Hubble Confirms Huge   'Dirty Snowball' Nucleus

Comet With 85-Mile-Wide

NASA's Hubble Space Telescope team

Likens comets to dirty snowballs with spectacular multimillion-mile-long tails. Comets look fuzzy, but they have a packed nucleus of ice and dust.

Hubble has now confirmed

the largest comet nucleus ever discovered, a stunner of a snowball that could be 85 miles (137 kilometers) across.

Hubble is a joint project

of NASA and the European Space Agency. It often gazes at distant galaxies, but scientists were able to use it to help measure the nucleus of comet C/2014 UN271

Remember comet Neowise

which came close to Earth for a visit in 2020? Neowise's nucleus is about 3 miles (5 kilometers) in diameter.

The 4-billion-year-old comet

hailing from a theoretical distant comet "nesting ground" called the Oort Cloud  was first observed in 2010.

Hubble observations in 2022

were needed to discriminate the solid nucleus from the huge dusty shell enveloping it, with help from radio observations. That dusty shell is called a coma.

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