New research on the exoplanets found orbiting the star TRAPPIST-1 have shed some light on the mysterious planets. Scientists at Bern University found that all seven planets are all rocky and contain 5 percent water.
This would make these planets the best studied outside of Earth's solar system.
Ultra-Cool Red Dwarf
A new study published in the journal Astronomy and Astrophysics shows new discoveries about the planets found in the TRAPPIST-1 system. All of the planets are mostly made of rock, and some have the potential to hold more water than Earth.
Discovery of the seven Earth-like planets orbiting TRAPPIST-1 was announced last year. Astronomers are hopeful that the planets could support life. TRAPPIST-1 is about 40 light years or 235 trillion miles away from Earth. TRAPPIST-1 is an ultra-cool red dwarf star when it was found it marked the first time so many planets were found around the same star.
To find out the planet's density researchers used transit timing variations - a method used by seeing a planet pass in front of a star, the dip in brightness determines its size. Because of the proximity of the planets to each other, they change the timing of each of the planet's years slightly.
Using this method astronomers were able to deduce the mass with less than 10 percent uncertainty. This helped scientists calculate the density of the planets. Calculations show that some of the planets have up to 5 percent of their mass in water, that's 250 times more than the oceans on Earth. Earth's water mass is only 0.02 percent.
TRAPPIST-1 is 9 percent the size of the Sun, the water on the surface of the planets depends on the amount of heat radiating from TRAPPIST-1. Heat determines what form of water will be present on the planets, those that are closer that gets the most heat may have vapor, and those further away may have ice on the surface. One of the planets has the possibility of having liquid water, TRAPPIST-1e is the rockiest planet.
"We now know more about TRAPPIST-1 than any other planetary system apart from our own," said Sean Carey, who authored the study. "The improved densities in our study dramatically refine our understanding of the nature of these mysterious worlds."
Since TRAPPIST-1 is much smaller than the Sun that means that it also radiates less heat. For the planets to receive as much heat as Earth they would need to be closer to the star.