Tag Archives: Coralie

Amaury Triaud wins the RAS Fowler Award

Congratulations to Dr Amaury Triaud, now at the University of Birmingham, recipient of the 2020 Fowler Award from the Royal Astronomical Society. The Fowler Award is for scientists making a “particularly noteworthy contribution to Astronomy & Geophysics at an early stage of their research career”.

Amaury Triaud

The citation reads: “Between 2007 and 2017, Dr Triaud led the radial-velocity follow-up of planet candidates south of declination −10 degrees from the Wide-Angle Search for Planets (WASP). His programme led to the discovery of over 130 planets from some 1000 candidates, making WASP the most successful of all ground-based transit searches.”

Amaury started looking for WASP exoplanets as a graduate student at the Geneva Observatory, under the direction of Didier Queloz (himself recipient of the 2019 Nobel Prize for Physics for his discoveries of exoplanets). Didier’s group at Geneva operated the CORALIE spectrograph on the 1.2-m Euler telescope at La Silla in Chile. Euler/CORALIE was the ideal follow-up instrument to vet the transiting exoplanet candidates coming from WASP-South, able to show which ones were genuinely the transits of planetary-mass bodies (only 1-in-10 of all candidates), and which were merely transit mimics. Amaury organised and ran the campaign, observing of order 1500 candidates and leading to the discovery of around 150 planets.

Euler telescope

The Euler 1.2-m telescope

While the citation mentions the campaign for Southern candidates south of declination −10 degrees, the Geneva group were also responsible for much of the follow-up in the equatorial strip from −10 to +10 degrees, where the candidates came jointly from data from WASP-South and from SuperWASP-North on La Palma.

Amaury’s work extended into studying the orbits of the WASP exoplanets, showing that many of the orbits were misaligned. He also developed programs identifying and studying the low-mass binary stars that also came from the WASP survey, and is now looking for circumbinary planets orbiting these low-mass binaries.

Nobel Prize for Michel Mayor and Didier Queloz


Naturally, we at WASP are chuffed at the award of the Nobel Prize in Physics to Michel Mayor and Didier Queloz for their discovery of 51 Peg b, the first extra-solar planet found orbiting a sun-like star. Congratulations to them both! The award is a welcome boost and recognition of the burgeoning field of exoplanets.

The WASP-South camera array

When, back in 2006, we built WASP-South in South Africa and started our Southern survey for transiting exoplanets, the Geneva Observatory team led by Mayor and Queloz were the obvious collaborators, given their world-leading track-record in the radial-velocity discovery of exoplanets, and their Euler telescope with its CORALIE spectrograph, situated at La Silla in Chile.

Prof Queloz, and his then-students Michaël Gillon and Amaury Triaud, started the radial-velocity observations of WASP-South transit candidates. Since many transit candidates turn out to be transit mimics, both the transit data and RV data are necessary to prove the discovery of a planet. That collaboration still continues, and has involved the Geneva Observatory team observing 1500 WASP candidates over many hundreds of clear nights with Euler/CORALIE.

Euler telescope

The Euler 1.2-m telescope

The result has been the discovery of over 150 exoplanets transiting bright stars, and many of them are among the most valuable exoplanets for further observation and study. So far the collaboration between Prof Queloz’s team and WASP-South has led to over 100 refereed papers in leading journals, that have so far been cited over 5000 times.

RAS Gold Medal for Professor Michel Mayor

The Royal Astronomical Society has announced the award of a Gold Medal to Professor Michel Mayor of the University of Geneva. Prof. Mayor was, of course, the co-discoverer of the first extrasolar planet around a solar-like star, with the detection of 51 Pegasi b back in 1995. His Observatoire de Genève group developed a succession of planet-finding spectrographs that have led the way to the discovery of many hundreds of extrasolar planets.

Michel Mayor

Prof. Mayor has been an important collaborator for the WASP project, through the CORALIE spectrograph on the 1.2-m Swiss/Euler telescope at La Silla. The CORALIE spectrograph observes all WASP-South planet candidates, and the detection of the radial-velocity signature of a planet — in about 1 in 8 such candidates — is the crucial step that confirms a new planet discovery. Thus Prof. Mayor was a co-author on many of the early WASP planet papers until his retirement.

The WASP project is hugely indebted to Prof. Mayor and is honoured to have collaborated with him on WASP planet discovery. We congratulate him on the well-deserved award of the RAS Gold Medal.

WASP-94: “cousin” planets around twin stars

Press release regarding our discovery of planets around binary stars WASP-94A and WASP-94B:

European astronomers have found two new Jupiter-sized extra-solar planets, each orbiting one star of a binary-star system. Most known extra-solar planets orbit stars that are alone, like our Sun. Yet many stars are part of binary systems, twin stars formed from the same gas cloud. Now, for the first time, two stars of a binary system are both found to host a “hot Jupiter” exoplanet.

The discoveries, around the stars WASP-94A and WASP-94B, were made by a team of British, Swiss and Belgian astronomers. The British WASP-South survey, operated by Keele University, found tiny dips in the light of WASP-94A, suggesting that a Jupiter-like planet was transiting the star; Swiss astronomers then showed the existence of planets around both WASP-94A and then its twin WASP-94B.

Marion Neveu-VanMalle (Geneva Observatory), who wrote the announcement paper, explains: “We observed the other star by accident, and then found a planet around that one also!”.

Hot Jupiter planets are much closer to their stars than our own Jupiter, with a “year” lasting only a few days. They are rare, so it would be unlikely to find two Hot Jupiters in the same star system by chance. Perhaps WASP-94 has just the right conditions for producing Hot Jupiters? If so WASP-94 could be an important system for understanding why Hot Jupiters are so close to the star they orbit.

The existence of huge, Jupiter-size planets so near to their stars is a long-standing puzzle, since they cannot form near to the star where it is far too hot. They must form much further out, where it is cool enough for ices to freeze out of the proto-planetary disk circling the young star, hence forming the core of a new planet. Something must then move the planet into a close orbit, and one likely mechanism is an interaction with another planet or star. Finding Hot-Jupiter planets in two stars of a binary pair might allow us to study the processes that move the planets inward.

Professor Coel Hellier, of Keele University, remarks: “WASP-94 could turn into one of the most important discoveries from WASP-South. The two stars are relatively bright, making it easy to study their planets, so WASP-94 could be used to discover the compositions of the atmospheres of exoplanets”.

The WASP survey is the world’s most successful search for hot-Jupiter planets that pass in front of (transit) their star. The WASP-South survey instrument scans the sky every clear night, searching hundreds of thousands of stars for transits. The Belgian team selects the best WASP candidates by obtaining high-quality data of transit lightcurves. Geneva Observatory astronomers then show that the transiting body is a planet by measuring its mass, which they do by detecting the planet’s gravitational tug on the host star.

The collaboration has now found over 100 hot-Jupiter planets, many of them around relatively bright stars that are easy to study, leading to strong interest in WASP planets from astronomers worldwide.

An illustration of a planet orbiting one star of a binary system. In WASP-94, the planet would transit the brighter star, causing a dip in the light that can be detected from Earth. Another planet orbits the second star at lower-left. It does not transit and is not directly visible, but it can be detected by its gravitational tug on the second star.

An illustration of a planet orbiting one star of a binary system. In WASP-94, the planet would transit the brighter star, causing a dip in the light that can be detected from Earth. Another planet orbits the second star at lower-left. It does not transit and is not directly visible, but it can be detected by its gravitational tug on the second star. [ Image Credit: ESO/L. Calçada/Nick Risinger]

Update: This press release has resulted in articles in phys.org, sciencedaily.com, world-science.net, yahoo.news, Science World Report, and breakingnews.ie.

WASP thesis wins European Astronomical Society prize

Congratulations to Dr Amaury Triaud for winning the highly prestigious 2014 MERAC Prize, awarded by the European Astronomy Society for the Best Doctoral Thesis in Observational Astrophysics. Dr Triaud was a PhD student at the Geneva Observatory of the University of Geneva, supervised by Prof. Didier Queloz.

Amaury Triaud

Amaury Triaud took charge of the radial-velocity campaign following up WASP-South planet candidates, using the Coralie spectrograph on the Swiss/Euler 1.2-m telescope at La Silla, and has thus played a major part on the discovery of all WASP-South transiting exoplanets. The MERAC prize highights the success of the European collaboration between the British WASP-South transit search, the Swiss Euler/Coralie spectrograph, and the Belgian-led TRAPPIST robotic photometer.

Euler telescope

The Euler 1.2-m telescope

In addition to the planet discoveries, Amaury Triaud lead-authored a landmark paper on the dynamical origins of hot-Jupiter exoplanets, deduced by measuring the angle between the planet’s orbit and the host-star’s spin, which has already been cited 170 times. Amaury’s work provided strong evidence that hot Jupiters formed much further out than their current orbits, and were moved inwards by the Kozai mechanism.