[meteorite-list] Rosetta's Comet Wakes Up (67P/Churyumov-Gerasimenko)

[Ron Baalke]

http://www.mps.mpg.de/3261529/Rosetta_s-comet-wakes-up

Rosetta's comet wakes up

In new images recorded by ESO's Very Large Telescope comet Churyumov-Gerasimenko 
appears brighter than expected. 

Max Planck Institute
March 10, 2014

It's back! After comet 67P/Churyumov-Gerasimenko had disappeared behind 
the Sun and out of the Earth's view last year in October, the target comet 
of ESA's Rosetta mission can now be seen again. In the most recent image 
obtained by researchers from the Max Planck Institute for Solar System 
Research (MPS) in Germany and the European Southern Observatory (ESO) 
with the help of ESO's Very Large Telescope on February 28th, 2014, the 
comet presents itself brighter than expected for the nucleus alone. This 
suggests that frozen ice is already beginning to vaporize and form a very 
thin atmosphere. In August, the spacecraft Rosetta will rendezvous with 
67P/Churyumov-Gerasimenko and accompany it on its journey around the Sun 
until at least the end of 2015.   

[Images]
Comet 67P/Churyumov-Gerasimenko as observed on Februaray 28th, 2014, with 
the Very Large Telescope. 

To obtain a measurable image of the comet from a distance of 740 million 
kilometers, the scientists superposed several exposures taken at slightly 
different times. Before, the images were shifted to compensate for the 
comet's motion. The stars in the background therefore appear as broadly 
smudged lines. Subtracting the starry background then revealed the comet: 
a tiny dot in space.

For researchers, this tiny dot carries valuable information. Already 
67P/Churyumov-Gerasimenko is approximately 50 percent brighter than in the 
last images from October 2013. While the comet has moved another 50 million 
kilometers closer to Earth in this time (and 80 million kilometers closer to 
the Sun), the increase in brightness cannot be explained by the smaller 
distance alone. 

"The new image suggests that 67P is beginning to emit gas and dust at 
a relatively large distance from the Sun", says Colin Snodgrass from the 
MPS. This confirms a study presented by Snodgrass and his colleagues last 
year in which they had compared the comet's brightness as recorded during 
its previous orbits around the Sun. The calculations showed that already 
in March 2014 its activity would be measurable from Earth.

In the coming months, the researchers will continue to monitor how the 
comet's brightness develops in close collaboration with ESA. The data 
will help to assess what conditions await Rosetta upon arrival in August.