WHERE DID ALL THE SUNSPOTS GO? So far this year, the sun has been blank--without sunspots--76% of the time. That's verging on the Space Age record set just last year in 2019 when the sun was blank 77% of the time. This means Solar Minimum is still underway despite recent signs of life from the next solar cycle. Stay tuned for more quiet. Aurora alerts: SMS Text.
THE SIZE OF COMET ATLAS: No one knows how big the icy core of Comet ATLAS (C/2019 Y4) might be--possibly no wider than a few kilometers. One thing's for sure, though, the comet's atmosphere is huge. New images from amateur astronomers around the world show that ATLAS's gaseous envelope has ballooned in diameter to ~720,000 km--about half as wide as the sun.
"Comet ATLAS's coma (atmosphere) is approximately 15 arcminutes in diameter," reports Michael Jäger of Weißenkirchen, Austria, who took the picture, above, on March 18th. "Its newly-formed tail is about the same size."
Other astronomers are getting similar results. 15 arcminutes = a quarter of a degree. Given Comet ATLAS's distance of 1.1 AU on March 18th, that angle corresponds to a physical size of 720,000 km.
On the scale of big things in the solar system, Comet ATLAS falls somewhere between the sun (1,392,000 km diameter) and Jupiter (139,820 km). It's not unusual for comets to grow so large. While their icy solid cores are typically mere kilometers in diameter, they can spew prodigious amounts of gas and dust into space, filling enormous volumes. In the fall of 2007, Comet 17P/Holmes partially exploded and, for a while, had an atmosphere even larger than the sun. The Great Comet of 1811 also had a sun-sized coma. Whether Comet ATLAS will eventually rival those behemoths of the past remains to be seen.
Right now, Comet ATLAS is certainly the biggest green thing in the Solar System. Its verdant hue comes from diatomic carbon, C2, a molecule commonly found in comets. Gaseous C2 emits a beautiful green glow in the near-vacuum of space.
Currently, Comet ATLAS is shining like an 8th magnitude star--invisible to the unaided eye but an easy target for backyard telescopes. The comet is brightening rapidly as it comes closer to Earth and the sun. By late May it could rival Venus in the evening twilight sky. Stay tuned!
Comet ATLAS resources: sky map; 3D orbit; ephemeris, light curve.
Realtime Comet ATLAS Photo Gallery
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FAR-OUT MOTHER'S DAY GIFT: Every time the students of Earth to Sky Calculus launch cosmic ray sensors to the stratosphere, they send a little something extra along for the ride. For example, this Northern Lights pendant:
On Dec. 6, 2019, it flew 107,612 feet above the rugged Sierra Nevada mountains of central California.
You can have it for $129.95. The students are selling these pendants as a fund-raiser for their cosmic ray monitoring program. They make great anniversary, birthday and Mother's Day gifts. Each pendant comes with a greeting card showing the jewelry in flight and telling the story of its journey to the stratosphere and back again.
Far Out Gifts: Earth to Sky Store
All sales support hands-on STEM education
Realtime Space Weather Photo Gallery
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Realtime Aurora Photo Gallery
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