Free Astronomy Magazine July-August 2020

13 JULY-AUGUST 2020 EXOPLANETS Just a week after these latest remarkable revelations, news began to circulate about a new search in the archive data conducted by Fritz Benedict (retired astronomer of the McDonald Observatory) that would have confirmed the existence of the outer planet, Proxima c. The results of this latest work on the topic in question were presented in early June at the 236th meeting of the American Astronomical Society and are based on the reanalysis of astrometric meas- urements ob- tained in the last quarter of a cen- tury by the Fine Guidance Sensors of the Hubble Space Telescope. Although the pri- mary task of these sensors is to ensure accurate pointing of the telescope, it is also possible to use them to make precise measure- ments of the posi- tions and motions of stars. In the 1990s, Benedict had already attempted to high- light anomalies in Proxima Centauri’s mo- tion in the sky by searching for periods of less than 1000 days, but had been unable to find anything. After learning about the work of Damasso’s team, Benedict reviewed all of the available data, looking for a swing in the stellar mo- tion with a longer period. This time, it seems that he has found a variation (acceleration and deceleration with respect to the straight motion) with a period of 1907 days, practically identical to that found by Da- masso and colleagues. But Benedict went further, combining his results with those of previous measurements and producing a calculated mass of seven Earth masses for Proxima c. Until Benedict’s results are validated by other researchers, the presence of extra planets in addition to Proxima b remains un- confirmed. Discovering others would not be a surprise, however, because small-mass stars tend to host several rocky planets, not infre- quently in very narrow orbits. We, there- fore, expect further and compelling dis- coveries in the Proxima Centauri system. ! A part of the ESPRESSO facility which, through a fiber optic system, col- lects the light beams from the four VLT's 8.2- meter telescopes and sends them to the spectro- graph located in another room. [ESO/P. Horálek] Below, Fritz Benedict, the as- tronomer whose independent work might have con- firmed the exis- tence of Proxima c using archive data from the Hubble Space Telescope. [University of Texas, McDonald Observatory]