NASA's Kepler telescope reveals orbital details of TRAPPIST-1 system's outermost and least understood planet

Image credit: NASA

New Delhi: Earlier in February, scientists announced the discovery of a new solar system, the TRAPPIST-1, that has seven Earth-sized planets.

Scientists using the NASA's Spitzer Space Telescope in Chile and other ground-based telescopes discovered the planets in the TRAPPIST-1 system.

They said three of these exoplanets are firmly located in the habitable zone, the range of distances from a star where liquid water could pool on the surface of a rocky planet.

The discovery sets a new record for greatest number of habitable-zone planets found around a single star outside our solar system.

Now, astronomers studying NASA's Kepler Space Telescope identified a regular pattern in the orbits of the planets in the TRAPPIST-1 system, confirming suspected details about the orbit of its outermost and least understood planet, TRAPPIST-1h.

They said TRAPPIST-1, home to seven Earth-size planets, is only eight percent the mass of our sun, making it a cooler and less luminous star.

The system is located about 40 light-years away in the constellation of Aquarius and is estimated to be between 3 billion and 8 billion years old.

Using data from the Kepler spacecraft, astronomers from the University of Washington have confirmed that TRAPPIST-1h orbits its star every 19 days.

At six million miles from its cool dwarf star, TRAPPIST-1h is located beyond the outer edge of the habitable zone, and is likely too cold for life as we know it, says a NASA release.

The amount of energy (per unit area) planet h receives from its star is comparable to what the dwarf planet Ceres, located in the asteroid belt between Mars and Jupiter, gets from our sun.

“It’s incredibly exciting that we’re learning more about this planetary system elsewhere, especially about planet h, which we barely had information on until now,” said Thomas Zurbuchen, associate administrator of NASA’s Science Mission Directorate at Headquarters in Washington. “This finding is a great example of how the scientific community is unleashing the power of complementary data from our different missions to make such fascinating discoveries.”

"It really pleased me that TRAPPIST-1h was exactly where our team predicted it to be. It had me worried for a while that we were seeing what we wanted to see -- after all, things are almost never exactly what you expect them to be in this field," said Rodrigo Luger, doctoral student at UW in Seattle, and lead author of the study.

"Nature usually surprises us at every turn, but, in this case, theory and observation matched perfectly."

Using the prior Spitzer data, the team recognised a mathematical pattern in the frequency at which each of the six innermost planets orbits their star. This complex but predictable pattern, called an orbital resonance, occurs when planets exert a regular, periodic gravitational tug on each other as they orbit their star.

TRAPPIST-1's seven-planet chain of resonances established a record among known planetary systems, the previous holders being the systems Kepler-80 and Kepler-223, each with four resonant planets.

The TRAPPIST-1 system was first discovered in 2016 by the TRAPPIST collaboration, and was thought to have just three planets at that time. Additional planets were found with Spitzer and ground-based telescopes.

The study has been published in the journal Nature Astronomy.