What I learned
❖ The Universe is a vast and complex place. It is made up of a vast number of material objects such as stars, galaxies, planets, comets, asteroids, dust and gas. It also consists of immaterial substances such as light, radio waves, gamma rays and cosmic rays. It is the whole that contains all that exists.
The Universe began to form about 13.8 billion years ago and has been evolving and changing its structure ever since. The universe is incredibly large and it is impossible to determine its exact size as it is constantly expanding and evolving. Galaxies are born, die and collide, stars form and burn out, and new planets are born from the remains of old ones.
❖ The central and largest body in the Solar System is the Sun. Eight planets of the Solar System orbit the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune (Pluto is considered a dwarf planet and although it orbits the Sun, it is not a planet of the Solar System).
❖ In addition to the planets, a large number of smaller bodies called asteroids orbit the Sun.
❖ Moons orbit most of the larger planets. Jupiter (14), Saturn (23), and Uranus have the largest number of moons. Mercury and Venus have no moons.
❖ Other interesting bodies in the Solar System are the comets. They orbit the Sun on very elongated ellipses. The best known is Halley’s Comet with an orbital period of 75-76 years. It last passed Earth in 1986. We are reminded of the vastness of the cosmos by this amazing cosmic occurrence.
❖ The meteoroid is a relatively small piece of debris in the Solar System. Its size ranges from a grain of sand to the size of a large boulder or rock. When a meteoroid enters the Earth’s atmosphere, there is a light phenomenon and subsequent ionization of the air particles. This phenomenon is called a meteor or shooting star. We believe that if we make a wish when we observe a shooting star, it will come true.
❖ If any part of the meteoroid stays on the Earth’s surface, it is called a meteorite.
