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. 2026 February 15 [2]An astronaut is seen hovering over the Earth. In the top part of the image, the astronaut is seen against the darkness of space. In the lower part of the image, the Earth is bright blue with white clouds. Please see the explanation for more detailed information. To Fly Free in Space Image Credit: [3]NASA, [4]STS-41B Explanation: What would it be like to fly free in space? About 100 meters from the cargo bay of a [5]space shuttle, Bruce McCandless II was living the dream -- floating farther out than anyone had ever been before. Guided by a [6]Manned Maneuvering Unit (MMU), astronaut McCandless, [7]pictured, was [8]floating free in space. During [9]Space Shuttle mission [10]41-B in 1984, [11]McCandless and fellow [12]NASA astronaut [13]Robert Stewart were the first to [14]experience such an "un[15]tethered [16]space walk". The [17]MMU worked by shooting jets of [18]nitrogen and was used to help deploy and [19]retrieve satellites. With a mass over 140 kilograms, an [20]MMU is heavy on [21]Earth, but, like everything, is weightless when drifting in orbit. The MMU was later replaced with the [22]SAFER backpack propulsion unit. Tomorrow's picture: unexplained shocks __________________________________________________________________ [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: Amber Straughn [38]Specific rights apply. [39]NASA Web Privacy, [40]Accessibility, [41]Notices; A service of: [42]ASD at [43]NASA / [44]GSFC, [45]NASA Science Activation & [46]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2602/freeflyer_nasa_3000.jpg 3. https://www.nasa.gov/ 4. https://www.nasa.gov/mission/sts-41b/ 5. https://www.nasa.gov/space-shuttle/ 6. https://en.wikipedia.org/wiki/Manned_Maneuvering_Unit 7. https://www.nasa.gov/image-feature/nasa-celebrates-50-years-of-spacewalking 8. https://youtu.be/RvnC--JjDBw 9. https://apod.nasa.gov/apod/ap990411.html 10. https://www.nasa.gov/mission/sts-41b/ 11. https://www.nasa.gov/press-release/astronaut-bruce-mccandless-ii-dies-at-80 12. https://www.nasa.gov/humans-in-space/astronauts/ 13. https://www.nasa.gov/wp-content/uploads/2023/03/stewart-robert.pdf 14. https://youtu.be/7K5DiKsZhTk 15. http://www-istp.gsfc.nasa.gov/Education/wtether.html 16. https://apod.nasa.gov/apod/ap990801.html 17. https://youtu.be/92ZRVlKuc0U 18. https://periodic.lanl.gov/7.shtml 19. https://apod.nasa.gov/apod/ap121209.html 20. http://en.wikipedia.org/wiki/Manned_Maneuvering_Unit 21. https://science.nasa.gov/earth/facts/ 22. https://apod.nasa.gov/apod/ap011002.html 23. https://apod.nasa.gov/apod/ap260214.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.com/feed.rss 30. https://apod.nasa.gov/apod/lib/edlinks.html 31. https://apod.nasa.gov/apod/lib/about_apod.html 32. https://asterisk.apod.com/discuss_apod.php?date=260215 33. https://apod.nasa.gov/apod/ap260216.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://www.nasa.gov/general/accessibility/ 41. https://www.nasa.gov/privacy/ 42. https://astrophysics.gsfc.nasa.gov/ 43. https://www.nasa.gov/ 44. https://www.nasa.gov/centers/goddard/ 45. https://science.nasa.gov/learners 46. http://www.mtu.edu/