Exoplanet Transits

Introduction

Although there are several methods to detect planets around other stars (e.g. Pulsar Timing, Doppler Measurements, Astrometry), the Kepler Mission has discovered many such objects using the "transit method". If the orbit of the planet around the star is lined up just right, once an orbit the planet passes in front of the star and dims the starlight we receive. By monitoring the starlight and looking for periodic "dips", we can not only detect planets, we can learn a lot about them!

The detailed shape of a transit light curve depends on the type of star, the planet's size, and its orbital period, size, and inclination. By carefully analyzing the transit light curve data, we can figure out how big a planet is, how far it is from its star, and whether or not it might be habitable - capable of sustaining life.

Research Project

For certain types of stars, planets in the hapitable zone will be "tidally locked". Just like our Moon always faces the Earth with the same side, these planets will always have the same side facing their star. A colleague, Dr. Eric Korpela of the Space Sciences Laboratory at Berkeley, wondered what would happen if an extraterrestrial civilization were inspired to illuminate the dark side of such a planet, perhaps with a fleet of orbiting, steerable mirrors to redirect starlight. Such a fleet of mirrors would affect the transit light curve for such a planet.

Dr. S., Dr. Korpela, and a UW-L undergraduate student have simulated the effects of simple fleets of mirrors, predicting their impact on the transit light curves. We assumed the mirrors would illuminate the dark side to the same level as the day side.

In the animated GIF movie below, the left panel shows a transiting planet surrounded by a simple fleet of mirrors, resulting in the solid light curve in the bottom graph. The right panel is for a single planet without mirrors that would produce a transit of similar depth, producing the dashed curve.

This is also available as an AVI movie , Quicktime movie, or MP4 movie .

Unfortunately, the effects of such a fleet of mirrors are too small to be observable with Kepler data, but future telescopes will be more sensitive. At that time, students may have the opportunity to search for these effects in the transit light curves of exoplanets.

Online Exoplanet / Transit Resources

If any of the tutorial links have vanished, you can try finding them through the "Wayback Machine" Internet Archive.
NASA Planetquest's description of Methods of Planet Detection
Wikipedia's page on Methods of Detecting Exoplanets
Description of the Transit Method of Exoplanet detection
Kepler's How Kepler Finds Planets
NAAP Transit Simulator

Back to Website for Dr. Shauna Sallmen

Last updated August, 2014