The Milky Way's impending galactic collision is already birthing new stars

The Milky Way's impending galactic collision is already birthing new stars
A newfound cluster of young stars (blue star) sits on the periphery of the Milky Way. These stars probably formed from material originating from neighboring dwarf galaxies called the Magellanic Clouds. Credit: D. Nidever; NASA

The outskirts of the Milky Way are home to the galaxy's oldest stars. But astronomers have spotted something unexpected in this celestial retirement community: a flock of young stars.

More surprising still, spectral analysis suggests that the infant have an extragalactic origin. The stars seemingly formed not from material from the Milky Way, but from two nearby known as the Magellanic Clouds. Those are on a collision course with our own. The discovery suggests that a stream of gas extending from the galaxies is about half as far from crashing into the Milky Way as previously thought.

"This is a puny of stars—less than a few thousand in total—but it has big implications beyond its local area of the Milky Way," says primary discoverer Adrian Price-Whelan, a research fellow at the Flatiron Institute's Center for Computational Astrophysics in New York City. (The cluster also bears his name: Price-Whelan 1.)

The newfound stars could reveal new insights into the Milky Way's history; they might, for example, tell if the Magellanic Clouds collided with our galaxy in the past.


The Milky Way's impending galactic collision is already birthing new stars
Astronomers have spotted a group of young stars (blue) on the outskirts of the Milky Way. The scientists propose that these stars formed from material from two dwarf galaxies known as the Magellanic Clouds. Credit: A. Price-Whelan



The newfound cluster is relatively young at 117 million years old and is on the far outskirts of the Milky Way. "It's really, really far away," Price-Whelan says. "It's further than any known young stars in the Milky Way, which are typically in the disk. So right away, I was like, 'Holy smokes, what is this?'"


A visualization of the position of the newfound Price-Whelan 1 star cluster (blue points) relative to the Milky Way (white points). The star cluster probably formed from material from the Large and Small Magellanic Clouds (purple points). The vertical green line shows the location of the Sun. Credit: A. Price-Whelan; Simulation by J. Hunt

The researchers propose that the cluster formed as gas from the Magellanic Stream passed through the gases surrounding the Milky Way. This pass-through created a that compressed the Magellanic Stream gas. This drag, along with tidal forces from the Milky Way's gravitational tug, condensed the gas enough to trigger star formation. Over time, the stars zoomed ahead of the surrounding gas and joined the Milky Way.

The stars' presence presents a unique opportunity. Gauging the distance of gas from Earth is tricky and imprecise, so astronomers weren't sure how far the Magellanic Stream was from reaching the Milky Way. The distance of stars, on the other hand, is comparatively trivial. Using the current positions and movements of stars in the cluster, the researchers predict that the edge of the Magellanic Stream is 90,000 light-years away from the Milky Way. That's roughly half the distance previously predicted.

"If the Magellanic Stream is closer, especially the leading arm closest to our galaxy, then it's likely to be incorporated into the Milky Way sooner than the current model predicts," Nidever says. "Eventually, that gas will turn into new stars in the Milky Way's disk. Right now, our galaxy is using up gas faster than its being replenished. This extra gas coming in will help us replenish that reservoir and make sure that our galaxy continues to thrive and form new stars."

The updated distance to the Magellanic Stream will improve models of where the Magellanic Clouds have been and where they're going, Price-Whelan says. The improved numbers could even settle a debate over whether the Magellanic Clouds have crossed through the Milky Way before. Finding an answer to that question will help astronomers better understand the history and properties of our galaxy.

Explore further

Magellanic clouds duo may have been a trio

More information: Adrian M. Price-Whelan et al, Discovery of a Disrupting Open Cluster Far into the Milky Way Halo: A Recent Star Formation Event in the Leading Arm of the Magellanic Stream?, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab4bdd

David L. Nidever et al. Spectroscopy of the Young Stellar Association Price-Whelan 1: Origin in the Magellanic Leading Arm and Constraints on the Milky Way Hot Halo, The Astrophysical Journal (2019). DOI: 10.3847/1538-4357/ab52fc

Journal information: Astrophysical Journal

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Citation: The Milky Way's impending galactic collision is already birthing new stars (2020, January 8) retrieved 20 June 2021 from https://phys.org/news/2020-01-milky-impending-galactic-collision-birthing.html

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