Cassel Sloan


Presented at the Astronomy Club of Augusta meeting

at Augusta State University 

on July 22, 2005



I.  What are Exoplanets?

•      Exoplanets are planets that have been found around stars other than the sun.

•      There are currently 161 Exoplanets around 137 stars known.


II. Ways to find exoplanets

•      Pulsar timing

•      Astrometry

•      Radial velocity

•      Gravitation microlensing

•      Transit method

•      Circumstellar disks

•      Direct observation


Pulsar timing

•      Pulsar timing uses anomaly in timing in the pulsing of pulsars to find companions

•      This method was the first to find planets.



•      Astrometry tries to detect an occolation in the proper motion of a star.

•      Astrometry is the first method used to try to find planets.

•      Due to limitations of current equipment, no planets have been found by astrometry.


Radial velocity

•      Radial velocity uses the Doppler effect to look for a planet’s pull on a star.

•      This method is the one that has found the most planets.


Gravitational microlensing

•      Gravitational microlensing uses gravity’s affect on light to find planets.

•      Gravitational microlensing main advantage is that it can detect Earth sized planets, however it only happens by chance and can not be repeated.


Transit method

•      The transit method uses the dimming of star by planets going in front of it.



Circumstellar disks

•      Circumstellar disks are dust clouds around a star which a planet can distort.

•      This method requires space telescopes since the atmosphere absorbs most of the light from the dust clouds.


Direct observation

•      Direct observation tries to see a planet directly.

•      The stars light usually far outshines the planet.

•      There may be two planets found by this method.



III. Future of exoplanet search

•      There are three missions to look for exoplanets in the future.

•      Space Interferometry Mission (SIM)

•      Terrestrial Planet Finder (TPF)

•      Darwin


Space Interferometry Mission

•      The Space Interometry Mission will use optical interometry to exactly measure the proper motion of a star.

•      This should be exact enough to find planets by astrometry.


Terrestrial Planet Finder

•      The Terrestrial Planet Finder is a NASA proposal to find planets

•      There are two architectures:  multiple telescopes in formation to cancel out the light from the star and one big telescope with special optics to decrease the light from the star.



•      Darwin is a proposal European Space Agency mission that will use six 1.5 meter telescopes in formation to cancel out the light from a star.

•      This is like part of the Terrestrial Planet Finder and the two projects may merge.

First Exoplanet

•      Aleksander Wolszczan found the first exoplanet around the pulsar PSR 1257+12.

Fartherest exoplanet

•      An exoplanet was found in an unknown galaxy by microlensing the quasar Q0957+561.

•      Its mass is 3 Earths.




•      In 2001 the planet HD 209458b’s atmosphere was measured by the Hubble.

•      The atmosphere has hydrogen, carbon, oxygen, and sodium.


Planet eating stars

•      In 2001, a star was found that had the remnants of planets in its atmosphere.


Oldest Planet

•      The oldest planet found is 13 billion years old and is in the M4 star cluster.



•      Wikipedia