Free Astronomy Magazine November-December 2022

36 NOVEMBER-DECEMBER 2022 ASTRO PUBLISHING tists think about galaxy mergers and deaths. As galaxies move through the Universe, they sometimes en- counter other galaxies. As they in- teract, each galaxy’s gravity pulls on the other. The ensuing tug-of-war flings gas and stars away from the galaxies, leaving behind streams of material known as tidal tails. And that’s just what scientists be- lieve happened to SDSS J1448+1010, but with a plot twist. The massive galaxy, which was born when the Universe was about half its current by ALMA Observatory Nicolás Lira Tug of war between merging galaxies W hile observing a newly- dormant galaxy using the Atacama Large Millime- ter/ submillimeter Array (ALMA) and the Hubble Space Telescope (HST), scientists discovered that it had stopped forming stars, not because it had used up all of its gas, but be- cause most of its star-forming fuel had been thrown out of the system as it merged with another galaxy. The result is a first for ALMA scien- tists. Moreover, if proven common, the results could change how scien- S cientists observing the newly- dormant galaxy SDSS J1448+1010 found that most of its star-forming fuel had been tossed out of the sys- tem as it merged with another galaxy. That gas is not forming new stars for the galaxy but remains nearby in new structures known as tidal tails. This artist’s conception shows the stream of gas and stars that were flung away from the mas- sive galaxy during its merger. [ALMA (ESO/NAOJ/NRAO), S.Dagnel- lo (NRAO/AUI/NSF)]