The Search for Exoplanets

An exoplanet is a planet orbiting a star outside of our solar system The first proven exoplanet was 51 Pegasi, announced in To date, 2011 planets have been identified.

Ways of Discovering Exoplanets Stars are so much bigger and brighter (+1,000,000x) than planets, it is nearly impossible to just point a telescope at a star and see its planets

Radial Velocity As a planet goes around its star, they both orbit the same center of gravity. The gravity of the planet cause the star to wobble. This back forth wobble is detectable as a back and forth redshift and blueshift of the star

Radial Velocity only works on very large planets, bigger than Jupiter. It also appears to be most effective if the planet is very close to the star. 51 Pegasi, the first exoplanet, is 3 times closer to its star than Mercury. As of December 2015, 622 exoplanets have been discovered using Radial Velocity

Imaging Recently, telescopes have made huge technological advances. Telescopes and interferometers (a bunch of small telescopes mimicking a giant one) have become advanced enough to take actual pictures of exoplanets. 63 planets have been discovered by imaging.

Gravitational Microlensing Gravity from a star or planet causes light to bend. If a star has a planet going around it, this “lensing” will cause it to periodically become brighter and dimmer. This technique is only being done by the University of Warsaw in Poland. They have discovered 42 exoplanets

Pulsar Timing When very massive stars run out of nuclear fuel, they explode, leaving a small dense core, called a neutron star. These remnants usually spin, sending out “blips” of radiation, this is called a “pulsar”. A planet can form out of the debris of the dead star, which can gravitationally alter the spin of the pulsar, which can be measured. 23 exoplanets, with a pulsar as the central star, have been discovered.

Transit Photometry The total light from a star can be measured. If you continuously watch a star, and note that it gets dimmer periodically, that is caused by a planet blocking the light planets have been discovered.

The Kepler space telescope (launched 2009), is looking at a tiny patch of sky with powerful enough optics to detect these miniscule differences in light 1020 planets have been confirmed.

Kepler is looking at 150,000 medium to small stars for changes in the light curve of the star. TIME BRIGHTNESS 0 0 If you were watching a star, and a planet passed in front….what would happen to the light curve?