Astronomers discovered three planets orbiting in a possibly habitable zone of an ultra-cold dwarf star just 40 light years from Earth.
This discovery, Nature reported today, is the first evidence to support the hypothesis that these stars, having low mass and low temperature, should have planets the size of Earth or less, orbiting around them.
“Planets, the size of Venus or Earth, are currently the best place to search for life outside of our solar system,” said a team of researchers led by astronomer Michael Gillon from the University of Liege in Belgium.
“The systems around these tiny stars are the only place where we can detect life on Earth-sized exoplanets using modern technology,” said Gillon. “So, if we want to find life in the Universe, this is exactly where it stands to begin".
The planets were found almost by accident, during a test inspection of an ultra-cold dwarf star named TRAPPIST-1, which is in the Aquarius constellation, an international group of astronomers.
“We were preparing a more ambitious project that will begin this year using a large telescope located in Chile. It was a model designed to assess the feasibility of the project, but it worked so well that we found an amazing system around a nearby ultra-cold dwarf star, ”Gillon said. Planets can be habitable.
The star TRAPPIST-1 is the size of Jupiter, but a thousand times weaker than our Sun and shines in a much cooler infrared part of the light spectrum.
Three planets revolve around it, the orbits of two planets are within 1.1 and 1.5 percent of the distance between the Earth and the Sun and rotate around a star in one or two days.
“Since the star is very weak, small and cold, it emits far fewer photons, so there must be a temperature on these planets, something like Venus,” Gillon said.
The third planet found is farther from the star, but its rotation is worse described. According to the researchers, it makes a turn around the star from 4 to 72 days.
“This puts the third planet in the middle of the so-called Goldilocks Zone of possible habitability, which means that there may be a temperature range similar to Earth,” said Gillon.
While astronomical theory suggests that Earth-sized planets can rotate around ultra-cold, little massive stars, astronomer Simon O'Toole of the Australian Astronomical Observatory says that finding them will not be so easy.
“This is one of the most accurate parts of the project. They mainly look at the stars as much as they can, and then try to find movement, dim the brightness, and then try to find the frequency, ”said O'Toole, who did not take part in the study.
The researchers used a weak 60-cm telescope to observe the brightness of TRAPPIST-1 every 1-2 minutes for 245 hours for 62 nights. A small telescope detected a periodical darkening of the star, which was caused by the planets, passing in front of it and blocking part of the world.
The research team then used three larger telescopes in India, Chile and Hawaii to confirm that these are indeed planets orbiting a star.
“This is a phenomenal dimension ... it’s really very difficult, they have exceeded the capabilities of their equipment,” O'Toole said.
“The presence of such relatively large planets very close to such a small star suggests that they form in a completely different way than the formation of planets in our Solar System around our large Sun,” Gillon said.
The next stage involves a more detailed study of the composition and atmosphere of the planets using the 2-meter Himalayan telescope Chandr in India, and the James Webb Space Telescope, which is going to be launched in 2018.
“With this we can really explore the atmosphere of the planets, their composition, detect biological keys, whether there are traces of life, and we can also determine the masses of planets that are still unknown,” Gillon said.
