An introduction to exoplanets
An introduction to exoplanets

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An introduction to exoplanets

Week 3: Dawn of the exoplanet era


This week you are going to look at your first exoplanet – the first planet ever discovered orbiting another star. That planet is called 51 Pegasi b. You will learn about how the planet was discovered by measuring tiny changes in the properties of the light coming from the star 51 Pegasi, and you will also find out what kind of planet it is.

Watch the following video in which Carole Haswell talks about how the exoplanet era came about.

Download this video clip.Video player: boc_exo_1_video_week3_carole_upload.mp4
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Carole Haswell:
In the 1980s, when I was studying astronomy at the University of Texas, some of my colleagues were looking for planets orbiting around other stars. I thought they were a bit daft. It seemed like such a difficult thing to do. Of course, things have moved on a lot since then, especially technology.
The technology used in astronomy is much more powerful than it was when I first used a professional telescope. In fact, it’s revolutionised our exploration of the universe. Finding exoplanets is now almost routine. And there are hundreds of astronomers around the world finding them and studying them.
You’re going to start this week looking at the first planet found orbiting another main sequence star, a star like our own Sun. This is one of those landmark discoveries which cause us to re-evaluate our own place in the Universe. To me, part of the point of life is to figure out everything we can about where we are and how we fit into the big picture.
To understand how the first exoplanet was found, we need to do a bit of physics. And to understand how we can work out the mass of a planet we can’t even see, we need to do a bit of maths, too. So we’ve made some interactive animations to help you see how things behave.
Like Angry Birds (remember that?) these applications obey the laws of physics and should help you to see how changing things like the mass of a star affects the properties we can measure. Turning it around, it allows us to see how once we’ve measured something, we can work out other things.
In a way, planet hunting has a lot in common with Angry Birds persistence, practise, and learning from your mistakes brings success
End transcript
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By the end of this week, you will be able to:

  • interpret the name of an exoplanet
  • describe the characteristics of 51 Pegasi b
  • explain the radial velocity method for detecting planets using the analogy of a see-saw
  • understand that both light and sound are waves
  • understand how the Doppler shift affects wave properties
  • use the website [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] to find a list of planets discovered by the radial velocity method.

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