The footprint of an asteroid collision captured 10 million light-years away

Marrakesh, Mar. 18 (Maroc-Actu) –

Data from NASA’s now-retired Spitzer Telescope has revealed the first glimpse of a cloud of debris from a collision between rocky bodies. passing in front of his star and blocking the light.

In a new study published in the Journal of Astrophysicsa group of astronomers led by Kate Su of the University of Arizona reports this new “transit” of asteroid-sized objects. about 10 million light-years away.

Combined with knowledge of the size and luminosity of the star, these observations allowed the researchers to directly determine the size of the cloud shortly after impact, to estimate the size of the colliding objects and to observe the speed at which the cloud dispersed.

“Nothing can replace being an eyewitness to an event,” he said. in a statement George Rieke, also from the University of Arizona and co-author of the new study. “All cases previously reported by Spitzer have not been resolved, with only theoretical assumptions about what the actual event and the debris cloud might have been. »

Beginning in 2015, a team led by Su began routine observations of a 10-million-year-old star called HD 166191. At this early stage in a star’s life, dust left behind by its formation s is agglomerated to form rocky bodies called planetesimals: the seeds of future planets. Once the gas that previously filled the space between these objects disperses, catastrophic collisions between them become common.

Anticipating that they might see evidence of one of these collisions around HD 166191, the team used Spitzer to make more than 100 observations of the system between 2015 and 2019. While the planetesimals are too small and too distant to be resolved with a telescope, their collisions produce large quantities. Spitzer dust detected infrared light, or wavelengths slightly longer than human eyes can see. Infrared is ideal for detecting dust, especially debris created by protoplanetary collisions.

In mid-2018, the space telescope saw system HD 166191 become noticeably brighter, suggesting an increase in debris production. Meanwhile, Spitzer also detected a cloud of debris blocking the star. Combination of transit observation by Spitzer with observations from ground-based telescopes, the team was able to deduce the size and shape of the debris cloud.

Their work suggests that the cloud was very elongated, with an estimated minimum surface area three times larger than that of the star. However, the amount of infrared glow observed by Spitzer suggests that only a small portion of the cloud passed in front of the star, and that debris from this event covered an area hundreds of times larger than that of the star.

To produce such a large cloud, the objects in the main collision had to be the size of dwarf Vesta in our solar system, an object 530 kilometers (330 miles) in diameter located in the main asteroid belt between Mars and Jupiter. The initial collision generated enough energy and heat to vaporize some of the material. It also set off a chain reaction of impacts between the fragments from the first collision and other small bodies in the system, which likely created a significant amount of the dust observed by Spitzer.

Over the next few months, the large dust cloud grew larger and became more translucent, indicating that dust and other debris was spreading rapidly through the young star system. In 2019, the cloud passing in front of the star was no longer visible, but the system contained twice as much dust as before Spitzer detected the cloud. According to the authors of the article, this information could help scientists test theories about the formation and growth of terrestrial planets.

“By observing the dusty debris disks around young stars, we can essentially go back in time and see the processes that may have shaped our own solar system,” Su said. “By learning the outcome of collisions in these systems, we can see the processes that may have shaped our own solar system,” he added, we can also get a better idea of ​​how often rocky planets form around other stars.« .

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