In April, the Hubble Space Telescope will celebrate 30 years of exploring the space around us and sharing new discoveries, along with awe-inspiring views. And its latest subject is a galaxy thought to be the largest in the local universe: the so-called “Godzilla galaxy.”
The spiral galaxy, also known by its official name UGC 2885, is 2.5 times wider and contains ten times the stars as our own galaxy, the Milky Way.
But it’s also called a “gentle giant” by researchers because despite its massive size, the Godzilla galaxy is a quiet one. It appears tranquil, as though it’s been still for billions of years.
The galaxy is still forming stars, but only at half the rate of what is occurring in the Milky Way. It’s also not munching on other neighboring satellite galaxies, only “sipping” on nearby hydrogen to fuel its star birth. Even the supermassive black hole at its center is quiet because there’s no flow of gas to fuel it.
Found in the Perseus constellation, the galaxy was once measured by pioneering astronomer Vera Rubin, who determined that dark matter comprised much of its mass. An observatory was just named after Rubin, who died in 2016.
“My research was in large part inspired by Vera Rubin’s work in 1980 on the size of this galaxy,” said Benne Holwerda at the University of Louisville, Kentucky. “We consider this a commemorative image. The goal of citing Dr. Rubin in our observation was very much part of our original Hubble proposal.”
But trying to understand the galaxy’s size presents another puzzle.
“It’s as big as you can make a disk galaxy without hitting anything else in space,” Holwerda said. “It seems like it’s been puttering along, slowly growing.”
On its own, the galaxy has been undisturbed. No other galaxies are crashing into it and disturbing its shape. But it is possible that the galaxy once consumed smaller nearby galaxies so that it could grow.
Holwerda and his colleagues are counting star clusters found in a shell around it, known as the galaxy’s halo. If they find numerous clusters, that might present evidence that it gobbled up other galaxies over time.