Exploring the Sun, planets, Moon and stars
The Solar System consists of the Sun and everything that orbits it: eight planets, their moons, dwarf planets, asteroids and comets. In order from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. The four inner planets are rocky, while the outer four are giant planets made mostly of gas and ice. Venus is the hottest planet and Jupiter is the largest. Satellites are bodies that orbit a planet; the Moon is Earth’s natural satellite.
The Moon does not produce light; we see it because it reflects sunlight. As it orbits Earth in about 29.5 days, we see changing phases from new moon to full moon. A solar eclipse happens when the Moon comes between the Sun and Earth, and a lunar eclipse when Earth’s shadow falls on the Moon. Stars are huge glowing balls of gas very far away. Groups that form patterns, such as Ursa Major (Saptarishi) and Orion, are constellations, and the Pole Star helps find north.
Why it matters
Astronomy helps us understand days, months, seasons and calendars, and it guided travellers before compasses existed. Artificial satellites in Earth orbit provide weather forecasts, television and navigation. Space missions by ISRO, such as Chandrayaan and Mangalyaan, have explored the Moon and Mars. This topic builds curiosity for gravitation and space science in later classes.
Key terms
- Planet
- A large body that orbits a star and has cleared its orbit of other objects.
- Phases of the Moon
- The changing shapes of the lit part of the Moon seen from Earth during a month.
- Constellation
- A group of stars that appears to form a recognisable pattern in the night sky.
- Eclipse
- An event in which one celestial body moves into the shadow of another.