PLANETS

There are 8 planets in our solar system, they are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus andNeptune. With the exception of Neptune and Uranus the other 6 planets can be seen unaided and all 8 are visible with a small telescope or binoculars.

ORDER OF PLANETS

The order of the planets from closest to the Sun outwards is; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and finally Neptune. The largest planet in the solar system is Jupiter, followed by Saturn, Uranus, Neptune, Earth, Venus, Mars with the smallest being Mercury.

Name Diameter Distance from the Sun Orbit Period

Mercury 4,879 km 57,909,227 km (0.39 AU)88 days

Venus 12,104 km 108,209,475 km (0.73 AU)225 days

Earth 12,742 km 149,598,262 km (1 AU)365.26 days

Mars 6,779 km 227,943,824 km (1.38 AU)1.9 years

Jupiter 139,822 km 778,340,821 km (5.20 AU)11.9 years

Saturn 116,464 km 1,426,666,422 km (9.58 AU)29.5 years

Uranus 50,724 km 2,870,658,186 km (19.22 AU)84.0 years

Neptune 49,244 km 4,498,396,441 km (30.10 AU)164.8 years

WHAT ARE PLANETS?

Planets are among the many worlds and smaller objects that orbit the Sun. The formal definition of planet, as voted on by the International Astronomical Union in 2006, is as follows:

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 neighbourhood around its orbit.

Under this definition, Pluto is NOT a planet, but has been deemed a dwarf planet because it has not yet cleared its orbit. This definition is under discussion, particularly by members of the planetary science community, and it may yet be further refined.

PLANETS FAQ

• How many planets are there in our solar system? 8

• What is the smallest planet? Mercury

• What is the largest planet? Jupiter

• Which planet is closest to the Sun? Mercury

• Which planet is farthest from the Sun? Neptune

• What is the coldest planet? On average Neptune is the coldest planet

• What is the hottest planet? Venus

• What are the inner planets? Mercury, Venus, Earth and Mars

• What are the outer planets? Jupiter, Saturn, Uranus and Neptune

• Which planets have rings? Jupiter, Saturn, Uranus and Neptune

• Is there life on other planets? Not that has been encountered so far!​

HERE ARE THE FACTS ABOUT THE PLANETS

1-MERCURY

Mercury is the closest planet to the Sun and due to its proximity it is not easily seen except during twilight. For every two orbits of the Sun, Mercury completes three rotations about its axis and up until 1965 it was thought that the same side of Mercury constantly faced the Sun. Thirteen times a century Mercury can be observed from the Earth passing across the face of the Sun in an event called a transit, the next will occur on the 9th May 2016.

Planet Profile

Diameter:4,879 km

Mass:3.29 × 10^23 kg (0.06 Earths)

Moons:None

Orbit Distance:57,909,227 km (0.39 AU)

Orbit Period:88 days

Surface Temperature:-173 to 427°C

First Record:14th century BC

Recorded By:Assyrian astronomers

2-VENUS

Venus is the second planet from the Sun and is the second brightest object in the night sky after the Moon. Named after the Roman goddess of love and beauty, Venus is the second largest terrestrial planet and is sometimes referred to as the Earth’s sister planet due the their similar size and mass. The surface of the planet is obscured by an opaque layer of clouds made up of sulfuric acid.

Planet Profile

Diameter:12,104 km

Mass:4.87 × 10^24 kg (0.82 Earths)

Moons:None

Orbit Distance:108,209,475 km (0.73 AU)

Orbit Period:225 days

Surface Temperature:462 °C

First Record:17th century BC

Recorded By:Babylonian astronomers

3-EARTH

Earth is the third planet from the Sun and is the largest of the terrestrial planets. The Earth is the only planet in our solar system not to be named after a Greek or Roman deity. The Earth was formed approximately 4.54 billion years ago and is the only known planet to support life.

Planet Profile

Equatorial Diameter:12,756 km

Polar Diameter:12,714 km

Mass:5.97 × 10^24 kg

Moons:1 (The Moon)

Orbit Distance:149,598,262 km (1 AU)

Orbit Period:365.26 days

Surface Temperature:-88 to 58°C

4-MARS

Mars is the fourth planet from the Sun. Named after the Roman god of war, and often described as the “Red Planet” due to its reddish appearance. Mars is a terrestrial planet with a thin atmosphere composed primarily of carbon dioxide.

Planet Profile

Equatorial Diameter:6,792 km

Polar Diameter:6,752 km

Mass:6.39 × 10^23 kg (0.11 Earths)

Moons:2 (Phobos & Deimos)

Orbit Distance:227,943,824 km (1.38 AU)

Orbit Period:687 days (1.9 years)

Surface Temperature:-87 to -5 °C

First Record:2nd millennium BC

Recorded By:Egyptian astronomers

5-JUPITER

The planet Jupiter is the fifth planet out from the Sun, and is two and a half times more massive than all the other planets in the solar system combined. It is made primarily of gases and is therefore known as a “gas giant”.

Planet Profile

Equatorial Diameter:142,984 km

Polar Diameter:133,709 km

Mass:1.90 × 10^27 kg (318 Earths)

Moons:67 (Io, Europa, Ganymede & Callisto)

Rings:4

Orbit Distance:778,340,821 km (5.20 AU)

Orbit Period:4,333 days (11.9 years)

Surface Temperature:-108°C

First Record:7th or 8th century BC

Recorded By:Babylonian astronomers

6-SATURN

Saturn is the sixth planet from the Sun and the most distant that can be seen with the naked eye. It is best known for its fabulous ring system that was discovered in 1610 by the astronomer Galileo Galilei.

Planet Profile

Equatorial Diameter:120,536 km

Polar Diameter:108,728 km

Mass:5.68 × 10^26 kg (95 Earths)

Moons:62 (Titan, Enceladus, Iapetus & Rhea)

Rings:30+ (7 Groups)

Orbit Distance:1,426,666,422 km (9.58 AU)

Orbit Period:10,756 days (29.5 years)

Surface Temperature:-139 °C

First Record:8th century BC

Recorded By:Assyrians

7-URANUS

Uranus is the seventh planet from the Sun. It’s not visible to the naked eye, and became the first planet discovered with the use of a telescope. Uranus is tipped over on its side with an axial tilt of 98 degrees. It is often described as “rolling around the Sun on its side.”

Planet Profile

Equatorial Diameter:51,118 km

Polar Diameter:49,946 km

Mass:8.68 × 10^25 kg (15 Earths)

Moons:27 (Miranda, Titania, Ariel, Umbriel & Oberon)

Rings:13

Orbit Distance:2,870,658,186 km (19.22 AU)

Orbit Period:30,687 days (84.0 years)

Surface Temperature:-197 °C

Discovery Date:March 13th 1781

Discovered By:William Herschel

8-NEPTUNE

Neptune is the eighth planet from the Sun making it the most distant in the solar system. This gas giantplanet may have formed much closer to the Sun in early solar system history before migrating to its present position.

Planet Profile

Equatorial Diameter:49,528 km

Polar Diameter:48,682 km

Mass:1.02 × 10^26 kg (17 Earths)

Moons:14 (Triton)

Rings:5

Orbit Distance:4,498,396,441 km (30.10 AU)

Orbit Period:60,190 days (164.8 years)

Surface Temperature:-201 °C

Discovery Date:September 23rd 1846

Discovered By:Urbain Le Verrier & Johann Galle