The Mysterious Case of Green Galaxies

A new study in the evolution of galaxies revealed that the colors that galaxy have might shed some light in the age of its stars and its composition, helping researchers determine how galaxies evolved.

The new study, published in the Monthly Notices of Astronomical Society, suggests that galaxies can turn green in color during the critical stage in their evolution when they suddenly turn from blue into red.

Blue and red galaxies are common in the Universe. However, green galaxies can rarely be detected. Healthy galaxies emits blue glow when stars and planets are being born. On the other, when the stars and planets in a galaxy is beginning to age and die, their color turns into red.

Using state-of-the-art EAGLE simulations, researchers analyzed galaxies as they changed color, and investigated what processes caused them to change.

Researchers then discovered that green galaxies don't have an easy life.

"We typically find that smaller green galaxies are being violently tossed around by the gravitational pull of a massive neighbor, causing their gas supply to be stripped away," explained James Trayford, PhD student in the ICC at Durham University and lead author of the study, in a statement. "Meanwhile, bigger green galaxies may self-destruct as immense explosions triggered by super-massive black holes at their centers can blow dense gas away."

However, the researchers noted that green galaxy can survive its grueling fate it fresh supply of gas were to be absorbed from their surroundings. This process can revive the formation of stars and planets, potentially restoring the healthy blue light emission.

"By using simulations to study how galaxy colors change, we can speed up the process of galaxy evolution from the billions of years it takes in the real Universe to just a matter of days in a compute," said Trayford in a press release. "This means we don't just see galaxy colors frozen in time, we can watch them evolve. Another advantage is that we can remove unwanted factors that may change the colors we see, such as pesky dust clouds that can prevent light escaping from galaxies.