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Orbital harmony limits the delayed arrival of water on the TRAPPIST-1 planet

A diagram showing what the TRAPPIST-1 system looks like from a vantage point near the planet TRAPPIST-1f (right). Credit: NASA / JPL-Caltech

Seven Earth-sized planets orbit the star TRAPPIST-1 in near-perfect harmony, and researchers in the United States and Europe have used that harmony to see how much physical abuse the planets have in their childhood. I decided if I could endure it.


“rear Rocky planet “This is called bombing or late accretion, and we care about it because these effects can be an important source of water,” said Sean Raymond, an astrophysicist at the University of Bordeaux, France. Volatile elements It nurtures life. ”

In the studies available online today Nature Astronomy, Raymond and colleagues funded by NASA at Rice University Wise planet The project and seven other agencies used computer models of the bombing phase of planet formation. TRAPPIST-1 Investigate its impact planet I would have been able to endure it without breaking the harmony.

Decoding the planetary impact history is difficult within us Solar system According to Raymond, it may seem like a desperate task in a light-year-old system.

“On Earth, we can measure certain types of elements and compare them to meteorites,” Raymond said. “That’s what we’re doing to try to figure out how many things have been driven into the Earth after it’s almost formed.”

However, these tools do not exist to study bombing of extrasolar planets.

“We will never get rocks from them,” he said. “We will never see craters on them. So what can we do? This is where TRAPPIST-1’s special orbital composition comes out. This is where we do this. It’s a kind of lever that can be pulled to limit. “

About 40 light-years away, TRAPPIST-1 is much smaller and cooler than our Sun. The planets are named alphabetically from b to h, in order of distance from the star. The time required to complete one orbit around a star (equivalent to one year on Earth) is 1.5 days on planet b and 19 days on planet h.Surprisingly, their The orbital period forms an almost perfect ratio, Resonant arrangement Reminiscent of harmonious notes.. For example, every 8 “years” on planet b, 5 times on planet c, 3 times on planet d, 2 times on planet e, and so on.

“We can’t say exactly how many of these planets collided, but this special resonance configuration can put an upper limit on it,” Raymond said. “I can say,’Nothing more is possible.’ And it turns out that the upper limit is actually quite small.

“We realized that after these planets were formed, they weren’t attacked by more than a tiny amount,” he said. “It’s a little cool. It’s interesting information when thinking about other aspects of the planet in the system.”

Planets grow in a protoplanetary disk of gas and dust around newly formed stars. These discs last only millions of years, and previous studies have shown that when young planets approach stars before the discs disappear, a resonant chain of planets like TRAPPIST-1 is formed. It is shown that. Computer models show that disks can resonate planets. According to Raymond, resonant chains like TRAPPIST-1 need to be set up before the disc disappears.

The conclusion is that the planet of TRAPPIST-1 was formed rapidly in about one-tenth of the time it took for the Earth to form, said Rice research co-author, astrophysicist and postdoctoral fellow at CLEVER Planets. Andre Izidoro said.

CLEVER Planets, led by research co-author Rajdeep Dasgupta, Professor Maurice Ewing of Earth Systems Science in Rice, is exploring ways to acquire the elements that planets need to sustain life.In a previous study, CLEVER Planets’ Dasgupta and colleagues showed a significant portion of the Earth. Volatile elements came from shock It formed the moon.

“If the planets form early and are too small, like the mass of the Moon or Mars, we can’t accrete large amounts of gas from the disc,” Dasgupta said. “Such planets also have much less opportunity to obtain life-critical volatile elements through slow bombing.”

Izidro said that was the case with the Earth, which acquired most of its mass relatively slowly, including about 1% from the post-collision impact that forms the Moon.

“We know that the Earth has had at least one huge impact after the gas (of the protoplanetary disk) has run out,” he said. “It was an event that formed the moon.

“In the case of the TRAPPIST-1 system, these earth mass planets were formed early,” he said. “Therefore, one of the potential differences when compared to the formation of the Earth is that there is an atmosphere of hydrogen from the beginning and has never experienced a huge impact in the later stages. This allows for internal evolution. Much can change. Planets, outgassing, volatile losses, and other things that affect habitability. “

Raymond said this week’s work will affect not only the study of other resonant planetary systems, but also the much more common exoplanet systems that were believed to have started as resonant systems.

“Super-Earth and Sub-Neptune are very abundant around other stars, and the main idea is that they could have moved inward during that gas disk stage and then had a late stage of collision. There is, “Raymond said. “But I think there was a stage where they were mostly (probably) a resonant chain structure like TRAPPIST-1 in the early stages when they were moving inward. They didn’t survive. It has become stable. On. “

Izidoro said that one of the major contributions to this research was NASA’s. James Webb Space Telescope, European Southern Observatory Extremely large telescope And other instruments allow astronomers to directly observe the atmosphere of exoplanets.

“Today we have some restrictions on the composition of these planets, such as the amount of water they can have,” Izidoro said of the planets formed during the resonating migration phase. .. “But there is a very large error bar.”

In the future, observations will better constrain the internal composition of extrasolar planets, and it can be very useful to know the history of late heavy bombardment of resonant planets.

“For example, if one of these planets has a large amount of water, for example a 20% mass fraction, water must have been incorporated into the planet early in the gas phase,” he said. “So you will have to understand what process can bring this water to this planet.”

Additional research co-authors include Emeline Bolmont and Martin Turbet of the University of Geneva, Caroline Dorn of the University of Zurich, Franck Selsis of the University of Bordeaux, Eric Agol of the University of Washington, and Patrick Barth of the University of St Andrews. , Ludmila Carone of the Maxplank Institute for Astronomy in Heidelberg, Germany, Michael Gillon of the University of Liege, Simon Grimm of the University of Bern.


Orbital flatness of the planetary system


For more information:
Sean Raymond, TRAPPIST-1 Late Accretion and Upper Limit of Water Supply in the Extrasolar Planetary System, Nature Astronomy (2021). DOI: 10.1038 / s41550-021-01518-6.. www.nature.com/articles/s41550-021-01518-6

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Rice University

Quote: Orbital harmony is the TRAPPIST-1 planet (2021) acquired from https: //phys.org/news/2021-11-orbital-harmony-limits-late-trappist-.html on November 25, 2021. Restrict late arrival of water to (November 25)

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Orbital harmony limits the delayed arrival of water on the TRAPPIST-1 planet

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