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May 10 (UPI) -- The initial models built to simulate the TRAPPIST-1 system suggested the orbits of its planets should grow unstable within 1 million years of its existence, yielding planet-destroying collisions. So why do the system's eight Earth-sized planets -- three inside the ultra cool dwarf star's habitable zone -- still exist? Are the system's planets less than a million years old?
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"This may seem like a long time, but it's really just an astronomical blink of an eye," Dan Tamayo, a postdoctoral researcher at the University of Toronto, Scarborough's Center for Planetary Science, said in a news release. "It would be very lucky for us to discover TRAPPIST-1 right before it fell apart, so there must be a reason why it remains stable."
As new analysis showed, the system's stability and longevity can be explained by a phenomenon known as a "resonant chain." Researchers described the phenomenon in the Astrophysical Journal.
The orbital periods of TRAPPIST-1 planets form ratios of whole numbers.
"There's a rhythmic repeating pattern that ensures the system remains stable over a long period of time," explained Matt Russo, a post-doctoral researcher at the Canadian Institute for Theoretical Astrophysics.
In our own solar system, Neptune and Pluto form a resonant chain. In the TRAPPIST-1 system, all seven planets form a resonant chain.
Scientists liken the phenomenon to music -- in fact, they turned the phenomenon into music.
Resonance or harmonic frequencies are the reason why a pair or trio of notes sound pleasing when played together. Similarly, the TRAPPIST-1 planets orbit in harmony.
"Most planetary systems are like bands of amateur musicians playing their parts at different speeds," said Russo. "TRAPPIST-1 is different; it's a super-group with all seven members synchronizing their parts in nearly perfect time."
Researchers created a musical model to simulate the birth of the seven planets. As the planets coalesced out of the protoplanetary disk of gas and debris, they slowly settled into a resonant orbital pattern.
"This means that early on, each planet's orbit was tuned to make it harmonious with its neighbors, in the same way that instruments are tuned by a band before it begins to play," said Russo.
But even the most stable resonant chains are unlikely to be perfect.
"It's not that the system is doomed, it's that stable configurations are very exact," Tamayo said. "We can't measure all the orbital parameters well enough at the moment, so the simulated systems kept resulting in collisions because the setups weren't precise."
