Moons Of The Solar System

Hypothetical Moon Of Mercury

Mercury is the closest planet to the Sun and lacks any natural satellites. An undiscovered moon orbiting the planet was hypothesized to exist in the early 1970s, but it turned out to be misinterpreted data from the star 31 Crateris. Observation of a moon of Mercury from Earth would be difficult because Mercury is relatively close to the Sun. For example, Mercury was not observed in the infrared spectrum until 1995.NASA‘s MESSENGER spacecraft, which orbited Mercury from 2011 to 2015, did not detect any moon. Mercury’s small Hill sphere limits the potential for a natural satellite to exist.

Moons In The Solar System

There are currently 181 known moons in our solar system orbiting the various planets and dwarf planets. Of the 13 planets and dwarf planets, there are four which don’t have any moons. These are the planets Mercury and Venus, and the dwarf planets Ceres and Makemake.

DiscovererDistance from Planet Diameter Orbital Period Earth: 1 MoonJupiter: 67 MoonsSaturn: 62 MoonsUranus: 27 MoonsNeptune: 14 MoonsPluto: 5 MoonsEris: 1 MoonHaumea: 2 Moons

How Many Moons Are In The Solar System

For millennia, human beings stared up at the night sky and were held in awe by the Moon. To many ancient cultures, it represented a deity, and its cycles were accorded divine significance. By the time of Classical Antiquity and the Middle Ages, the Moon was considered to be a heavenly body that orbited Earth, much like the other known planets of the day .

However, our understanding of moons was revolutionized when in 1610, astronomer Galileo Galilei pointed his telescope to Jupiter and noticed four wandering stars around Jupiter. From this point onward, astronomers have come to understand that planets other than Earth can have their own moons in some cases, several dozen or more. So just how many moons are there in the Solar System?

In truth, answering that question requires a bit of a clarification first. If we are talking about confirmed moons that orbit any of the planets of the Solar System , then we can say that there are currently 173 known moons. If, however, we open the floor to dwarf planets that have objects orbiting them, the number climbs to 182.

The moons, several minor planets and comets of the Solar System, shown to scale. Credit: Antonio Ciccolella

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Even Dwarf Planets Have Moons

Most dwarf planets that have been discovered have at least one moon, such as Pluto’s Charon, Eris’ Dysnomia, Haumea’s Hiiaka and Makemake’s moon S/2015 .

There are several other strange moons that orbit other small dwarf planets, Jupiter trojans, centaurs – there are even asteroids that have not one but several moons!

Our Own Quite Respectable Moon

The moon is about one-fourth the size of Earth the Earth is about 13,000 kilometers in diameter, and the moon is about 3,500 kilometers in diameter. You may think that Earth and the moon are close together, but theyre not: the real distance between Earth and the moon is about 30 Earth diameters away from the moonabout 380,000 kilometers. It looks far away, but we have traversed that gap. The moon is the only place in the solar system that humans have visited, besides our planet.

When we look at the moon, we can see the basics of it. Its surface is dominated by craters, and from those craters, we understand the history of impacts throughout the solar system. When you look at the full moon, you can see that there are some dark regions. These are the marae, which were originally believed to be lunar seas but we now know to be lava-filled plains. A lot of them have circular boundaries around them, indicating that they are lava-filled plains due to very large impacts that punched through the crust of the moon, and the lava then flowed up and filled the circular basin.

Compared to the other large moons of the solar system, our moon is quite respectable. The seven large moons are, in decreasing order of size: Ganymede, Titan, Callisto, Io, our moon, Europa, and Triton. Ganymede, Callisto, Io, and Europa are the four Galilean moons that Galileo saw in 1610. Titan is the large moon of Saturn, and Triton is the large moon of Neptune.

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The Gravity Of The Situation

According to NASA, Mercury is around 41 million miles from the sun. This is a mind-boggling distance, but in space terms, they’re next-door neighbors. Naturally, this means that the enormously hot and enormously dense star has an incredible amount of influence over, and effect on, Mercury.

Being only slightly larger than Earth’s moon, the gravity of Mercury is relatively low. As a result of this and the sun’s own gravity, according to World Atlas, the teeny planet would not be able to keep a grip on any moons that happened to develop. The sun would interrupt and prevent their orbit.

World Atlas goes on to state that Venus, which also has no moons, is a slightly different case. At four-fifths of Earth’s size, it would ordinarily be able to keep any moons in orbit. That website states that Venus is believed to have had a moon at some point in the solar system’s long existence. However, it’s much closer to that pesky life-giving sun than we are, and so any potential moons would reportedly be drawn away.

Which Planets Have Rings

Saturn, Jupiter, Uranus, and Neptune all have rings. Saturns is the brightest though, and therefore the planet most thought of as “ringed” in the popular imagination.

Saturns rings are composed of ice and rock, and some scientists think their formation might have something to do with the planets plentiful moons.

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Are Moons Always Smaller Than Planets

Moons are always smaller than the planet that they orbit . A smaller body always orbits around a larger body rather than the other way around because the larger body has more gravity. However, not all of the moons are smaller than all of the planets. There are seven moons in our Solar System, including our own Moon, that are larger than Pluto. Jupiter’s moon Ganymede is the largest moon in the Solar System, and Ganymede as well as Saturn’s moon Titan are both larger than Mercury and Pluto. Earth’s Moon, Jupiter’s moons Callisto, Io, and Europa, and Neptune’s moon Triton are all larger than Pluto, but smaller than Mercury.

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How Many Moons Does Each Planet Have

Which planet in our solar system has the most moons â Saturn or Jupiter? Learn some interesting facts about each planet’s natural satellites.

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What Is A Moon

Moons also known as natural satellites orbit planets and asteroids in our solar system. Earth has one moon, and there are more than 200 moons in our solar system. Most of the major planets all except Mercury and Venus have moons. Pluto and some other dwarf planets, as well as many asteroids, also have small moons. Saturn and Jupiter have the most moons, with dozens orbiting each of the two giant planets.

Moons come in many shapes, sizes, and types. A few have atmospheres and even hidden oceans beneath their surfaces. Most planetary moons probably formed from the discs of gas and dust circulating around planets in the early solar system, though some are “captured” objects that formed elsewhere and fell into orbit around larger worlds.

Dwarf Planets And Other Bodies:

As already noted, there are several dwarf planets, TNOs, and other bodies in the Solar System that also have their own moons. These consist mainly of the natural satellites that have been confirmed orbiting Pluto, Eris, Haumea and Makemake. With five orbiting satellites, Pluto has the most confirmed moons .

The largest, and closest in orbit to Pluto, is Charon. This moon was first identified in 1978 by astronomer James Christy using photographic plates from the United States Naval Observatory in Washington, D.C. Beyond Charon lies the four other circumbinary moons Styx, Nix, Kerberos, and Hydra, respectively.

A portrait from the final approach of the New Horizons spacecraft to the Pluto system on July 11th, 2015. Credit: NASA-JHUAPL-SWRI.

Nix and Hydra were discovered simultaneously in 2005 by the Pluto Companion Search Team using the Hubble Space Telescope. The same team discovered Kerberos in 2011. The fifth and final satellite, Styx, was discovered by the New Horizons spacecraft in 2012 while capturing images of Pluto and Charon.

In addition, it is unusual in that each body is tidally locked to the other. Charon and Pluto always present the same face to each other and from any position on either body, the other is always at the same position in the sky, or always obscured. This also means that the rotation period of each is equal to the time it takes the entire system to rotate around its common center of gravity.

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The Many Moons Of The Solar System

Per Astronomy, the planets of the solar system acquired their moons in different circumstances. The solitary moon of Earth is believed to have resulted, according to the magazine, when another body struck the planet. The force of such an impact would have split small pieces from the whole, which then would have come together to form Neil Armstrong’s famous stomping ground.

Further out in the reaches of the solar system, meanwhile, the outlet states that “Jupiter, Saturn, Uranus, and Neptune … form like solar systems in miniature.” Further away from the formidable gravity of the sun, chilly fragments of dusty gas and ice formed these vast planets, and it’s believed that the remainders became multiple moons. Per USA Today, Saturn has the most moons in the solar system: 82, though 29 of them are dubbed provisional moons prior to further study.

Mercury, for its part, is deemed a terrestrial planet, meaning that it boasts a solid surface characteristic of those worlds closer to the sun. It seems to lack any moons because of its sheer proximity to that most famous of stars.

The Solar System’s Major Moons

NASA / JPL-Caltech / Montage by Emily Lakdawalla. The Moon: Gari Arrillaga. Processing by Ted Stryk, Gordan Ugarkovic, Emily Lakdawalla, and Jason Perry.

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The Most Amazing Moons In The Solar System

There are currently 174 named moons in our Solar System, orbiting the six outermost planets, with more being discovered and debated every day. Some are more fascinating than others, whether its their landscapes, features, orbits or environments – so we ranked our top 20 most interesting moons, because, well, why not

Orbits: Asteroid 243 Ida

Discovered in 1995 by the Galileo probe, this moon is less than a mile in diameter and is the natural satellite to the asteroid Ida, a Koronis asteroid located in the belt between Mars and Jupiter. Before this, scientists had no evidence that asteroids could have moons, but since its discovery a further 24 have been found to orbit them.

The origin of the unorthodox moon is debated, and could either be from the asteroid itself, or a captured object.

How Many Moons Does Saturn Have

Saturn has 82 moons. Of those, 53 are confirmed moons, and 29 are provisional, meaning they need to be confirmed by additional observation.

A moon is defined by NASA as a “natural satellite,” usually a solid body, without an atmosphere — though a few, like Earth’s, do have atmospheres. The majority of planetary moons likely were formed from the “rings” or discs of gas and dust circling planets early on in the solar system.

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Largest And Smallest Moons:

The title for largest moon in the Solar System goes to Ganymede, which measures 5262.4 kilometers in diameter. This not only makes it larger than Earths Moon, but larger even than the planet Mercury though it has only half of Mercurys mass. As for the smallest satellite, that is a tie between S/2003 J 9 and S/2003 J 12. These two satellites, both of which orbit Jupiter, measure about 1 km in diameter.

An important thing to note when discussing the number of known moons in the Solar System is that the key word here is known. With every passing year, more satellites are being confirmed, and the vast majority of those we now know about were only discovered in the past few decades. As our exploration efforts continue, and our instruments improve, we may find that there are hundreds more lurking around out there!

For more information, be sure to check out NASAs Solar System Exploration page.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

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Use these up-to-date tables to learn about the moons of the solar system, including the plethora of Jupiters moons and the weird menagerie of Saturns moons.

NASA / JPL / Space Science Institute

Discovering a new moon in the solar system used to be a rare event. After Gerard Kuiper found Miranda, a moon of Uranus, in 1948 and Seth Nicholson found Ananke, a moon of Jupiter, in 1951, the total count of natural planetary satellites stood at 31: Jupiter’s moons numbered 12, followed by the moons of Saturn , Uranus , Neptune , Mars , and Earth .

In the ensuing three decades, finding solar system moons largely fell to NASA spacecraft. After Voyager 2’s flyby of Neptune in 1989, the total number of solar system moons had nearly doubled to 60. However, the advent of sensitive electronic cameras has put ground-based observers back in the driver’s seat, resulting in several dozens of finds over the past few years.

Indeed, some of the new objects are so small, only a few kilometers across, that they stretch the traditional notion of what constitutes a “moon.” Sometimes faint objects appear fleetingly in images and are never seen again others require patient follow-up observations over months or years to confirm that they orbit a planet.

NASA / ESA

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What Planet Rains Diamonds

This sounds like a question straight out of a sci-fi novel. Astoundingly, it has basis in reality. On Uranus, Neptune and Saturn scientists believe there is likely diamond rainfall.

On Saturn, a video from BBC Earth describes a scenario where soot clouds, deep in the planet, reach such a point of pressure that the chunks of soot turn to diamonds.

American Scientist also reports that scientists have believed diamond-rain to be a phenomenon on both Neptune and Uranus, but since the planets are so far away, on the outer fringes of the solar system, it has been difficult to study.

Galactic Collision And Planetary Disruption

Although the vast majority of galaxies in the Universe are moving away from the Milky Way, the Andromeda Galaxy, the largest member of the Local Group of galaxies, is heading toward it at about 120 km/s. In 4 billion years, Andromeda and the Milky Way will collide, causing both to deform as tidal forces distort their outer arms into vast tidal tails. If this initial disruption occurs, astronomers calculate a 12% chance that the Solar System will be pulled outward into the Milky Way’s tidal tail and a 3% chance that it will become gravitationally bound to Andromeda and thus a part of that galaxy. After a further series of glancing blows, during which the likelihood of the Solar System’s ejection rises to 30%, the galaxies’ supermassive black holes will merge. Eventually, in roughly 6 billion years, the Milky Way and Andromeda will complete their merger into a giant elliptical galaxy. During the merger, if there is enough gas, the increased gravity will force the gas to the centre of the forming elliptical galaxy. This may lead to a short period of intensive star formation called a starburst. In addition, the infalling gas will feed the newly formed black hole, transforming it into an active galactic nucleus. The force of these interactions will likely push the Solar System into the new galaxy’s outer halo, leaving it relatively unscathed by the radiation from these collisions.

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