Astronomy EssentialsSpace

Heads up! Famous comet 67P/C-G nearly closest

Star chart of the Gemini constellation with short line showing path of comet with dates along it.
This chart faces east around 11:30 p.m. CDT from October 28, 2021, to November 9, 2021. At that time, the comet is in front of the constellation Gemini the Twins. Illustration by Eddie Irizarry/ Stellarium.

Famous comet 67P is approaching

Comet 67P/Churyumov-Gerasimenko is gearing up for its closest approach to Earth on November 11 and 12, 2021. On October 26, the waning gibbous moon and the comet are in virtually the same location in Gemini, so the comet will be tough to see. But then the moon will move on, and, by November 8, the comet will pass very near to Pollux, the brighter of the two Twin stars. At its closest, the comet will pass more than 38 million miles (61 million km) from Earth. That’s still between the orbits of Earth and Mars. And it’s 67P’s closest approach for the next 193 years, until the year 2214.

Comet 67P’s 2021 perihelion – closest point to the sun – will take place on November 3. Its exact time of closest approach to Earth is November 12, 2021, at 00:50 UTC on November 12 (translate UTC to your time).

Comet 67P/C-G is one of the best-studied comets. The European Space Agency’s Rosetta spacecraft rendezvoused with it in August of 2014. Before the year ended, in a first, the mission had sent its Philae lander to the comet’s surface. Overall, the spacecraft traveled with the comet for two years.

67P/Churyumov-Gerasimenko is an ordinary comet, with a close orbit around the sun. Soviet astronomers Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko discovered it on October 22, 1969. It requires only 6.43 years to orbit the sun once, making it an attractive target for spacecraft. Its nucleus is an estimated 2.6 miles (4.2 km) wide. Like many of the small, icy comets in our solar system, 67P has two distinct lobes. Astronomers believe double-lobed comets like this one formed during slow collisions of icy debris in the early stages of our solar system’s formation, some 4.5 billion years ago.

Dense star field with two distinct bunches of stars, and a small, elongated fuzzy green object.
This beautiful image shows famous Comet 67P/Churyumov-Gerasimenko passing close to open cluster Messier 35 (left) and distant cluster NGC 2158 (lower right) on October 16, 2021. Image from San German, Puerto Rico, via Raymond Negron/ Sociedad Astronomia del Caribe. Thanks, Raymond!
Famous Comet 67P: Backlit two-lobed object with straight streamers of glowing gas coming from it.
Double-lobed comet 67P/Churyumov-Gerasimenko as captured on March 27, 2016, when the Rosetta spacecraft was only about 200 miles (329 km) away. Via ESA/ Rosetta/ NavCam/ NASA.

Rosetta’s visit to 67P

ESA’s Rosetta spacecraft mission – named for the Rosetta Stone that was an invaluable tool for deciphering ancient Egyptian scripts – was a ground-breaking comet mission. It was the first to include an orbiter that accompanied the comet as it sped through space for a year prior to its August 2015 perihelion (closest point to the sun).

The spacecraft also stayed with the comet for a second year, after perihelion, as it began heading outward away from the sun again. The Rosetta mission’s lander was named Philae for an ancient Egyptian obelisk. When Philae landed on the surface of 67P on November 12, 2014, it was the first spacecraft ever to land on a comet. Philae landed in one piece, but bounced in the comet’s low gravity. They found it a month later.

All in all, it’s hard to overstate the impact of the Rosetta mission on our knowledge of comets. Much of what scientists thought was true about them did prove true. For example, we had long pictured gases venting from a comet’s small nucleus as its orbit brought closer to the sun. But to see the gases venting from comet 67P’s nucleus in images from Rosetta … it was beautiful and wonderful!

Closeup of rough-surfaced double-lobed comet, with a single stream of gas jetting from it.
A jet erupting from comet 67P/ Churyumov-Gerasimenko. Image via ESA’s Rosetta spacecraft/ NASA.
Fuzzy green comet 67P/C-G with a greenish-tinted tail stretching out to the right, among scattered stars.
Comet 67P/Churyumov–Gerasimenko photographed on September 6, 2021, with an 8-inch diameter telescope by Raymond Negron from his back yard in San German, Puerto Rico. Thank you, Raymond!

How to see famous comet 67P

Although the comet is gradually brightening, unfortunately it won’t get bright enough to see with the unaided eye at its 2021 sweep past Earth. But, at its brightest, it will be around magnitude 9 to 10, well within the reach of visual observations using amateur telescopes, and an easy target for small telescopes equipped with cameras.

Comet 67P/Churyumov-Gerasimenko will be fascinating to view in backyard telescopes. As you gaze upon it, you’ll know this chunk of rock and ice has been visited by a robot spacecraft, sent by humanity. The charts below can help you find comet 67P.

Chart of sky with constellations and path of comet in green across it.
View larger. | Dominic Ford’s great website has a detailed page for observers with telescopes who wish to see comet 67P G-C from now through February 2022.
Star chart with the region around Orion and Gemini, labeled to pinpoint comet 67P.
This chart faces east at 11:30 p.m. CDT on the night of the 67P’s closest approach to Earth (November 11-12, 2021). Gemini’s brightest stars, Castor and Pollux, will help to locate the celestial visitor, as they’ll form an arc with the comet. Illustration by Eddie Irizarry/ Stellarium.
Star chart of Gemini region with labeled reference stars and tick marks at location of comet 67P.
A closer view, facing East around 11:30 p.m. CDT on November 11, 2021. Observers using a computerized or “GoTo” telescope can easily locate Comet 67P on the night of closest approach by pointing the instrument at one of these reference stars. Illustration by Eddie Irizarry/ Stellarium.
Colorful concentric circles depicting planetary orbits around the sun, with a parabola, the path of comet 67P.
Orbit of comet 67P shows its location during closest approach to Earth on November 11-12, 2021. Image via NASA/JPL.

Holding out for a bright comet?

Still waiting for a good binocular comet or perhaps even a comet visible to the eye alone?  Another comet, C/2021 A1 (Leonard), might become this year’s brightest comet. More details on Comet Leonard here.

Bottom line: Famous comet 67P/Churyumov-Gerasimenko will sweep closest to Earth on November 11 to 12. Finder charts here will help you locate this comet before it leaves for another 193 years.

October 26, 2021
Astronomy Essentials

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