| Astrobiology Australasia | Home | What is Astrobiology? | Highlights | People | Glossary | Links | Books | Publications |
| See also:
Anglo-Australian Planet Search The Ages of Terrestrial Planets
External Links:
|
Searching for Extrasolar Planets - 3 Detecting Terrestrial Planets The methods currently used for detecting extra-solar planets can only detect giant planets, similar in mass to Jupiter and Saturn in our own solar system. Detecting terrestrial planets - planets similar to Earth - is much more difficult. A method of detecting such planets was first suggested by Australian scientist Ron Bracewell in 1978. Bracewell's proposal was to use an infrared nulling interferometer in space. Scientists at NASA and its European counterpart ESA are now preparing designs for space missions to implement Bracewell's concept, the Terrestrial Planet Finder or TPF (NASA) and the Darwin/IRSI project (ESA).
Both TPF and Darwin are envisaged as arrays of a number of free flying space telescopes arranged in a precisely controlled formation and combining their light in a central station. Searching for Life These space missions aim to do more than just find such planets - it should also be possible to determine whether they have developed life. Life on Earth dramatically transformed the atmosphere of the planet when the development of oxygenic photosynthesis transformed the original atmosphere of mainly carbon dioxide into the oxygen atmosphere we have today. TPF and Darwin will be able to measure the infrared spectrum of a planet and thus determine if their atmospheres have been similarly transformed by the presence of life. |
The
fundamental difficulty in detecting such a planet is that of distinguishing
its light from that of the star which can be a billion times brighter.
By going to infrared wavelengths at which the radiation from the planet
is significant this factor of a billion can be reduced substantially, but
the key to the concept is the use of a nulling interferometer. This is
two or more telescopes arranged such that destructive interference
of light removes most of the light from the star while leaving that from
the planet.