Observatoire de Paris
<-   Properties of the discovered planets   ->

Indirect detection with the radial velocity method

To date (April 2005), we have detected about 150 planets with the radial velocity method. As seen before, this method only provides the orbit period (and thus the semi-major axis of the orbit), the orbit eccentricity, and the product (M_pl)*sin(i).

Indirect detection with the transit method

Some planets have been detected with the transit method. This method provides the orbit period, the inclination of the orbit (necessarily close to 90°), the radius of the planet and, combined with radial velocity measurements, the mass of the planet.
In addition, we can observe the spectrum of the star during the transit of the planet. The planet's atmosphere then produces absorption bands in the spectrum of the star, from which we can deduce the chemical composition of the atmosphere. That's how we have found hydrogen, oxygen and sodium in the atmosphere of HD209458 b.

Direct detection

The most important turning point since the first indirect discoveries is the detection of light arising directly from a planet. That's what has been detected for the very young planet (and thus still very warm) 2M1207-3932, as well as HD 209458b and TrES-1. The latter two periodically move past their star; a secondary eclipse then occurs when the star moves past the planet, one half-period later. This secondary eclipse has been detected, and from it we deduced the thermal flux of the planet.

Catalogue of the planets

About two planets a month are detected. Their properties are presented in this catalogue, which is regularly updated.