An exoplanet (extrasolar planet) is a planet located outside the Solar System. The first confirmed detection of exoplanets was announced in 1992, with two planets found orbiting a pulsar. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods such as the transit method and the radial-velocity method.
Talk about lucky number seven. Astronomers have discovered not one, not two, but seven Earth-sized planets orbiting a star called TRAPPIST-1.
Turns out it wasn’t just dust on the telescope lens, Nasa astronomers have spotted seven Earth-size planets around a nearby star, some or all of which could harbour water and possibly life, so Google has marked the Earth-shattering discovery with a Doodle.
Three of TRAPPIST-1’s “exoplanets” are smack dab in the so-called habitable zone, also known as the Goldilocks zone, where conditions are just right for watery oceans – not too much and not too little stellar energy – greatly increasing the likelihood of life.
No other star system known contains such a large number of Earth-sized and probably rocky planets. All are about the same size as Earth or Venus, or slightly smaller. Because the parent star is so dim, the planets are warmed gently despite having orbits much smaller than that of Mercury, the planet closest to the sun.
Scientists said they need to study the atmospheres before determining whether these rocky, terrestrial planets could support some sort of life. But just because a planet is in this sweet spot, doesn’t mean life exists or ever did.
The discovery, reported in the journal Nature, was made by astronomers using Nasa’s exoplanet-hunting Spitzer Space Telescope. The telescope operates at the infrared wavelengths which glow brightest from TRAPPIST-1, and can detect the tiny dimming that occurs when a passing or “transiting” planet blocks out light from its star. Spitzer’s data allowed the team to measure precisely the sizes of the seven planets and estimate the masses and densities of six of them.
The discovery sets a new record for greatest number of habitable-zone planets found around a single star outside our solar system. All of these seven planets could have liquid water – key to life as we know it – under the right atmospheric conditions, but the chances are highest with the three in the habitable zone.
“This discovery could be a significant piece in the puzzle of finding habitable environments, places that are conducive to life,” said Thomas Zurbuchen, associate administrator of the agency’s Science Mission Directorate in Washington. “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.”
This is the first time astronomers have found so many Earth-sized planets circling the same sun.
Let’s hope we find our neighbours soon!