Free Astronomy Magazine March-April 2022

25 MARCH-APRIL 2022 ASTRO PUBLISHING A n exoplanet can be de- tected through an os- cillation in the movement of its star, caused by the gravitational attraction of the planet itself on the star as they orbit around their common center of mass. When viewed from afar, the star seems to approach and move away from the observer. The movement makes the light of the star appear slightly bluer when it moves towards the ob- server and slightly redder when it moves away. This change in frequency is known as the Doppler Ef- fect. Most of the early dis- coveries of exoplanets took place by exploiting this effect. [ESA] both photometrically and spectroscopically, allowing it to easily hide the signal produced by any Proxima b transits. Nevertheless, if the planet transits, it does so every 11.2 days, a fre- quency that in the long run could bring out the signal. If it were possible to regularly record the transits, there would be the op- portunity to carry out more in- depth spectroscopic analy- ses and reveal the possi- ble presence of biosigna- tures − molecules poten- tially linked to the presence of life, such as oxygen and methane. This opportunity, referring precisely to the planet in the habitable zone closest to the Solar System, has lately prompted many teams of researchers to study Proxima Centauri assiduously to confirm or definitively exclude the transits of Proxima b. The first team was the Anglada- T his graph shows the movement of Proxima Centauri with respect to the Earth in the first months of 2016. In one part of its orbit, the star approaches the Earth at about 5 km/h, then in another part it moves away at the same velocity. This regular pattern of radial ve- locity variation repeats itself over a period of 11.2 days. [ESO/G. Anglada-Escudé] Escudé team, which analyzed a num- ber of the star’s light curves avail- able in 2016 but found no evidence of transits. Those same researchers, considering the orbital separation of the planet, calculated that the