Researchers have discovered an ancient ultramassive galaxy in which stars suddenly ceased to be born. Scientists do not yet have a decent explanation for this phenomenon, although there are interesting versions.
The discovery is described in a scientific article published in the Astrophysical Journal.
The galaxy, designated XMM-2599, is very far from Earth. Astronomers saw it as it was 12 billion years ago, when the universe was only 1.8 billion years old.
The total mass of stars in this system is estimated at 300 billion suns. The formation of a galaxy so rich in luminaries in such ancient times is in itself an extraordinary event. Although modern models allow this, such objects should be extremely rare.
But her story is even more unusual. After analyzing the spectrum of the galaxy obtained with the Keck I optical telescope, the researchers found an amazing picture.
All XMM-2599 stars formed in one turbulent epoch, when the rate of star formation exceeded a thousand solar masses per year (for comparison: in the Milky Way today it is on the order of one solar mass per year). At that moment, it almost certainly looked like some very distant and dusty galaxies with intense star formation recently discovered in infrared telescopes.
After spending hundreds of millions of years in this mode, XMM-2599 … ceased to generate new stars altogether.
"During that era, very few galaxies stopped forming stars, and none of them is as massive as XMM-2599," states co-author Gillian Wilson of the University of California, Riverside.
Possible evolutionary path of the XMM-2599 galaxy.
Illustration by NRAO / AUI / NSF / B. Saxton; NASA / ESA / R. Foley; NASA / StScI.
The illustration from left to right shows the possible evolutionary path of the XMM-2599. From a massive and dusty galaxy with intense star formation to a star system of old red stars and then to the center of the brightest cluster of galaxies.
Such a sudden stop in star formation - in a sense, the death of the galaxy - has no explanation. Scientists can only guess what happened. It is possible that the cause of the catastrophe was the activity of the central black hole.
Since researchers do not know why the formation of new luminaries has stopped, it is difficult to say, and what this star system looks like today (we cannot see this, since the light emitted by it recently has not reached us and will not reach us very soon).
A separate question is what is happening around the XMM-2599. It is likely that due to its huge mass, it attracted the surrounding galaxies.
"Perhaps over the next 11.7 billion years of space history, XMM-2599 became a central member of one of the brightest and most massive galaxy clusters in the local universe," suggests co-author Michael Cooper of the University of California, Irvine.