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. 2025 September 13 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Star Trails over One-Mile Radio Telescope Image Credit & [3]Copyright: [4]Joao Yordanov Serralheiro Explanation: The steerable 60 foot diameter dish antenna of the One-Mile Telescope at [5]Mullard Radio Astronomy Observatory, Cambridge, UK, is [6]pointing skyward in this evocative night-skyscape. To capture the dramatic scene, consecutive 30 second exposures were recorded over a period of 90 minutes. Combined, the exposures reveal a background of gracefully arcing star trails that reflect planet Earth's daily [7]rotation on its axis. The [8]North Celestial Pole, the extension of Earth's axis of rotation into space, points near Polaris, the [9]North Star. That's the bright star that creates the short trail near the center of the [10]concentric arcs. But the [11]historic One-Mile Telescope array also relied on planet Earth's rotation to operate. Exploring the universe at [12]radio wavelengths, it was the first radio telescope to use Earth-rotation aperture synthesis. [13]That technique uses the rotation of the Earth to change the relative orientation of the telescope array and celestial radio sources to create [14]radio maps of the sky at a resolution better than that of the human eye. Tomorrow's picture: tilts and spins __________________________________________________________________ [15]< | [16]Archive | [17]Submissions | [18]Index | [19]Search | [20]Calendar | [21]RSS | [22]Education | [23]About APOD | [24]Discuss | [25]> __________________________________________________________________ Authors & editors: [26]Robert Nemiroff ([27]MTU) & [28]Jerry Bonnell ([29]UMCP) NASA Official: Amber Straughn [30]Specific rights apply. [31]NASA Web Privacy, [32]Accessibility, [33]Notices; A service of: [34]ASD at [35]NASA / [36]GSFC, [37]NASA Science Activation & [38]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2509/StarTrailsOne-MileRadioTelescope2100.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. https://www.joaoysphotography.com/about 5. https://en.wikipedia.org/wiki/Mullard_Radio_Astronomy_Observatory 6. https://www.joaoysphotography.com/portfolio?pgid=izo2cln4-f5684d4a-6f79-49cd-a911-84e93c45d8d0 7. https://apod.nasa.gov/apod/ap090909.html 8. https://apod.nasa.gov/apod/ap250605.html 9. https://apod.nasa.gov/apod/ap110514.html 10. https://apod.nasa.gov/apod/ap100212.html 11. https://en.wikipedia.org/wiki/One-Mile_Telescope 12. https://apod.nasa.gov/apod/ap180713.html 13. https://ui.adsabs.harvard.edu/abs/1973IEEEP..61.1211F/abstract 14. https://public.nrao.edu/vlass/ 15. https://apod.nasa.gov/apod/ap250912.html 16. https://apod.nasa.gov/apod/archivepix.html 17. https://apod.nasa.gov/apod/lib/apsubmit2015.html 18. https://apod.nasa.gov/apod/lib/aptree.html 19. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 20. https://apod.nasa.gov/apod/calendar/allyears.html 21. https://apod.com/feed.rss 22. https://apod.nasa.gov/apod/lib/edlinks.html 23. https://apod.nasa.gov/apod/lib/about_apod.html 24. https://asterisk.apod.com/discuss_apod.php?date=250913 25. https://apod.nasa.gov/apod/ap250914.html 26. http://www.phy.mtu.edu/faculty/Nemiroff.html 27. http://www.phy.mtu.edu/ 28. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 29. http://www.astro.umd.edu/ 30. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 31. https://www.nasa.gov/about/highlights/HP_Privacy.html 32. https://www.nasa.gov/general/accessibility/ 33. https://www.nasa.gov/privacy/ 34. https://astrophysics.gsfc.nasa.gov/ 35. https://www.nasa.gov/ 36. https://www.nasa.gov/centers/goddard/ 37. https://science.nasa.gov/learners 38. http://www.mtu.edu/