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Planet Facts
Read some really neat facts about
the planets in our solar system!
Note: The fast facts on
this page are appropriate for grades 1 to 3 while the "more
about" links are appropriate for grades 4+.
I've listed them in order from closest to
furthest from the sun:
- Mercury
- Venus
- Earth
- Mars
- Ceres (dwarf planet found in the asteroid belt)
- Jupiter
- Saturn
- Uranus
- Neptune
- Pluto
(Note: Pluto is considered a dwarf planet now)
- Eris, Makemake, Haumea, Sedna (also
dwarf planets -- found past Pluto)
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| Mercury takes 59 days to make a
rotation but only 88 days to circle the Sun.
That means that there are fewer than 2 days in a year! Many
astronomers believe that Mercury might be the core of what was once a much
larger planet -- it appears to be a huge ball of iron covered by a thin
layer of rock. |
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Venus is the brightest
planet in our sky and can sometimes be seen with the naked eye if you know
where to look. It is the solar system's brightest planet -- yellow
clouds of sulfuric acid reflect the sun's light brightly. |
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Earth has more exposed
water than land. Three
quarters of the Earth is covered by water!
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Mars is the home of
"Olympus Mons", the largest volcano found in the solar system.
It stands about 27 kilometers high with a crater 81 kilometers
wide. |
Between Mars and Jupiter, is a
Dwarf Planet known as Ceres. It was discovered in 1801. It is the
smallest dwarf planet discovered in our universe (so far) and is the only one
found in the asteroid belt.
| Jupiter is the largest planet in
the solar system, but it spins very quickly on its axis.
A day on Jupiter lasts only 9 hours and 55 minutes. Ack, I
get dizzy just thinking about it!
Jupiter is so big that you could fit all
the other planets in the solar system inside it. The red spot of
Jupiter is the biggest, most violent storm in the known universe -- that
spot is at least three times the size of earth!
more
about Jupiter >
(including actual photos)
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Saturn is the second
biggest planet, but it’s also the lightest planet.
If there was a bathtub big enough to hold Saturn, it would float in
the water!
The ring that surrounds
Saturn could be the remnants of a moon that was shattered by Saturn's
gravity.
more about
Saturn >
(including actual photos) |
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Uranus’ axis is at a 97
degree angle, meaning that it orbits lying on its side! Talk about a
lazy planet. |
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Neptune was discovered in
1846 (over 150 years ago). Since
that time it has still yet to make a complete orbit around the sun,
because one Neptune year lasts 165 Earth years! Like
Jupiter, Neptune has a dark spot caused by a storm. Neptune's spot
is smaller than Jupiter's -- it is only about the size of the planet
earth. |
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Pluto’s orbit sometimes
brings it closer to the Sun than Neptune.
It jumped ahead of Neptune on September 5, 1989 and remained there
until February, 1999 when it went back to being the farthest.
Note: Pluto is no
longer considered a planet -- instead, astronomers call it a dwarf planet
or planetoid. Whatever the name, our solar system isn't the neat
model we once thought it was. It takes a bit for grown-ups (like
me!) to adapt to the changes in our understanding (I now understand a bit
better how folks felt when someone started telling them the earth was
round not flat!) |
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In January 2005,
astronomers in the United States discovered a new body orbiting the sun in
our solar system. They named this planetoid, Eris after the Greek
goddess of strife.
Eris takes approximately
550 earth years to orbit the sun. The majority of the time, it is
further from the sun than Pluto, but for a short time, it is closer.
Eris is actually larger
than Pluto (it is the ninth largest object orbitting our sun discovered so
far!) |
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Makemake and Haumea are
dwarf planets just like Pluto, but a little further out in our solar
system. Because their orbits are not perfect circles, they trade
places in terms of which is closer and which is further from the
sun. Both
were discovered in late 2004/early 2005. Haumea
has a squished egg shape -- thought to be the result of a collision from
an asteroid or meteor at some time. |
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In 2004, astronomers in
universities in the United States discovered a new body orbiting the sun
in our solar system. They named this planetoid, Sedna after the
Inuit goddess of the Ocean. This is the furthest orbiting body
identified in our solar system to date.
Sedna is about three
times further from our sun than Pluto. It takes between 10,500 and
12,000 earth years for Sedna to make one orbit around the sun (we haven't
quite figured out exactly how long it takes). |
Definition of a
'Planet': What makes something 'beautiful'?
Is a Picasso painting
beautiful? Or do you prefer a photograph? Or perhaps the first
project ever created by a beloved three year old is where beauty lies for
you.
Definitions are created by
people to describe the universe that surrounds us. But we don't have
a King of Definitions to tell us when we've got it right! Sometimes
we all agree on what something means and sometimes we don't.
There is no
'King of Definitions' in charge of deciding what is a planet and what is
not. These decisions are the result of a lot of thinking and
conversation by a lot of very smart people. And these decisions
change over time as our knowledge grows and changes.
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the most beautiful craft I've ever
seen!
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Where we stand now, there are
8 'planets' in our solar system and a number of planetoids (dwarf
planets). The biggest deciding factor that makes something a planet
is that it orbits on the same plane, that it has significant gravity and
that it is a large enough size.
It will be interesting to see
how our solar system shapes up as astronomers discover more and more
through technologies such as the Hubble Telescope!
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Note: This section last updated in April, 2009. Our
understanding of our solar system is always being updated due to new
technologies and new discoveries!
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