The TRAPPIST-1 solar system has seven Earth-size planets, at least three of which might be potentially habitable. However, astronomers found that the system was not bombarded by rocks like early Earth.

According to Live Science, TRAPPIST-1 was located some 40 light-years away from the sun in the constellation Aquarius. It is a red dwarf, the type that is the most common in the Milky Way. 

A new study suggests that the way the TRAPPIST-1 planets orbit might reveal clues about their evolution and if space rocks frequently smashed into them over the years. 

The planets lock in a multi resonant orbital configuration, which has enabled precise measurements of the planets’ masses and constrained their compositions.

The seven exoplanets orbit in resonance, which means that although each planet takes a different amount of time to complete one orbit, pairs regularly meet again at the same starting point. 

In the new research, scientists argue that this strangely regular orbital dance would not be possible if those planets were subjected to too much hammering by space rocks after their birth in the protoplanetary disk that surrounded TRAPPIST-1 star some 7 billion years ago. 

“We figured out that after these planets formed, they weren’t bombarded by more than a very small amount of stuff,” astrophysicist Sean Raymond of the University of Bordeaux in France and the lead author of the study said in a statement.

“That’s kind of cool. It’s interesting information when we’re thinking about other aspects of the planets in the system,” Raymond added.

A group of U.S. and European researchers simulated the evolution of the TRAPPIST-1 system on a computer as they tried to find out how many rocks could hit those planets before their synchronized orbital dance would get disrupted.

“We can’t say exactly how much stuff bashed into any of these planets, but because of this special resonant configuration, we can put an upper limit on it,” Raymond said. “We can say, ‘It can’t have been more than this.’ And it turns out that that upper limit is actually fairly small.”

The model suggests that planets in the TRAPPIST-1 system must have formed very early and very fast, the scientists said in the statement. 

According to scientists, understanding the intensity of the bombardment by space rocks in the early stages of a planet’s life may help understand the planet’s chemical composition.

In the case of Earth, many chemical elements are believed to have been introduced by impacting comets, asteroids, and meteorites.

Scientists currently know very little about the chemical composition of the TRAPPIST-1 system.

“We have some constraints today on the composition of these planets, like how much water they can have,” said astrophysicist Andre Izidoro at Rice University in Houston and a co-author of the paper.

However, these planets may have already formed from more hydrogen and naturally have more water than Earth. 

“For instance, if one of these planets has a lot of water, let’s say 20% mass fraction, the water must have been incorporated into the planets early, during the gaseous phase,” Izidoro said. “So you will have to understand what kind of process could bring this water to this planet.”

Scientists are now waiting for new observatories such as the James Webb Space Telescope and the Extremely Large Telescope, scheduled to begin operations in 2022 and 2024, respectively, to learn how the various pieces of the puzzle work fit into place. 

At the end of this puzzle, scientists will hopefully know whether there might be life on any of those distant Earths. 

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