PlanetPol was a ground-based, high sensitivity
polarimeter
A polarimeter is a scientific instrument used to measure the angle of rotation caused by passing polarized light through an optically active substance.[William Herschel Telescope
The William Herschel Telescope (WHT) is a optical/near-infrared reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain. The telescope, which is named after William Herschel, ...]
on the island of
La Palma
La Palma (, ), also known as ''La isla bonita'' () and officially San Miguel de La Palma, is the most north-westerly island of the Canary Islands, Spain. La Palma has an area of making it the fifth largest of the eight main Canary Islands. The ...
in the
Canary Islands
The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...
,
Spain
, image_flag = Bandera de España.svg
, image_coat = Escudo de España (mazonado).svg
, national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond")
, national_anthem = (English: "Royal March")
, i ...
that has now been decommissioned. It was the most sensitive astronomical visual polarimeter ever built in fractional polarisation, a mantle that since its decommissioning now belongs to
HIPPI. Although the device could be used for a wide range of astronomy, its primary use was the
detection of extrasolar planets.
Results
PlanetPol did not discover any extrasolar planets, however it was used to provide upper limits to planetary albedos in the known
55 Cnc and
τ Boo planetary systems. Observations with the polarimeter in the Canary Islands, which are affected by dust from the Sahara, also identified airborne dust as a source of polarization within our atmosphere. Additionally, PlanetPol provided measurements of the polarization of a few dozen nearby stars, which were later combined with southern hemisphere measurements from PlanetPol's successor, HIPPI, to provide information about the nature of those stars and the distribution of the interstellar medium.
References
Exoplanet search projects
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