In July 1994, the fragments of Comet Shoemaker-Levy collided with Jupiter, producing the largest explosions ever observed in our solar system. The fragments left behind dark patches in the clouds of Jupiter, allowing astronomers to observe the way Jupiter’s atmosphere works.

Jupiter rotates on its axis every 9 hours and 55 minutes.

In December 1995, the Galileo spacecraft went into orbit around Jupiter and began returning close-up images of Jupiter’s atmosphere and moons.

The basics

Order (outwards from the Sun): 5
Average distance from the Sun: 778 300 000 km (5.20 astronomical units)
Period of revolution (length of year): 11.86 years
Period of rotation (length of day): 9 hours 55 minutes at the equator
Diameter: 142 980 km at the equator
Surface gravity: 2.54 times greater than Earth’s
Composition: Scientists do not agree on whether Jupiter has a solid rocky core or if it consists only of gases that condense in the middle to form liquids. The interior ocean is made primarily of hydrogen and helium, with a few other gases
Atmosphere: Hydrogen, helium, some me Read More

In July 1994, the fragments of Comet Shoemaker-Levy collided with Jupiter, producing the largest explosions ever observed in our solar system. The fragments left behind dark patches in the clouds of Jupiter, allowing astronomers to observe the way Jupiter’s atmosphere works.

Jupiter rotates on its axis every 9 hours and 55 minutes.

In December 1995, the Galileo spacecraft went into orbit around Jupiter and began returning close-up images of Jupiter’s atmosphere and moons.

The basics

Order (outwards from the Sun): 5
Average distance from the Sun: 778 300 000 km (5.20 astronomical units)
Period of revolution (length of year): 11.86 years
Period of rotation (length of day): 9 hours 55 minutes at the equator
Diameter: 142 980 km at the equator
Surface gravity: 2.54 times greater than Earth’s
Composition: Scientists do not agree on whether Jupiter has a solid rocky core or if it consists only of gases that condense in the middle to form liquids. The interior ocean is made primarily of hydrogen and helium, with a few other gases
Atmosphere: Hydrogen, helium, some methane and ammonia
Satellites: 61 moons and one faint ring
Surface temperature: 10 000 degrees Celsius in the interior ocean; -140 degrees Celsius at the cloud tops; 25 000 degrees Celsius at the centre. Therefore, Jupiter radiates more heat than it receives

Appearance of surface

The visible cloud tops of Jupiter are divided into multicoloured cloud belts and zones, stretched out by Jupiter’s rapid rotation. The Great Red Spot, easily visible with small telescopes, is the largest example of the many violent storms in Jupiter’s atmosphere. There is a vast liquid hydrogen ocean under the visible cloud tops.

Appearance in Earth’s sky

Jupiter is easily visible for about 10 months of the year, appearing as a very bright, star-like object.

Telescopic appearance

Jupiter offers a wealth of detail to telescope users. The cloud bands, the Great Red Spot, and the four Galilean moons are all easily visible.


© Canadian Heritage Information Network, 2003

Jupiter

The visible cloud tops of Jupiter are divided into multicoloured cloud belts and zones, stretched out by Jupiter's rapid rotation.

NASA

© NASA


Jupiter's Orbit

Canadian Heritage Information Network

© Canadian Heritage Information Network 2003


Jupiter rotates on its axis every 9 hours and 55 minutes. Watch a video of Jupiter. Can you see the Great Red Spot?

Canadian Heritage Information Network

© Canadian Heritage Information Network, 2003


Saturn is best known for its beautiful system of rings. The ring system is only about 10 kilometres thick and is made up of particles of ice and dust. Most of the rings are less than one metre across, but a few are as large as 100 kilometres across. During 1995, Saturn’s rings were visible almost edge-on, making them appear to vanish as viewed from Earth.

The basics

Order (outwards from the Sun): 6
Average distance from the Sun: 1 429 000 000 km (9.56 astronomical units)
Period of revolution (length of year): 29.42 years
Period of rotation (length of day): 10 hours 40 minutes at the equator
Diameter: 120 540 km at the equator; rings are 275 000 km across
Surface gravity: 1.08 times greater than Earth’s
Composition: Scientists are not sure if Saturn is made completely of gases or if it has a solid rocky core. The entire planet has a density less than water- if you could put it in a big enough bathtub, it would float
Atmosphere: Hydrogen, helium, some methane and ammonia
Satellites: 31 moons and a ring system of 23 major rings
Surface temperature: -190 degrees Celsius at the clo Read More

Saturn is best known for its beautiful system of rings. The ring system is only about 10 kilometres thick and is made up of particles of ice and dust. Most of the rings are less than one metre across, but a few are as large as 100 kilometres across. During 1995, Saturn’s rings were visible almost edge-on, making them appear to vanish as viewed from Earth.

The basics

Order (outwards from the Sun): 6
Average distance from the Sun: 1 429 000 000 km (9.56 astronomical units)
Period of revolution (length of year): 29.42 years
Period of rotation (length of day): 10 hours 40 minutes at the equator
Diameter: 120 540 km at the equator; rings are 275 000 km across
Surface gravity: 1.08 times greater than Earth’s
Composition: Scientists are not sure if Saturn is made completely of gases or if it has a solid rocky core. The entire planet has a density less than water- if you could put it in a big enough bathtub, it would float
Atmosphere: Hydrogen, helium, some methane and ammonia
Satellites: 31 moons and a ring system of 23 major rings
Surface temperature: -190 degrees Celsius at the cloud tops. Like Jupiter, Saturn radiates more heat than it receives from the Sun

Appearance of surface

Saturn has cloud structures similar to Jupiter, but not as pronounced. There is probably a liquid hydrogen ocean under the visible cloud tops.

Appearance in Earth’s sky

Saturn can be seen in the sky as a bright star-like object. It moves very slowly against the background stars, and several weeks may be required to see it change its position relative to the stars.

Telescopic appearance

A good pair of binoculars will reveal that Saturn is not quite round,due to its ring system. Almost any telescope that magnifies over 30 times will show the rings of Saturn and perhaps a faint cloud band or two on the disk of the planet.

The view of Saturn through a telescope is one of the most beautiful sights in astronomy.


© Canadian Heritage Information Network, 2003

Saturn

Saturn is best known for its beautiful system of rings. The ring system is only about 10 kilometres thick and is made up of particles of ice and dust. Most of the rings are less than one metre across, but a few are as large as 100 kilometres across.

NASA

© NASA


Uranus was discovered by amateur astronomer William Herschel in 1781 using a six-inch telescope. The planet is tilted on its side relative to its orbit around the Sun. The north pole of Uranus sometimes points almost directly towards the Sun, and sometimes almost directly away. This means that the "daytime" and "nighttime" on Uranus can be over 40 years long!

Uranus was visited by the Voyager 2 robotic spacecraft in January 1986. Voyager 2 increased our knowledge of Uranus tremendously by providing close-up pictures of the planet and its moons and ring system.

The basics

Order (outwards from the Sun) : 7
Average distance from the Sun : 2 875 000 000 km (19.22 astronomical units)
Period of revolution (length of year) : 83.75 years
Period of rotation (length of day) : 17 hours 14 minutes at the equator
Diameter : 51 120 km at the equator
Surface gravity : 0.91 times greater than Earth’s
Composition : Possibly has an inner rocky core, overlaid with ice (frozen methane, water and ammonia) covered with an ocean of liquid hydrogen
Atmosphere : Hydrogen, helium, methane Read More

Uranus was discovered by amateur astronomer William Herschel in 1781 using a six-inch telescope. The planet is tilted on its side relative to its orbit around the Sun. The north pole of Uranus sometimes points almost directly towards the Sun, and sometimes almost directly away. This means that the "daytime" and "nighttime" on Uranus can be over 40 years long!

Uranus was visited by the Voyager 2 robotic spacecraft in January 1986. Voyager 2 increased our knowledge of Uranus tremendously by providing close-up pictures of the planet and its moons and ring system.

The basics

Order (outwards from the Sun) : 7
Average distance from the Sun : 2 875 000 000 km (19.22 astronomical units)
Period of revolution (length of year) : 83.75 years
Period of rotation (length of day) : 17 hours 14 minutes at the equator
Diameter : 51 120 km at the equator
Surface gravity : 0.91 times greater than Earth’s
Composition : Possibly has an inner rocky core, overlaid with ice (frozen methane, water and ammonia) covered with an ocean of liquid hydrogen
Atmosphere : Hydrogen, helium, methane
Satellites : 22 moons, and 9 dark rings
Surface temperature : -195 degrees Celsius at the cloud tops

Appearance of surface

Probably a liquid surface under the visible cloud tops.

Appearance in Earth’s sky

Uranus is technically visible to the unaided eye, but it is near the limit of detection. It appears as an extremely faint greenish star.

Telescopic appearance

A large telescope reveals that Uranus is not a star but a tiny blue-green disk. The planet is so far away that cloud features are not visible in small telescopes.


© Canadian Heritage Information Network, 2003

Uranus

The north pole of Uranus sometimes points almost directly towards the Sun, and sometimes almost directly away. This means that the "daytime" and "nighttime" on Uranus can be over 40 years long!

STScI / NASA

© STScI / NASA


Neptune’s existence was predicted by both English mathematician John Adams and French mathematician U.J.J. Leverrier, based on irregularities in Uranus’ orbit. The German astronomer J.G. Galle began searching for a new planet and found it very near the predicted position.

In August 1989, the robotic spacecraft Voyager 2 flew past Neptune, radioing back close-up pictures of the planet and its family of moons. Voyager also discovered a large storm system, similar to Jupiter’s Great Red Spot, which is called The Great Dark Spot.

Due to the elliptical shape of Pluto’s orbit, Neptune is the furthest planet from the Sun for about 20 years out of every 248 years. This was the case from about 1979 to 1999.

The basics

Order (outwards from the Sun): 8 or 9
Average distance from the Sun: 4 504 400 000 km (30.11 astronomical units)
Period of revolution (length of year): 163.73 years
Period of rotation (length of day): 16 hours 3 minutes at equator
Diameter: 49 530 km at the equator
Surface gravity: 1.19 times greater than Earth’s
Composition: Hydrogen and helium ic Read More

Neptune’s existence was predicted by both English mathematician John Adams and French mathematician U.J.J. Leverrier, based on irregularities in Uranus’ orbit. The German astronomer J.G. Galle began searching for a new planet and found it very near the predicted position.

In August 1989, the robotic spacecraft Voyager 2 flew past Neptune, radioing back close-up pictures of the planet and its family of moons. Voyager also discovered a large storm system, similar to Jupiter’s Great Red Spot, which is called The Great Dark Spot.

Due to the elliptical shape of Pluto’s orbit, Neptune is the furthest planet from the Sun for about 20 years out of every 248 years. This was the case from about 1979 to 1999.

The basics

Order (outwards from the Sun): 8 or 9
Average distance from the Sun: 4 504 400 000 km (30.11 astronomical units)
Period of revolution (length of year): 163.73 years
Period of rotation (length of day): 16 hours 3 minutes at equator
Diameter: 49 530 km at the equator
Surface gravity: 1.19 times greater than Earth’s
Composition: Hydrogen and helium ice
Atmosphere: Hydrogen, helium, methane
Satellites: 11 moons and 5 incomplete ring arcs
Surface temperature: -205 degrees Celsius at the cloud tops

Appearance of surface

Perhaps a rocky core surrounded by massive layers of ice. May be covered by a deep ocean of liquid hydrogen under the visible cloud tops.

Appearance in Earth’s sky

Neptune is so far away it cannot be seen without the aid of a telescope. Neptune revolves so slowly that it spends years in basically the same area of the sky.

Telescopic appearance

Even in large telescopes, Neptune appears as a small pale blue speck, with no detail visible.


© Canadian Heritage Information Network, 2003

Neptune

Due to the elliptical shape of Pluto's orbit, Neptune is the furthest planet from the Sun for about 20 years out of every 248 years. This was the case from about 1979 to 1999.

NASA / JPL

© NASA / JPL


Pluto’s orbit is very different from that of the other planets. In fact, in 2006, Pluto was declared by scientists to not be a planet at all, but a dwarf planet, like other small bodies beyond Pluto that are within reach of the Sun’s gravitational pull. Pluto orbits in a highly oval path called an ellipse, which is angled to the other planets’ orbits by about 17.1 degrees. Pluto’s distance from the Sun varies because of this oval path, so that sometimes it is closer to the Sun than Neptune.
In 1976, James Christie discovered Pluto’s moon, Charon. Charon is about half as big as Pluto, which makes Pluto and Charon more like a double planet than a planet and moon.

The basics

Order (outwards from the Sun): 9 or 8
Average distance from the Sun: 5 915 800 000 km (39.55 astronomical units)
Period of revolution (length of year): 248.03 years
Period of rotation (length of day): 6 days 9 hours 17 minutes
Diameter: 2 300 km
Surface gravity: 0.05 times greater than Earth’s
Composition: Probably rock covered with methane ice
Atmosphere: A thin atmosphere of nitrogen, Read More

Pluto’s orbit is very different from that of the other planets. In fact, in 2006, Pluto was declared by scientists to not be a planet at all, but a dwarf planet, like other small bodies beyond Pluto that are within reach of the Sun’s gravitational pull. Pluto orbits in a highly oval path called an ellipse, which is angled to the other planets’ orbits by about 17.1 degrees. Pluto’s distance from the Sun varies because of this oval path, so that sometimes it is closer to the Sun than Neptune.
In 1976, James Christie discovered Pluto’s moon, Charon. Charon is about half as big as Pluto, which makes Pluto and Charon more like a double planet than a planet and moon.

The basics

Order (outwards from the Sun): 9 or 8
Average distance from the Sun: 5 915 800 000 km (39.55 astronomical units)
Period of revolution (length of year): 248.03 years
Period of rotation (length of day): 6 days 9 hours 17 minutes
Diameter: 2 300 km
Surface gravity: 0.05 times greater than Earth’s
Composition: Probably rock covered with methane ice
Atmosphere: A thin atmosphere of nitrogen, methane, and carbon monoxide that is produced only when Pluto is closest to the Sun
Satellites: 1 moon (Charon, diameter = 1 200 to 1 300 km)
Surface temperature: -215 degrees C

Appearance of surface

Scientists suppose that the rocky surface of Pluto is covered by ice frozen as hard as steel. There are also polar ice caps of frozen methane, which partially melt when Pluto is nearest the Sun, releasing the gas that forms Pluto’s atmosphere.

Appearance in Earth’s sky

Pluto is invisible without a moderate-sized telescope.

Telescopic appearance

Even with the largest telescopes on Earth, Pluto appears as a faint star-like point. No details can be seen at all. The Hubble Space Telescope has been able to resolve some rough details on Pluto’s surface, and also detect its moon, Charon.


© Canadian Heritage Information Network, 2003

Pluto

Pluto and its moon Charon, as revealed by the Hubble telescope.

STScI / NASA / ESO

© STScI / NASA / ESO


Learning Objectives

The learner will:

  • Understand the concept of planet and dwarf planet
  • Describe the basic features of Saturn, Jupiter, Uranus, Neptune, Pluto

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