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Exoplanet imaginarium
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    Exoplanet imaginarium
    Exoplanet imaginarium

    ESA is preparing for the launch of the first in a series of three exoplanet missions designed to tackle different aspects of the evolving field of exoplanet science. Cheops, the Characterising Exoplanet Satellite, is scheduled for launch in late 2019, and will make precise measurements of planets known to be orbiting around nearby bright stars. It will focus particularly on stars with Earth- to Neptune-sized planets. By determining the size of the planet, and combining this with known measurements of the planets’ masses, Cheops will allow the density of the planet to be estimated, and therefore enable a first step towards characterising the nature of these planets – from lava worlds to rocky Earth-like planets, to gas planets or even ocean worlds.

    The artist impressions depicted in this montage imagine some of the different types of exoplanets and their host stars that might be studied by Cheops.

    In the next decade, Plato, the PLAnetary Transits and Oscillations of stars mission will be launched. It is a next-generation planet hunter with an emphasis on the properties of rocky planets in orbits up to the ‘habitable zone’ – where liquid water can exist on the planet’s surface – around Sun-like stars. It will also investigate seismic activity in stars, which will enable precise characterisation of the planet’s host star, including its age, providing insight into the age and evolutionary state of the planet system.

    Also scheduled to launch in the next decade, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission, Ariel, will take exoplanet characterisation one step further, performing a chemical census of a large and diverse sample of exoplanets by analysing their atmospheres. This will enable the study of exoplanets both as individuals and, importantly, as populations, in greater detail than ever.

    Cheops will also help provide targets for other missions, including the international James Webb Space Telescope, which will be used to search for the signatures of water and methane, important elements in our quest for signs of habitability.

    Together with Cheops, these future missions will keep ESA at the forefront of exoplanet research well beyond the next decade, and will build on answering the fundamental question: what are the conditions for planet formation and the emergence of life?

    Long-term planning is crucial to realise the missions that investigate fundamental science questions, and to ensure the continued development of innovative technology, inspiring new generations of European scientists and engineers.

    Science is everywhere at ESA. As well as exploring the Universe and answering the big questions about our place in space we develop the satellites, rockets and technologies to get there. Science also helps us to care for our home planet. All this week we're highlighting different aspects of science at ESA. Join the conversation with #ScienceAtESA

    Credits: ESA
    Cheops, ESA’s first exoplanet mission
    Cheops, ESA’s first exoplanet mission

    Artist impression of Cheops, the Characterising Exoplanet Satellite, with an exoplanet system in the background.

    In reality, Cheops will be situated in Earth orbit, and will study exoplanet systems from afar, making precise measurements of the planet’s size as it moves in front of its host star. These measurements, combined with known information about the mass of the planet based on independent observations, will allow the density of the planet to be estimated. This will constrain the planet’s possible composition and structure, indicating for example if it is predominantly rocky or gaseous, or perhaps harbours significant oceans. Cheops will focus particularly on bright stars hosting Earth- to Neptune-sized planets. This first-step characterisation of these worlds – many with no Solar System equivalents – is a critical process towards understanding the formation, origin and evolution of exoplanets in this size range.

    Cheops paves the way for the next generation of ESA’s exoplanet satellites, with two further missions – Plato and Ariel – planned for the next decade to tackle different aspects of the evolving field of exoplanet science.

    Credits: ESA/ATG medialab
    What kind of planets will Cheops study?
    What kind of planets will Cheops study?

    The Characterising Exoplanet Satellite, Cheops, will make measurements of alien worlds that will help determine their nature. It will focus on Earth-to-Neptune sized planets orbiting nearby bright stars, and will measure the size of the planet as it transits in front of the star.

    Combined with known information about the mass of the planet, these data will enable scientists to distinguish between a dense rocky world or rather more gaseous, a water-world or an ice-rich planet – as represented from left to right in this artist impression.

    Cheops will identify which planets are rather more similar in composition to Mercury, Venus, Earth and Mars in our own Solar System, or if they resemble small versions of the outer Solar System’s gas giants like Neptune or Uranus. It will also be able to identify hot-Jupiters – large gas planets similar in mass and size to Jupiter but orbiting very close to their host stars – or rather smaller and rocky lava worlds orbiting close to their star.

    This first-step characterisation of these worlds – many with no Solar System equivalents – is a critical process towards understanding the formation, origin and evolution of these small exoplanets.

    Credits: ESA
    Transiting exoplanets
    Transiting exoplanets

    Artist impression showing three planets orbiting across the face of their host star.

    Watching as a star’s light decreases due to a planet transiting in front of it is one way to discover and investigate planets around other stars outside of our own Solar System.

    ESA’s Characterising Exoplanet Satellite, Cheops, will study known transiting planets around bright stars in order to build up precise measurements of their size. Together with known information about their mass, it will then be possible to determine the density of the planet. This will constrain the planet’s possible composition and structure, indicating for example if it is predominantly rocky or gaseous, or perhaps harbours significant oceans. Cheops will focus particularly on bright stars hosting Earth- to Neptune-sized planets. This first-step characterisation of these worlds – many with no Solar System equivalents – is a critical process towards understanding the formation, origin and evolution of exoplanets in this size range.

    Credits: ESA
    Exoplanet system
    Exoplanet system

    Artist’s impression of an exoplanet system featuring three planets imagined as two gaseous planets orbiting close to the star – perhaps ‘hot-Jupiters’ – and an icy world further away (foreground).

    Combined with known information about the mass of the planet, measurements made by ESA’s upcoming Cheops – Characterising Exoplanet Satellite – will allow the density of exoplanets to be estimated, and as such the nature and composition of the planets to be inferred. The data will enable scientists to distinguish between a dense rocky world or rather more gaseous, a water-world or an ice-rich planet, for example.

    Cheops will identify which planets are rather more similar in composition to Mercury, Venus, Earth or Mars in our own, inner, Solar System, or if they resemble the outer Solar System’s gas giants like Neptune or Uranus. It will also identify between hot-Jupiters – giant gas planets similar in mass and size to Jupiter but orbiting very close to their host stars – or rather small and rocky lava worlds orbiting close to their star.

    This first-step characterisation of these worlds – many with no Solar System equivalents – is a critical process towards understanding the formation, origin and evolution of these small exoplanets.

    Credits: ESA
    Exoplanet and star
    Exoplanet and star

    Artist’s impression of an exoplanet orbiting a star.

    Credits: ESA
    Exoplanet system
    Exoplanet system

    Artist’s impression of an exoplanet system.

    Credits: ESA
    Exoplanet system
    Exoplanet system

    Artist’s impression of an exoplanet system.

    Credits: ESA
    Transiting exoplanet
    Transiting exoplanet

    Artist impression of a small, rocky planet – perhaps one flooded with lava – transiting across the face of its parent star.

    ESA’s Characterising Exoplanet Satellite, Cheops, will study known transiting planets to build up precise measurements of their size. Together with known information about the mass of the planet, Cheops will allow the density of the planet to be estimated. This will constrain the planet’s possible composition and structure, indicating for example if it is predominantly rocky or gaseous, or perhaps harbours significant oceans. Cheops will focus particularly on bright stars hosting Earth- to Neptune-sized planets. This first-step characterisation of these worlds – many with no Solar System equivalents – is a critical process towards understanding the formation, origin and evolution of exoplanets in this size range.

    Credits: ESA
    Searching for exoplanetary systems
    Searching for exoplanetary systems

    The PLAnetary Transits and Oscillations of stars (PLATO) mission will identify and study thousands of exoplanetary systems, with an emphasis on discovering and characterising Earth-sized planets and super-Earths. It will also investigate seismic activity in stars, enabling a precise characterisation of the host sun of each planet discovered, including its mass, radius and age.

    Plato is ESA’s third medium-class science mission and is planned for launch by 2026.

    Credits: ESA–C. Carreau
    Exoplanet mission timeline
    Exoplanet mission timeline

    The first discoveries of exoplanets in the 1990s, by ground-based observatories, completely changed our perspective of the Solar System and opened up new areas of research that continues today. This infographic highlights the main space-based contributors to the field, including not only exoplanet-dedicated missions, but also exoplanet-sensitive missions, past, present and future.

    One of the first exoplanet-sensitive space telescopes was the CNES-led Convection, Rotation and planetary Transits mission, CoRoT, which launched in 2006. While focused on studies of stars, it uncovered exoplanets using the transit method.

    NASA’s 2009 Kepler mission is an exoplanet discovery machine, accounting for around three-quarters of all exoplanet discoveries so far. It looks at a specific patch of sky for a lengthy period of time, so is sensitive to a great number of faint stars.

    Meanwhile, telescopes that were launched even before the first discoveries were confirmed, such as the NASA/ESA Hubble Space Telescope, have been contributing to the evolving field.

    ESA’s Gaia mission, through its unprecedented all-sky survey of the position, brightness and motion of over one billion stars, is providing a large database to search for exoplanets. These will be uncovered through the changes in the star’s motion as the planet or planets orbit around it, or by the dip in the star’s brightness as the planet transits across its face.

    The most recent addition to the exoplanet-hunting fleet is NASA’s Transiting Exoplanet Survey Satellite, Tess, launched in April 2018. It is the first all-sky transit survey satellite.

    But discovering an exoplanet is just the beginning: dedicated telescopes are needed to follow up on this ever-growing catalogue to understand their properties, to get closer to knowing if another Earth-like planet exists, and better understanding what conditions are needed for planet formation and the emergence of life.

    ESA is launching three dedicated exoplanet satellites in the next decade, each tackling a unique topic.

    The Characterising Exoplanet Satellite, Cheops, will observe bright stars known to host exoplanets, in particular Earth-to-Neptune-sized planets, anywhere in the sky. By knowing exactly where and when to look for transits, and being able to return to repeatedly observe the same targets, Cheops will become the most efficient instrument to study individual exoplanets. It will record the precise sizes of these relatively small planets and combined with mass measurements already calculated from other observatories, will enable the planet’s density to be determined, and thus make a first-step characterisation of the nature of these worlds.

    Cheops will also identify candidates for additional study by future missions. For example, it will provide well-characterised targets for the international James Webb Space Telescope, which will perform further detailed studies of their atmospheres.

    Plato, the PLAnetary Transits and Oscillations of stars mission, is a next-generation planet hunter with an emphasis on the properties of rocky planets up to the habitable zone around Sun-like stars – the location from a star where liquid water can exist on the planet’s surface. Importantly, it will also analyse the planet’s host star, including its age, and thus give insight into the evolutionary state of the entire extrasolar system.

    Ariel, the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey mission, will perform a chemical census of a large and diverse sample of exoplanets by analysing their atmospheres in great detail.

    With the complementary work of both ground- and space-based observatories, we will get closer to understanding one of humanity’s biggest questions: are we alone in the Universe?

    Credits: ESA

    Exoplanet imaginarium

    Imagine the alien worlds ESA will investigate with its three generations of exoplanet missions