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\section{New worlds}  A revolution has occurred in the last two decades in the world of astrophysics.   It all started in the mid '90s with the first discovery of new worlds around other stars. The term "Extrasolar planet" (or Exoplanet) became widely used to identify planets\footnote{A planet is a celestial body massive enough to be bounded by its self gravity (unlike a rock or an asteroid, that are kept together by electromagnetic forces), but not massive enough to produce energy through nuclear fusion (as stars do)} orbiting a star other than the Sun.   %I remember hearing about the discovery of 51 Pegasi b, a giant planet about 50 light years away, on a bus ride to school. I was blown away. That night I could not sleep, my mind racing towards the amazing implications of that discovery. Little I knew that was just the beginning.