[ti:Newly Discovered Solar System Matches Our Own] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.00]The American space agency NASA and the technology company Google [00:06.73]have identified an eighth planet in a faraway solar system. [00:12.14]That solar system now has exactly the same number of planets as our own. [00:19.64]Machines made the surprising discovery, not human researchers. [00:26.09]NASA and Google representatives made a joint announcement [00:31.45]about the discovery on December 14. [00:35.13]The newly discovered planet orbits the star known as Kepler-90. [00:41.69]The system is about 2,545 light-years away. [00:48.53]A light-year is about 9.5 trillion kilometers. [00:54.41]Researchers have named the planet Kepler-90i. [00:59.66]Like Earth, Kepler-90i is the third farthest planet from its sun. [01:06.97]However, Kepler-90i is much closer to its sun. [01:12.64]It only takes the planet 14 days to orbit Kepler-90. [01:18.55]So, its surface is much warmer -- 427 degrees Celsius. [01:26.41]In fact, all the planets in the Kepler-90 solar system orbit [01:32.16]closer to their sun than Earth does to our sun. [01:36.44]So far, this is the only other eight-planet solar system [01:42.08]that researchers have found. [01:44.33]Eight is the largest number of planets ever observed around a single sun. [01:50.60]Our solar system had nine planets up until 2006, [01:56.97]when the International Astronomical Union decided Pluto [02:01.86]did not meet the requirements to be considered a planet. [02:06.27]Instead, the group renamed it a dwarf planet. [02:11.08]But some astronomers believe there could be [02:14.94]a large ninth planet far off in our solar system. [02:19.70]They call it Planet X, and believe it is the size of Neptune. [02:25.89]Researchers also believe there could be nine [02:29.68]or more planets in the Kepler-90 solar system. [02:33.96]Google used data from NASA's special planet-hunting device, [02:39.97]called the Kepler Space Telescope, to locate Kepler-90i. [02:45.53]The company used the data to develop a computer program [02:50.42]with machine learning. [02:52.35]This means it can learn and improve itself [02:56.24]without a programmer telling it to do so. [02:59.46]The program carefully studies planetary signals [03:03.66]that are so weak it would take humans years to examine them. [03:08.29]Christopher Shallue is a senior software engineer [03:12.62]at Google in Mountain View, California. [03:15.63]He said, "This is a really exciting discovery, [03:20.04]and we consider it to be a successful proof of concept [03:24.74]to be using neural networks to identify planets, [03:28.87]even in ... situations where the signals are very weak." [03:33.28]NASA astrophysicist and Kepler project scientist Jessie Dotson [03:40.00]said she is "so excited to see where this goes next." [03:44.52]Shallue partnered with astronomer Andrew Vanderburg [03:49.53]of the University of Texas at Austin [03:52.46]to develop this machine-learning program. [03:55.70]The two trained a computer to identify planets beyond our solar system. [04:02.25]To do so, it used observations of the minor changes [04:07.30]in the brightness of stars when planets passed [04:10.67]in front of them that the Kepler Space Telescope had recorded. [04:14.92]Shallue and Vanderburg plan to continue hunting for new planets. [04:20.75]They plan to use the program to examine the more than 150,000 stars [04:27.33]that the Kepler Space Telescope has already identified. [04:31.93]So far, esearchers have confirmed the existence of [04:37.00]more than 3,560 planets beyond our solar system. [04:42.95]The Kepler Space Telescope, which launched in 2009, [04:47.84]located about two-thirds of them. [04:50.71]Another 4,500 possible exoplanets await confirmation. [04:58.03]I'm Pete Musto. 更多听力请访问51VOA.COM