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Artist concept of ESA's future Plato Space Telescope. Image via Thales Alenia Space.
The search for exoplanets – planets orbiting other stars – has really intensified in recent years. New telescopes, both space and ground-based, have been launched, constructed and under development. These efforts have already discovered thousands exoplanets, confirmed candidates and additional candidates. On October 4, 2018, the initial construction of one of the latest additions to the family of exoplanet hunters was announced – the Plato mission of the European Space Agency. The announcement was made at the 69th International Astronautical Congress in Bremen, Germany, where the new contract was signed.
The contract includes the delivery of the satellite, the test phase leading to the launch, assistance during the launch campaign and the in-orbit commissioning phase. Plato will be built and assembled by satellite manufacturer OHB System in collaboration with Thales Alenia Space (in France and the UK) and RUAG Space in Switzerland, as well as contributors from many other ESA Member States. The main scientific instrument, a set of 26 cameras and electronic units, will observe much of the sky. According to Ana Heras, scientist of the Plato project at ESA:
Plato is a new generation exoplanet mission that will monitor thousands of bright stars across much of the sky in search of tiny, steady drops in brightness caused by transiting planets. Since the planets block only a tiny fraction of the light emitted by their parent star, this quest requires extremely precise and long-term photometric observations.
The design of Thales Alenia Space for Plato. Image via ESA.
The EADS Astrium design for Plato. Image via ESA.
NASA's Kepler Space Telescope has detected most of these new worlds, but this mission is about to be completed as the satellite runs out of fuel. The TESS telescope, launched just a few months ago, has already found its first two planets after starting scientific operations more recently. Kepler's focus is on finding planets of varying sizes and masses around stars at many light-years away. TESS will observe brighter stars much closer to our solar system, focusing on planets of the same size as the Earth, including in the habitable areas of their stars. where liquid water could exist on their surfaces.
So how does Plato compare? Plato – the PLAnetary Transits and Oscillations of Stars mission – will not launch until 2026, but it should be worth the wait. Like TESS, its main goal will be to search for rocky planets orbiting living areas of sun-like stars. According to Johann-Dietrich Wörner, Director General of ESA, he will attempt to answer a key question:
Does a second Earth exist in the universe? is one of the exciting questions in astrophysics today. With our Plato satellite, we focus on Earth-like planets that revolve around the habitable zone surrounding other stars similar to our sun. This will be a major step in the search for another Earth.
Comparison of the areas of the sky already observed by Corot and Kepler and future targets Plato. The clearest "step-by-step" target areas are tentative because their exact location has not yet been determined. Image via CNES / ESA.
Although Plato focuses on the search for planets, he will also examine their masses, sizes and ages with unprecedented accuracy, and will also study the properties of host stars, even the seismic activity of the latter, called asteroseismology, which will help scientists better understand stellar interiors and evolution. Plato will be able to determine the mass of a star with an accuracy of 1%. By examining in detail the properties of the planets themselves, scientists will be able to determine the architecture of the exoplanetary systems and determine if they can harbor habitable worlds.
Plato will operate at L2 Lagrange point in the space – 1.53 km (1.53 km) beyond the Earth, as seen from the sun. Its nominal mission will last six years, in three stages. The first two will be long-term observations, centered on two fields of the sky supposed to contain a high density of cold dwarf stars and designed to detect transits with an orbital period similar to that of the Earth. The first phase of observation will last two to three years and the second two years. The third and final phase of the mission will be a step-by-step phase, during which different parts of the sky will be monitored for a few months each and will last at least a year.
Plato will operate at the second Lagrange sun-Earth point (L2), 1.5 million kilometers from the Earth. Image via ESA.
Plato will be a follow-up mission to Cheops, ESA's next planetary hunter. Cheops will be launched much earlier – next year – and will lead to more detailed studies of previously known exoplanets, particularly super-Earths – rocky planets larger than Earth but smaller than Neptune – and analogues of the size of Neptune.
After Platon, the AERIAL mission (a large geodetic infrared survey with atmospheric remote sensing) will be launched in 2028 to observe a wide range of exoplanets – rocky worlds to gaseous giants – and examine their atmosphere, like the next James Webb of the NASA Telescope (JWST).
The study of the atmosphere of the planets is essential to try to determine which are habitable – or even inhabited. JWST will even be able to search for biomarker gases in the atmospheres, which, if detected, would provide irrefutable evidence of active biology.
Plato will search for rocky exoplanets in the habitable areas of their stars. Image via NASA Ames / JPL-Caltech / T. Pyle.
The beginning of the construction of Plato is exciting, although the launch is still far away. As Filippo Marliani, Plato Project Manager at ESA, noted:
We are excited to launch the construction of this exciting mission. With the master builder and the support of the European space industry, we look forward to building a spacecraft that will tackle some of humanity's deepest questions.
In summary: The Plato mission will be an important mission in the search for rocky and potentially habitable planets, like the Earth orbiting other stars. Astronomers focus on these worlds because they are the most likely to be able to support life.
Via ESA
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