#NASA announced this afternoon that it had moved a little farther in the search for alien life with the discovery of seven promising exoplanets in the TRAPPIST-1 system. This is the first time ever that seven Earth-size planets have been found orbiting the same star.

What is especially encouraging to NASA scientists is the fact that the planets orbit the star within the so-called habitable zone -- meaning an area where temperatures were likely to be found between 0 and 100 degrees Celsius and therefore water could exist on #Exoplanets with rocky compositions like that of Earth. Initial calculations of planetary mass indicate that the TRAPPIST-1 planets are likely to be rocky.

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"Answering the question 'are we alone' is a top science priority and finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal." The associate administrator of the NASA Science Mission Directorate, Thomas Zurbuchen, made the statement in a media release.

Our sister solar system

The planets in the TRAPPIST-1 system were discovered a few at a time as a team effort by the NASA Spitzer Space Telescope, in conjunction with a number of ground-based telescope systems, including the TRAnsiting Planets and PlanetesImals Small Telescope or TRAPPIST system in Chile that gave it its name.

The TRAPPIST-1 system is located in the constellation Aquarius about 40 light years from Earth. That makes it relatively close to our solar system in cosmic terms.

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The seven exoplanets are so close together that you would be able to see the other six in the sky no matter which one you were standing on. The sun -- TRAPPIST-1 -- would look about three times bigger than our sun here on Earth.

Red dwarf stars

TRAPPIST-1 is classified as an ultra-cool red dwarf star. That's how water could exist on planets which orbit the star much more closely, relative to our own solar system. Their close orbits also raise the possibility that the exoplanets are tidally locked to their sun. That means the same side would always face the star, so that it was always daylight on one side of the planet, and always night time on the other. Weather patterns would be extreme, and very different than what we are used to on Earth.

So why is NASA focusing its search for exoplanets and alien life on the hunt for red dwarf stars? Why not look for a star system more similar to our own? One reason is that red dwarf stars, because of their relatively low mass and the slow rate that they go through the process of using their solar fuel via nuclear fusion, they last a long, long time in that state -- into the trillions of years.

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The development of life forms also takes millions of years. Scientists, at an even sponsored by The Search for Extraterrestrial Intelligence or SETI crunched the numbers and found that statistically, their longevity made red dwarf systems the most likely place to find life a we know it.

Next steps in the hunt for alien life

Currently, the NASA Hubble Space Telescope is studying four of the TRAPPIST-1 planets. The Spitzer Space Telescope will conduct a follow up study this fall to refine the findings, and then it will be up to the brand new James Webb Space Telescope to continue the search for extraterrestrial life in 2018. #aliens