An introduction to exoplanets
An introduction to exoplanets

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

An introduction to exoplanets

Week 4: You’re in my light – transits

Introduction

Last week you learned how astronomers detect exoplanets by measuring the wobble of their stars. This week you will learn about a different technique for spotting them – waiting for them to pass in front of, or transit, their parent stars. You’ll start off by looking at planets that transit in our own Solar System, and then move on to exoplanet detection.

Watch this video in which Carole Haswell talks about what you will be doing this week.

Download this video clip.Video player: boc_exo_1_video_week4_carole_upload.mp4
Skip transcript

Transcript

Carole Haswell:
Now, you’re going to study one of the most beautifully simple techniques in 21st century astrophysics, the transit method for detecting and measuring the size of exoplanets. I love this so much that some of the early results prompted me to completely redirect my own research to study exoplanets instead. I wrote a book called Transiting Exoplanets, which was published in 2010. And I’ve used telescopes including the Hubble Space Telescope to study them.
This week, you’ll learn a lot more about transits and enough about stars to be able to appreciate how our knowledge of stars helps us to measure and work out the properties of their planets. Telescopes are obviously important tools for astronomy. What may be less obvious is the importance of calculus.
Calculus is a branch of maths, and it’s no coincidence that it was invented by the first person to work out the rules of gravity. This week, you’ll see a cartoon, which beautifully illustrates how calculus works. I hope you enjoy it.
Finally, we’ll bring it all together. You’ll see how we know the size of thousands of individual exoplanets even though we can’t see them.
End transcript
 
Interactive feature not available in single page view (see it in standard view).

By the end of this week, you will be able to:

  • state which planets in the Solar System are observed to transit the Sun, and explain why
  • outline how transits can be used to identify exoplanets and measure the size of stars and planets
  • state the relationship between radius and cross-sectional area for a sphere
  • show you understand the size ratio between the Sun, Jupiter and Earth
  • describe the relationship between transit depth and the ratio of radii of the planet and star (Rp /Rstar)2.
EXO_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371