Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                               2021 January 31

                          Asteroids in the Distance
      Image Credit: NASA, ESA, Hubble; R. Evans & K. Stapelfeldt (JPL)

   Explanation: Rocks from space hit Earth every day. The larger the rock,
   though, the less often Earth is struck. Many kilograms of space dust
   pitter to Earth daily. Larger bits appear initially as a bright meteor.
   Baseball-sized rocks and ice-balls streak through our atmosphere daily,
   most evaporating quickly to nothing. Significant threats do exist for
   rocks near 100 meters in diameter, which strike the Earth roughly every
   1000 years. An object this size could cause significant tsunamis were
   it to strike an ocean, potentially devastating even distant shores. A
   collision with a massive asteroid, over 1 km across, is more rare,
   occurring typically millions of years apart, but could have truly
   global consequences. Many asteroids remain undiscovered. In the
   featured image, one such asteroid -- shown by the long blue streak --
   was found by chance in 1998 by the Hubble Space Telescope. A collision
   with a large asteroid would not affect Earth's orbit so much as raise
   dust that would affect Earth's climate. One likely result is a global
   extinction of many species of life, possibly dwarfing the ongoing
   extinction occurring now.

                       Tomorrow's picture: bunny-moon
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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