Scott Sheppard, David Jewitt, Yan Fernandez and Gene Magnier
Institute for Astronomy University of Hawaii
On UT 2000 Nov 21st an object was discovered near Jupiter using the University of Hawaii 2.2-m telescope. The slow rate of motion relative to the fixed stars and the proximity to Jupiter immediately suggested that the new object might be an unknown Jovian satellite. Astrometry obtained on subsequent nights was passed to Brian Marsden at the Harvard-Smithsonian Center for Astrophysics, who confirmed the possible satellite nature of the object and then linked it to the satellite discovered and lost by Charles Kowal in 1975. The results are described in Brian's IAU Circular.
The figure above shows three discovery images of 2000 J1 taken on UT 2000 Nov 21 at the UH telescope, assembled to show the motion of the object. The images were taken at UT 12:04, 12:49 and 13:27. The satellite moves towards the West (left) in these images. North is towards the top and the field of view is approximately 70 arcseconds by 70 arcseconds.
The size of the satellite is not well known because the albedo (the reflectivity of the surface) is unmeasured. However, a crude estimate based on the apparent brightness in our data would place the diameter at nearly 10 miles. The newly recovered satellite follows an "irregular orbit", meaning that the orbit is large, eccentric and inclined to Jupiter's equator. This type of satellite, of which 9 other examples are known as of this date, is thought to have been captured from heliocentric orbit when Jupiter was young.
These images show a tiny portion (about 0.5 percent) of the total number of pixels in the camera used to take the data. The so-called 8k CCD camera was built at the Institute for Astronomy by Gerry Luppino and is one of the world's largest astronomical cameras.
Contacts: Scott Sheppard (phone 808 956 6098; e-mail: sheppard@ifa.hawaii.edu) David Jewitt (phone 808 956 6664; e-mail: jewitt@ifa.hawaii.edu)
Page by Jing Li November 29 2000
