File:PIA17041-Orbits-PotentiallyHazardousAsteroids-Early2013.jpg
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[編輯]描述PIA17041-Orbits-PotentiallyHazardousAsteroids-Early2013.jpg |
English: PIA17041: Orbits of Potentially Hazardous Asteroids (PHAs)
http://photojournal.jpl.nasa.gov/catalog/PIA17041 This graphic shows the orbits of all the known Potentially Hazardous Asteroids (PHAs), numbering over 1,400 as of early 2013. These are the asteroids considered hazardous because they are fairly large (at least 460 feet or 140 meters in size), and because they follow orbits that pass close to the Earth’s orbit (within 4.7 million miles or 7.5 million kilometers). But being classified as a PHA does not mean that an asteroid will impact the Earth: None of these PHAs is a worrisome threat over the next hundred years. By continuing to observe and track these asteroids, their orbits can be refined and more precise predictions made of their future close approaches and impact probabilities. More information about asteroids and near-Earth objects is at: http://www.jpl.nasa.gov/asteroidwatch. |
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來源 | http://photojournal.jpl.nasa.gov/jpeg/PIA17041.jpg |
作者 | NASA/JPL-Caltech |
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[編輯]Public domainPublic domainfalsefalse |
本作品由NASA創作,屬於公有領域。根據NASA的版權政策:“NASA的創作除非另有聲明否則不受版權保護。”(參見:Template:PD-USGov/zh,NASA版權政策或JPL圖像使用政策) | ||
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2014年2月18日 (二) 21:54 | 3,254 × 2,613(795 KB) | Drbogdan(對話 | 貢獻) | User created page with UploadWizard |
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