Scientists have used the “perfect harmony” of a distant planetary system to understand more about its past.
The star Trappist-1 is best known for being at the center of what NASA has dubbed the “holy grail” of a solar system remarkably similar to Earth. Since this discovery was first announced in 2017, astronomers have found more information about the system, including that it contains more planets and could host life.
However, scientists are still discovering more about these worlds, despite their vast difference from Earth. In new research, astronomers use the “near-harmony” of the orbits of the seven planets in the TRAPPIST-1 system to better understand their past.
The term harmony refers to the amazing clarity of the orbits of the various planets in the system. They are arranged in precise proportions, like the order of the harmonious musical notes: every eight years on one planet, five years pass the next, and they continue in this way in precise relationships.
The new research is allowing scientists to better understand the history of impacts on those planets, or what traumas they might have experienced when they were in their infancy. Doing so could help better determine whether planets contain water and other materials needed to start life.
“After the rocky planets formed, things bumped into them,” astrophysicist Shaun Raymond of Purdue University said in a statement. “It’s called bombardment, or delayed buildup, and it’s important in part, because these effects can be a major source of water and volatile elements that support life.”
The study of these impacts is very difficult on Earth, and this must be done by measuring certain elements and comparing them with the composition of meteorites. Doing so is impossible in a system like Trappist-1, which is 40 light-years away, so scientists have had to rely on more complex methods.
“We’re not going to get stones from them,” Raymond said. We’ll never see a hole in it. So what can we do? This is where Trappist-1’s special orbital configuration comes into play. It’s kind of a lever that we can pull to put limits on this.”
The researchers were able to estimate how much bombardment the planets could have done before taking them out of this fragile resonant harmony. This helps determine what might happen to those planets.
“We can’t say exactly how many objects have collided with any of these planets, but because of this particular resonant configuration, we can put an upper limit on it,” Raymond said. “We can say, ‘It couldn’t be more than this.’ And that upper bound turned out to be very small.
“We found that after these planets formed, they were not bombarded with more than a few things,” he explained. “That’s great. It’s interesting information when you think about other aspects of the planets of the system.”
The findings help scientists begin to tell the story of the Trappist-1 planets. They should have formed early and fast, about ten times faster than Earth, but they shouldn’t have been so bombarded, which helps to understand what might be inside these worlds and what their atmosphere might be.
However, scientists point out that there is a lot to learn about the system. Future checks on projects like the upcoming James Webb Space Telescope could help remove some unknowns from the new research.
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