Interesting Facts About the Solar System

In the Solar System, the hottest planet is not the one closest to the Sun, and Pluto is only about half the width of the United States.

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1. Mercury is closest to the Sun, but the “hottest” planet is Venus

Venus has an atmosphere that is 100 times denser than Earth’s, primarily composed of CO2. The average temperature here is about 468 degrees Celsius, hot enough to melt tin and lead.

2. Pluto has a diameter of only about 2,200 km

This size is less than half the width of the United States and is much smaller than any other large planet. It is no longer considered an official planet.

3. The only asteroid belt known to scientists exists between Mars and Jupiter

There are tens of thousands of asteroids orbiting between them, but they are spaced far apart with little chance of collision. This is quite different from what we see in science fiction films, where spacecraft constantly risk colliding with asteroids.

The Solar System. (Photo: NASA/JPL).

4. Most elements on Earth are rare elements

The basic composition of Earth primarily consists of iron, oxygen, silicon, magnesium, sulfur, nickel, calcium, sodium, and aluminum. However, compared to the universe, they are merely “trace elements” because of the much greater abundance of hydrogen and helium in the universe.

5. Some meteorites originate from Mars

Chemical analysis of many meteorites found in Antarctica and the Sahara Desert shows that they originate from Mars. Larger meteorite impacts can blast them off to Earth.

6. Jupiter has the largest ocean of all planets

The planet is more than five times farther from the Sun than Earth and is primarily composed of hydrogen and helium. Hydrogen on Jupiter exists in liquid form, creating a “planetary ocean” that is 40,000 km deep.

7. The outer atmosphere of the Sun extends at least 100 AU, nearly 16 billion km

The outer atmosphere of the Sun extends far beyond its visible surface, and Earth’s orbit lies within this thin atmosphere.

8. Even very small asteroids can have moons

It was once thought that only large objects like planets could have satellites or natural moons. In fact, the existence of moons, or a planet’s ability to gravitationally capture a moon in orbit, is sometimes used as part of the definition of what a true planet is. It seems unreasonable for smaller celestial bodies to have enough gravitational force to hold a moon. After all, Mercury and Venus have none, and Mars only has small moons. However, in 1993, the Galileo spacecraft passed by the 20-mile-wide asteroid Ida and discovered its one-mile-wide moon, Dactyl. Since then, moons have been discovered orbiting many other smaller planets in our solar system.

9. The edge of the solar system is over 1,000 times farther than Pluto

You might still think of the solar system as an extension of the orbit of the beloved dwarf planet Pluto. Today, we don’t even consider Pluto an official planet. However, we have discovered many objects orbiting the Sun that are much farther than Pluto.

These are known as Trans-Neptunian Objects (TNO) or Kuiper Belt Objects (KBO). The Kuiper Belt, the first of two regions containing material from the Sun, is thought to extend to 50 or 60 astronomical units (AU, or the average distance from Earth to the Sun). Another part, even farther out in the solar system, is the vast yet fragile Oort Cloud, which may extend up to 50,000 AU from the Sun, or about half a light year – over 1,000 times farther than Pluto.

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