Jupiter At Opposition

The planets in our solar system always make amazing targets for skywatchers. Most are bright enough to be seen even in heavy light pollution, and can reveal striking details and even moons when viewed with a telescope. The best time to view the planets with a telescope is when the planet is in opposition.

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Jupiter

Opposition occurs when the planet is exactly opposite in the sky from the sun. It is also when Earth is closest to the planet, making the planet appear the largest and brightest during each year. On March 8th, Jupiter will be at opposition and at it’s closest distance to Earth at around 365 million miles (588 million kilometers), giving a good opportunity to see some fine details on our solar system’s largest planet.

Jupiter will rise shortly after sunset in the constellation Leo, and will reach it’s highest point in the sky around midnight. On average, Jupiter is the third brightest object in the night sky behind the Moon and Venus respectively. Sometimes, Mars can appear brighter during its favorable oppositions. Jupiter is largest planet, with a mass of over 300 Earths, or 1/1050th of the sun. It’s made of mostly hydrogen and helium, and has 67 moons which orbit the planet.

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Image of Jupiter and the Galilean Moons through a telescope. From top to bottom: Callisto, Europa, Io, Jupiter, and Ganymede. Image taken by me

Using a pair of binoculars held steady, you can spot Jupiter and even several of its 4 brightest moons. Those 4 moons are known as the Galilean Moons, as it was Galileo who first discovered them with the first telescope. They were also the first moons beside our own that were discovered in our solar system, and are named after mythological characters associated with Zeus. If you use a telescope to spot Jupiter, you can make out cloud layers, the Great Red Spot, and even some of the smaller storms on Jupiter, depending on how steady your viewing is and how much magnification you use. Also, the use of filters on your eyepieces can help enhance various details.

Spotting the bright moons of Jupiter is one of the unforgettable moments you will have of stargazing! All 4 moons are bright enough that they can be seen from Earth with your naked eye if the glare of Jupiter wasn’t there to drown them out. Although they can be spotted, no detail can be made out them with amateur telescopes. They are still interesting objects to spot. Let’s take a brief look at each one.

Callisto
Callisto

Callisto is the second largest of the moons of Jupiter, and the third largest moon in our solar system. It is about 99% the size of the planet Mercury. Made up of mostly rocks and ices, Callisto has the oldest and one of the most cratered surfaces in the solar system. It is also the outermost moon of the Galilean Moons.

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Ganymede

Ganymede is both the largest moon of Jupiter, and the largest moon in the solar system, having a diameter 8% larger than the planet Mercury. It is the second outermost moon of the Galilean moons. Also made up of rocks and ices, it is thought that Ganymede has a sub-surface ocean that contains more water than all of Earth’s oceans combined. Ganymede is also the only moon in the solar system that has its own magnetic field.

Europa-moon
Europa

Europa is the second innermost moon of the Galilean moons. It is slightly smaller than our own moon, making it the 6th largest moon in the solar system. Europa has the smoothest surface of any solid object in the solar system, due to its outer surface being ice with water underneath. The large cracks on the surface appear to have formed due to tidal stresses from Jupiter and the other moons which “crack” the ice, then new liquid water freezes to fill the crack. It is thought that the water under Europa’s surface is warm enough to support life, making it a major target of interest in the search for extraterrestrial life.

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Io

Io is the innermost moon of the Galilean Moons. It is slightly larger than our Moon, making Io the 4th largest moon in the solar system. It is the most dense and driest moon in the solar system. It’s also the most geologically active body in the solar system as well. Consisting of rock, Io has over 400 active volcanoes. This is due to tidal pull between Jupiter and the other large moons of Jupiter. Io has mountains taller than Mount Everest, and has very few craters due to lava from erupting volcanoes which constantly resurface Io.

With Jupiter approaching opposition, it is a great opportunity to spot the details of this giant planet and to see its moons. While the size and brightness of Jupiter and its moons enables you to spot them any time Jupiter is in the night sky, the best views will come during opposition. With the help of some astronomy websites and articles, it’s possible to be able to distinguish which moon is which, as they visually appear similiar in a telescope, and they orbit Jupiter quickly enough to change position nightly. Using these tools, it’s also possible to see when the Great Red Spot is visible, and even see when shadows from the moons cross Jupiter’s surface. With Jupiter being its biggest and brightest, and being out in the evening, now is your best opportunity to take a look at this amazing planet and its moons!

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