Journal
ASTRONOMY & ASTROPHYSICS
Volume 599, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201629682
Keywords
planets and satellites: individual: Proxima b; planets and satellites: atmospheres; techniques: spectroscopic techniques: high angular resolution
Categories
Funding
- Swiss National Science Foundation (SNSF)
- Fundacao para a Ciencia e a Tecnologia (FCT) through Investigador FCT [IF/01037/2013, IF/00169/2012]
- POPH/FSE (EC) by funding through the program Programa Operacional de Factores de Competitividade-COMPETE
- FCT through project [PTDC/FIS-AST/1526/2014]
- FEDER through COMPETE2020 [POCI-01-0145-FEDER-016886, UID/FIS/04434/2013, POCI-01-0145-FEDER-007672]
- Fundacao para a Ciencia e a Tecnologia (FCT) [IF/01037/2013CP1191/CT0001]
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Context. The temperate Earth-mass planet Proxima b is the closest exoplanet to Earth and represents what may be our best ever opportunity to search for life outside the Solar System. Aims. We aim at directly detecting Proxima b and characterizing its atmosphere by spatially resolving the planet and obtaining high-resolution reflected-light spectra. Methods. We propose to develop a coupling interface between the SPHERE high-contrast imager and the new ESPRESSO spectrograph, both installed at ESO VLT. The angular separation of 37 mas between Proxima b and its host star requires the use of visible wavelengths to spatially resolve the planet on a 8.2-m telescope. At an estimated planet-to-star contrast of similar to 10 7 in reflected light, Proxima b is extremely challenging to detect with SPHERE alone. However, the combination of a similar to 10(3)-10(4) contrast enhancement from SPHERE to the high spectral resolution of ESPRESSO can reveal the planetary spectral features and disentangle them from the stellar ones. Results. We find that significant but realistic upgrades to SPHERE and ESPRESSO would enable a 5 sigma detection of the planet and yield a measurement of its true mass and albedo in 20-40 nights of telescope time, assuming an Earth-like atmospheric composition. Moreover, it will be possible to probe the O-2 bands at 627, 686 and 760 nm, the water vapour band at 717 nm, and the methane band at 715 nm. In particular, a 3.6 sigma detection of O-2 could be made in about 60 nights of telescope time. Those would need to be spread over three years considering optimal observability conditions for the planet. Conclusions. The very existence of Proxima b and the SPHERE-ESPRESSO synergy represent a unique opportunity to detect biosignatures on an exoplanet in the near future. It is also a crucial pathfinder experiment for the development of extremely large telescopes and their instruments, in particular the E-ELT and its high-resolution visible and near-IR spectrograph.
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