Detecting Earth twins, planets with physical properties similar to that of the Earth, and finding signatures of life in their atmospheres are prime objectives of astrophysics. HARPS / HARPS-N radial velocity (RV) and Kepler photometric campaigns have shown that this type of planets is very common. The detection and characterization of such planets or confirmation of their planetary nature is done with the RV technique, putting it in an important position in the field of exoplanets.
Unfortunately, RVs are affected by stellar signals that are of much larger amplitude than the signal created by Earth twins, and therefore prevent their detection. Stellar signals perturb also the high-resolution spectra needed to characterize an exoplanet atmosphere, and therefore correcting for those signals is crucial to the detection of biomarkers on other planets. With the most precise RV instruments available today we are able to characterize the RV effects induced by sunspots, granulation, and stellar oscillations. However, we face two issues when trying to devise mitigation techniques: acquiring a high temporal sampling and understanding the signal's origin.
To address these issues we built HELIOS, a solar telescope for HARPS, with the specific objective of acquiring high-resolution spectra and extremely precise RV measurement of the Sun as a star. The high-resolution spectra allows us to measure precisely the RV of the Sun as a star, as well as a number of other parameters and activity diagnostics. The measurements obtained by the telescope permit a characterization of Sun-as-a-star, with a similar observation setup as used on others stars, but with the following advantages:
• SAMPLING: Observing the Sun every day, therefore gathering data with a very high sampling.
• ORIGIN: Several instruments monitor and resolve the solar disc (SDO, HINODE, SOURCE). It is therefore possible to associate any disc-integrated RV variation observed by HELIOS with local phenomenon on the solar surface.
The measurements gathered by HELIOS are the best data set to determine the origin of RV stellar signals, to study their variation as a function of time, and to develop optimized correction techniques to strongly reduce their impact on RV measurements. HELIOS data is ingested into the ESO archive, from where it can be downloaded by any ESO portal user after expiration of the proprietary period. The HELIOS team is composed by:
|PI & Project Manager
||X. Dumusque (Observatory of
Geneva, University of Geneva)
|Co-PI and Instrument Scientist
||P. Figueira (ESO, Instituto de
Astrofısica e Ciencias do Espaco, University of
||G. LoCurto (ESO), D. F. Phillips
(Harvard-Smitshonian Centre for Astrophysics)
|Members of the Consortium
||. Udry, F. Pepe, C. Lovis
(Observatory of Geneva, University of Geneva),
N.C. Santos (Instituto de Astrofısica e Ciencias
do Espaco, University of Porto)