Before Andromeda Crashes into The Milky Way Another Devastating Collision Could Sneak In First

The Whirlpool Galaxy is undergoing a minor merger. The two galaxies have roughly the same mass of the Milky Way and the LMC respectively. NASA, ESA, S. Beckwith (STScI) and the Hubble Heritage Team (STScI/AURA)

The Milky Way is going to collide with its sibling galaxy, Andromeda, around 4 billion years in the future. This merger will dramatically change both galaxies. But researchers think that before that happens another merger will take place, one with the Large Magellanic Cloud. Analysis of this potential collision is published in the Monthly Notices of the Royal Astronomical Society.

The Large Magellanic Cloud (LMC) is one of the biggest and closest of the dwarf galaxies that surround the Milky Way. It is located 163,000 light-years away and entered our neighborhood 1.5 billion years ago. People thought for a long time that it would either keep orbiting our galaxy or it might even escape it, as it moves very fast. But recently we discovered that it has a lot more dark matter than expected and its fate has shifted dramatically.

It is now expected that in about 2.4 billion years the LMC will hit the Milky Way. It won’t devastate the galaxy completely but it will make substantial changes. The team expects Sagittarius A*, the supermassive black hole at the center of the Milky Way, to get an influx of material. This will increase its mass significantly, by a factor of eight according to the study, and will likely lead to its awakening.

Sagittarius A* is quiescent and not actively feeding, but during a merger it will start actively gobbling up material falling into the core of the Milky Way. An active black hole produces powerful jets of material at temperatures higher than the center of the Sun. It also emits a lot of high-energy radiation. Such an active black hole could lead to the formation of gigantic hot winds of gas moving across the galaxy.

The team also expects that the halo of the Milky Way – the sphere of very spread out stars surrounding the galaxy – will accrue more members. In fact, possibly five times as many as there are currently. Mostly they will be stars from the LMC but even stars from the Milky Way might be thrown out into circumgalactic space.

The obvious question is will this affect the Solar System?

“There is a small chance that we might not escape unscathed from the collision between the two galaxies, which could knock us out of the Milky Way and into space,” lead author Dr Marius Cautun, from Durham University, said in a statement.

The team thinks that the scenario is unlikely as only a few percent of the stars located where the Sun is are at risk. And at the end of the day, we’ll all be dead by then so really we shouldn’t lose sleep over this.


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