                        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.

                                2022 April 3

                  CMB Dipole: Speeding Through the Universe
              Image Credit: DMR, COBE, NASA, Four-Year Sky Map

   Explanation: Our Earth is not at rest. The Earth moves around the Sun.
   The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy
   orbits in the Local Group of Galaxies. The Local Group falls toward the
   Virgo Cluster of Galaxies. But these speeds are less than the speed
   that all of these objects together move relative to the cosmic
   microwave background radiation (CMBR). In the featured all-sky map from
   the COBE satellite in 1993, microwave light in the Earth's direction of
   motion appears blueshifted and hence hotter, while microwave light on
   the opposite side of the sky is redshifted and colder. The map
   indicates that the Local Group moves at about 600 kilometers per second
   relative to this primordial radiation. This high speed was initially
   unexpected and its magnitude is still unexplained. Why are we moving so
   fast? What is out there?

                     Tomorrow's picture: auroral vortex
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                             & Michigan Tech. U.

