Seven planets, with mass similar to the Earth and orbiting around a dwarf star the size of Jupiter, just 39 light years from the Sun, have been spotted by scientists. The planets’ temperatures are low enough to make possible the presence of liquid water on their surface.
In May last, the scientists found three planets passing in front of star TRAPPIST-1. On further monitoring of the star from the ground and space, they found four more exoplanets orbiting it.
The results are being published on February 23 in Nature . Michaël Gillon from the Université de Liège, Belgium, is the first author of the paper.
In habitable zone of star
“This is the first time we have so many Earthlike planets found around a star. The star is low-mass and small,” Dr. Gillon said at a press briefing. “The seven planets could have some liquid water and maybe life. They are found in the habitable zone of the star. This is the first time we have found so many planets in the habitable zone of a star.”
The scientists have been able to make precise mass measurement of six of the seven planets. Though this is preliminary, they do indicate that the planets are terrestrial with liquid water. “The seven planets are suitable for detailed atmospheric study,” said Dr. Gillon. “The architecture suggests that they formed farther from the star and migrated towards it.”
“We can study the climate and chemical composition of the planets’ atmosphere,” Dr. Amaury H.M.J. Triaud from the Institute of Astronomy, Cambridge, who is one of the authors of the paper, said at the press briefing.
“We are first trying to rule out the presence of large hydrogen envelope to make sure that the planets are indeed Earthlike. This will be followed by a detailed study of climate and chemical composition to try and find out if there is life on these planets. If there is life on these planets we will know it in a decade,” he said.
Orbital periods
The four newly discovered planets orbit around the star every 4.04 days, 6.06 days, 8.1 days and 12.3 days respectively; the orbital period of two of the three planets discovered last year are 1.51 days and 2.42 days respectively.
Five planets have sizes similar to that of the Earth, while the remaining two are intermediate in size — between the Mars and the Earth. Based on the mass estimates, the six inner planets may have a rocky composition. The sixth planet has low density, suggesting a volatile rich composition. The volatile content could be either ice layer and/or atmosphere.
