Jupiter is the fifth planet of the Solar system. It is the largest planet and the most massive. Jupiter has been identified as a planet by Babylonians astronomers around 7th-8th century BCE. It is named after the Roman God of thunder Jupiter, the father of all gods and humans. Unlike Earth, which is made of rock, Jupiter is a gaseous giant. So, apart from beautiful images, Jupiter offers plenty of fun-facts. Let’s see these below.
Jupiter in numbers
Jupiter orbits the Sun at a mean distance of 778.57 million km (5.2 times the distance between the Earth and the Sun). One year in Jupiter lasts ~11.9 years, but one day is 9 hours, 55 minutes, and 30 seconds.
Jupiter is more massive than all the planets of the Solar system combined. Its mass is ~1.9×1027 kg (317.8 of Earth’s mass or around one-thousandth of the Sun’s mass). The planet has a radius of 69,911 km and a mean density of 1.326 g/cm3. This corresponds to a surface gravity of 2.528 g.
Jupiter doesn’t have a solid surface, thus the mean temperature of the planet is strongly related to the depth from its surface. For example, at a pressure of 0.1 bar, the mean temperature of Jupiter is -161° C (-257.8°F), while at a pressure of 1 bar, it is -108°C (-162.4°F).
Our planet has just one natural satellite, the Moon. Jupiter has 79 satellites, and four of them have attracted our interest. These are known as the Galilean satellites (Io, Europa, Ganymede, and Callisto). The quartet was discovered in 1610, and it was the first time that we had observational evidence of an object orbiting around another, other than Earth, as the geocentric model was considering.
Formation and structure
Jupiter is a gaseous planet, so the rocky planet structure (crust, mantle, and core) is not applicable, since gaseous planets do not have a surface. Thus, when you observe Jupiter, what someone can see, is the top of its clouds. The composition of Jupiter’s atmosphere is 89% hydrogen, 10% helium, 0.3% methane, 0.026% ammonia, and smaller traces of water. The most obvious characteristic of Jupiter’s atmosphere is its division in numerous parallel banded stripes. The dark ones are called belts, while the lighter ones are zones. These structures circulate the planet in opposite directions.
The belts and zones of Jupiter form due to convection in Jupiter’s atmosphere. Clouds in the upper layers of the atmosphere form dense ammonia ice clouds, which is responsible for the lighter color of the zones. The belt clouds are thinner and they are located at lower altitudes. The nature of the belts is not clearly known, but it could be due to molecules of sulfur, carbon, and phosphorus.
Perhaps the trademark of Jupiter is the Great Red Spot. This is an anticyclonic storm that is much larger than Earth. Its existence is known from the 17th century. The giant oval-shaped structure rotates counterclockwise with a period of about six days. The feature is visible even with small telescopes from Earth. Models of the storm suggest that it is stable and most likely is a permanent feature of the planet. However, since its discovery, its size has decreased. The first known measurement in the late 19th century showed that it was 41,000 across. In 1979, when Voyager arrived, the Great Red Spot was 23,000 km across and 13,000 km wide. Sixteen years later, observations with the Hubble Space Telescope showed that its size decreased again (20,950 km), while in 2009, its size was 17,910 km. Finally, the dimensions of the storm by 2015, have decreased down to 16,500 by 10,940 km, thus decreasing in length by about 930 km every year.
Unlike Earth, which has a mantle, Jupiter has a region made up of liquid metallic hydrogen. Under the conditions of extreme pressure, hydrogen atoms lose their electrons, thus the liquid can behave as a metal. At this point, the temperature in Jupiter’s interior is around 10,000°C, which is higher than the Sun’s surface.
It is still not clear if Jupiter has a rocky core or not. Even if Jupiter had a core at its formation stage, it could have been eroded by currents of the liquid metallic hydrogen. But it is also possible that Jupiter never had one.
The key to this is the formation of the planet. All planets grew from gas and small dust particles, that were in a disk form around the early Sun. Through collisions and clumping bigger and bigger structures were forming, which led eventually to the planets we know today.
If Jupiter formed from the bottom to top, then Jupiter might (or even may) have a core. But if Jupiter formed from big clumps of gas in a top-to-bottom formation, then Jupiter might have no core at all.
Jupiter has the second strongest magnetic field in the Solar system. It is fourteen times as strong as that of Earth, and its intensity varies from 10 to 14 gauss at the poles, to 4.2 gauss at the equator. The origin of the magnetic field is due to swirling movements of conducting materials within the liquid metallic hydrogen core.
In our Solar system, Saturn is the undisputed lord of the rings. Jupiter has a ring system too, but it was only discovered in 1979 when Voyager 1 flew by the gaseous giant. This faint ring system is composed of small dark particles, that are difficult to observe when they are backlitted by the Sun. Data from the Galileo spacecraft indicate that the ring system of Jupiter most likely formed by dust. The source of the dust comes from meteoroids that impact the innermost satellites of Jupiter.
- Jupiter’s diameter is 11 times greater than Earth’s, but it is also ten times smaller than the Sun’s.
- Jupiter is 2.5 times more massive than all planets of the Solar system combined.
- Jupiter’s mass is 1050 smaller than the Sun, thus calling Jupiter a failed star is incorrect.
- If you add up the mass of 80 Jupiters, then yes you will get a star.
- Jupiter spins faster than any other planet in the Solar system.
- Jupiter radiates more heat itself than it receives from the Sun.
- In 1994 we were able to observe live the impact of comet Shoemaker-Levy 9 on Jupiter’s atmosphere.
- In Astronomy, the center of mass of two or more bodies that orbit one another is called the barycenter, and this is the point at which the two or more bodies orbit. The Jupiter-Sun barycenter is not at the Sun’s center as you might expect, but it is located at a distance of 1.07 Solar radii, thus it is outside the Sun.
- Jupiter’s moons Europa, Ganymede, and Callisto, together with Saturn’s Titan are our only hope to find life in the Solar system outside our planet.
- Jupiter has powerful storms that are often accompanied by lightning. The storms result from the evaporation-condensation cycle of water, and they are much more powerful than those on Earth.
Since the 70s, plenty of probes flew by or visited Jupiter. The first one was Pioneer 10, which encountered the planet on the 6th of November 1973 and returned the first images of the planet and its moons. Pioneer 10 was the first artificial satellite that achieved the escape velocity for leaving the Solar system. A year later Pioneer 11 flew by and explored the environment of Jupiter on its way to Saturn.
Six years later, the Voyager missions flew by Jupiter towards their trip to the edge of the Solar system. The twin probes improved our understanding of the Galilean moons, and they discovered the ring system of Jupiter. They also confirmed that the famous Great Red Spot is anticyclonic in nature, and it changed hue since the visit of the Pioneer missions turning from orange to dark brown. Voyager also discovered the volcanoes in Io, which was something unexpected. Additionally, a torus of ionized atoms was discovered along the orbital path of Io, and the probes observed flashes of lightning in the night-side of the atmosphere.
The first probe to orbit Jupiter was Galileo. The spacecraft entered orbit on the 7th of December 1995, and for seven years conducted flybys to all Galilean moons. An atmospheric probe was released from the spacecraft and it entered Jupiter’s atmosphere. It went down 150 km and collected data for almost an hour (contact was lost at a temperature of 153°C and a pressure of 23 atmospheres). The whole Galileo had the same fate, since it was carefully crashed on Jupiter. This was done to protect Europa because it is considered one of the best candidates where life may exist outside Earth. Data from Galileo revealed that hydrogen composes up to 90% of the atmosphere of Jupiter, while wind speeds up to 644 km/h were measured before the probe got destroyed.
Two years from now, the ESA’s Jupiter ICy moons Explorer (JUICE) will visit three of Jupiter’s Galilean moons: Ganymede, Callisto, and Europa. The three targets were chosen because we believe that they have significant amounts of liquid water beneath their surface, making them potentially habitable environments.