The Exoplanets Group at Chabot Space & Science Center conducts weekly observing sessions using Chabot telescopes in an effort to verify discoveries of extra-solar planets (exoplanets).
How Is It Done?
Working from prioritized star lists provided by the Lick Observatory group (TransitSearch.org), Chabot's Exoplanets Group captures images of selected candidate stars, along with nearby "reference" stars, seeking to detect any reduction in the brightness of the candidate star that may be caused by a planet crossing in front of it ("transiting").
Images are taken at different wavelengths and processed using associated dark- and flat-field images to remove camera-related effects that introduce errors. The software package MaxIM DL is used to perform the processing.
The photometric program AIP4Win is used to measure the brightness of stars in the processed images. The output consists of a table of the photometric instrumental magnitudes for all the measured stars, along with CCD camera statistics that indicate the quality of the measurements.
Further analysis of atmospheric extinction is applied and the results are sent to the Los Alamos National Laboratory as part of their program on atmospheric aerosols and particulates in global warming modeling.
The tabular star data is then analyzed by taking the difference between the target star and similar nearby stars (for comparison) as a function of time and wavelength. Several comparison stars are examined to ensure that none of them are variable stars.
Graphic plots of the data are prepared, reviewed by the ExoPlanets team at Chabot, and if the results look good, they are sent on to the Lick Observatory team.
Example of the light curve plot of a star during the transit of its planet - the star's brightness increases (returns to normal levels) as its planet passes out of transit
The Lick team assembles the photometric light curves from all contributing exoplanets groups around the world to piece together a complete transit light curve.