Could a Laser-like Beam of Light in Andromeda Predict Milky Way’s Fate?

Andromeda-xray-ir

A laser-like beam of light could predict the eventual collision of the Milky Way with the Andromeda Galaxy. Loránt Sjouwerman of the National Radio Astronomy Observatory in Socorro, New Mexico, and colleagues have glimpsed a bright, laser-like spot of microwave radiation, called a maser, in Andromeda that could help measure its sideways movement.


The speed at which Andromeda is moving towards the Milky Way can be determined from the Doppler shift of the light it emits. But the galaxy is too spread out for its subtle sideways motion in the sky to be detected. If it moves sideways fast enough it may miss colliding the Milky Way altogether.

The maser appears when interstellar methanol molecules get heated up by nearby stars.  The newly upgraded Very Large Array of telescopes in New Mexico is tracking the motion of this bright spot. But the team must first find other masers in Andromeda, to confirm that the maser motion reflects Andromeda's path overall.

"Measuring the proper motion of Andromeda is key to determining the fate of the Milky Way," says Mark Reid of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. "Such a measurement is best done with a compact, bright source such as a maser, but until now no maser strong enough for current telescopes to measure has been detected."

 It looks as though that in about three billion years, we'll need a new revised, Hitchhiker's Guide to Galaxy. According to recent research the Andromeda Galaxy may be destined to collide with the Milky Way.

Andromeda and the Milky Way are approaching one another at a speed of 100 to 140 kilometers per second (62–87 miles/sec). However, this does not mean it will definitely collide with the Milky Way, since the galaxy's tangential velocity is unknown. If they do collide, the two galaxies will likely merge to form a monster elliptical galaxy.

Andromeda is believed to be the largest galaxy of the Local Group of galaxies, which consists of the Andromeda Galaxy, the Milky Way Galaxy, and the Triangulum Galaxy, and about 30 other smaller galaxies. But scientists now believe that the Milky Way contains more dark matter and may be the most massive in the grouping.

However, recent observations by the Spitzer Space Telescope revealed that Andromeda contains one trillion stars, greatly exceeding the four billion stars in our own galaxy. The wide, detailed Spitzer Space Telescope view of Andromeda at the top of the page features infrared light from dust (red) and old stars (blue).

The blue dot in the center of the image at top of page is a "cool" million degree X-ray source where Andromeda's massive central object, with the mass of 30 million suns, is located, which most astronomers consider to be a super-massive black hole. Most of these are probably due to X-ray binary systems, in which a neutron star (or perhaps a stellar black hole) is in a close orbit around a normal star.

The Daily Galaxy via newscientist.com and Astrophysical Journal Letters

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