Our solar system is the group of planets, moons and other space debris circling our Sun. There are also at least 120 moons circling the planets, and millions of asteroids in a belt between Mars and Jupiter. At the outer edge of the Solar system, far beyond the orbit of distant Pluto, is a halo of icy comets called the Oort cloud.

Our solar system is the group of planets, moons and other space debris circling our Sun. There are also at least 120 moons circling the planets, and millions of asteroids in a belt between Mars and Jupiter. At the outer edge of the Solar system, far beyond the orbit of distant Pluto, is a halo of icy comets called the Oort cloud.

© Canadian Heritage Information Network, 2003

Solar System

The Sun is at the centre of our solar system. The four inner planets are Mercury, Venus, Earth and Mars. The five outer planets are Jupiter, Saturn, Uranus, Neptune and Pluto.

Planétarium de Montréal

© Planétarium de Montréal


Asteroid

Some asteroids come close to Earth's orbit, although astronomers don't know of any that pose an immediate threat to the Earth. By studying asteroids, astronomers hope to find a way to counteract any that come too close for comfort in the future.

NASA / JPL

© NASA / JPL


The Sun is a star, just like the stars we see at night. The Sun is much closer to us than the other stars, so it appears much bigger and brighter. The Sun’s visible disk is called the photosphere. Surrounding the photosphere is a thin layer called the chromosphere, which is only seen during a total solar eclipse. The outer atmosphere of the Sun is called the corona.

Eclipses of the sun inspire creative works and cultural rituals. One rock-climbing performance group from Canada performed a piece during the solar eclipse of May 1994.

The basics

Period of revolution (around centre of galaxy): 220 000 000 years
Period of rotation 27 days on average
Diameter: 1 392 000 km
Surface gravity: 27.9 times greater than Earth’s
Composition: 75% hydrogen, 25% helium, with traces of heavier elements
Temperature: 5 500 degrees Celsius at surface; 15 000 000 degrees Celsius at core

Appearance in Earth’s sky

The Sun appears as a blindingly bright disk of light. In fact, the Sun is bright enough to cause serious eye damage, so it’s important never to look at it di Read More
The Sun is a star, just like the stars we see at night. The Sun is much closer to us than the other stars, so it appears much bigger and brighter. The Sun’s visible disk is called the photosphere. Surrounding the photosphere is a thin layer called the chromosphere, which is only seen during a total solar eclipse. The outer atmosphere of the Sun is called the corona.

Eclipses of the sun inspire creative works and cultural rituals. One rock-climbing performance group from Canada performed a piece during the solar eclipse of May 1994.

The basics

Period of revolution (around centre of galaxy): 220 000 000 years
Period of rotation 27 days on average
Diameter: 1 392 000 km
Surface gravity: 27.9 times greater than Earth’s
Composition: 75% hydrogen, 25% helium, with traces of heavier elements
Temperature: 5 500 degrees Celsius at surface; 15 000 000 degrees Celsius at core

Appearance in Earth’s sky

The Sun appears as a blindingly bright disk of light. In fact, the Sun is bright enough to cause serious eye damage, so it’s important never to look at it directly. When the Sun is in the sky, the atmosphere of the Earth scatters the blue component of the Sun’s light, turning the sky blue. This blue sky is bright enough that we cannot see the other stars in the sky. (The stars are still there, however, and can be seen in the daytime during a solar eclipse.)

Telescopic appearance

WARNING! NEVER LOOK DIRECTLY AT THE SUN!
The Sun is so bright that looking at it through a telescope for even an instant can cause permanent blindness. The best way to observe the Sun is by using a pinhole camera or another indirect viewing method. The most obvious features of the solar disk are sunspots. These are cooler regions of the Sun’s surface and are sometimes visible as dark spots. The Sun rotates relatively slowly, once every 27 days.

© Canadian Heritage Information Network 2003

The Sun

The Sun is a star, just like the stars we see at night. The Sun is much closer to us than the other stars, so it appears much bigger and brighter.

NASA / Extreme UV Imaging Consortium

© NASA / Extreme UV Imaging Consortium


Learning Objectives

The learner will:

  • Define solar system
  • Recognize that the Sun is a star
  • Describe the basic features of the Sun

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