Two New Satellites for Jupiter



This animation combines two discovery images for the new Jovian satellite S/2017 J 1, taken March 23, 2017, with the 4-m reflector on Cerro Tololo in Chile.
Scott Sheppard
Just a mile across, a pair of moonlets found orbiting Jupiter bring the planet's total satellite count to 69.

The advent of monster telescopes equipped with super-sensitive, wide-field detectors has been a boon for astronomical discoveries, among them a bevy of tiny moonlets around the outer planets. For example, observations made from 2000 to 2003 yielded 46 moons around Jupiter — more than two-thirds of the planet's total!

Now astronomer Scott Sheppard (Carnegie Institution for Science) has added two more to the planet's extended family, bringing the total of known moons to 69. The announcements for S/2016 J 1 and S/2017 J 1 ("S" for satellite, "J" for Jupiter) came via Minor Planet Electronic Circulars issued on June 2nd and June 5th, respectively.

As Sheppard explains, "We were continuing our survey looking for very distant objects in the outer solar system, which includes looking for Planet X, and Jupiter just happened to be in the area we were looking in 2016 and 2017." So they took a minor detour to image some fields that were very close to Jupiter.
With magnitudes hovering near 24, these barely-there moonlets must be only 1 or 2 km across. So for now all that's really known is the character of their orbits:




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