From Red Dots: “Proxima Centauri: What do we know? – by Mikko Tuomi”

Red Dots

4th July 2017
Mikko Tuomi


Following the announcement of the discovery of Proxima b, the Red Dots campaign aims at detecting additional small planetary sized companions to Proxima Centauri. But we already have hints of variability in the star’s radial velocities not explained by the presence of Proxima b alone. There is more to the star than Proxima b.

We explained in our paper last year [1] that there was evidence for variability at a period of roughly 215 days in the radial velocity data from two instruments: HARPS (including the Pale Red Dot observing run in 2016) at ESO observatory at La Silla, ESO’s UVES instrument at VLT in Paranal, Chile. This variability is much more dominant on these relatively longer periods than the signal caused by Proxima b and is especially clearly visible when looking at the unbinned data (Fig. 1) — it is certainly amplified with respect to that in the nightly binned data presented in the Proxima b discovery paper. But although we labelled this variability as activity and removed it in order to study the signal of Proxima b at a shorter period, in reality, we do not know its origin. Different hypotheses range from instrumental instability to activity of the stellar surface to Doppler signature of another planet orbiting the star.

See the full article here .

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Red dots is a project to attempt detection of the nearest terrestrial planets to the Sun. Terrestrial planets in temperate orbits around nearby red dwarf stars can be more easily detected using Doppler spectroscopy, hence the name of the project.

ESO 3.6m telescope & HARPS at LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO/HARPS at La Silla