79 Moons

Fifth away from the Sun, Jupiter is the biggest planet (1,300 times the size of Earth) in the solar system. Jupiter is very cold (effective temperature -148 degrees Celsius) and made up mainly of hydrogen and helium -- hence it’s coined the ‘gas giant’. It is because of its relatively light mass that Jupiter is considered a planet, as it does have the mass needed to be qualify as a star. Its similar composition to the Sun suggests that Jupiter was one of the earliest planets formed, using the remainder of the gases formed by the Sun.


So how did Jupiter’s ‘newest’ moons go unnoticed? One reason is that these moons are really small: no more than 1-3 kilometers in diameter. Another reason is Jupiter’s brightness - Jupiter is the brightest planet in our solar system and its glare makes it difficult to see moons as small as the latest 12. Upgraded telescope technology (such as the Dark Energy Camera) removed this problem. Finally, these moons aren’t new, they’re 4 billion years old - meaning that these moons may not have been in orbit as individual bodies but may have broken off in collisions with other moons, asteroids or comets.


In 2011, NASA launched the Juno Mission with the aims of understanding what lies beneath the clouds of Jupiter. As of 2011, 53 of Jupiter’s moons were named and another 14 moons are known. It took 5 years for the Juno satellite to make it to Jupiter and one of the biggest discoveries since then is that Jupiter has 12 more moons than previously thought - bringing the total up to 79 moons.10 of these moons are in the retrograde orbital group and the 2 are in the prograde orbital group (pictured).

Photo: Roberto Molar-Candanosa, Carnegie Inst for Science

One of these new moons in retrograde orbit, Valetudo (Jupiter’s ‘oddball’ moon), is described as being on a ‘suicide orbit’ going the opposite direction of other Jovian bodies in the retrograde group, and is particularly, destined to collide with other bodies in Jupiter’s orbit; such a collision will apparently be visible from earth (but collisions are not frequent). So don’t hold your breath, it’s not likely to happen any time soon.


The Juno Mission is set to return by 2021 so there’s no doubt that much more will be discovered; we’ll keep you updated.


More on Jupiter and its moons:

Jupiter has 10 more moons we didn't know about — and they're weird (Nature News) by Alexandra Witze

Juno Overview by NASA

12 New Moons Found Orbiting Jupiter by National Geographic

Astronomers discover 12 new moons orbiting Jupiter - one on collision course with the others (Guardian) by Ian Sample

A dozen new moons of Jupiter discovered, including one 'oddball' (Science Daily) by Carnegie Institution for Science


By Tomi Akingbade, Founder

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