                        Astronomy Picture of the Day

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                               2021 August 29

                  Orbits of Potentially Hazardous Asteroids
                       Image Credit: 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's Double Asteroid Redirection Test (DART) is planned
   for launch later this year. Of course rocks and ice bits of much
   smaller size strike the Earth every day, usually pose no danger, and
   sometimes creating memorable fireball and meteor displays.

                      Tomorrow's picture: ice sky fire
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC
                             & Michigan Tech. U.


