An extremely low-density and temperate giant exoplanet

Abstract

Transiting extrasolar planets are key objects in the study of the formation, migration, and evolution of planetary systems. In particular, the exploration of the atmospheres of giant planets, through transmission spectroscopy or direct imaging, has revealed a large diversity in their chemical composition and physical properties. Studying these giant planets allows one to test the global climate models that are used for the Earth and other solar system planets. However, these studies are mostly limited either to highly-irradiated transiting giant planets or directly-imaged giant planets at large separations. Here we report the physical characterisation of the planets in a bright multi-planetary system (HIP41378) in which the outer planet, HIP41378 f is a Saturn-sized planet (9.2 $\pm$ 0.1 R${}_{\oplus }$) with an anomalously low density of 0.09 $\pm$ 0.02 g cm${}^{-3}$ that is not yet understood. Its equilibrium temperature is about 300 K. Therefore, it represents a planet with a mild temperature, in between the hot Jupiters and the colder giant planets of the Solar System. It opens a new window for atmospheric characterisation of giant exoplanets with a moderate irradiation, with the next-generation space telescopes such as JWST and ARIEL as well as the extremely-large ground-based telescopes. HIP41378 f is thus an important laboratory to understand the effect of the irradiation on the physical properties and chemical composition of the atmosphere of planets.

Preprint submitted to Nature Astronomy. The results have not been peer-reviewed yet. Supplementary informations available as ancillary file

References in corpus (23)

• Habitable Zones Around Main-Sequence Stars: New Estimates
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion
• Models of Stars, Brown Dwarfs and Exoplanets
• The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Chromospheric CaII Emission in Nearby F, G, K, and M stars
• Transitions in the cloud composition of hot Jupiters
• A Framework for Characterizing the Atmospheres of Low-Mass Low-Density Transiting Planets
• The orbital eccentricity of small planet systems
• PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance
• Very Low-Density Planets around Kepler-51 Revealed with Transit Timing Variations and an Anomaly Similar to a Planet-Planet Eclipse Event
• Magnetic cycles of the planet-hosting star Tau Bootis: II. a second magnetic polarity reversal
• BGLS: A Bayesian formalism for the generalised Lomb-Scargle periodogram
• The Featureless Transmission Spectra of Two Super-Puff Planets
• An Earth-sized exoplanet with a Mercury-like composition
• Evidence for a systematic offset of $-$0.25 mas in the Gaia DR1 parallaxes
• The HARPS search for southern extra-solar planets. XXXI. Magnetic activity cycles in solar-type stars: statistics and impact on precise radial velocities
• Radial Velocity Data Analysis with Compressed Sensing Techniques
• Absolute masses and radii determination in multiplanetary systems without stellar models
• A Discrete Set of Possible Transit Ephemerides for Two Long Period Gas Giants Orbiting HIP 41378
• Revisiting the HIP41378 system with K2 and Spitzer
• Detecting transit signatures of exoplanetary rings using SOAP3.0

Cited by in corpus (14)

• Uncovering the true periods of the young sub-Neptunes orbiting TOI-2076
• Can planetary rings explain the extremely low density of HIP 41378f?
• The TESS-Keck Survey. VIII. Confirmation of a Transiting Giant Planet on an Eccentric 261 day Orbit with the Automated Planet Finder Telescope
• The First Near-Infrared Transmission Spectrum of HIP 41378 f, a Low-Mass Temperate Jovian World in a Multi-Planet System
• Cleaning our Hazy Lens: Exploring Trends in Transmission Spectra of Warm Exoplanets
• Kepler-167e as a Probe of the Formation Histories of Cold Giants with Inner Super-Earths
• A transit timing variation observed for the long-period extremely low density exoplanet HIP 41378f
• A Framework for Characterizing Transmission Spectra of Exoplanets with Circumplanetary Rings
• TOI-220 $b$: a warm sub-Neptune discovered by TESS
• Observational constraints on the formation and evolution of Neptune-class exoplanets
• Kepler's Last Planet Discoveries: Two New Planets and One Single-Transit Candidate from K2 Campaign 19
• The formation of transiting circumplanetary debris discs from the disruption of satellite systems during planet-planet scattering
• Cosmic Hydrogen and Ice Loss Lines
• ASTEP confirmation of a pair of long-period Jupiter-sized planets with extremely low densities transiting TOI-791