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THE SOLAR SYSTEM'S TWENTY LARGEST OBJECTS
Greetings, planet pickers! Welcome to Bob
the Alien's Top of the Solar System! The Solar System is full of
thousands of objects of various shapes and sizes - some unimaginably
huge and some extremely tiny. Here is our rundown of the twenty
largest items in the Solar System.
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THE SUN
 |
| WIDTH ACROSS EQUATOR
(DIAMETER) |
1,392,000
kilometres
865,000 miles |
| CLASSIFICATION AND LOCATION |
Yellow dwarf star, centre
of the Solar System |
|
Topping of
our charts for what seems like an eternity and the undisputed holder
of the title of Official Largest Object in the Solar System
is everybody's favourite star, the Sun! At a width of
1,392,000
km (865,000 miles)
and weighing in at
1,989,000,000,000,000,000,000,000,000,000 kilograms (whoever weighed
it must have some pretty big scales!), the Sun is large enough to
contain every single other object in the Solar System and is set to
get even bigger as it gets older. It is almost ten times wider than
the next largest object in the Solar System, which is...... |
JUPITER
|
 |
| WIDTH ACROSS EQUATOR |
142,984 kilometres / 88,846 miles |
| CLASSIFICATION AND LOCATION |
Gas Giant. Fifth planet from The Sun, first of
the Outer Planets |
| By Jove, it's Jupiter! Yes, second
in our chart is the Solar System's largest planet and the first of
the Gas Giants. Jupiter is a world made mostly of gas (hydrogen and
helium if you're interested), hence the reason why it's called a Gas
Giant. Scientists think that it may have a solid core surrounded by
liquid metallic oceans, but they don't know for sure. In fact,
they're probably just guessing. It could have a chocolate centre for
all they know. Jupiter is a stormy world, with one storm in
particular - The Great Red Spot - having raged for at least four
hundred years. Keeping Jupiter company are at least
63 moons. Don't
be surprised if some of them pop up later in this list. |
 |
SATURN
 |
| WIDTH ACROSS EQUATOR |
120,536 kilometres / 74,900 miles |
| CLASSIFICATION AND LOCATION |
Gas Giant. Sixth planet
from the Sun, second of the Outer Planets. |
| Jupiter's not-so-near neighbour is
Saturn and it takes bronze position in this leaderboard of the Solar
System's giants. Whoever or whatever created the Solar System seemed
to like Saturn so much that they put a
ring on it! With a similar
gassy composition to Jupiter,
Saturn also has a multitude of
moons
of all shapes and sizes orbiting it. Its diameter is 120,536 kilometres (74,900 miles), but
if we take into consideration its ringspan, Saturn's diameter more
than doubles to a whopping 270,000 km (168,000 miles). |
URANUS
 |
 |
| WIDTH ACRrOSS EQUATOR |
51,118 kilometres / 31,763 miles |
| CLASSIFICATION AND LOCATION |
Gas Giant. Seventh planet from the Sun, third of
the Outer Planets |
| Fourth on our list is the rather dull and
featureless Uranus. But what it lacks it looks, it makes up in
peculiarity. At some point in its history, Uranus fell over. Either
this was because another large object collided with it and knocked
it over, or it just felt like being different. Whatever happened,
Uranus appears to orbit on its side, as if it is rolling around the
Sun. Scientists are easily excitable creatures, and the effects of
Uranus' sideways orbit excites them greatly. You see, its orbit
causes Uranus to have an 'interesting' magnetic field, day and night
to last forever (42 years), and its moons to orbit up and under the planet. |
 |
NEPTUNE
 |
| CLASSIFICATION AND LOCATION |
49,532 kilometres / 30,779 miles |
| WIDTH ACROSS EQUATOR |
Gas Giant. Eighth and most distant regular planet
from the Sun, fourth of the Outer Planets. |
| When it was discovered in 1851,
Neptune, the fifth
object on our list, was the most distant planet in the Solar System.
It lost its claim to this title in 1930 when
Pluto was discovered,
briefly regaining it for a few years in the late 1990s due to
Pluto's weird orbit. However, when Pluto was permanently thrown out
of the Planet Gang* in 2006 for being too strange, Neptune was once
again given the title of Official Most Distant Planet in the Solar
System (remember that if you're doing 'space travel brochures' kids!).
Neptune is the last of the
Gas Giants, representing the
end of the region of the Solar System dominated by the huge gassy
worlds. *Note: The Planet Gang doesn't actually exist. I just made
it up. |
EARTH
 |
 |
| WIDTH ACROSS EQUATOR |
12,756 kilometres / 9,926 miles
|
| CLASSIFICATION AND LOCATION |
Inner Planet. Third planet
from the Sun. |
| At number six is the Solar System's most unique, most special
and most interesting object. It's none other than your home. Well,
obviously, not your actual house, but the world on which it is
situated. It's Earth, the first object in this chart with a solid
surface, and therefore the first place you can actually stand on.
The presence of water on its surface, a breathable atmosphere, a
suitable climate and protection from the Sun's dangerous rays are
all factors that allow Earth to be the ideal place for
life. The
planet is now home to countless lifeforms, and you are of course one
of them! But, take care of Earth, because there's nowhere else to
go. |
 |
VENUS
|
| WIDTH ACROSS EQUATOR |
12,104 kilometres / 7,521 miles |
| CLASSIFICATION AND LOCATION |
Inner Planet. Second planet
from the Sun. |
| With a size, mass, gravity and composition similar to
Earth, Venus is
often seen as its slightly smaller twin. If it is
Earth's twin,
Venus is most definitely an evil one. Something went drastically
wrong with Venus at some point. If you were able to stand on its
surface, you would be crushed, suffocated, cooked and pretty much
doomed. Venus' surface pressure is similar to being 1km below water
on Earth. Its atmosphere contains poisonous carbon dioxide, clouds
contain sulphuric acid and temperatures are about 400c, hot enough
to melt lead. And, even if you could survive, the fact that a day on
Venus is longer than its year, and that it spins the wrong way, will
just mess with your head! It's little wonder that
Venus hides it
horrors under a cover of deceptively beautiful clouds. |
MARS
 |
 |
|
WIDTH ACROSS EQUATOR |
6,794 kilometres / 4,222 miles |
|
CLASSIFICATION AND LOCATION |
Inner Planet. Fourth Planet from the Sun. |
|
Now this is more like it! Forget Venus and its inhospitality.
Mars is much more accomodating, and over the years, the Red Planet has
welcomed visitors aplenty, allowing rovers to drive across its surface,
take pictures, poke its rocks and analyse its soil. Even so, it's
still not somewhere that you'd go to in a hurry. With an unbreathable atmosphere, no water to drink
(well, perhaps a small amount) and temperatures that are
chilly to the extreme, Mars is not really the best place for a day
out.
That's not to say that life over there has been completely ruled
out. Scientists continue to find evidence that could suggest that
life could be or could have been possible on
Mars. |
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GANYMEDE
 |
| WIDTH ACROSS EQUATOR |
5,262 kilometres / 3,270 miles |
| CLASSIFICATION AND LOCATION |
Moon of Jupiter. Eighth
closest moon to Jupiter, third of the Galilean satellites. |
| Unbelievably, the ninth and tenth largest objects in the Solar
System happen to be moons. Well, I found it quite unbelievable when
I found out. The Solar System's largest moon is Ganymede which
orbits the Solar System's largest planet, Jupiter. Large enough to
have been spotted by Galileo Galilei in 1610 through one of the first
telescopes, Ganymede's surface is a mixture of extremely ancient and
slightly less extremely ancient. Part of it is heavily cratered,
much like many moons, whereas parts are much smoother, suggested
some sort of geological disturbance occurred after the period of
heavy bombardment. Scientists reckon that deep below the surface,
there may be water. |
TITAN
|
 |
|
WIDTH ACROSS EQUATOR |
5,510 kilometres / 3,200 miles |
|
CLASSIFICATION AND LOCATION |
Moon of Saturn. Twenty-first moon in orbit of the planet |
|
The tenth largest object in the Solar System is
Titan, the Solar
System's second largest moon which orbits the Solar System's second
largest planet, Saturn. What makes
Titan unique is that it is the
only moon in the Solar System to possess an atmosphere. And what an
atmosphere it does possess! In fact, to be able to see through it, a
probe had to be send to its surface to take pictures. Images sent
back from the Huygens probe which landed in 2005 - along with radar
imagery from the Cassini orbiter - revealed Titan to possess lakes of
liquid methane. As well as methane in its atmosphere and frozen
methane on its surface, the element plays a similar role on
Titan as
water does on Earth. Scientists sometimes consider
Titan to be
similar to an early Earth and some even consider the possibility of
life there. |
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MERCURY
 |
| WIDTH ACROSS EQUATOR |
4,878 kilometres / 3,031
miles |
| CLASSIFICATION AND LOCATION |
Inner Planet. Closest
planet to the Sun. |
| Because we're no longer allowed to call
Pluto a planet, the
final planet to feature in our chart, and therefore the smallest, is
Mercury. Whizzing around the
Sun in just 88 days, Mercury is
scorched by the star on is sunlit side, yet is colder than cold on
its 'night' side, its lack of atmosphere preventing the retention
and dispersal of any of the heat that the planet receives. |
CALLISTO
 |
 |
|
WIDTH ACROSS EQUATOR |
4,821
kilometres / 2,996 miles |
|
CLASSIFICATION AND LOCATION |
Moon of Jupiter. Ninth closest moon to Jupiter, fourth of the
Galilean satellites. |
|
It's back to Jupiter for now with
Callisto occupying
twelth spot in our list. Callisto is the fourth of the
Galilean
satellites, Jupiter's four largest moons discovered by Galilei in
1610. Callisto is heavily cratered like most moons, but the rings
around its craters appear quite bright suggesting that ice may be
under its surface. |
 |
IO
 |
| WIDTH ACROSS EQUATOR |
3,643 kilometres / 2,264 miles |
| CLASSIFICATION AND LOCATION |
Moon of Jupiter. Fifth
closest moon to Jupiter, first of the Galilean satellites. |
|
Io, Io, it's off the
Jupiter we go - again. The thirteenth
largest object in the Solar System is Io, Jupiter's third largest
moon and the closest of the four large Galilean satellites to orbit
the planet. Io is a violent world where volcanoes erupt on a daily
basis. The insides of Io are constantly churned and heated by the
gravitational tug-of-war between Jupiter on one side and
Europa,
Ganymede and Callisto on the other. The resulting eruptions give the
moon an ever-changing colourful appearance, and the discovery of
active volcanoes there in 1979 revealed that Earth isn't the only
only geologically active place in the Solar System, a discovery that
undoubtedly excited many scientists. |
THE MOON
|
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|
WIDTH ACROSS EQUATOR |
3,475 kilometres / 2,159 miles |
|
CLASSIFICATION AND LOCATION |
Natural satellite. In orbit of Earth |
|
Next up is a very familiar face - Earth's Moon, or Luna if you
want to give it its proper name. Thought to have formed out of the
debris from a collision of a planet-sized object with
Earth in the
early days of the Solar System, the Moon is 400 times smaller than
the Sun but, by some bizarre coincidence, is 400 times closer to
Earth than the Sun. This means that the
Moon and the Sun appear to be the
same size from Earth and that the
Moon can completely cover the
Sun's disc during a total eclipse. The
Moon is the only surface
other than Earth to have been stepped on by human beings. The last
one there stepped off it in 1972, and it doesn't look like anybody
will be back in the near future. |
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EUROPA
 |
| WIDTH ACROSS EQUATOR |
3,122 kilometres / 1,940 miles |
| CLASSIFICATION AND LOCATION |
Moon of Jupiter. Sixth
closest moon to Jupiter, second of the Galilean satellites. |
| It's back to
Jupiter for the final time, and time to acquaint
ourselves with Europa. Unlike most moons,
Europa's surface is smooth. This is
because its surface is ice. It is thought that the ice as much as 30 kilometres
thick (18 miles) and that below it there may be water. As you know,
or you should if you've read this website properly seeing as I keep
harping on about it, water is essential for life. As
Europa is
thought to be covered in it, scientists are especially eager to
investigate it. Who knows what kind of mysterious sea-dwelling
creatures lurk in the depths of Europa's oceans? Not me, that's for
sure. |
TRITON
|
 |
|
WIDTH ACROSS EQUATOR |
2,707 kilometres / 1,680 miles |
|
CLASSIFICATION AND LOCATION |
Moon of Neptune, seventh closest to the planet. |
|
It's over to Neptune now as its largest moon,
Triton, takes
sixteenth spot on our list. Triton is a cold, lonely place (well, I
suppose everywhere other than Earth is lonely), so to pass the time
and amuse itself, Triton orbits backwards and sometimes emits gasses. Nitrogen gas
escapes through geysers in a similar, but less exciting, way to the
volcanoes on Io. What this proves is that even distant moons are
geologically active. |
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ERIS
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| WIDTH ACROSS EQUATOR |
3,000 kilometres / 1,850 miles |
| CLASSIFICATION AND LOCATION |
Dwarf planet/Trans-Neptunian
Object/Kuiper Belt Object/Plutoid. Most distant Dwarf planet in
Solar System. |
| The newest entry in our chart,
Eris' discovery in 2003 gave
scientists headaches and many sleepless nights, resulting in
catastrophe for Pluto. Being large and round,
Eris, by definition,
should have been a planet. But, astronomers around the world didn't
want Eris to be a planet for reasons best explained elsewhere (here
for example!) so they voted to change the definition of a planet. A
new definition - the dwarf planet - was created for worlds just like
Eris, would-be planets that exist in regions shared with other
objects. Eris became one of the first
dwarf planets. But so did
Pluto, losing its status as planet and angering many a scientist and
people from Illinois. |
PLUTO
 |
 |
|
WIDTH ACROSS EQUATOR |
2,390 kilometres / 1,430 miles |
|
CLASSIFICATION AND LOCATION |
Dwarf planet/Trans-Neptunian Object/Kuiper Belt Object/Plutoid.
Usually orbits beyond Neptune. |
|
As if losing its status as a planet wasn't bad enough because of
it, Eris' discovery also resulted in
Pluto dropping a place in this
chart. Pluto was discovered in 1930 by Clyde Tombaugh who was
looking for a large planet beyond Neptune that was affecting
Uranus'
orbit. It later became apparent Uranus'
orbit was not actually being
affected by anything beyond Neptune, so
Pluto's discovery was more
through pure luck than anything else. Pluto's name was suggested by
an English schoolgirl. From its discovery up to 2006,
Pluto was the
ninth planet in the Solar System. Nowadays, it is the Solar System's
second largest dwarf planet. |
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TITANIA
 |
| WIDTH ACROSS EQUATOR |
1,578 kilometres / 982
miles |
| CLASSIFICATION AND LOCATION |
Moon of Uranus, seventeenth
closest moon to the planet |
| Titania is a moon of
Uranus and the largest moon to orbit the
planet. It was discovered by William Herschel, the astronomer who
discovered Uranus and three of its other
moons. Not a lot is known about Titania. It is half ice and half rock and orbits above and below
Uranus due to Uranus travelling around the
Sun on its side. |
RHEA
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 |
|
WIDTH ACROSS EQUATOR |
1,530 kilometres / 949 miles |
|
CLASSIFICATION AND LOCATION |
Moon of Saturn, twentieth closest moon to the planet. |
|
Taking last spot in our list of the Solar System's largest
objects is Rhea, the second largest moon of Saturn. It was
discovered in 1672 by Giovani Domonico Cassini, although didn't get
its name until 1847. Rhea is heavily cratered, and is home to a
crater nicknamed "The Splat." |
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