Jupiter

Big and easy to find

Jupiter, the fifth planet from the Sun, stands as the behemoth of our Solar System. With a diameter of about 143,000 kilometers, it is more than 11 times the width of Earth and has a mass 318 times greater.

One of the most remarkable features of Jupiter is its visibility in the night sky. It is the third brightest object, after the Moon and Venus, and is often visible to the naked eye even in light-polluted urban areas. Its brilliance results from its massive size and highly reflective cloud cover, making it an easy find for stargazers and astronomers alike. You can easily spot Jupiter as a bright, steady point of light in the night sky, distinguishable from the stars due to its lack of twinkling (remember the song Twinkle, Twinkle Little Star?).

Find some modest binoculars, and you can see the four Galilean moons—Io, Europa, Ganymede, and Callisto—appear as tiny, star-like points of light lined up perfectly around the planet. It is a wonderful spectacle. Using a small telescope reveals even more detail, including Jupiter's cloud bands and the Great Red Spot. The planet's brightness and large apparent size, combined with the relatively close and synchronous orbits of the moons, make Jupiter and its moons easy to locate and observe. It's a treat for anyone, even the most amateur of astronomers.

NASA/JPL/University of Arizona, Public domain, via Wikimedia Commons

Beautiful stormy skies

The atmosphere of Jupiter is a complex and dynamic system. It is characterised by its striking cloud bands and the Great Red Spot, which in fact is actually a gigantic storm. The cloud bands, which run parallel to the planet’s equator, consist of ammonia clouds at different altitudes. These bands exhibit varying colours, from white to brown, and are a product of chemical reactions occurring within Jupiter's atmosphere. The alternating bands are known as zones (the lighter regions) and belts (the darker regions), and are driven byJupiter's rapid rotation and complex internal heat dynamics.

Jupiter's atmosphere is incredibly turbulent, with wind speeds reaching up to 360 kilometers per hour (225 miles per hour). The most iconic feature of this turbulent atmosphere is the Great Red Spot. This colossal storm, larger than Earth itself, has been raging for at least 193 years. The Red Spot is a high-pressure region in Jupiter's atmosphere—its reddish colour is thought to be caused by complex organic molecules, ammonia, or other chemicals being lifted from deeper within Jupiter's atmosphere by the storm, and then exposed to strong radiation by the Sun.

Kevin Gill from Los Angeles, CA, United States, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles, Public domain, via Wikimedia Commons

Intense flashes of lightning have also been observed in Jupiter’s atmosphere, with electrical discharges many times stronger than those seen on Earth.

Jupiter's other prominent feature, the Great Red Spot, measures about 16,350 kilometers (10,159 miles) in width, although it has been shrinking over the past century. Its origins are still a subject of research, but it is believed to have formed from the planet’s internal heat and rapid rotation, which drive the atmospheric turbulence necessary for such a storm to persist for centuries. Yes, you read that correctly—centuries!

Beneath the clouds

Jupiter is mainly composed of hydrogen and helium, much like the Sun. The internal structure of Jupiter, however, is not fully understood due to its thick atmosphere and lack of a solid surface. The planet is believed to have a core composed of heavier elements, surrounded by a layer of metallic hydrogen, followed by a layer of molecular hydrogen and helium.

The core of Jupiter is still a subject of scientific debate, but it is estimated to be about 10 to 20 times the mass of Earth. Above this core lies a thick layer of hydrogen, crushed under such extreme pressures at the planet’s centre that it becomes metallic. This layer, therefore, conducts electricity and is likely responsible for Jupiter’s powerful magnetic field, which is the strongest of any planet in the Solar System.

NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill, Public domain, via Wikimedia Commons

It's also worth realising that standing on Jupiter’s “surface” would be an impossible task, because the planet lacks a solid surface as we know it. As you descend through Jupiter's atmosphere, the gases become denser and hotter, eventually transitioning into a supercritical fluid due to the intense pressure. Any spacecraft attempting to land would be both crushed and melted long before reaching any solid core!

Jovian moons

Callisto is the most heavily cratered object in the solar system, its ancient surface bearing the scars of countless impacts which occurred over billions of years. It is the least geologically active of the Galilean moons, and its surface has remained relatively unchanged. However, Callisto might also have a subsurface ocean, maintained by a combination of residual heat from its formation, and the slight tidal forces which are exerted by Jupiter.

NASA/JPL/DLR, Public domain, via Wikimedia Commons

Europa is renowned for its smooth, icy surface and is considered one of the most promising places to search for extraterrestrial life. Beneath its ice crust, estimated to be 15 to 25 kilometers (10 to 15 miles) thick, lies a subsurface ocean of salty water. The tidal forces exerted by Jupiter create heat, which prevents the ocean from freezing solid. In contact with Europa’s rocky mantle, this ocean could provide the necessary conditions for life, perhaps similar to the life that flourishes in the deepest parts of our oceans, around hot submarine geysers called Black Smokers.

Jupiter is orbited by more than 90 moons (with more being discovered all the time!) but four of these stand out due to their significant size and unique features: Io, Europa, Ganymede, and Callisto. These moons, known as the Galilean moons, were first observed by Galileo Galilei in the year 1610.

Io is the most volcanically active body in the Solar System. Its surface is dotted with hundreds of volcanoes, some erupting with lava fountains reaching up to 500 kilometers (310 miles) from the surface, beyond Io's atmosphere and into space. This intense volcanic activity results from tidal heating, caused by the gravitational pull of Jupiter and the other Galilean moons.

Ganymede is the largest moon in the Solar System, and is even bigger than the planet Mercury. Ganymede is also unique among moons in having a magnetic field, and its surface is a mixture of two types of terrain: highly cratered dark regions, and lighter regions which are marked with grooves and ridges, indicating tectonic activity. Ganymede also likely harbours a subsurface ocean beneath its icy crust.

Conducting the Solar System

Jupiter plays a crucial role in the architecture of our Solar System. Its immense gravity has shaped the orbits of other planets and debris, acting as a gravitational shield for the inner planets by capturing or deflecting comets and asteroids that might otherwise impact Earth. This protective effect has likely influenced the development and evolution of life on our planet.

Additionally, Jupiter's formation and subsequent migration influenced the distribution of materials in the early Solar System, contributing to the formation of other planets and the Asteroid Belt. The moons of Jupiter, particularly Europa, have become focal points in the search for life beyond Earth, offering insights into the potential for habitable environments elsewhere in our galaxy.

In summary, Jupiter is not just a massive planet; it is a cornerstone of our Solar System's dynamics and a fascinating world of its own. From its bright presence in the night sky, to its complex atmospheric phenomena and diverse moons, Jupiter continues to captivate and challenge our understanding of planetary science.

NASA/JPL-Caltech/ASU, Public domain, via Wikimedia Commons

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How to see Jupiter

Jupiter is one of the five planets visible to the naked eye from Earth. It appears as a bright "star" in the night sky.

• Naked eye: Jupiter can be seen without any equipment. It appears as a bright, steady point of light. The best times to observe Jupiter are during opposition, when it is closest to Earth and directly opposite the Sun in the sky.

• Binoculars: Using binoculars, you can see Jupiter as a small disc and observe its four largest moons: Io, Europa, Ganymede, and Callisto. These moons appear as tiny points of light lined up around the planet.

• Small telescope: A small telescope allows you to see Jupiter's cloud bands and the Great Red Spot. During opposition, you can observe these features more clearly and even see the dynamic changes in Jupiter's atmosphere.

Jan Sandberg, Attribution, via Wikimedia Commons