         <p>The way that the lightcurves are produced means that sometimes light from other stars (not just the target star) is included. This is called ‘blending’, and it leads to the light of the target being diluted. This means if the target is an eclipsing binary, the dips in light may appear small enough to mimic a planet. </p>
         <p>Also, if one of the background stars is actually an eclipsing binary it may appear like there are smaller transits occurring on the target star, when in fact there is nothing there at all. The right-hand panel of the diagram below shows an example of this scenario.</p>
         """
-      figure: "missing"
+      figure: "./images/mini-course/slide-7.jpg"
       figure_credits: ""
 
   }

        <strong>THE RADIAL VELOCITY METHOD</strong>
        <p>As a planet orbits a star its gravitational pull moves the star around. Therefore at some points the star is moving towards us (the observer) and at other points it is moving away from us. We can measure the speed of this movement by looking at the spectrum of light from the star. When moving towards us the star’s light becomes more blue, and when moving away its light becomes more red. The faster the star is moving, the more massive the planet. For example, Jupiter moves the Sun at 12.7 m/s (slightly faster than Usain Bolt can run), whereas the effect from Earth is over 100 times smaller, making it much easier to detect larger planets.</p>
        """
      figure: "missing"
      figure_credits: "NASA"

  }

  {
    course_number: 17
    material:
      title: "How else can we discover planets? - Radial Velocity"
      text: """
        The radial velocity method has been used to discover hundreds of exoplanets to date, however it has one major disadvantage; it cannot be used to determine the angle of the planetary system to our line-of-sight, so perhaps we are only seeing a small fraction of the star’s movement? This means that only a minimum measurement of the star’s speed can be calculated, leading to only a minimum possible value for the mass of the exoplanet.
        """
      figure: "./images/mini-course/16-radial-velocity.jpg"
      figure_credits: "NASA"

  }

  {
    course_number: 18
    material:
      title: "How else can we discover planets? - Gravitational Microlensing"
      text: """
        The gravitational field of a star is strong enough to noticeably bend light. When one star passes directly in front of a more distant star as seen from Earth it can bend and focus the light of the distant star causing it to appear brighter for a short period of time. This is known as gravitational microlensing and the closer star is called the lens. If there is a planet orbiting the lens it will sometimes add a noticeable component to the lens effect allowing us to confirm its existence.
        """
      figure: "./images/mini-course/17-micro-lensing.jpg"
      figure_credits: "NASA"

  }

  {
    course_number: 19
    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 in in orbit its gravitational pull on the pulsar will manipulate the rotation-rate in a way that allows its existence to be inferred.
        """
      figure: "missing"
      figure_credits: "NASA"

  }

  {
    course_number: 20
    material:
      title: "How else can we discover planets? - Transit Timing Variations"
      text: """
        In a similar way to pulsar timing, the timing of exoplanet transits can be used to infer the existence of other planets in the same system. If there were just one planet orbiting the star, the time interval between each transit would be exactly the same. However, if there is more than one planet the gravitational pull from other planets will cause regular variations in the time at which the transiting planet actually passes in front of the star. The size of the timing variation is used to measure the mass of the unseen planet.
        """
      figure: "missing"
      figure_credits: "NASA"

  }

  {
    course_number: 21
    material:
      title: "How else can we discover planets? - Astrometry"
      text: """
        As described before for the radial velocity method, stars are pulled around by the gravitation force from their orbiting planets (see animation below). Therefore, if the position of a star can be measured accurately, this movement can be observed and the existence of the planet can be confirmed. These movements are extremely small and to-date very few exoplanet candidates have been discovered in this way, however the recently launch Gaia spacecraft plans to utilise this method as part of its mission.
        """
      figure: "missing"
      figure_credits: "NASA"

  }

        <p>The separation and extreme difference in brightness between exoplanets and their host stars makes it very difficult to image them directly. However, there are a handful of exoplanet candidates  that have been discovered this way. All of them have very large radii and lie in distant orbits.</p>
        <p>Below is an image showing the directly imaged exoplanet candidate orbiting in the debris disk around the star Formalhaut.</p>
        """
      figure: "./images/mini-course/slide-22.jpg"
      figure_credits: "NASA"

  }
