Last week, astronomers made a record-breaking discovery. They spied seven Earth-size planets circling a single star beyond our solar system. At least three of the planets lie within the star’s habitable zone—an area of space that has the best conditions to support life.
“This is an amazing planetary system—not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth,” Michaël Gillon said in a recent statement. He’s an astronomer at the University of Liège in Belgium and one of the planets’ discoverers.
The system, called TRAPPIST-1, is named for The Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile. Researchers using the telescope first discovered three planets in the system. Several other ground-based telescopes soon turned up four additional ones. The group of planets is located 40 light years from Earth—about 386 trillion kilometers (240 trillion miles).
STRANGE NEW WORLDS
TRAPPIST-1’s exoplanets—planets outside our solar system—are rocky like Earth. But they may not spin like Earth does on its axis (the imaginary line around which a body in space rotates). If they don’t spin, the same side of each planet would always face its star. That would make it forever day on one side of the planet and night on the other.
The planets are located much nearer to their star than Mercury is to our sun. (Mercury is the planet closest to the sun in our solar system.) Despite the closeness, the planets are thought to experience much cooler temperatures than Mercury. The reason is that the system’s star is an ultra-cool dwarf. This type of star is much smaller and cooler than our sun.
The planets are also extremely close to one another. A person standing on one planet’s surface would be able to see landforms and clouds on its neighboring worlds.
SEARCH FOR ALIEN LIFE
What really excites scientists is that all of TRAPPIST-1’s planets could have liquid water on their surfaces. Liquid water is a necessary ingredient for life as we know it. That makes the newly discovered worlds good places to look for life beyond Earth.
NASA hopes to continue studying the planets using its new James Webb Space Telescope, which will launch in 2018. The telescope will be able to analyze the chemical makeup of each planet’s atmosphere (the envelope of gases surrounding a body in space). It will also determine the planets’ temperatures—another important factor in whether life might exist there.