Solar System

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Solar System

Event Information
Latest Appearance 2010
Forum Threads

This event rotates with Reach for the Stars.

Event Overview

This event will address the Sun, planets and their satellites, comets, asteroids, the Oort Cloud, the Kuiper Belt, meteoroids, meteorites, and meteors.

For this event be sure to acquire a glossary containing many astronomical terms, a list of famous astronomers and their accomplishments, a table of planetary facts (mass, volume, year length, etc.), detailed diagrams of the sun and solar features, and astronomy formulas.

Origins of the Solar System


Quick Guide to the Solar System

Planets and Basic Info
Planet Orbit Peroid Rotation Period Date Discovered Distance From Sun Radius Mass
Mercury 87.97 days 58.6 days .39 AU 2439.7 km
Venus 224.7 days 243 days .72 AU 6051.9 km
Earth 365.25 days 1 day 1 AU 6371.0 km
Mars 686.98 days 1.03 days 1.52 AU 3389.5 km
Jupiter 11.86 years 0.41 days 1610 5.2 AU 72,000 km
Saturn 29.46 years .4166667 days 9.54 AU 60,268 km
Uranus 84.01 years .7183333 days March 13, 1781 19.18 AU 25559 km
Neptune 164.9 years .67125 days September 23, 1846 30.06 24764 km

Use this chart to quickly look and compare some basic info for all the planets.

Bodies of the Solar System

(Please note that all of the largest/smallest classifications of the planets are NOT including Pluto! (Which technically isn't really a planet anymore.))

The Sun

Diameter 1,392,000 km
Mass 1.989 1030 kg
Luminosity 3.846 1033 erg/s

The Sun is the largest body in our solar system, and contains 99% of the mass. It is made up of layers, starting from the outside(with Temperatures), Corona(1,000,000 C),Photosphere(6,000 C),Convection Zone(1,000,000 C),Radiative Zone(2,000,000 C),and the Core(15,000,000 C).It produces heat from the fusion of hydrogen atoms. The heat is transferred by the process of convection, through the radiative and the convective zone, where it is radiated out through the photosphere and corona to the planets in the form of rays.This site should contain the solar features that I have not listed here: [1]


The core is the densist part of the sun, with a denistity of 160 g/cm^3. That is ten times that of lead. Although, the temperature is 15 million kelvin, or 27 millon degrees Fahrenheit, which keeps the core in a gaseous state. The core is where fusion takes place. Fusion is the proccess of small molecules combining to form larger ones, releasing energy. The force of gravity is so strong that it breaks down atoms into protons, nuetrons, and electrons. Sometimes protons will combine with nuetrons to form deuterons. If these deuterons combine with one more proton, they form a helium-3 isotope. Two of these combine to make a helium atom. The missing proton (remember that the helium-3 isotope has 1 neutron and 2 protons each) is released in the form of energy.

Raidiative Zone

Surounding the core is the raidiative zone. This area is hot and dense that energy from the core can radiate outwards through this area. Ions of helium and hydrogen emit photons, which then get obsorbed by more hydrogen and helium isotopes. Photons travel slowly this way. It can take 100,000 years for a single photon to exit the radiative zone.

Convection zone

The sun isn't hot enough in this outer layer to raidate throug here, but instead the energy moves through here through convection, or the process of hoter things rising and cooler things falling. The solar plasma here heats up as you get closer to the core, rising, lets out the energy near the top, then falls again.


The outermost part of the sun is called the photosphere. This is where the energy made in the core is finaly released into the sun's atmosphere. This is the visible part of the sun.

Inner Planets


is the smallest planet with a radius of 2439 km and the planet closest to the sun at a distance of 57.9 million kilometers. Its year is 88 earth days long, and its day is 59 earth days long. The Surface gravity of mercury is 1/3 of Earth's, so it cannot hold on to an atmosphere. Therefore its surface is scarred with the craters of meteors that would have broken up if it had an atmosphere. The surface temperatures at day and at night are very different, the day temp is 227 C and the night temp is -173 C. It's most noticeable feature is the largest impact crater on its surface, the Caloris basin.


is the 2nd smallest planet in the solar system with a radius of 6051 km, and the 2nd closest to the sun at a distance of 108.2 million kilometers. It is the only planet whose day is longer than its year. Its day is 243 Earth days, and its year is 225 Earth days. It was often called Earth's sister plane because of its close proximity to Earth, and because of its similar diameter and mass. People even thought it could hold life!, but sadly people discovered that the greenhouse effect on Venus raised the surface temp to the highest in the Solar System.


is the third planet from the Sun, and the fifth largest at a radius of 6378 km. It is the only planet in the universe known to support (supposedly) intelligent life. We use it as a basis for many measurements of planets and other things in the solar system (ex. the AU, the average distance between the Earth and the Sun, 93,000,000 miles or 149,600,000 km). The year is equal to 365.256 Earth days, and its day is 1 earth day (But you already knew that).


the fourth planet from the Sun at a distance of 227,392,000 km, is often called the Red Planet, because the large quantities of iron oxide in its soil. The Romans saw it as blood, so they named it for their god of war, Mars. It is the third smallest planet, with a radius of 3397 km. It has a day length of about 25 hours, and a year equal to 687 Earth days. It has been suggested that Mars may hold intelligent life, but it hasn't been proven.

Outer Planets


is the fifth planet from the sun at a distance of 778.3 million km, and the largest with a radius of 71,492 km. Jupiter holds most of the non-solar mass in the solar system. It gives off more energy than it receives from the sun, so it is believed that Jupiter is a failed star, that it could have formed a star, but wasn't under the right conditions. Contrary to popular belief, Jupiter has three small rings around it, made of tiny particles. Its day is the shortest in the solar system at about 10 hours, and its year is equal to 12 earth years. It has an atmosphere composed of hydrogen and helium. The outer layer is the thin visible cloud bands that we see this is also the zone that contains the circular storm known as the Great Red Spot. This is followed by a thick layer of liquid hydrogen. Beneath that is a nearly same size level of liquid hydrogen that, because of the pressure, behaves like a metal. Then beneath that is an iron-silicate core.


is the sixth planet from the sun, 1.427 billion km away. It is also the second largest at about 60,330 km radius. Its day is only 10 hrs and 40 min., and its year is about 30 Earth years. It is the least dense planet, and if placed in a large enough body of water, it would float. It has the largest and most spectacular ring system in the solar system. They have a diameter of 275,000 km, but they are only a few hundred meters thick. The rings are made up of particles that vary in size, from dust like particles, to the moons Janus and Epimetheus. Saturn, like Jupiter, is made up of only Hydrogen and Helium, and gives off more energy than it receives, but it isn’t as large as Jupiter, so it is not believed to have ever had the potential to be a star.


(pronounced your-uhn-us, not: your-anus) is the 3rd largest planet (25,560 km radius), and the seventh from the sun (2.87 billion km away). It was the first planet discovered after prehistoric times, because it is so far away from Earth. It was discovered by William Herschel. Uranus is known for having its axis of rotation parallel to its plane of orbit. Its 9-ring ring system is also parallel to its plane of orbit. These rings are different from those of Jupiter and Saturn, because they are more like hoops than rings of particles, and they have large gaps between them. Its day is about 18 hours long, and its year is 84 Earth years long. Its outer atmosphere is composed of hydrogen, helium, and methane, which gives it its blue green color. Beneath the outer layer is a layer of high pressure solid water, methane, and ammonia. Then, beneath that layer is a ball of rocky material that is very similar to Earth, but its surface is distorted by the dense inner ocean of water and methane.


the 8th planet from the sun, at a distance of 4.479 billion km, and the 4th largest at a radius of 24,765 km was discovered in 1846 after calculations in Uranus's orbit revealed that its motions were disturbed by a more distant planet. Its day is about 19 hours, and its year is 165 Earth years. The outer third of Neptune is made of hydrogen, helium, water, and methane, which, as on Uranus gives it a blue tint. The inner two thirds are made of molten rock, liquid water, liquid ammonia, and methane. Neptune's most apparent feature is a storm similar to the Great Red Spot, The Great Dark Spot.

Dwarf Planets

The definition of a Dwarf Planet is a planet with enough of a gravitional pull to keep a spherical shape, but not strong enough to "clear the nieghborhood", which means that any object that comes close to the planet, it either "pushes away" or "pulls into an orbit".










When it was still considered a planet, Pluto was the ninth planet from the Sun and the smallest planet. Very little is known about Pluto and its similarly sized moon Charon (pronounced karen). It was discovered in 1930 by Clyde Tombaugh, and is the only planet discovered in the 20th century. It is a part of the Kuiper belt, and is one of many similar Kuiper Belt objects. The only thing we know about Pluto is that it has a highly eccentric orbit, which crosses Neptune’s orbit every 200 years or so, for 20 years. It also has two smaller moons, Nix and Hydra.



Small Solar System Bodies


A small solar system body orbiting the sun composed mainly of rock. They are larger than meteoroids but smaller than planets. Size ranges from 10 meters across to thousands of kilometers. The main difference between asteroids and comets is that comets have a tail of gases while asteroids do not. Comets can become asteroids if they burn off the ice on their surfaces. In fact, asteroids with eccentric orbits are most likely former comets. Most asteroids in the solar system orbit within the Asteroid Belt between Mars and Jupiter.


A "sand- to boulder-size" piece of space debris. The official definition from the IAU is "a solid object moving in interplanetary space, of a size considerably smaller than an asteroid and considerably larger than an atom". Traditionally, anything smaller than 10 meters across is considered a meteoroid, while anything larger than 10 meters is an asteroid. Once a meteoroid enters the atmosphere of Earth or another planet, it is considered a meteor. If it reaches the ground and stays (more or less) intact, it's called a meteorite.


A small solar system body that has a coma (the dust particles gathered around the comet's nucleus that give it an "atmosphere") and/or a tail. The nucleus itself is made up of water ice, dust, frozen gases and small rocky particles. The nuclei range from 100 meters across to more than 40 kilometers. As the comet approaches the sun, solar radiation cause the gases inside to vaporize and carry the dust with them. The gases also become excited by sunlight and emit electromagnetic radiation. Comets leave a trail of solid particles behind them, and if a comet crosses earth's path, there will most likely be meteor showers when earth passes through the debris field. For example, Halley's Comet causes the Orionid Showers and the Swift-Tuttle Comet causes the Perseid showers.

Short-Period Comets

Comets with an orbital period of less than 200 years. Their orbits are in the same direction as the planets, close to the ecliptic, and their aphelion is generally in the area of the outer planets. They are divided into the Jupiter family (orbital period less than 20 years) and the Halley family (orbital periods between 20 and 200 years).

Long-Period Comets

Comets with orbital periods of more than 200 years, sometimes even thousands or millions of years. Their orbits are very eccentric, often don't lie near the ecliptic, and their aphelion is far beyond the outer planets. However, all long-period comets are still gravitationally bound to the sun; comets that have been ejected from the solar system by the gravity of the outer planets are no longer considered to have an orbital period.

Single-Apparition Comets

Comets that have a parabolic or hyperbolic trajectory, i.e. their trajectories only let them enter the solar system once (hence the name). Other than that, they are very similar to long-period comets.

Other Features of the Solar System

Oort Cloud


Oortcloud.jpgCopyright Calvin J. Hamilton

Kuiper Belt

The Kuiper belt is similar to the Asteroid belt. It lies beyond Neptune, about 30-50 AU from the Sun. It is believed that these are the remains of when the Solar System was first created. When the solar system was created, most space debris was condensed to form planets. The debris that did not form planets slowly drifted outwards to form the Kuiper Belt. No spacecraft has ever reached the Kuiper Belt, but the New Horizins spacecraft should drift past it sometime in 2015.

Moons of the Solar System

Mercury: No moons

Venus: No moons

Earth's Moons
Moon prehistory prehistory 384,400 3476 27.322
Mars' Moons
Deimos 1877 A. Hall 23,460 8 1.263
Phobos 1877 A. Hall 9,270 .319
Jupiter's Moons
Callisto 1610 Galileo 188300 4800 16.689
Europa 1610 Galileo 670900 3126 3.551
Ganymede 1610 Galileo 1070000 5276 7.155
Io 1610 Galileo 421600 3629 1.769

There are actually 63 moons, but only the most famous ones were listed here.

Saturn's Moons
Atlas 1980 R. Terrile 137640 37 0.602
Tethys 1684 G. Cassini 294660 1060 1.888
Titan 1655 C. Huygens 1221850 5150 15.945

There are 60 moons of Saturn, but I only listed the 3 most famous here.

Uranus- 27 moons

Neptune- 13 moons

Pluto's Moons
Charon 1978 J. Christy 19571 1207 6.387
Nix 2005 H.A. Weaver 48675 44130 42.856
Hydra 2005 H.A. Weaver 64780 44130 38.206

Newton's Laws of Motion and Gravitational Attraction

Laws of motion


2. F=ma. Force equals mass times acceleration.


Law of Gravitational Attraction



G is the gravitational constant,

m1 is the mass of the first point mass,

m2 is the mass of the second point mass, and

r is the distance between the two point masses.

Kepler's Laws of Planetary Motion

Quick Overview


A little more in-depth

Thanks to all the pictures I used in this section! They have a bunch of great info, and I have included a link at the bottom of this page. I would go check it out if I were you!

Law 1


To understand this law, you must first understand ellipses. You can think of an ellipse as a flatten circle, with two axises. There is the major axis, which is the longer one, and the minor axis, which is the shorter one. There are always two focuses, which are on the major axis. There is also a semimajor axis, which is half the major axis, and a semiminor axis, or half the minor axis. The sum of the distance to both of the foci is constant.



Law 2

A line joining a planet and the sun sweeps out equal areas during equal intervals of time. This one is harder to envision. So we've established that the orbit is ellipticle, right? Two lines extending out of the sun will always have the same area, and the planet we are talking about will always travel this distance in equal time. Look at this picture:



Law 3

The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit. Ok, what does this mean? I had to do a little research, too. This is purely math. Sorry, I don't know what that little A is, or why its there.

So what this means is that these two fractions are equal. Remeber in the first law, we defined the major and minor axises? The semimajor axis is half of the major axis. (In an older version, I said the semimajor axis is the same as the minor axis which is not right. Please pay attention to this correction, and I apologize for any confuion.) So that shows that the minor axis defines the orbital period! You can use this law to find either the semimajor axis, which can then be used to find the major axis, or the orbital period. Since , we can use the formula to find the orbital period, or to find the semimajor axis.

Escape Velocity

Escape Velocity is the velocity something must reach in order to escape the gravitational pull of a planet. You can calculate the escape velocity using this formula: Where Ev is the escape velocity, M is the mass (in km) of the planet, G is the gravitational constant (equal to ), and R is equal to the radius of your planet in meters. This is a strange form of measurement for a planet, so watch out. It can change your answer dramatically.

Here is a simple, easy to use Escape Velocity calculator that I made with Microsoft Excell. To use it, you fill in each box in a row with the mass and radius of your planet, respectively. You usually use meters for the radius, but this calculator converts it for you, so fill in the radius in killometers. The first to boxes are used for the mass, so that a*10^b = mass, you would fill in "a" in the first box and "b" in the second box. Just look at the examples to figure out how to use it. Enjoy! Media:Escape_Velocity_Calculator.xls

Famous Astronomers

Tycho Brahe

Tycho Brah(1546-1601) Tycho Brahe was a Danish astronomers that was famous for creating precise measurements of the planets, and also more than 700 stars. He discovered a supernova in 1572 near Cassiopeia. The king of Denmark was so impressed with this discovery that he funded a large observatory on the island of Ven.

Galileo Galilei

Galileo Galilei (1564-1642)



Aristotle's Universe


Johannes Kepler


Clyde Thombaugh


Nicholas Copernicus

Nicholas Copernicus (1473 -1543) Nicholas Copernicus was a Polish astronomer who was the first to develop the Copernicus theory,stating that the sun lie near the center of the Solar System, and the Earth revolve around it, not the other way around. This theory was not proven until Galileo, and not widely excepted for many more years. Later in life he went on to lecture in Rome about astronomy.

Edmond Halley

Edmond Halley (1656-1742) Edmond Halley was a British astronomer who was the first to calculate a comet's orbit. He went to the University of Oxford where he studied the theories of Sir Issac Newton. He published a book in 1705 called Astronomiae Cometicae Synopsis (Synopsis on Cometary Astronomy). Hi theories were validated when a comet appeared in 1758, just as he predicted. The comet was named after him for his remarkable accuracy, and is now known as Halley's comet.

Helpful Tips



the 9 planets

the solar system

views of the solar system

soinc's solar system page

Information on famous astronomers

Kepler's Laws of Planetary Motion