The largest planet in the Solar System, as many people already know, is Jupiter. It is one of the gas giants in our Solar System, but how does it compare in size and other attributes to the other planets in the Solar System. In the next sections, we will be taking a closer look at Jupiter and learning more about it.
Jupiter’s Orbit & Rotation
Jupiter is the fifth planet from the Sun – it makes a complete revolution about every 11.6 years at the closest distance of around 740.5 million miles and the farthest distance of about 816.6 million miles with an eccentricity in its orbit of roughly .0489. This elliptical orbital plane of Jupiter is inclined about 1.31 degrees in relation to that of the Earth.
Jupiter rotates around its axis faster than any other planet in the Solar System – the Jovian day is only about 9.925 hours which gives it a rotational speed of about 28000 miles per hour at the outer most cloud tops at its equator; this compares to a rotational speed of the Earth of about 1000 miles per hour at its equator. This tremendous rotational speed causes a flattening effect at the poles and some bulging at the equator which means that Jupiter isn’t a perfectly round sphere; it has an oblate spheroid shape.
Jupiter has an axial tilt of only 3.13 degrees, which is really quite small; this means that Jupiter has no significant change of seasons the way the Earth does, with its much greater axial tilt of 23.4 degrees(this is an average – the Earth’s axial tilt actually varies between 22.1 degrees and 24.5 degrees due to a wobble it has in its orbit).
Its distance from the Earth varies from 390.68 million miles at the closest to 576.68 million miles at the farthest. When Jupiter is at its closest distance to the Earth it actually becomes the third brightest object in the night sky behind the Moon and Venus with an apparent magnitude of -2.94 – bright enough to cast shadows!
Jupiter and its 4 largest moons can easily be viewed through binoculars, but to get the best experience, of course, one should use a telescope. Even a modest telescope will reveal the color bands and Giant Red Spot of Jupiter.
Composition Of Jupiter
The composition of Jupiter – its internal structure and atmosphere – will be discussed next.
Internal Structure Of Jupiter
Jupiter is currently believed to have a dense core consisting of various heavier elements due to gravitational studies which have been done by different space probes, but that is by no means certain; it is possible that there is no dense central core since gravitational studies done so far are not precise enough to definitively determine this.
However, if a dense central core exists, as is now suggested by the most recent gravitational measurements, it would have somewhere between 4 to 14 percent the mass of Jupiter; this would be 12 to 45 times the mass of the entire Earth! It would probably consist of a very dense central core made of various heavier elements, perhaps rocky in nature, with a layer of liquid hydrogen and helium surrounding that.
Atmosphere Of Jupiter
Jupiter has the largest atmospheric structure of any planet in the Solar System with an altitude of at least 3000 miles from top to bottom. Temperatures range from -234 degrees Fahrenheit to a somewhat balmy 70 degrees Fahrenheit as you move deeper into the Jovian atmosphere. The surface of Jupiter has no solidity, so the beginning of the atmosphere is defined as where the pressure is equal to one bar, which is about 14.5 pounds per square inch. This compares to 14.7 pounds per square inch at sea level on the Earth.
Jupiter is perpetually covered with a thick layer of clouds about 31 miles deep consisting of mostly ammonia crystals and possibly some ammonium hydrosulfide. These clouds lie in a thermodynamic gradient stratification area of Jupiter’s atmosphere between its troposphere and stratosphere in multi-colored latitudinal bands, some light in color and some dark, which can vary in intensity of colors over a period of years, but which have enough stability to make prolonged study possible.
These multi-colored bands around Jupiter are caused by various compounds coming up from the surface and changing color when exposed to ultraviolet light. The stratification of the band structure itself is caused mainly by the extremely powerful winds in Jupiter’s atmosphere which is in turn caused by Jupiters extremely fast rotation – 28000 miles per hour in the outer cloud tops at the equator, as previously mentioned.
The atmosphere of Jupiter has extremely violent storms, the most famous of which is the Giant Red Spot, easily visible from Earth through a modest telescope. This Giant Red Spot was first observed over 350 years ago in 1665, and observations in recent years seem to indicate some fading which would mean that the extremely intense storm causing it may be abating. Jupiter also has less intense white and brown ovals caused by less intense storms – the white ovals mainly consist of cooler clouds in the upper thinner cloud layer while the brown ovals are warmer clouds lower in the cloud layer.
Flashes of lightning have been observed in the atmosphere of Jupiter by the various space probes which seem to indicate there may be a layer of water clouds. Lightning on Jupiter is generated by electrical discharges similar to lightning on Earth by heat that is driven up from the interior of Jupiter through its atmosphere.
The big difference though is that these lightning discharges are often over a thousand times as powerful as those in Earth’s atmosphere. That means that Jupiter may have thunderstorms similar to Earth in their nature, but far more intense.
Moons Of Jupiter
Jupiter has 79 known moons at the present time – this is the largest number of moons with stable orbits of any planet in the Solar System. The largest and most massive of these are the four Galilean moons; Io, Europa, Ganymede, and Callisto, so-called since they were first observed by the great astronomer and scientist Galileo Galilei somewhere in the time frame of December 1609 to January 1610. By March of 1610, Galileo realized that these were moons orbiting another planet – the first objects that were ever discovered orbiting another planet.
How Big Is Jupiter?
Jupiter is a gigantic planet, the largest in the Solar System by far; the mass of Jupiter alone is about two and one-half times that of all the other planets combined, and one-thousandth that of the Sun! By volume, Jupiter could hold around 1300 Earths and it is around 317 times as massive as Earth. With a surface gravity of 2.528g, compared to Earths 1g, a person who weighed 170 pounds on Earth would weigh 429.6 pounds on Jupiter!
Exploration Of Jupiter
Jupiter has been explored by a number of different space probes, both flyby, and orbital, which will be discussed in more detail below.
Flyby Missions To Jupiter
Flyby missions to Jupiter began in 1973 with the Pioneer 10 space probe, then other flybys followed with Pioneer 11, Voyager 1, Voyager 2, Ulysses, Cassini, and New Horizons. Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 were all projects of NASA, while Ulysses and Cassini were a collaboration between NASA and the European Space Agency.
These probes gathered much very important information about Jupiter including more precise measurements of its size and mass, polar flattening effects, atmospheric composition and effects(such as wind velocities and storms), radiation and magnetic fields, its gravitational field, and closeup looks at some of Jupiter’s moons.
Orbital Missions To Jupiter
There have been two orbital missions to Jupiter so far, both by NASA, which will now be discussed in more detail.
Galileo Space Probe
Galileo was the first spacecraft to orbit Jupiter, entering its orbit on December 7th, 1995 and continuing to orbit for about 7 years. This probe obtained a great deal of valuable information about Jupiter including more precise atmospheric studies from a probe which it released into Jupiter’s atmosphere, close-ups of all of Jupiters Galilean moons along with the moon Amalthea, and detailed observations of the impact of the comet Shoemaker-Levy 9 into Jupiter, among other things.
Juno Space Probe
Juno is a space probe to Jupiter which went into a polar orbit on July 5th, 2016 and is continuing to orbit the planet past the original length of 7 years planned for the mission. Its mission is to continue to study the composition of Jupiter, its gravitational and magnetic fields, and the magnetosphere of Jupiter’s polar region. It is hoped that the Juno mission will find more clues about how Jupiter was actually formed along with more information about its internal structure.
Future Space Probes To Jupiter
Some future missions to Jupiter which are being planned include the Jupiter Icy Moon Explorer from the European Space Agency to obtain more information about moons in the Jovian system, due for launch in 2022, and NASA’s Europa Clipper mission, due for launch in 2025 to study the Galilean moon Europa in more detail.