Our Solar System
First... Some Numbers... BIG Numbers
Due to the sheer scale of astronomical distances, Astronomers use different measurements to describe these distances based on distances we can relate with.
a.u. (Astronomical Unit): This is the average distance from the Earth to the Sun. (Roughly 150 million km.) We call this 1 a.u.
With the theory of the Oort cloud (see below), scientists now place the size of our solar system at approximately 100,000 a.u. in diameter, and reaches almost a quarter of the way to the next nearest star. While reading this, bear in mind that Pluto (our farthest known planet) is only less that 40 a.u. away!
So, If the next closest star is 4 light-years away, with the Oort cloud is reaching a quarter of the way to the nearest star, this would make our solar system approximately 2 light years across.
How big is a light-year? Well, this is measured more in time than distance. Or rather, "How far light travels in 1 year". For that, I give you this. Light travels at 186,282 miles per SECOND. I'll provide the equation, but (as the saying goes) you do the math!
In 1 year, light would travel 5.87 x 1012 miles! (1 light-year is 63,240 a.u.)
☉ Sol (The Sun)
Size: 1,392,000 km. dia. (109 Earth dia.)
Distance from Earth: 149,597,870 km. (1 a.u.)
Rotation: 25 Earth days.
This is a large nuclear furnace equivalent to all the worlds' supply of nuclear weapons going off every second. The light we see from the sun takes 8 minutes to reach us traveling at 186 thousand miles per second. Our sun is a middle-aged star at only 4.6 billion years old.
☿ Mercury
Size: 4,878 km. dia. (0.382 Earth dia.)
Distance from Sun: 57.91 million km. (0.3871 a.u.)
Rotation: 58.65 Earth days.
Orbit: 87.969 Earth days.
This is the closest planet to the sun. Its quick orbit as seen from the Earth travels so swiftly through the sky, that it prompted the ancients to name it for the Greek god Mercury, the messenger of the gods.
♀ Venus
Size: 12,102 km. dia. (0.949 Earth dia.)
Distance from Sun: 108.2 million km. (0.7233 a.u.)
Rotation: 243.01 Earth days.
Orbit: 224.701 Earth days.
Venus is the brightest of all the planets due to its thick cloud cover reflecting the sunlight. It was named after the goddess of love in Roman mythology. Venus is one of the three planets that rotate backwards. This planet was once thought to be 2 planets named "Phosphorous" (morning star) and "Hesperus" (Evening star) due to it being seen either in the morning or evening depending on where in its orbit it was at the time.
♁ Earth
Size: 12,756 km. dia. (1.0 Earth dia.)
Distance from Sun: 149,597,870 km. (1 a.u.)
Rotation: 24 Earth hours. (1 Earth day)
Orbit: 365.2422 Earth days.
You are here. Earth was thought to be the center of the universe in ancient times. Unlike all the other planets, whose names are based upon Greek and Roman mythology, the name Earth comes from the Old-English "Orethe" roughly translating to mean land or rock, although the Earth's surface is made up of over 70% water, which allowed Earth to begin life. The Earth has only 1 satellite, and we call it the Moon. The word "Moon" comes from the Anglo-Saxon word "Moneth" meaning "a period of one month", which is about the time between the full moons.
♂ Mars
Size: 6,786 km. dia. (0.532 Earth dia.)
Distance from Sun: 227.94 million km. (1.5237 a.u.)
Rotation: 24.6229 Earth hours.
Orbit: 686.98 Earth days.
This planet was named after the Greek god of war because its reddish color reminded the ancients of blood. It is also the only planet to have a star named for it, "Antares", which means, "rival of Mars" also having a reddish color. During its orbit, Mars travels close to Antares in the sky, as if threatening war with its rival. Mars is also thought to once contain water on its surface, which leads many to believe that life could have been there as well. Mars has 2 satellites, "Phobos" (Fear) and "Deimos" (Panic), named after the 2 dogs of the god Mars.
The Asteroid Belt
Size: Varies
Distance from Sun: 315-495 million km. (2.1-3.3 a.u.)
This region between Mars and Jupiter was possibly a "proto-planet" at one time long ago. With all the debris collected and reassembled, the planet would be smaller than our moon. Destroyed long ago, possibly due to the immense gravity of Jupiter, it is now the home to currently over 4000 named and numbered asteroids. The asteroids here range from softball-sized chunks, to several hundred miles in across.
♃ Jupiter
Size: 142,984 km. dia. (11.23 Earth dia.)
Distance from Sun: 778.33 million km. (5.2028 a.u.)
Rotation: 9.841 Earth hours.
Orbit: 11.8623 Earth years.
Jupiter is the "king" of the gods, named so because it is the largest of all the other planets. Not only is it the largest planet, but it also has the fastest rotation of all of them, causing it to "bulge" in the center and making it look more oval than round. Jupiter does not have a "surface" as yet known, but instead is a planet made up of only various gasses. On the cloud surface, there is a storm known as the "Great Red Spot" that is larger than the Earth and has been raging for more than 300 years. Jupiter currently has 61 satellites, and more are being discovered regularly. The 4 largest of these can be seen from earth with simple binoculars.
♄ Saturn
Size: 120,536 km. dia. (9.41 Earth dia.)
Distance from Sun: 1,426.98 million km. (9.5388 a.u.)
Rotation: 10.233 Earth hours.
Orbit: 29.458 Earth years.
Saturn was named after the god of time due to its slow, near 30 year orbit. Saturn is possibly the prettiest of all the planets because of its bright rings. Although Jupiter, Uranus, and Neptune also have rings, they are not visible from Earth. The rings were possibly other satellites at one time that were destroyed by Saturn's gravity. Slowly over time, these rings will disappear as they are pulled into the planet. Like Jupiter, Saturn is also a gas planet. Its density is so low, that if Saturn was placed in a body of water large enough, it would float. Saturn currently has 22 satellites, and has a long way to go to stay in the race with Jupiter and its growing number of satellites.
♅ Uranus
Size: 51,118 km. dia. (3.98 Earth dia.)
Distance from Sun: 2,870.99 million km. (19.1914 a.u.)
Rotation: 17.9 Earth hours.
Orbit: 84.01 Earth years.
The name Uranus comes from the Greek mythology "Ouranos" the "Overhanging Heavens". Another of the gas planets, Uranus is one of the three planets that rotate backwards. Uranus also differs in the fact that its axis is tilted following the plane of its orbit, like a bead on a thread. Uranus also has a faint ring that is not visible from Earth, which was discovered when Voyager took pictures as it passed. Uranus currently has 26 satellites, of which only 5 were known before Voyager 2 flew by in 1986.
♆ Neptune
Size: 49,528 km. dia. (3.81 Earth dia.)
Distance from Sun: 4,497.07 million km. (30.0611 a.u.)
Rotation: 19.2 Earth hours.
Orbit: 164.79 Earth years.
Since its discovery nearly doubled the size of the known Solar System, being so far away, Neptune was named after the Roman god of the deep-sea. This is the last of the gas planets, and because of the composition of the gasses, it is thought to possibly have a solid diamond core at its center about half the size of Earth. Neptune currently has 13 known satellites.
♇ Pluto
Size: 2,300 km. dia. (0.18 Earth dia.)
Distance from Sun: 5,913.52 million km. (39.5294 a.u.)
Rotation: 6.3872 Earth days.
Orbit: 248.54 Earth years.
Pluto got its name from the Roman god of the underworld, since it is the furthest planet from the sun. Pluto is the last of the three planets to rotate backwards. Pluto has an elliptical orbit, which brings it in closer than Neptune at times. Its orbit is on an incline from the rest of the planets orbits. And it is also the smallest of all the planets (1000 km. smaller than the Earth's Moon). With all this being so different than the other planets, many scientists have debated the status of Pluto being a planet or not. Pluto has one satellite, Charon, named after the boatman who ferried the dead to the underworld across the river Styx.
In August of 2006, the IAU had their annual convention and an 11th hour vote was brought to the table. This vote was to define what a planet was. The result of this vote booted Pluto out of the planet list for our solar system due to the new "RULES" of a planet not being met. Ironically, Neptune should also be booted, as it does not meet the new rule either.
Regardless of the IAU decision, I still choose to keep Pluto listed in as a planet.
The Kuiper Belt
Size: Varies
Distance from Sun: 6,000 million km. (40 a.u.)
Well beyond Pluto (orbit marked in image) is the Kuiper belt. This is a disc-shaped region comprised of the "left-overs" from the solar system's creation. Mostly chunks of rock and ice, this is considered to be the birthplace of many of the short-period Comets known today. Objects in this region are influenced by the gravity of the larger planets, and occasionally an object may be "nudged" out of orbit and sent on a path towards the inner solar system.
Xena (2003-UB313)
Size: 2700 km. dia. (0.21 Earth dia.) (Bigger than Pluto!)
Distance from Sun: 5,700 million - 14,550 million km. (38 - 97 a.u.)
Rotation: Not known yet.
Orbit: 560 Earth years.
Not the official name, but until the IAU (International Astronomical Union) decides upon the permenent name for 2003-UB313, astronomers are calling this planet Xena (from the T.V. show). And of course, following suit, they named the small moon orbiting UB313 Gabrielle, which is of Xena's side-kick from the show. The moon is 250k. in diameter, and as yet has an unknown orbital period. More information will be added as it becomes available.
☄ Comets
Size: Varies.
Distance from Sun: Varies. Elongated Orbit.
Orbit: Varies.
I have comets this far down on my list, since the region of the Kuiper belt and beyond is where comets are born and begin their long journey around the sun. Their orbits are very elongated and brush closely to some of the planets along their way. When they get close to the Sun, the heat from the Sun causes the comet's tail to form. The Sun's gravity whips the comets around, and on a course back out to the outer reaches of the solar system. Many comets have been discovered and plotted. Some with early periods that return regularly every several years, and others with far longer orbital periods like Halley's comet, which returns every 84 years.
Quaoar (Un-Official)
Size: 1,300 km. dia. (Roughly half the diameter of Pluto)
Distance from Sun: Roughly 6,000,000,000 km. (6 Billion km.) (43 a.u.)
Rotation: Not yet known.
Orbit: 288 Earth Years.
Discovered while looking for that imfamous "Planet-X" on June 4, 2002, Quaoar (pronounced KWAH-o-wahr) has not been classified as a planet. Scientists are still in debate as to what is actually required as a planet. Quaoar (originally known as 2002 LM60) is now the official name as voted upon by the IAU (International Astronomical Union).
The name "Quaoar" comes from the creation mythology of the Tongva people (sometimes called the San Gabrielino Native Americans), who inhabited the Los Angeles area before the arrival of the Spanish and other European people.
Sedna (Un-Official)
Size: 1,800 km. dia. (Slightly smaller than Pluto)
Distance from Sun: Roughly 11,500,000,000 km. (11.5 Billion km.) (~76 a.u. to ~942 a.u)
Rotation: Not yet known.
Orbit: 10,500 Earth Years.
The distance listed above is when Sedna is at its closest. Sedna's orbit is highly elongated, and reaches an astonishing distance of 942 a.u. For a fantastic "Zoom-Out" video from the sun to Sedna, and the Oort cloud, check out The Nasa Newsroom.
Discovered on November 14, 2003, Sedna is now the farthest discovered object in the solar system. It was originally thought to have a small moon of its own, although the Hubble images acquired did not show enough detail to determine the presence of one, and further tests that were conducted confirmed that there was in fact no moon. As with Quaoar, scientists were searching for that elusive "Planet-X" when they stumbled upon this VERY distant object. Sedna (Originally known as 2003 VB12), is now the official name as voted upon by the IAU.
As for the name, this object is the coldest most distant place known in the solar system, so it is only appropriate to name it in honor of Sedna, the Inuit goddess of the sea, who is thought to live at the bottom of the frigid Arctic Ocean. Scientists are suggesting to the IAU that any future objects found near or in the inner Oort cloud be named after entities in arctic mythologies.
The Oort Cloud
Size: Varies
Distance from Sun: Unknown (5000 - 50,000+ a.u.)
In 1950, an astrophysicist named Jan Oort noted from her observations that;
1 - no comet has been observed with an orbit that indicates that it came from interstellar space;
2 - there is a strong tendency for aphelia of long period comet orbits to lie at a distance of about 50,000 AU, and;
3 - there is no preferential direction from which comets come.
These observations led to the belief that well beyond the kuiper belt, there may be another region where many more comets reside. As many as a Trillion "Proto-Comets" are possible. Unlike how the Kuiper belt is disc-shaped, the Oort cloud is better described as a very thick "Bubble" surrounding the entire solar system, about half-way from the Sun to the next nearest star.