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The relativistic Universe

If you are interested in using quantitative physical methods to understand relativistic and high-energy processes in the Universe, and already have a good background in OU level 2 maths, physics and astronomy, then this is the module for you. This module comprises three parts that present, in turn, the theoretical basis for modern cosmology, described by Einstein’s special and general theories of relativity; cosmological observations of the local and distant Universe that are used to understand its structure and evolution; and high-energy phenomena in the Universe including interacting binary stars, active galactic nuclei and gamma-ray bursts.

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Module code


  • Credits measure the student workload required for the successful completion of a module or qualification.
  • One credit represents about 10 hours of study over the duration of the course.
  • You are awarded credits after you have successfully completed a module.
  • For example, if you study a 60-credit module and successfully pass it, you will be awarded 60 credits.
Study level
Across the UK, there are two parallel frameworks for higher education qualifications, the Framework for Higher Education Qualifications in England, Northern Ireland and Wales (FHEQ) and the Scottish Credit and Qualifications Framework (SCQF). These define a hierarchy of levels and describe the achievement expected at each level. The information provided shows how OU module levels correspond to these frameworks.
3 10 6
Study method
Distance Learning
Module cost
See Module registration
Entry requirements
See Entry requirements

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What you will study

This module will give you a good understanding of relativistic astrophysics and cosmology, including both their theoretical underpinnings and their observational consequences. It is a mathematical module that builds on skills and concepts you will have developed by studying maths, physics and astronomy at a level equivalent to OU level 2 modules. The module makes full use of tools in the OU’s Virtual Learning Environment (VLE) and internet-based resources are used throughout.

Part 1, Relativity, Gravitation and Cosmology, is based around a book which allows you to develop an understanding of special and general relativity and apply this knowledge to the structure and evolution of the Universe as a whole. You will learn how a metric is used to describe mathematically a space-time (including unrealistic two- and three-dimensional models, as well as possibly more realistic four-dimensional space-times). You will then develop an understanding of Einstein’s theory of general relativity as a metric theory of gravity, including the role of the Einstein field equations, some examples of specific solutions and the current status of a range of ‘tests’ of general relativity. Finally you will learn about the existence, nature and implications of cosmological solutions to the Einstein field equations subject to the assumption of large-scale homogeneity and isotropy (including the effect of a cosmological constant/uniform dark energy density).

Part 2, Observational Cosmology, is based around a book which allows you to learn about the various observational techniques and measurements that provide a picture of the structure and evolution of the Universe on the largest scales. You will acquire knowledge and understanding of statistical cosmological techniques as well as current relativistic cosmological models and the observational evidence for them. You will learn about the bulk properties of local and distant galaxies and the physical inferences that can be made from them.

Part 3, Extreme Environment Astrophysics, is based around a book which focuses on the role of accretion in the presence of strong gravitational fields and the physics of relativistic objects, including white dwarfs, neutron stars and black holes. You will learn the physics of the main high-energy phenomena arising in compact and accreting systems as well as the main physical processes occurring in, and parameters of, accreting systems at small and large scales. You will study the astrophysics of interacting binary stars, active galaxies, accretion discs, their outbursts and outflows, and gamma-ray bursts, and will also discover the methods used in the measurement and characterisation of accretion flow properties. Your study of this part will allow you to develop basic concepts of hydrodynamics, thermodynamics and plasma physics.

Outside the UK

This module is suitable for study outside the UK.

Teaching and assessment

Support from your tutor

Throughout your module studies, you’ll get help and support from your assigned module tutor. They’ll help you by:

  • Marking your assignments (TMAs) and providing detailed feedback for you to improve.
  • Guiding you to additional learning resources.
  • Providing individual guidance, whether that’s for general study skills or specific module content.
  • Facilitating online discussions between your fellow students, in the dedicated module and tutor group forums.

Module tutors also run online tutorials throughout the module. Where possible, recordings of online tutorials will be made available to students. While these tutorials won’t be compulsory for you to complete the module, you’re strongly encouraged to take part.


The assessment details for this module can be found in the facts box above.

You will be expected to submit your tutor-marked assignments (TMAs) online through the eTMA system unless there are some difficulties which prevent you from doing so. In these circumstances, you must negotiate with your tutor to get their agreement to submit your assignment on paper.

You will, however, be granted the option of submitting on paper if typesetting electronically or merging scanned images of your answers to produce an electronic TMA would take you an unacceptably long time.

There will be a mixture of online interactive computer-marked assignments (iCMAs) and short tutor-marked assignments (TMAs), with a total workload equivalent of three full TMAs.

Both the iCMAs and TMAs will focus strongly on learning through practice rather than on assessment. The feedback you receive on your answers will help you to improve your knowledge and understanding of the study material and to develop important skills associated with the module. The feedback on the iCMAs will be instantaneous and hints will be given so that you can refine any incorrect answers. Although your scores on all these assignments will not contribute directly to your module grade, they form an essential part of the learning process and you will be required to submit a proportion of them to complete the module.

Your overall module grade will be based on two examinable components. The first comprises an extended written assignment for Part 2 of the module which you submit at the end of this study period. The other is an end-of-module written examination based on Parts 1 and 3.

Future availability

The relativistic Universe (S383) starts once a year – in October.

This page describes the module that will start in October 2022.

It will start for the last time in October 2022. We plan to replace The relativistic Universe (S383) with a new module – Cosmology and the distant Universe (S385) – that will start for the first time in October 2023.


As a student of The Open University, you should be aware of the content of the academic regulations which are available on our Student Policies and Regulations website.

    Course work includes:

    4 Tutor-marked assignments (TMAs)
    4 Interactive computer-marked assignments (iCMAs)
    No residential school

    Entry requirements

    The relativistic Universe (S383) is an OU level 3 module. It builds on study skills and subject knowledge acquired at OU levels 1 and 2.

    We’ve designed S383 to follow these four modules:

    These parts are especially significant:
    • ‘Galaxies and cosmology’ in S284
    • ‘Ordinary and partial differential equations’ and ‘Matrices’ in MST224.

    Check you’re ready for S383.

    Talk to an advisor if you’re not sure you’re ready.

    Preparatory work

    As a result of taking the Are you ready for ...? test, you may find that you need to study a further module or modules before embarking on S383. If this is not possible, you may choose to spend time studying relevant background material. For this purpose we have produced a ‘Book 0’ for S383 (and the related module S382) entitled An introduction to astrophysics and cosmology, which you may download as a PDF. This document covers the recommended background knowledge and skills that we expect students to possess before embarking on S383. If you need to study all the maths, physics and astronomy background contained within this Book 0, we estimate it will require about 40–60 hours of study. It is not a replacement for taking the appropriate OU level 2 modules, but it will serve to fill the gaps in your knowledge in many cases.


    Start End England fee Register
    01 Oct 2022 Jun 2023 -

    Registration now closed

    October 2022 is the final start date for this course. For more information, see Future availability.

    Additional Costs

    Study costs

    There may be extra costs on top of the tuition fee, such as set books, a computer and internet access.

    If your income is not more than £25,000 or you are in receipt of a qualifying benefit, you might be eligible for help with some of these costs after your module has started.

    Ways to pay for this module

    Open University Student Budget Account

    The Open University Student Budget Accounts Ltd (OUSBA) offers a convenient 'pay as you go' option to pay your OU fees, which is a secure, quick and easy way to pay. Please note that The Open University works exclusively with OUSBA and is not able to offer you credit facilities from any other provider. All credit is subject to status and proof that you can afford the repayments.

    You pay the OU through OUSBA in one of the following ways:

    • Register now, pay later – OUSBA pays your module fee direct to the OU. You then repay OUSBA interest-free and in full just before your module starts. 0% APR representative. This option could give you the extra time you may need to secure the funding to repay OUSBA.
    • Pay by instalments – OUSBA calculates your monthly fee and number of instalments based on the cost of the module you are studying. APR 5.1% representative.

    Joint loan applications

    If you feel you would be unable to obtain an OUSBA loan on your own due to credit history or affordability issues, OUSBA offers the option to apply for a joint loan application with a third party. For example, your husband, wife, partner, parent, sibling or friend. In such cases, OUSBA will be required to carry out additional affordability checks separately and/or collectively for both joint applicants who will be jointly and severally liable for loan repayments.

    As additional affordability checks are required when processing joint loan applications, unfortunately, an instant decision cannot be given. On average the processing time for a joint loan application is five working days from receipt of the required documentation.

    Read more about Open University Student Budget Accounts (OUSBA).  

    Employer sponsorship

    Studying with The Open University can boost your employability. OU courses are recognised and respected by employers for their excellence and the commitment they take to complete. They also value the skills that students learn and can apply in the workplace.

    More than one in ten OU students are sponsored by their employer, and over 30,000 employers have used the OU to develop staff so far. If the module you’ve chosen is geared towards your job or developing your career, you could approach your employer to see if they will sponsor you by paying some or all of the fees. 

    • Your employer just needs to complete a simple form to confirm how much they will be paying and we will invoice them.
    • You won’t need to get your employer to complete the form until after you’ve chosen your module.  

    Credit/debit card

    You can pay part or all of your tuition fees upfront with a debit or credit card when you register for each module. 

    We accept American Express, Mastercard, Visa and Visa Electron. 

    Mixed payments

    We know that sometimes you may want to combine payment options. For example, you may wish to pay part of your tuition fee with a debit card and pay the remainder in instalments through an Open University Student Budget Account (OUSBA).

    Please note: your permanent address/domicile will affect your fee status and therefore the fees you are charged and any financial support available to you. The fees and funding information provided here is valid for modules starting before 31 July 2023. Fees normally increase annually in line with inflation and the University's strategic approach to fees. 

    This information was provided on 26/09/2022.

    What's included

    You'll have access to a module website, which includes:

    • a week-by-week study planner
    • course-specific module materials
    • audio and video content
    • assignment details and submission section
    • online tutorial access.

    You'll also be provided with three printed module books and a DVD-ROM.

    You will need

    Basic scientific calculator.

    Computing requirements

    You’ll need broadband internet access and a desktop or laptop computer with an up-to-date version of Windows (10 or 11). Any macOS is unsuitable with this module.

    Any additional software will be provided or is generally freely available.

    To join in spoken conversations in tutorials, we recommend a wired headset (headphones/earphones with a built-in microphone).

    Our module websites comply with web standards and any modern browser is suitable for most activities.

    Our OU Study mobile app will operate on all current, supported versions of Android and iOS. It’s not available on Kindle.

    It’s also possible to access some module materials on a mobile phone, tablet device or Chromebook. However, as you may be asked to install additional software or use certain applications, you’ll also require a desktop or laptop as described above.

    If you have a disability

    The OU strives to make all aspects of study accessible to everyone and this Accessibility Statement outlines what studying S383 involves. You should use this information to inform your study preparations and any discussions with us about how we can meet your needs.

    To find out more about what kind of support and adjustments might be available, contact us or visit our Disability support website.