The beginning of the end of our galaxy is a few billion years away. At this time, the bright disk of the Milky Way will be projected to crash into its closest neighbor, a spiral galaxy called Andromeda. The force of the collision will fuse the black holes at the centers of the galaxies, producing a luminous swirl of fast-moving ultra-gas known as a quasar.
Far from the galactic center, on a remote planet called Earth, the quasar will initially appear as a bright blue halo in the sky, so bright it will outshine the stars. But quasars are prone to cataclysmic flashes, which sweep away gas and dust, the materials that suns, worlds, and life are made of. Eventually, the galaxy will be emptied of all its material to make new stars.
This is how all galaxies die, at least according to theory. Until now, no one had captured a galaxy in its transition phase, after the formation of a quasar, but before it had lost all of its stellar building blocks.
Now, at the annual meeting of the American Astronomical Society in St. Louis, Missouri, Allison Kirkpatrick, assistant professor of physics and astronomy at the University of Kansas, has announced the discovery of “cold quasars”, galaxies with a large amount of cold gas that can still produce new stars despite having a quasar in the center , a revolutionary discovery that nullifies the assumptions about the maturation of galaxies and may represent a phase of the life cycle of each galaxy that until now has not He was known.
Cold quasars
It is an incredibly rare type of galaxy, radically changing our understanding of how galaxies die. These “cold quasars” would be incredibly bright and dying galaxies in the farthest reaches of the cosmos.
Quasars are basically super massive black holes surrounded by huge amounts of gas and dust, making them super bright, much brighter than a typical galaxy. They can be created when two galaxies merge and their black holes collide. For example, our galaxy, the Milky Way, is on a collision course with the neighboring Andromeda galaxy. This event, which will occur billions of years from now, will mark the end of the two galaxies and the creation of a quasar.
Gas and dust will begin to fall in the center of the quasar and will be expelled into space. Astronomers have speculated that this point is basically the end of a galaxy’s life, when it has lost the ability to form new stars and becomes “passive,” but Kirkpatrick and his team found that a small fraction of these cold quasars were still forming. new stars. The researchers examined the sky with X-ray and infrared telescopes and found 22 quasars at a distance of 6 to 12 billion light years away that show unusual signatures. They appeared to be in the final stages of life when viewed optically; however, they still emitted a bright far-infrared signature with lots of dust and cold gas.
During the press conference, Kirkpatrick posited that if we could get up close and see one of these quasars, it would be like a donut. In the center of the galaxy we would see a dead zone, where the quasar has expelled most of the gas and dust. Around the outside, we would find a star-forming region still abundant with gas and dust.
“These galaxies are rare because they are in a transition phase ,” Kirkpatrick said in a press release. “We have caught them just before star formation in the galaxy dies down, and this transition period should be very short.”
Incredibly strong winds would move through the galaxy, so this period would only last about 10 million years, the blink of an eye in universe timelines. These cold quasars are therefore incredibly rare, and spotting one is an important step in discovering how galaxies mature, live, and ultimately die.
Is this the final destination of our own galaxy?
Kirkpatrick thinks so. However, there is between 3 and 4 billion years to go for that to happen and we will have other problems by then, like an expanding sun ready to swallow the entire Earth.
The next step for the team of scientists will be to try to measure the speed at which gas and dust are expelled from the galaxy, which will allow Kirkpatrick to calculate how long galaxies spend in the “cold quasar” phase. Astrophysics will continue to search for more such objects, offering a glimpse into a poorly understood phase of galactic histories.
“Astronomy is a unique science because it is passive. We cannot see any processes in real time, so we are limited by the snapshots of different galaxies that we are trying to link. The more we can complete that image with snapshots, the better we can tell this story. And I think I found a new snapshot “, concludes the expert.
Referencia: “A New Population of Cold Quasars,” University of Kansas. “Astrophysicist announces her discovery that could rewrite story of how galaxies die.” ScienceDaily. ScienceDaily, 12 June 2019. University of Kansas.
