I have written this article in the form of a story. I hope you are going to enjoy the ride.
Imagine you are on a spaceship, a powerful one perhaps, you would want to travel to the edge of our solar system and come back to Earth. You know it will be an arduous journey, yet you are determined to do it. You would want to explore all the planets, comets and asteroids along the way. You buckle up and start reading your notes about planets, and the countdown begins ten, nine, eight…..
Our solar system: Introduction
Our solar system has the sun at its centre, and all the planets, asteroids and other objects revolve around it. Overall, there are eight planets and numerous asteroids in our solar system.
These eight planets are divided into territorial planets, gas giants and ice giants. The terrestrial planets are chiefly made up of rock and metals. In other words, they have a solid surface composed of silicate and metals. Mercury, Venus, Earth and Mars are the four terrestrial planets in our solar system. Gaseous planets don’t have any solid surface; instead, they are composed mainly of Hydrogen and Helium. Jupiter and Saturn are two gas giants.
Icy giants, too, don’t have a solid surface. They are composed primarily of volatile substances such as ammonia, methane etc. Uranus and Neptune are the two icy planets. Collectively these gaseous planets are known as Jovian planets. Apart from these, five dwarf planets and moons, asteroids, icy particles etc., together constitute our solar system.
Our solar system revolves around the centre of the milky way galaxy with a speed of 828,000 kmph. Our milky way galaxy is a barred spiral galaxy. We are located in the Orion arm of the milky way, about 25000 light-years away from the centre. Milky way is one of several billions of galaxies in our universe. Learn more about many interesting things about our universe here: http://walktoinfinity.com/our-universe/
Our solar system was formed more than 4.5 billion years ago. Scientists assume that our solar system was formed from a massive accumulation of gases, chiefly molecular hydrogen and dust particles called a molecular cloud. Molecular clouds are vast, typically hundreds of light-years across, have a temperature of 7K. This extremely low temperature coupled with high-density causes the gravitational collapse of these dense clumps. A supernova could have triggered this gravitational collapse. Many stars, including our sun, were formed this way.
Initially, this dense clump of matter starts to spin and becomes very hot. The matter surrounding it starts to revolve around the centre. This process continues for hundreds of years, and a protostar is formed. Read more about the life cycle of a star here.
Planets and other objects in a solar system are formed from this rotating matter through accretion. The terrestrial planets have rocky surfaces because, below 4 AU, it was too hot for the gases to condense, and only rocky particles were left behind. Also, silicates and other metals are relatively rare. Hydrogen and other gases that make up much of gaseous giants are abundant in our universe. Beyond the frost line, there was an accretion of massive clumps of rocks and ices forming a solid core, and its strong gravity pulled in enormous quantities of hydrogen and other gases, so these jovian planets were formed.
Your spaceship grinds to a halt. You look at one of the brightest planets in our solar system. You read the name Venus on the signboard.
Venus: the scorching one
Venus is the closest planet to Earth. This planet is named after the Roman goddess of beauty and love. As the name suggests, it is the brightest planet in our solar system. Frequently known as Earth’s sister planet due to its similarity in size, mass etc., the atmospheres of both worlds couldn’t be any more different. It is the hottest planet in our solar system due to the runaway greenhouse effect. Its surface has a vast number of volcanoes. Its atmosphere is chiefly composed of CO2, and very thick sulphuric acid clouds spread all over the planet. Also, the atmosphere is very dense, making life impossible to form.
Our models suggest that Venus could have been habitable planet aeons ago, but its water vapour evaporated and created such a climate because of its close proximity to the sun. Venus has a metallic iron core and a weaker magnetic field than ours.
Facts about Venus
1) Diameter: 12,104 km (while Earth’s is 12742 km)
2) Surface temperature: 463C
3) Distance from sun: 0.72AU
4) Orbital period: 224 days
You are mesmerised by the brilliant and yet hellish planet, Venus. Next up is the smallest and the closest planet to the sun, Mercury.
Mercury: the diminutive one
The planet gets its name from the Roman god of travellers, commerce, and transporter of goods, Mercury. Being the closest planet to the sun, Mercury completes its revolution in about 88 days. Its day-night temperatures shift dramatically, ranging from a scorching 450C during the daytime to a freezing -173C at night. It has a huge metallic core, and its surface has numerous craters formed after collisions with asteroids. It has a very thin atmosphere and is chiefly composed of Hydrogen, oxygen, Helium, potassium and nitrogen. It also has a very weak magnetic field. Also, some scientists assume that its poles contain ice. To know more about the planet mercury, click here: https://solarsystem.nasa.gov/planets/mercury/in-depth/
Facts about Mercury
1) Distance from the sun: 0.4AU
2) Diameter: 4,878 km, slightly larger than our moon.
3) Time to complete one rotation: 59 days
4) Moons: None
You just have witnessed the diminutive planet, Mercury. Now, let us know more about our home planet, Earth.
Earth: the habitable one
Our home planet is the only planet known to support life in the observable universe. Due to its ideal distance from the sun, it supports life. As we all know, its atmosphere is chiefly composed of nitrogen and oxygen. Of all the terrestrial planets, it is the largest and the densest one. A strange fact is that the equator of our planet moves faster than the poles. Our planet has a solid iron core with a thick mantle layer made up of silicate rocks. Earth has a tidally locked moon, which might have formed due to a collision with a giant asteroid.
Facts about the Earth
1) Distance from the sun: about 93 million miles(1 AU)
2) Speed of revolution: 29km/sec
3) Hottest temperature: 56.7C, recorded at Death Valley, USA
4) Coldest temperature: -89.2C, recorded at Vostok, Antarctica
5) Distance to the moon: 384,400 km or 0.002569 AU
Next, you are headed to a red planet, Mars.
Mars: the red one
Mars is fondly known as the red planet. Its iconic colour is caused by iron oxide, found aplenty on its surface. This planet is named after the Roman god of war, Mars. This planet has numerous craters, valleys, volcanoes and mountains. The largest volcano in our solar system, Olympus Mons, has a height of nearly 22 kilometres. Its atmosphere is very thin, comprised chiefly of CO2 and trace amounts of nitrogen and argon. Temperatures during daytime(20C) and nighttime(-73C) vary considerably, making it very difficult to sustain life. Many unmanned explorations have happened on Mars. Also, recent studies suggest that mars might have had conditions that support life billions of years ago.
Facts about Mars
1) Distance from the sun: 1.5 AU
2) Time to take one rotation: 24 hours and 37 minutes
3) 1 year on Mars: 687 days
4) No of moons: 2 (Phobos and Deimos)
5) Diameter: 6,787 km
You are exhausted but want to continue. Next, you are heading to the king of all planets in our solar system, Jupiter.
Jupiter: the giant one
upiter is the biggest and the most massive planet in our solar system. It is so massive that it still weighs more than twice the other planets combined. It is named after the king of Roman gods, Jupiter. Being a gas planet, it doesn’t have a solid surface. Its atmosphere is primarily made up of hydrogen and small amounts of helium. The pressure increases as you descend deeper into its atmosphere. This planet has very turbulent and extreme weather conditions, with flashes of lightning and powerful storms rocking the planet every minute.
It is also famous for its Great Red Spot, a powerful anticyclonic storm that continues to occur to this day. It has a strong magnetic field due to liquid hydrogen in its inner layers. Although Jupiter has the necessary components to become a star, it’s not as massive to become a star.
Facts about Jupiter
1) Distance from the sun: 5.2 AU
2) Diameter: 139,822 km
3) Mass of Jupiter: 1.898 × 10^27 kg
4) Orbital period: 12 years
5) 1-day on Jupiter: 10 hours
6) No of moons: 79
As you are travelling farther from the sun, everything outside looks dimmer. Glad you are on a powerful spacecraft. Next up, Saturn. You return to your notes about the planet.
Saturn: the one with the rings
When we think of Saturn, its brilliant rings come to mind. Saturn rings are made of ice particles, small rocks and dust. The planet is named after the Roman god of agriculture and wealth, Saturn. It is the second biggest planet in our solar system, after Jupiter. Like Jupiter, its atmosphere consists chiefly of molecular hydrogen and small amounts of helium. It has a solid metallic core surrounded by liquid hydrogen that causes a magnetic field. Also, Saturn has less density than water. The temperatures and pressures inside this gas giant are far too intense for any organism to form. One of its many moons, called Enceladus, is thought to host microbial life.
Facts about Saturn
1) Distance from the sun: 9.5 AU
2) Diameter: 116,460 km
3) Mass of Saturn: 5.7 × 10^26 kg
4) Orbital period: 29 years
5) 1-day on Saturn: 10 hours and 42 minutes
6) No of moons: 83
After you witness one of the many wonders of the solar system, you are headed straight to the eighth planet. The planet gives off a thick, pungent smell. Yikes.
Uranus: the stinky one
Uranus is named after a Greek god, Ouranos and is the only planet named after a Greek deity rather than a Roman god. It has a blue-green colour due to the presence of methane gas in its atmosphere. Uranus is very frigid and windy and is considered the coldest planet in the solar system, with freezing -224C. Uranus is also a gas giant without any rocky surface. Like the gas giants, the atmosphere of Uranus is chiefly composed of hydrogen and helium but with higher compositions of methane, ammonia and water. It has a relatively smaller rocky core, water and ammonia present as oceans in the mantle. It has an unusual axis of rotation, which might have occurred due to an impact with a massive object.
Facts about Uranus
1) Distance from the sun: 19.8 AU
2) Diameter: 50,724 km
3) Mass of Uranus: 8.7 × 10^25 kg
4) Orbital period: 84 years
5) 1-day on Uranus: 17hours and 14minutes
6) No of moons: 27
Phew, one more to go.
Neptune: the windy one
Neptune is a brilliant blue icy planet named after the Roman god of the sea. It is the only planet in the solar system not visible to the naked eye. It is the fourth-largest and third most massive planet in our solar system. It is a frigid and windy planet with temperatures dipping below -240C. Though not very clear, scientists assume that it has a small solid core made up of iron, silicates and nickel, and its mantle has liquid oceans of water and ammonia. Its top layer of the atmosphere consists of hydrogen and helium. The Great dark spot on Neptune is a raging storm that resembles the Great red spot on Jupiter.
Facts about Neptune
1) Distance from the sun: 30.1 AU
2) Diameter: 49,244 km
3) Mass of Neptune: 1.024 × 10^26 kg
4) Orbital period: 165 years
5) 1-day on Neptune: 16hours and 6minutes
6) No of moons: 14
After you are done with your exploration, you head back to your home, thinking about all the fantastic yet terrifying objects in our solar system.