The solar system contains eight planets: Neptune, Uranus, Jupiter, Saturn, Mars, Venus, Earth, and Saturn Terrestrial planets include Mercury, Venus, Earth, and Mars, which are the four inner solar system planets. Uranus and Neptune are ice giants, containing primarily elements heavier than hydrogen and helium, whereas Jupiter and Saturn are gas giants (giant plants).
When Clyde Tombaugh discovered Pluto for the first time, it was regarded as one of the planets in the solar system. Pluto is a dwarf planet. However, it is now thought to be one of the largest known members of the Kuiper Belt, a group of icy bodies near the solar system’s outer edges. In 2006, a group of scientists agreed on a formalized definition for the term “planet,” which resulted in Pluto losing its status as a planet.
A planet is “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit,” as defined by the International Astronomical Union. Pluto is no longer considered a planet because it is located in the Kuiper Belt and does not satisfy the third requirement. It is instead categorized as a dwarf planet. Other bantam planets incorporate Ceres, Haumea, Makemake, and Eris.
Pluto is the most complex dwarf planet we know about and one of the most surprising planets in the solar system. It has an atmosphere, stark surface features, and at least five moons. In July 2015, the spacecraft New Horizons passed by our favorite dwarf planet, and scientists continue to discover surprising information about this faraway world.
Additional Queries Concerning the Solar System:
- Which planets in our solar system are the largest and smallest?
- Why do the gas-giant outer planets rotate more quickly than the terrestrial inner planets?
- What is a comet and where did it originate?
- What are space rocks and where do they come from?
Track down additional responses to your inquiries in Sky and Telescope’s Cosmology back and forth discussions.
Available now: Using imagery from New Horizons, a 6-inch Pluto globe was created!