A rare green comet, last seen in Earth’s skies 50,000 years ago, is revisiting our solar system and may become visible to the naked eye in our northern skies this week.
Observers withbinoculars and small telescopes are already starting to see it.
The comet – formally identified as C/2022 E3 (ZTF)but commonly called the "green comet" – won't be as bright as other famous comets such as Halley's or Hale-Bopp.
"The brightness of comets is notoriously unpredictable, but by (Feb. 1) C/2022 E3 (ZTF) could become only just visible to the eye in dark night skies," NASA said in its blog.
There's no guarantee, but the best chance of seeing it with your own eyesis a clear dark sky before dawn without thelight pollution of cities.
Otherwise, the comet "will more likely look like a smudge in the sky, like someone has dipped their finger in chalk dust and dabbed it on a blackboard," the BBC said.
The comet isa once-in-a-lifetime event generating excitement among astronomers and amateur skywatchers for its unique color and because it's a long-period comet, one that takes more than 200 years to orbit the sun. (Short-period comets take less than 200 years.)
Observers at the Palomar Observatory in California discovered it on March 3, 2022, inside the orbit of Jupiter nearly 400 million miles from the sun. Since then it has traveled sunward and reached perihelion, its closest orbital point to the sun, on Jan. 12.
It will come closest toEarth between Wednesday and Thursday, passing at a distance of about 26 million miles. By comparison, the moon is about 239,000 miles from Earth.
The green comet's path
Green comets are rare, but we've seen them at times. One of themwas Comet ISON, which visited Earth in 2013. ISON and C/2022 E3 (ZTF) are believed to have originated in the distantOort Cloud, a giant bubble of space debris containing billons of icy objects, some of them larger than mountains.
The cloud is so far away its distance is measured in astronomical units, or AUs. One AU is 93 million miles, the distance from the Earth to the sun. The edge of the Oort Cloud is estimated at 2,000 to 5,000 AUs from the sun.
If the 50,000-year visitation is accurate, the comet was last here in the Upper PaleolithicAge, when hom*o sapiens began replacing other human species such as Neanderthals and Denisovans.
Why is this comet green?
Comets are cosmic snowballs with ice, frozen gases, rocks and dust that range in size from a few miles to tens of miles in diameter.
Comets are frozen but warm up as they approach the sun and start spewing gases and dust particles, which createsa large glow around the head, called a coma, and formsa tail millions of miles long.
C/2022 E3 (ZTF)'s color comes from its molecular composition. It has dicarbon molecules, chemical compounds with two bonded carbon atoms, and cyanogen. Both of these glow green when exposed to sunlight.
Where to look for the green comet in the pre-dawnsky
Best times to view the comet
It can be challenging to predictwhen and if comets will become brighter as they approach Earth. We don't know yet if the green comet will be visible to the unaided eye.
Even if C/2022 E3 (ZTF) doesn't become bright enough to be seen without help, it can still be seen during the last days of January and the first few days of February with binoculars and small telescopes.
Viewers in the Northern Hemisphere have the best chance of seeing the comet in pre-dawn hours.
How to decipher the comet's name code
The International Astronomical Union names comets with a code that looks complicatedat first, but breaks down like this:
C=Length of time to orbit sun
The "C" in the code prefix doesn't stand for "comet." Instead, it identifiesthe comet as a non-periodic one that takes more than 200 years to orbit the sun.
Other prefixes include:
- P:Periodic (or short-period) cometwith solar orbitof less than 200 years.
- A:Asteroid or minor planet that was previously identified as a comet.
- X: Comet whose orbit can't be computed.
- D: Periodic comet that no longer exists or has disappeared.
- I: Interstellar object.
Year of discovery
Next is the year in which the comet was first seen.
Month it was found
The letter/number combination indicates the month of discovery.
- Letter:The IAU divides months into two halves and assigns letters A through Yto identify each. Jan. 1-15 is "A" and Jan. 16-31 is "B," for example. (The letter "I" is not used to avoid confusion with the number 1. "Z" isn't used, either.)
- Number:Showsthe order in which the comet was found in the half-month of its discovery.
Accordingly, "E3" identifies C/2022 E3 (ZTF) as the third comet discovered in the first half of March 2022.
(Who discovered the comet)
Finally, the comet's discoverer is listed in parenthesis. The Zwicky Transient Facility at the Palomar Observatory near San Diego, which discoveredC/2022 E3 (ZTF),uses a powerful camera to scan and recordthe northern sky every two days. The images are comparedto collect data on stars, comets, asteroids and other celestial objects.
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SOURCE USA TODAY Network reporting and research; Associated Press; NASA; Jet Propulsion Laboratory; space.com; earthsky.org; universetoday.com; International Astronomical Union; Las Cumbres Observatory; minorplanetcenter.net; theskylive.com
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