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Астронет: Астрономическая картинка дня Орбиты потенциально опасных астероидов http://variable-stars.ru/db/msg/1904059/eng |
Credit & Copyright: NASA,
JPL-Caltech
Explanation:
Are asteroids dangerous?
Some are, but the likelihood of a dangerous asteroid striking the Earth during any
given year is low.
Because some past mass
extinction events have been linked to asteroid impacts, however,
humanity has made it a priority to find and catalog those
asteroids
that may one day affect
life on Earth.
Pictured here
are the orbits of the over 1,000 known
Potentially Hazardous Asteroids (PHAs).
These documented tumbling
boulders
of rock and ice are over 140 meters across and
will pass within 7.5 million kilometers of Earth --
about 20 times the distance to the Moon.
Although none of them will
strike the Earth in the next 100 years --
not all PHAs have been discovered,
and past 100 years, many orbits become hard to predict.
Were an
asteroid of this size to
impact the Earth,
it could raise dangerous tsunamis,
for example.
To investigate Earth-saving strategies, NASA successfully tested the
Double Asteroid Redirection
Test
(DART) mission last year.
Of course, rocks and ice bits of much smaller size
strike the Earth every day,
usually pose no danger, and sometimes create
memorable fireball and
meteor displays.
Today is: Asteroid Day
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.