Close-Up View of Comet NEOWISE Shows It Survived Close Encounter With Sun

A close-up view of Comet NEOWISE, taken by Hubble on August 8. (Image: NASA, ESA, Q. Zhang (Caltech), and A. Pagan (STScI)
A close-up view of Comet NEOWISE, taken by Hubble on August 8. (Image: NASA, ESA, Q. Zhang (Caltech), and A. Pagan (STScI)

Comets don’t always survive their sojourns into the inner solar system, but a new close-up image suggests the NEOWISE comet — the brightest in decades — has kept it together.

Some 6,800 years from now, our descendants, should they still be around, can expect a return visit from comet NEOWISE. This 5 km-wide comet appears to have survived its recent trip around the Sun, as revealed by a new close-up image taken by the Hubble Space Telescope. Its solid core remains intact, pointing to a potential return thousands of years from now.

This comet, formally known as C/2020 F3 (NEOWISE), was first spotted this past March, and it turned out to be the brightest comet seen in the Northern Hemisphere since Hale-Bopp in 1997. NEOWISE was visible to the naked eye from early July until mid-August and made its closest approach to the Sun on July 3, coming to within 43 million km, or just inside Mercury’s orbit. The comet is now speeding back toward the outer solar system at around 60 km per second.

NEOWISE comet as seen from the ground on July 18, and the new close-up image, inset, taken by Hubble on August 8. (Image: NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI), and Z. Levay)

The solid icy core, or nucleus, can’t actually be seen in the new photo, which was taken on August 8, but the image does show some of the gas and dust pouring out from the comet, forming a cloud that measures around 18,000 km across. This marks the “the first time Hubble has photographed a comet of this brightness at such resolution after this close of a pass by the Sun,” according to a Hubble press release.

Comets are best described as gigantic dirty snowballs that formed ages ago in the outer solar system. When close to the Sun, they enter into a temporary active state, resulting in a bright coma and jets shooting off from the surface, forming a long cometary tail.

Video showing the rotation of Comet NEOWISE shortly after it passed by the Sun. These two frames were taken three hours apart on August 8. The pair of jets emerging from the nucleus are being fanned out by the comet's rotation. (Gif: NASA, ESA, Q. Zhang (Caltech), and A. Pagan (STScI)

Some comets don’t survive these encounters, disintegrating on account of heat and gravitational pressures. This happened to Comet ISON in 2013 and more recently to C/2019 Y4 ATLAS, which was supposed to be the brightest comet in decades. Astronomers weren’t sure if the same fate might befall comet NEOWISE.

To find out, Caltech graduate student Qicheng Zhang, along with colleagues, captured the new image of NEOWISE comet, revealing no discernible signs of fragmentation.

“Hubble has far better resolution than we can get with any other telescope of this comet,” explained Zhang in the Hubble press release. “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.”

Astronomers will now carefully track any changes to the comet as it moves further away from the Sun, including changes to colour of its dust. Ultimately, scientists want a better understanding of how solar heating affects the material within the comet and its chemical composition.