Solar System

The Solar System

The Solar System. Our solar system consists of an average star we call the Sun, the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. It includes: the satellites of the planets; numerous comets, asteroids, and meteoroids; and the interplanetary medium.

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These are the Celestial bodies in the Solar System

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The Sun

The Moon

Asteroid Belt

Kuiper Belt

Oort Cloud

Solar Eclipses

Comets

Asteroids

Meteorites

Meteor Showers

The Sun

The Sun (or Sol), is the star at the centre of our solar system and is responsible for the Earth’s climate and weather.
The Sun is an almost perfect sphere with a difference of just 10km in diameter between the poles and the equator.
The average radius of the Sun is 695,508 km (109.2 x that of the Earth) of which 20–25% is the core.

Star Profile

Age	Type	Diameter	Equatorial Circumference	Mass	Surface Temperature
4.6 Billion Years	Yellow Dwarf (G2V)	1,392,684 km	4,370,005.6 km	1.99 × 10^30 kg (333,060 Earths)	5,500 °C

QUICK SUN FACTS

At its centre the Sun reaches temperatures of 15 million °C.
The Sun is all the colours mixed together, this appears white to our eyes.
The Sun is mostly composed of hydrogen (70%) and Helium (28%).
The Sun is a main-sequence G2V star (or Yellow Dwarf).
The Sun is 4.6 billion years old.
The Sun is 109 times wider than the Earth and 330,000 times as massive.

The Moon

The Moon (or Luna) is the Earth’s only natural satellite and was formed 4.6 billion years ago around some 30–50 million years after the formation of the solar system.
The Moon is in synchronous rotation with Earth meaning the same side is always facing the Earth.
The first unmanned mission to the Moon was in 1959 by the Soviet Lunar Program with the first manned landing being Apollo 11 in 1969.

Moon Profile

Orbit Distance	Orbit Period	Diameter	Orbits	Mass	Surface Temperature
384,400 km	27.3 days	3,475 km	The Earth	7.35 × 10^22 kg (0.01 Earths)	-233 to 123 °C

QUICK MOON FACTS

The dark side of the moon is a myth.
The rise and fall of the tides on Earth is caused by the Moon.
The Moon is drifting away from the Earth.
A person would weigh much less on the Moon.
The Moon has only been walked on by 12 people; all American males.
The Moon has no atmosphere.
The Moon has quakes.
The first spacecraft to reach the Moon was Luna 1 in 1959.
The Moon is the fifth largest natural satellite in the Solar System.
The Moon will be visited by man in the near future.
During the 1950’s the USA considered detonating a nuclear bomb on the Moon.

Asteroid Belt

The vast majority of asteroids in the solar system are found in a region of the solar system out beyond Mars. They form the Asteroid Belt.
Others orbit in near-Earth space and a few migrate or are thrown out to the outer solar system by gravitational interactions.
The four largest asteroids in the belt are Ceres, Vesta, Pallas, and Hygiea.
They contain half the mass of the entire belt.
The rest of the mass is contained in countless smaller bodies.
There was a theory once that if you combined all the asteroids they would make up the missing “Fifth” rocky planet.
Planetary scientists estimate that if you could put all that material together that exists there today, it would make a tiny world smaller than Earth’s moon.

QUICK ASTEROID BELT FACTS

Asteroid Belt objects are made of rock and stone.
Some are solid objects, while others are orbiting “rubble piles”.
The Asteroid Belt contains billions and billions of asteroids.
Some asteroids in the Belt are quite large, but most range in size down to pebbles.
The asteroid 1/Ceres is also designated as a dwarf planet, the largest one in the inner solar system.
We know of at least 7,000 asteroids.
The Asteroid Belt may contain many objects, but they are spread out over a huge area of space.
This has allowed spacecraft to move through this region without hitting anything.
Asteroids get their names from suggestions by their discoverers and are also given a number.
The formation of Jupiter disrupted the formation of any worlds in the Asteroid Belt region by scattering asteroids away.
This caused them to collide and break into smaller pieces.
Gravitational influences can move asteroids out of the Belt.
The Asteroid Belt is often referred to as the “Main Belt” to distinguish it from other groups of asteroids such as the Lagrangians and Centaurs.
Kuiper Belt

The Kuiper Belt (sometimes referred to as the Kuiper-Edgeworth Belt) is an area of the outer solar system that is estimated to stretch across 20 astronomical units (AU) of space.
It contains small solar system bodies made mostly of ices.
The ices are frozen volatiles (gases) such as methane, ammonia, nitrogen and water.
It also is home to the known dwarf planets Pluto, Haumea and Makemake.
The Kuiper-Edgeworth Belt is named for the astronomers Gerard Kuiper, who theorized about a disk of material in the outer reaches of the solar system, and Kenneth Edgeworth, who had the idea that the outer solar system contained a number of small bodies, perhaps left over from the formation of the Sun and planets.
This region of space is cold enough to support the existence of volatiles more easily than areas closer to the Sun.

QUICK KUIPER BELT FACTS

The Kuiper Belt could contain hundreds of thousands of icy bodies that range in size from small chunks of ice to worldlets larger than 100 kilometres across.
Astronomers have tracked most short-period comets from their origins in the Kuiper Belt.
These are comets with orbital periods of 200 years or less.
There could be more than a trillion comet nuclei in the main body of the Kuiper Belt.
The largest Kuiper Belt Objects are Pluto, Quaoar, Makemake, Haumea, Ixion, and Varuna.
These are often also referred to as Trans-Neptunian Objects (TNOs).
The first mission to the Kuiper Belt and beyond will fly by Pluto in July 2015.
It’s called New Horizons and will survey Pluto, Charon and the other moons before heading out to study other Kuiper Belt Objects in the future.
Astronomers have found structures similar to our Kuiper Belt around at least nine other stars.
Hubble Space Telescope imaged discs around the stars HD 138664 in the constellation Lupus, and HD 53143 in the constellation Carina.
The ices in the Kuiper Belt date back to the formation of the solar system.
They contain clues to conditions in the early solar nebula.
Oort Cloud

The Oort Cloud is an extended shell of icy objects that exist in the outermost reaches of the solar system.
It is named after astronomer Jan Oort, who first theorised its existence.
The Oort Cloud is roughly spherical, and is thought to be the origin of most of the long-period comets that have been observed.
This cloud of particles is theorized to be the remains of the disc of material that formed the Sun and planets.
Astronomers now refer to those primeval objects as a protoplanetary disk.
The most likely theory is that the material now in the Oort Cloud probably formed closer to the young Sun in the earliest epochs of solar system formation.
As the planets grew, and in particular as Jupiter coalesced and migrated to its present position, its gravitational influence is thought to have scattered many icy objects out to their present position in the Oort cloud.
The Oort Cloud is very distant from the Sun and it can be disrupted by the nearby passage of a star, nebula, or by actions in the disk of the Milky Way.
Those actions knock cometary nuclei out of their orbits, and send them on a headlong rush toward the Sun.

QUICK OORT CLOUD FACTS

Objects in the Oort Cloud are also referred to as Trans-Neptunian objects.

This name also applies to objects in the Kuiper Belt.
Some astronomers theorise that the Sun may have captured Oort Cloud cometary material from the outer disks of other stars that were forming in the same nebula as our star.
The Oort Cloud is a reserve of cometary nuclei that contain ices dating back to the origin of the solar system.
No one knows for sure how many objects exist in the Oort Cloud, but most estimates put it at around 2 trillion.
The planetoid Sedna, discovered in 2003, is thought to be a member of the inner Oort Cloud.
Astronomers think that long-period comets (those with orbital periods longer than 200 years) have their origins in the Oort Cloud.
Solar Eclipses

A solar eclipse is a natural event that takes place on Earth when the Moon moves in its orbit between Earth and the Sun (this is also known as an occultation).

It happens at New Moon, when the Sun and Moon are in conjunction with each other.
If the Moon was only slightly closer to Earth, and orbited in the same plane and its orbit was circular, we would see eclipses each month.
The lunar orbit is elliptical and tilted with respect to Earth’s orbit, so we can only see up to 5 eclipses per year.
Depending on the geometry of the Sun, Moon and Earth, the Sun can be totally blocked, or it can be partially blocked.
During an eclipse, the Moon’s shadow (which is divided into two parts: the dark umbra and the lighter penumbra) moves across Earth’s surface.
Safety note: do NOT ever look at the Sun directly during an eclipse unless it is during a total solar eclipse.
The bright light of the Sun can damage your eyes very quickly.

QUICK SOLAR ECLIPSE FACTS

Depending on the geometry of the Sun, Moon, and Earth, there can be between 2 and 5 solar eclipses each year.

Totality occurs when the Moon completely obscures Sun so only the solar corona is showing.
A total solar eclipse can happen once every 1-2 years.
This makes them very rare events.
The longest a total solar eclipse can last is 7.5 minutes.
The width of the path of totality is usually about 160 km across and can sweep across an area of Earth’s surface about 10,000 miles long.
Almost identical eclipses occur after 18 years and 11 days.
This period of 223 synodic months is called a saros.
During a total solar eclipse, conditions in the path of totality can change quickly.
Air temperatures drop and the immediate area becomes dark.
If any planets are in the sky at the time of a total solar eclipse, they can be seen as points of light.
Comets

A comet is a very small solar system body made mostly of ices mixed with smaller amounts of dust and rock.

Most comets are no larger than a few kilometres across.
The main body of the comet is called the nucleus, and it can contain water, methane, nitrogen and other ices.
When a comet is heated by the Sun, its ices begin to sublimate (similar to the way dry ice “fizzes” when you leave it in sunlight).
The mixture of ice crystals and dust blows away from the comet nucleus in the solar wind, creating a pair of tails.
The dust tail is what we normally see when we view comets from Earth.
A plasma tail also forms when molecules of gas are “excited” by interaction with the solar wind.
The plasma tail is not normally seen with the naked eye, but can be imaged.
Comets normally orbit the Sun, and have their origins in the Oort Cloud and Kuiper Belt regions of the outer solar system.

QUICK COMETS FACTS

The nucleus of a comet is made of ice and can be as small as a few meters across to giant boulders a few kilometres across.
The closest point in a comet’s orbit to the Sun is called “perihelion”.

The most distant point is called “aphelion”.
As a comet gets closer to the Sun, it begins to experience heat.
That causes some of its ices to sublimate (similar to dry ice sizzling in sunlight).
If the ice is close to the comet’s surface, it may form a small “jet” of material spewing out from the comet like a mini-geyser.
Material streams from comets and populates the comet’s orbit.
If Earth (or another planet) happens to move through that stream, those particles fall to Earth as meteor showers.
As a comet gets close to the Sun, it loses some of its mass due to the sublimation.
If a comet goes around enough times, it will eventually break up.
Comets also break up if they come TOO close to the Sun or another planet in their orbits.
Comets are usually made of frozen water and supercold methane, ammonia and carbon dioxide ices.
Those are mixed with rock, dust, and other metallic bits of solar system debris.
Comets have two tails: a dust tail (which you can see with the naked eye) and a plasma tail, which is easily photographed but difficult to see with your eyes.
Comet orbits are usually elliptical.
Many comets formed in the Oort Cloud and Kuiper Belts, two of the outermost regions of the solar system.
Comets are not spaceships or alien bases.
They are fascinating bits of solar system material that date back to the formation of the Sun and planets.
Asteroids

Asteroids are small, rocky solar system bodies that populate interplanetary space out to the orbit of Jupiter.
There are millions of them, and they are often grouped by their composition.
The planetary science community refers to them as minor planets, a general term applied to solar system bodies smaller than moons.
Asteroids are mainly made of materials left over from the formation of the inner solar system words.
Most of them orbit the Sun between Mars and Jupiter, although there are groups of them that orbit closer.
Asteroids come in three composition classes. C-types (chondrites) are made of clay and silicate rocks.
S-types are the so-called “stony” asteroids and are made mostly of silicate rocks and nickel-iron mixtures.
M-types are metallic nickel-iron.
These categories indicate how far from the Sun they formed in the early solar system.

QUICK ASTEROID FACTS

Asteroids aren’t the only things that hit Earth.
Each day, more than 100 tons of material from asteroids and comets falls toward Earth.
Most of it is destroyed by friction as it passes through our atmosphere.
If something DOES hit the ground, it is known as a meteorite.
While asteroid impacts were more common in the past, they aren’t as frequent today.
An asteroid impact some 65 million years ago contributed to the extinction of the dinosaurs.
(It was one of several factors that affected all life on Earth at that time.)
Earth suffers an impact from an object the size of a football field about once every 2,000 years.
A car-sized meteoroid (a piece of asteroid) falls into Earth’s atmosphere about once a year.
The result is a beautiful fireball, but the meteoroid usually burns up before reaching the ground.
Asteroids are rich in precious metals and other metals, as well as water.
Some asteroids are actually blown-out comets.
The ices are gone, and all that’s left is the rocky material.
Some asteroids have moons of their own!
Most asteroids orbit the Sun in the Asteroid Belt, which lies between Mars and Jupiter.
Asteroids are also referred to as minor planets or planetoids.
Meteorites

Earth is bombarded with millions of tons of space material each day.
Most of the objects vaporize in our atmosphere, but some of the larger pieces (from pebbles to boulder-sized rocks) actually fall to the ground.
Most of the objects come from asteroids, which are objects made of various types of rock and have existed since the origin of the solar system.
A small rocky or metallic chunk of material that travels through space is called a meteoroid.
Very small meteoroids (the size of dust) are often referred to as micrometeoroids or space dust.
These fragments may also be leftover comet debris, or were ejected in collisions between other solar system bodies such as the Moon or Mars.
As a meteoroid travels through our atmosphere, it is heated by friction.
That causes it to glow, and if this happens at night, we see a long streak of light known as a meteor.
If the object survives the trip and falls to Earth’s surface, it is known as a meteorite.
Many of these fall into the ocean (since about 71% of Earth’s surface is covered by water).
The rest fall on land, where they await discovery by meteorite hunters.

QUICK METEORITE FACTS

Millions of meteoroids travel through Earth’s atmosphere each day.
When a meteor encounters our atmosphere and is vaporized, it leaves behind a trail.
That “burning” meteoroid is called a meteor.
The appearance of a number of meteors occurring in the same part of the sky over a period of time is called “meteor shower”.
Many meteor showers are associated with comets, which leave behind debris as they orbit through the solar system.
Showers occur when Earth’s orbit crosses the path of a comet’s orbit.
Most meteorites are one of three types: stony, stony-iron, or iron.
These compositions tell us where the meteoroid existed in its parent body.
An iron or stony iron was close to the core of an asteroid, while a stony object was closer to the surface.
Meteor Showers

A meteor shower occurs when a number of meteors flash seem to radiate (or shoot out from) the same point in the sky.
They are usually named for the constellation in which their radiant appears.
The meteoroids in a shower usually come from the trail of debris left behind by a comet.
In the case of the Geminids and Quadrantids, those meteor showers come from the debris scatted by orbiting asteroids.
When Earth’s orbit intersects the dust trail, we see more meteors flaring as the cometary debris encounters our planet’s atmosphere.

QUICK METEOR SHOWER FACTS

Most meteor showers are caused by debris from comets.
When Earth moves through those debris trails, we see increased numbers of comets.
Two meteor showers are caused by debris shed by asteroids.
The Quadrantids are very likely caused by debris from the minor planet 2003 EH1.
The Geminid meteor shower comes from debris shed by asteroid 3200 Phaethon.
The Orionid Meteor shower (which occurs in late October each year) is created by dust and debris left behind by the passage of Comet 1P/Halley.
Meteors fall to Earth during the day, although we can’t see them.
It is very rare that a meteorite will strike a human being.
It’s more likely that it will fall into the ocean.
The best time to view a meteor shower is in the early morning hours, preferably on a dark, moonless night.
The earliest record of the Perseids meteor shower is found in Chinese annals from 36 AD.

Reference Sites for more information on Solar System

Nasa.gov
Nationalgeographic.com
Space.com
Space-facts.com
Science.howstuffworks.com

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