NASA astronomers figure out the intricate dance of exoplanets in the TRAPPIST-1 system

The planets are locked in an orbital resonance, each gravitationally tugging the next planet, and keeping it in place.


In February 2017, NASA announced the exciting discovery of seven earth sized planets in orbit around an ultracool dwarf star forty light years away. Three of the exoplanets in the TRAPPIST-1 system were in the habitable zone of the star, with conditions suitable for liquid water to exist on the surface. All the seven planets were in a tight orbit around the star, closer to the host star than mercury is to the Sun. A person standing on the surface of one of these planets would be able to clearly discern details on the surface of the other six planets floating in the skies above.

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Now, further observations from the Kepler Space Telescope has allowed NASA astronomers to figure out what is going on. The raw data from Kepler was released to the scientific community, and astronomers around the world processed the observations in near real time to figure out what was going on with the TRAPPIST-1 system. The planets are locked in an orbital resonance, each gravitationally tugging the next planet, and keeping it in place. This is why the planets do not crash into each other.

There is no other planetary system with orbital resonance observed among seven planets. Four planets in orbital resonance have previously been observed in the Kepler-80 and Kepler-223 missions. The orbital relationships are believed to have formed in the early days of the system, which is believed to be between 3 to 8 billion years old. The study has been published in the scientific journal, Nature Astronomy. Here is an example of orbital resonance in our own Solar System, between Neptune, the dwarf-planet Pluto, and the trans-Neptunian object Orcus.

 

Rodrigo Luger, lead author of the study, said that "The resonant structure is no coincidence, and points to an interesting dynamical history in which the planets likely migrated inward in lock-step. This makes the system a great laboratory for planet formation and migration theories." One of the most interesting pieces of the puzzle, the orbital details of TRAPPIST-1h were confirmed by the new set of observations.

Trappist-1h. Image: Nasa.

Trappist-1h. Image: NASA.

TRAPPIST-1h was found to have an orbital period of 19 days. The orbit of the planet just skirts around the habitable zone of the star, and is likely to be too cold for liquid water to exist on the surface. The amount of energy received by TRAPPIST-1h is similar to the amount of energy received by Ceres, a dwarf planet in the asteroid belt of the Solar System, in orbit between Mars and Jupiter. Six possible orbits of TRAPPIST-1h was calculated even before the observations, and five of them were eliminated based on the available data. The remaining calculated orbit turned out to be the correct one.

What the surface of one of the planets could look like. ImagE: Nasa.

What the surface of one of the planets could look like. ImagE: Nasa.

The discovery of the system is a major step for the search of extra terrestrial life. The upcoming James Webb Space Telescope will observe the TRAPPIST-1 system to find signs of lifeforms.

 


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