Department of Physics AstroLab

Studying Exoplanets from Transit Light Curves

Project Aims

  • to measure the light curve of extasolar planets, the transit depth and duration (and uncertainties).
  • to determine the characteristics of the host star (colours, type and size) from BVR-band photometry.
  • combine the transit depth and duration with the period and properties of the star to determine the basic characteristics of the planet and star-planet system.

Project Notes

  1. Learn how to use the telescope and CCD system efficiently

    • Attend the observing training sessions
    • Review the L1 User's Guide material to refresh your understanding of the apparent movement of objects in the night sky
    • Study the provided reference material on the telescope, CCD and software

  2. Research background material

    • Understand the aims of the project
    • Study the Web-based information linked from the provided References page
    • Revise the material covered in the "Observational Techniques" part of Level-2 "Stars and Galaxies" module
    • Read Chapter 8 (Photometry) of "The Handbook of Astronomical Image Processing" by Berry and Burnell
    • Review the V-band filter characteristics
    • Review your understanding of the photometry errors of objects on CCD images (see e.g. John Simonetti's short article (local copy)
    • appreciate the points listed on the How to get good photometric data page
    • Search out additional sources of information

  3. Plan your project

    • Study the published work on exoplanets and exoplanet transits
    • Idenitfy suitable exoplanet transit events that are suitable for observation. These can be identified from
    • Perform some test observations with the telescopes to measure the exposure time required for stars of various magnitudes.
    • Download a 30'x30' DSS image centred on your targets star and decide on the best field position in order to include the comparison stars in your exposures.
    • Search out information on your comparison stars. e.g. via SIMBAD
    • Plan your project write-up; consult the online DUO Report Format Guide and Marking Criteria

  4. Write-up the "Introduction and Background" sections of your project

  5. Explore the provided software

    • Understand and test the provided software for measuring the relative brightnesses of stars on your CCD images: are the quoted errors reasonable?
    • Identify a suitable method for measuring the duration and depth of the transit.
    • Explore the random and systematic uncertainties in the data

  6. Make observations of exoplanet transits, as the weather permits, during the term (and request ocassional observations with the pt5m on La Palma)

    • Measure the relative brightness of the variable star using the provided software. You can automate this by developing a short script.
    • Write-up your results and conclusions

  7. Photometric zero-point calibration

    • Determine the apparent magnitudes of the comparison star(s) in your variable star field via the UCAC4 catalog and hence determine the zero-point calibration
    • Estimate the uncertainty of your zero-point calibration

  8. Determine characteristics of the star--planet systems by examining the colours of the star, the shape of light-curve, the transit depth.

    • Determine whether there are any significant fluctuations during the transit which might be explained by the planet crossing sun-spots.
    • Write-up your conclusions
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