Now that TRAPPIST-1 is the trendiest star system in the galaxy, astronomers and nerds alike are clamouring to learn more about it. We know that the seven-planet system contains three planets in the habitable zone, which means they could hypothetically support liquid water, and even life. We also know that the TRAPPIST-1 planets orbit around their ultracool dwarf star very closely, which could be good or bad for finding life, depending on who you ask. And now, we know a little more about the most distant planet in the bunch.
A new study published on May 22 in Nature Astronomy confirms TRAPPIST-1h's orbit. By using data from NASA's Kepler spacecraft, a team of researchers were able to ascertain the predictable frequency at which the innermost six planets orbit their star, a pattern called resonance. The planets' gravitational tugs on each other keeps the entire system stable.
"For every 2 orbits of the outermost planet, the next one in does 3 orbits, the next one 4..., 6, 9, 15, and 24," University of Toronto Scarborough astronomer Dan Tamayo previously told Gizmodo. "This is called a chain of resonances, and this is the longest one that has ever been discovered in a planetary system."
The team used this information to determine TRAPPIST-1h's orbital period, which is 19 days. At approximately 10 million km from its star, that places TRAPPIST-1h outside the habitable zone, so it's unlikely the chilly world could ever support life. According to NASA, the amount of energy the planet receives from its star is comparable to the sunlight hitting dwarf planet Ceres in the asteroid belt.
"We find that TRAPPIST-1 h has a radius of 0.752 R and an equilibrium temperature of 173 K," the researchers wrote. "We have also measured the rotational period of the star to be 3.3 days and detected a number of flares consistent with a low-activity, middle-aged, late M dwarf."
While TRAPPIST-1h might not be the flashiest planet in the system, it is the coolest — literally. And at this point, we'll take all the new details TRAPPIST-1 is willing to give us.