The CARMENES planet hunter detects comet-like tail of helium and water in atmospheres of giant exoplanets
Researchers of the CARMENES consortium detected atoms and molecules in the atmospheres of hot Jupiter exoplanets, which could help us understand how planet atmospheres evolve over time. The findings come from several dedicated observations obtained in the last two years with the CARMENES spectrograph — a planet hunting instrument installed at the 3.5-m telescope in Calar Alto.

Studies led by the researchers of the CARMENES consortium show that giant exoplanets WASP-69 b and HD189733 b have comet-like tails made of escaping helium particles, and confirm that water molecules are present in the atmosphere of exoplanet HD 189733 b. These new results prove that the CARMENES spectrograph can do more than just finding nearby planets, it can also analyse their atmospheres.  The results of this work are published today in the journal Science, and will also appear in the journal Astronomy & Astrophysics.

The three publications are led by researchers at the Instituto de Astrofísica de Canarias, University of Hamburg, and University of Leiden, and contain relevant contributions from several members of the Institut de Ciències de l’Espai (ICE, CSIC) and the Institut d’Estudis Espacials de Catalunya (IEEC).

CARMENES is a spectrograph installed on the 3.5-meter telescope of the Calar Alto Observatory,located in Almería, Spain. It simultaneously covers the visible wavelength range and the near infrared at high spectral resolution allowing for detailed searches of atoms and molecules in the atmospheres of planets passing in front of their parent stars. In addition to just detecting materials in their atmospheres, the new observations helped researchers draw conclusions about the speed of the helium being evaporated from the planet WASP-69 b, and the length of the tail it produces.

The two hot Jupiters, WASP-69 b and HD189733 b, were observed during transits, a phenomenon when the planet passes in front of its host star from our perspective here on Earth. During these events, the planet and its atmosphere block part of the starlight. "We observed a stronger and longer lasting dimming of the starlight in a region of the spectrum where helium gas absorbs light," says Lisa Nortmann, a researcher at the Instituto de Astrofisica de Canarias and lead author of the article on the WASP-69 b exoplanet. “The longer duration of this absorption allows us to infer the presence of a tail” she adds.
The team also investigated the host stars of these two exoplanets and three others analyzed in the article using data from the European Space Agency's Multi-Mirror X-Ray Mission (ESA XMM-Newton). The results indicate that helium is detected in the atmospheres of those planets that receive the largest amount of X-ray and extreme ultraviolet radiation from their host stars. “This is a first big step towards finding out how exoplanet atmospheres evolve over time says Enric Pallé, IAC researcher and co-author of the publication.

The results of these studies seem to indicate that extreme radiation from the star can strip the gaseous envelope off of giant planets (similar to Jupiter or Neptune) and turn them into bare rocky worlds with densities similar to those of Venus or the Earth. “In the past, studies of atmospheric escape, like the one we have seen in WASP-69 b, were based on space-borne observations in the far ultraviolet, a spectral region of very limited access and strongly affected by interstellar absorption,” says Michael Salz, a researcher at the University of Hamburg and first author of a companion publication by the same team, which focuses on the details of the detection in HD 189733 b to be published in the journal Astronomy & Astrophysics. “Our results” - he continues – “show that helium is a very promising new tracer to study atmospheric escape in exoplanets.”
This new line of research will permit astronomers to compare the evaporation processes in a large sample of planets and answer questions such as whether planets with ultra-short orbital periods are actually the evaporated nuclei of ancient hot Jupiters.

The water detection was achieved using a subset of observations also on the hot Jupiter HD 183799 b, but looking at broader parts of the spectrum. Water signals are very weak individually, but hundreds of small features across a broad part of the spectrum can be combined together to pull out faint signals like this. This technique has been used on very few instruments before, and the current result shows that CARMENES is up for the task as well. In the next few years this method could in principle reveal the presence of water in the atmosphere of warm and smaller planets around small red dwarf stars. This part of the work has been led by Javier Floriano-Alonso, currently working at University of Leiden, and has been accepted for publication in Astronomy & Astrophysics.

The publications have contributions from members of the Institut de Ciències de l’Espai (ICE, CSIC) and the Institut d’Estudis Espacials de Catalunya (IEEC) Ignasi Ribas, Juan Carlos Morales and Marina Lafarga. “The unexpected new use of the infrared capabilities of the CARMENES spectrograph makes us very hopeful about prospects of characterizing exciting worlds in the near future” adds Ignasi Ribas, co-author and project scientist of CARMENES.

CARMENES was developed by a consortium of eleven Spanish and German institutions. It was designed to search for terrestrial type planets in the habitable zone of M-stars, the region around a star where conditions allow the existence of liquid water. Observations with CARMENES played a central role in the recent announcement of the second closest exoplanet to Earth Barnard’s star b. The results published today demonstrate the ability of the instrument to also contribute significantly to the exoplanet atmosphere research field.

Contact information

Ignasi Ribas ICE/IEEC ( - English, Spanish, Catalan) CARMENES project scientist
Lisa Nortmann IAC ( - English , Deutsch) Lead author of Article 1
Michael Salz U. Hamburg ( - English, Deutsch)  Lead author of article 2
Javier Floriano Alonso, U.Leiden ( - English, Spanish)  Lead author of article 3

Media files: Links to artist impression images/video provided by IAC
Credit: Gabriel Perez Diaz (IAC)

Links & resources

Article 1 : Ground-based detection of an extended helium atmosphere in the Saturn?mass exoplanet WASP-69b
Nortmann, L.; Pallé, E.; Salz, M.; Sanz-Forcada, J.; Nagel, E.; Alonso-Floriano, F. J.; Czesla, S.; Yan, F.; Chen, G., Snellen I. A. G.;Zechmeister, M.; Schmitt, J. H. M. M.; López-Puertas, M.; Casasayas-Barris, N.; Bauer, F. F.; Amado, P.; Caballero, J.; Dreizler, S.; Henning, T.; Lampón, M.; Montes, D.; Molaverdikhani, K.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Sánchez-López, A.; Schneider, C.; Zapatero Osorio, M. R. (2018). This paper will be published online by the journal Science on THURSDAY, 6 December, 2018.

Article 2 : Detection of He I 10830 Å absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy
Salz, M.; Czesla, S.; Schneider, P. C.; Nagel, E.; Schmitt, J. H. M. M.; Nortmann, L.; Alonso-Floriano, F. J.; López-Puertas, M.; Lampón, M.; Bauer, F. F.; Snellen, I. A. G.; Pallé, E.; Caballero, J. A.; Yan, F.; Chen, G.; Sanz-Forcada, J.; Amado, P. J.; Quirrenbach, A.; Ribas, I.; Reiners, A.; Béjar, V. J. S.; Casasayas-Barris, N.; Cortés-Contreras, M.; Dreizler, S.; Guenther, E. W.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Ku?rster, M.; Lafarga, M.;Lara, L. M.; Molaverdikhani, K.; Montes, D.; Morales, J. C.; Sánchez-López, A.; Seifert, W.; Zapatero Osorio, M. R.; Zechmeister, M. (2018)

Article 3 : Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733b
Alonso-Floriano, F. J.; Sánchez-López, A.; Snellen, I. A. G.; López-Puertas, M.; Nagel, E.; Amado, P. J.; Bauer, F. F.; Caballero, J. A.; Czesla, S.; Nortmann, L.; Pallé, E.; Salz, M.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Aceituno, J.; Anglada-Escudé, G.; Béjar, V. J. S.; Guenther, E. W.; Henning, T.; Kaminski, A.; Kürster, M.; Lampón, M.; Lara, L. M.; Montes, D.; Morales, J. C.; Tal-Or, L.; Schmitt, J. H. M. M.; Zapatero Osorio, M. R.; Zechmeister, M. will be published in Astronomy and Astrophysics, and it is available in pre-print format in arXiv

CARMENES website :

Related press releases

Instituto de Astrofísica de Canarias (IAC) : Escape from planet WASP-69b: detection of an extended comet-like tail signaling the atmospheric loss of helium:

Instituto de Astrofísica de Andalucía: The "Planet Hunt" instrument CARMENES studies evaporating atmospheres and water vapour beyond the Solar System:

Hamburg University:

The CARMENES Consortium institutes

Max-Planck-Institut für Astronomie, MPIA ( )
Instituto de Astrofísica de Andalucía, IAA ( )
Landessternwarte Königstuhl, LSW ( )
Institut de Ciències de l'Espai, ICE ( )
Insitut für Astrophysik Göttingen, IAG ( )
Universidad Complutense de Madrid, UCM ( )
Thüringer Landessternwarte Tautenburg, TLS ( )
Instituto de Astrofísica de Canarias, IAC ( )
Hamburger Sternwarte, HS ( )
Centro de Astrobiología, CAB ( )
Centro Astronómico Hispano-Alemán, CAHA ( )

Special Notes to Reporters

More information, including a copy of the paper, can be found online at the Science press package at You will need your user ID and password to access this information. Please contact Lisa Nortmann ( for further information concerning media materials, and embargo.
Attached Documents
Generalitat de CatalunyaUniversitat de BarcelonaUniversitat Autònoma de BarcelonaUniversitat Politècnica de CatalunyaConsejo Superior de Investigaciones CientíficasCentres de Recerca de Catalunya