The three faces of Rosetta's comet
10 July 2014
What a difference a week can make. Even in the six days since the last image, the shape of comet 67P/Churyumov-Gerasimenko is becoming much more apparent, although still heavily pixelated.
 |
| Comet 67P/Churyumov-Gerasimenko on 4 July 2014. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA |
This sequence of three images are separated by 4 hours, and were taken on 4 July by the narrow angle camera of Rosetta's scientific imaging system, OSIRIS. At this time, 37 000 km lay between the spacecraft and the comet, similar to the altitude at which geostationary satellites orbit Earth.
At this distance the comet covers an area of about 30 pixels in the narrow angle camera, with each pixel roughly equivalent to about 0.7 km.
The comet rotates with a period of about 12.4 hours. The image on the left is the first in the sequence, the middle around four hours later, and the right-hand one another four hours later. The small 'lobe' seen at the bottom of the first image is seen on the right in the second image, and at the top in the third.
It is not yet clear in which direction the rotation axis is pointing with respect to Rosetta, but the comet obviously has an irregular shape. Previous estimates suggested dimensions of 3 × 4 × 5 km, but we are now getting a more direct view.
But will it turn out to be long and skinny like comet Borrelly or Hartley 2, more rounded and lumpy, like Tempel-1 or Wild-2, or maybe somewhere in between, like Halley?
Let's see what clues are revealed in the coming week.
