Year 10 Astronomy Revision Name: _________________________________1. Arrange the 8 planets in order from the Sun.

1. Mercury 2. Venus 3. Earth 4. Mars 5. Jupiter 6. Saturn 7. Uranus 8. Neptune

2. Which are the 4 Inner Planets and which are the 4 Outer Planets?Give 3 differences between these 2 types of planets.

THE INNER PLANETSMercury, Venus, Earth and Mars

THE OUTER PLANETSJupiter, Saturn, Uranus and Neptune

Small size

Earth is the largest of the Inner Planets, with a diameter of 12,756 km (7,926 miles). Mercury is the smallest with a diameter of 4,878 km (3,031 miles)

Huge!

Jupiter, the largest planet, has a diameter of 142,984 km (88,846 miles). Neptune is the smallest of the Outer Planets with a diameter of 49,532 km (30,779 miles)

Have solid surfaces and thin/no atmospheres

In theory, it would be possible to stand on each of the Inner Planets, although you would only survive on Earth.

Balls of gas with no surface

Most of the Outer Planets are made of gas. It is likely that they have a much smaller solid or liquid centre. It would be impossible to stand on any of the Outer Planets.

Greater Density

The size and composition of the planets is caused by the density of the elements that make up the planets. The elements in the Inner Planets are more closely packed together, causing them to be smaller on solid.

Smaller Density

Despite being larger, the elements that make up the Outer Planets are less densely packed together causing them to be quite light for their size.

Varied atmospheres

The contents of the atmospheres of the Inner Planets varies from planet to planet. Mercury has no atmosphere although Sodium and Helium can be detected above the surface. Venus' atmosphere is mostly Carbon Dioxide with a very small amount of Nitrogen. Earth's atmosphere is mostly Nitrogen with a smaller amount of Oxygen and even smaller amounts of other gases. Mars has a similar composition of carbon dioxide and nitrogen as Venus although has a much thinner atmosphere.

Similar atmospheres

The atmospheres of the Outer Planets consist mostly of Hydrogen and Helium, with Methane also being present in the atmospheres of Uranus and Neptune. Other gases are present although in much smaller quantities.

Known by the ancients

The existence of the Inner Planets has been known about for thousands of years. The earliest astronomers didn't know that the four objects (including Earth) were planets, but they knew they existed.

Not known by the ancients

Of the Outer Planets, only Jupiter and Saturn were observed by ancient astronomers. The existence of Uranus and Neptune was not known until relatively recently. Uranus was discovered in 1781 and Neptune in 1846.

Spin slowly

Compared to the much larger Outer Planets, the Inner Planets spin quite slowly. Earth spins the quickest, taking 23 hours and 56 minutes to spin on its axis. Venus takes 243 days to spin on its axis, spinning in an opposite direction to the other planets.

Spin quickly

All of the Outer Planets spin quicker than the Inner Planets. Uranus spins slowest, taking 17 hours and 14 minutes to spin on its axis. Jupiter takes only 9 hours and 55 minutes to spin on its axis. This rapid rotation causes Jupiter and Saturn to appear squashed, wider across the equator than from top to bottom.

Orbit the Sun quickly

Because they are quite close to the Sun, the Inner Planets complete an orbit quickly. Mercury takes only 88 days to orbit the Sun. Mars takes 687 days.

Orbit the Sun slowly

The Outer Planets orbit the Sun from millions of miles and have a much greater distance to cover to complete an orbit, so take much longer to do so. Jupiter takes almost 12 years to complete an orbit and Neptune takes over 164 years.

Few Moons Lots of Moons

Only Earth and Mars have moons orbiting them. One moon orbits Earth and two small moons orbit Mars.

All of the Outer Planets have many moons orbiting them. There are 63 moons known to orbit Jupiter, 60 orbiting Saturn, 27 orbiting Uranus and 13 orbiting Neptune.

No rings None of the Inner Planets have rings orbiting them

Rings

All of the Outer Planets have rings orbiting them. The rings are thin discs of dust and rocks possibly caused by moons being broken up or not being completely formed while orbiting the planet. Saturn has the most visible ring system of any of the planets.

Multiple space craft visitors

Due to being close to Earth, there have been several missions to the other Inner Planets, especially to Mars and Venus. Mercury has been visited by two spacecrafts.

All Outer Planets visited by one space craft

There have been multiple visits to Jupiter and Saturn, but Uranus and Neptune have only been visited once. This was by Voyager 2 (which also visited Jupiter and Saturn).

3. Why Pluto is no longer a Planet (since 2006)?It occurred during the 2006 International Astronomical Society convention. Pluto was re-classified as a 'Dwarf Planet' because of even larger objects discovered further out from Pluto. It's thought that up to *50,000* Pluto-sized objects and larger could exist in the Kuiper belt, so, rather than have to come up with names for that many planets, Pluto's classification was changed, and it's now the first "Kuiper Belt Object" discovered.The orbit is not in the same plane as the orbits or other planets.

4. What is the meaning of orbit in astronomy? Give 3 examples of celestial objects that orbit others.Orbit means to revolve around another object.Planets orbit the Sun, comets orbit the Sun, asteroids orbit the Sun, moons orbit planets, artificial satellites orbit planets, stars can orbit each other (any 3).

5. Arrange these celestial objects according to their size in descending order.Milky Way, Super-cluster, Universe, Earth, Meteoroid, Jupiter, Sun, Local Group, Mars, Asteroid, Solar System, our Moon.Meteoroid Asteroid Our Moon Mars Earth Jupiter Sun Solar System Milky Way Galaxy Local Group Super-cluster Universe

6. What are the 2 opposite forces the control or maintain the integrity of a star? Explain briefly.Gravitational force as a result of the mass, pulling the star inward, against the outward radiation force from fusion of hydrogen.

7. Describe briefly the structure of our Sun.Much like the earth, the Sun has many different layers that define its structure. Unlike the earth, the Sun is completely gaseous, there is no solid surface on the Sun. Although the Sun is completely made of gas, the density and temperature of the gas changes drastically as you travel from the center to the outermost regions.

8. What is Nuclear Fission in the core of the Star?Stars are giant nuclear reactors. In the center of stars, atoms are taken apart by tremendous atomic collisions that alter the atomic structure and release an enormous amount of energy. This makes stars hot and bright. Stars are powered by nuclear fusion in their cores, mostly converting hydrogen into helium.

9. What determines the formation of other elements in stars?

A star's mass determines what other type of element undergoing fusion in its core (or during explosive changes in its life cycle)

a. Small stars: The smallest stars only convert hydrogen into helium. b. Medium-sized stars (like our Sun): Late in their lives, when the hydrogen

becomes depleted, stars like our Sun can convert helium into oxygen and carbon.

c. Massive stars (greater than five times the mass of the Sun): When their hydrogen becomes depleted, high mass stars convert helium atoms into carbon and oxygen, followed by the fusion of carbon and oxygen into neon, sodium, magnesium, sulfur and silicon. Later reactions transform these elements into calcium, iron, nickel, chromium, copper and others. When these old, large stars with depleted cores supernova, they create heavy elements (all the natural elements heavier than iron) and spew them into space, forming the basis for life.

10. Name the 3 main types of Galaxies in the Universe and give an example of each type.(1) Spiral galaxies get their name from the shape of their disks, in which stars, gas and dust are concentrated in spiral arms that extend outward from the central nucleus of the galaxies. Eg. The Milky Way, Andromeda Galaxy(2) Elliptical galaxies are elliptical in shape, eg. M32, Sagittarius Dwarf Elliptical galaxy.(3) Irregular galaxies have no particular shape, eg. The Large and Small Magellanic Clouds

11. What is the Big Bang Theory? Big-bang theory states that the universe originated sometime between 10 billion and

20 billion years ago from the cataclysmic explosion of a small volume of matter at extremely high density and temperature.

The Big Bang theory describes how the Universe began in a rapid expansion about 13.7 billion years ago and has evolved since that time.

The Big Bang theory states that the universe began from an initial point or singularity which has expanded over billions of years to form the universe as we now know it.

12. What is a LIGHT YEAR? Why is it commonly used in astronomy?A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.46 × 1012 km.Calculation: Light moves at a velocity of about 300,000 kilometers (km) each second.No. of second in one year = 365 days x 24 hours x 60 mins x 60 secs = 31,536,000 secDistance = Speed x Time = 300,000 x 31,536,000 = 9.46 × 1012 km.Light Year is used to measure the very far away distance between stars.Our nearest star (Proxima Centauri) is 4.2 light year away.Our Milky way is about 100,000–120,000 light-years in diameter which contains approximately 100–400 billion stars.

13. Why is it difficult to travel to another star?The nearest star is 4.2 light years away. It will take If the spacecraft is 1000 km/hour, it will take 80,000 years to reach at a super-speed of 240,000 km/hr.

14. What does E=mc2 stand for?E = mc2 is perhaps the most famous equation of all time. It stands for E(energy) = Mass times the Speed of Light (C) squared. What this means is that if you take the mass of an object and multiply it by the speed of light (2.9 x 10^8 metres per second) you will then have calculated the amount of energy. As you can see, even a tiny amount of mass when multiplied by such a huge number (C) yields an incredible amount of energy. Releasing that energy can do everything from power cities (a nuclear power plant) to destroy them (a nuclear bomb).

15. What is the common name for all the radiation from the stars and matter in the universe? List all these radiations in order from long to short wavelengths.Electromagnetic RadiationRadiowaves Microwaves Infra-red Visible light Ultraviolet X-ryas Gamma rays Cosmic rays(Roy's Mother Is Visiting Uncle Xavier's Garden for a Coffee)

16. What is the use of Radio telescope? Why is it more useful than optical telescope?An instrument used to detect radio emissions from the sky, whether from natural celestial objects or from artificial satellites.It can detect the star’s size, shape, movement, temperature, composition and location. It can detect tiny amounts of energy from vast distances away, through Earth’s atmosphere and dust and gases in deep space.It can be placed on Earth instead of the Hubble Space Telescope in space.

17. What is a Space Shuttle? What is the use of space shuttles?

The space shuttle is the "world's first reusable spacecraft," launching like a rocket, orbiting like a spacecraft, and landing like a plane.

Space shuttles could carry satellites, space probes, and other cargo into orbit around Earth on both commercial and non-commercial missions.

The space shuttle system was made up of three components: - Two white solid rocket boosters. They provided 80% of the launch thrust. - The external orange tank, which provided fuel to the space shuttle main engines during launch. - The white orbiter. It acted as the crew's home during the flight. The space shuttle normally took as many as seven astronauts to and from space.

All of the components were reused except for the external fuel tank. It burned up in the atmosphere after launch.

There were five orbiters in the shuttle program's history: Atlantis, Challenger, Columbia, Discovery and Endeavour.

The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger (mission STS-51-L) broke apart 73 seconds into its flight, leading to the deaths of its seven crew members.

The Space Shuttle Columbia disaster occurred on February 1, 2003, when, shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana as it reentered Earth's atmosphere, killing all seven crew members.

What Did the Space Shuttle Do?a. It was used to launch satellites and serve as an orbiting science laboratory. b. Its crews repaired and improved other spacecraft, such as the Hubble Space Telescope. c. The shuttle was used for military missions. d. Finally, the space shuttle was mostly used to work on the International Space Station.

18. How Did the Space Shuttle Launch and Land?

The space shuttle took off like a rocket. The solid rocket boosters and the main engines on the orbiter

provided the thrust for launch. The solid rocket boosters burned for about two minutes. Then they were dropped from the shuttle and fell into the ocean.

Special boats brought them back so they could be used again. The shuttle's main engines fired for about another six minutes. The external tank is dropped when all the fuel was  used. Shortly after this happened the shuttle and crew were in orbit. The orbiter landed like a glider. While in orbit it fired its engines to slow down and stop orbiting. After it re-entered Earth's atmosphere, it glided in for a landing

on a runway.

20.

Intrepret the Hertzsprung-Russell diagram:The diagram shows the

various stages of stellar evolution. By far the most prominent feature is the main sequence stars, which runs from the upper left (hot, luminous stars) to the bottom right (cool, faint stars) of the diagram. Our Sun is a main sequence star with average size, medium temperature and luminosity. Similar stars (like our Sun) spend about 90% of their lives burning hydrogen into helium in their cores.

The giant and supergiant stars lie above the main sequence, and white dwarfs are found below it. Stars enter this evolutionary stage once they have exhausted the hydrogen fuel in their cores and have started to burn helium and other heavier elements.

White dwarf stars are the final evolutionary stage of low to intermediate mass stars, and are found in the bottom left of the HR diagram. These stars are very hot but have low luminosities due to their small size.

21. List some tools used for Space Exploration.Satellites, Space probes, Space Shuttle, Hubble Space Telescope (HST), Other spacecraft like the Mars Rover, International Space Station (ISS), Rocket and Communication Tools.NB: Space probes are spacecraft sending to the space for a purpose. Satellites are spacecraft that orbiting the Earth for many purposes.

Sun