Tuesday, October 20, 2009

Thirty-Two More for HARPS

This week--October 19 through 23--in Porto, Portugal, the European Southern Observatory (ESO) is jointly holding an international conference with Centro de AstrofĂ­sica da Universidade do Porto (CAUP), a private astronomical association of the University of Porto. The topic of the conference is the progress of exoplanet studies--exoplanets being extrasolar planets, or planets orbiting in other star systems.

On Monday, those attending received a report on the first five years of operation of the High Accuracy Radial Velocity Planet Searcher (HARPS), the spectrograph used on ESO’s 3.6 meter telescope. The HARPS team was excited to announce that in its first five years of operation, HARPS had discovered 75 exoplanets in 30 different planetary systems. This number included the announcement of 32 brand new exoplanets discovered by HARPS.

The precision of HARPS has allowed astronomers to search for small planets, those with a mass of a few times that of the Earth--known as super-Earths and Neptune-like planets. To date, HARPS has discovered 24 of the 28 planets known to have masses below 20 Earth masses. Most of the new low-mass planets reside in multi-planet systems, with up to five planets per system.

First installed in 2003, HARPS is able to measure the back-and-forward motions of stars by detecting small changes in a star’s radial velocity--as small as 3.5 km/hour. This precision is crucial for the discovery of exoplanets and the radial velocity method, the most prolific method for searching for exoplanets. The radial velocity method is one which detects small changes in the radial velocity of a star as it wobbles slightly under the gentle gravitiational pull from an unseen orbiting planet.

The achievement of the HARPS observing teams has increased the number of known low-mass planets by 30 percent. As of this latest count, there are roughly 400 known exoplanets. To learn more about the discoveries of HARPS and about exoplanets in general, check out these links:

European Southern Observatory (ESO) October 19 News Release and Images
http://www.eso.org/public/outreach/press-rel/pr-2009/pr-39-09.html

European Southern Observatory (ESO)
http://www.eso.org/

Extrasolar Planets Encyclopaedia
http://exoplanet.eu/

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