Our solar system is an awe-inspiring part of the universe. It is embedded within the vast expanse of the Milky Way’s Orion star cluster, about 27 thousand light years from the galactic center. But what is so special about our own cosmic backyard? What makes our solar system so unique? Our remarkable birthplace is one of over 3200 known star systems that make up our milky way galaxy. However, only one percent of these star systems have the same number of planets as our solar system or more. It is estimated to have formed around 4.5 billion years ago, when a swirling disc of interstellar gas and dust collapsed, creating a solar nebula. At its center lies our sun, a life-giving star that is one of the 20% of stars in the galaxy that host Earth-like planets.
The Sun
The Sun is a blazing ball of gas, located about 150 million kilometers away from Earth. This distance is called one astronomical unit. The Sun is the brightest object in our sky, the source of most of the energy on Earth, and the center of our solar system, with eight planets orbiting around it. The Sun is classified as a yellow dwarf star, and its surface temperature is a scorching 6000 degrees Celsius. Its surface is constantly changing, producing solar flares and sunspots. Its immense gravity holds the solar system together, making up 99.8% of the solar system’s mass. The Sun is mainly composed of hydrogen and helium. But the Sun is more than just a ball of gas and dust. It is a powerful nuclear fusion reactor, converting hydrogen into helium and releasing an incredible amount of energy in the process. This reaction releases a tremendous amount of energy in the form of light and heat, equivalent to the energy released by approximately 9 million atomic bombs every second. The Sun is truly a magnificent force of nature!
The inner planets: Mercury and Venus
Revolving around the sun are eight planets, divided into two categories based on their composition: Terrestrial and Jovian. The four Terrestrial planets, Mercury, Venus, Earth, and Mars are made of rocky material and have solid surfaces. Mercury is the smallest and closest planet to the Sun, zipping around it in a mere 88 Earth days Its surface is covered in craters and its atmosphere is virtually non-existent. But what it lacks in air it makes up for in temperature variation – ranging from a frigid -173 degrees to a scorching 427 degrees Celsius! Venus is a blazing inferno of a planet, second only to the Sun in brightness in the night sky. Venus’s thick atmosphere traps heat, creating a runaway greenhouse effect. Its scorching surface temperature of 462 degrees Celsius makes it the hottest planet in the Solar System. It is also home to the most active volcanoes, with over 1600 of them erupting across its surface. Venus rotates very slowly on its axis: One day on Venus lasts 243 Earth days. The planet orbits the Sun faster than Earth. One year on Venus takes only about 225 Earth days. This makes a Venusian day last longer than its year!
Earth and Moon
Earth is the only planet in our solar system that is teeming with life! It is the third planet from the Sun and the fifth largest in the solar system. The name Earth is a Germanic word, which simply means “the ground.” Its surface is unique in that it is the only one with liquid water. Earth’s oceans cover nearly 70% of the planet’s surface and contain 97% of Earth’s water. These vast oceans provided a convenient place for life to begin about 3 point 8 billion years ago. Earth has an atmosphere that consists of 78% nitrogen, 21% oxygen, and 1% other gases such as argon, carbon dioxide, and neon. The atmosphere affects Earth’s long-term climate and short-term local weather and shields us from much of the harmful radiation coming from the Sun. It also protects us from meteors, most of which burn up in the atmosphere before they can strike the surface. The Moon is the only companion of Earth, shining brightly in the night sky! It is the fifth largest moon in the Solar System, with a gravity only one-sixth of Earth’s. Its surface is barren but covered with craters, mountains, and valleys. The Moon’s temperature can span from 123 degrees to minus 233 degrees Celsius. Its orbit around Earth is elliptical, and its rotation is tidally locked, meaning the same side of the Moon always faces us. The Moon makes Earth a more livable planet by moderating our home planet’s wobble on its axis, leading to a relatively stable climate. It also causes tides, creating a rhythm that has guided humans for thousands of years.
Mars
Mars, the Red Planet, is an exciting world, named after the Roman god of war. It is the fourth planet, at 1 and a half astronomical units from the Sun. Mars is about half the size of Earth, making it the second smallest planet in our solar system. The gravity on Mars is only about one-third of Earth’s gravity, making it a great place to experience a feeling of weightlessness! Mars completes one rotation every 24 point 6 hours, which is very similar to one day on Earth. A year on Mars lasts 687 Earth days. Much like Earth, Mars’ axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This tilt causes Mars to have distinct seasons that last about twice as long as on Earth since it takes Mars about twice as long to orbit the Sun. Mars has a very thin atmosphere compared to Earth, composed mostly of carbon dioxide. The temperature on Mars can range from -125 to 20°C, making it a very cold and hostile environment. The dust storms on Mars are also fascinating, as they can cover the entire planet and last for weeks. The surface of Mars is covered in iron oxide, giving it a red rusty color, made up of soil, rock, and dust. Mars is home to Olympus Mons, the largest volcano and highest mountain, and the Borealis Basin, the biggest crater in our solar system. It also has the largest canyon in our solar system, Valles Marineris, which is 7 kilometers deep and stretches about 4800 kilometers long. That’s about 10 times the size of the Grand Canyon. Although there is no definitive evidence of life on Mars, scientists believe there is potential for life under its surface. Mars is an exciting world, and it is the planet that humans will most likely step foot on first.
Jupiter and its four Galilean moons
The four Jovian planets, Jupiter, Saturn, Uranus, and Neptune are gas and ice giants. They are predominantly made of helium and hydrogen. The ice giants also contain rock, ice, and a liquid mixture of water, methane, and ammonia. All four Jovian planets have multiple moons, and ring systems, and are immense. Jupiter is an awe-inspiring gas giant, the fifth planet from the Sun and the largest in the Solar System. Jupiter is called a failed star because it is made of the same elements as the Sun, but it is not massive enough to have the internal pressure and temperature necessary to cause hydrogen to fuse to helium which powers the sun and most other stars. Its mass is two and a half times that of all the other planets combined, and its magnetic field is an incredible 14 times stronger than Earth’s. Jupiter’s days are incredibly short. With a rotation period of only 10 hours, Jupiter is the fastest-spinning planet in the Solar System. It has between 80 and 92 moons, the most of any planet, and its Great Red Spot is the largest storm in the solar system that has been raging for centuries. Jupiter’s Great Red Spot was first observed in 1831, so we know the storm has existed for at least 150 years. Since scientists started regularly observing the storm in 1850, they have noticed that the storm occasionally shrinks and grows. It is currently on a shrinking trend. What once was three times the size of Earth now only stretches to twice our planet’s diameter.
The four Galilean moons of Jupiter, Io, Europa, Ganymede, and Calisto, are among the largest and most studied moons in the Solar System. They were discovered by Galileo Galilei in 1610 and are the first objects found to orbit a planet other than Earth. Io is the most volcanically active world in the Solar System, hosting hundreds of volcanoes that are kept active by the gravitational interactions between Io, Jupiter, and the other Jovian moons. Europa is an icy world known to have a liquid ocean beneath its 20 kilometers-thick icy crust, which may contain twice as much as all of Earth’s oceans combined. This makes it a promising place to search for life, and this is exactly what upcoming missions will be doing. Callisto, the third largest moon in the Solar System, may be considered by some to be the lifeless, characterless member of the four Galilean moons. Ganymede is the largest moon in our solar system, even bigger than the planet Mercury and the dwarf planet Pluto. There’s strong evidence that Ganymede has an underground saltwater ocean that may hold more water than all the water on Earth’s surface. Ganymede is the only moon known to have its own magnetic field – something typically found on planets like Earth. The magnetic field causes auroras, bright ribbons of glowing gas, that circle the moon’s poles. Observing the Galilean moons is a thrilling experience. With a big enough telescope, you can witness transits of the moons passing Jupiter and spot their shadows cast on the gas giant’s surface. Truly, Jupiter is a majestic force of nature!
Saturn
Saturn is a celestial wonder. It’s the sixth planet from the Sun and the second largest planet in the Solar System at 9.6 astronomical units from the sun. Saturn has the lowest density of all the planets in our solar system. Its density is lesser than water and if you had a large enough pool of water, Saturn would float. Saturn’s most remarkable feature is its stunning ring system, visible from Earth with a telescope. These rings are made up of billions of icy and dusty particles, ranging in size from micrometers to a couple of meters, and are believed to be relatively young, having formed within the last 100 million years. The gravitational pull of Saturn’s moons constantly changes the rings, making them a captivating sight to behold. Saturn has 83 moons. Sixty-three moons are confirmed and named, and another 20 moons are awaiting confirmation.
Saturn’s largest moon, Titan, is an extraordinary and exceptional world. Titan is larger than the planet Mercury and is the second-largest moon in our solar system. Among all the solar system’s known moons, Titan is the only one with a substantial atmosphere. Titan’s atmosphere is made mostly of nitrogen, like Earth’s, but with a surface pressure 50 percent higher than Earth’s. And of all the places in the solar system, Titan is the only place besides Earth known to have liquids in the form of rivers, lakes, and seas on its surface. These are made out of liquid hydrocarbons like methane and ethane. Beneath Titan’s thick crust of water ice is an ocean. Titan’s subsurface water could be a place to harbor life as we know it, while its surface lakes and seas of liquid hydrocarbons could conceivably harbor life that uses different chemistry than we’re used to. Another compelling world is Saturn’s icy ocean moon Enceladus. A handful of worlds are thought to have liquid water oceans beneath their frozen shell, but Enceladus sprays its ocean out into space where a spacecraft can sample it. From these samples, scientists have determined that Enceladus has most of the chemical ingredients needed for life, and likely has hydrothermal vents spewing out hot, mineral-rich water into its ocean. Another interesting feature is Saturn’s’ hexagonal storm, which is a large, rotating storm system located at the planet’s north pole. The storm is estimated to be about 20 thousand kilometers across and is believed to have been present for at least 150 years. The hexagonal shape of the storm is believed to be caused by the planet’s high-speed jet streams.
Uranus
Uranus is an incredible celestial body, about 20 astronomical units away from the Sun. It is the seventh planet from the Sun and the third largest in the Solar System. One day on Uranus takes about 17 hours, and Uranus makes a complete orbit around the Sun in about 84 Earth years. Uranus is the only planet whose equator is nearly at a right angle to its orbit, with a tilt of nearly 98 degrees. This is possibly the result of a collision with an Earth-sized object long ago. This unique tilt causes the most extreme seasons in the solar system. For nearly a quarter of each Uranian year, the Sun shines directly over each pole, plunging the other half of the planet into a 21-year-long, dark winter. Uranus has an impressive 27 known moons and a faint, barely visible ring system made up of nine continuous and three discontinuous rings.
Neptune
Far from the warmth of the Sun, Neptune reigns as the most distant planet in our Solar System. Its winds are the strongest of any planet, whipping clouds of frozen methane across the planet at speeds up to an incredible 2100 kilometers per hour! With 14 known moons, the largest of which is Triton, Neptune’s atmosphere is a beautiful blue hue, thanks to the presence of methane in its atmosphere. Triton is the largest moon of Neptune and one of the most geologically active bodies in the Solar System, together with Venus and Jupiter’s moon Io. It has a very thin atmosphere composed mostly of nitrogen and is the coldest known planetary body in the Solar System, with temperatures as low as -235°C. Its surface is covered in a variety of features, including mountains, valleys, and craters. Triton is believed to have a subsurface ocean of liquid water. The probability of life existing within the depths of Triton’s ocean is much smaller than for Europa, but it can’t be completely ruled out.
Asteroid belt, Kuiper belt, and Oort cloud
The asteroid belt is an incredible cosmic playground, located between the orbits of Mars and Jupiter. It is estimated to contain an astonishing 1 to 2 million asteroids, ranging in size from a few meters to hundreds of kilometers in diameter. Not only is the asteroid belt home to countless asteroids, but it also contains several dwarf planets, including Ceres, Vesta, and Pallas. The largest one, the mighty Ceres, is a whopping 950 kilometers in diameter! Beyond the orbit of Neptune lies the mysterious Kuiper Belt! This region of the Solar System is a treasure trove of icy bodies, including comets, asteroids, and dwarf planets. It is estimated that the Kuiper Belt contains over 100000 objects larger than 100 kilometers in diameter and is believed to be the source of many short-period comets, including Halley’s Comet. Among the dwarf planets in the Kuiper Belt are Pluto, Eris, Makemake, and Haumea. Beyond the Kuiper belt, deep in the depths of our Solar System, lies a mysterious cloud of icy objects known as the Oort Cloud. This vast expanse of icy bodies is believed to contain up to two trillion objects, ranging from small comets to large planetesimals. It is thought to be the source of most of the long-period comets that enter the inner Solar System and is believed to be composed of icy objects left over from the formation of the Solar System. The Oort Cloud is so distant that it is impossible to observe directly, but its presence can be inferred from the behavior of long-period comets.
The awe-inspiring beauty of our solar system is unparalleled. It is the only known place in the universe where life is known to exist, and it houses some of the most remarkable celestial bodies. It is truly a special place to call home!
Very interesting. Will take me some time to absorb all this knowledge. Thanks for being so informative.