the LMC’s halo. There’s only a little bit left, and it’s this small, compact leftover that we’re seeing now,” added Fox.
The ram pressure is a phenomenon in which the dense environment of the Milky Way pushes back against the incoming LMC and creates a wake of gas trailing the dwarf galaxy – like the tail of a comet. As the ram pressure pushes away much of the LMC’s halo, the gas slows down and eventually will rain into the Milky Way. However, since LMC has moved away from its closest approach to the Milky Way, scientists do not expect the whole halo will be lost.
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‘A survivor’
Despite losing its halo, LMC has survived and has enough life in it to develop new stars, according to the researchers.
“The LMC is a survivor. Even though it’s lost a lot of its gas, it’s got enough left to keep forming new stars. So new star-forming regions can still be created. A smaller galaxy wouldn’t have lasted – there would be no gas left, just a collection of aging red stars,” said Fox.
Notably, LMC is 10 per cent the mass of the Milky Way — making it much heftier than most dwarf galaxies. Had it been a little less massive, it wouldn’t have been able to hold onto itself gravitationally.
