Jupiter is a colossus among the planets in our solar system.

Everything about Jupiter is extreme. The Great Red Spot is an anticyclonic storm  three times the size of Earth and has been raging for at least 350 years.

With a magnetic field 20,000 times stronger than that of Earth, the radiation surrounding the planet is 1000xs the lethal dose for a human, damaging even heavily shielded space probes.

Jupiter is so big you could fit all the other planets inside it and is far closer to becoming a star than it is to being a planet like Earth.

Stars are formed because gravity causes hydrogen and helium to undergo pressure-induced fusion. Earth is roughly a million times smaller than the Sun, but Jupiter is only a thousand times smaller. And yet, if Jupiter was just 20xs bigger it would be considered a brown dwarf star. At 80-100x bigger, Jupiter would undergo fusion and shine as a red dwarf with enough light to allow you to read at night. As it is, Jupiter already glows when viewed in infrared light!

Jupiter is a vacuum cleaner, sucking up debris.

Jupiter shields the inner planets from asteroids, shepherding asteroids and keeping them in stable orbits around the Sun.

Without Jupiter, asteroid impacts like those that wiped out the dinosaurs could be so frequent complex life would never have evolved here on Earth.

At first, this animation might look a little confusing and counterintuitive, but it’s a fantastic example of how gravity shapes space.

Notice the different orbital speeds. Close to the Sun, Mercury is like a race car. Venus is slightly slower, then Earth, then Mars, then the Hilda family of asteroids (in magenta) and the Greeks (in front of Jupiter) and the Trojans (trailing Jupiter).

Space isn’t flat. Picture the animation above occurring in the fundraising coin well below and you’ll get a good mind-picture of how gravity works.

Space is like a coin well, only there's no friction so the coins keep going around and around and around

Space is like a coin well, only there’s no friction so the coins keep going around and around and around

Imagine Jupiter as a bowling ball rolling around a trampoline. Anything that gets too close is going to get sucked in. But what about objects that aren’t too close and are also in motion on our trampoline? How will they behave? Remember, in space there’s no such thing as being stationary. Everything’s in motion, and so asteroids find themselves in equilibrium with Jupiter and the Sun and appear to “sit” in the Lagrange points (in green) on either side of Jupiter.

If we take another perspective, imagining we’re in motion directly above Jupiter as it orbits the sun, then the massive planet appears stationary and we get an idea of how these asteroids have stabilized in their orbits.

The triangular shape of the Hilda family of asteroids is an illusion. Each individual asteroid is in a highly elliptical orbit, but there’s so many of them crisscrossing each other they give the appearance of a triangle relative to the Lagrange points.

Without Jupiter the inner solar system would be chaotic

Without Jupiter the inner solar system would be chaotic

The (green) Greek and Trojan asteroids on either side of Jupiter are in motion around the Sun at roughly the same rate as Jupiter and are held in these spots by the way gravity balances between Jupiter and the Sun (which are roughly equidistant from these clouds of asteroids).

Being in a lower, closer and faster orbit to the Sun, the Hilda asteroids “bounce” between these Lagrange points and the point directly opposite Jupiter.

topographical map

Topographical maps help us imagine three dimensions in two

If we compare Lagrange points to topographical maps, “Able Hill” and “Baker Hill” would be our two (green) Lagrange points with the Greek and Trojan asteroids sitting on the hilltops. Jupiter would be in the valley in-between, while the Sun would be down at sea level. The Hilda asteroids are like ball bearings rolling around in the valleys.

Jupiter’s phenomenal size gives it a massive influence over the distribution of asteroids in our solar system, protecting Earth for billions of years and allowing life to flourish.


Picture credit:NASA. The moon Io orbits high above the clouds of Jupiter

Looking up into the night sky, Jupiter appears insignificant, little more than a tiny dot in the darkness, but it has played a dominant role in shaping our solar system and may be the key to why life was able to avoid being peppered by asteroids. Without Jupiter, Earth might be a planet full of microbes and nothing else.

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