Participate in a world-wide campaign to observe and photograph Comet 67P/C-G as it approaches and recedes from the Sun with Rosetta in tow. Your observations matter.

Comet recovered!
The fun begins! A team of astronomers recovered Comet 67P/C-G on April 14 after solar conjunction under difficult conditions (low altitude, moonlight) from Chile. It was magnitude 16.8.
Jean François Soulier, Jean Gabriel Bosch, CAO, San Pedro de Atacama

Just because there's a billion-dollar-plus spacecraft mission examining every nook and cranny of Rosetta's comet doesn't mean amateur astronomers can't play an important role in its study, too. To tap into the skills of amateurs and professionals alike, the Rosetta Worldwide Ground-based Observing Program was initiated last year.

At the time, Comet 67P/Churyumov-Gerasimenko was little more than a 23rd-magnitude blip. But now that the comet is emerging from solar conjunction and brightening, the campaign is moving into high gear. Time to dust off that scope!

You wouldn't think an 8-inch Dob under the quivering blanket of Earth's atmosphere could add to the our understanding of 67P/C-G, but amateurs have several advantages:

* They're not tied to a schedule or competing for time at a large observatory like most professional astronomers. Amateurs are free to spend as much time as needed making visual observations and sketches, taking comet photos, and recording spectra.

* Ground-based observations, both from amateurs and professionals, provide a "big picture" perspective complementing the up-close, in situ measurements from Rosetta.

* Astronomy hobbyists form a global network of sky enthusiasts. If there's a sudden change in a comet's behavior, amateurs are often among the first to report the news, alerting professionals to take a closer look with more powerful instruments.

* Amateurs can observe comets close to the Sun without fear of damaging the more sensitive instruments used by professional astronomers.

Campaign leads
Padma Yanamandra-Fisher (left) and Colin Snodgrass, the coordinators of the Comet 67P amateur and professional ground-based campaigns.
Courtesy photos

The two-pronged campaign will serve as a clearinghouse and database for amateurs and professionals alike. Colin Snodgrass, astronomer and planetary scientist at The Open University, heads up the pro side. NASA's Jet Propulsion Lab oversees the amateur campaign coordinated by Padma Yanamandra-Fisher, Senior Research Scientist at the Space Science Institute.

Yanamandra-Fisher was a key figure in the C/2012 S1 (ISON) and C/2013 A1 (Siding Spring) campaigns, working closely with amateurs to encourage them to share and contribute observations.

Having joined in both those earlier efforts, I can vouch for the participants' enthusiasm and excitement at being part of a group effort. All contributions were accepted: photos, magnitude estimates, maps, spectra, sketches, verbal descriptions, you name it. Not only did the data flow daily, but members were more than willing to answer questions or confirm an observation.

One puzzle piece at a time
Sketch of comet 67P showing a bright nucleus, compact coma, and short tail made during the December 1982 apparition. Even simple sketches like this one can help tell 67P's story.
Bob King

By following the stream of commentary and images, I not only learned more about comets but was able to compare my observations with others, sharpening my observing skills in the process.

Let's just say it was a blast, and I felt like my tiny contribution mattered. Yours will, too.  Amateur astronomers can sign up here for the new campaign. Once registered, you'll start receiving updates from your fellow observers at the PACA (Pro-Amateur Collaborative Astronomy) Rosetta67P Facebook group. You'll also contribute your observations there.

Professional astronomers can go to the Rosetta Campaign site or e-mail Colin Snodgrass.

67P is currently crossing from Aquarius into Pisces and just beginning to emerge from the solar glare for observers in the southern hemisphere. With an estimated magnitude at around +16, the comet will still be a very difficult object to see visually, but well within the range of amateur astrophotography. Solar elongation increases to 37° in mid-May with the comet a magnitude brighter and ripe for a portrait before the start of dawn.

En route to your eyes
Comet 67P/Churyumov-Gerasimenko's path during the time of best viewing from mid-July to November. The comet will be visible low in the eastern sky shortly before the start of dawn for observers across both hemispheres.
Chris Marriott's SkyMap

Northern skywatchers will have to be patient and have access to a good charting program that goes deep and has up-to-date orbital elements. By mid-July, 67P will have brightened to around magnitude +13.4 — within range of 8- and 10-inch telescopes from dark skies — and beckon early morning risers from its perch near the Hyades in Taurus some 10° high at dawn's start.

Light curve showing brightness estimates made by comet observers (black dots) and a prediction of Comet 67P's brightness from Seiichi Yoshida's Weekly Comet Information site. In this analysis, the comet may wax as bright as 11th magnitude. Periodic comets like 67P/C-G often lag in brightness early in an apparition and then brighten more quickly at and shortly after perihelion (purple line). Click image to visit the site.
Seiichi Yoshida

According to JPL's Horizons site and magnitudes based on orbital elements from the Minor Planet Center, the comet continues gaining altitude, passing perihelion on August 13 in Gemini with a peak brightness around magnitude +13. Or maybe not. Comets are notorious for ignoring predictions, so who knows how bright 67P might become?

Solar snap the whip
The portion of Comet 67P/C-G's orbit when things really start to heat up. Notice the descriptive temperature indicators. Perihelion occurs on August 13.

67P tracks from Cancer through Leo as summer mellows into fall, slowly fading as it departs both Sun and Earth. Come mid-December, the comet will return to its slumbers at magnitude +15. With your eyes, telescope and camera, you can help tell its story while playing a part in one of humanity's grandest adventures.

Learn the Secrets of Stargazing from expert observer Becky Ramotowski!


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