Publication archive

Publication archive

Download this interactive media kit to learn more about the launch of CHEOPS on 17 December 2019 and the science goals of the mission. CHEOPS, the CHaracterising ExOPlanet Satellite, is ESA's first mission dedicated to the study of exoplanets. It will observe bright stars that are already known to host planets, measuring minuscule brightness changes due to the planet's transit across the star's disc.

Contents:

  • Introduction
  • Event programme
  • Key messages
  • CHEOPS science themes
  • CHEOPS: an exoplanet follow-up mission
  • Exoplanet detection methods
  • Exoplanets discoveries
  • Examples of planetary systems
  • Characterising exoplanets with CHEOPS
  • CHEOPS observing programmes
  • What are exoplanets made of?
  • Open questions: How do planets form?
  • Open questions: How do planets evolve?
  • High photometric stability and precision
  • Where is CHEOPS?
  • Launch details and timeline
  • CHEOPS team and consortium
  • Selected images
  • Selected videos
  • Media services

To download the pdf file (25 MB) click on the image or on the link to publication below.

Published: 10 December 2019
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Solar Orbiter is a mission dedicated to solar and heliospheric physics. It will address big questions in Solar System science to help us understand how the Sun creates and controls the heliosphere, the giant bubble of plasma that surrounds the whole Solar System and influences Earth and the other planets within it. The spacecraft will provide close-up, high-latitude observations of the Sun to gain new information about the solar wind, the heliospheric magnetic field, solar energetic particles, transient interplanetary disturbances and the Sun's magnetic field.

Contents:

  • Living with a star
  • Exploring our Sun
  • Anatomy of our Sun
  • Preparing for extreme environments
  • How Solar Orbiter will study the Sun
  • Launching and operating Solar Orbiter
  • Teamwork with Parker Solar Probe
  • An international enterprise
Published: 01 October 2019
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Document reference: ESA-SCI-F-ESTEC-RP-2019-001

The EPIG (ESA Probe for Investigation of the Giants) CDF study explored the feasibility of a European "stand-alone" mission to the Ice Giants (or Saturn as back-up). It corresponds to an ESA internal assessment of the capabilities to use only European technology to explore the outer planets.

The study was carried out by an interdisciplinary team of experts from ESA in eight sessions, starting with a kick-off on 28 March 2019 and ending with an Internal Final Presentation on 9 May 2019. This is a summary report of the EPIG CDF study. The full CDF study report will be made available at a later date.

Published: 16 July 2019

This brochure summarises the Herschel mission and its science achievements to date, capturing the basis for the science yet to come and its enduring legacy.

The European Space Agency's Herschel Space Observatory flew the largest single mirror ever built for a space telescope. At 3.5-metres in diameter the mirror collected long-wavelength radiation from some of the coldest and most distant objects in the Universe. In addition, Herschel was the only space observatory to cover a spectral range from the far infrared to sub-millimetre.

The Herschel mission leaves behind a lasting legacy in the form of a treasure trove of data, thousands of scientific papers, and a new generation of astronomers whose professional lives have been formed by working on this remarkable endeavour.

Contents:

  • Foreword
  • The other half of the light
  • Tools of the trade
  • The Herschel mission
  • Gathering the light
  • The infrared Universe
  • Origins
  • Engines of star formation
  • From dust to planets
  • The water trail
  • An international enterprise
  • A lasting legacy

Published: 09 May 2019

CHEOPS is ESA's CHaracterising ExOPlanet Satellite. It is the first mission dedicated to studying bright, nearby stars that are already known to host exoplanets, in order to make high-precision observations of the planet's size as it passes in front of its host star. It will focus on planets in the super-Earth to Neptune size range, with its data enabling the bulk density of the planets to be derived – a first-step characterisation towards understanding these alien worlds.

Contents

  • Why exoplanets
  • Enter CHEOPS
  • How CHEOPS will characterise exoplanets
  • Designing a planet watcher
  • A European collaboration
  • Welcome onboard!

Published: 27 March 2019
Evidence has mounted in recent decades that outflows of matter and energy from the central few parsecs of our Galaxy have shaped the observed structure of the Milky Way on a variety of larger scales. On scales of 15 parsecs, the Galactic Centre has bipolar lobes that can be seen in both the X-ray and radio parts of the spectrum, indicating broadly collimated outflows from the centre, directed perpendicular to the Galactic plane. On larger scales, approaching the size of the Galaxy itself, γ-ray observations have revealed the so-called 'Fermi bubble' features, implying that our Galactic Centre has had a period of active energy release leading to the production of relativistic particles that now populate huge cavities on both sides of the Galactic plane. The X-ray maps from the ROSAT all-sky survey show that the edges of these cavities close to the Galactic plane are bright in X-rays. At intermediate scales (about 150 parsecs), radio astronomers have observed the Galactic Centre lobe, an apparent bubble of emission seen only at positive Galactic latitudes, but again indicative of energy injection from near the Galactic Centre. Here we report prominent X-ray structures on these intermediate scales (hundreds of parsecs) above and below the plane, which appear to connect the Galactic Centre region to the Fermi bubbles. We propose that these structures, which we term the Galactic Centre 'chimneys', constitute exhaust channels through which energy and mass, injected by a quasi-continuous train of episodic events at the Galactic Centre, are transported from the central few parsecs to the base of the Fermi bubbles.
Published: 21 March 2019
Collisionless shocks are ubiquitous throughout the universe: around stars, supernova remnants, active galactic nuclei, binary systems, comets, and planets. Key information is carried by electromagnetic emissions from particles accelerated by high Mach number collisionless shocks. These shocks are intrinsically nonstationary, and the characteristic physical scales responsible for particle acceleration remain unknown. Quantifying these scales is crucial, as it affects the fundamental process of redistributing upstream plasma kinetic energy into other degrees of freedom—particularly electron thermalization. Direct in situ measurements of nonstationary shock dynamics have not been reported. Thus, the model that best describes this process has remained unknown. Here, we present direct evidence demonstrating that the transition to nonstationarity is associated with electron-scale field structures inside the shock ramp.
Published: 27 February 2019
Bilobate comets—small icy bodies with two distinct lobes—are a common configuration among comets, but the factors shaping these bodies are largely unknown. Cometary nuclei, the solid centres of comets, erode by ice sublimation when they are sufficiently close to the Sun, but the importance of a comet's internal structure on its erosion is unclear. Here we present three-dimensional analyses of images from the Rosetta mission to illuminate the process that shaped the Jupiter-family bilobate comet 67P/Churyumov–Gerasimenko over billions of years. We show that the comet's surface and interior exhibit shear-fracture and fault networks, on spatial scales of tens to hundreds of metres. Fractures propagate up to 500 m below the surface through a mechanically homogeneous material. Through fracture network analysis and stress modelling, we show that shear deformation generates fracture networks that control mechani-cal surface erosion, particularly in the strongly marked neck trough of 67P/Churyumov–Gerasimenko, exposing its interior. We conclude that shear deformation shapes and structures the surface and interior of bilobate comets, particularly in the outer Solar System where water ice sublimation is negligible.
Published: 18 February 2019
The 3D velocities of M31 and M33 are important for understanding the evolution and cosmological context of the Local Group. Their most massive stars are detected by Gaia, and we use Data Release 2 (DR2) to determine the galaxy proper motions (PMs). We select galaxy members based on, e.g., parallax, PM, color–magnitude diagram location, and local stellar density. The PM rotation of both galaxies is confidently detected, consistent with the known line-of-sight rotation curves: Vrot = -206 ± 86 km s-1 (counterclockwise) for M31, and Vrot = 80 ± 52 km s-1 (clockwise) for M33. We measure the center-of-mass PM of each galaxy relative to surrounding background quasars in DR2. This yields that (μα*δ) equals (65 ± 18, -57 ± 15) μas yr-1 for M31 and (31 ± 19, -29 ± 16) μas yr-1 for M33. In addition to the listed random errors, each component has an additional residual systematic error of 16 μas yr-1. These results are consistent at 0.8σ and 1.0σ with the (2 and 3 times higher accuracy) measurements already available from Hubble Space Telescope (HST) optical imaging and Very Long Baseline Array water maser observations, respectively. This lends confidence that all these measurements are robust. The new results imply that the M31 orbit toward the Milky Way (MW) is somewhat less radial than previously inferred, Vtan,DR2+HST = 57+35-31 km s-1, and strengthen arguments that M33 may be on its first infall into M31. The results highlight the future potential of Gaia for PM studies beyond the MW satellite system.
Published: 07 February 2019
We present the first extensive radio to γ-ray observations of a fast-rising blue optical transient, AT 2018cow, over its first ~100 days. AT 2018cow rose over a few days to a peak luminosity Lpk ~ 4 × 1044 erg s-1, exceeding that of superluminous supernovae (SNe), before declining as L ∝ t-2. Initial spectra at δt ≲ 15 days were mostly featureless and indicated large expansion velocities v ~ 0.1c and temperatures reaching T ~ 3 × 104 K. Later spectra revealed a persistent optically thick photosphere and the emergence of H and He emission features with v ~ 4000 km s-1 with no evidence for ejecta cooling. Our broadband monitoring revealed a hard X-ray spectral component at E ≥ 10 keV, in addition to luminous and highly variable soft X-rays, with properties unprecedented among astronomical transients. An abrupt change in the X-ray decay rate and variability appears to accompany the change in optical spectral properties. AT 2018cow showed bright radio emission consistent with the interaction of a blast wave with vsh ~ 0.1c with a dense environment (Ṁ ~ 10-3–10-4 Myr-1 for vw = 1000 km s-1). While these properties exclude 56Ni-powered transients, our multiwavelength analysis instead indicates that AT 2018cow harbored a "central engine," either a compact object (magnetar or black hole) or an embedded internal shock produced by interaction with a compact, dense circumstellar medium. The engine released ~1050–1051.5 erg over ~103–105 s and resides within low-mass fast-moving material with equatorial–polar density asymmetry (Mej,fast ≲ 0.3 M). Successful SNe from low-mass H-rich stars (like electron-capture SNe) or failed explosions from blue supergiants satisfy these constraints. [Remainder of abstract truncated due to character limitation]
Published: 06 February 2019
The concordance model (Λ cold dark matter (ΛCDM) model, where Λ is the cosmological constant) reproduces the main current cosmological observations1,2,3,4 assuming the validity of general relativity at all scales and epochs and the presence of CDM and of Λ, equivalent to dark energy with a constant density in space and time. However, the ΛCDM model is poorly tested in the redshift interval between the farthest observed type Ia supernovae5 and the cosmic microwave background. We present measurements of the expansion rate of the Universe based on a Hubble diagram of quasars. Quasars are the most luminous persistent sources in the Universe, observed up to redshifts of z ≈ 7.5 (refs. 6,7). We estimate their distances following a method developed by our group8,9,10, based on the X-ray and ultraviolet emission of the quasars. The distance modulus/redshift relation of quasars at z < 1.4 is in agreement with that of supernovae and with the concordance model. However, a deviation from the ΛCDM model emerges at higher redshift, with a statistical significance of ~4σ. If an evolution of the dark energy equation of state is allowed, the data suggest dark energy density increasing with time.
Published: 28 January 2019
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License.

The scale of groundwater upwelling on Mars, as well as its relation to sedimentary systems, remains an ongoing debate. Several deep craters (basins) in the northern equatorial regions show compelling signs that large amounts of water once existed on Mars at a planet-wide scale. The presence of water-formed features, including fluvial Gilbert and sapping deltas fed by sapping valleys, constitute strong evidence of groundwater upwelling resulting in long term standing bodies of water inside the basins. Terrestrial field evidence shows that sapping valleys can occur in basalt bedrock and not only in unconsolidated sediments. A hypothesis that considers the elevation differences between the observed morphologies and the assumed basal groundwater level is presented and described as the "dike-confined water" model, already present on Earth and introduced for the first time in the Martian geological literature. Only the deepest basins considered in this study, those with bases deeper than −4000 m in elevation below the Mars datum, intercepted the water-saturated zone and exhibit evidence of groundwater fluctuations. The discovery of these groundwater discharge sites on a planet-wide scale strongly suggests a link between the putative Martian ocean and various configurations of sedimentary deposits that were formed as a result of groundwater fluctuations during the Hesperian period. This newly recognized evidence of water-formed features significantly increases the chance that biosignatures could be buried in the sediment. These deep basins (groundwater-fed lakes) will be of interest to future exploration missions as they might provide evidence of geological conditions suitable for life.

Published: 21 January 2019
The tidal forces close to massive black holes can rip apart stars that come too close to them. As the resulting stellar debris spirals toward the black hole, it heats up and emits x-rays. We report observations of a stable 131-s x-ray quasi-periodic oscillation from the tidal disruption event ASASSN-14li. Assuming the black hole mass indicated by host galaxy scaling relations, this implies that (i) the periodicity originates from close to the event horizon, and (ii) the black hole is rapidly spinning. Our findings demonstrate that tidal disruption events can generate quasi-periodic oscillations which encode information about the physical properties of their black holes.
Published: 09 January 2019
White dwarfs are stellar embers depleted of nuclear energy sources that cool over billions of years. These stars, which are supported by electron degeneracy pressure, reach densities of 107 grams per cubic centimetre in their cores. It has been predicted that a first-order phase transition occurs during white-dwarf cooling, leading to the crystallization of the non-degenerate carbon and oxygen ions in the core, which releases a considerable amount of latent heat and delays the cooling process by about one billion years. However, no direct observational evidence of this effect has been reported so far. Here we report the presence of a pile-up in the cooling sequence of evolving white dwarfs within 100 parsecs of the Sun, determined using photometry and parallax data from the Gaia satellite. Using modelling, we infer that this pile-up arises from the release of latent heat as the cores of the white dwarfs crystallize. In addition to the release of latent heat, we find strong evidence that cooling is further slowed by the liberation of gravitational energy from element sedimentation in the crystallizing cores. Our results describe the energy released by crystallization in strongly coupled Coulomb plasmas, and the measured cooling delays could help to improve the accuracy of methods used to determine the age of stellar populations from white dwarfs.
Published: 09 January 2019

Document reference: CDF-187(C)

A mission to the Ice Giants (Neptune and Uranus) will be among the ones examined by the next Planetary Sciences Decadal, which also fits with the potential launch opportunity, with a Jupiter swing-by, that would allow to reach both planets by launching in the early 2030s.

ESA is exploring potential contributions to a NASA-led mission to the ice giants aimed at understanding the interior structure and bulk composition of the planet(s), including isotopes and noble gases.

ESA and NASA agreed to study a palette of possible configurations of varying cost to ESA and complexity, keeping in mind the need for clear interfaces.

It is important to keep this background in mind and remember that this study is not analysing a specific science proposal but trying to understand potential contributions following a top-down approach.

Requested by SCI-FM and funded by GSP, the M* (Ice Giants) study was set to analyse the feasibility of "stand-alone" elements provided by ESA to be part of the NASA-led mission to Uranus, Neptune and their moons (M-class mission budget but not proposed following a Cosmic Vision Programme Call, hence M*).

Published: 01 January 2019

The internal Phase 0 study of the M5 mission candidate THESEUS has been performed at ESA's Concurrent Design Facility (CDF) between June and November 2018. An internal final presentation has been prepared by the CDF Team, summarizing the outcome of the Phase 0 study. This presentation can be downloaded as a PDF (10 MB) by clicking the image to the right, or the 'link to publication' link below.

The internal final presentations of the internal Phase 0 studies of the other two M5 mission candidates, EnVision and SPICA, are also available.

Published: 21 December 2018

The internal Phase 0 study of the M5 mission candidate SPICA has been performed at ESA's Concurrent Design Facility (CDF) between June and November 2018. An internal final presentation has been prepared by the CDF Team, summarizing the outcome of the Phase 0 study. This presentation can be downloaded as a PDF (6 MB) by clicking the image to the right, or the 'link to publication' link below.

The internal final presentations of the internal Phase 0 studies of the other two M5 mission candidates, EnVision and THESEUS, are also available.

Published: 21 December 2018

The internal Phase 0 study of the M5 mission candidate EnVision has been performed at ESA's Concurrent Design Facility (CDF) between June and November 2018. An internal final presentation has been prepared by the CDF Team, summarizing the outcome of the Phase 0 study. This presentation can be downloaded as a PDF (10 MB) by clicking the image to the right, or the 'link to publication' link below.

The internal final presentations of the internal Phase 0 studies of the other two M5 mission candidates, SPICA and THESEUS, are also available.

Published: 21 December 2018
The bulk of stars in galaxy clusters are confined within their constituent galaxies. Those stars do not trace the extended distribution of dark matter well as they are located in the central regions of the cluster's dark matter subhaloes. A small fraction of stars is expected, however, to follow the global dark matter shape of the cluster. These are the stars whose extended spatial distribution results from the merging activity of galaxies and form the intracluster light (ICL). In this work, we compare the bi-dimensional distribution of dark matter in massive galaxy clusters (as traced by gravitational lensing models) with the distribution of the ICL. To do that, we use the superb data from the Hubble Frontier Fields Initiative. Using the Modified Hausdorff distance (MHD) as a way of quantifying the similarities between the mass and ICL distributions, we find an excellent agreement (MHD ~25 kpc) between the two components. This result shows that the ICL exquisitely follows the global dark matter distribution, providing an accurate luminous tracer of dark matter. This finding opens up the possibility of exploring the distribution of dark matter in galaxy clusters in detail using only deep imaging observations.
Published: 24 October 2018

Reference: ESA/SCI(2018)1

SMILE (Solar wind Magnetosphere Ionosphere Link Explorer) was selected from a pool of 13 potential missions that were proposed to the European Space Agency (ESA) and the Chinese Academy of Sciences (CAS) as a result of a joint call for mission concepts in June 2015.

Following its selection in November 2015, detailed studies were performed by ESA, CAS, three European industrial contractors and the Science Study Team to finalise the mission architecture, including the space and ground elements that are required to fulfil the science requirements. This report, also known as the Red Book, summarizes the SMILE definition study.

Published: 17 December 2018
13-Dec-2019 07:54 UT

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