September 13, 2025
On this day, the universe repeated one of its rarest tricks: it arranged dust, light, memory, and possibility into a person no equation...
Star Trails over One-Mile Radio Telescope
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APOD published September 13, 2025. Credit: Joao Yordanov Serralheiro. A publication-date match, not a photo taken on your date. Independent of NASA.
The steerable 60 foot diameter dish antenna of the One-Mile Telescope at Mullard Radio Astronomy Observatory, Cambridge, UK, is 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 rotation on its axis. The North Celestial Pole, the extension of Earth's axis of rotation into space, points near Polaris, the North Star. That's the bright star that creates the short trail near the center of the concentric arcs. But the historic One-Mile Telescope array also relied on planet Earth's rotation to operate. Exploring the universe at radio wavelengths, it was the first radio telescope to use Earth-rotation aperture synthesis. That technique uses the rotation of the Earth to change the relative orientation of the telescope array and celestial radio sources to create high resolution radio maps of the sky.
Image credit: Joao Yordanov Serralheiro