For the first time ever, astronomers have discovered a system of seven Earth-sized planets orbiting around a single star.

　　The finding was announced Wednesday by officials from NASA – the U.S. space agency – and other research team members. The discovery was also published in the journal Nature.

　　Scientists said three of the newly discovered planets are in the so-called habitable zone. This is the area around the parent star where a rocky planet is most likely to have liquid water, and possibly life.

　　Thomas Zurbuchen is an associate administrator of NASA's Science Mission Directorate in Washington. He said the discovery could play an important role in finding new environments that could support life forms.

　　"Answering the question ‘are we alone' is a top science priority," he said. "And finding so many planets like these for the first time in the habitable zone is a remarkable step forward toward that goal."

　　The new discovery set the record for the most habitable-zone planets found around a single star. These planets outside our solar system are called exoplanets. NASA says the seven new discoveries are just 40 light years away from earth.

　　The planets were observed by NASA's Spitzer Telescope. NASA says the planets are circling around a small, nearby dwarf star called TRAPPIST-1. The star is not hot like the sun. It is very cool, meaning liquid water could survive on planets orbiting close to it.

　　Scientists say further study is needed to determine whether these rocky, terrestrial planets could support any life forms. But they agree that the new discovery shows the possibility that many other Earth-size planets could be out there.

　　Thomas Zurbuchen said the latest findings provide valuable information about other worlds and what they may look like. But he added that much remains unknown and will only become clear with future discoveries.

　　"There's many things we don't know - many questions we have that come up when we see these observations. We look at all these animations. Very likely nature is way more beautiful, way more amazing than what we've animated here. It's always that way."

　　Sara Seager is a professor of planetary science and physics at the Massachusetts Institute of Technology (MIT). She said the new exoplanet discoveries gives her great hope for future research about other worlds.

　　"When there's one, there's more. And so that's why I'm so excited to be here today to share it with you. Because with this amazing system, we know that there must be many more potentially life-bearing worlds out there just waiting to be found."

　　Some of this future research will be completed with the help of new advanced observance tools NASA has yet to launch.

　　One of those is the James Webb Space Telescope – a large infrared telescope with a nearly 7-meter mirror. It is scheduled to launch in October 2018.

　　I'm Bryan Lynn.

　　Bryan Lynn wrote this story for VOA Learning English, based on information from NASA and a report from Associated Press. Hai Do was the editor.

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