New "Green Bean" Galaxies Discovered


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A new type of galaxy nicknamed "green bean galaxies" has been identified and they are some of the rarest objects in the known universe.

The nickname comes from the galaxies' appearance: they glow with intense light generated by the ionized gas surrounding a super-massive black hole. They also resemble "green pea galaxies," but are larger. Though most galaxies have a giant black hole at their center that causes the gas around it to glow, the entirety of green bean galaxies glow.

The green bean galaxy seen in the photo above has been named J2240 and lies in the constellation Aquarius. It is around 3.7 billion light-years from Earth. The object was discovered by Mischa Schirmer, an astronomer at the Gemini Observatory in Hawaii. He then asked the European Southern Observatory (ESO) for time with the Very Large Telescope (VLT) to verify his finding.

“ESO granted me special observing time at very short notice and just a few days after I submitted my proposal, this bizarre object was observed using the VLT,” said Schirmer. “Ten minutes after the data were taken in Chile, I had them on my computer in Germany. I soon refocused my research activities entirely as it became apparent that I had come across something really new.”

After categorizing the green bean galaxy, Schirmer and his colleagues found 16 more with similar properties. The astronomers estimate that the objects are so rare that there is, on average, only one found in a cube 1.3 billion light-years across.

The glowing regions of galaxies typically take up to 10% of the diameter of the galaxy, though exceptions, such as NGC 1277, are not unheard of. The glowing region of J2240, however, spans the entire galaxy with one of the biggest and brightest of such regions ever found.

“These glowing regions are fantastic probes to try to understand the physics of galaxies - it’s like sticking a medical thermometer into a galaxy far, far away,” said Schirmer. “Usually, these regions are neither very large nor very bright, and can only be seen well in nearby galaxies. However, in these newly discovered galaxies they are so huge and bright that they can be observed in great detail, despite their large distances.”

(Image courtesy CFHT/ESO/M. Schirmer)