¿ 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. 2020 July 8 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Mercury's Sodium Tail Image Credit & Copyright: [3]Andrea Alessandrini Explanation: What is that fuzzy streak extending from Mercury? Long exposures of our [4]Solar System's innermost planet may reveal something unexpected: a tail. [5]Mercury's thin [6]atmosphere contains small amounts of [7]sodium that glow when excited by light from the Sun. Sunlight also liberates these molecules from [8]Mercury's surface and pushes them away. The yellow glow from sodium, in particular, is relatively bright. Pictured, Mercury and its [9]sodium tail are visible in a deep image taken in late May from [10]Italy through a filter that primarily transmits [11]yellow light emitted by sodium. First [12]predicted in the 1980s, Mercury's tail was first [13]discovered in 2001. Many tail details were revealed in [14]multiple observations by [15]NASA's robotic [16]MESSENGER spacecraft that orbited Mercury between 2011 and 2015. [17]Tails are usually associated with [18]comets. The tails of [19]Comet NEOWISE are currently [20]visible with the unaided eye in the [21]morning sky. Comet NEOWISE from Around the Globe: [22]Notable Images Submitted to APOD Tomorrow's picture: open space __________________________________________________________________ [23]< | [24]Archive | [25]Submissions | [26]Index | [27]Search | [28]Calendar | [29]RSS | [30]Education | [31]About APOD | [32]Discuss | [33]> __________________________________________________________________ Authors & editors: [34]Robert Nemiroff ([35]MTU) & [36]Jerry Bonnell ([37]UMCP) NASA Official: Phillip Newman [38]Specific rights apply. [39]NASA Web Privacy Policy and Important Notices A service of: [40]ASD at [41]NASA / [42]GSFC & [43]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2007/MercuryTail_Alessandrini_1804.jpg 3. mailto:%20andrea-alessandrini%20@at@%20hotmail%20.dot.%20it 4. https://solarsystem.nasa.gov/planets/mercury/overview/ 5. https://apod.nasa.gov/apod/ap170723.html 6. https://en.wikipedia.org/wiki/Atmosphere_of_Mercury 7. https://en.wikipedia.org/wiki/Sodium 8. https://apod.nasa.gov/apod/ap110616.html 9. https://www.psi.edu/news/cover-pages/2018/mercurys-sodium-tail 10. https://en.wikipedia.org/wiki/Italy 11. https://www.youtube.com/watch?v=7u3rRy97m9Y 12. https://ui.adsabs.harvard.edu/abs/1986GeoRL..13..423I/abstract 13. https://ui.adsabs.harvard.edu/abs/2001mses.conf...77P/abstract 14. https://www.nasa.gov/image-feature/mercurys-sodium-tail 15. https://www.nasa.gov/ 16. https://www.nasa.gov/mission_pages/messenger/main/index.html 17. https://i.pinimg.com/originals/04/16/2e/04162ebbb47b9421cfceedf0908482d2.jpg 18. https://apod.nasa.gov/apod/ap200508.html 19. https://skyandtelescope.org/astronomy-news/anticipation-grows-for-comets-neowise-and-lemmon/ 20. https://www.universetoday.com/146455/comet-f3-neowise-may-perform-in-july/ 21. https://apod.nasa.gov/apod/ap200707.html 22. https://www.facebook.com/media/set?set=a.2741239435980258&type=3 23. https://apod.nasa.gov/apod/ap200707.html 24. https://apod.nasa.gov/apod/archivepix.html 25. https://apod.nasa.gov/apod/lib/apsubmit2015.html 26. https://apod.nasa.gov/apod/lib/aptree.html 27. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 28. https://apod.nasa.gov/apod/calendar/allyears.html 29. https://apod.nasa.gov/apod.rss 30. https://apod.nasa.gov/apod/lib/edlinks.html 31. https://apod.nasa.gov/apod/lib/about_apod.html 32. http://asterisk.apod.com/discuss_apod.php?date=200708 33. https://apod.nasa.gov/apod/ap200709.html 34. http://www.phy.mtu.edu/faculty/Nemiroff.html 35. http://www.phy.mtu.edu/ 36. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 37. http://www.astro.umd.edu/ 38. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 39. https://www.nasa.gov/about/highlights/HP_Privacy.html 40. https://astrophysics.gsfc.nasa.gov/ 41. https://www.nasa.gov/ 42. https://www.nasa.gov/centers/goddard/ 43. http://www.mtu.edu/