Features of our solar system

Features of the solar system

The solar system is the name for the Sun and all the objects that circle around it. This includes:

eight planets
several moons
five dwarf planets
asteroids
comets
gas
dust

The Sun is our closest star and is at the centre of the solar system. The Sun is a star of medium size and is much closer to Earth than other stars. This is why it looks much bigger and brighter than other stars. If the Sun were as far away as Proxima Centauri, the nearest star after the Sun, it would be too tiny and faint to see.

The Sun has most of the mass in our solar system. Although the Sun is not very large for a star (a circumference of 4.3 million km around the equator), it is very big and very massive compared to the planets.

The Sun’s huge mass creates a strong gravitational field around it, which makes smaller objects like planets, asteroids and comets go around it in elliptical paths. Planets move in nearly round paths around the Sun, whereas asteroids and comets follow paths that are more oval (or elliptical) shaped.

Image showing the order of planets in our solar system. From left to right: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Planets

The Earth is one of a family of eight planets. All of these are orbiting round the Sun. Together with the Sun and the 8 planets makes our Solar System. All eight planets are different in every respect.

For example, in shape, size and conditions. The distances between the planets are enormous; much farther than the picture on the top of this page.

Click here to see the Solar System.

Inner Planets	Mercury	Venus	Earth	Mars	Asteroids
Distance from the Sun (million Km)	60	110	150	230	-
Time to Travel once round the Sun ( Earth years)	0.2	0.6	1	2	-
Diameter (Km)	5000	12000	12800	7000	-

Outer Planets	Jupiter	Saturn	Uranus	Neptune
Distance from the Sun (million Km)	780	1400	2900	4500
Time to Travel once round the Sun ( Earth years)	12	30	84	160
Diameter (Km)	140000	120000	52000	50000

Dwarf planets.

In addition to these 8 planets are 5 smaller dwarf planets (which are too small to be considered planets). These are Pluto, Eris, Haumea, Makemake and Ceres.
As of August 24, 2006, Pluto was no longer considered a planet and is instead described as a Dwarf Planet.

Image showing the dwarf planets in our solar system. From left to right: Pluto, Eris, Haumea, Makemake and Ceres.

Image showing the dwarf planets in our solar system and sizes compared to the Earth and Moon. From left to right: Pluto, Eris, Haumea, Makemake and Ceres.

Try these questions!

You could use the table above to answer the following questions.

Q1. How long does it take for the Earth to orbit round the Sun once?

Q2. Which heavenly body is bigger, the Sun or the Earth?

Q3. Which planet is the smallest

Q4. Which planet is biggest?

Q5. Which planet is the coldest?

Q6. Which planet is farthest from the Sun?

Q7. Which planet is nearest to the Sun?

Q8. Which planet has large rings?

Q9. Which planet is Approximately the same size as the Earth?

Q10. Name all the planets which are larger then the Earth?

Q11. Which is the hottest planet?

Q12. Which planet comes between Jupiter and Earth?

Q13. Which planet takes the shortest time to orbit the Sun once?

Q14. What trend can you see between the time for one complete orbit and the distance from the Sun?

Q15. What do you find between Mars and Jupiter and what are they?

Q16. What pattern can you see between the surface temperature and the distance from the Sun?

Q17. What keeps the planets in their orbit around the Sun?

Q18. Name the shape of the orbit that planets move round the Sun?

Q19. State the names of 4 inner planets?

Q20. Why is the temperature higher on these 4 inner planets than the 5 outer planets?

Q21. Does the Sun look bigger from Pluto or Mercury?

Q22. Why was Pluto the last planet to be discovered?

Click here for answers!

Click here to take an interactive Solar System Quiz

Our Solar System

Mercury - Venus - Earth - Mars - The inner planets

The four inner planets are all made of rocks and have metallic cores. Our Earth is the largest of these inner planets.

Mercury: this is the smallest planet, roughly the size of our moon and is closest to the Sun. Its mass is not great enough to produce a strong gravitational field and for this reason it is unable to sustain atmosphere. The gases just simply drift into space. The side of Mercury facing the Sun can reach temperature high enough to melt lead (430ºC), while the dark side drops to -170ºC.

Venus: It is almost the same size as the Earth. It is an unpleasant planet. It has a rocky surface, covered by dense clouds of sulphuric acid and carbon dioxide. These clouds of gas entirely hide the surface of Venus. This traps the Sun's heat due to the ' Super Greenhouse Effect' and for this reason it surface temperature is higher then that of Mercury (approximately 500ºC). Without this atmosphere, Venus' temperature would be a lot lower. It reflects a lot of light, so Venus looks bright. It is also known as the 'Morning and the evening Star'.

Earth: If you view the Earth from space, it looks blue with swirls of clouds. Its surface is rocky, with mountains and canyons, which are covered with water and ice. It is the only planet with water, oxygen and living thing. Planet Earth has just the right conditions for life to exist, because it is at the right distance from the Sun . It has one moon. No doubt, other stars in the universe might have planets with the same life sustaining conditions.

Mars: It is called the red planet. It is dry cold desert of red rock, with massive mountains and canyons. It is most like Earth. It has a thin atmosphere of carbon dioxide (95%), nitrogen, oxygen, water vapour and noble gases. there is no life on it. It has 2 small moons. The dark patch is a giant volcano.

Saturn - Uranus - Neptune - The outer planets

Jupiter: The largest of the planets and the coldest. It has no solid surface, it is a liquid giant. It is made up of mainly liquid hydrogen and helium, surrounded by these gases and clouds. The bands of colour , in Jupiter are produced by different regions in the atmosphere. The great red spot is thought to be an area where the atmosphere constantly swirls around a giant storm. This spot is 3 times the size of Earth. Jupiter is surrounded by 16 moons.

Saturn: A gas giant, very much like Jupiter. It is made mostly of hydrogen and helium. It has the most striking ring system of all the outer planets. The 18 rings are made from billions of tiny particles of rock and ice. They are held together in orbit by the pull of Saturn's gravity. It has 18 moons.

Uranus: Another gas giant, made up of hydrogen and helium. It is different from other planet, because it is lying on its side as it goes round the Sun. The spin axis of Uranus is tilted at 98°, so that at times it poles point towards the Sun, giving rise to extreme seasons. It has 15 moons and 11 rings.

Neptune: Appears in the sky as tiny blue-green speck, using even the most powerful telescope on Earth, because it is so far away from the Sun, where the light is one thousandth as strong as on Earth. Neptune is a ball of water and rock, consisting of atmosphere of hydrogen, helium and methane. The great dark spot is a storm, about the size of Earth.

My Very Easy Method Just Speeds Up Naming

Learn this line to remember the names of the 8 planets.

Summary of data on planets.

Planets	Diameter (Km)	Distance from Sun (Km)	Time for one orbit (planet's year - relative to Earth)	Time for one spin (planet's day - relative to Earth)	Average temperature - side facing the sun (ºC)	Moons & rings
Mercury	5000	60	88 days	1400 hours	+430	0
Venus	12000	110	220 days	5800 hours	+470	0
Earth	12800	150	356 ¼ days	24 hours	+20	1
Mars	7000	230	2 years	25 hours	-20	2
Asteroids
Jupiter	140000	780	12 years	10 hours	-150	160
Saturn	120000	1400	30 years	10 hours	-180	18 + 18
Uranus	52000	2900	84 years	17 hours	-210	15 + 11
Neptune	50000	4500	160 years	16 hours	-220	8

Continue... Beyond our Solar System

Summary:

The Sun (our closest star) and the objects that circle around it, such as planets, asteroids and comets, make up the solar system.
Planets move around the Sun in nearly round paths, and moons move around planets.
Asteroids and comets follow paths that are more egg-shaped.
The Sun’s gravity keeps all of these objects together, and the gravitational forces between objects can make less massive objects go around more massive objects.