A comet is streaking back our way after 50,000 years.

The dirty snowball last visited during Neanderthal times, according to NASA. It will come within 26 million miles (42 million kilometers) of Earth Wednesday before speeding away again, unlikely to return for millions of years.

So do look up, contrary to the title of the killer-comet movie B次元官网网址淒onB次元官网网址檛 Look Up.B次元官网网址�

Discovered less than a year ago, this harmless green comet already is visible in the northern night sky with binoculars and small telescopes, and possibly the naked eye in the darkest corners of the Northern Hemisphere. ItB次元官网网址檚 expected to brighten as it draws closer and rises higher over the horizon through the end of January, best seen in the predawn hours. By Feb. 10, it will be near Mars, a good landmark.

Skygazers in the Southern Hemisphere will have to wait until next month for a glimpse.

While plenty of comets have graced the sky over the past year, B次元官网网址渢his one seems probably a little bit bigger and therefore a little bit brighter and itB次元官网网址檚 coming a little bit closer to the EarthB次元官网网址檚 orbit,B次元官网网址� said NASAB次元官网网址檚 comet and asteroid-tracking guru, 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 Transient Facility, a wide field camera at CaltechB次元官网网址檚 Palomar Observatory. That explains its official, cumbersome 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 kilometers). Its nucleus is thought to be about a mile (1.6 kilometers) across, with its tails extending millions of miles (kilometers).

The comet isnB次元官网网址檛 expected to be nearly as bright as Neowise in 2020, or Hale-Bopp and Hyakutake in the mid to late 1990s.

But B次元官网网址渋t will be bright by virtue of its close Earth passage B次元官网网址� which allows scientists to do more experiments and the public to be able to see a beautiful comet,B次元官网网址� University of Hawaii astronomer Karen Meech said in an email.

Scientists are confident in their orbital calculations putting the cometB次元官网网址檚 last swing through the solar systemB次元官网网址檚 planetary neighborhood at 50,000 years ago. But they donB次元官网网址檛 know how close it came to Earth or whether it was even visible to the Neanderthals, said Chodas, director of the Center for Near Earth Object Studies at NASAB次元官网网址檚 Jet Propulsion Laboratory in California.

When it returns, though, is tougher to judge.

Every time the comet skirts the sun and planets, their gravitational tugs alter the iceballB次元官网网址檚 path ever so slightly, leading to major course changes over time. Another wild card: jets of dust and gas streaming off the comet as it heats up near the sun.

B次元官网网址淲e donB次元官网网址檛 really know exactly how much they are pushing this comet around,B次元官网网址� Chodas said.

The comet B次元官网网址� a time capsule from the emerging solar system 4.5 billion years ago B次元官网网址� came from whatB次元官网网址檚 known as the Oort Cloud well beyond Pluto. This deep-freeze haven for comets is believed to stretch more than one-quarter of the way to the next star.

While comet ZTF originated in our solar system, we canB次元官网网址檛 be sure it will stay there, Chodas said. If it gets booted out of the solar system, it will never return, he added.

DonB次元官网网址檛 fret if you miss it.

B次元官网网址淚n the comet business, you just wait for the next one because there are dozens of these,B次元官网网址� Chodas said. B次元官网网址淎nd the next one might be bigger, might be brighter, might be closer.B次元官网网址�

B次元官网网址擬arcia Dunn, The Associated Press