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 March 18
A comet is pictured with a really long and wavy ion tail.
The front of the comet -- its coma -- appears to be a spiral.
The coma is green, the tail is faint blue, and part of the 
swirl is red.
Please see the explanation for more detailed information.

Comet Pons-Brooks' Swirling Coma
Image Credit & Copyright: Jan Erik Vallestad

Explanation: A bright comet will be visible during next month's total solar eclipse. This very unusual coincidence occurs because Comet 12P/Pons-Brooks's return to the inner Solar System places it by chance only 25 degrees away from the Sun during Earth's April 8 total solar eclipse. Currently the comet is just on the edge of visibility to the unaided eye, best visible with binoculars in the early evening sky toward the the constellation of the Fish (Pisces). Comet Pons-Brooks, though, is putting on quite a show for deep camera images even now. The featured image is a composite of three very specific colors, showing the comet's ever-changing ion tail in light blue, its outer coma in green, and highlights some red-glowing gas around the coma in a spiral. The spiral is thought to be caused by gas being expelled by the slowly rotating nucleus of the giant iceberg comet. Although it is always difficult to predict the future brightness of comets, Comet Pons-Brook has been particularly prone to outbursts, making it even more difficult to predict how bright it will actually be as the Moon moves in front of the Sun on April 8.

Total Eclipse Info: 2024 Total Solar Eclipse from NASA
Tomorrow's picture: sounding out a cosmic jellyfish

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