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Comet Churyumov-Gerasimenko

Discovery of Comet Churyumov-Gerasimenko (67P)

Image of Comet Churyumov-Gerasimenko

Credit: ESO's Very Large Telescope

(October 15, 2013)

In 1969, several astronomers visited the Alma-Ata Astrophysical Institute in Kazakhstan to study comets. On September 20, 1969, Klim Ivanovych Churyumov spotted a comet in a photograph taken by Svetlana Gerasimenko, nine days earlier. Its apparent magnitude was 13.

Initially, it was thought that the comet was 32P/Comet Solas. However, Comet Solas, although faint, was captured in the photograph about 1.8 degrees of sky away from this new comet. It was named Churyumov-Gerasimenko for its discover and the photographer.

Contents:

Size of Churyumov-Gerasimenko

In 2003, the Hubble Space Telescope observed 67P/Churyumov-Gerasimenko. Based on these observations astronomers determined that the nucleus of Comet Churyumov-Gerasimenko is 3 x 2 miles wide (5 x 3 kilometers) and takes 12 hours and 42 minutes to complete one rotation. The axis is tilted roughly 40 degrees.

The Orbit of Comet 67P / Churyumov-Gerasimenko

The comet was spotted in 1969, 1976, 1982, 1989, 1996, 2002 and 2009. After it was determined that this comet took 6.45 years to complete one orbit of the Sun, it received the designation 67P/Churyumov-Gerasimenko—meaning it was the sixty-seventh comet in history to have its periodic orbit determined. Halley's Comet was the first.

It is Jupiter-Family Comet—a comet prevented from returning to the Kuiper Belt by the orbit of Jupiter centuries or millennia ago. It is a Near-Earth Object, meaning it can approach Earth within 1 AU.

Comet orbits change when they pass close to a planet or moon. Jupiter, as the largest planet in our solar system, is the largest "perturber". Near-passes by this giant bring comets further into the solar system. Astrophysicists rewound the clock on this comet and suggest that, up until 1840, 67P/Churyumov-Gerasimenko didn't get any closer than 4.0 AU from the Sun. The Sun could not heat its nucleus, at this distance, and therefore the comet remained invisible to astronomers on Earth. In 1840, a close pass by Jupiter decreased the perihelion to 3.0 AU. Over the next 100 years, the perihelion decreased further to 2.77 AU and the comet took 9.3 years to orbit the Sun.

According to astronomer Kazuo Kinoshita, in February 1959, Comet Churyumov-Gerasimenko once again passed close to Jupiter and its perihelion decreased to 1.243 AU. As mentioned above, this comet now takes 6.45 years to orbit the Sun.

The Orbital Path of Comet Churyumov–Gerasimenko

Credit: JPL

The Rosetta Spacecraft - Landing on Comet Churyumov-Gerasimenko

In November of 1993, the European Space Agency's Science Programme Committee approved the Rosetta Mission. The mission was to study Comet 46P/Wirtanen. However, after the launch was delayed, Comet 67P/Churyumov-Gerasimenko became the target.

On March 2, 2004 the European Space Agency launched the Rosetta Spacecraft aboard an Ariane 5 rocket from Kourou, French Guian. Its mission was to study Comet Churyumov-Gerasimenko, a 3 x 5-kilometer wide Jupiter Family Comet that orbits the Sun once every 6.45 years. After three close fly-bys of Earth and one on Mars, the comet had an elongated orbit and was stalking Rosetta. With each passing day, Comet Churyumov-Gerasimenko closed the distance to Rosetta. Once it and the comet were in a stable orbit, Rosetta was put into hibernation on June 8, 2011. With the exception of heating, all functionality was powered off.

On January 20, 2014 Rosetta was woken from its nearly three-year hibernation near the orbit of Jupiter. "This was one alarm clock not to hit snooze on, and after a tense day we are absolutely delighted to have our spacecraft awake and back online," said Fred Jansen, Rosetta mission manager. ESA also had a "Wake Up, Rosetta" video contest, encouraging citizens to make entertaining videos in which they said, "Wake up Rosetta!"

Shortly after waking up, Rosetta imaged Comet Churyumov-Gerasimenko for the first time since it awoke from hibernation. It captured the comet using its two cameras, the Wide-Angle Camera and the OSIRIS Narrow Angle Camera, while the comet was 3.1 million miles away (5 million kilometers) in the constellation Ophiuchus. The two cameras were developed in Germany by the Max Planck Institute for Solar System Research. Holger Sierks, OSIRIS principal investigator at the Max Planck Institute, said "Finally seeing our target after a 10 year journey through space is an incredible feeling...These first images taken from such a huge distance show us that OSIRIS is ready for the upcoming adventure."

Philae Lander

Artist conception of ESA's Philae attaching to the surface of Comet 67P/Churyumov-Gerasimenko

Credit: ESA

On March 28, the $1.7 billon, 100 kg, German-built lander named Philae was woken from hibernation and successfully communicated with Earth at 10:40 A.M. EDT. The last time Philae sent a signal to Earth was on June 8, 2011 when Rosetta went into hibernation. Stephan Ulamec, Philae project manager at the German Aerospace Center, said, "Philae is operational and ready for the next few months."

In May of 2014, engines fired and adjust the course of Rosetta to intercept Comet Churyumov-Gerasimenko. Without the redirection, Rosetta would have missed Comet Churyumov-Gerasimenko by 31,000 miles (50,000 km) during the first week of August. After the fuel burn, it passed within 60 miles (100 km) of the comet.

Rosetta met-up with Comet 67P/Churyumov-Gerasimenko while it was still is in the colder regions of our solar system at a distance of 3.5 AU from the Sun. The orbiter carefully examined the comet, avoiding any shed material and identifying the most suitable place for Philae to land.

On November 11, 2014 Rosetta deployed the lander and successfully attached it to the comet's surface. The lander carried a drill which pierced the comet's surface, collected samples, and examined them in a built-in oven. The results were then analyzed on Earth to determine the chemical composition. "It's risky, because nobody has done [this] before, but this is the price to pay to learn about the origin of the solar system and perhaps more of the origin of life," said ESA Director General Jean-Jacques Dordain prior to the landing.

As the comet approaches the Sun, the comet's icy elements will continue to melt and emit dust. At least, three such areas were spotted during Comet Churyumov-Gerasimenko's last apparition in 2009. Since Rosetta will be "along for the ride", studying Comet Churyumov-Gerasimenko one year before its perihelion, it will have an unprecedented front-row seat to the transformation of a comet. A giant crack on the surface of the comet is also being watched carefully, hinting at possible fragmentation.

The Rosetta Space Mission cost €1bn.

The Rosetta Spaccraft

Credit: European Space Agency (ESA)

How Bright will Comet Churyumov-Gerasimenko get?

Comet 67P/Churyumov-Gerasimenko is expected to reach an apparent magnitude of 12 after its perihelion on August 13, 2015. It will not be visible to the naked eye. You will need a telescope to see this comet.

If the comet performs like it did during its 2003 and 2009 apparition, then the first jet should appear from the nucleus around a month before perihelion. In 2003, at its peak, the comet shed 132 pounds (60 kilograms) of material a second. In 1983, this amount was even greater at 485 pounds (220 kilograms) a second.