Our Solar System

How our Solar System formed

• Meteorites are tiny pieces of rock or metal which fell into earth’s atmosphere from outer space.

• 90% of meteorites are made from rocky material while the last 10% are made from metal like iron or nickel.

• Scientists can use this information to figure out all sorts of things about how our solar system formed.

• By studying these meteorites we are able to say that our solar system is about 4.6 billion years old.(Remember, our universe is nearly 14 billion years old! )

Meteorites

Pictured above are some examples of meteorites that have landed on Earth

• Meteorites range from very small to quite large!

• When they enter Earth’s atmosphere forces like friction, pressure and chemical reactions begin to burn away the outer layers of the meteorite. This can cause it to shrink quite a lot before it finally hits the surface. So it’s not surprising that most meteorites tend to be quite small!

Meteor caught on video!

• This video shows a meteor that was videoed burning through the sky across Russia. See how hot and bright it burns?

https://www.youtube.com/watch?v=90Omh7_I8vI

Formation of the Solar System

• By looking at how old these meteorites are and by seeing what they are made of, we can come up with a theory for how our solar system formed.

• It’s believed that the solar system began as a large molecular cloud.

• This cloud was mostly made up of Hydrogen and Helium and a few heavier elements like carbon and iron. All of the elements in this cloud were most likely the leftovers from an older star that reached the end of it’s life-cycle and went supernova!

• Carbon only comes from stars that went supernova and most life forms on Earth are carbon-based. So this means that we were once part of stars millions and millions of years ago!

A Typical Gas Cloud

Pictured above is the “Boogie Man Nebula”. These are regions were stars are born. See the young stars in the cloud?

The Nebula Hypothesis• Stars are born when a gas cloud is compressed by a shockwave.

• The process began when a shockwave from a nearby supernova caused a wave of pressure in the gas cloud, a lot like the ripples in a pond when you throw a rock in!

• This caused the molecules in the cloud to clump together and these clumps would then have collapsed under their own gravity.

• As they collapse they start to spin and form a ball shape.

• The nebula around the ball would form a disk of material which rotates about the centre.

• As the central ball rotates faster and gets bigger, it starts to get hotter and form what we call a “Protostar”. This is basically just a baby star.

This picture shows how a gas cloud might turn into a protostar and then a solar system

• After the protostar is formed, it gets bigger and hotter until is starts a nuclear reaction. We’ll talk more about this nuclear reaction later on when we talk about stars and their life-cycles.

• Once the nuclear reaction begins, the protostar sheds almost half of its mass and becomes a young star.

• The shedded mass causes another small ripple in the material around the star which causes smaller clusters to form into planet-forming discs.

This picture is from the Hubble Telescope. It shows small planet-forming discs in the Orion nebula!

• This video shows a planet-forming disc with a bright protostar in the centre.

http://upload.wikimedia.org/wikipedia/commons/transcoded/c/cc/Artist%27s_impression_of_the_disc_around_a_young_star.ogg/Artist%27s_impression_of_the_disc_around_a_young_star.ogg.360p.webm

• Did you see the shockwaves and the young planets in the disc?

Rocky Planets• The main theory we have today is that in the planet-forming disc, the planets would

start as little grains of dust and rocks.

• Every year they would grow by about 1cm for millions of years until they formed the planets we have today.

• The area closest to the sun was way too hot for gas planets to hold their shape. This meant that for a planet to form in this region it would have to be made of something with a high melting point, like carbon or iron.

• It’s not surprising then to learn that Mercury, Venus, Earth and Mars are made up mostly of a rocky surface with a molten Iron core. We call these planets “Terrestrial planets”.

• These elements are quite rare in space so the terrestrial planets are much smaller than the gas giants.

• Some of these planets managed to snag some of the gas and dust around them which formed their atmospheres and moons. (Although, some moons began life as a comet that might have knocked into the planet in its early years).

The Frost Line

Pictured above is the Frost Line. It divides the hot zone where the rocky planets form and the cold zone where the gas planets form.

Gas Planets• Beyond the frost line elements like hydrogen and

helium could form planets that wouldn’t evaporate.

• These planets became huge because there was so much hydrogen and helium in the gas cloud to make them! In fact they make up 99% of the mass that orbits the sun!

Recap• Lets take a quick recap so far! This video uses

really awesome animations to describe what we’ve just learned!

https://www.youtube.com/watch?v=Uhy1fucSRQI

Mercury • Mercury is the smallest of the 8

planets and also the closest to the sun. (We say 8 planets because Pluto is technically a dwarf planet and doesn’t count. We’ll explain why later). In fact Mercury is even smaller than the moons Ganymede and Titan!

• A year on Mercury is only 88 Earth days but a day on Mercury is 58.6 Earth days.

• It is named after the Roman God Mercury, who was the messenger to the Gods.

Mercury• Mercury has no moons because of

how close it is to the sun. Any objects caught in orbit around Mercury don’t tend to survive long because the sun’s gravity has such a strong affect.

• We have man-made satellites like MESSENGER (pictured across) in orbit around mercury but every now and then the on-board rockets have to fire to keep it from crashing into the surface!

• Mercury has perhaps the strangest rotation of the 8 planets. If you lived on Mercury it would take nearly two years for you to see the sun rise and set again!

Venus• Venus is the second closest planet to the sun

with a year as long as 224.7 Earth days.

• Just like Mercury it has no natural satellites or moons.

• Venus is the second brightest object in the night sky next to the Moon itself. It can even cast shadows on Earth in certain circumstances!

• Venus is often called Earth’s “sister planet” because it’s so similar in size, density and closeness to the sun. But unfortunately the atmosphere on Venus is about 96% carbon dioxide, ruling it out as a planet we could live on.

• Other reasons why we couldn’t live on Venus is that the pressure is 92 times stronger than Earth’s. It is also the hottest planet in the Solar System with a surface temperature of 462 degrees Celsius!

Venus• Venus is covered in really

dense clouds of sulfuric acid making it difficult to see the surface with visible light. The picture you see here is a radar image taken by the Magellan probe.

• The Magellan probe is no longer functioning today because it was sent to its destruction into the atmosphere of Venus so that it could give us information about its density and strutcture.

Vanera Lander Missions

• This image of the Venusian surface was taken by the Vanera 13 lander.

• The Vanera landers were a series of missions dedicated to studying the surface of Venus. They returned the first colour images of the planet’s surface and some detail about its soil composition.

Earth• The 3rd rock from the sun and also the

only known astronomical object to accommodate life!

• Using radiometric dating and other techniques we can confidently say Earth was first formed 4.5 billion years ago

• Earth has only one natural satellite, the Moon.

• Today we believe the Moon originated from the Great Impact Theory. This theory states that the Moon was the result of a collision between a young planet Earth and the proto-planet Theia. This explains why the Moon is so similar to the Earth’s crust.

Mars• Mars is the second smallest planet in the

solar system and also the 4th planet from the sun.

• It gets its red colour from the large amounts of Iron Oxide on the surface. This is very similar to rust that form on metal!

• Mars has a very thin atmosphere and as such we can see a lot of impact craters similar to those found on the moon. This is because the atmosphere hasn’t done a very good job of protecting the planet from meteors as its atmosphere is too thin to properly burn them up.

• Just like Earth, Mars has volacanoes, valleys, deserts and even Polar ice caps!

• A year on Mars is 687 Earth days but a Mars day is roughly the same at about 24hrs and 40mins.

Mars• If you download the Google Earth App there is a

setting which lets you explore the surface of Mars!

• Mars has two moons, Phobos and Deimos, which are quite small and strangely shaped. We think this is because they are captured asteroids.

• Mars is easily the most studied of the planets (next to Earth!) with 7 functioning spacecraft in orbit and on the surface. These include 5 satellites and the 2 rovers, Opportunity and Curiosity (Curiosity selfie pictured across). Curiosity’s selfie is made up of many panoramic pictures it took from a camera on one of it’s robotic arms.

• Curiosity has already told us that Mars soil contains between 1.5% and 3% water.

• Unfortunately the atmospheric pressure on Mars is too low for liquid water and so it mostly takes the form of ice.

• Mars is also where you’ll find the largest known mountain in the solar system, Mons Olympus.

Jupiter• Jupiter is the largest of the gas giants and

the largest planet in the solar system.

• Jupiter is HUGE. It’s mass is 2.5x bigger than the mass of all the other planets combined!

• In fact Jupiter is so big and easily seen that even the Ancient Romans knew about it and named it after their King of the Gods.

• The points where the bands on the surface meet are areas of high turbulence and storms. This is what causes the Great Red Spot, a rampant storm which has been on-going since the 17th century.

• Jupiter has at least 67 moons! Some of them are even thought to contain water. Future missions aim to explore Europa in the hope that it contains an ice-covered liquid ocean!

Jupiter• Jupiter has been explored

before by the robotic spacecraft Pioneer and Voyager 1 fly-bys and eventually again by the Galileo orbiter (seen pictured).

• NASA launched another Jupiter-bound spacecraft in August 2011 called Juno. It is expected to reach the planet in late 2016.

Jupiter Size Comparison

Jupiter’s Rings

Jupiter has very feint but very large rings as seen in the picture above.

Jupiter’s Moons

The 4 Gallilean moons can be seen above: Io, Europa, Ganymede, Callisto.

Saturn• Saturn is the second largest planet in

the solar system after Jupiter. Most famously recognised by its intense ring system.

• Saturn gives off a pale yellow colour due to ammonia crystals in the upper atmosphere.

• The planet’s ring system consists of 9 continuous rings and 3 arcs. These are just broken rings made up of mostly ice particles.

• It is known to have almost 150 moons, of which only 53 have official names. Titan is Saturn’s largest moon and is the second largest moon in the solar system. Titan is even bigger than Mercury!

Saturn’s structure

Astronomers believe that Saturn has a rocky core surrounded by ice, metallic, liquid and gassy Hydrogen.

Saturn’s Rings• Each of Saturn’s rings are

about 20km thick and are made mostly of ice water.

• There are two ways that Saturn could’ve gotten its rings. Firstly it could’ve been the result of a destroyed moon. Secondly it may have been left over particles from the nebula which Saturn formed in.

Uranus• Uranus and Neptune are

slightly different from the Gas Giants Jupiter and Saturn in that they’re mostly made of ice.

• Uranus has the coldest atmospheric temperature which reaches a minimum of -224.2 degrees Celsius!

•

The Unfortunate Name• Uranus has had many different names

before it was finally settled on.

• It was first discovered by a man named Herschel who, true to his king and country, suggested that it be called George’s Star after King George.

• Of course not everyone outside of England agreed with this and had instead suggested naming it Herschel, after the man who discovered it.

• A German astronomer, Johann Bode suggested the name Uranus, a Latinised version of the Greek God of the sky, Ouranos. The name stuck when Bode’s friend discovered a new element and named it Uranium to help him.

Neptune• Neptune is the furthest planet from

the sun. Named after the Roman God of the Sea.

• Neptune was the first plant to be discovered by prediction rather than actually seeing it in the sky. Alex Bouvard predicted its existence when he saw weird changes in Uranus’ orbit. He figured it must have been the gravity of a nearby planet.

• Neptune is an ice giant and is very similar to Uranus. But it’s atmosphere is much clearer and we can see some weather patterns. The dark blue spot you see here is actually very similar to the Great Red Spot on Jupiter.

Pluto (The Dwarf Planet)

• Pluto is a object in the Kupier Belt, a large asteroid belt that orbits the sun beyond the planets.

• Pluto is only the 2nd most massive dwarf planet in the known solar system after Eris.

• We all know that since 2006, Pluto was officially declared NOT a planet. This upset a lot of people but there is a lot of really good reasons for it.

Computer generated image of

Pluto

Pluto• After discovering other large objects in

the Kupier Belt a decision had to be made whether to include pluto and all it’s buddies as planets, or to make a special group just for them.

• The International Astronomical Union (IAU) got together in 2006 and decided to set down a few ground rules so we can say once and for all what a planet is.

• The rules were:1) The object must orbit the sun2) The object must be big enough that gravity makes it form into a ball.3) It must have cleared the area around its orbit.

• The last rule is where Pluto falls short because its neighbourhood is littered with similar objects that are pretty much the same size.