Space can be a violent place. Objects collide with each other, causing destruction or leading to the formation of larger celestial bodies. Scientists act as astronomical detectives and use the evidence left behind by these collisions to piece together what happened and learn about the objects involved.
Now, astronomers have had the chance to observe a huge star-sized cloud of debris from an impact just as it passed in front of a nearby star and blocked some of its light.
This temporary dimming of starlight, known as a transit, is often a method used to detect the presence of exoplanets around stars beyond our Solar System.
But this time, the observations revealed evidence of a collision between two celestial bodies likely the size of giant asteroids or mini-planets, the scientists said.
A team of astronomers began routinely observing HD 166191, a 10-million-year-old star similar to our Sun located 388 light-years away, in 2015. Astronomically speaking, it’s still a fairly young star — considering our sun is 4 .6 billion years.
At this age, planetesimals (rocky bodies of ice) usually form around stars. These orbiting clumps of dust left over from the formation of the star become rocky bodies, not unlike the asteroids left over from the formation of our Solar System.
Planetesimals found around other stars can collect material and increase in size, eventually turning into planets.
The gas, which is necessary for star formation, disperses over time among the planetesimals – and so these objects are increasingly at risk of colliding with each other.
The research team considered that they would likely be able to witness such an event if they continued observing HD 166191. Using the Spitzer Space Telescope, astronomers made more than 100 observations of the star between 2015 and early 2020.
Debris provide clues to planet formation
Planetesimals are too small to be seen by telescopes, but when they collide with each other, their dust clouds are large enough to be observable.
Based on the observable data, the researchers initially believe that the debris cloud became so elongated that it occupied an area about three times that of the star — and that’s the bare minimum estimate.
But Spitzer’s infrared observation saw only a small portion of the cloud pass in front of the star, while the total debris cloud spanned a region hundreds of times the size of the star.
To create such a massive cloud, the collision was likely the result of two objects similar in size to Vesta, a 530-kilometer-wide giant asteroid nearly the size of a dwarf planet in the main asteroid found in the belt between Mars and Jupiter in our System. Solar, uniting.
When these two celestial bodies collided, they created enough heat and energy to vaporize some of the debris. Fragments from this collision likely collided with other small objects orbiting HD 166191, contributing to the dust cloud witnessed by Spitzer.
“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,” said lead study author Kate Su, a research professor at the Observatory. Steward of the University of Arizona.
“By learning about the outcome of collisions in these systems, we can also get a better idea of ​​how often rocky planets form around other stars.”
First post-crash eyewitness observation
In mid-2018, HD 166191 grew in brightness, suggesting activity. Spitzer, which observed infrared light invisible to human eyes, detected a cloud of debris as it moved in front of the star.
This observation was compared with those obtained in visible light by ground-based telescopes, which revealed the cloud’s size and shape, as well as how quickly it evolved.
Ground-based telescopes had also witnessed a similar event about 142 days earlier, during a period when there was a gap in Spitzer observations.
“For the first time, we’ve captured the infrared glow of the dust and the nebulosity that the dust introduces as the cloud passes in front of the star,” said study co-author Everett Schlawin, research assistant professor at the University of Arizona’s Steward Observatory, in a affirmation.
Previous Spitzer attempts to observe collisions around young stars have not revealed much detail. The new observations were published last week in The Astrophysical Journal.
“There is no substitute for being an eyewitness to an event,” study co-author George Rieke, Regents professor of astronomy and planetary sciences at the University of Arizona’s Steward Observatory, said in a statement.
“All the cases previously reported by Spitzer have not been resolved, with only theoretical hypotheses about what the actual event and the debris cloud would look like.”
As the researchers continued their observations, they saw the debris cloud expand and become more translucent as the dust quickly dispersed.
The cloud was no longer visible in 2019. However, there was twice as much dust in the system compared to Spitzer’s observations before the collision.
The research team continues to monitor the star using other infrared observatories and anticipate further observations of these types of collisions using the newly launched James Webb Space Telescope.
Source: CNN Brasil
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