Rosa M. Ros

Technical University of Catalonia, Barcelona (Spain)


When in 1610 Galileo Galilei looked at Jupiter with the use of his telescope, he saw four “bodies” circling it (Figure 1). This discovery was in contradiction to the then generally held belief that all heavenly bodies turned round the Earth. This fact represented a scientific revolution at that time and helped in the acceptance of the Heliocentric Copernican System. As Jupiter and their Galilean satellites is a good model of a planetary system our intention is to study this using a set of photographs which we had taken previously.

When in 1995 Michael Mayor and Didier Queloz announced the detection of an exoplanet orbiting the ordinary main sequence star 51 Pegasi a new era began. Currently several methods are being used to find exoplanets more or less indirectly:

- Astrometry

- Radial velocity or Doppler method

- Pulsar timing

- Transit method

- Gravitational microlensing

- Circumstellar disks

- Eclipsing binary

- Orbital phase

- Polarimetry

Each of these methods is more or less appropriated for different kinds of planets. For instance, it is possible to detect them by measuring the planet’s influence on the motion of its parent star, but in this case the exoplanet found has to be very big. The smallest planets can be found eventually by observing the apparent luminosity variation in a star’s as a planet passes in front of it, but this means that the observer must be approximately in the same plane as that of the planet’s orbit. By using different methods it has been possible to list about 30 multiple-planet systems. We will compare them, in some way, with the solar system and the Galilean satellites of Jupiter.

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