While all the rest of us were out looking at Comet Neowise earlier this summer with our scopes, binoculars, and—in some places—the unaided eye, Hubble Space Telescope took a close-up look. It orbits high above Earth’s atmosphere.
On August 8th, the telescope focused on the nucleus of the comet. The coma hid the actual surface of NEOWISE, and there’s no way HST could study something that small at a distance of 43 million kilometers. But, that wasn’t what astronomers were looking for. They wanted to check out details of the coma.
What’s to See at Comet NEOWISE?
From Earth, NEOWISE looked like a streak of light across the sky. We saw two tails stretching out from the coma. All that, thanks to the nucleus—a chunk of ice mixed with dust that is about 4.8 kilometers across. Normally, these objects stick to the cold, outer regions of the solar system. That’s where their ices remain safely frozen. But, if they get knocked into an orbit that brings them close to the Sun, things change.
As any comet, including NEOWISE, nears the Sun, it starts to sublimate (like dry ice on a hot sidewalk. That’s due to the increasing heat it ...