The oldest branch of science is astronomy. Human beings always have the curiosity to solve the mystery of the universe. Those who study the universe are known as astronomers. Earlier astronomers used to think that earth was at the center and the whole universe moved around the Earth. Now we can understand how narrow the understanding of the Universe earlier astrologers had. However, better ideas started to grow with the passage of time.
In 1543, A Polish priest named Nicholas Copernicus published a theory that tells that it is the Sun that is at the center. It means that all the planets are to move around the Sun, and not the Earth. Earth is one of the eight planets in our solar system.
In 1929, Hubble using the largest telescope proved that the Universe is expanding as galaxies and suns are moving away from one another due to the Big Bang explosion.
We ordinary people can also watch stars at night by using binoculars or a mini telescope. However, scientific observations cannot get benefit from these instruments. They are to use an observatory that is situated on a mountain because this observatory has many telescopes as well as other instruments necessary for carrying out scientific research efficiently.
Observatories are set up on mountain tops so that they can collect the starlight before the atmosphere of the earth distorts the light.
People have been tracking stars for thousands of years. They used to group the stars to make their tracking easier. These groups are called constellations. These groups were also given names after legendary or mythical characters. People also used the names of animals for some groups whose shapes look like some animals.
Do you know why sometimes a star twinkle? It twinkles because the light of the star has to be bent and broken when it passes through the atmosphere. Sometimes, the star is to flicker because it has to pass through both cold and warm air.
If you look up at the sky, you will see that the stars move from one place to another. But have you ever noticed a star that does not move from its position? The name of this star is the pole star. Travelers have been using this star for finding directions.
Like us, a star has to die after a few billion years. The age of our star is 5 billion years. It is a main sequence star, and it is a middle-aged star. After a few billion years, it will become old and die. So, a star has a life cycle.
A star is born when a nuclear reaction begins out of the shrinkage of the dust particle and a cloud of gases into a ball. This nuclear reaction leads to a rise in temperature. This rise in temperature begins to glow as a star. When the star reaches its middle age, it begins to expand and appears as a red giant. Finally, the star begins to shrink in response to its own gravitational pull and appears as a white dwarf. The white dwarf ends its life in a black dwarf. However, a big star ends its life in an explosion as a supernova. A massive star can last only a few hundred thousand years because it uses its fuel more quickly. On the other hand, a small star can live several billion years as it uses its fuel very slowly.
Our sun is also a star. It is a main sequence star. It is now in its middle age. It appears big to us because it is very near to us. As a result, we get light and warmth from it. This warmth and light are the ultimate sources of life on earth. Though there are many other stars that are larger than our sun, we do not get light and heat from them because they are very far from us. You should keep in mind that the Sun is not uniformly hot. Some parts are less hot, and these parts look dark. These dark patches are known as sunspots.
There are eight planets that are constantly revolving around the Sun because the Sun's strong gravitational pull keeps all the planets and heavenly bodies rotating in their respective orbits around the Sun.
The closest planet to the Sun is Mercury. Mercury moves so fast that it takes only 88 days to revolve around the Sun. So, there are only 88 days in a year of Mercury. Mercury's ground looks like the ground of the Moon because its ground is full of craters. The atmosphere of Mercury is very thin because it is very close to the Sun. As this thin atmosphere cannot pull the warmth towards the surface, it is too cold at night. The only space probe through which we know about Mercury is Mariner 10.
On the basis of distance, Venus is the second planet. In our sky, it is the brightest object after the moon. Though it is the second planet away from the Sun, it is the hottest planet in our solar because the gases of Venus do not let the heat escape into Space. Therefore, the temperature of Venus is 490°C which can cause volcanic eruption on its surface. As the orbit of Venus lies in between the Earth and the Sun, we can only see before sunrise or after sunset. We can Venus our morning or evening star because it is the brightest object in the night sky after our natural satellite the Moon.
Earth is the third planet away from the Sun. The distance of the Earth from the Sun has made the planet ideal and unique. It is unique because it is the only planet that has life. It is the only planet that has the required amount of oxygen necessary for living creatures. Its temperature can keep water in its liquid condition. The existence of oxygen and water has enabled the evolution of different kinds of living creatures. The atmosphere of the sun is thin enough to allow Sun rays through it and thick enough to block ultraviolet rays.
The next planet is Mars. It is the smallest planet after Mercury. As Mars has an iron-rich surface, it makes the planet look red. People talk highly about Mars. In fact, NASA, Spacex, and other organizations around the world are planning to send humans to Mars. But Mars is not located at the right distance. As a result, it is too cold to sustain life. Moreover, the planet's gravity is only 38% of the gravity of the Earth. Furthermore, there is too much carbon dioxide in the atmosphere of Mars. As Mars is very close to the Earth, reaching March would be easier for scientists. Therefore, scientists are planning to create environmental conditions on Mars's surface.
After Mars, we have Jupiter, the biggest planet, in the solar system. It is 13000 times bigger than the Earth. Jupiter's atmosphere consists of multi-colored gases that whirl at the rate of up to 650 kilometers per hour. Winds whip up at high speed in Jupiter because of its speedy rotation on its axis. Life cannot exist on Jupiter because of unsuitable temperatures, high gravitational pull, and unsuitable gasses.
The second largest planet is Saturn. Its mass is 95 times that of Earth. However, Saturn's average density is lighter than the same volume of water. It means that if Saturn is put in a large water body, it will float. Saturn just consists of gasses, and it has no solid surface to land on. Moreover, it is about 1.2 billion kilometers (746 million miles) away from the earth; it is the furthest planet from the Earth. Furthermore, its gravity is too low. Saturn is considered the most beautiful planet because of its surrounding colorful rings. These rings consist of thousands of ringlets. Each ringlet consists of dust particles and chunks of rocks and ice. Saturn has the greatest number of satellites. Titan is the largest one.
Uranus lies in the middle between Saturn and Neptune. So, it is the farthest planet after Neptune away from the Sun. It is so far away from the Sun that it takes 84 years to revolve around the Sun. Though Uranus is much smaller than Saturn and Jupiter, it is 15 times bigger than Earth. Uranus is too cold because it is too far from the Sun. Its temperature is -224° Celsius or -371° Fahrenheit. Its atmosphere consists of hydrogen and helium.
Neptune is the last planet away from the Sun. We cannot see Neptune through our naked eyes because it is so far away from us. Neptune is as big as Uranus. As it is very far from the Sun, it is too cold. Its temperature is about -400° Celsius. it takes 165 years to move around the Sun. Its atmosphere consists of hydrogen, helium, and methane. As methane absorbs red light and reflects blue light, it looks blue.
Once Pluto was a planet. But the International Astronomical Union (IAU) discarded Pluto from the status of a planet. Though Pluto has its own orbit around the Sun, and it has almost a round shape, Pluto has "cleared the neighborhood" around its orbit. It is so far that no probe has been able to visit it. So, we have known very little about Pluto. It takes 248 Earth years to revolve around the Sun.
Besides planets, there are asteroids, comets, and meteors in a solar system. An asteroid is called a small planet though they do not have a round-like shape. Scientists recognize them as the 'debris' of the Big Bang because they could not become planets during the formation of the Solar System. Almost 90% of asteroids are found between the orbit of Jupiter and Mars, known as the asteroid belt.
Comets consist of massive masses of rock, dust, and ice floating in space. Comets also have a fixed orbit, and they too move around the Sun.
Meteors are fallen chunks of rock from a comet. Sometimes, comets come close to the Earth, and the chunks of rock that are associated with the comet break off due to Earth's gravity and fall down to the earth.
Eckermann, Alex. Observatories on the Summit of Mauna Kea, Hawaii., 5 Apr. 2020, unsplash.com/photos/eLjFKlrv3iU. Accessed 3 Oct. 2022.
Shuo, Yang. “Editorial, Architecture, Wallpapers,” Unsplash.com, 21 Oct. 2020, unsplash.com/photos/b8nZU0GYsrg. Accessed 3 Oct. 2022.
Solar System Planets Planetary System Orbit Sun. pixabay.com/illustrations/solar-system-planets-11111/. Accessed 3 Oct. 2022.
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