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 __________________________________________________________________ [14]< | [15]Archive | [16]Submissions | [17]Index | [18]Search | [19]Calendar | [20]RSS | [21]Education | [22]About APOD | [23]Discuss | [24]> __________________________________________________________________ Authors & editors: [25]Robert Nemiroff ([26]MTU) & [27]Jerry Bonnell ([28]UMCP) NASA Official: Phillip Newman [29]Specific rights apply. [30]NASA Web Privacy Policy and Important Notices 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/