Jupiter, Jupiter's Moons, Solar System

The Planet Jupiter


Jupiter has fascinated astronomers since the birth of the telescope and it’s subsequent confirmed discovery of moons in 1610, by Galileo. The fifth planet from the sun and the largest planet in our solar system is so immense that it owns a mass two and a half times that of all the other planets in the Solar System combined.

Jupiter is a gas giant planet composed primarily of hydrogen and helium. It’s believed that the planet could contain rocky elements however it’s been shown that Jupiter lacks a clearly defined solid surface. It has the largest planetary atmosphere in the Solar System but because it has no true surface, its base is considered to be the point in which its atmospheric pressure reaches 100 kPa (1.0 bar).

The planet has most notably been explored by robotic spacecraft such as Pioneer, Voyager, the Galileo orbiter, and most recently by New Horizons. Observations of the planet date as far back as 7th or 8th century BC where ancient Chinese cultures used the planet’s orbit to calculate their cycle of the 12 earthly branches.

A prominent feature of Jupiter is the great red spot. The great red spot is a storm that was first observed in 1831 and continues to rage today with no apparent end in sight. The storm is large enough to be seen by Earth-based telescopes and is big enough to fit an entire Earth within it’s diameter.

There’s so much to learn about the largest planet in our solar system, following along below as we’re just getting started.

What Is Jupiter Like

Jupiter is a gas planet. In this case its atmosphere is mainly made up of hydrogen and helium gasses that create stunning and thick brown, red, and yellow clouds that cover its entire surface in a stripe-like pattern.

Similar to Saturn, the planet has three faint rings that are often forgotten. Made up of tiny dust particles, the rings were initially discovered by NASA’s Voyager 1 in 1979.

If you were to stand atop Jupiter’s atmosphere you would weigh 2.4 times what you do right now. A 100 pound individual would weigh 240 pounds on Jupiter; the force of gravity at the top of Jupiter’s atmosphere is 2.4 times the gravity here on Earth.

The planet’s magnetic field is 2o times stronger than the magnetic field here on Earth. Underneath cloud cover there’s an ocean of liquid metallic hydrogen created by immense pressures (Hydrogen is usually a gas on Earth, but becomes a liquid on Jupiter). This liquid ocean creates the strongest magnetic field in our solar system as the planet rotates around it’s axis.

A day on Jupiter is approximately 10 hours long as the planet rotates faster than any other in our solar system. On year on Jupiter is equivalent to 12 here on Earth; it takes the planet 12 years to orbit the sun.

Jupiter’s Size, Mass, And Orbit

Specifically speaking, the dimensions of Jupiter are expressed as so: 1.8981 x 10^27 kg, 1.43128 x 1015 km3, 6.1419 x 1010 km2, and 4.39264 x 105. In lamens, this shows that the planet has a diameter approximately 11 times that of Earth, and 2.5 the mass of all other planets in our solar system combined. 

Even with it’s immense size, the planet has a surprisingly low density at 1.326 g/cm3, which is just less than one quarter of the density here on Earth. So even while it’s volume could contain 1,321 Earths, its actual weight is only 318 times of our home planet. This low density is one of the reasons why scientists believe that the planet is comprised mostly of gasses – even in the face of it’s core debates. 

The most massive planet in our solar system orbits the sun at an average distance of 778,299,000 km (5.2 AU). At perihelion the planet orbits 740,550,000 km (4.95 AU) and at aphelion 816,040,000 km (5.455 AU). Aphelion is the point at which the orbit of an object is furthest from the sun. Contrastly, Perihelion is the point at which the orbit of an object is at its closest to the sun. 

Jupiter is approximately 143,000 kilometers (about 89,000 miles) in diameter at it’s equator and is so large that it could fit more than 1,300 Earth’s within its boundaries.

Jupiter’s diameter is one order of magnitude smaller (×0.10045) than the Sun, and one order of magnitude larger (×10.9733) than Earth. The Great Red Spot is roughly the same size as Earth.

Jupiter’s Storms

Jupiter has some of the most intense weather patterns in our solar system with wind speeds as high as 620 kph (385 mph). In this turbulent atmosphere storms can form within hours and can grow to thousands of kilometers in diameter overnight. 

Clouds on Jupiter are primarily composed of ammonia crystals and ammonium hydrosulfide. They’re located in an area of the atmosphere known as the tropopause, a region rapidly stirred by vertical motions. The troposhpere is warmed by the sun and the planet’s interior and cooled due to re-radiation to space. The troposphere is believed to be roughly 50 km (31 mi) deep and comprised of an upper and lower deck of cloud regions. 

It has also been theorized that it’s cloud regions could contain a thin layer of water cloud. This is shown by lightning that has been detected in Jupiter’s atmosphere, which is a sign that water’s polarity could be causing an electrical charge.

The famous ‘string of pearls’ storm cloud. (JunoCam)

The History Of Jupiter

Jupiter’s moons were officially discovered by Galileo Galilei in 1610 in the age of the telescope. However the planet has been a subject of interest for centuries with civilizations across the globe as early as the Babylonian astronomers of the 7th or 8th century BC.

It has a specific history with the ancient Chinese where the civilization observed the orbit of Suìxīng to establish the 12 earthly branches, based on the 12 years it takes to orbit the sun. In the 4th century BC these observations evolved into what we now know as the Chinese Zodiac. These observations show that a Chinese historian named Xi Zezong claims that ancient astronomer that Gan De, was the first to discover Jupiter with an unaided eye in 362 BC – this would predate Galileo’s initially discovery by two millenia.

Ptolemy demonstrates knowledge of the planet in the 2nd century when he constructed his infamous geocentric planetary model. In this model, he shows that Jupiter has an orbit of 11.86 years – an impressive observation without the aid of a telescope. 

In the 1600s Cassini used new telescopes to view the planet and its colorful storms and was also able to infer the rotational period of the planet. In 1831 astronomer Heinrich Schwabe produced the first known drawing of the Great Red Spot, and in 1892 E. E. Barnard discovered Amalthea, which is the last of the planetary moons to be discovered by observation. 

In the 20th century we began to learn about the composition of the atmosphere where Rupert Wildt identified absorption bands of ammonia and methane in the spectra of Jupiter. We also identified Three long-lived anticyclonic features termed white ovals that were observed in 1938. For several decades they remained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two of the ovals merged in 1998, then absorbed the third in 2000, becoming Oval BA.

Jupiter’s Structure And Composition

Jupiter’s atmosphere is approximately 88–92% hydrogen and 8–12% helium by percent volume of gas molecules. The atmosphere on the planet is made up of the following trace compounds: methane, water vapor, ammonia, and silicon-based compounds. As well, there exist traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur. We have also located trace amounts of benzene and other hydrocarbons through the process of infrared and ultraviolet measurements of the atmosphere.

It is most commonly believed that Jupiter has a dense core composed of a mixture of elements with a surrounding layer of metallic hydrogen, helium, and an outer layer of molecular hydrogen. There is a large uncertainty that surrounds the core’s composition, and it’s actual existence. The idea of a core was initially posited in 1997 where research indicated a mass of from 12 to 45 times that of Earth, or roughly 4%–14% of the total mass of Jupiter at the center of the planet.

The possibility of the core’s presence is further aided by theories that show how the planet was formed. Models suggest that the formation of a rocky core massive enough to collect a bulk of hydrogen and helium is required to build Jupiter from the protosolar nebula. It’s believed that the core would have shrunk over millions of years, and could be entirely absent. Until we have gravitational measurements precise enough to rule this out, we won’t know for certain.

If it exists, Jupiter’s core region could be surrounded by dense metallic hydrogen that extends to roughly 78% of the planet’s radius. Above this layer lies a transparent atmosphere comprised of hydrogen. At this depth, hydrogen is neither a liquid or a gas – the pressure is above hydrogen’s critical pressure of 1.2858 MPa which causes the substance to act in it’s fluid state.

As we descend deeper into the planet temperatures and pressures increase drastically, thanks in part to the due to the Kelvin–Helmholtz mechanism. At this level the temperature can reach 10,000 K (9,700 °C; 17,500 °F) and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure is roughly 3,000–4,500 GPa.

This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen.

Jupiter’s Atmosphere

Like most of it’s metrics, Jupiter has the largest atmosphere in our solar system. It spans over 5,000 km (3,000 mi) in altitude. A distinct orange and brown coloration in it’s clouds is caused by an upwelling in compounds that change color as they are exposed to the sun’s ultraviolet light. The exact make up of the clouds is uncertain, but the clouds are thought to be made of phosphorus, sulfur or possibly hydrocarbons.

The colorful compounds have a name, they’re known as chromophores, and they mix with the upper and lower deck of clouds to produce the phenomena we see.

The poles of Jupiter’s atmosphere consistently receive less solar radiation than that at the planet’s equator. This means that convection from the interior of the planet transports energy the poles, which balances out the cloud layers. If this didn’t happen, the poles would be barren of cloud cover.

How Many Moons Does Jupiter Have

Jupiter has at least 67 recorded moons and moonlets. The largest (and most well known) of the four moons are Io, Europa, Ganymede, and Callisto. They’re known as the Galilean satellites, and are most famous for their discovery in 1610 by astronomer Galileo Galilei.

The largest moon in our solar system is Ganymede with a diameter that stretches 3,260 miles or 5,246 kilometers. Io has been known to have active volcanoes and massive lava lakes, and Callisto and Europa are rumoured to have liquid oceans beneath their surface.

Here are the name of Jupiter’s moons and it’s provisional moons:

Jupiter’s moons:

Adrastea, Aitne, Amalthea, Ananke, Aoede, Arche, Autonoe, Callirrhoe, Callisto, Carme, Carpo, Chaldene, Cyllene, Dia, Elara, Erinome, Eukelade, Euanthe, Euporie, Europa, Eurydome, Ganymede, Harpalyke, Hegemone, Helike, Hermippe, Herse, Himalia, Io, Iocaste, Isonoe, Jupiter LI, Jupiter LII, Kale, Kallichore, Kalyke, Kore, Leda, Lysithea, Megaclite, Metis, Mneme, Orthosie, Pasiphae, Pasithee, Praxidike, Sinope, Spond, Thebe, Themiste, Taygete, Thelxinoe, Thyone

Provisional moons: 

S/2017 J 1, S/2016 J 1, S/2003 J2, S/2003 J3, S/2003 J4, S/2003 J5, S/2003 J9, S/2003 J10, S/2003 J12, S/2003 J15, S/2003 J16, S/2003 J18, S/2003 J19, S/2003 J23, S/2011 J1, S/2011 J2

How Does NASA Study Jupiter

Primarily we used Earth based telescopes to study and make observations on our solar system’s largest planet. Space based telescopes have also been used to observe the planet such as the use of Hubble, Pioneer 10, Pioneer-Saturn, Voyager 1, Voyager 2, Ulysses, Galileo, Cassini and New Horizons.

Ulysses, New Horizons, and Cassini missions made fly-bys of the planet as they made their way to destinations beyond our solar system.

Our missions take close up imagery of Jupiter and it’s unique features in order to better understand the planet.

How Does NASA Explore Jupiter

NASA is currently exploring Jupiter with the Juno spacecraft that was launched in 2011. It arrived at the planet on July 4th 2016 and has been sending stunning images back to earth ever since. Juno will help researchers to better understand the composition, evolution, and activity we see in and around the planet.

Juno uses the gravitational field from Jupiter’ magnetic field and naturally occurring radio waves to analyze the planet’s puzzling interior.

Jupiter’s Great Red Spot

Located 22° south of the equator is one of the most intriguing stroms in our solar system, the Great Red Spot. The great red spot is an anticyclonic storm that has been observed in existence since at least 1831, and allegedly as far back as 1655. The great red spot is large enough to easily fit all of planet Earth within it’s boundaries.

The storm itself is large enough that you can see it from Earth if you have a telescope with an aperture of at least 12 cm.

While the storm is believed to be a persistent (and possibly never ending) feature of the atmosphere, it has been decreasing in size since the initial discovery. In the late 1800s it was seen to be as big as 41,000 km (25,500 mi) across. By the time Voyager flew by in 1979 it was recorded as 23,300 km (14,500 mi) across. In 2009 it was shown to be 17,910 km (11,130 mi) across, and our most recent estimates from 2015 show the storm at 16,500 by 10,940 km. This shows that the storm is decreasing in size by roughly 930 km (580 mi) each year.

The great cold spot: In 2017 scientists discovered a great cold spot in Jupiter’s atmosphere. The spot was found at the north pole and is measured at 24,000 km (15,000 mi) across. It has been observed to be 200 °C (360 °F) colder than all it’s surrounding areas. The spot has fluctuated in size and shape over the time we’ve collected data (fifteen years) but has been shown to maintain its relative position at the pole.

Jupiter’s Aurora

While the great red spot is seen as one of Jupiter’s most captivating features, we can’t forget about Jupiter’s stunning aurora.

Similar to here on Earth, Jupiter’s auroras are created when high-energy particles enter the atmosphere near its magnetic poles and collide with atoms of gas.

Due to the strength of the magnetic field on Jupiter the auroras are much larger and hundreds of times more energetic than the ones we see on Earth (Jupiter’s magnetic field is fourteen times as strong as that of Earth). On Earth the most intense auroras are caused by solar storms where charged particles collide with the upper atmosphere. But on Jupiter it’s a different process, whereby the strong magnetic field collects charged particles from it’s surroundings – not just the particles that are created by solar winds – but also particles created by it’s orbiting moons and the particles they throw into space (such as Io’s volcanoes).

The intense field on Jupiter is theorized to be created by eddy currents. Eddy currents are swirling movements of conducting materials within the liquid metallic hydrogen core.

jupiter's aurora
Astronomers are using NASA’s Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the solar system, Jupiter.
Credits: NASA, ESA, and J. Nichols (University of Leicester)

Jupiter And Exoplanets

The existence of Jupiter infers that planets could get even bigger than the one we know as ‘the biggest’. A new category of planets known as Super Jupiters have been observed by Kepler. We’ve found over 300 of these objects since 2015. 

PSR B1620-26 b was the first of the super jupiter’s to be discovered in 2003 (it’s also the oldest known planet in the universe at 12.7 billion years). HD 80606 another super jupiter we found is shown to have the most eccentric orbit of any known planet.

Understanding how large planets can form is important for our understanding of the universe. Research shows that a planet could gain up to 15 times the mass of Jupiter before it were to begin the fusion process under it’s own weight; causing it to become a brown dwarf.

Future Jupiter Missions

The next scheduled mission for Jupiter is JUICE. (JUICE) or the Jupiter Ice Moon Explorer is due to launch in 2022. JUICE is the first large-class mission from the ESA’s Cosmic Vision 2015-2025 programme. JUICE will spend a minimum of three years at Jupiter analyzing the planet and it’s three largest moons (Ganymede, Callisto, and Europa).

NASA’s Europa Clipper mission in 2025 has a more directed mission. It will conduct a detailed reconnaissance of Jupiter’s moon Europa to investigate if the icy moon could harbor conditions that are suitable for life as we know it.

Thermal instruments will survey Europa’s frozen surface in search of eruptions and warmer water near the moon’s surface. The mission will perform 45 flybys of the Jovian moon at altitudes that range from 1700 miles to 16 miles above the surface (2700 kilometers to 25 kilometers).

Jupiter and Mythology

Jupiter has a significant mythological presence throughout ancient times. Being visible to the naked eye at night, and being occasionally seen during the day (when the sun is low) allowed for the planet to be a prominent topic of discussion with many civilizations.

It was represented as the god Marduk to the babylonians and similar to the ancient Chinese discussed above, the planet’s 12 year orbit allowed the civilization to define the constellations for the zodiac calendar.

In Roman mythology Jupiter is the principal god of mythology and the counterpart to Zeus. This is seen in the planets astronomical symbol, ♃, which is a representation of the god’s lightning bolt.

To the Chinese, Koreans, and Japanese Jupiter was known as the ‘wood star’. This was based on the Chinese five elements.

Quick Jupiter Facts

Here’s a quick overview of what we discussed and some brief facts on the largest planet in our system:

  • Jupiter is the fourth brightest object in the solar system
  • Jupiter has the shortest day of all of the planets
  • Jupiter has unique cloud features
  • Jupiter has a thin ring system
  • Jupiter has been visited by eight spacecraft
  • Jupiter’s moon Ganymede is the largest moon in the solar system
  • Jupiter orbits the sun once ever 11.8 Earth years
  • The ancient babylonians were the first to record sightings of Jupiter
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Lauren studies astronomy and physics at NYU.