APOD: 2025 August 23 Б Fishing for the Moon
23.08.2025

How big is planet Earth's Moon? Compared to other moons of the Solar System, it's number 5 on the largest to smallest ranked list, following Jupiter's moon Ganymede, Saturn's moon Titan, and Jovian moons Callisto and Io. Continuing the list, the Moon comes before Jupiter's Europa and Neptune's Triton.

Ida and Dactyl: Asteroid and Moon
17.10.2025

This asteroid has a moon. The robot spacecraft Galileo enroute to explore the Jovian system in 1993, encountered and photographed two asteroids during its long interplanetary voyage. The second minor planet it photographed, 243 Ida, was discovered to have a moon.

Triple Transit and Mutual Events
21.08.2021

These three panels feature the Solar System's ruling gas giant Jupiter on August 15 as seen from Cebu City, Phillipines, planet Earth. On that date the well-timed telescopic views detail some remarkable performances, transits and mutual events, by Jupiter's Galilean moons.

Moon Shadow on Jupiter
27.04.2022

What is that large dark spot on Jupiter? It's the shadow of Io, one of Jupiter's largest moons. When Jupiter's moons cross between the Jovian giant and the Sun, they created shadows just like when the Earth's moon crosses between the Earth and the Sun.

Astronomer s Moon
24.08.2007

Jupiter is an astronomer's planet -- its large size and contrasting global cloud belts and zones allow detailed studies with a range of earthbound telescopes. On the other hand, most telescopic views of Jupiter's moons usually show only featureless, tantalizing points of light hovering near the ruling gas giant.

Europa: Ridges and Rafts on a Frozen Moon
10.09.1998

The large Jovian moon Europa may harbor liquid water beneath its frozen crust. Controversy surrounding this idea has been recently fueled by dramatic images of Europa's surface from the Galileo spacecraft. This alluring...

APOD: 2020 September 2 Б Jupiter and the Moons
2.09.2020

How many moons do you see? Many people would say one, referring to the Earth's Moon, prominent on the lower left. But take a closer look at the object on the upper right.

Io: Moon Over Jupiter
20.04.2001

How big is the Jovian moon Io? The most volcanic body in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite.

560 Kilometers Above Europa
3.03.1998

This is the closest photograph ever taken of Europa. Last December, NASA's spacecraft Galileo swept past the Jovian moon and took photographs which were released yesterday. Speculation that life-bearing oceans exist beneath Europa's surface caused NASA to put Galileo on orbits that approach Europa.

Jagged Hills on Jupiters Callisto
28.08.2001

Why does Jupiter's moon Callisto have unusual jagged hills? This mystery came to light after the robot spacecraft Galileo, in orbit around Jupiter since 1995, swooped past the dark moon in May. The resulting pictures were the highest resolution yet obtained for a Jovian moon: objects as small as 3 meters across are discernable.