"When we contemplate the whole globe as one great dewdrop, striped and dotted with continents and islands, flying through space with other stars all singing and shining together as one, the whole universe appears as an infinite storm of beauty." -John Muir

When we look up to the sky on a clear, crisp night in the country we are simply blown away by the number of stars we can see in our galaxy.

There are so many individuals who buy a telescope and take up the hobby of astronomy due to the fact that they are interested in learning more about space, the solar system, galaxies and stars. The intrigue of space has fascinated people for many centuries and there are no signs of decline in this trend.

Students who have a passion for the sky and are considering exploring the GCSE Physics Syllabus will be happy to know that the last topic in this syllabus is all about space!

The last topic in the GCSE Physics Syllabus designed by the AQA exam board in the United Kingdom covers the sections of the solar system, the life cycle of a star and the expanding universe.

Superprof is here to guide students through the concepts learnt in this favourite and last topic of the GCSE Physics Syllabus.

## The Solar System

Our solar system is a unique and awe-inspiring place. The milky way galaxy is filled with billions of stars and the sun is one of them. Our solar system consists of important elements that make it one of a kind:

• The Sun: the largest object in the solar system. Due to its large gravitational field, planets, asteroids and comets all orbit around it.
• Planets: there are eight planets that orbit around the sun at different times. The third rock from the sun, also known as Earth, is our home due to its perfect position that makes life possible. All planets are distinct and have different properties. For example, Mercury is the closest to the sun and has a temperature of 430 Celsius and Neptune is the farthest and has a temperature of -200 Celsius. In order for a planet to form, its gravity needs to be strong enough to make it a sphere or round in shape.
• Moons: natural satellites that orbit a planet. Many of the planets in our solar system have more than one moon with Saturn having more than 50.
• Dwarf planets: Pluto has been considered a dwarf or "minor" planet since 2006 when it was considered not strong enough to "clear the neighbourhood" so there may be other objects in its orbit around the Sun. There have been hundreds of dwarf planets discovered in The Solar System.
• Asteroids: these oval-shaped objects that are made of rocky materials orbit the Sun and may take millions of years to complete their obit.
• Comets: very similar to asteroids, however, they are made up of rocky material, dust and ice. When a comet approaches the sun it begins to vaporise and turns into a gas.

### The Sun

Students in this section will learn that according to scientists, the solar system was formed over 4 billion years from a large cloud of dust and gas called a nebula. As the nebula collapsed it became denser and rotated around more rapidly.

When the Sun's core became hot and dense enough, nuclear fusions began which caused hydrogen nuclei to join together and form helium nuclei and energy was transferred by radiation.

### Orbital Speed and Orbits

Gravity is an important force that maintains the stable orbit of planets around a star, moons and artificial satellites around a planet. For an object to remain at a stable, steady orbit it must be moving at the right speed.

The orbital speed of a planet can change with its distance from the Sun.

The reasons for this are studied further by students in this section of the GCSE Physics Syllabus.

You can get a jump on those studies with a maths and physics tutor...

## The Life Cycle of a Star

The life cycle of a star completely depends on its size. In this section of the Solar System topic, students study a diagram to show how long the life cycle of stars would be for those who are about the same size of the sun and far greater than the size of the sun.

All stars begin life in the same exact way: a cloud of dust and gas, also known as a nebula, becomes a protostar which goes on to become a main sequence star.

Stars that are about the same size as the sun take the left path on the diagram and those who are larger in size than the sun take the right path on the diagram. Here are some further details about each type of star and how they are formed:

• A nebula: stars are formed from massive clouds of dust and gas, known as nebulas. Gravity does its jobs and pulls the gas and dust together to make the new star.
• Protostar: a new star is formed when it is hot enough for the hydrogen nuclei to form together and make helium.
• Main Sequence Star: also known as the stable phase of the star due to the fact that the force of gravity that is holding the star together is balanced by high pressure due to the high temperatures. The Sun as we know it is in its stable phase in its life.
• Red Giant Star: after all the hydrogen has been used in the fusion process of the star, larger nuclei begin to form and the star may expand to become a red giant.
• White Dwarf: after all the nuclear reactions are over, a small star may begin to contract under the pull of gravity. If this is the case, the star becomes a white dwarf which changes colour as it cools down.
• Supernova: a very large star with more mass will continue to get hotter and hotter until it explodes as a supernova. This massive star throws hot gas into space when it explodes.
• Neutron Star (aka Black Hole): becoming a neutron star or black hole all depends on the size of the supernova when it was first formed.

For most of its life, a star is considered a main sequence star. It is very stable with balanced forces that keep it the same size all the time. The Sun has been studied by astronomers and is expected to remain as a main sequence star for billions and billions of years.

There is a fusion reaction that occurs in a main sequence star: hydrogen nuclei fuse together with helium nuclei and this happens in several steps.

All of the naturally occurring events in the Universe are produced by nuclear fusion reactions in the stars. After a while, the star will run out of hydrogen and other fusion reactions take place forming the nuclei of other elements.

## The Expanding Universe

For years theories about the development of the universe have been analyzed by scientists. These theories are based on astronomical observations and ideas.

### Red Shift

Using the colours from the electromagnetic spectrum, scientists notice that elements in the star absorb some of the emitted wavelengths and dark lines become present in the spectrum when it is analyzed. Students acquire important information in this section such as how distinct elements produce different patterns of dark lines.

Astronomers use the spectrum to observe light from distant galaxies, the dark lines in the spectra show an increase in wavelength. When the lines are moved towards the red part of the spectrum, the effect is known as red-shift.

The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from the Earth.

### The Big Bang Theory

Not just a popular American television program, the Big Bang theory is a very famous scientific speculation studied by scholars all over the world.

The basic concepts of the Big Bang theory include the fact that about 13.8 billion years ago the whole Universe was a very small and dense region and from this tiny point the Universe expanded and became what it is today.

Red-shift data has proven this theory and shown that the Universe is constantly expanding.

Pupils also analyze supported evidence from the Cosmic Microwave Radiation Background (CMRB) that was discovered in 1964 and shows the remains of the thermal energy from the Big Bang.

### What is the Future of the Universe?

The future is very unsure and quite difficult to predict, however, scientists have been trying for years to work out the density of the Universe to see if it will continue expanding or eventually stop.

One thing scientists and astronomers do know is that much about the Universe is not currently understood. It is estimated that only about 5% of the Universe is made up of matter that is currently understood such as stars, galaxies and planets.

Dark energy is not well understood but it is believed to be the reason why the Universe is expanding all the time. Another concept that still needs time to be thoroughly understood is dark matter. This mass is invisible to the instruments used by scientists and is credited with being responsible for the fact that the galaxies move too quickly for the mass of their stars.

The future of the Universe is uncertain and there are various concepts that need to be better understood by scientists in order for proven theories to be created. Students learn all about this throughout the section space physics in the GCSE Physics Syllabus.

You should have an interesting discussion on this topic with your maths and physics tutor...

## Sample Exam Questions

Examination periods are very stressful for students in their last years of secondary school. They want the best test results in order to be considered for admission at the most prestigious universities in the United Kingdom.

Knowing what type of questions to expect on the examinations for the GCSE Physics Syllabus relieves the stress of students and boosts their overall results. Here are the different kinds of questions that can be anticipated on the exams:

• Multiple choice questions: the easiest to complete because all students have to do is put a cross in a box to choose the correct answer,
• One and two mark questions: these ones usually start with the words "describe" or "explain" and require students to write down a few logical sentences explaining their response,
• Three and four mark questions: these are the same as the previously mentioned questions, however, they require slightly longer answers,
• Maths questions: these ones might include graphs, tables and calculations. Students need to show their workings on how they arrived at their answer,
• Six mark questions: these are considered the most difficult for students due to the fact that long and logical answers are needed to get good results,
• Equations: these questions require pupils to recall the equations and information they learnt in previously taught classes.

Space is fascinating but can ultimately be called a giant mystery. The few things we know and can learn about captive the attention and the mystery of the things we have yet to learn have kept individuals intrigued for centuries. Learning more about the topic of space physics in the GCSE Physics Syllabus provides students with a great base for a future of studying the stars.

Space physics is only one of the many topics in the GCSE Physics option. Other topics discussed include electricity, particle model of matter, atomic structure, forces and waves.

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