Jupiter is truly the king of all of the planets in the solar system. Although Venus can grow larger in apparent size, the wealth of details visible on Jupiter makes it an incredible photographic subject. Jupiter is the largest planet in the solar system, and is the fifth planet from the Sun. It was named after the Roman god Jupiter, the king of all the gods and the god of the sky and thunder. The diameter of Jupiter is 142,984 kilometers (about 88,846 miles) compared to the Earth's diameter of 12,742 km (7,917 miles). Jupiter is about 11 times the diameter of the Earth and one-tenth the diameter of the Sun. Jupiter is a gas giant that does not have a visible solid surface. It takes 4,332.59 Earth days (11.8618 Earth years) for Jupiter to orbit around the Sun. Its brightness can very from magnitude -1.6 to -2.94, and its size can vary from 29.8 to 50.1 arcseconds. Jupiter's size and brightness vary depending on where Jupiter and the Earth are in their orbits around the Sun and in relationship to each other. Jupiter appears largest and brightest when it is closest to the Earth at opposition, which occurs about every 13 months. It takes 9 hours 55 minutes and 30 seconds for Jupiter to rotate once on its own axis. This is the fastest rotational period of all the planets, and it means that we are limited in the length of time that we can shoot a video for stacking before details become blurred as we discussed in Chapter 1, Section 8 - Planetary Rotation and Detail Smearing. Features on Jupiter Because Jupiter is a gas giant we do not really see its surface. We see the tops of clouds in Jupiter's atmosphere which is made mostly of hydrogen and helium.
When looking at Jupiter with a telescope, the first features that you will see are Jupiter's two prominent equatorial belts, which can be seen even in a small telescope. These are called the north and south equatorial belts. Jupiter also has other alternating darker belts and lighter zones. These run parallel to the equator and are created by strong east-west winds in the upper reaches of the planet's atmosphere. Sometimes these belts fade in and out and change due to mixing within Jupiter's atmosphere. At higher magnification with a larger scope under good seeing, and if Jupiter is turned the right way, the Great Red Spot can be seen. It is a gigantic oval-shaped storm in Jupiter's south equatorial belt. It is usually 20,000 km (12,400 miles) long by 12,000 km (7,500 miles) wide (twice as wide as the Earth), but can change in size. It also changes color sometimes, and sometimes can fade leaving what is called the "Red Spot Hollow". The Great Red Spot has been observed for hundreds of years. It is a high-pressure system that rotates counter-clockwise with a rotation period of about 6-7 days, driven by high velocity winds. Jupiter also has smaller white ovals and brown "barges" which are also thought to be storms in the atmosphere like the larger Great Red Spot. White ovals are usually cooler and are located in the upper atmosphere. Brown barges are usually warmer and located below the altitude that white ovals are found.
Belts and Zones on Jupiter (Not all are always present.) Features on Jupiter (Not all are always present.)
If you want to catch a particular feature on Jupiter, like the Great Red Spot, you have to observe it when that detail is facing the Earth. You might think a detail would be visible for half of Jupiter's rotational period of about 10 hours, but it would be much less than that because you can't really see it when it is on the limb. It takes a while for a feature to rotate into view. The Great Red Spot is well placed for viewing only for about two hours - an hour before and after it transits the meridian, the center line that runs north south on a planet. You can find out if the Great Red Spot is visible with Sky & Telescope's Red Spot Calculator. Different parts of Jupiter's atmosphere also rotate at different speeds, particularly the equatorial area compared to the rest of the planet. Observers call these "systems" of rotation. System I, the equatorial zone, rotates in 9 hours 50.5 minutes. System II, most of the rest of the planet, rotates in 9 hours 55.7 minutes. The Moons of Jupiter
Jupiter's four large bright moons called the Galilean moons. They were discovered by Galileo in 1610. Galileo's observations of these moons provided strong evidence for the Copernican theory that the Earth was not the center of the universe. The Galilean moons are Ganymede, Callisto, Io and Europa. These moons are bright enough to be seen with the unaided eye, but are usually lost in the bright glare of Jupiter. They are easy to spot in a telescope and can even be recorded with telephoto camera lenses. You can find their locations with Sky & Telescope's Jupiter's Moons calculator.
Besides the Galilean moons, Jupiter has 5 other moons that are brighter than magnitude 17: Almathea, Thebe, Himalia, Elara and Pasiphae.
Jupiter also has many other smaller moons. Currently, Wikipedia lists 66. Scott Sheppard's Jupiter's Known Satellites web page lists 67. Most are small irregularly shaped bodies only a couple of kilometers in diameter. These are probably asteroids captured by Jupiter's gravity. Himalia is the largest of the small moons with a diameter of 184 km (114 miles). The Galilean moons are 1.2, 1.0, 1.7 and 1.6 arcseconds in diameter.
All of the Galilean moons are larger than Pluto. Ganymede, the largest moon in the solar system, is even larger than Mercury. Under very good seeing conditions, with a scope with a moderately large aperture of 8 inches or more with excellent optics, detail can even be captured on the Galilean moons. These moons are small, usually around 1 arcsecond or less, so recording detail on one of them is quite an accomplishment for a high-resolution planetary photographer. Impacts Like every other body in the solar system, sometimes comets and asteroids crashed into Jupiter. When these types of objects crash into a solid surface planet like the Earth or Mars or Mercury, they leaves behind impact craters. Because Jupiter is a gas giant with no solid surface, impactors do not leave craters. They can leave behind temporary dark markings as evidence after exploding and disintegrating in the thick atmosphere of Jupiter. The dark spots are believed to be material welling up from lower layers of the atmosphere. Comet Shoemaker-Levy 9 crashed into Jupiter in July of 1994, leaving marks in the atmosphere that were visible for months afterward. These marks appeared as large crescent-shaped dark spots in Jupiter's south south temperate zone. Scientists had thought that impacts like this were rare, but had to reconsider when two more impacts were observed on Jupiter in 2009 and 2010, both discovered by amateur astrophotographer Anthony Wesley. Jupiter's Rings Like Saturn, Jupiter has rings. Saturn's rings are made of ice but Jupiter's are dark and probably made of rocky material. Unfortunately, unlike Saturn, they are so small and faint as to be invisible to amateur astronomer's telescopes. Tips for Photographing Jupiter
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