The star: It is much smaller than our sun and is referred to by scientists as an "ultra-cool dwarf" star. Its brightness makes it an ideal candidate for the Spitzer telescope, which was used by researchers, explained Sean Carey, manager of NASA's Spitzer Science Center in Pasadena, California.
The habitable zone of a star is the area around it in which a rocky planet is most likely to have liquid water. It can be different depending on the size of the star. In this case, the planets are closer to their star than Mercury is to the sun, according to NASA.
Scientists believe some planets in the habitable zones of their stars do not support life because of stellar eruptions. "Ultra-cool dwarfs are known to be very active when they are young," Gillon said. "This is the main concern about these potentially habitable planets. They (the planets' atmospheres) could have been eroded strongly by the star when it (the star) was young. Now it is quiet. ...So it is not very active. But maybe when it was young, the conditions were quite different. It will be by observation that we will really figure out the past of these planets and what happened during this very active and young phase."
How long it would take to travel to these planets: If it were possible to travel at light speed, the trip would take 39 years. But as that’s not an option, the trip would take longer, according to Lewis. “Something more like a jet plane would take far longer,” she says. “It would be more along the line of 44 million years.”
The significance: “With these discoveries, we’ve made a giant, accelerated leap forward in the search for habitable worlds and life on other worlds potentially speaking,” said Sara Seager, professor of planetary science and physics at Massachusetts Institute of Technology, Cambridge.
In addition, this solar system presents a chance to study planets orbiting cool, dim stars. In 2018, NASA plans to launch another observatory, the James Webb Space Telescope. “The reason the TRAPPIST planets are so significant is that they are accessible to observations with the James Webb Space Telescope. ... With the James Webb, we’ll be able to study the atmospheres,” Seager said.
Scientists may also learn about the planets’ greenhouse gas content, which will help them understand the surface temperatures, she added. “Are they indeed the right temperatures to support liquid water and life as we know it?”
The James Webb telescope may also help scientists search for gases that might be produced by life.
So how many habitable exoplanets have been found, including this discovery? The answer depends on who you ask and how you count them, Seager explained. "We would say that there are, let's say, a few dozen exoplanets that you might consider habitable," she said, "but the bottom line is that many of them may be a bit too hot or a bit too big. We really have to wait until we can see the atmospheres to know how hot or cold the planets really are. That's why the TRAPPIST planets are so relevant, because. .. unlike a lot of the other habitable zone planets, we can actually assess them in the near future."
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