Myths: Solar System

Solar system

1. The Earth is the largest object in the solar system.

The largest object in the solar system is the Sun. It contains 99 percent of the mass of the solar system. Jupiter is the largest planet in the solar system, and Earth is the fifth-largest.

2. The Earth is the center of the solar system.

The Sun is at the center of the solar system, and the planets, asteroids, moons, and comets orbit the Sun. The Earth is the third planet from the Sun.

3. Earth and Venus are identical.

Earth and Venus have a couple of things in common: they are rocky planets and are about the same size. But Venus is different in many ways from Earth. Venus has a harsh environment, is very hot, and has a poisonous atmosphere with “acid clouds.”

4. Earth and Mars are similar in size.

Mars is about half the size of Earth.

5. All the planets are the same size as Earth.

The planets are different sizes. From smallest to largest they are: Mercury, Mars, Venus, Earth, Neptune, Uranus, Saturn and Jupiter. Jupiter is roughly 10 times larger than Earth. Mars is about half the size of Earth. Venus and Earth are roughly the same size.

6. The Sun is not a star because it doesn’t shine at night.

The Sun is the closest star to Earth and provides us with most of our energy and light. Earth turns on its axis once every day. When we experience darkness, we are facing away from the Sun. When we experience daylight, we are facing the Sun. We can’t see other stars during the day because the Sun’s light illuminates Earth’s atmosphere.

7. The Sun is a burning ball of fire.

The Sun is glowing, not burning like a fire. The Sun glows because its temperature is about 5,500 degrees Celsius (about 10,000 degrees Fahrenheit). This heat is not produced by burning (a chemical reaction), but rather by fusion (a nuclear reaction). This nuclear fusion takes place deep in the Sun’s core at a temperature of about 15 million degrees. As the heat travels out through the Sun’s layers, it becomes much cooler, but still hot enough to glow in visible light. For comparison, the temperature of a wood fire is less than a thousand degrees Fahrenheit.

8. Spacecraft can land on the surfaces of Jupiter, Saturn, Uranus, and Neptune.

These giant planets are made mostly of gas. They may have solid cores, but the temperature and pressure of the gas would increase as the spacecraft moved toward the core. It would be destroyed before it reached that solid surface.

9. The rings of Saturn are solid disks.

Thousands of rings, made of pieces of ice, orbit the planet. The pieces of ice are about one meter apart, and can be as small as dust specks or as big as a house. The ice pieces collect into ring shapes because of gravity. The rings are usually divided into seven regions, labeled A to G. The total mass of the rings is that of a 100-kilometer-sized comet.

10. Pluto is the most-distant and last object in the solar system.

No, Pluto is not the last object in the solar system. Pluto resides within a region of icy objects called the Kuiper Belt. The Kuiper Belt extends from Neptune’s orbit outward. Beyond Pluto's orbit is another vast region of icy objects called the Oort Cloud, which, like the Kuiper Belt, is a home to comets.

11. The planets are evenly spaced between the Sun and Neptune.

The inner planets (Mercury, Venus, Earth and Mars) are closer together than the outer ones (Jupiter, Saturn, Uranus, and Neptune). The inner planets are closest to the Sun; the outer planets are farthest away from the Sun. The distance between planets generally increases as one looks farther from the Sun. The planets in the inner solar system are tens of millions of kilometers apart; the planets in the outer solar system are hundreds of millions of kilometers apart.

12. The solar system is made up of only the Sun and eight planets.

The solar system also contains the planets' moons, scattered gas and dust, asteroids, and comets. Comets occasionally visit the inner solar system — the region closest to the Sun — from their home in the Kuiper Belt or Oort Cloud.

13. Comets are composed of the same material as asteroids.

Although comets and asteroids are both tiny objects that orbit in the solar system, their composition differs. Asteroids are mostly rock with some ice, while comets are mostly ice with some rock.

14. Comets always have tails.

Comets do not always have tails. They develop a fuzzy, shell-like cloud called a coma, and one, two, or three tails when near the Sun. Comets have no coma or tail when far away from the Sun.

15. Comets come from regions outside the solar system.

Comets are part of the solar system. Scientists believe they come from one of two locations within the solar system: the Kuiper Belt and the Oort Cloud. The comets that we see often – every 100 years – come from the Kuiper Belt, and comets that we see rarely – every few thousand years – come from the Oort Cloud.

16. Meteors are falling stars.

Meteors are the bright flashes of light seen in the night sky. They are caused by meteoroids, small, solid objects moving through space that have entered Earth’s atmosphere. Usually, the meteoroids burn up in the atmosphere and never reach the ground. A meteorite is the chunk of material that does reach the ground.

17. Meteors are solid objects.

A meteor is a bright streak of light in the sky caused when a meteoroid (a small chunk of rock or ice) enters the Earth’s atmosphere and heats up.

18. Asteroids are very close to each other.

Asteroids are not close to each other. They are roughly 1 million miles from each other.

19. Other stars and galaxies are part of the solar system.

There is only one star, the Sun, in the solar system. Besides the Sun, the solar system consists of planets, moons, asteroids, and comets. The solar system resides in the Milky Way galaxy. Many other stars are outside our solar system, but part of our Milky Way galaxy. About 50 billion galaxies are outside our galaxy. Galaxies contain from tens of millions to trillions of stars.

20. Scientists know all there is to know about the solar system.

Scientists are sending out spacecraft and pointing telescopes to learn more about the solar system. Among the many questions scientists are trying to answer are whether Mars has liquid water and how the solar system was formed.

Myths: Solar System