The shadow of Ganymede falls across Jupiter in this image taken by NASA’s Juno probe. The shadow seems especially large in this image because of how close to the planet Juno was — just 44,000 miles (71,000 km), or one-fifteenth the orbital distance of Ganymede. Swirling storm systems in the planet’s belts and zones are also visible.
In 2022, Jupiter reaches opposition – the point in its orbit opposite the Sun as seen from Earth – on Sept. 26. It’s also the giant planet’s closest approach to Earth since October 1963. On the 26th, Jupiter will blaze at magnitude -2.9, making it the brightest starlike object until Venus rises shortly before sunrise. You can observe Jupiter and its moons with a good binocular and of course with a telescope.
Opposition occurs when a planet that orbits outside of Earth’s orbit is positioned directly opposite the Sun. Around opposition is when a planet will be closest to Earth — prime time to observe it.
Spot the Spot
Jupiter’s most famous atmospheric feature is the Great Red Spot (GRS), a high-pressure storm that lies south of Jupiter’s equator, drifting slowly through the South Equatorial Belt.
The GRS changes color because clouds at higher levels and of different compositions condense above it. The GRS has varied from brick red during the 1960s to pale pink in the 1990s. Since 2000, the spot’s hue has remained light orange.
Jupiter’s four largest moons are known as the Galilean satellites, named for their discoverer, Italian astronomer Galileo Galilei. On Jan. 7, 1610, Galileo saw three stars in a straight line, two on one side of Jupiter and one on the other. The next night, their positions had changed. Five nights later, he spotted a fourth star. Galileo concluded that the “stars” were actually bodies revolving around Jupiter like the Moon circles Earth. His discovery made Io, Europa, Ganymede, and Callisto the first objects in the solar system to be observed despite being invisible to the naked eye.
An audience with the king
As fall is now in the Northern Hemisphere, Jupiter provides a brilliant target for any observer, no matter your equipment. It’s so bright, in fact, that you won’t need to head to a dark site to view it. Set your scope up in your yard, pull up a chair, and carve out some time to see the giant planet at its best.
Jupiter reached opposition Sept. 26 but will dominate its region of the sky for months
Jovian fun facts
• Jupiter’s magnetosphere is the largest structure in the solar system. If it were visible from Earth, it would appear larger than the Full Moon.
• On a moonless night at a dark site, Jupiter can cast a visible shadow.
• At its equator, Jupiter rotates at 28,100 mph (45,300 km/h), more than 27 times as fast as Earth.
• If Jupiter were hollow, it could hold 1,320 Earths.
• On average, Jupiter travels 5› per day against the background stars. So, in a little over six days, the giant planet moves roughly the width of the Full Moon.
• The King of Planets is almost 318 times as massive as Earth.
• Jupiter reflects 34 percent of the sunlight that falls on it.
• The brightest planetary satellite visible from Earth (not counting the Moon) is Ganymede. At opposition, the solar system’s largest moon glows at magnitude 4.4, a brightness that would make it visible to the naked eye if the glare from Jupiter didn’t overwhelm it.