On September 1, 2017, NASA’s Juno spacecraft witnessed a remarkable cosmic event — a small Jovian moon called Amalthea blocked the sunlight and cast a shadow on the face of the gas giant.
Amalthea casts a shadow on Jupiter in this image captured by NASA’s Juno spacecraft; the elongated shape of the shadow is a result of both the location of Amalthea with relation to Jupiter in this image as well as the irregular shape of the small moon itself. Image credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstaedt.
On September 1 at 5:49 p.m. EDT (2:49 p.m. PDT), Juno successfully made its eighth flyby of Jupiter.
The newly released image was taken just three minutes before Juno’s closest approach to the planet.
At the time the image was taken, the spacecraft was 2,397 miles (3,858 km) from the tops of the clouds of the planet at a latitude of 17.6 degrees.
This three-color image of Amalthea was taken on March 4, 2979, by NASA’s Voyager 1 spacecraft. Image credit: NASA.
Amalthea, also known as Jupiter V, is the third moon of Jupiter in order of distance from the giant planet.
Discovered in 1892 by the American astronomer Edward Emerson Barnard, the small moon is irregular, with dimensions about 155 x 91 x 80 miles (250 x 146 x 128 km).
Amalthea orbits 112,717 miles (181,400 km) from Jupiter and takes 0.498 Earth days to complete one orbit.
It rotates on its axis once for each orbit around Jupiter, always keeping the same side facing the planet.
According to NASA astronomers, Amalthea is the reddest object in our Solar System and it appears to give out more heat than it receives from the Sun.
This may be because, as it orbits within Jupiter’s powerful magnetic field, electric currents are included in the moon’s core. Alternatively, the heat could be from tidal stresses.
