Exoplanets

by

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

• 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

• 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.

Atmosphere

• 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.

Acknowledgements

• Wikipedia