B*V
发帖数: 3365 | 1 【 以下文字转载自 Headline 讨论区 】
发信人: zongheimun (feifei), 信区: Headline
标 题: Next Friday, a 130,000 ton asteroid is set to pass perilously close
to earth.
发信站: BBS 未名空间站 (Sat Feb 9 14:03:20 2013, 美东)
National Aeronautics and Space Administration experts who plotted its
trajectory are confident that the primordial rock, weighing an estimated 130
,000 metric tons, will pass within "a remarkably close distance" of Earth,
nearer than many orbiting communications satellites but far enough away to
safely speed past the planet.
At its closest approach—a distance of about 17,200 miles or so away—the
asteroid will pass over the eastern Indian Ocean, off Sumatra at 2:24 pm ET
Friday, Feb. 15. It will be travelling eight times as fast as a bullet from
a high-powered rifle. Depending on local weather, it may be visible from
Eastern Europe, Australia and Asia, with binoculars or a moderately powered
telescope, space-agency officials said.
"No Earth impact is possible," said asteroid expert Donald Yeomans at the
Jet Propulsion Laboratory in Pasadena, Calif. The asteroid poses no danger
to the 400 or so satellites in higher orbits around Earth, agency officials
said.
Known officially as 2012 DA14, the asteroid is about 150 feet across and was
discovered last February by astronomers at the La Sagra Sky Survey operated
by the Astronomical Observatory of Mallorca in Spain.
In its journey through space, Earth is bombarded by a hailstorm of comets,
meteors and asteroids. Most are motes that sparkle like fireflies as they
burn up entering the atmosphere, about 100 tons worth each day. Others have
had catastrophic consequences.
Highlighting the risks such asteroids pose to the planet, researchers at the
University of California, Berkeley, on Thursday tightened the link between
the demise of most dinosaurs 66 million years ago and the impact of a six-
mile-wide asteroid that left a 110-mile-wide crater off the Yucatan coast of
Mexico. On a geologic time scale, the two events occurred at virtually the
same moment, according to new and more precise dating results that they
reported in the journal Science.
All told, scientists at NASA's Jet Propulsion Laboratory estimate there are
about 500,000 objects about the size of asteroid 2012 DA14 that regularly
cross Earth's path. At least one object that size flies close to Earth about
every 40 years and one likely hits the planet about once every 1,200 years,
astronomers calculate.
They believe the impact of an asteroid that size would generate about 2.5
megatons of blast energy—about twice the explosive power of the B83 nuclear
warhead currently deployed in the U.S. military arsenal.
比月球还近 不会被地球引力吸过来吗？？
原来玛雅人的预言是真的 只是晚了一个月
下周五 见证事实时刻到了！ |
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