OUR SOLAR SYSTEM
Let's end our Astronomy section with a little review of our Solar System!
KING OF THE SKY
It is easy to understand why the Sun became associated with life, authority, power, and leadership in many cultures. Nearly every ecosystem on Earth ultimately depends on energy from the Sun. It was likely born as a twin, like stars usually are.
From Earth, the Sun appears to rise in the east, travel across the sky, and set in the west.
But the Sun is not actually circling Earth every day; we already know it's the other way a-round (see what I did there? HA HA). This apparent movement happens because Earth rotates from west to east. As Earth turns, the Sun appears to move in the opposite direction across our sky -- it rises on the East and sets on the West, no matter where you are on Earth.
From Earth, the Sun appears to rise in the east, travel across the sky, and set in the west.
But the Sun is not actually circling Earth every day; we already know it's the other way a-round (see what I did there? HA HA). This apparent movement happens because Earth rotates from west to east. As Earth turns, the Sun appears to move in the opposite direction across our sky -- it rises on the East and sets on the West, no matter where you are on Earth.
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The Sun's observed path over the Earth changes throughout the year. During summer, it follows a higher and longer path through the sky; during winter, its path is lower and shorter. This is one reason summer days are longer and winter days are shorter. These changes happen because Earth's axis is tilted.
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You can watch the theory of Sun's origins (and learn more about Nemesis!) in this video!
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Some places on Earth won't see much of a change; in places close to the Equator, the difference is only a few degrees, and it is warm all year around, even though this shift causes rainy and sunny seasons.
Our Solar System
Our Solar system includes everything affected by the Sun's gravitational pull. It includes the Sun at its centre, as well as everything orbiting around it: eight planets and numerous other objects, such as moons, asteroids, meteors and comets.
Our solar system was formed 4.6 billion years ago. It was believed that 4.7 billion years ago, gravity pulled a cloud of dust and gas together to form our solar system. The massive concentration of dust and gas created a molecular cloud that would eventually form the Sun. With the birth of a Sun, planets began to form 100 million years later around it.
Our solar system was formed 4.6 billion years ago. It was believed that 4.7 billion years ago, gravity pulled a cloud of dust and gas together to form our solar system. The massive concentration of dust and gas created a molecular cloud that would eventually form the Sun. With the birth of a Sun, planets began to form 100 million years later around it.
Size and Structure of the Solar System
The image below shows the size and structure of our Solar System, for comparison purposes. See how small Earth is compared to Jupiter, Saturn and the Sun. The furthest object that we can see in our solar system is Sedna, which is 143.73 billion Km away from the Sun. This means that the diametre of the Solar system is 287.46 billion Km.
There are eight planets in our solar system and one sun that each planet orbits around. An orbit is a regular, repeating path that one object takes around another. Therefore, all planets orbit the Sun, but their position varies thanks to their different mass. The Earth takes a year to go around the Sun, but some planets take much longer due to being so far away. Neptune, for instance, takes 165 years to orbit the Sun.
ORBIT DURATIONS
See how they increase depending on how far the planet is!
Mercury - 88 days to go around the Sun
Venus - 224.7 days
Earth - 365 days
Mars - 687 days
Jupiter - 12 years
Saturn - 29.5 years
Uranus - 84 years
Neptune - 164.8 years
Scientists found evidence that there may be a very large, ninth planet beyond Neptune, by tracking its gravitational pull -- but no one has spotted it yet!
Before we start checking out our Solar System's planets and seeing their different and unique stats, it's a good idea to talk about some of the terms we might hear.
Mercury - 88 days to go around the Sun
Venus - 224.7 days
Earth - 365 days
Mars - 687 days
Jupiter - 12 years
Saturn - 29.5 years
Uranus - 84 years
Neptune - 164.8 years
Scientists found evidence that there may be a very large, ninth planet beyond Neptune, by tracking its gravitational pull -- but no one has spotted it yet!
Before we start checking out our Solar System's planets and seeing their different and unique stats, it's a good idea to talk about some of the terms we might hear.
Equinox, Aphelion and Periphelion
Equinox: Twice a year, Earth's axis tilts neither toward nor away from the Sun, giving nearly equal hours of daylight and darkness worldwide. Occurs around March 21 (spring) and September 23 (autumn).
Perihelion: The point in Earth's elliptical orbit where it is closest to the Sun. About 91.4 million miles (147 million km) away. Happens in early January (about two weeks after the December solstice).
Aphelion: The point in Earth's elliptical orbit where it is farthest from the Sun. About 94.5 million miles (152 million km) away. Happens in early July (about two weeks after the June solstice).
Perihelion: The point in Earth's elliptical orbit where it is closest to the Sun. About 91.4 million miles (147 million km) away. Happens in early January (about two weeks after the December solstice).
Aphelion: The point in Earth's elliptical orbit where it is farthest from the Sun. About 94.5 million miles (152 million km) away. Happens in early July (about two weeks after the June solstice).
Definition of a Planet
- It must orbit a star (in our cosmic neighborhood, the Sun).
- It must be big enough to have enough gravity to force it into a spherical shape.
- It must be big enough that its gravity has cleared away any other objects of a similar size near its orbit around the Sun.
OUTER PLANETS
These are the planets that are farthest from the Sun. The outer planets are all called GAS GIANTS, because although they have rocky or metallic cores, they are mostly made of gassy sludge. Gas giants don't have defined outlines and are much larger than the terrestrial or inner planets.
The gas giant planets are Jupiter, Saturn, Neptune and Uranus.
Below, some general facts about these gas giants.
Composition:
Primarily composed of Hydrogen and Helium, with small amounts of other gases such as methane, ammonia, and water vapor.
Size:
They are much larger than terrestrial planets and have a massive size. Jupiter is the largest planet in our Solar system.
No solid surface:
Gas giants do not have a solid surface that one could stand on. They have thick atmospheres that become progressively denser as you move deeper into the planet. We say they have a mettalic core because the pressure is so high in the middle, that Hydrogen behaves like a metal, squished by the pressure.
Weather patterns:
These planets have internal heat sources that create intense weather patterns, such as powerful storms and winds that can reach up to several thousand miles per hour.
Strong magnetic fields:
Gas giants have strong magnetic fields that are much larger than Earth's.
Rings and moons:
Gas giant planets, such as Saturn and Jupiter, often have numerous moons and ring systems that orbit around them.
High density:
Despite their large size, gas giants have a relatively high average density, indicating they have a relatively small rock core, and large Hydrogen and Helium atmosphere.
Different colours and patterns:
Gas giant planets have different colours and patterns depending on the composition of their atmospheres and the weather patterns tha occur in them.
LIFE on a gas giant:
It is unlikely that life as we know it could exist on a gas giant planet. With nothing to stand on and an atmosphere with intense pressure and temperatures, the species we have on Earth would not survive in any of the gas giants.
More details on the outer planets can be seen below.
The gas giant planets are Jupiter, Saturn, Neptune and Uranus.
Below, some general facts about these gas giants.
Composition:
Primarily composed of Hydrogen and Helium, with small amounts of other gases such as methane, ammonia, and water vapor.
Size:
They are much larger than terrestrial planets and have a massive size. Jupiter is the largest planet in our Solar system.
No solid surface:
Gas giants do not have a solid surface that one could stand on. They have thick atmospheres that become progressively denser as you move deeper into the planet. We say they have a mettalic core because the pressure is so high in the middle, that Hydrogen behaves like a metal, squished by the pressure.
Weather patterns:
These planets have internal heat sources that create intense weather patterns, such as powerful storms and winds that can reach up to several thousand miles per hour.
Strong magnetic fields:
Gas giants have strong magnetic fields that are much larger than Earth's.
Rings and moons:
Gas giant planets, such as Saturn and Jupiter, often have numerous moons and ring systems that orbit around them.
High density:
Despite their large size, gas giants have a relatively high average density, indicating they have a relatively small rock core, and large Hydrogen and Helium atmosphere.
Different colours and patterns:
Gas giant planets have different colours and patterns depending on the composition of their atmospheres and the weather patterns tha occur in them.
LIFE on a gas giant:
It is unlikely that life as we know it could exist on a gas giant planet. With nothing to stand on and an atmosphere with intense pressure and temperatures, the species we have on Earth would not survive in any of the gas giants.
More details on the outer planets can be seen below.
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Neptune
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Uranus
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Saturn
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Jupiter
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INNER PLANETS
The four planets closest to the Sun are called the INNER PLANETS. All of the Inner planets are TERRESTRIAL PLANETS, which means "earthlike". The terrestrial planets are made of rocks and have iron cores, just like Earth. Many of the inner planets have craters, or holes on their surfaces, caused by rocks smashing into them.
The terrestrial planets in our solar system are Mercury, Venus, Earth and Mars.
Below, some general facts about the terrestrial planets:
Composition:
They are primarily composed of rock and metal and have a solid surface.
Size:
They are typically smaller than gas giant plants and have a higher density.
Geology:
They have a varied Geology, and can have mountains, valleys, canyons and other landforms.
Different atmospheres:
Terrestrial planets have different atmospheres depending on the specific planet, for example Earth has a diverse climate and weather patterns, while Venus has a thick atmosphere that causes a greenhouse effect.
Strong magnetic fields:
Some terrestrial planets like Earth have strong magnetic fields that protect the planet from harmful solar radiation.
Different colours and patterns:
Terrestrial planets have different colours and patterns depending on the composition of their surfaces and atmospheres.
Closer to the Sun:
Terrestrial planets are located in the inner part of the solar system, closer to the sun.
Life on Terrestrial Planets:
Life on other terrestrial planets hasn't been discovered. Mars has a dry and cold environment, and we are currently searching for life on it. Scientists are constantly searching for signs of life on other planets as well, although we have not landed on them. We are looking at traces of life on Venus, as well as other planets and moons in our solar system and beyond.
The terrestrial planets in our solar system are Mercury, Venus, Earth and Mars.
Below, some general facts about the terrestrial planets:
Composition:
They are primarily composed of rock and metal and have a solid surface.
Size:
They are typically smaller than gas giant plants and have a higher density.
Geology:
They have a varied Geology, and can have mountains, valleys, canyons and other landforms.
Different atmospheres:
Terrestrial planets have different atmospheres depending on the specific planet, for example Earth has a diverse climate and weather patterns, while Venus has a thick atmosphere that causes a greenhouse effect.
Strong magnetic fields:
Some terrestrial planets like Earth have strong magnetic fields that protect the planet from harmful solar radiation.
Different colours and patterns:
Terrestrial planets have different colours and patterns depending on the composition of their surfaces and atmospheres.
Closer to the Sun:
Terrestrial planets are located in the inner part of the solar system, closer to the sun.
Life on Terrestrial Planets:
Life on other terrestrial planets hasn't been discovered. Mars has a dry and cold environment, and we are currently searching for life on it. Scientists are constantly searching for signs of life on other planets as well, although we have not landed on them. We are looking at traces of life on Venus, as well as other planets and moons in our solar system and beyond.
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Mercury
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Venus
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Mars
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Earth
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Planet Earth has five different "air" layers, with different characteristics as you can see below:
- Troposphere: Where we live! Weather, rain, winds, all of these phenomenon are in this layer. It contains almost all the water molecules and 75% of all of the "air" molecules. The higher you go, the colder it gets.
- Stratosphere: This is the layer right above the Troposphere. It contains most of the Ozone in the atmosphere. This layer gets hotter the highest you go, because of the absorption of UV radiation from the Sun.
- Mesosphere: In this layer, the higher you go, the coldest it gets. Because it is so hot at its lowers area, most of the meteors that enter our atmosphere burn in this layer (and the rest burn off in the Stratosphere!)
- Thermosphere: This layer gets super hot the higer you go, due to the absorption of xrays and UV radiation from the Sun.
- Exosphere: This is the highest you can go and still be on "Earth". This is where the Moon resides.
THE MOON
After the Sun, the Moon is the most important celestial body for the Earth. It affects our tides, the light at night, and many have considered that it may even affect human and animal behaviour, perhaps due to melatonin fluctuations.
The Moon formed about 4.5 billion years ago, when a Mars-sized proto-planet named Theia crashed into the early Earth. The extreme impact threw massive amounts of melted rock and gas into space. This orbiting ring of debris quickly came together to form our natural satellite, the Moon, within just a few thousands of years. This theory is accepted as true because samples from NASA Apollo missions show that Earth and the Moon share very similar chemical and isotope patterns. The Moon also has a very small iron core compared to Earth, which fits computer models where lighter surface materials are blasted into orbit while heavier iron sinks to Earth's core.
The Moon formed about 4.5 billion years ago, when a Mars-sized proto-planet named Theia crashed into the early Earth. The extreme impact threw massive amounts of melted rock and gas into space. This orbiting ring of debris quickly came together to form our natural satellite, the Moon, within just a few thousands of years. This theory is accepted as true because samples from NASA Apollo missions show that Earth and the Moon share very similar chemical and isotope patterns. The Moon also has a very small iron core compared to Earth, which fits computer models where lighter surface materials are blasted into orbit while heavier iron sinks to Earth's core.
OTHER THINGS IN OUR SOLAR SYSTEM
Asteroids: Huge chunks of irregularly shaped rocks. They can be found mostly in separate areas of our Solar system (thank goodness!)
We have a disk-like ASTEROID BELT between Mars and Jupiter, as well as two donut-shaped structures called Kuiper Belts. These giant donuts are mostly formed by asteroids. More on Kuiper belts later!
Comets: dirty snowballs made of dust, rock particles, frozen gases, and ice that are orbiting the Sun, usually with enormous orbits. They can take years and years to return. They are sometimes visible to the naked eye when they pass through the inner Solar system because of their long tails -- caused when they are partly vaporized by the Sun (the tail does not follow behind the comet, it always points toward the Sun!)
Oort cloud: A cloud of billions of comets beyond Pluto, named after astronomer Jan Oort, who first proposed the model. More about Oort clouds later!
Meteoroids, Meteors, Meteorites: Meteoroids are small pieces of rock and dust. They become meteors (shooting stars!) when they enter the Earth's atmosphere and burn from all of the atmosphere friction into a bright and hot streak. Most meteors burn out and never reach the Earth; the ones that makes it to Earth without turning into dust are called meteorites, and some people like to collect these.
We have a disk-like ASTEROID BELT between Mars and Jupiter, as well as two donut-shaped structures called Kuiper Belts. These giant donuts are mostly formed by asteroids. More on Kuiper belts later!
Comets: dirty snowballs made of dust, rock particles, frozen gases, and ice that are orbiting the Sun, usually with enormous orbits. They can take years and years to return. They are sometimes visible to the naked eye when they pass through the inner Solar system because of their long tails -- caused when they are partly vaporized by the Sun (the tail does not follow behind the comet, it always points toward the Sun!)
Oort cloud: A cloud of billions of comets beyond Pluto, named after astronomer Jan Oort, who first proposed the model. More about Oort clouds later!
Meteoroids, Meteors, Meteorites: Meteoroids are small pieces of rock and dust. They become meteors (shooting stars!) when they enter the Earth's atmosphere and burn from all of the atmosphere friction into a bright and hot streak. Most meteors burn out and never reach the Earth; the ones that makes it to Earth without turning into dust are called meteorites, and some people like to collect these.
