Of these, only 51 were photographed directly from Earth, while all the others were discovered by indirect methods, such as transits and radial velocities.
It is not difficult to imagine why it is so complicated to photograph an exoplanet directly: the stars are in fact generally millions of times brighter. During a normal observation, the light reflected and/or produced by the exoplanets is therefore lost in the bright halo of the star.
However, it is possible to find some cases in which a planet can be photographed directly. This must be in orbit at a great distance around a not very bright star (such as a red dwarf) and must be comparable in size to Jupiter.
It is on the basis of these considerations that in 2004 it was possible to obtain the first direct image of an exoplanet!
The planet in question (in red in the image) is 2M1207b, which orbits a brown dwarf located 230 light-years away from Earth.
Going to see the characteristics of 2M1207b we see that it meets all the requirements we have talked about above.
It is in fact a gas giant with a diameter and a mass equal to 1.5 and 5 times those of Jupiter, respectively. It orbits at a distance of 55 AU from its star, about twice the distance that separates Neptune from the Sun.
Credit: ESO.
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