Six more moons have been found orbiting Jupiter, pushing to 58 the total number of known natural satellites of the solar system's largest planet.

The University of Hawaii's David Jewitt and Scott Sheppard, along with Jan Kleyna of Cambridge University, announced the discoveries Friday.

The moons are tiny, perhaps just a mile or so across, and orbit Jupiter at a distance of tens of millions of miles. They were found as part of an ongoing search using the world's two largest digital cameras at the Subaru and Canada-France-Hawaii telescopes atop Mauna Kea.

The moons follow retrograde orbits, traveling in the opposite direction of Jupiter's rotation. That suggests the moons were captured by Jupiter's gravitational tug, perhaps not long after the planet itself formed, Jewitt said.

Jupiter has more moons than any other planet. The largest four were discovered by Galileo in 1610.

The largest of those, Ganymede, with a diameter of 3,270 miles, is also the largest known moon in the solar system.

Jewitt's team has found 18 Jupiter moons this year and expects to find more.

"We think if we keep on pushing it with the cameras and telescopes we have available, we'll get to about 100," Jewitt said.