Researchers discover a gigantic cloud of debris around a young star. It must have been caused by a violent collision.
Tucson – The universe is unimaginably large and full of violent processes – black holes collide or rupture stars, asteroids smash into planets and stars “fight” with each other. Our solar system was also created in a brutal process: a so-called accretion disk circled the sun, in which dust clumped and became planetesimals. These planetary progenitors attracted material through their gravity and grew larger, but also collided with each other and broke up again. Over time, the four rocky planets crystallized Mercury*, Venus, Earth and Mars* out.
Our solar system is now relatively calm, the planets reliably move their orbits around the sun, brutal collisions are a thing of the past. But elsewhere in the universe, such processes continue to occur, giving rise to new planetary systems. Researchers have now succeeded for the first time in observing this process of planet formation in a star that is 388 light-years away from Earth.
Universe: Debris cloud around star created by brutal collision
Star HD 166191 is 10 million years old—a baby compared to our 4.6 billion-year-old Sun—and at an age when planetesimals often form around a star. For this reason, the researchers observed the star with NASA’s “Spitzer” space telescope, which was active until 2020. Although planetesimals are too small to be observed with telescopes, the dust clouds that form during a collision could be seen by the Spitzer infrared telescope until it was deactivated.
And indeed: The researchers were not only able to observe the cloud of debris around the star, but even determine its size. Because the debris passed in front of the star and blocked the light it emitted for some time – a so-called transit, which researchers usually use to find exoplanets orbiting stars. The research team, led by University of Arizona’s Kate Su, initially thought the debris cloud was elongated, with an area at least three times that of the star. But Spitzer’s infrared data indicated otherwise: apparently only a small portion of the cloud passed in front of the star — the total amount of debris covering an area hundreds of times larger than that of the star.
Outer space: Two celestial bodies 500 kilometers across have collided
Using this data, the researchers were able to estimate how large the objects that had collided had to be to create the cloud of debris: they were probably two celestial bodies that were about the size of the asteroid Vesta (about 500 kilometers in diameter). Their collision generated enough heat and energy to vaporize some of the debris. At the same time, fragments collided with other small objects in orbit, creating a chain reaction that caused even more dust and debris. “By looking at dusty debris disks around young stars, we can essentially look back in time and see the processes that may have shaped our own solar system,” explains Kate Su, lead author of the study published in the Astrophysical Journal became.
Debris cloud observed in space: researchers are “eyewitnesses”
“If we learn more about the outcome of collisions in these systems, we can also get a better picture of how often rocky planets are formed around other stars,” says Su. “There is no substitute for being an eyewitness to an event,” adds her co-author George Rieke.
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Even if the “Spitzer” space telescope NASA* has long been history, Su’s team wants to continue observing the star and its orbit. The Stratospheric Observatory for Infrared Astronomy (SOFIA) is used for this purpose. Like many other astronomers, Kate Su’s team hopes for the “James Webb” space telescope from Nasa and Esa. The telescope was launched at the end of 2021 and is scheduled to send the first scientific data to Earth from summer 2022. Above all, Su and her team want to use “Webb” to investigate the mineralogy of the dust and thereby obtain new information about the physical conditions of such large collisions. (tab) *fr.de is an offer from IPPEN.MEDIA.
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