(ORDO NEWS) — Trying to find out why in some galaxies the formation of new stars has completely stopped, astronomers suddenly discovered a very curious factor.
The Milky Way galaxy is not very active compared to other galaxies. Each year it produces about three or four Suns of new stars along its entire length, and stars of all ages meet in it.
But in space there are also quieter galaxies – elliptical, for which star formation in most cases has long ceased.
There are very few (or no) stars in these galaxies younger than a certain age, suggesting that at some point much of the star formation suddenly stopped, leaving the galaxy slowly fading over eons, star by star.
Exactly how star formation is “turned off” remains a mystery, but scientists believe it has something to do with the supermassive black holes found at the center of each such galaxy.
An international team of astronomers led by Kei Ito of the SOKENDAI Advanced Research University in Japan looked into the early universe to find out if this is the case.
Using some of the world’s most powerful telescopes, they collected data on various wavelengths of light to identify galaxies whose light traveled 9.5 to 12.5 billion years across the chasm of space-time.
How black holes are choking their own galaxies
We all know that nothing can come from beyond the event horizon of a black hole, but the space around it is another matter entirely.
Material revolves around a black hole like water around a drain; gravity and friction generate intense radiation that permeates the universe.
Another form of feedback takes the form of jets erupting from the black hole’s polar regions. Matter beyond the event horizon is thought to be accelerated along the black hole’s external magnetic field and ejected from the poles in powerful, focused jets of plasma moving at a significant percentage of the speed of light.
Finally, active supermassive black holes generate strong winds that rush into their galaxies. All three forms of feedback radiation, jets, and wind are thought to heat up and repel the cold molecular gas needed to form young stars.
At such vast distances, galaxies are much harder to see; they are very small and very weak, from our point of view here and now.
So the researchers had to “stack” the galaxies together to highlight radio and X-ray light, which are telltale signs of an active supermassive black hole all those billions of years ago.
And it worked; the team found that the “excessive” X-ray and radio signal is too strong to be explained only by stars in galaxies where there is little to no star formation.
The best explanation for this signal is an active supermassive black hole. Moreover, in galaxies with ongoing star formation, the signal was not so pronounced.
The researchers concluded that this suggests that it is very likely that an active supermassive black hole plays a role in the sudden death of these mysterious ghost galaxies.
Future research could help shed light on the detailed physics of this enigmatic process, they said.
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