Projects

Description

The SPHERE instrument, installed at the ESO Very Large Telescope at Paranal (Chile), aims at imaging and characterizing giant exoplanets around stars close to the Sun. SPHERE represents a huge technological and scientific challenge as planets are very faint and very close to their star and therefore difficult to detect. SPHERE is designed to optimally suppress the stellar light without removing the planetary signal using high-contrast and high-angular resolution techniques. To compensate for the effect of the atmosphere, SPHERE is equipped with an adaptive optics system to restore the ultimate spatial resolution of the telescope as if the Telescope was in Space. Then, combining various techniques of coronagraphy and differential imaging, SPHERE optimized the detection of the planets in imaging, but also the characterization of the planet’s orbital and chemical properties. SPHERE is currently on the UT3 Telescope of the ESO Paranal observatory. The instrument had its first light in May 2014 and has been offered to the community in early-2015. Combining technological and scientific challenges, SPHERE is one of the most innovant ground-based instruments built to date. The consortium to conduct the SPHERE project consists of 12 major European astronomy institutes.

In the context of the SPHERE consortium representing more than 150 European scientists, I am currently playing a central role to lead and manage the SPHERE Guaranteed Time Observations since 2014, and to nurture the SPHERE consortium Legacy.

The SPHERE consortium Legacy

In compensation for building the instrument, the consortium received a total of 260 nights of guaranteed time observations (GTO). They were allocated primarily to the SHINE survey for expolanets (200 nights), a programme to search for and image circumstellar disks (20 nights), a programme to search for planets in reflected light with ZIMPOL (20 nights), and a mixture of "other science" programs (12 nights). The remainder has been allocated as seen fit, mostly to the disk programme.

The prime scientific goals of SPHERE that were originally defined have actually been achieved

• to better understand the mechanisms of formation and evolution of planetary systems. The fundamental observational parameter is the frequency of planets as a function of mass and separation.

• to study the characteristics of young exoplanetary systems

• to study planet-disk interactions

• to characterize the properties of young planetary atmospheres

In addition to these exoplanetary topics, SPHERE provides outstanding contributions in the fields of brown dwarfs, stellar formation, discs and jets, small bodies of the solar system, and evolved stars.

A few highlights from the SPHERE GTO are detailed below including:

• Mysterious structures in the young, planetary architecture. The discovery several structures in the form of ondulations in the debris disk of the young, low-mass star AU Microscopii. These strcutures have been identified in older images from HST. The comparison of SPHERE and HST images showed that the structures moved by a significant distance. Some of these structures are very fast and probably escape from the attraction of the star. AU Microscopii is regularly observed with SPHERE in order to understand which mechanisms are producing such intriguing structures.

• The first exoplanet discovered with SPHERE. The exoplanet HIP 65426b — the first to be seen by the SPHERE instrument on ESO’s Very Large Telescope. The image of the parent star has been removed from the image for clarity, and its position marked with a cross; the circle indicates the orbit of Neptune around the Sun on the same scale. The planet is clearly visible at the lower-left in this remarkable image. HIP 65426 b is a super Jupiter exoplanet for which the infrared spectrum has indicated a carbon-poor and oxygen-rich atmosphere compared to Solar System gas giants.

• Planet caught in formation. PDS 70 b, discovered by the SPHERE consortium, was the first confirmed protoplanet to be directly imaged. PDS 70 (V1032 Centauri) is a low-mass T Tauri star in the constellation Centaurus. Located approximately 370 light-years from Earth, it has a mass lower than the Sun, and is approximately 10 million years old. The star has a protoplanetary disk containing two nascent exoplanets, named PDS 70b and PDS 70c, which have been directly imaged by the European Southern Observatory's Very Large Telescope.

• beta Pictoris revolution. With an orbital distance comparable to that of Saturn in the solar system, β Pictoris b is the closest (semi-major axis ≃9 au) exoplanet that has been imaged to orbit a star. Thus it offers unique opportunities for detailed studies of its orbital, physical, and atmospheric properties, and of disk-planet interactions. With the exception of the discovery observations in 2003 with NaCo at the Very Large Telescope (VLT), all following astrometric measurements relative to β Pictoris have been obtained in the south western part of the orbit, which severely limits the determination of the planet’s orbital parameters. Since the first SPHERE observation in December 2014 and up to December 2018, we have been able to directly follow the motion of this young, massive exoplanet as it moves to the other side of its host star up to the north western part.

• celebrating its 100th scientific publication. The SPHERE consortium played a major role in the success of SPHERE, and is celebrating in 2021 its 100th scientific publication, together with the release of a series of three articles in the Astronomy & Astrophysics Journal presenting the first phase of the exoplanet demographics survey beyond 10 Astronomical Units (AU) from the central star (that is Saturn’s orbit in our solar system). This achievement represents an important milestone for the SPHERE consortium to reward all individual members and institutes who successfully contributed to each critical step of the project, from the design phase, and the construction, up to the scientific exploitation over the last five years.

Collaborators

The SPHERE consortium is a large collaborations with several dozens of contributors.

SPHERE consortium management: Jean-Luc Beuzit (PI), David Mouillet (PS, construction phase), Gaël Chauvin (PS, exploitation phase), Markus Feldt (co-PI)

SPHERE consortium at IPAG: Philippe Delorme, Julien Milli, Mickael Bonnefoy, Simon Petrus, Célia Desgrange, Hervé Beust, Laetita Rodet, Julien Girard (associate)