The Solar System

Location of Solar System

A galaxy contains a large group of stars, gas, and dust bound together by gravity. The Milky Way is a large barred spiral galaxy that contains our Solar System in one of its four spiral arms. The Solar System goes around the center of the Milky Way every 250 million years. Our Solar System is about 25,000 light-years away from the center of this galaxy. The stars that we see at night belong to Milky Way.

Planets

A planet is an astronomical body moving in an elliptical orbit around a star. They are massive, rounded, and spherical in the structure under the influence of their own gravitational force. There are about 8 planets in our solar system. Earth is the only habitable planet known. These planets are divided into two categories:

1. TERRESTRIALS: Planets like Mercury, Venus, Earth and Mars are terrestrials and are closer to the sun. They are primarily composed of rock and metal.
2. GIANT PLANETS: They are massive planets and include Jupiter, Saturn, Uranus and Neptune. Jupiter and Saturn are the most massive and are known as gas giants. They are composed mainly of hydrogen and helium. Neptune and Uranus are called ice giants. They have icy cores and are composed of substances with high melting points like water, ammonia and methane.

Dwarf Planets

These are worlds that are too small to be considered full-fledged planets, but too large to fall under smaller categories. Astronomers estimate that there could be as many as 200 dwarf planets in the Solar System. The confirmed names are Ceres, Pluto, Eris, Haumea and Makemake. Pluto which was earlier considered a planet has been given the status of a dwarf planet now, but the controversy still exists. The following picture depicts their sizes as compared to Mercury.

Moons

Moons, also known as natural satellites orbit around planets and asteroids. There are around 205 known moons in our solar system. Most orbit the giant planets –Saturn and Jupiter, but even smaller worlds like Pluto have moons orbiting it. They come in various shapes and sizes with some of them having atmospheres and hidden oceans. They are mostly made of rocks and some are made of ice.

The Earth-Moon relationship is a special one. It makes our planet more livable by giving us stable climatic conditions. It takes 27.3 days to orbit around the Earth.

              Some of the Moons around Jupiter

Comets

Described as ‘dirty snowballs’, comets are made up of frozen gases, rocks and dust left over during the formation of the Solar System. They usually orbit around the Sun in elongated paths.  As the comet gets close to the Sun, some of the ice melts and boils along with particles of dust forming a giant glowing head with a trail of debris behind it made of dust and gases. Comet Halley is a famous comet visible to the naked eye every 75-76 years.

All these objects orbit around the Sun in a direction in which the Sun rotates. They move in a counterclockwise direction when viewed from top. Besides them, there is an interplanetary medium made up of highly tenuous gases and dust that make up the Solar System.

Check Point

1. There are __________ planets in the Solar System.
2. The Solar System belongs to a galaxy called _____________.
3. _______________ are also known as minor planets.
4. Comet ___________ appears in the Earth’s sky every 75-76 years.
5. When _____________ enter the Earth’s atmosphere, they illuminate and form meteors or

     shooting stars.

6. __________ is the star present at the center of the Solar System.

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Image Credits

1. https://msutoday.msu.edu/news/2016/astronomers-pinpoint-how-milky-way-galaxy-was-formed/

2.https://my.vanderbilt.edu/astro201solarsys/page/164/?wordfence_logHuman=1&hid=1BD0B6093844F3967615838D5B4E59FA

3. https://rsc.byu.edu/vol-3-no-2-2002/our-creators-cosmos
4. http://www.seasky.org/solar-system/solar-system.html
5. https://scied.ucar.edu/sun-regions
6. https://socratic.org/questions/what-are-some-non-major-dwarf-planets

7.https://www.perkinselearning.org/accessible-science/activities/earth-and-moon-student-built-model

8. https://earthsky.org/astronomy-essentials/how-to-see-jupiters-moons
9. https://nineplanets.org/asteroid-belt/
10. http://www.pas.rochester.edu/~blackman/ast104/halley.html

11.http://www.oecd.org/pisa/PISA2015Questions/platform/index.html?user=&domain=SCI&unit=S641-MeteoroidsAndCraters&lang=eng-ZZZ