Cape Canaveral, Fla. (AP) — Comet streaks have traced our way back 50,000 years later.
Dirty Snowball was last visited during the days of Neanderthals, according to NASA. It will come within 26 million miles (42 million kilometers) of Earth on Wednesday before speeding away again, and is unlikely to return for millions of years.
So look up, in contrast to the Killer-Comet title “Don’t Look Up.”
Discovered less than a year ago, this harmless green comet is already visible in the northern night sky with binoculars, small telescopes, and possibly with the naked eye in the darkest corners of the Northern Hemisphere.
It is expected to lighten as it approaches and rise higher above the horizon until the end of January, and it is best seen in the predawn hours. By February 10th, it will be near Mars, which is a good landmark. Skygazers in the Southern Hemisphere will have to wait until next month to get a glimpse.
While a lot of comets have graced the sky over the past year, “it looks like this one probably looks a little bigger and therefore a little brighter, and it’s getting a little bit closer to Earth’s orbit,” said NASA asteroid and comet tracking expert Paul Chodas.
Green from all the carbon in the gas cloud, or coma, surrounding the nucleus, this long-period comet was discovered last March by astronomers using the Zwicky Transit Facility, a Wide Field Camera at Caltech’s Palomar Observatory.
That explains its onerous official name: Comet C/2022 E3 (ZTF).
On Wednesday, it will hurtle between the orbits of Earth and Mars at a relative speed of 128,500 mph (207,000 km). Their cores are thought to be about a mile (1.6 kilometers) wide, and their tails extend millions of miles (kilometers).
The comet is not expected to be nearly as bright as Neowise in 2020, or Hale-Bopp and Hyakutake in the mid-to-late 1990s.
“It will be bright thanks to its near-Earth pass…which allows scientists to do more experiments and publics to be able to see a beautiful comet,” Karen Meek, an astronomer at the University of Hawaii, said in an email.
Scientists are confident in their orbital calculations, which pinpoint the comet’s last swing through the solar system’s planetary neighborhood 50,000 years ago.
They don’t know how close it was to Earth or if it was visible even to Neanderthals, said Chodas, director of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory in California.
But when he returns, the verdict is even tougher.
Each time a comet passes the sun and planets, their gravitational tugs slightly alter the iceball’s trajectory, causing significant changes in trajectory over time. Another wild card: jets of dust and gas gushing from the comet as it heated up near the sun.
“We don’t know exactly how far they’re pushing this comet around,” Chodas said.
The comet – a time capsule from the nascent solar system 4.5 billion years ago – came from what is known as the Oort Cloud outside Pluto. This deep freeze haven for comets is thought to extend more than a quarter of the way to the next star.
Chodas said that while Comet ZTF originated in our solar system, we can’t be sure that it will remain there. He added that if he was expelled from the solar system, he would never return.
Don’t worry if you missed it.
“In the field of comets, you just have to wait for the next one because there are dozens of them,” Chodas said. “And the next one might be bigger, it might be brighter, it might be closer.”
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