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RIP Comet Leonard: Brightest comet to whiz past Earth in 2021 is now a blur of dust.

Comet Leonard, shown here on Dec. 4, 2021, was the brightest comet to whiz past Earth that year. (Image credit: Franco Tognarini/Getty Images)
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The brightest comet to whiz past Earth in 2021 has likely disintegrated. 

Comet Leonard is now nothing but a ghostly streak, having lost its nucleus, or main body, and its coma, or temporary atmosphere, according to EarthSky magazine (opens in new tab). The comet, first noticed by planetary science researcher Gregory Leonard of the Catalina Sky Survey in Arizona, survived barely a year after its discovery. 

Though the comet is gone, it will be fondly remembered, both by scientists who hope to learn something from its breakup and by its discoverer. 

"[F]or me this comet and its apparition have been an unimagined dream come true," Leonard wrote in an email to EarthSky. 

Related: Why are asteroids and comets such weird shapes?

The life of a comet

Leonard discovered the comet that bears his name on Jan. 3, 2021. The discovery was inadvertent, Leonard told Live Science's sister site Space.com (opens in new tab); in December 2020, he was doing a routine survey for near-Earth asteroids when he spotted something too fuzzy to be an asteroid. What he was seeing was the coma, the thin asteroid that forms around the icy comet nucleus as it nears the sun and heats up.

The comet likely came from the Oort cloud, a spherical cluster of icy and rocky bodies thought to hover outside the solar system at 2,000 times the distance between the sun and Earth. 

Comet Leonard is just one of 13 comets that Leonard had discovered as of December 2021, but it was special because its orbit brought it close enough to Earth for it to be spotted with a backyard telescope or binoculars. The comet made its closest pass by Earth on Dec. 12, 2021. And it behaved oddly: As it approached the sun, it should have brightened as it warmed, with gas and dust streaming from its surface. Instead, it became dimmer in November 2021, likely because it began boiling off water instead of carbon dioxide, according to EarthSky. 

But just as some astronomers were questioning whether the comet would be a dud, it came to life again, brightening and developing a dramatic twisted tail as it interacted with the wind of charged particles streaming from the sun. 

The end of Comet Leonard

After this last hurrah, though, Comet Leonard — also known as Comet C/2021 A1 — approached perihelion, or its closest point in its orbit to the sun, on Jan. 3, 2022, coincidentally a year to the day after it was first discovered. As it got close, the comet began to fluctuate in brightness. At this point, Comet Leonard was no longer visible from the Northern Hemisphere but could be seen from the Southern Hemisphere.

On Feb. 23, Czech Academy of Sciences telescope operator Martin Mašek noticed that the comet's nucleus was looking decidedly ghostly, according to EarthSky. Unlike in late 2021, Comet Leonard was really breaking up. Its approximately 1-mile-wide (1.6 kilometers) nucleus had either disintegrated or evaporated. Telescope imagery soon showed nothing but a vague smear across the night sky. 

Scientists may still learn from the quirky way Comet Leonard moved through space on its final voyage, Leonard told EarthSky. It will also be remembered for its final dramatic show. 

"It will be known for the appearance of the tails, some of the best ever observed," he said.

Originally published on Live Science. 

Stephanie Pappas
Live Science Contributor

Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.