For 30 years, the world’s astronomers have searched the cosmos for exoplanets. We recently hit a milestone now that more than 6,000 have been found.<\/p>\n
In our solar system<\/a>, Earth is one of but eight planets \u2013 nine if you really want to count Pluto \u2013 and the only one remotely hospitable to life.<\/p>\n But look beyond our sun’s gravitational pull into the bounds of interstellar space<\/a>, and you’ll find a cosmic landscape absolutely brimming with an abundance of worlds of all sizes and characteristics<\/a>. In fact, three decades since the first exoplanet was found, NASA has recorded a milestone 6,000-plus worlds beyond our solar system.<\/p>\n And as technology advances, astronomers only expect to continue discovering a wider variety of exoplanets amid the billions that are thought to exist. But even after 30 years of searching the cosmos, one question continues to nag at scientists: Are we alone in the universe?<\/p>\n “Is Earth the only home for life? Or are there other habitable worlds waiting to be found?” a narrator says in a NASA video<\/a> promoting the milestone. “With every planet we discover, we get closer to answering that question.”<\/p>\n Here’s everything to know about exoplanets, and why scientists believe that searching for them is the best way to discover whether life exists anywhere else in the universe.<\/p>\n What is an exoplanet?<\/p>\n Exoplanets<\/a>\u00a0are\u00a0planets<\/a>\u00a0outside Earth’s solar system. For that reason,\u00a0these celestial bodies<\/a>\u00a0are sometimes also referred to as extrasolar planets.<\/p>\n Some, called\u00a0rogue planets<\/a>, don’t even orbit a star, but rather are floating through the cosmos untethered.<\/p>\n How many exoplanets are there?<\/p>\n In 1995, a gas giant known as 51 Pegasi b<\/a>, which orbits a star similar to Earth’s sun<\/a>, etched its name in cosmic history as the first exoplanet ever discovered.<\/p>\n Since then, astronomers around the world have spent 30 years finding and confirming the existence of thousands of more exoplanets in the far reaches of the cosmos.<\/p>\n As of Monday, Sept. 22, a total of 6,007 exoplanets have been confirmed, according to NASA’s Exoplanet Science Institute<\/a>, which monitors and tracks exoplanets. Because confirmed planets are regularly added to the count, no single planet is considered the milestone 6,000th entry, NASA said in a press release<\/a> in September announcing the achievement.<\/p>\n What’s more, not only are nearly 8,000 additional exoplanet candidates awaiting official confirmation, but billions are thought to exist<\/a>, astronomers say.<\/p>\n How do scientists find exoplanets?<\/p>\n Both ground- and space-based cosmic observatories<\/a>, including the James Webb<\/a> and Hubble<\/a> space telescopes, are integral in imaging and collecting data on possible exoplanets.<\/p>\n Astronomers also anticipate that new and future cutting-edge space missions could lead to the discovery of even more. That includes\u00a0NASA\u2019s upcoming\u00a0Nancy Grace Roman Space Telescope<\/a>, which is designed to discover thousands of new exoplanets primarily through a technique called\u00a0gravitational microlensing.<\/p>\n \u201cThis milestone represents decades of cosmic exploration driven by NASA space telescopes \u2013 exploration that has completely changed the way humanity views the night sky,\u201d Shawn Domagal-Goldman, acting director of NASA’s astrophysics division, said in a statement.<\/p>\n Have we found life on any exoplanets?<\/p>\n In short, not yet.<\/p>\n An exoplanet known as K2-18b achieved a degree of fame in April<\/a>\u00a0when a team of astronomers claimed to have found in its atmosphere “the strongest evidence yet” that\u00a0life exists anywhere else besides Earth. Other scientists have since\u00a0cast doubt on the findings<\/a> \u2013 putting a damper on the notion that humanity finally had proof that we aren’t alone in the cosmos.<\/p>\n Are any exoplanets similar to Earth?<\/p>\n That’s why astronomers are pressing on, looking for one planet that closely resembles Earth and, thus, could potentially harbor living organisms.<\/p>\n The cosmos may be home to both rocky and gaseous worlds resembling planets in our solar system, but it is also teeming with incredible and strange planets that are nothing like those orbiting our sun. The universe is home to Jupiter-size planets that\u00a0orbit closer to their parent star<\/a>\u00a0than Mercury orbits the sun, and planets that\u00a0orbit two stars<\/a>, like one named Kepler-16b<\/a> that has drawn comparisons to Tattoine in “Star Wars.”<\/p>\n Astronomers have also discovered the coldest exoplanet imaged to date, 14 Herculis c, which is\u00a0about seven times the mass of Jupiter and as cold as 26 degrees Fahrenheit<\/a>. For comparison, most planets are thousands of degrees Fahrenheit.<\/p>\n There are also planets like WASP-193b, which is larger than Jupiter but light and wispy like cotton candy<\/a>, and inhospitable worlds like WASP-107b<\/a>,\u00a0where sandy clouds high in the atmosphere fall like rain onto the surface<\/a>.<\/p>\n But amid these thousands of worlds,\u00a0“There’s one we haven’t found \u2013 a planet just like ours,” according to NASA’s video about exoplanets.<\/p>\n “At least, not yet.”<\/p>\n Eric Lagatta is the Space Connect reporter for the USA TODAY Network. Reach him at elagatta@gannett.com<\/p>\n","protected":false},"excerpt":{"rendered":"For 30 years, the world’s astronomers have searched the cosmos for exoplanets. 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