Astronomy Picture of the Day

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.

2024 May 11
The Sun is shown in black and white showing dark
sunspots on the far right. The large sunspot group is
expanded in an inset image at the bottom left.
Please see the explanation for more detailed information.

AR 3664: Giant Sunspot Group
Image Credit & Copyright: Franco Fantasia & Guiseppe Conzo (Gruppo Astrofili Palidoro)

Explanation: Right now, one of the largest sunspot groups in recent history is crossing the Sun. Active Region 3664 is not only big -- it's violent, throwing off clouds of particles into the Solar System. Some of these CMEs are already impacting the Earth, and others might follow. At the extreme, these solar storms could cause some Earth-orbiting satellites to malfunction, the Earth's atmosphere to slightly distort, and electrical power grids to surge. When impacting Earth's upper atmosphere, these particles can produce beautiful aurorae, with some aurorae already being reported unusually far south. Pictured here, AR3664 and its dark sunspots were captured yesterday in visible light from Rome, Italy. The AR3664 sunspot group is so large that it is visible just with glasses designed to view last month's total solar eclipse. This weekend, skygazing enthusiasts will be keenly watching the night skies all over the globe for bright and unusual aurorae.

Gallery: Active Region 3664 on the Sun and Associated Aurora
Tomorrow's picture: active sky


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