How are the planets in the solar system classified?

The planets in the solar system are classified based on their physical characteristics and their position relative to the sun. There are two main types of planets in the solar system: terrestrial planets and gas giant planets.

The terrestrial planets, also known as rocky planets, are Mercury, Venus, Earth, and Mars. These planets are smaller, have rocky surfaces, and are closer to the sun.

The gas giant planets, also known as Jovian planets, are Jupiter, Saturn, Uranus, and Neptune. These planets are larger, have thick atmospheres made up mostly of hydrogen and helium, and are located farther from the sun.

Pluto, formerly classified as a planet, is now considered a dwarf planet, as it does not meet the criteria for a full-fledged planet.

There are many ways to classify the planets in our solar system. Here are a few common ways:

• By size: The planets can be divided into two groups based on their size: terrestrial planets and gas giants. Terrestrial planets are smaller and have a rocky surface, while gas giants are larger and have a gaseous surface. The terrestrial planets are Mercury, Venus, Earth, and Mars. The gas giants are Jupiter, Saturn, Uranus, and Neptune.
• By location: The planets can also be divided into two groups based on their location in the solar system: inner planets and outer planets. Inner planets are closer to the sun than the asteroid belt, while outer planets are farther away from the sun than the asteroid belt. The inner planets are Mercury, Venus, Earth, and Mars. The outer planets are Jupiter, Saturn, Uranus, and Neptune.
• By composition: The planets can also be divided into two groups based on their composition: rocky planets and icy planets. Rocky planets are made mostly of rock and metal, while icy planets are made mostly of ice and gas. The rocky planets are Mercury, Venus, Earth, and Mars. The icy planets are Jupiter, Saturn, Uranus, and Neptune.

In addition to these common ways of classifying the planets, there are many other ways to classify them. For example, planets can be classified by their atmosphere, their moons, or their rings.

The definition of a planet has changed over time. In the past, any object that orbited the sun was considered a planet. However, in 2006, the International Astronomical Union (IAU) redefined the term "planet." Under the new definition, a planet must meet three criteria:

1. It must orbit the sun.
2. It must be large enough for its own gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
3. It must have cleared the neighbourhood around its orbit.

Under this new definition, Pluto is no longer considered a planet. It is now classified as a dwarf planet.