Rosetta Comet Update Aug. 5 – Countdown To Orbit

Comet 67P/C-G from 145 miles photographed by Rosetta’s navigation camera on August 4. The comet is about 2.5 miles (4 km) across. Credit: ESA/Rosetta/NAVCAM

Today’s photo, taken Monday at a distance of only 145 miles (234 km), gives us a fresh perspective on comet 67P/Churyumov-Gerasimenko. From this angle, the larger lobe faces us, partially hiding the smaller lobe that’s been sticking up like a thumb in recent images. Beside craters, there are about a dozen small ‘dots’ with shadows that may be boulders and interesting variations in tones and textures in and around the smooth regions.

Rosetta is still slowly approaching the comet. Tomorrow, after additional rocket firings to slow it further, the spacecraft will be traveling in tandem with 67P C-G at the same 34,000 mph speed and enter orbit. The final thruster burn will slow the probe relative to the comet to just 3 feet per second – about the same as human walking speed. We’ll also start receiving full-frame pictures of 67P/C-G instead of cropped wide-field views. Can’t wait!

Sketch I made of Comet 67P/C-G (here abbreviated ‘Churyumov’) on Dec. 12, 1982 showing the comet’s starlike nucleus, bright coma and faint tail extending to the west. Tracking it across the winter sky in 1982 inspired my interest in comets. Credit: Bob King

Comet 67P/C-G got its mouthful of a name back in 1969 when astronomers Klim Churyumov and Svetland Gerasimenko of Kiev (now part of Ukraine) discovered it on a photographic plate. The letter ‘P’ refers to ‘periodic’ comets or those that cycle around the sun with periods of fewer than 200 years. The number ’67’ tells us that the comet was the 67th periodic comet to have its orbit determined; the first was famed 1P/Halley.

I’ve seen the 67P on three returns – 1982, 1995 and 2002 – and can honestly say that watching it change in size, brightness and appearance inspired a lifelong interest in comets. “Chury”, as I once called it, led to chasing one fascinating fuzzball after another. Some people make life lists of birds. I keep just one list – comets – and it’s waiting for entry #304.

For more about the Rosetta mission, check out this excellent FAQ.

4 Responses

  1. Giorgio Rizzarelli

    Thanx Bob for all the updates about Rosetta.

    Speaking about comets, a few days ago I and a skywatcher friend saw comet Jacques. It was a bit challenging, having to be with the equipment in country before dawn, and fighting with an unstable weather which we’ve been having for most of this new moon (and a tree which was quite in the direction of the comet LOL). At first it wasn’t too easy to find the comet in bino, since it was just a weak blob. Also in scope it was not spectacular (Lovejoy last winter was quite another thing). But we got photos at scope showing tail (possibly a multiple ion tail) and in piggyback with camera lens showing an intense green coma. I have enough for sleepless nights for now, so I’ll wait a few days to see Perseids (we saw a few that night, by the way). But clear skies to you.

    I’m also following the Sun as always. Still rather quiet concerning sunspots, it has long and thick filaments these days.

    1. astrobob

      Hi Giorgio,
      Great you got to see the comet. We had a rare clearing in the ubiquitous fire haze and Jacques looked very fine this morning. True, just a blob in binoculars, but in the 37cm scope I could see the green coloration of the coma and about 15′ of faint tail.

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