An artist's illustration of the strange Earth-like rocky planet Kepler-78b, which orbits a sun-like star 400 light-years from Earth. The planet is 20 percent wider and 80 percent more massive than Earth. 
 
 Credit: David A. Aguilar (CfA) View full size image 
 
 A puzzling alien planet is the closest thing to an Earth twin in size and composition known beyond our solar system, though it's far too hot to support life, scientists say. 
 
 The exoplanet Kepler-78b, whose supertight orbit baffles astronomers, is just 20 percent wider and about 80 percent more massive than Earth, with a density nearly identical to that of our planet, two research teams report in separate papers published online today (Oct. 30) in the journal Nature. 
 
 "This is the planet that, in many respects, is the most like Earth that's been discovered outside our solar system," said Andrew Howard, of the University of Hawaii at Manoa's Institute for Astronomy and lead author of one of the studies. "It has approximately the same size. It has the same density, which means it's made out of the same stuff as Earth, in all likelihood." [The Strangest Alien Planets (Gallery)] 
 
 Studying a lava world 
 
 Kepler-78b, whose discovery was announced last month, orbits a sunlike star in the constellation Cygnus, about 400 light-years from Earth. 
 
 The alien world circles 900,000 miles (1.5 million kilometers) or so from its parent star — just 1 percent of the distance between Earth and the sun— and completes one lap every 8.5 hours. Surface temperatures on Kepler-78b likely top 3,680 degrees Fahrenheit (2,000 degrees Celsius), Howard said. 
 
 The planet was found by NASA's prolific Kepler space telescope, which has spotted nearly 3,600 potential exoplanets since its March 2009 launch. (Kepler was hobbled in May of this year when the second of its orientation-maintaining reaction wheels failed, but scientists are still sifting through the instrument's huge databases.) 
 
 Kepler flagged alien worlds by noting the telltale brightness dips they caused when passing in front of, or transiting, their parent stars from the spacecraft's perspective. Kepler's measurements allow researchers to estimate an exoplanet's size but not its mass, meaning that other strategies are required to get a handle on a world's density and composition. [Gallery: A World of Kepler Planets] 
 
 One such method is the radial velocity technique, which measures the wobble in a host star's light induced by the gravitational pull of an orbiting planet. Both new studies employed this method to investigate the Kepler-78 system, with Howard's group using the HIRES spectrograph at Hawaii's Keck Observatory and another team, led by Francesco Pepe of the University of Geneva, relying on the new HARPS-N instrument on the Telescopio Nazionale Galileo in the Canary Islands. 
 
 The two teams came to very similar conclusions. Howard's group determined Kepler-78b's mass to be 1.69 times greater than that of Earth, while Pepe's team calculated it to be 1.86 times higher than Earth's. The results of the Pepe-led study suggest a density of 5.57 grams per cubic centimeter for Kepler-78b, while those of Howard's team imply a density of 5.3 grams per cubic cm. 
 
 These numbers agree to within the error range independently estimated by both teams, suggesting that they are quite accurate, Howard said. 
 
 "The fact that we agree to within our errors — in science, that's basically as good as you can do," Howard told SPACE.com. 
 
 Earth's density is about 5.5 grams per cubic cm, so Kepler-78b probably has an Earth-like composition, complete with a rocky interior and an iron core, both studies suggest. 
 
 A mysterious origin 
 
 The extremely tight orbit of Kepler-78b puzzles astronomers. According to prevailing theory, the alien world shouldn't exist where it does, because its host star was significantly larger when the planet was taking shape. 
 
 "It couldn't have formed in place because you can't form a planet inside a star," Dimitar Sasselov, of the Harvard-Smithsonian Center for Astrophysics and a member of the Pepe-led team, said in a statement. "It couldn't have formed further out and migrated inward, because it would have migrated all the way into the star. This planet is an enigma." 
 
 What is clear, however, is that Kepler-78b's days are numbered. The planet will continue circling lower and lower until the immense gravity of its host star tears it apart, likely within 3 billion years or so. 
 
 "Kepler-78b is going to end up in the star very soon, astronomically speaking," Sasselov said. 
 
 The search for another Earth 
 
 The hellishly hot Kepler-78b is not a good place to hunt for alien life. But the determination of its density marks a milestone in the ongoing search for a true "Earth twin" — a planet very much like Earth in size, composition and surface temperature. 
 
 "The existence of Kepler-78b shows that, at the very least, extrasolar planets of Earth-like composition are not rare," astronomer Drake Deming, of the University of Maryland, writes in an accompanying commentary article today in the same issue of Nature. 
 
 Deming points to NASA's upcoming Transiting Exoplanet Survey Satellite mission, or TESS, which is slated to launch in 2017 to hunt for transiting planets around nearby stars (as contrasted with Kepler, whose gaze was more distant). 
 
 "By focusing particularly on small stars cooler than the sun, TESS should find exo-Earths whose mass can be measured by trading the close-in orbit of Kepler-78b for more distant orbits around low-mass stars, approaching orbital zones where life is possi­ble," Deming writes. "That trade-off probably cannot be pushed to the point of measuring an Earth twin orbiting once per year around a sun twin, but it will allow future scientific teams to probe habitable planets orbiting small stars." 
 
 Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @Spacedotcom, Facebook or Google+. Originally published on SPACE.com. ||||| (CNN) Astronomers have found at least seven Earth-sized planets orbiting the same star 40 light-years away, according to a study published Wednesday in the journal Nature. The findings were also announced at a news conference at NASA Headquarters in Washington. 
 
 This discovery outside of our solar system is rare because the planets have the winning combination of being similar in size to Earth and being all temperate, meaning they could have water on their surfaces and potentially support life. 
 
 "This is the first time that so many planets of this kind are found around the same star," said Michaël Gillon, lead study author and astronomer at the University of Liège in Belgium. 
 
 The seven exoplanets wereall found in tight formation around an ultracool dwarf star called TRAPPIST-1 . Estimates of their mass also indicate that they are rocky planets, rather than being gaseous like Jupiter. Three planets are in the habitable zone of the star, known as TRAPPIST-1e, f and g, and may even have oceans on the surface. 
 
 The TRAPPIST-1 star, an ultracool dwarf, has seven Earth-size planets orbiting it. 
 
 The researchers believe that TRAPPIST-1f in particular is the best candidate for supporting life. It's a bit cooler than Earth, but could be suitable with the right atmosphere and enough greenhouse gases. 
 
 If TRAPPIST-1 sounds familiar, that's because these researchers announced the discovery of three initial planets orbiting the same star in May. The new research increased that number to seven planets total. 
 
 "I think we've made a crucial step towards finding if there is life out there," said Amaury Triaud, one of the study authors and an astronomer at the University of Cambridge. "I don't think any time before we had the right planets to discover and find out if there was (life). Here, if life managed to thrive and releases gases similar to what we have on Earth, we will know." 
 
 Life may begin and evolve differently on other planets, so finding the gases that indicate life is key, the researchers added. 
 
 "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 NASA's Science Mission Directorate. "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." 
 
 And as we've learned from studying and discovering exoplanets before, where there is one, there are more, said Sara Seager, professor of planetary science and physics at Massachusetts Institute of Technology. Seager and other researchers are encouraged by the discovery of this system because it improves our chances of finding another habitable planet, like Earth, in the future, by knowing where to look. 
 
 What we know 
 
 The planets are so close to each other and the star that there are seven of them within a space five times smaller than the distance from Mercury to our sun. This proximity allows the researchers to study the planets in depth as well, gaining insight about planetary systems other than our own. 
 
 The seven planets of TRAPPIST-1 compared with Mercury, Venus, Earth and Mars. 
 
 Starting closest to the star and moving out, the planets have respective orbits from one and a half to nearly 13 Earth days. The orbit of the farthest planet is still unknown. 
 
 Standing on the surface of one of the planets, you would receive 200 times less light than you get from the sun, but you would still receive just as much energy to keep you warm since the star is so close. It would also afford some picturesque views, as the other planets would appear in the sky as big as the moon (or even twice as big). 
 
 On TRAPPIST-1f, the star would appear three times as big as the sun in our sky. And because of the red nature of the star, the light would be a salmon hue, the researchers speculate. 
 
 The researchers believe the planets formed together further from the star. Then, they moved into their current lineup. This is incredibly similar Jupiter and its Galilean moons. 
 
 Like the moon, the researchers believe the planets closest to the star are tidally locked. This means that the planets always face one way to the star. One side of the planet is perpetually night, while the other is always day. 
 
 What the TRAPPIST-1 planetary system may look like. 
 
 Based on preliminary climate modeling, the researchers believe that the three planets closest to the star may be too warm to support liquid water, while the outermost planet, TRAPPIST-1h, is probably too distant and cold to support water on the surface. But further observation is needed to know for sure. 
 
 How the discovery was made 
 
 TRAPPIST-1 barely classifies as a star at half the temperature and a tenth the mass of the sun. It is red, dim and just a bit larger than Jupiter. But these tiny ultracool dwarf stars are common in our galaxy. 
 
 Photos: Weird and wonderful planets beyond our solar system Photos: Weird and wonderful planets beyond our solar system This image shows an artist's impression of the surface of Barnard's star b, a cold Super-Earth discovered orbiting Barnard's star 6 light-years away. Hide Caption 1 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's illustration shows newly discovered exoplanet K2-288Bb, 226 light-years away and half the size of Neptune. It orbits the fainter member of a pair of cool M-type stars every 31.3 days. Hide Caption 2 of 30 Photos: Weird and wonderful planets beyond our solar system This is an artist's impression of the exoplanet HAT-P-11b. The planet has an extended helium atmosphere that's being blown away by the star, an orange dwarf star smaller but more active than our sun. Hide Caption 3 of 30 Photos: Weird and wonderful planets beyond our solar system An artist's illustration of what the super-Earth found around the orange-hued star HD 26965 (also known as 40 Eridani A) might look like. The recently discovered exoplanet is being compared to the fictional planet of Vulcan because Star Trek creator Gene Roddenberry said the star was the ideal candidate to host Vulcan, Mr. Spock's home world. Hide Caption 4 of 30 Photos: Weird and wonderful planets beyond our solar system The TRAPPIST-1 star, an ultra-cool dwarf, has seven Earth-size planets orbiting it. Hide Caption 5 of 30 Photos: Weird and wonderful planets beyond our solar system For the first time, eight planets have been found orbiting another star, tying with our solar system for the most known planets around a single star. The Kepler-90 system is in the constellation Draco, more than 2,500 light-years from Earth. Hide Caption 6 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's illustration shows exoplanet Ross 128 b, with its red dwarf host star in the background. The planet is only 11 light-years from our solar system. It is now the second-closest temperate planet to be detected, after Proxima b. Hide Caption 7 of 30 Photos: Weird and wonderful planets beyond our solar system WASP-121b, 880 light-years away, is considered a hot Jupiter-like planet. It has a greater mass and radius than Jupiter, making it "puffier." If WASP-121b were any closer to its host star, it would be ripped apart by the star's gravity. Hide Caption 8 of 30 Photos: Weird and wonderful planets beyond our solar system NASA's Kepler space telescope team has identified 219 more planet candidates, 10 of which are near-Earth size and in the habitable zone of their stars. Hide Caption 9 of 30 Photos: Weird and wonderful planets beyond our solar system Welcome to the KELT-9 system. The host star is a hot, rapidly rotating A-type star that is about 2.5 times more massive and almost twice as hot as our sun. The hot star blasts its nearby planet KELT-9b with massive amounts of radiation, leading to a daylight temperature of 7800 degrees Fahrenheit, hotter that most stars and only 2000 degrees cooler than the sun. Hide Caption 10 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's concept shows OGLE-2016-BLG-1195Lb, a planet orbiting an incredibly faint star 13,000 light-years away from us. It is an "iceball" planet with temperatures reaching minus-400 degrees Fahrenheit. Hide Caption 11 of 30 Photos: Weird and wonderful planets beyond our solar system LHS 1140b is located in the liquid water habitable zone surrounding its host star, a small, faint red star named LHS 1140. The planet weighs about 6.6 times the mass of Earth and is shown passing in front of LHS 1140. Depicted in blue is the atmosphere the planet may have retained. Hide Caption 12 of 30 Photos: Weird and wonderful planets beyond our solar system An artist's concept image of the surface of the exoplanet TRAPPIST-1f. Of the seven exoplanets discovered orbiting the ultracool dwarf star TRAPPIST-1, this one may be the most suitable for life. It is similar in size to Earth, is a little cooler than Earth's temperature and is in the habitable zone of the star, meaning liquid water (and even oceans) could be on the surface. The proximity of the star gives the sky a salmon hue, and the other planets are so close that they appear in the sky, much like our own moon. Hide Caption 13 of 30 Photos: Weird and wonderful planets beyond our solar system Artist's conception of the binary system with three giant planets discovered, where one star hosts two planets and the other hosts the third. The system represents the smallest-separation binary in which both stars host planets that has ever been observed. Hide Caption 14 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to our solar system. Hide Caption 15 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's impression shows a view of the surface of the planet Proxima b. Hide Caption 16 of 30 Photos: Weird and wonderful planets beyond our solar system An artist's rendering shows Earth-sized exoplanets TRAPPIST-1b and 1c in a rare double transit event as they pass in front of their ultracool red dwarf star, which allowed Hubble to take a peek at at their atmospheres. Hide Caption 17 of 30 Photos: Weird and wonderful planets beyond our solar system Out of a new discovery of 104 exoplanets, astronomers found four similar in size to Earth that are orbiting a dwarf star. Two of them have the potential to support life. The craft depicted in this illustration is the NASA Kepler Space Telescope, which has helped confirm the existence of thousands of exoplanets. Hide Caption 18 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. Located about 320 light-years from Earth, the planet is about 16 million years old, making it also one of the youngest exoplanets discovered to date. Hide Caption 19 of 30 Photos: Weird and wonderful planets beyond our solar system An artistic impression of the planet Kepler-1647b, which is nearly identical to Jupiter in both size and mass. The planet is expected to be roughly similar in appearance. But it is much warmer: Kepler-1647b is in the habitable zone. Hide Caption 20 of 30 Photos: Weird and wonderful planets beyond our solar system HD-106906b is a gaseous planet 11 times more massive than Jupiter. The planet is believed to have formed in the center of its solar system, before being sent flying out to the edges of the region by a violent gravitational event. Hide Caption 21 of 30 Photos: Weird and wonderful planets beyond our solar system Kepler-10b orbits at a distance more than 20 times closer to its star than Mercury is to our own sun. Daytime temperatures exceed 1,300 degrees Celsius (2,500 degrees Fahrenheit), which is hotter than lava flows on Earth. Hide Caption 22 of 30 Photos: Weird and wonderful planets beyond our solar system This Jupiter-like planet in the HD-188753 system, 149 light-years from Earth, has three suns. The main star is similar in mass to our own Sun. The system has been compared to Luke Skywalker's home planet Tatooine in "Star Wars." Hide Caption 23 of 30 Photos: Weird and wonderful planets beyond our solar system Kepler-421b is a Uranus-sized transiting exoplanet with the longest known year, as it circles its star once every 704 days. The planet orbits an orange, K-type star that is cooler and dimmer than our Sun and is located about 1,000 light-years from Earth in the constellation Lyra. Hide Caption 24 of 30 Photos: Weird and wonderful planets beyond our solar system Astronomers discovered two planets less than three times the size of Earth orbiting sun-like stars in a crowded stellar cluster approximately 3,000 light-years from Earth in the constellation Cygnus. Hide Caption 25 of 30 Photos: Weird and wonderful planets beyond our solar system This artist's conception shows a hypothetical planet with two moons orbiting in the habitable zone of a red dwarf star. The majority of the sun's closest stellar neighbors are red dwarfs. Hide Caption 26 of 30 Photos: Weird and wonderful planets beyond our solar system Kepler-186f was the first validated Earth-sized planet to be found orbiting a distant star in the habitable zone. This zone a range of distance from a star where liquid water might pool on the planet's surface. Hide Caption 27 of 30 Photos: Weird and wonderful planets beyond our solar system Kepler-69c is a super-Earth-size planet similar to Venus. The planet is found in the habitable zone of a star like our sun, approximately 2,700 light years from Earth in the constellation Cygnus. Hide Caption 28 of 30 Photos: Weird and wonderful planets beyond our solar system The Kepler-444 system formed when the Milky Way was just 2 billion years old. The tightly packed system is home to five planets that range in size, the smallest is comparable to the size of Mercury and the largest to Venus, orbiting their sun in less than 10 days. Hide Caption 29 of 30 Photos: Weird and wonderful planets beyond our solar system This artistic concept image compares Earth, left, with Kepler-452b, which is about 60% larger. Both planets orbit a G2-type star of about the same temperature; however, the star hosting Kepler-452b is 6 billion years old -- 1.5 billion years older than our sun. Hide Caption 30 of 30 
 
 They were largely overlooked until Gillon decided to study the space around one of these dwarfs. 
 
 The researchers used a telescope called TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) to observe its starlight and changes in brightness. The team saw shadows, like little eclipses, periodically interrupting the steady pattern of starlight. This is called transiting. The shadows indicated planets, and further observation confirmed them. 
 
 In July, the team was able to determine that two of the closest planets to the stars had atmospheres that were more compact and comparable to those of Earth, Venus and Mars by observing starlight through the planets' atmosphere. 
 
 By using a global network ground-based telescopes like TRAPPIST and space-based telescopes like Spitzer, the researchers continued looking toward the TRAPPIST system and were able to determine the orbital periods, distances from their star, radius and and masses of the planets. 
 
 What's next 
 
 Over the next decade, the researchers want to define the atmosphere of each planet, as well as to determine whether they truly do have liquid water on the surface and search for signs of life. 
 
 Although 40 light-years away doesn't sound too far, it would take us millions of years to reach this star system. But from a research perspective, it's a close opportunity and the best target to search for life beyond our solar system. 
 
 "If we learn something now, it can determine if we looked in the right place," Gillon said. 
 
 In 2018, the James Webb Space Telescope will launch and be positioned 1 million miles from Earth with an unprecedented view of the universe. It can observe large exoplanets and detect starlight filtered through their atmosphere. 
 
 The researchers are also searching for similar star systems to conduct more atmospheric research. Four telescopes named SPECULOOS (Search for habitable Planets EClipsing ULtra-cOOl Stars) based in Chile will survey the southern sky for this purpose. 
 
 This star system will probably outlive us because this type of star evolves so slowly. When our sun dies, TRAPPIST-1 will still be a young star and will live for another trillion years, Gillon said. After we are gone, if there is another part of the universe for life to carry on, it may be in the TRAPPIST-1 system. 
 
 "This is the most exciting result I have seen in the 14 years of Spitzer operations," said Sean Carey, manager of NASA's Spitzer Science Center at Caltech/IPAC in Pasadena, California. "Spitzer will follow up in the fall to further refine our understanding of these planets so that the James Webb Space Telescope can follow up. More observations of the system are sure to reveal more secrets." ||||| The Gaia mission, scheduled to launch Thursday morning (Dec. 19), could be a bonanza for discovering exoplanets, perhaps finding more than 2,500 new alien worlds, scientists suggest. 
 
 Gaia, a $1 billion (740 million euros) mission from the European Space Agency (ESA), aims to chart a 3D map of the Milky Way by surveying more than 1 billion stars, amounting to about 1 percent of the stars in the galaxy, using its billion-pixel camera. Its goal is to make the largest, most precise map of where Earth dwells by observing the position of each of these stars 70 times over five years. 
 
 ESA will broadcast a live webcast of Gaia's launch atop a Russian Soyuz rocket from the Guiana Space Center in South America beginning at 3:30 a.m. EST (0830 GMT) on Thursday. Gaia is scheduled to launch at 4:12 a.m. EST (0912 GMT), and you can watch the Gaia webcast live on SPACE.com, courtesy of ESA. [See photos of the Gaia spacecraft] 
 
 To pinpoint the position of a star in 3D — a field known as astrometry — Gaia will measure the distance of the star from the sun. The satellite will do so by watching how its position shifts over time. As the Earth orbits the sun, the apparent positions of stars change with regard to each other due to how our viewpoint has moved, a phenomenon known as parallax. 
 
 Discovering a star's distance can narrow down many of its other details. For instance, the actual brightness of a star can only be determined by not only measuring how bright it appears but also how far away it lies and thus how distance might have dimmed its light. Once researchers know how bright a star actually is, they can determine how much fuel it must burn — that is, the star's mass. A star's brightness is also related to its width, and so discovering its brightness can help deduce its size. Knowing a star's mass and size then helps determine the strength of gravity on its surface. 
 
 Gaia will also scan the color of stars. This can help reveal details of their chemical makeup as well as its temperature, as the color of a star depends on its surface temperature. Knowing the brightness and color of a star can also help figure out its age and thus stage in its evolution. All in all, Gaia will help shed light on the composition, formation and evolution of the stars that make up the galaxy, researchers say. 
 
 Gaia will make the largest, most precise 3D map of our galaxy by surveying an unprecedented number of stars. Credit: ESA 
 
 Charting the stars and planets 
 
 Gaia is not the first space mission to chart the stars. In 1989, ESA launched the Hipparcos satellite, which charted the positions of more than 100,000 stars with high precision and more than 2 million stars with slightly less precision. In the end, Hipparcos measured the distances of all stars within 325 light-years and bright stars within 3,250 light-years (to within 10 percent). 
 
 In comparison, Gaia will collect more than 30 times more light than Hipparcos. This will help measure a star's position 200 times more accurately. All in all, Gaia can measure the distances of stars as far away as the galactic center — roughly 32,500 light-years away — with an accuracy within 10 percent. 
 
 On top of what light Gaia might shed on the stars in the Milky Way, it may also reveal exoplanets orbiting them, said astronomer Alessandro Sozzetti at the Astrophysical Observatory of Turin in Italy. This could be the first time exoplanets are detected using astrometry. [Video: Galaxy's Most Precise 3D Map: Gaia Probe Will Make It] 
 
 NASA's exoplanet-hunting Kepler spacecraft discovered planets through photometry — that is, by measuring light. It looked at regular dips in starlight caused by planets crossing between stars and Earth. 
 
 Gaia can hunt worlds a different way. The gravitational pull of a planet can introduce a regular wobble in its host star's position as they orbit each other that Gaia can detect over time. 
 
 Gaia will be most effective at detecting giant planets orbiting small stars. These planetary systems are prone to generating significant, noticeable wobbles in a star's position. 
 
 Sozzetti and his colleagues focused on red dwarfs, also known as M dwarf stars, which are relatively small, less than 60 percent the mass of the sun. These stars make up roughly three-quarters of the stars in the galaxy, and scientists recently found red dwarfs are far more common than before thought, making up at least 80 percent of the total number of stars. Moreover, past research suggests about 6.5 percent of red dwarfs host giant Jupiter-mass planets. 
 
 The researchers devised computer models simulating Jupiter-mass planets around the 3,150 red dwarfs known to exist within about 110 light-years of Earth. They estimated Gaia could detect about 100 new giant planets from this sample if such worlds exist about 0.5 to 3 astronomical units around those stars. (An astronomical unit is equal to Earth's distance from the sun — about 93 million miles, or 150 million kilometers.) 
 
 In addition, unlike Kepler, Gaia should be able to deduce the full orbits and masses of these giant worlds. For more than 80 percent of stars detected by Gaia around M dwarf stars within about 110 light-years of Earth, their masses could be measured to within 10 percent. 
 
 Extrapolating from these findings, the researchers suggest Gaia could find about 2,600 giant planets orbiting the roughly 415,000 red dwarfs within about 325 light-years from Earth. [The Strangest Alien Planets (Photos)] 
 
 Sozzetti and his colleagues detailed their findings online Nov. 11 in the journal Monthly Notices of the Royal Astronomical Society. 
 
 "Gaia should be able to detect orbital motion for giant planets orbiting hundreds of M dwarfs," said astronomer David Latham at the Harvard-Smithsonian Center for Astrophysics, who did not take part in this study. 
 
 The researchers also calculated they could accurately derive the masses and orbits of as many as 500 of these 2,600 planets. In addition, within this group of stars, Gaia might identify hints of 10 systems with planets that might possibly noticeably cross in front of their host stars. 
 
 Exoplanet astrometry 
 
 Astronomers have tried detecting exoplanets using astrometry before. Until now, astrometry has only helped confirm the existence of exoplanets detected through other methods, not ones astrometry spotted directly. So far astrometry has suffered about 70 years of blunders in the field of exoplanet detection, "with many a discovery announcement biting the dust," Sozzetti said. "We're finally on the verge of seeing astrometry coming of age and providing substantial contributions to this field." 
 
 Sozzetti cautioned that Gaia is not sensitive enough to detect planets of about Earth's mass, as Kepler is. "Its astrometric accuracy is not sufficient, not even for the nearest stars," he said. 
 
 Gaia should also not be able to detect planets within the habitable zones of red dwarfs — that is, the areas around stars where it is warm enough on a planet's surface for water to stay liquid. Since red dwarfs are very dim, their habitable zones are typically very close to them, about 3 percent to 30 percent of an astronomical unit. The astrometric signals caused by planets get increasingly smaller the closer they are to their stars, meaning that worlds in a red dwarf's habitable zone would probably be too difficult to detect. 
 
 However, Sozzetti said Gaia could provide unique insights "on the existence of systems in which the likelihood of a potentially habitable terrestrial planet may have formed is high." By seeing where a giant planet is orbiting a star, Gaia can help rule out any systems where giant planets may have interfered with the formation of rocky planets within those stars' habitable zones. 
 
 Sozzetti noted that Gaia and Kepler ought to be highly complementary in several ways. While Kepler can discover many small worlds, Gaia can find thousands of giant planets. 
 
 "The combination of Gaia and Kepler data will allow for a much improved understanding of planetary systems' properties and frequencies as a function of the host stars' characteristics," Sozzetti said. 
 
 This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program. 
 
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– Astronomers have discovered a planet where a certain red guy with horns could make himself right at home. It's a planet much like our own Earth—about the same size, with the same mixture of rock and iron, and it orbits a star like our sun—except that Kepler 78b is an infernal ball of fire. Located less than a million miles from its host star—that's 1% of the distance between Earth and our sun—its temperature ranges between 3,500 and 5,000 degrees Fahrenheit. That's "well above the temperature where rock melts," an astronomer tells the New York Times. "This is probably one of the most hellish planets that have been discovered yet." At 400 light-years from Earth, the exoplanet was first spotted by the Kepler spacecraft but astronomers on Earth took a closer look at its light frequency to discover its orbit and mass. The findings, published in two studies in Nature, show a planet that tightly orbits its sun—which from the surface would look 80 times larger than our sun—in just eight and a half hours. Adds an expert, per LiveScience: "This planet is an enigma. It couldn't have formed in place because you can't form a planet inside a star." But while astronomers are baffled as to how the planet got there, they're fairly certain it shows friendlier Earthlike planets are still out there.