An international team of astronomers has discovered three exoplanets that could possibly host alien life.
The trio of planets are circling an “ultra-cool” brown dwarf that’s located about 40 light years from Earth, in the constellation of Aquarius.
“Ultra-cool” dwarf stars are those that that are much cooler and redder than our Sun, and only slightly larger than Jupiter in size. Scientists say they’re quite common in the Milky Way.
Despite the relatively short distance between this star and Earth, the astronomers say that the star is too dim to be seen with the naked eye or even using a large amateur telescope.
The exoplanets were discovered with the Belgian TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST) at the European Southern Observatory’s La Silla facilities in Chile’s Atacama Desert.
The star is referred to as 2MASS J23062928-0502285, but now is also known as TRAPPIST-1. It has about .05% of the Sun’s brightness and has 8% the mass of the Sun.
The newly found exoplanets were described as being similar in size to Earth and were the first planets to be found orbiting such a small and faint star.
The team, led by Michaël Gillon of the Department of Astrophysics, Geophysics and Oceanography at Belgium’s University of Liège, have published their findings in the journal Nature.
Gillon says the reason why his team has been trying to detect Earth-like planets around the smallest and coolest stars is simple. “Systems around these tiny stars are the only places where we can detect life on an Earth-sized exoplanet with our current technology,” he said. So if we want to find life elsewhere in the Universe, this is where we should start to look.”
Astronomers conducting additional observations with larger telescopes have found that the one of the planets makes a complete orbit of its star every 1½ days, another takes about 2½ days and the third planet can take anywhere between 4½ to 73 days to circle its sun.
“With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun. The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the Solar System,” says Gillon.
The astronomers say that while the two most inner planets orbit closer to its star than the system’s habitable zone – the region around a star where planets can support liquid surface water – because TRAPPIST-1 isn’t nearly as powerful as our own Sun they still only receive between two to four times the amounts of radiation as Earth gets from our Sun.
The astronomers figure that the third, most outer planet, probably gets less radiation than Earth, but may still receive enough to lie within the star system’s habitable zone.
A more ambitious follow-up project to the TRAPPIST survey, called the Search for Planets EClipsing ULtra-cOOl Stars (SPECULOOS), is being planned at ESO’s Paranal Observatory.