Fastest stars in Milky Way escaped from Large Magellanic Cloud?


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Astronomers have proposed that the fastest stars in Milky Way actually escaped from the Large Magellanic Cloud (LMC), the largest nearby satellite dwarf galaxy.

The LMC is the largest and fastest of the dozens of dwarf galaxies in orbit around the Milky Way. It only has 10% of the mass of the Milky Way, and so the fastest runaways born in this dwarf galaxy can easily escape its gravity. The LMC flies around the Milky Way at 400 kilometres per second and, like a bullet fired from a moving train, the speed of these runaway stars is the velocity they were ejected at plus the velocity of the LMC. This is fast enough for them to be the hypervelocity stars. “These stars have just jumped from an express train – no wonder they’re fast,” said co-author Rob Izzard, a Rutherford fellow at the Institute of Astronomy. “This also explains their position in the sky, because the fastest runaways are ejected along the orbit of the LMC towards the constellations of Leo and Sextans.”

Their calculations predict how many hypervelocity stars should be detectable and where in the sky they should be. If right, the data from Gaia, soon to be released, should prove them right or wrong.

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2 comments

  • LocalFluff

    I’ve seen even people who are very optimistic about interstellar travel say that intergalactic travel is out of the question. Well, LMC is twice as far away as the furthest star in the Milky Way’s disk. And those guys take their fusion reactor with them.

    You know those star field zooms in many sci fi movies, pretending to show faster than speed of light travel? By extrapolating GAIA’s absurdly precise parallax measurements of stars’ positions and movements, they have calculated how it will look for real as the Sun travels through the galaxy at 200 m/s for the next five million years (so only 1/50 of a revolution).
    https://www.youtube.com/watch?v=Ag0qsSFJBAk

    I love GAIA. It is historic. Mapping our neighborhood, finally. I think it should be renamed after Tycho Brahe who were the first one to do it really seriously. Just decades before the telescope, but that was enough to give Johannis Kepler the data to, also very painstakingly, calculate the movements of Mars and discovered the fundamental law of physics that Isaac Newton a few decades later built upon which caused the industrialization.

    The movement of a single dot on the sky led to all of that.

  • LocalFluff

    I should add that each star ids indicated by an identical dot regardless of its real brightness. And those who suddenly move faster generally do so just because we come closer to them for a while.

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