As near as we can tell, our galaxy is a barred spiral with two bars of gas and stars extending out from a peanut-shaped central bulge. New models, published in the Monthly Notices of the Royal Astronomical Society and led by Junichi Baba, indicate that the rapid flow of gas along these bars drove star formation in the center, while gravitational interactions of existing stars with that bar tossed those stars into their odd, peanut-shape forming distribution. The simulation even offers observational tests: If this model is correct, stars in the peanut-y bulge should be older than the stars in the central area that are forming from gas flowing down the bar. The team hopes that analysis of data from the Gaia space telescope will allow this check to be made. When their results are known, we’ll bring them to you here on the Daily Space.

One of our joys and frustrations as researchers comes from the universe’s habit of finding multiple ways to accomplish the same thing. Did galaxies form in one large collapse of stuff into one large galaxy or through the build-up of lots of small stuff into a large galaxy? Honestly, it depends on the galaxy.

More Information

NAOJ press release

“Age distribution of stars in boxy/peanut/X-shaped bulges formed without bar buckling,” Junichi Baba, Daisuke Kawata, and Ralph Schönrich, 2022 March 8, Monthly Notices of the Royal Astronomical Society