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Indirect Observations of Exo-Planets from ULO

The Celestron C14 and SBIG STL6303E CCD camera have been commissioned over the summer, and are ready for use in student teaching in the 2006 autumn term.

Outside teaching hours a UCL 4th-year project student, Dan Smith, and project supervisor, Dr. Steve Fossey , are using the telescope and CCD to observe the transits of extrasolar planets.

Observations of the star HD189733 were taken in July and August 2006 during two transit events; a sequence of several hundred images were obtained on each night.


HD189733 star field HD189733 star field

Photometry of the star's brightness variations, measured relative to other stars in the field, reveals how the star's light fades very slightly (a few percent) while its planetary companion passes in front of it as viewed from Earth.


Transit light curve of HD189733 on 8th August 2006. Transit light curve of HD189733 on 8th August 2006.

The planet orbits its host star in just over 2 days, and the total transit lasts just under 2 hours. Modelling of the light curve can provide estimates of the planetary radius: the latest results on this system indicate the exoplanet is about 15 percent bigger than Jupiter, while the star is about 20 percent smaller than the Sun. Such observations are very important for determining the nature of such planets - so-called "hot Jupiters" - and addressing detailed questions concerning their origin in exo-planetary systems.

Links: The Extrasolar Planets Encyclopaedia