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Our Home, the Solar System
The Sun is just an average, yellow star in the Milky Way, but from the point of view of earthly life it is the most significant star: it is the centre of the Solar System around which Earth orbits.
The Sun accounts for 99.87% of the Solar System’s mass, and exerts a massive gravitational force. This gravitational force holds the system together, and determines the motion of the 8 planets and of the other smaller celestial bodies (at least 173 known moons,
6 identified dwarf planets, 500,000 asteroids
and more than 5,000 known comets).
The Solar System’s gravitational
boundary extends approx.
1 light-year away from the Sun.
The Sun and the eight planets
The Sun, the central star in the Solar System, is the only celestial body in it capable of generating energy that results in light emission. Its strong gravity determines how the entire Solar System works.
Neptune: The outermost planet of the Solar System. It is the fourth-largest planet in terms of volume and the third-largest planet in terms of mass. It has 14 known moons.
Mars: The fourth planet from the Sun in the Solar System. Due to its colour, it is also called the red planet. It has two moons.
Jupiter: The largest planet in the Solar System.
Its volume is more than 1300 times larger, and its mass 318 times larger than that of the Earth.
It has 79 moons.
Saturn: The second largest planet in the Solar System after Jupiter. It has a spectacular ring system and 62 known moons.
Uranus: It is the 7th planet from the Sun and the fourth-largest planet in terms of mass. It has 27 known moons.
Mercury: The closest planet to the Sun. It has an orbital period of only 88 Earth days. It does not have any moons.
Venus: The closest planet to Earth. It is the third brightest celestial body in the sky, after the Sun and the Moon. It has no moons.
The Earth: The third planet from the Sun in the Solar System. Its only natural satellite is the Moon.
Did you know?
Pluto ‘downgraded’
Astronomers previously considered Pluto as the ninth, smallest planet of the Solar System. However today it is no longer classified as a planet, as several larger celestial bodies were discovered which also had many similar characteristics that differed from those of planets. Astronomers therefore reformulated the definition of the term ‘planet’ and classified Pluto as a dwarf planet.
Neither a planet nor a moon
Dwarf planets are smaller than planets, but larger than aster-
oids. Along with Pluto, the currently known dwarf planets
of the Solar System are Ceres, Haumea, Makemake and Eris.
Our Solar System
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