GRAVITY reveals details of a storm-wracked exoplanet
The GRAVITY instrument on ESO’s Very Large Telescope Interferometer (VLTI) has made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterising many of the exoplanets known today.
The new observations of the exoplanet HR8799e were obtained using optical interferometry with the GRAVITY instrument developed at the Max Planck Institute for Extraterrestrial Physics. The exoplanet was discovered in 2010 orbiting the young main-sequence star HR8799, which lies around 129 light-years from Earth in the constellation of Pegasus. Today’s result, which reveals new characteristics of HR8799e, required an instrument with very high resolution and sensitivity. GRAVITY combines the VLT’s four unit telescopes using a technique known as interferometry. This creates a large super-telescope — the VLTI — that collects and precisely disentangles the photons from HR8799e’s atmosphere and the photons from its parent star.
HR8799e is a ‘super-Jupiter’, a world unlike any found in our Solar System, that is both more massive and much younger than any planet orbiting the Sun. At only 30 million years old, this baby exoplanet is young enough to give scientists a window onto the formation of planets and planetary systems. The exoplanet is thoroughly inhospitable — leftover energy from its formation and a powerful greenhouse effect heat HR8799e to a hostile temperature of roughly 1000 °C.
This is the first time that optical interferometry has been used to reveal details of an exoplanet, and the new technique furnished an exquisitely detailed spectrum of unprecedented quality — ten times more detailed than earlier observations. The team’s measurements were able to reveal the composition of HR8799e’s atmosphere — which contained some surprises.
“Our analysis showed that HR8799e has an atmosphere containing far more carbon monoxide than methane — something not expected from equilibrium chemistry,” explains team leader Sylvestre Lacour, researcher CNRS at the Observatoire de Paris - PSL and the Max Planck Institute for Extraterrestrial Physics (MPE). “We can best explain this surprising result with high vertical winds within the atmosphere preventing the carbon monoxide from reacting with hydrogen to form methane.”
The team found that the atmosphere also contains clouds of iron and silicate dust. When combined with the excess of carbon monoxide, this suggests that HR8799e’s atmosphere is engaged in an enormous and violent storm.
“Our observations suggest a ball of gas illuminated from the interior, with rays of warm light swirling through stormy patches of dark clouds,” elaborates Lacour. “Convection moves around the clouds of silicate and iron particles, which disaggregate and rain down into the interior. This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes.”
This result builds on GRAVITY’s string of impressive discoveries, which have included breakthroughs such as last year’s observation of gas swirling at 30% of the speed of light just outside the event horizon of the massive Black Hole in the Galactic Centre. “We knew that GRAVITY would open up a whole new range of possibilities,” marvels Frank Eisenhauer, who led the instrument development at MPE. “I am overwhelmed to see so many astonishing results from completely different fields of astronomy in such a short time!”
This research was presented in the paper “First direct detection of an exoplanet by optical interferometry” in Astronomy and Astrophysics
The team was composed of : S. Lacour (LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Meudon, France [LESIA]; Max Planck Institute for Extraterrestrial Physics, Garching, Germany [MPE]), M. Nowak (LESIA), J. Wang (Department of Astronomy, California Institute of Technology, Pasadena, USA), O. Pfuhl (MPE), F. Eisenhauer (MPE), R. Abuter (ESO, Garching, Germany), A. Amorim (Universidade de Lisboa, Lisbon, Portugal; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), N. Anugu (Faculdade de Engenharia, Universidade do Porto, Porto, Portugal; School of Physics, Astrophysics Group, University of Exeter, Exeter, United Kingdom), M. Benisty (Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France [IPAG]), J.P. Berger (IPAG), H. Beust (IPAG), N. Blind (Observatoire de Genève, Université de Genève, Versoix, Switzerland), M. Bonnefoy (IPAG), H. Bonnet (ESO, Garching, Germany), P. Bourget (ESO, Santiago, Chile), W. Brandner (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), A. Buron (MPE), C. Collin (LESIA), B. Charnay (LESIA), F. Chapron (LESIA) , Y. Clénet (LESIA), V. Coudé du Foresto (LESIA), P.T. de Zeeuw (MPE; Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), C. Deen (MPE), R. Dembet (LESIA), J. Dexter (MPE), G. Duvert (IPAG), A. Eckart (1st Institute of Physics, University of Cologne, Cologne, Germany; Max Planck Institute for Radio Astronomy, Bonn, Germany), N.M. Förster Schreiber (MPE), P. Fédou (LESIA), P. Garcia (Faculdade de Engenharia, Universidade do Porto, Porto, Portugal; ESO, Santiago, Chile; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), R. Garcia Lopez (Dublin Institute for Advanced Studies, Dublin, Ireland; MPIA), F. Gao (MPE), E. Gendron (LESIA), R. Genzel (MPE; Departments of Physics and Astronomy, University of California, Berkeley, USA), S. Gillessen (MPE), P. Gordo (Universidade de Lisboa, Lisbon, Portugal; CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Lisbon, Portugal), A. Greenbaum (Department of Astronomy, University of Michigan, Ann Arbor, USA), M. Habibi (MPE), X. Haubois (ESO, Santiago, Chile), F. Haußmann (MPE), Th. Henning (MPIA), S. Hippler (MPIA), M. Horrobin (1st Institute of Physics, University of Cologne, Cologne, Germany), Z. Hubert (LESIA), A. Jimenez Rosales (MPE), L. Jocou (IPAG), S. Kendrew (European Space Agency, Space Telescope Science Institute, Baltimore, USA; MPIA), P. Kervella (LESIA), J. Kolb (ESO, Santiago, Chile), A.-M. Lagrange (IPAG), V. Lapeyrère (LESIA), J.-B. Le Bouquin (IPAG), P. Léna (LESIA), M. Lippa (MPE), R. Lenzen (MPIA), A.-L. Maire (STAR Institute, Université de Liège, Liège, Belgium; MPIA), P. Mollière (Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), T. Ott (MPE), T. Paumard (LESIA), K. Perraut (IPAG), G. Perrin (LESIA), L. Pueyo (Space Telescope Science Institute, Baltimore, USA), S. Rabien (MPE), A. Ramírez (ESO, Santiago, Chile), C. Rau (MPE), G. Rodríguez-Coira (LESIA), G. Rousset (LESIA), J. Sanchez-Bermudez (Instituto de Astronomía, Universidad Nacional Autónoma de México, Mexico City, Mexic; MPIA), S. Scheithauer (MPIA), N. Schuhler (ESO, Santiago, Chile), O. Straub (LESIA; MPE), C. Straubmeier (1st Institute of Physics, University of Cologne, Cologne, Germany), E. Sturm (MPE), L.J. Tacconi (MPE), F. Vincent (LESIA), E.F. van Dishoeck (MPE; Sterrewacht Leiden, Leiden University, Leiden, The Netherlands), S. von Fellenberg (MPE), I. Wank (1st Institute of Physics, University of Cologne, Cologne, Germany), I. Waisberg (MPE) , F. Widmann (MPE), E. Wieprecht (MPE), M. Wiest (1st Institute of Physics, University of Cologne, Cologne, Germany), E. Wiezorrek (MPE), J. Woillez (ESO, Garching, Germany), S. Yazici (MPE; 1st Institute of Physics, University of Cologne, Cologne, Germany), D. Ziegler (LESIA), and G. Zins (ESO, Santiago, Chile).