Teacher:In this task, you are given a text of many news articles seperated by special token "|||||". Your task is to summarize them.
Teacher: Now, understand the problem? Solve this instance: The first two Earth-like worlds orbiting another star have been detected, although neither are believed to be suitable for life. 
  
 But if the planets had water in the past, there's a good chance they could have hung on to it long enough for life to take hold, Linda Elkins-Tanton, with the Carnegie Institution in Washington DC, told reporters on a conference call Tuesday. 
  
 The planets, known as Kepler-20e and 20f, are the smallest planets found so far by NASA's Kepler telescope, which was launched three years ago to look for Earth-sized worlds around other stars. 
  
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 The newly discovered planets have diameters of 6,900 miles and 8,200 miles -- equivalent to 0.87 times Earth -- slightly smaller than Venus -- and 1.03 times Earth. 
  
 They join three Neptune-sized gas giant planets circling the parent star Kepler-20, which is slightly smaller and dimmer than the sun. The system is located about 1,000 light years away in the constellation Lyra. 
  
 While Kepler-20e and 20f are not thought to be habitable, it is "the next major milestone along the road to finding habitable planets around stars beyond the sun," said Kepler project scientist Nick Gautier, with NASA's Jet Propulsion Laboratory in Pasadena, Calif. 
  
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 The two new discoveries were found by a team led by Francois Fressin of the Harvard-Smithsonian Center for Astrophysics, using NASA's Kepler orbiting space telescope. The results were published online in the journal Nature. 
  
 Finding the relatively small planets was a feat. 
  
 Kepler monitors more than 150,000 stars for tiny wobbles in light. The wobbles signal a planet as it passes in front of the star and dims the light reaching the telescope. 
  
 The discovery follows the announcement earlier this month of Kepler-22b, a planet around twice the diameter of Earth that is orbiting the right distance from its parent star for liquid water to exist on its surface. Water is believed to be a key ingredient for life. 
  
 "Kepler-22b has the right temperature, but it is too big. What we're announcing today are just the right size, but too hot. But you can bet that the hunt is on to find a planet that combines the best of both worlds, a true earth twin," said astronomer David Charbonneau with Harvard University. 
  
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 Unlike our solar system where the rocky planets Mercury, Venus, Earth and Mars orbit closer in to the sun than the gas giants Jupiter, Saturn, Uranus and Neptune, the five planets circling Kepler-20 are a mix of rocky and gas planets and all orbit closer to their parent star than Mercury is to the sun. 
  
 "The architecture of that planetary system is crazy," Charbonneau said. "Rocky planets and gas giants happily mingle together. This is the first time we've seen anything like this." 
  
 "I really want to dare my fellow astronomers to try to explain how this system could have formed," he said. ||||| MOFFETT FIELD, Calif. - NASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like our sun. 
  
  
  
 The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra. 
  
  
  
 Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass. 
  
  
  
 "The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. "This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them." 
  
  
  
 The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days. All five planets have orbits lying roughly within Mercury's orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler. 
  
  
  
 The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large. 
  
  
  
 "The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system," said Jack Lissauer, planetary scientist and Kepler science team member at NASA's Ames Research Center in Moffett Field, Calif. "The analysis of Kepler data continues to reveal new insights about the diversity of planets and planetary systems within our galaxy." 
  
  
  
 Scientists are not certain how the system evolved but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes. 
  
  
  
 The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet. 
  
  
  
 The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets. 
  
  
  
 To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet. 
  
  
  
 On Dec. 5 the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface. 
  
  
  
 "In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time," said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. "We are on the edge of our seats knowing that Kepler's most anticipated discoveries are still to come." 
  
  
  
 NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. JPL managed the Kepler mission's development. 
  
  
  
 Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. 
  
  
  
 The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington. 
  
  
  
 For more information about the Kepler mission and to view the digital press kit, visit: http://www.nasa.gov/kepler 
  
  
  
  
  
 This artist's animation flies through the Kepler-20 star system, where NASA's Kepler mission discovered the first Earth-size planets around a star beyond our own. Animation credit: NASA/JPL-Caltech |||||
Student:
For the first time, scientists have discovered planets roughly the size of ours outside our solar system. Kepler-20e and Kepler-20f are the smallest exoplanets yet found, Discovery reports. Because they're so close to the star they orbit, they don't appear habitable, but the finding is "next major milestone to finding habitable planets beyond our solar system," says a NASA scientist. A year on Kepler-20e—that is, a full orbit of its star—takes about six days, while Kepler-20f completes its orbit in about 20 days, NASA reports. The planets were discovered using the Kepler space telescope, fulfilling the Kepler mission's "primary goal," says the head of the team that made the find. "This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them."