Galaxies like our Milky Way are thought to be essentially 'factories' that use gravity to form new stars from molecular hydrogen gas. However, despite this, similar processes in similar galaxies suddenly stopped, and it became difficult for astronomers to explain why this is happening.
“The Milky Way turns gas into stars about the average mass of the sun each year,” said Gregory Rudnik, professor of physics and astronomy at the University of Kansas. 'The galaxy is filled with gas and we are constantly getting new gas from outside the galaxy. This gas enters the galaxy by gravity and forms stars, and some of the gas escapes from the galaxy. We see many galaxies that do not form stars. For some reason, they don't have much gas, so they can't create new stars. The question arises: why? Why are some galaxies not working as they should? Why do they have stars, but they no longer create new ones? '
The key to solving this puzzle may be a strange new class of galaxies about 6 billion light-years from Earth. They are undergoing active processes of forcible expulsion of their own gas. Digging deeper into this issue, Rudnik has teamed up with scientists from the United States for a new grant from the National Science Foundation to study these galaxies and find out why some galaxies no longer have the gas needed to form new stars. Part of the process is to challenge recent traditional ideas about ending star formation.
“One way humans have come up with an explanation for such events today is explosive gas removal through the active galactic nucleus,” Rudnik said. 'Every galaxy, including ours, has a supermassive black hole at its center. When gas enters a black hole, right before it enters the black hole, it becomes super-hot, and the energy it provides can actually blow the rest of the gas out of the galaxy. People love this explanation, as it is a mechanism that requires enough energy to force all the gas out of the galaxy. '
However, in 2007, a group of astronomers discovered a set of 'self-flowing' galaxies, in which star formation was interrupted for some inexplicable reason. Subsequently, Rudnik joined this team, which conducted a long-term study of these objects.
'In the course of our research, we were able to find a galaxy from which gas is bursting at a speed of thousands of kilometers per second (more than 3500 times faster than a jet plane), but there is absolutely no evidence that any gas is entering into a black hole, 'said the researcher. “So the question is whether this black hole process is needed or there are other ways to do it.”
After analyzing the best images of galaxies from the Hubble Space Telescope, Rudnik and his collaborators realized that gas could be expelled from galaxies by the purely concentrated light of stars in galaxies. That is, there is absolutely no need for additional energy from the gas falling into the black hole.
'The Milky Way has all of its stars and gas, spreading out over 100,000 light years, which means it takes 100,000 years of light to travel from one side to the other. These galaxies, which are as massive as the Milky Way, look huge and have an incredibly high concentration of stars. The idea that we started to develop is that perhaps these galaxies are so compact that all the starlight from all the stars in these galaxies is stuck in this small space, which is intense enough on its own to force gas out of the galaxies. '
To summarize, Rudnik said the idea is that stars emit light particles that will collide with gas particles and 'give them a little kick. The sum of many of these small jolts is enough to push all the gas out of the galaxy at an incredible rate. '
