     material:
       title: "Kepler-90"
       text: """
-        The third confirmed exoplanet discovered by volunteers on Planet Hunters is in a system known as Kepler-90 and now has the designation Kepler-90h. This system already had six confirmed exoplanets, but the discovery of the seventh buy Planet Hunters volunteers made it the most populous planetary system known, apart from our own. The red circle in the diagram above shows the orbit of Kepler-90h in the system.
+        The third confirmed exoplanet discovered by volunteers on Planet Hunters is in a system known as Kepler-90 and now has the designation Kepler-90h. This system already had six confirmed exoplanets, but the discovery of the seventh buy Planet Hunters volunteers made it the most populous planetary system known, apart from our own. The red circle in the diagram above shows the orbit of Kepler-90h in relation to the other planets in the system.
         """
       figure: "./images/mini-course/11-kepler90.png"
       figure_credits: ""

      title: "What can we learn from a lightcurve?"
      text: """
        <p>
          A lightcurve can tell us a lot about a planetary system. Firstly, it gives us is an estimate of the size of the planet. The larger the planet is in relation to the star, the more light is blocked by the planet and the deeper the transit. So the transit depth, d, is proportional to the radius of the planet, Rp:
        </p>
        <div style=\"text-align: center;\">
          <img style=\"width: 75px; padding: 10px\" src=\"./images/mini-course/keplers-third-law.png\"/>
        </div>
        <p>
          A planet the size of Jupiter will cause a 1% dip in the brightness of a star the size of our Sun. An Earth-sized planet would only cause a 0.1% dip, making it much harder to detect! However, if the star is much smaller than our Sun, which the majority of the stars in our galaxy are, the dip in light will be larger.
        </p>
      """
      figure: "./images/mini-course/light-curve-period.png"
      figure_credits: "Image credit: NASA"
  }
  {
    course_number: 4
    material:
      title: "What can we learn from a lightcurve?"
      text: """
        <p>
          If we observe multiple transits at equally spaced intervals then we know they are caused by a single planet and we have a measurement of its orbital period, as it is just the time interval between each transit. Astronomer Johannes Kepler showed that orbital period,P, is proportional to orbital separation, a:
        </p>
        <div style=\"text-align: center;\">
          <img style=\"width: 75px; padding: 10px\" src=\"./images/mini-course/transit-depth.png\"/>
        </div>
        <p>This means that by observing multiple transits of the same planet we can determine how far away it is from its host star.</p>
        """
      figure: "./images/mini-course/lightcurve-transit-depth.png"
      figure_credits: ""
  }
  {

    material:
      title: "How else can we discover planets? - Pulsar Timing"
      text: """
        The first ever confirmed exoplanet was not actually discovered orbiting a Sun-like star. It was found around an object known as a 'pulsar'. Pulsars are the extremely dense, rapidly spinning cores of dead stars which have beams of radiation that sweep out like an interstellar lighthouse. The rotation-rate of pulsars is extremely reliable and can be measured to very high accuracy. However, if a planet is in orbit, its gravitational pull on the pulsar will manipulate the rotation-rate in a way that allows its existence to be inferred.
        """
      figure: "./images/mini-course/slide-19.gif"
      figure_credits: "Image credit: Cambridge Physics"
