                        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.

                              2024 December 22
   An artist's illustration shows where our Sun resides relative to local
    interstellar gas. The direction of motion of the Sun and local gas is
       shown with arrows. Please see the explanation for more detailed
                                information.

                               The Local Fluff
         Illustration Credit: NASA, SVS, Adler, U. Chicago, Wesleyan

   Explanation: The stars are not alone. In the disk of our Milky Way
   Galaxy, about 10 percent of visible matter is in the form of gas called
   the interstellar medium (ISM). The ISM is not uniform and shows
   patchiness even near our Sun. It can be quite difficult to detect the
   local ISM because it is so tenuous and emits so little light. This
   mostly hydrogen gas, however, absorbs some very specific colors that
   can be detected in the light of the nearest stars. A working map of the
   local ISM within 20 light-years, based on ongoing observations and
   particle detections from the Earth-orbiting Interstellar Boundary
   Exporer satellite (IBEX), is shown here. These observations indicate
   that our Sun is moving through a Local Interstellar Cloud as this cloud
   flows outwards from the Scorpius-Centaurus Association star forming
   region. Our Sun may exit the Local Cloud, also called the Local Fluff,
   during the next 10,000 years. Much remains unknown about the local ISM,
   including details of its distribution, its origin, and how it affects
   the Sun and the Earth. Unexpectedly, IBEX spacecraft measurements
   indicate that the direction from which neutral interstellar particles
   flow through our Solar System is changing.

        APOD Year in Review: Night Sky Network Presentation for 2024
                        Tomorrow's picture: sky tree
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

