First direct detection of an exoplanet by optical interferometry

Abstract

Aims. To date, infrared interferometry at best achieved contrast ratios of a few times 10−4 on bright targets. GRAVITY, with its dual-field mode, is now capable of high contrast observations, enabling the direct observation of exoplanets. We demonstrate the technique on HR 8799, a young planetary system composed of four known giant exoplanets. Methods. We used the GRAVITY fringe tracker to lock the fringes on the central star, and integrated off-axis on the HR 8799 e planet situated at 390 mas from the star. Data reduction included post-processing to remove the flux leaking from the central star and to extract the coherent flux of the planet. The inferred K band spectrum of the planet has a spectral resolution of 500. We also derive the astrometric position of the planet relative to the star with a precision on the order of 100 μas. Results. The GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital solutions. A small adjustment of a few degrees to the orbital inclination of HR 8799 e can resolve the tension, implying that the orbits are close to, but not strictly coplanar. The spectrum, with a signal-to-noise ratio of ≈5 per spectral channel, is compatible with a late-type L brown dwarf. Using Exo-REM synthetic spectra, we derive a temperature of 1150 ± 50 K and a surface gravity of 104.3 ± 0.3 cm s2. This corresponds to a radius of 1.17−0.11+0.13 RJup and a mass of 10−4+7 MJup, which is an independent confirmation of mass estimates from evolutionary models. Our results demonstrate the power of interferometry for the direct detection and spectroscopic study of exoplanets at close angular separations from their stars.

KELT-11 b: Abundances of Water and Constraints on Carbon-bearing Molecules from the Hubble Transmission Spectrum

“…While the detection of water is now routine for the hot-Jupiter class of planets, other molecules such as the carbon species remains challenging with current space instrumentation. With a few exceptions (Swain et al 2008(Swain et al , 2009, most claims for the carbon species from space have been based on additional absorption in the infrared Spitzer photometric bands (Madhusudhan et al 2010;Line et al 2016;Stevenson et al 2017;Gandhi et al 2019) or from ground-based observations using either direct imaging (Macintosh et al 2015; Barman et al 2015;Lacour et al 2019) or high-dispersion techniques (Snellen et al 2010;de Kok et al 2013;Konopacky et al 2013;Brogi et al 2017). While very valuable, these detections often lack a reference baseline or require the combination of multiple instruments, each with different systematics, which may limit the determination of absolute abundances or may lower the detection significance (Brogi & Line 2019;.…”

Ariel – a window to the origin of life on early earth?

“…Recent studies show that terrestrial planets that grow beyond 75 % of Earth's mass at the time when their disk dissipates will never get rid of their accumulated primordial atmosphere [274]. It is found from modelling present-day atmospheric noble gas isotope ratios of 36 Ar/ 38 Ar, 20 Ne/ 22 Ne and 36 Ar/ 22 Ne, that the proto-Earth most likely had 53 % -58 % of its present mass and could lose its tiny captured primordial H2/He-dominated atmosphere during a few Myr after disk evaporation [274]. This finding indicates that rocky planets need to accrete more than about 60% of the present Earth mass during their disks lifetime in order to later evolve into potential Earth-like habitats.…”

“…Additionally, thermal properties [16], surface properties [17], global atmospheric dynamics [18] and cloud properties [19] can all be garnered to a certain extent. Optical and near-infrared interferometry are now offering new possibilities in the search for exoplanets and the characterization of their atmospheres [20], with future prospects at UV wavelengths [21].…”

An exact, generalised Laplace resonance in the HR 8799 planetary system

“…In order to test the PO hypothesis, we used the most early HST observations in (Lafrenière et al 2009;Soummer et al 2011), a homogeneous, uniformly reduced data in (Konopacky et al 2016), as well as the most recent refined Gemini Planet Imager (GPI) observations in (De Rosa et al 2020), and the most accurate detection of HR 8799e in (Lacour et al 2019) with the GRAVITY instrument. This primary set does not contain all observations available in the literature, and we limited the data in order to reduce possible observational biases due to different instruments and pipelines, but to extend the observational window as much as possible.…”