This summer we were (finally) treated to a spectacular, naked-eye comet, C/2020 F3 NEOWISE. And while seeing it with our own eyes was a joy, it was incredible to see the varied photos of NEOWISE taken by people around the world, showing the comet’s long gossamer tails, filled with detail and color. (See our gallery of images here.)
Now, the Hubble Space Telescope has released a high-resolution image of NEOWISE. However, it might not be the view you may have expected.
Instead of focusing on the comet’s beautiful tails, Hubble zeroed in on coma, the shell of gas and dust that surrounds its nucleus, which expands and changes as it is heated by the Sun. NASA says this is the first time Hubble has photographed a comet of this brightness at such high resolution after this close of a pass to the Sun.
“Hubble has far better resolution than we can get with any other telescope of this comet,” said lead researcher Qicheng Zhang of Caltech in Pasadena, California. “That resolution is very key for seeing details very close to the nucleus. It lets us see changes in the dust right after it’s stripped from that nucleus due to solar heat, sampling dust as close to the original properties of the comet as possible.”
The image was taken by Hubble on August 8, 2020. The great part is that the nucleus appears to have stayed intact, even after its closest approach to the Sun, which was in early July, at a distance of 27 million miles (43 million kilometers). Comets have a tendency to break apart due to thermal and gravitational stresses at such close encounters.
The lead image shows a ground-based image of comet C/2020 F3 (NEOWISE) taken from the Northern Hemisphere on July 16, 2020 (taken by retired Hubble image processing team guru Zolt Levay), with an inset of the Hubble image.
Even before Hubble launched, Zolt Levay was instrumental in developing software to translate Hubble data into images for analysis. He refined techniques into an artform, of taking data from the various filters on Hubble and turning them into beautiful photos that not only were pleasing to the eye, but also told the science story of the objects in the images.
So, here’s the science of this image: Even though the nucleus is to small to be seen, astronomers estimate it measures no more than 3 miles (4.8 kilometers) across. So, the Hubble image shows a portion of the comet’s coma, the fuzzy glow, which measures about 11,000 miles (18,000 kilometers) across in this image.
Hubble scientists explained that the two structures appearing on the left and right sides of the comet’s center are jets made up of ice sublimating from beneath the surface of the nucleus, with the resulting dust and gas being squeezed through at a high velocity. The jets emerge as cone-like structures, then are fanned out by the rotation of comet NEOWISE’s nucleus.
So, while this photo may not be a “stunner” that we’ve become accustomed to with Hubble, the details in the image data will help reveal the color of the comet’s dust and how those colors change as the comet moves away from the Sun. This, in turn, may explain how solar heat affects the composition and structure of that dust in the comet’s coma. Scientists say the ultimate goal here would be to learn the original properties of the dust to learn more about the conditions of the early solar system in which it formed.
Comet NEOWISE is now speeding away towards the outer solar system, traveling at a whopping 144,000 miles per hour (over 230,000 km/h). It will not return to grace our skies again for nearly 7,000 years.
Farewell Comet NEOWISE, and we thank you.
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