Astronomers Just Caught the Tiniest Cannibal Galaxy in the Universe.

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When galaxies collide (like these two in the Crab nebula), stars with completely different compositions and velocities get stirred into one big cosmic stew. Researchers just found signs of the smallest-ever cosmic merger in the nearby Sextans dwarf galaxy.
Credit: ESA/Hubble & NASA, CC BY 4.0
▼ The sky is full of cannibals. Astronomers have long suspected that massive galaxies like the Milky Way become so big over time by swallowing up starsfrom their smaller cosmic neighbors. However, new research suggests that little galaxies also have big appetites.
According to a new paper published today (Oct. 11) in the journal Monthly Notices of the  Royal Astronomical Society, a pair of astronomers from Spain's Instituto de Astrofísica de Canarias and theUniversity of Lagunamay have detected the smallest known case of galactic cannibalismever observed — and it may have happened right down the cosmic street in one of the Milky Way's teensy satellite galaxies known as the Sextans dwarf spheroidal.
This neighborhood dwarf is old (about 12  billion years) and small, carrying about 100,000 times less solar mass than the Milky  Way. And according to the study authors, it may've only gotten that way after eating an even smaller neighbor.
In their new study, the researchers analyzed data from several previous sky surveys to compare the different colors, brightness and orbital speeds of the Sextans stars. They saw some interesting patterns emerge. For starters, Sextans appeared to be split between blue, metal-poor stars and red, metal-rich stars — and those two groups of stars were behaving differently. While the blue stars appeared organized into a somewhat orderly, round cluster, the red stars were scattered into a more irregular, elliptical orbit. (▪ ▪ ▪)

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