New Extrasolar Planet

A group of astronomers from the Canaries and the US have just announced the discovery of a new planet, outside the solar system, that they have called TrES-1. Their paper will be published in Astrophysical Journal Letters but has been on astro-ph since Monday. The planet has about three-quarters the mass of Jupiter although with an orbital period (year) of just over three days, it is certainly much closer to its star than Jupiter is to the Sun.

In this paper two small (10cm) aperture, wide-field (6 degree) telescopes (Stare and PSST), were used to observe the same patch of sky at different times as they were at different longitudes. As planets don't give off their own light - by definition - there are several ways to spot planets around other stars including transits, the Doppler effect and microlensing. Each of these methods detects different types of planet/star. In this case, they used the transit method to watch for a drop in brightness of the star around which the planet orbits.

As anyone who saw the Venus transit will realise, a planet doesn't really cause a very significant drop in the amount of light from a star. Making your equipment very sensitive to changes in brightness can only help so much as the atmospheric seeing can cause a larger changes in brightness (think twinkling). Other than using a telescope in space, a way to get around this is to observe the brightness over time and then 'fold' the data up; basically split the data up into chunks of a specific time and then add all the chunks together. This might seem crazy but it means that if you happen to choose the chunk size to be the same as the orbital period of the planet, the dip in light from the star starts to stand out from the 'noise'. This method is well used in astronomy with many pulsars being found this way.

Posted in astro blog by Stuart on Wednesday 25th Aug 2004 (15:38 UTC) | Permalink
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