Astronomy Picture of the Day

   [1]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 October 9
    [2]See Explanation. Clicking on the picture will download the highest
                        resolution version available.

                         50 Light-years to 51 Pegasi
              Image Credit & [3]Copyright: [4]Josselin Desmars

   Explanation: [5]It's only 50 light-years to 51 Pegasi. That star's
   position is indicated in this snapshot from August, taken on a hazy
   night with mostly brighter stars visible above the dome at Observatoire
   de Haute-Provence in France. [6]Twenty-six years ago, in October of
   1995, astronomers [7]Michel Mayor and Didier Queloz announced a
   profound discovery made at the observatory. Using a precise
   spectrograph they had detected a planet orbiting 51 Peg, the first
   known exoplanet orbiting a sun-like star. Mayor and Queloz had used the
   spectrograph to measure changes in the [8]star's radial velocity, a
   regular wobble caused by the gravitational tug of the orbiting planet.
   [9]Designated 51 Pegasi b, the planet was determined to have a mass at
   least half of Jupiter's mass and an orbital period of 4.2 days, making
   it much closer to its parent star than Mercury is to the Sun. Their
   discovery was quickly confirmed and Mayor and Queloz were ultimately
   awarded the [10]Nobel Prize in physics in 2019. Now recognized as the
   prototype for the class of exoplanets fondly known as [11]hot Jupiters,
   51 Pegasi b was formally [12]named Dimidium, latin for half, in 2015.
   Since its discovery, over 4,000 [13]exoplanets have been found.

                  Tomorrow's picture: full moon silhouettes
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    Authors & editors: [25]Robert Nemiroff ([26]MTU) & [27]Jerry Bonnell
                                 ([28]UMCP)
          NASA Official: Phillip Newman [29]Specific rights apply.
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                A service of: [31]ASD at [32]NASA / [33]GSFC
                           & [34]Michigan Tech. U.

References

   1. https://apod.nasa.gov/apod/archivepix.html
   2. https://apod.nasa.gov/apod/image/2110/peg51_desmars.jpg
   3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
   4. http://josselin.desmars.free.fr/work/
   5. https://exoplanets.nasa.gov/exoplanet-catalog/7001/51-pegasi-b/
   6. https://apod.nasa.gov/apod/ap951201.html
   7. https://ui.adsabs.harvard.edu/abs/1995Natur.378..355M/abstract
   8. https://www.planetary.org/articles/color-shifting-stars-the-radial-velocity-method
   9. https://exoplanets.nasa.gov/exoplanet-catalog/7001/51-pegasi-b/
  10. https://www.nobelprize.org/prizes/physics/2019/summary/
  11. https://arxiv.org/abs/1801.06117
  12. https://earthsky.org/space/this-date-in-science-first-planet-discovered-around-sunlike-star/
  13. https://exoplanets.nasa.gov/faq/6/how-many-exoplanets-are-there/
  14. https://apod.nasa.gov/apod/ap211008.html
  15. https://apod.nasa.gov/apod/archivepix.html
  16. https://apod.nasa.gov/apod/lib/apsubmit2015.html
  17. https://apod.nasa.gov/apod/lib/aptree.html
  18. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search
  19. https://apod.nasa.gov/apod/calendar/allyears.html
  20. https://apod.nasa.gov/apod.rss
  21. https://apod.nasa.gov/apod/lib/edlinks.html
  22. https://apod.nasa.gov/apod/lib/about_apod.html
  23. http://asterisk.apod.com/discuss_apod.php?date=211009
  24. https://apod.nasa.gov/apod/ap211010.html
  25. http://www.phy.mtu.edu/faculty/Nemiroff.html
  26. http://www.phy.mtu.edu/
  27. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html
  28. http://www.astro.umd.edu/
  29. https://apod.nasa.gov/apod/lib/about_apod.html#srapply
  30. https://www.nasa.gov/about/highlights/HP_Privacy.html
  31. https://astrophysics.gsfc.nasa.gov/
  32. https://www.nasa.gov/
  33. https://www.nasa.gov/centers/goddard/
  34. http://www.mtu.edu/