Report - School of Physics
Report - School of Physics
Report - School of Physics
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2 The Period 2005–2015<br />
2.1 Ground Observations: 2005–2015<br />
There are many ongoing ground-based surveys. At the time <strong>of</strong> writing, the Planets<br />
Encyclopaedia www page (http://www.obspm.fr/encycl/searches.html) lists as<br />
either ongoing or planned: 18 radial velocity searches, 15 transit searches, 5 microlensing<br />
programmes, 10 imaging/direct detection programmes, 2 radio surveys,<br />
and 3 astrometric efforts. An overview <strong>of</strong> efforts and expected results is given in<br />
this section, with a particular focus on the ESA and ESO contributions.<br />
2.1.1 Radial Velocity Searches<br />
A summary <strong>of</strong> ongoing or planned radial velocity experiments is given in Table 1.<br />
It is certainly incomplete, and is intended only to give a flavour for the activity<br />
in the field. The vast majority <strong>of</strong> extra-solar planets discovered so far have been<br />
found by radial velocity searches, which have a natural bias for the discovery <strong>of</strong><br />
massive planets orbiting close to their central star (hot Jupiters). As the surveys<br />
continue for longer periods <strong>of</strong> time they become more and more sensitive to planets<br />
having longer periods, and to additional planets in systems in which one hot Jupiter<br />
is already known. Dedicated designs have brought spectrographs very close to the<br />
practical accuracy limit for ground-based radial velocity searches <strong>of</strong> ∼ 1 m s −1 ,<br />
allowing detection <strong>of</strong> lower mass planets. HARPS has recently detected a second<br />
planet around µ Arae, with a period <strong>of</strong> 9.5 days, a velocity semi-amplitude <strong>of</strong> less<br />
than 5 m s −1 (Santos et al., 2004), and a derived M sin i <strong>of</strong> only 14 M ⊕ (about one<br />
Uranus mass), making it the lowest mass planet found so far (as <strong>of</strong> December 2004).<br />
A planet <strong>of</strong> ∼ 17 M ⊕ has been discovered orbiting the M dwarf GJ 436 based on<br />
Keck data (Butler et al., 2004), and <strong>of</strong> ∼ 18 M ⊕ reported for 55 Cnc using HET<br />
observations (McArthur et al., 2004).<br />
Another trend is that larger telescopes are being used for the radial velocity searches.<br />
As a result the limiting magnitude <strong>of</strong> such searches has increased from typically<br />
V = 7.5 a few years ago to V ∼ 12, with the number <strong>of</strong> stars thus available for<br />
radial velocity study increasing by almost two orders <strong>of</strong> magnitude. For example,<br />
the N2K Consortium is using the Keck, Magellan and Subaru telescopes to track the<br />
next 2000 (N2K) closest (