Carme, or Jupiter XI


Carme was not discovered until 1938 and was known only as Jupiter-XI until it was given its official name in 1975. Probes sent to Jupiter have since revealed Carme to be 47 km in diameter and it rotates on its axis every 10.4 hours. When this image was created it was at magnitude 17.6.

To form the image above 19 exposures were taken with a total duration of 2175 seconds. The satellite was moving with respect to the background stars during this time so the sub-images were stacked on the predicted motion of the satellite, not on the stars themselves. In consequence, Carme shows up as a fairly sharp circular object whereas all the stars are trailed slightly.

The sky conditions were not very good when this image was taken. Saharan dust in the atmosphere was illuminated by an almost full moon and turbulent winds pouring down off the Cumbre Vieja to the east produced very bad seeing of around 6 to 8 arcseconds. The resulting poor contrast and bloated star images are readily visible, especially if the image is compared to that of Lysithea (a notedly fainter satellite) taken the following night when conditions had improved. The image is displayed negated (i.e. black stars on a light background) to help make the satellite more visible.

Image information
Date and time of observation  2020-08-05 01:00 UT
Telescope 0.4m f/6.5 Dilworth-Relay
Camera Starlight Xpress Trius-PRO SX814 CCD
Filter None
Exposure 1x15s and 18x120s median-stacked on predicted motion of the satellite
Centre of image RA 19h18m38.0s  Dec -22°09'03"
Image dimensions 5.0 arcmin × 4.2 arcmin