Innovative Gemini/CHFT Partnership Explores a Hot Jupiter

Artistʻs view of a newborn giant planet like the one newly discovered at the immediate vicinity of the very active infant star V830 Tau, as might be seen by an observer located close to the giant planet.  Download image | (Credit: Mark A. Garlick markgarlick.com)

Brightness and magnetic spots at the surfaces of V830 Tau induce spectral perturbations much larger than those caused by the reflex motion of the detected giant planet. Activity perturbations are shown in the top panel, with the blue arrow depicting the spectral velocity shift (scaled up by 20x) that activity generates. The bottom panel illustrates the combined effects of activity and of the detected planet on the spectrum of V830 Tau, with the blue / green / red arrows respectively showing the velocity shifts induced by activity, by the giant planet, and by both (scaled up by 20x). Click on the links for animations of the profile distortions induced by the spotted star, and by the spotted star plus the planet. (Credit: Jean-François Donati)

For the last 20 years the giant planets known as hot Jupiters have presented astronomers with a puzzle. How did they settle into orbits 100 times closer to their host stars than our own Jupiter is to the Sun? An international team of astronomers has announced this week¹ the discovery of a newborn hot Jupiter, orbiting an infant sun — only 2 million years old, the stellar equivalent of a week-old human baby. The discovery that hot Jupiters can already be present at such an early stage of star-planet formation represents a major step forward in our understanding of how planetary systems form and evolve. 

For this discovery, the team monitored a 2 million-year-old infant star called V830 Tau, located in the Taurus stellar nursery, some 430 light-years away. Over the 1.5 months of the campaign, a regular 4.9-day “wobble” in the velocity of the host star revealed a giant planet almost as massive as Jupiter, orbiting its host star at a distance of only one-twentieth that of the Sun to the Earth distance. “Our discovery demonstrates for the first time that such bodies can be generated at very early stages of planetary formation, and likely play a central role in shaping the overall architecture of planetary systems” explains Jean-François Donati, CNRS astronomer at IRAP / OMP² and lead author of a new paper in the current issue of the journal Nature.

The team used the twin spectropolarimeters ESPaDOnS and Narval to monitor V830 Tau for a total of 47 hours.  ESPaDOnS is mounted at the 3.6-m Canada-France-Hawaii Telescope³ (CFHT) on Maunakea and can be fiber-fed from either CFHT itself, or via GRACES, a 300-m optical-fiber link from the nearby 8 meter Gemini North telescope.  The team used ESPaDOnS in both modes, providing the opportunity to monitor the star using light from the Gemini North telescope when the instrument was unavailable at CFHT.

The team also used Narval, mounted at the 2-meter Télescope Bernard Lyot⁴ (TBL) atop Pic du Midi in the French Pyrénées.  “Using all three telescopes was essential for monitoring regularly V830 Tau throughout our campaign and for detecting its giant planet” stresses Lison Malo, CFHT astronomer, a coauthor of the study and leader in coordinating the observations.

In our Solar System, small rocky planets like the Earth are found near the Sun, whereas gas giants like Jupiter and Saturn orbit much further out.  “The discovery in 1995 of a giant planet flying very close to its host star took us by surprise and revolutionized the field” recalls Claire Moutou, CNRS astronomer at CFHT and a coauthor of this new study. Theoretical work indicates that such planets can only form in the cold and icy outer regions of the protoplanetary disc in which both the central star and surrounding planets are born. Some, however, migrate inwards without falling into their host star, thus becoming hot Jupiters.

“Planet formation models offer two competing explanations of how and when this migration of hot Jupiters occurred. Either it happened early while these planets were still forming, or much later, with some planets being kicked closer to their stars due to the interaction of multiple planets, or both” explains Clément Baruteau, CNRS astronomer at IRAP / OMP and a coauthor of this study. “Our discovery demonstrates that the first, earlier option is taking place; it revives the long-running debate about how and when this migration occurs, and brings us one step forward in our understanding of how planetary systems form”.

Among the known hot Jupiters, some feature strongly-tilted or even upside-down orbits, suggesting they were knocked into close orbits by interactions with other planets or neighboring stars. Others orbit above the host star’s equator, hinting at a more gentle formation process in the form of an inward drift through the disc.

“The young hot Jupiter we just detected comes as the first evidence that early disc migration is also happening” says Andrew Collier Cameron of the University of St Andrews, a coauthor of the study.


Contacts:

Claire Moutou
CFHT, Hawaii
Phone: +1-8088857944
moutou@cfht.hawaii.edu

Jean-François Donati
IRAP / OMP, Fr
Phone: +33-561332917
jean-francois.donati@irap.omp.eu

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View CFHT release.

The novel collaboration between the Gemini Observatory and Canada-France-Hawai‘i Telescope (CFHT) called GRACES (Gemini Remote Access to CFHT ESPaDOnS Spectrograph), helped to characterize a “hot Jupiter” around the T-Tauri star V830 Tau. The work appears in the current advanced online issue of the journal Nature. 

GRACES uses an innovative 270-meter fiber cable to transport light from the Gemini 8-meter telescope to the ESPaDOnS Spectrograph at CFHT. The system began operating in late 2015 and now is a popular option allowing Gemini and CFHT users to perform high-resolution optical spectroscopy with Gemini North’s larger mirror.

The Nature paper is available online (subscription required) and is summarized in the press release from Observatoire Midi Pyrenees in Toulouse, France and CFHT that follows (release is reproduced verbatim from original): Newborn Giant Planet Grazes its Sun

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“SPIRou and SPIP, the twin new-generation instruments built for CFHT and TBL by our team and scheduled for first light in 2017 and 2019 respectively, will offer vastly superior performances for such programs, and will soon allow us to explore the formation of new worlds with unprecedented sensitivity”, adds Louise Yu, a coauthor of the study and PhD student in observational exoplanet science at IRAP / OMP.

1 The paper describing the discovery, published in Nature, is available here

2 IRAP (Institut de Recherche en Astrophysique et Planétologie) is a research lab part of OMP (Observatoire Midi-Pyrénées) located in Toulouse (France), and under dual supervision from CNRS / INSU (Centre National de la Recherche Scientifique / Institut National des Sciences de l’Univers) and UFTMiP / UPS (Université Fédérale Toulouse Midi-Pyrénées / Université Paul Sabatier)

3 CFHT is operated by the National Research Council of Canada, CNRS/INSU in France and the University of Hawaii

4 TBL is operated by IRAP / OMP, CNRS / INSU and UFTMiP / UPS

Hot Jupiters courting baby stars?

Formation of stars and their planets in the Taurus nursery as seen at millimeter wavelengths by the APEX telescope in Chile 

Credits ESO/APEX

Star surface and planet (top) and magnetic field lines (bottom) at the surface of V830 Tau as reconstructed from ESPaDOnS observations.

ESPaDOnS observations of V830 Tau - a baby star in the Taurus nursery. Once the polluting effect of spots is removed, the residual shift of the spectrum (red dots and error bars) varies with time with a 6-day period. This spectral motion is compatible with that expected from a 1.4 Jupiter-mass planet orbiting at only 1/15 of the Sun-Earth distance (light blue curve). More densely-sampled observations are necessary to validate this preliminary result.

CFHT with a CAD view of SPIRou - the forthcoming spectropolarimeter in construction at OMP/IRAP

(not to scale - credit JC Cuillandre for the CFHT image)

Although first detected 20 years ago, hot Jupiters are still enigmatic bodies. These celestial objects are giant Jupiter-like exoplanets that orbit 20 times closer to their host stars than the Earth does to the Sun. Using the ESPaDOnS spectro-polarimeter on the Canada-France-Hawaii Telescope, the Matysse⁽¹⁾ team led by Dr J.-F. Donati (Toulouse, CNRS) reports the preliminary evidence that a hot Jupiter orbits a 2-My star of the Taurus star forming region. This planet, yet to be confirmed, has a mass of 1.4 Jupiter mass and a 6-day period orbit and is unveiled by the gravitational pull it imprints on its star⁽²⁾, once the stellar activity features are modeled. This discovery⁽³⁾ could help us better understand how planetary systems like (or unlike) the solar system form and evolve into maturity. This could also be the first exoplanet ever revealed by CFHT, a nice introduction to the coming SPIRou⁽⁴⁾ planet search survey.

In our solar system, rocky planets like the Earth or Mars are found near the Sun whereas giant planets like Jupiter and Saturn orbit much further out. "Hence the surprise in 1995 when Mayor & Queloz first unveiled a giant planet sitting very close to its host star" says Dr C. Moutou, CNRS astronomer at CFHT and co-author of this new study. Since then, astronomers demonstrated that such planets must form in the outer regions of the protoplanetary disc, then migrate inwards and yet avoid falling into their host star. This could happen either very early in their lives, when still embedded within their primordial disc. Or much later, once multiple planets are formed and mutually interact in a rather unstable choreography - with some being pushed inwards at the immediate vicinity of their stars.

An international team of astronomers led by Dr J.-F. Donati just secured preliminary evidence supporting the first of these two scenarios. Using ESPaDOnS, a spectropolarimeter built by IRAP / OMP for the CFHT, they looked at newly-born stars in the Taurus stellar nursery about 450 light-years away from us. They showed that the latest baby star they scrutinized, nicknamed V830 Tau, exhibits signatures that closely resemble those caused by a 1.4 Jupiter-mass planet orbiting 15 times closer to its host star than the Earth does to the Sun. This discovery, published in MNRAS, provides preliminary evidence that hot Jupiters may be extremely young and far more frequent around very young stars than around mature Sun-like stars.

Although potentially very informative about planet formation, young stars are extremely challenging to observe. "Being enormously active and strongly magnetic, baby stars are covered with huge spots hundreds of times wider than those of our Sun, which generate perturbations in their spectra much larger than those caused by orbiting planets. As a result, their planets are quite tricky to detect, even in the case of hot Jupiters", outlines E. Hebrard, PhD student at IRAP / OMP and co-author of the study. To address this issue, the team initiated the MaTYSSE survey aimed at mapping the surfaces of baby stars and at looking for the potential presence of hot Jupiters. "By monitoring these stars and using tomographic techniques inspired from medical imaging, we can unveil how dark and bright features are distributed across their surfaces, and how their magnetic fields expand into space. This modeling allows us to compensate for the perturbations that spots and fields generate in the spectra of young stars, and thus to regain the power of diagnosing the presence of close-in giant planets", explains Dr G. Hussain (ESO, UFTMiP), co-author of the study. In the case of V830 Tau, the authors accurately modeled the surface field and spots in order to clean out their polluting effects, enabling them to discover the much weaker signal that hints at the presence of a giant planet. 

Although more data are required for a definite validation, this promising first result clearly demonstrates that the technique the team devised is powerful enough to solve the puzzling question of how hot Jupiters form. " SPIRou, the new instrument currently built for CFHT by our team and scheduled for first light in 2017, will offer vastly superior performances thanks to its operation at near infrared wavelengths, at which young stars are far brighter, and will allow us to address this long-standing problem with unprecedented accuracy", Dr J.-F. Donati concludes. 

Additional information 

- 1. Matysse (Magnetic Topologies of Young Stars and the Survival of close-in giant Exoplanets) is a CFHT Large Program started in 2013 with ESPaDOnS. Matysse is a collaboration led by J.F. Donati (IRAP, Obs Midi-Pyrenees, France) with astronomers from IPAG (Grenoble, F), ENS (Lyon, F), CEA (Saclay, F), LAM (Marseille, F), OCA (Nice, F), UdM (Montreal, C), UFMG (Belo Horizonte, B), ASIAA (Taipei, T), NAO (Beijing, C) and many associated scientists outside the CFHT community.

- 2. The radial-velocity method uses the gravitational pull on the star by the planet modulated by its orbital motion, and measures the resulting spectral shift of the star with respect to the observer using the Doppler effect. This effect is of the order of 100 m/s for a hot Jupiter as the putative V 830 b and is repeatable at the period of the orbit - here, about 6 days.

- 3. The full paper is accepted in the Monthly Notices of the Royal Astronomical Society (MNRAS, Oxford University Press); it is entitled: "Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819 Tau and V830 Tau", by J.-F. Donati, E. Hebrard, G. Hussain, C. Moutou, L. Malo, K. Grankin, A. Vidotto, S. Alencar, S.G. Gregory, MM. Jardine, G. Herczeg, J. Morin, R. Fares, F. Menard, J. Bouvier, X. Delfosse, R. Doyon, M. Takami, P. Figueira, P. Petit, I. Boisse and the MaTYSSE collaboration, and is accessible here.

- 4. SPIRou i is a near-infrared spectropolarimeter and a high-precision velocimeter optimized for both the detection of habitable Earth twins orbiting around nearby red dwarf stars, and the study of forming Sun-like stars and their planets. SPIRou is managed in the framework of an international consortium led by France and involving, in addition to the Canada-France-Hawaii Telescope (CFHT), Canada, Switzerland, Brazil, Taiwan and Portugal. The construction of SPIRou has started in 2015, with integration in Toulouse, France, scheduled for 2016 and first light at CFHT for 2017. 

- This press release is also available as a pdf file with complementary illustrations.


Contacts

Dr. Claire Moutou (CFHT, Hawaii)
moutou@cfht.hawaii.edu
1-808-885-7944
  
Dr. Lison Malo (CFHT, Hawaii)
malo@cfht.hawaii.edu
1-808-885-7944    

Dr. Jean-Francois Donati (IRAP, Toulouse, France)
jean-francois.donati@irap.omp.eu
33-561-332-917  

Source:  Canada-France-Hawaii Telescope (CFHT)