Jupiter’s moon count reaches 79, scientists say

NEW YORK — Astronomers are still finding moons of Jupiter, 400 years after Galileo used his spyglass to spot the first ones.

The latest discovery of a dozen small moons brings the total to 79, the most of any planet in our solar system.

Scientists were looking for objects on the fringes of the solar system last year when they pointed their telescopes close to Jupiter’s backyard, according to Scott Sheppard of the Carnegie Institute for Science in Washington. They saw a new group of objects moving around the giant gas planet but didn’t know whether they were moons or asteroids passing near Jupiter.

“There was no eureka moment,” said Sheppard, who led the team of astronomers. “It took a year to figure out what these objects were.”

They all turned out to be moons of Jupiter. The confirmation of 10 was announced Tuesday. Two had been confirmed earlier.

The moons had not been spotted before because they are tiny. They are about one to two miles across, said astronomer Gareth Williams of the International Astronomical Union’s Minor Planet Center.

He said Jupiter might have even more moons just as small waiting to be found.

“We just haven’t observed them enough,” said Williams, who helped confirm the moons’ orbits.

Telescopes in Chile, Hawaii and Arizona were used for the latest discovery and confirmation.

Galileo detected Jupiter’s four largest moons, Io, Europa, Ganymede and Callisto in 1610. The latest count of 79 known moons includes eight that have not been seen for several years. Saturn is next with 61, followed by Uranus with 27 and Neptune with 14. Mars has two, Earth has one and Mercury and Venus have none.