Our Solar System
Sol, our Star and Sun:
Our Sun is the most prominent object in our solar system. This is an obvious fact, our
Sun contains about 98% of all the matter in the solar system and its interior is so large it would
hold 1.3 million planets the size of Earth! The Sun's surface, called the photosphere, has a
cool temperature of about 6,000o C (approximately 11,000o F ). Interior temperatures are
much higher, this is where the real solar energy is created. The interior temperature is between
15,000,000 and 27,000,000o and the pressure at the interior is 340 billion times Earth atmospheric
pressure.
Our Sun has been undergoing nuclear fusion for about 5 billion years, and has enough
hydrogen fuel left to continue for about that much longer. See
http://www.solarviews.com/eng/sun.htm for more information.
Mercury:
Mercury is a hard rock planet and the second smallest planet in the solar system. It is also
the closest planet to the sun; as a result, it's surface is very warm with a mean temperature of
452o K. There is very little atmosphere on Mercury, only trace amounts of hydrogen and helium.
The diameter of this small planet is 4,900 km (compared to Earth, nearly 12,800 km).
This makes Earth's diameter 2.6 times larger than Mercury's diameter; which means Earth has nearly
18 times the volume of Mercury (2.63 ). Mercury is only 58 million km from the Sun, each day
(one rotation) on Mercury is almost 59 Earth days. A Mercury year is only 88 Earth days. One
of the keys to life that we humans look for is evidence of water. No water could exist on Mercury.
Mercury's surface is scarred by many impact craters from meteorite and asteroid collisions.
Here's an excellent and very comprehensive website: http://www.solarviews.com/eng/mercury.htm .
There are a couple of short movies here that are super.
Venus:
Venus is the second planet from the Sun, and is nearly the same size as the Earth. Venus is
12,100 km in diameter. Venus is commonly known as the evening star, but it is not a star, just a
small planet near the Sun with a highly reflective and dense cloud cover. The clouds are not made
of water vapor as they are here on Earth, but mostly carbon dioxide and sulfuric acid droplets.
There is no water on Venus! Venus was named for the Roman goddess of love and beauty, but we
see that Venus is not so beautiful! The atmospheric pressure is 92 times that of Earth's, so it is
capable of crushing anything we commonly see on the surface of our Earth. It is also very hot
there, surface temperatures reach a sizzling 480o C or 900o F. The heavy crushing atmosphere of
carbon dioxide and sulfuric acid traps the solar heat and creates what is known as a greenhouse
effect. We've never seen the surface of Venus with optical telescopes because of these dense clouds.
In recent years new developments in radar mapping technology have allowed us to find out what
the surface of Venus looks like. Venus has had many collisions with meteors and asteroids; however,
there are few small craters most small meteorites either burn up on entry or break up into tiny pieces
due to the thick, heavy atmosphere. Volcanoes are numerous as are huge lava flows. There are
thousands of volcanoes here, some being very, very large.
Earth (Home):
Earth is called the blue planet, WATER! While we have found water in some form on Mars
and in small amounts on other planets (ice or vapor), Earth is the only planet with liquid water.
We have water in large seas, lakes, rivers, snow/ice, and clouds of water vapor. Without water,
there would be no life as we know it. Earth is the third planet from the Sun, it is a rocky planet
with brown and green land masses, clouds, and blue of oceans. To us, Earth seems very large,
but Earth is relatively small, it is the median sized planet of the solar system; there are four larger
and 4 smaller than Earth. Earth has a diameter of nearly 12,800 km. which is only 700 km larger
than the diameter of Venus. Our atmosphere is very different also; it is nearly 78% nitrogen,
21% oxygen and slightly more than 1% of all the other gases ( carbon monoxide, carbon dioxide,
helium, hydrogen, argon, and others). This thin atmosphere does three major things: a) it shields
the surface from much of the harmful radiation released by our sun , b) creates enough friction/heat
to destroy most meteors that enter our atmosphere, and c) it gives us oxygen to breathe.
The Earth is 93,000,000 miles or 150,000,000 km from the Sun, this measure is called an
Astronomical Unit ( AU ) and is used as a measure of distance in the solar system. Earth is 1 AU
from the Sun, Mercury is 0.387 AU's from the Sun, and Venus is 0.723 AU's from the Sun.
Mars ( The Red Planet):
Mars is the fourth planet from the Sun and is named for the Roman god of war and many
call it the Red Planet. we have seen by telescope and by pictures sent back by satellite and rovers,
much of the planet surface is red rock or sand. This past summer and fall (fall and summer of 2003)
Mars was the closest it's been to Earth in over 6,000 years!
It was the most likely planet in our solar system to harbor life of some kind. Water is a key to
life as we know it, and one of the Mars rovers just found evidence of water. The Martian atmosphere
is very different from Earth. It is composed of 95% carbon dioxide, 2.7% nitrogen, and only
0.13% oxygen, plus some other minor gases. Mars is also quite small, it's diameter is only
6,800 km, about half of Earth's. Mars is also much further from the Sun, 128,000,000 km or about
1.5 AU and takes about 687 Earth days to revolve around the sun. The temperature range on Mars
is a little forbidding, as high as 20o and as low as - 140o C. There's not much atmosphere to
moderate these temperature extremes. Evidence does seem to indicate that Mars was once warmer
and that liquid water may have flowed on the surface. That in turn would indicate more atmosphere.
What happened to it? Mars has two small irregularly shaped moons, Phobos and Deimos.
More pictures of Mars Return to Home Page
Jupiter - The Largest Gas Giant!
Jupiter, King of the Gods, is the fifth planet from the Sun and has a massive diameter that is
142,800 km. If Jupiter hollow, we could put over 1000 Earths inside it! Jupiter has 61 known
satellites, the largest four were spotted by Galileo in 1610. Several are very small with a radius
under 2 km. Jupiter also has 4 rings, however they are not visible from Earth. The rings were
discovered by Voyager 1 in a 1979 flyby. Jupiter's atmosphere is very deep and in fact may be
the entire planet; it resembles the Sun in many ways. At great depths, the pressure of the
hydrogen-helium atmosphere is so great that the electrons leave the hydrogen protons and metallic
hydrogen is formed. At 5.2 AU's from the Sun, Jupiter receives little light or warmth from the Sun.
However, Jupiter releases more energy than it receives. This is caused by Jupiter immense
size and the great pressure of its crushing atmosphere. Jupiter bulges at its equator; this is caused
by its fast rotation on its axis; a day on Jupiter is only about 6.5 hours on Earth. However, Jupiter
orbits the Sun in 4332 days.
For a larger view, click Io and a vocanic plume.
on the image above.
Saturn-the Ringed Planet: 
Saturn is the 6th planet from the Sun and the second largest planet with an equatorial diameter of
119,300 km (about 74,000 miles. Saturn rotates at a very high speed, its day is about 10.5 hours long
and is therefore distorted into more of an ellipse. As a result of its size and high rotation speed, Saturn
has very high winds that can reach velocities of 500 meters/sec;
that's 1,100 miles/hour!
Saturn is composed of 97% hydrogen and 3% helium, both lighter than air here on Earth.
The density of Saturn is 0.69 g/cm3 which means Saturn would float in water! Saturn is about
9.5 AU's from the Sun, and it orbits the Sun in about 29.5 years. There are 18 officially recognized
moons, the largest of these is Titan. Titan is the only satellite large enough to have an atmosphere;
all of Saturn's satellites have a density that is < 2gm/cm3 . This means that the satellites are probably
composed of 30-40% rock and the rest water/ice. Most of the satellites have a synchronous rotation.
Which means they around the planet much as our moon rotates around Earth with one side always
facing the planet. For more information about Saturn, see: http://www.solarviews.com/eng/saturn.htm or http://www.nineplanets.org/saturn.html .
Uranus: an Ice/Gas Giant
Uranus is the seventh planet from the Sun and it's the third largest in the Solar System.
Uranus and its two major moons (it has at least 22) were discovered by William Herschel in
1781. It's mean distance from the Sun is 2.87 billion kilometers or 1.78 billion miles. This
huge distance from the warmth of the Sun is the reason for the nickname ice planet, mean
atmospheric temperature is -193o C. 
The atmosphere is 83% hydrogen, 15% helium and
2% methane. There are trace amounts of acetylene and
other hydrocarbons in the atmosphere. Uranus is blue-green
in color, the methane in its upper atmosphere absorbs red
light from the sun, giving off blue which is the opposite of
red on color wheel. Uranus is quite unusual because it is
tilted on its side and its thin, virtually transparent, rings are almost perpendicular to the orbit
of Earth. These were discovered by Voyager in 1977. The rings are different than the rings found
on
Jupiter or Saturn; The outermost ring is composed of ice
boulders several feet across. A thin distribution of fine dust is
spread throughout the ring system. Since Uranus has a radius
4 times that of Earth, you could place approximately 64 Earths
inside Uranus ( 43 ). Return to Home Page
Neptune, A Second Ice/Gas Planet
Neptune is the eighth planet
from the Sun and
the last of the gas giants. Neptune has an equatorial radius of 24,746 Km which makes it
slightly smaller than Uranus, but its radius is still 3.87 times that of Earth. This means that
almost 58 Earths could fit inside Neptune. It takes Neptune 165 of our years to circle the
Sun! Neptune has eight known moons, six of these were found by Voyager. Neptune was
discovered by Johann Gottfried Galle and Louis d'Arrest by mathematical predictions of
Urbain Jean Joseph Le Verrier.
Neptune has a strange make-up: the inner two-thirds is composed of a mixture of molten
rock, water, liquid ammonia, and methane. The outer third is made f heated gases composed
hydrogen, helium, water and methane. Like Uranus, it's the methane that again absorbs red light
giving Neptune a bluish color.
Neptune has a dynamic atmosphere that changes with light clouds circling the planet about
every 16 hours and dark spots similar to the Great Red Spot of Jupiter. The winds near these
dark spots can blow up to 2,000 km per hour (1,200 mph ). Neptune also has rings; there are
four of them and they are very narrow and faint and made of dust.
Pluto: The Ninth Planet
Pluto is the last of the accepted planets, it has one known satellite, Charon.
Not much is known about Pluto or its moon. Pluto was discovered in 1930 and
it remains the only planet that has not been visited by an explorer spacecraft,
however, one is on the way and due to arrive sometime between 2006 and 2008.
Pluto is small, its equatorial radius is only 1,137 km which makes it only 17%,
or one-sixth the size of Earth. If the Earth were hollow you could put over
200 Plutos inside the Earth. Pluto averages more than 6 billion kilometers
from the Sun or 31 au's. An "au" is an astronomical unit which is the distance
from the Earth to the Sun.
Since Pluto is so far from the Sun, it does not get much light or heat. Its
average temperature is -236 C ( -273o C is 0o Kelvin ). Pluto's orbit is very
ellipical, Perihelion - 29 au's, Aphelion - 49 au's.
