Evidence of a giant impact on a nearby star system removing the atmosphere of a planet


These planetary collisions are common in young solar systems, but are not directly observed.

Younger planetary systems typically experience growing pains as children’s bodies collide and gradually form from larger planets. In our solar system, the Earth and the Moon are the products of this type of giant collision. Astronomers think such collisions should be common in early systems, but they are difficult to observe around other stars.

Now astronomers With, the National University of Ireland has found evidence of a massive impact on a nearby star system 95 light-years from Earth in Galway, Cambridge University and elsewhere. The star, named HD 172555, is about 23 million years old, and scientists suspect it may have traces of a recent collision of dust bears.

The team led by the Massachusetts Institute of Technology observed further evidence of a giant impact around the star. They determined that at least 200,000 years ago, a small Earth-sized planet might have had a collision with a small impact at 10 kilometers per second or more than 22,000 miles per hour.

Importantly, they discovered gas that could indicate that such a high-velocity impact could erupt over part of the planet’s atmosphere — an exciting phenomenon that illustrates the gas and dust surrounding the star. The results are out today natural >> adjective, indicates the first diagnosis of its kind.

We don’t have evidence in many systems,” said lead author Dagana Schneiderman, a graduate student in the Department of Earth, Atmospheric and Planetary Sciences at MIT. Now we have additional insight into these dynamics.

clear signal

Astronomers have maneuvered the star HD 172555 due to its unusual composition of dust. Observations made in recent years have shown that stardust contains high levels of unusual minerals, grains much better than astronomers would expect for a typical stellar debris disk.

“Because of these two factors, HD 172555 is this different system,” says Schneiderman.

She and her colleagues wondered what the gas might reveal about the history of the group’s offensive. They looked at the data they took Alma, Atacama Large Millimeter Array in Chile, which contains 66 radio telescopes, whose spacing can be adjusted to increase or decrease the resolution of their images. The team looked at data from the ALMA public archives, looking for signs of carbon monoxide around nearby stars.

“If people want to study gas in trash cans, carbon monoxide is generally very shiny, so it’s easy to find,” Schneiderman says. “So, we looked at the carbon monoxide data for HD 172555 because it’s an interesting system.”


Through careful reanalysis, the team was able to detect carbon monoxide around the star. When they measured its mass, they found that it contained about 20 percent carbon monoxide. Venus‘Atmosphere. They noticed that the gas circulated in great numbers and was surprisingly close to the star, about 10 AU or 10 times the distance between the Earth and the Sun.

“The presence of this nearby carbon monoxide requires some explanation,” Schneiderman says.

This is because carbon monoxide is generally susceptible to photosynthesis, a process in which a star’s photons are broken down and the molecule is destroyed. At close range, carbon monoxide is usually closest to the star. Therefore, the team experimented with different scenarios to illustrate the abundant and intimate view of the gas.

They quickly dismissed the situation in which the gas originated from the debris of the newly formed star. Like our Khyber Belt, they were also considered a spectacle where gas was expelled by several icy comets from a distant asteroid belt. But the data doesn’t fit that position either. The last scene the team looked at was the remnants of a giant gas impact.

“In all scenarios, this is the only thing that can explain all aspects of the data,” Schneiderman says. “In systems of this age, we would expect there to be large impacts, and we would expect larger impacts to be the most common. Temporal scales operate, age operates, morphology and synthesis constraints. In this context, the only reliable process that can produce carbon monoxide in this system has a significant impact.

The team estimates that the gas was released from a massive impact that occurred at least 200,000 years ago — as recently as the star may not have had time to completely destroy the gas. In terms of gas abundance, the impact involving two primordial planets similar to Earth could be enormous. Its impact was so great that it could cast a portion of the planet’s atmosphere into the gaseous form the team observed today.

“There is now an opportunity for future work outside of this organization,” Schneiderman says. “If we show that carbon monoxide and morphology in a space are compatible with each other, it provides a new way to search for giant impacts and understand how debris works.”

“What is particularly exciting about this work is that it demonstrates the importance of atmospheric loss through colossal impacts,” says Helck Schliching, professor of Earth, planetary and space sciences at the University of California, Los Angeles. This will eventually illuminate the planets’ atmospheres at their giant point of impact. “

Note: Tajana Schneiderman, Luca Mitra, Alan B. Jackson, Grant M.; Kennedy, Quentin Crowe, Sebastian Marino, Karen I. Oberg, Kate Yale. Sue, David J. Wellner and Mark C. White, Oct 20, 2021 Available here. natural >> adjective.
DOI: 10.1038 / s41586-021-03872-x

To some extent, this research was supported by the Alma Laboratory and the Simmons Foundation.


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