Our Universe: what we think we know

Aims of the course

This course aims to:
Bring participants up to date on astronomers’ current understanding of the contents, size, nature and evolution of our universe.

Content

In this course we tell the story of our Universe from when it was a millionth of a second old until the present day and consider how it might end.

To do this we use light, which thanks to its finite speed, allows us to look back in time as we look deep in space, to the moment when the Universe was about 1/20 its present age.

We will follow the emergence of hydrogen and helium a few minutes after the Big Bang, through the first generation of stars, which may have been 1000 times the mass of the Sun, up to the present day.
Stars make up galaxies, which at their centres contain thousand million Solar mass black holes that govern their evolution. Galaxies form clusters that are immersed in giant haloes of gas so hot they emit X-rays, as well as halos of mysterious dark matter, which outweighs all other matter in the cluster.

On the very largest scale, the evolution of the Universe is dominated by the even stranger vacuum energy, about which we know even less.

The story of the birth and death of stars is the story of the battle of matter against gravity, a battle that gravity always wins, with either a whimper or a bang. It is also the story of the origin of all the elements that make up everything we see around us, including ourselves.

Low mass stars like the Sun enrich the galaxy with lighter elements like carbon nitrogen and oxygen, while more massive stars end their lives in giant supernova explosions producing heavier elements such as iron and leaving behind sometimes nothing, sometimes neutron stars or black holes. Double stars can interchange matter as they evolve and the final outcome can be two neutron stars that merge and produce the heaviest elements like gold.

We will take a more detailed look at our nearest star the Sun and see how it varies and how it effects our climate. From there we will tour the great variety of planets in our solar system and see how we think they were formed. Despite our solar system being one third of the age of the universe, it is still an active environment, with comets and asteroid collisions that occasionally have serious consequences for our Earth. We will then look at planets around other stars.

Finally, we will consider if we are the only self-aware beings in our Universe and if so why this may be.

Presentation of the course

The course will be presented in the conventional lecture style with the speaker in front and the audience facing forward. The course will be richly illustrated with images and diagrams.
There will be an opportunity for questions and discussion where appropriate.

Class sessions

1 The Scale and Contents of the Universe 1
We will look at the hierarchy of structures from stars, star clusters to galaxies and clusters of galaxies. The finite speed of light allows us to look back in time as we look deeper in space.
As we look at the Universe on ever greater scales and see the influence of dark matter and vacuum energy in shaping the past and future of the Universe. Visible light does not reveal all the matter in the Universe, which is only seen if we extend our use of the electromagnetic spectrum to the X-ray and infrared, revealing the hottest and coldest material in the Universe.

2 The Scale and Contents of the Universe 2
We will continue our exploration on ever larger scales and on the way consider the nature of Black Holes and their important role in the evolution of galaxies.
Finally, we will show how we can reproduce the evolution of the Universe from when it was a few hundred thousand years old to the present day using a small number of parameters and including the influence of vacuum energy and dark matter.

3 The Birth and Death of stars and Origin of the elements 1
We will see how hydrogen and helium were formed within the first few minutes after the formation of our Universe. The force of gravity then counters the expansion of the Universe forming the first stars. These were massive and evolved more rapidly than future generations of stars, enriching the Universe with the first heavy elements. After 9 thousand million years our Sun was born. We will then look in more detail at the evolution of solar mass stars and how they end their lives.

4 The Birth and death of stars and Origin of the elements 2
In this lecture we will see how stars more than five to eight times the mass of the Sun explode as super novae, creating more heavy elements. We will then look at the most massive stars and how they create black holes or neutron stars and be responsible for the bursts of gamma rays seen at random across the sky. Many stars form in close pairs and as they evolve they can exchange matter, causing them to evolve in quite different ways including producing pairs of neutron stars that eventually merge creating the heaviest elements, including gold. We will end by showing how the material we see around us has been cycled through several generations of stars.

5 The Sun a detailed study of a Star and its effect on the Earth
The Sun is the closest star to us and is responsible for the Earths climate. It is a normal star, which is slowly converting the hydrogen in its core to helium. It is now about 30% brighter than when it was born. It has sunspots that come and go every 11 years and over the centuries these cycles vary in strength. We will see how the Sun works and look at the evidence that it affects our climate on both short and long time scales as well as producing dramatic auroral displays.

6 Solar Systems; Ours and Others 1
After considering the origin of our solar system we will take a tour through its wide variety of environments, ranging from the dry cold deserts of Mars, the lead melting environment of Venus and the icy wastes of Pluto.

7 Solar Systems; Ours and Others 2
We will continue our tour of the objects in our Solar System before seeing how it compares with the more than 5000 planetary systems found around other stars.

8 Asteroids and Earth impacts
On average, every 5,000 years an object, large enough to make a crater 1 km in diameter, strikes the Earth. Some of these impactors are derived from comets and some from asteroid collisions. We will look at past impacts, including that of 1906 that demolished 40 million trees, which may be related to even larger events in the last 10,000 years. We will examine the origin of these impacts and see what is being done to predict and prevent them.

9 How we know what we know or a visit to the Institute of Astronomy
If possible we will make a visit to the Institute of Astronomy. If this is not possible we will look in more detail at some of the instruments, telescopes and techniques used to interpret the signals we receive from the universe, which now include electromagnetic radiation from X rays to Radio waves, gravitational waves and neutrinos.

10 Are we Alone?
In previous lectures, we have seen that we live in a Universe perfectly suited to our existence. On Earth, life is found in rocks, ice and boiling water, suggesting it would be impossible to destroy, before the Sun becomes a red giant. Yet space is silent, suggesting, that though simple life may be common, technologically advanced life might be very rare. We will present the evidence, then take a closer look at the development of life on Earth. We will consider how to detect life and in particular intelligent life elsewhere in the Universe and use the Frank equation to predict the probability that there is intelligent life elsewhere and if not why this might be.

Learning outcomes

The learning outcomes for this course are:
1. To have a deeper understanding of the world around us;
2. To better understand media reports of new astronomical discoveries;
3. To have a broader perspective of our own significance and possible future, within in the context of the Universe.

Required reading

There is no required reading as the course is self-contained.

Typical week: Monday to Friday

Courses run from Monday to Friday. For each week of study, you select a morning (Am) course and an afternoon (Pm) course. The maximum class size is 25 students. 

Courses are complemented by a series of daily plenary lectures, exploring new ideas in a wide range of disciplines. To add to the learning experience, we are also planning additional evening talks and events.

Evaluation and Academic Credit 

If you are seeking to enhance your own study experience, or earn academic credit from your Cambridge Summer Programme studies at your home institution, you can submit written work for assessment for one or more of your courses. 

Essay questions are set and assessed against the University of Cambridge standard by your Course Director, a list of essay questions can be found in the Course Materials. Essays are submitted two weeks after the end of each course, so those studying for multiple weeks need to plan their time accordingly. There is an evaluation fee of £75 per essay.

For more information about writing essays see Evaluation and Academic Credit.

Certificate of attendance

A certificate of attendance will be sent to you electronically after the programme.