An international group of astronomers has found, through observations of the Hubble Space Telescope, that galaxy collisions, contrary to popular belief, generate new generations of stars, not destruction.
According to what NASA reported on Thursday, February 8, the Hubble Space Telescope focused on 12 interacting galaxies that have long tidal tails in the form of a string of pearls, consisting of gas, dust, and a large number of stars.
Hubble's remarkable resolution and ultraviolet sensitivity revealed 425 newborn star clusters along these tails, which look like strings of decorative lights.
Each star cluster contains up to a million newborn blue stars.
A star cluster is a group of stars bound together by gravity. Star clusters found in tidal tails have been known for decades. These tails occur when galaxies interact, as tidal forces pull in long streams of gas and dust.
A team of astronomers used a combination of new observations and archival data to obtain the ages and masses of star clusters in the tidal tails. They found that these clusters are very young, only 10 million years old. They appear to form at the same rate along tails extending thousands of light-years.
“It's a surprise to see so many small objects in the tails,” said study lead author Michael Rudrack of Randolph-Macon College in Ashland, Virginia. “This tells us a lot about the efficiency of cluster formation. Using tidal tails, new generations of stars will be built that might not have existed otherwise.” that".
The tails appear to take the galactic spiral arm and extend it into space. The outer part of the arm is pulled between a pair of interacting galaxies.
Before the mergers, galaxies were rich in dust clouds of molecular hydrogen, which may have remained dormant. But the clouds crowded together and collided with each other during the meeting. This compressed the hydrogen to the point that it triggered a firestorm of star birth.
String-of-pearl star formation may have been more common in the early universe when galaxies repeatedly collided with each other. These nearby galaxies observed by Hubble document what happened a long time ago, and are therefore laboratories for looking into the distant past.
Discovering a new source of the basic building blocks of planets
Stardust, also known as cosmic dust, forms the building blocks of rocky planets, like Earth and even life itself. Scientists have discovered a previously unknown source of this dust.
An international team of astronomers identified the source as a type of supernova interacting with gas from its surroundings.
Supernovas are huge explosions in space that occur during the final stages of the life of some stars.
The recent study found that Type Ia supernovae contribute significantly to the production of cosmic dust, which is surprising because the scientific community previously believed that Type II supernovae were the primary source of cosmic dust.
A Type Ia supernova emerges from a binary (or double) star system when a white dwarf star gains too much matter from its companion, triggering a thermonuclear explosion. While Type II supernovae occur when the core of a massive single star collapses at the end of its life cycle.
According to the study, SN2018evt, a Type Ia supernova that was discovered to generate an exceptional amount of cosmic dust, equivalent to about 1% of the mass of the Sun, challenges previous beliefs about the production of cosmic dust.
Scientists say that this supernova, which was monitored over the first three years after its explosion, and which is located in a spiral galaxy about 300 million light-years away, is one of the most dust-producing supernovas ever recorded.
Professor Haley Gomes, Head of the School of Physics and Astronomy at Cardiff University and one of those involved in the research, explained: “In this work, scientists around the world used multiple telescopes that can search in both visible and infrared light, to observe a rare type of astronomical event that occurs when "A very old dead star explodes with a slightly larger, younger companion star. The giant shock wave from the explosion collides with material previously ejected by one or both stars, and this collision creates a new batch of cosmic dust."
He continued: "Although rare, the amount of cosmic dust we discovered in the aftermath of this explosion is much greater than what was seen in other stellar events in such a short time."
Professor Gomez added: “Our new study on SN2018evt shows that just 1,041 days after the explosion, a huge amount of cosmic dust was formed, equivalent to 1% of the mass of our Sun. This provides an explanation for the abundance of dust that we see in these strange elliptical galaxies.”
While observing the supernova, scientists noticed that its light began to diminish in the wavelengths that our eyes can see, and then began to glow more brightly in infrared light, a clear sign of the formation of dust.
Understanding cosmic dust production can lead to an understanding of the materials that make up rocky planets and the origins of life, as well as the general structure and evolution of the universe.
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