exoplanet eclipse light curve

An exoplanet eclipse light curve (or exoplanet transit light curve) is the light curve of the star's light over the course of the exoplanet's transit, passing in front of its host star, the star's brightness plotted against time. A transiting planet can be detected by the dip in the light recorded in such a light curve. Often light curves are recorded that include the planet's full orbit, recording both the transit (primary eclipse) and the secondary eclipse, which can offer considerable information about the planet:

• The transit's amount of reduction is related to the relative sizes of the planet and star, and to the degree that the size of the star can be determined, the planet's can as well.
• At the beginning and end of the transit, the increase/decrease of light reveals information about the orbital inclination.
• Viewing the transit with filters or with a spectrograph and comparing with the starlight before/after the transit reveals photometry and transmission spectroscopy information about the planet's atmosphere.
• The secondary eclipse offers a very clear view of the star's own photometry and spectrography, and the changes entering and exiting it offer information about the albedo and temperature of the day-side of the planet. Differences between the light before and after the secondary eclipse offer information regarding the warmest location on the planet in relation to its noon, offering information about its rotation and winds.
• When the planet is in position to reflect the star's light, photometry or spectrography of the light reflected can be determined, revealing characteristics of the material on the surface of the planet.

Getting spectrographic data requires differential spectroscopy, comparing the spectrum at different points in the planets orbit including before, during and after the eclipse. This use of spectroscopy is known as occultation spectroscopy. Photometric data about the planet is similarly obtained. Spectrography requires telescope time and a certain amount of light and in some cases photometry is all that is practical.