A group of scientists from around the world recently announced the discovery of seven earth-sized planets orbiting around a relatively nearby star.
TRAPPIST-1A is an ultra-cool dwarf star that is about 39 light years away from the Sun and about 12 times smaller than the Sun. It was named after the telescope used to discover it: the TRAnsiting Planets and PlanetesImals Small Telescope. It is the center of the TRAPPIST-1 planetary system.
The discovery of planets in the TRAPPIST-1 system is not new. The group of scientists, led by Michaёl Gillon, announced the discovery of three planets in the system in 2016.
They found the planets by examining the light that emitted from TRAPPIST-1A star, which faded at regular intervals. Because the light faded at regular intervals, Gillon and his team realized that something must pass in front of the star. Additional study of the light allowed them to discover the planets, as well as the planets’ orbits and size.
After continuing to examine the TRAPPIST-1 system, the astronomers found four additional planets orbiting the star. Each planet has a size and mass that is similar to Earth. Knowing the size and mass allows scientists to determine the density of each planet. Based on the small size and Earth-like mass, the planets are likely made of rock, not gas.
Scientists also examined the temperatures of each of the planets by considering their distance from the star. While TRAPPIST-1A is small, it is still very hot.
The three closest planets to the star are likely very hot, and the planet furthest away from the star is likely very cold. However, the three middle planets likely have temperatures that are capable of supporting liquid water. These three planets are in what is called the habitable zone.
In the future, the astronomers hope to examine the chemical content of each of the planet’s atmospheres. They also hope to discover some evidence of liquid water, which is a requirement for life. Brice-Olivier Demory, an astronomer who contributed to the planets’ discovery, discussed the probability of finding life on other planets. “This system is probably our best bet as of today,” he said.
The discovery of the planets has also prompted other scientists to continue the search for life elsewhere. Finding seven Earth-sized planets together suggests that additional groups of Earth-sized planets may exist elsewhere in the universe.
Next year, NASA will launch TESS, the Transiting Exoplanet Survey Satellite, which is set to discover more exoplanets orbiting other stars near us. The more planets found, the higher likelihood that life will be discovered.