Scientists: 7 Earth-size planets orbit dwarf star
Potential is there to harbor life
Not just one, but seven Earth-size planets that could potentially harbor life have been identified orbiting a tiny star not too far away, offering the first realistic opportunity to search for signs of alien life outside of the solar system.
The planets orbit a dwarf star named Trappist-1, about 40 light-years, or 235 trillion miles, from Earth. That is quite close in cosmic terms, and by happy accident, the orientation of the orbits of the seven planets allows them to be studied in great detail.
One or more of the exoplanets in this new system could be at the right temperature to be awash in oceans of water, astronomers said, based on the distance of the planets from the dwarf star.
“This is the first time so many planets of this kind are found around the same star,” Michael Gillon, an astronomer at the University of Liege in Belgium and the leader of an international team that has been observing Trappist-1, said during a telephone news conference organized by the journal Nature, which published the findings on Wednesday.
Scientists could even discover compelling evidence of aliens.
“I think that we have made a crucial step toward finding if there is life out there,” said Amaury H. M. J. Triaud, an astronomer at the University of Cambridge in England and another member of the research team. “Here, if life managed to thrive and releases gases similar to that we have on Earth, then we will know.”
Cool red dwarfs are the most common type of star, so astronomers are likely to find more planetary systems like that around Trappist-1 in the coming years.
“You can just imagine how many worlds are out there that have a shot to becoming a habitable ecosystem,” Thomas Zurbuchen, associate administrator of NASA’s science mission directorate, said during a NASA news conference on Wednesday. “Are we alone out there? We’re making a step forward with this — a leap forward, in fact — towards answering that question.”
Telescopes on the ground now and the Hubble Space Telescope in orbit will be able to discern some of the molecules in the planetary atmospheres. The James Webb Space Telescope, scheduled to launch next year, will peer at the infrared wavelengths of light, ideal for studying Trappist-1.
Comparisons among the different conditions of the seven will also be revealing.
“The Trappist-1 planets make the search for life in the galaxy imminent,” said Sara Seager, an astronomer at the Massachusetts Institute of Technology who was not a member of the research team. “For the first time ever, we don’t have to speculate. We just have to wait and then make very careful observations and see what is in the atmospheres of the Trappist planets.”
Even if the planets all turn out to be lifeless, scientists will have learned more about what keeps life from flourishing.
Astronomers always knew other stars must have planets, but until a couple of decades ago, they had not been able to spot them. Now they have confirmed more than 3,400, according to the Open Exoplanet Catalog. (An exoplanet is a planet around a star other than the sun.)
The authors of the Nature paper include Didier Queloz, one of the astronomers who discovered in 1995 the first known exoplanet around a sunlike star.
While the Trappist planets are about the size of Earth — give or take 25 percent in diameter — the star is very different from our sun.
Trappist-1, named after a robotic telescope in the Atacama Desert of Chile that the astronomers initially used to study the star, is what astronomers call an “ultracool dwarf,” with only onetwelfth the mass of the sun and a surface temperature of 4,150 degrees Fahrenheit, much cooler than the 10,000 degrees radiating from the sun. Trappist is a shortening of Transiting Planets and Planetesimals Small Telescope.