The first thing to know about a new comet that has appeared in the evening sky is that it's one big ice ball: about 5 kilometers (3.1 miles) across.
"Just to put it into context, about 65 million years ago there was an asteroid or a comet that was thought to have caused the extinction of the dinosaurs," says astronomer Amy Mainzer. "That object is thought to have been about 5 to 10 kilometers across."
Mainzer is principal investigator for a NASA mission known as NEOWISE that is seeking to spot comets and asteroids that could wipe out life as we know it on Earth.
And NEOWISE did spot this comet in March.
And 2020 has been a terrible year so far.
But don't worry, she says: "It's definitely not going to hit the Earth."
Instead, the comet, known officially as C/2020 F3 (NEOWISE) — or just comet Neowise for short — is providing an unexpected bright spot in the lives of quarantined astronomers. It came from a dark part of the solar system known as the Oort Cloud — an icy graveyard billions of miles out that is filled with ancient comets and asteroids. It shot into the inner solar system, and astronomers watched as it passed the sun at a distance closer than the planet Mercury.
"Of course, the question we asked was, 'Will it survive? Or is the sun going to melt it like an ice cube on a Tucson summer day?' " says Mainzer, a professor at the University of Arizona.
It did survive, thanks in large part to its size, and is now passing near Earth. Mainzer says the wanderer appears to be very rich in carbon, making it almost sooty in appearance if you were up close. But the sun's rays are making it visible, even to the naked eye.
"It looks at first like a little fuzzy dot, and then you'll notice that it has this long streaky tail sticking off of it," she says.
Until this week, the comet was visible only to early birds willing to rise before dawn. But now it's appearing in the evening, mainly in the Northern Hemisphere. To find it, go outside just after dark and look to the northwest, below the Big Dipper. It appears close to the horizon right now, but it will start to rise higher in the sky in the coming days. Here's more on how to find it.
Mainzer says she can't predict how long the comet will remain visible. Its brightness depends on its distance from the sun and Earth, as well as its composition. But while it's here, she finds it to be comforting to look at.
"In spite of the really difficult times right now, it's a reminder that we're part of a bigger universe," she says. "And there are some really wonderful and beautiful things in it."
A previous version of this story misspelled Amy Mainzer's last name as Mainzen.
AILSA CHANG, HOST:
The night sky is putting on a show this month. A new comet is whizzing by the Earth, and it should be easily visible for those of us in the Northern Hemisphere. NPR's Geoff Brumfiel has more on how to see it.
GEOFF BRUMFIEL, BYLINE: The comet was spotted by a NASA satellite called NEOWISE. Amy Mainzer is the principal investigator in charge. She says the main job of NEOWISE is to hunt for things that might smash into Earth.
AMY MAINZER: It's a mission that's orbiting the Earth, but it's looking out into space right now in an effort to characterize asteroids and comets that can come close to the Earth and be potential impactors (ph).
BRUMFIEL: Given the way 2020 has gone so far, what do you think the odds are that we're going to get killed by an asteroid or comet? Just lay it - tell it to me straight.
MAINZER: (Laughter) Let's put it this way - the odds in any given year are very, very, very tiny. That said, we're keeping our eyes peeled.
BRUMFIEL: And that's how they found this new comet back in March. It came in from the outer solar system and passed really close to the sun. Now it's passing the Earth on its way back out.
MAINZER: This is a pretty big comet. This thing is 5 kilometers across. And just to put it into context, you know, a long time ago, about 65 million years ago, there was an asteroid or a comet that is thought to have caused the extinction of the dinosaurs, and that object is thought to have been about 5 to 10 kilometers across.
BRUMFIEL: Again, you can cross this one off your worry list.
MAINZER: It's definitely not going to hit the Earth.
BRUMFIEL: What it is doing is putting on quite a show for anyone who cares to see it.
MAINZER: It looks at first like a little fuzzy dot, and then you'll notice that it has this long, streaky tail sticking off of it.
BRUMFIEL: To find it, go outside just after dark and look to the northwest. It's below the Big Dipper, close to the horizon right now, but it will start to appear higher in the sky in coming days. Mainzer says she finds it comforting to look at.
MAINZER: You know, in spite of the really difficult times right now, it's really a reminder that we're part of a bigger universe, and there are some really wonderful and beautiful things in it.
BRUMFIEL: Mainzer says she doesn't know exactly how long this comet will be visible. So go see it while you can.
Geoff Brumfiel, NPR News.
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