Unlike previous satellites designed to find new exoplanets – planets orbiting stars other than our Sun – by observing tens of thousands of stars simultaneously, CHEOPS has been optimized to observe a single star at a time and it targets stars already known to host exoplanets. The aim of CHEOPS is therefore to go beyond a mere census of exoplanets, and measure some of their key characteristics, in particular their size, with an exquisite precision. This precision is what allows astronomer to infer what these planets are made of: combining the CHEOPS size measurement with the previously known planet mass yields the density: dense planets like the Earth are mainly composed of rocks and metals, while planets with low densities like Jupiter are mostly made out of gas. Since these compositions are the result of the planet formation process, getting to know them opens a window to the past history of planetary systems, putting our own Solar System in context.

Observation of exoplanet properties

“In this respect, the mission has been extremely successful,” highlights Willy Benz, Professor emeritus of astrophysics at the University of Bern and head of the CHEOPS consortium, “the precision of CHEOPS has exceeded all expectations and has allowed us to determine properties of several of the most interesting exoplanets.”

For example, by closely observing how the luminosity changes as the planet WASP-103b passes in front of its star, scientists from the CHEOPS team have observed that the planet is deformed into the shape of a rugby ball due to the intense gravity of the nearby star. Such planets are so hot that CHEOPS has also been able to detect them glowing along their orbit around their stars. “The glow detected with CHEOPS for the planet WASP-189b is only a few millionth of the light emitted by the star, and is related to the temperature of the planet atmosphere and its cloud coverage. So it is clear that CHEOPS can do much more than ‘simply’ measuring planet sizes,” explains Prof. David Ehrenreich of the University of Geneva, who is co-chairing the international team of over a hundred of scientists involved in the exploitation of the mission.

More exciting discoveries with the extended mission

The primary mission of CHEOPS was planned to last for three and a half years, that is until September 2023. The outstanding quality of the science produced by the mission is attested by the publication of over fifty scientific articles based on CHEOPS data in international journals. The satellite was successfully operated amidst a global pandemic, and its health is excellent with respect to the harsh conditions of space, where it is constantly bombarded by cosmic rays and high-energy radiation. All these elements have pushed the CHEOPS team to propose extending the mission beyond 2023.

The extension of CHEOPS operations has now been confirmed by the ESA Science Programme Committee until at least 2026, provided ongoing support from national contributors and partners. The CHEOPS team members are originating from 40 institutions across Europe: in addition to ESA, 11 countries, including Switzerland in a leading role, have come together to fund and build the telescope between 2012 and 2019. “CHEOPS can continue to count on the strong support of the participating Funding Agencies, including Switzerland, for the extension of the mission, and that the Swiss lead in the CHEOPS mission (including its extended operations) is possible due to the membership of Switzerland in ESA and through its participation in the PRODEX program,” says Oliver Botta, chair of the CHEOPS Steering Committee.

With the newly approved mission extension, the CHEOPS team plans to continue using CHEOPS for what it does best while at the same time trying out new observations. “We have only scratched the surface of the capabilities of CHEOPS, there is much more science that can be done with the satellite and we look forward to exploring it during the extension,” declares Benz. “A very exciting result would be the discovery of the first exomoon,” reveals Ehrenreich. “Many planets in our Solar System have moons, so we expect to find some around exoplanets, and we are currently observing some candidates. It is challenging to detect exomoons though, because they are small, hence their signatures are faint. However, CHEOPS is precise enough to find exomoons as small as the planet Mars, which is twice the size of our Moon. If such moons exist in the systems we observe, we could find them during the extended mission.”

A unique role in the landscape of space missions

Another unique characteristic of CHEOPS is its ability to combine forces with other space missions such as the James Webb Space Telescope (JWST), which is a joint mission of NASA and ESA. CHEOPS can refine our knowledge of already known exoplanets to select the best candidates to be observed with JWST to probe the atmospheres of these planets. “Thanks to CHEOPS observations, we have been granted valuable JWST time to observe the planets in the TOI-178 system to determine their atmospheric composition, which will help to understand the dynamical history of the system,” specifies Prof. Yann Alibert of the University of Bern. Alibert is coordinating the CHEOPS program dedicated to the follow-up of multiplanetary systems discovered by NASA’s satellite TESS. “This is an example of a great synergy between CHEOPS and other missions: TESS originally found 3 planets orbiting the star TOI-178. When CHEOPS looked at this system, it discovered three more planets and revealed an outstanding and fragile orbital harmony, leading us to hypothesize that it has been unperturbed for billions of years,” explains Alibert.

“Scientists are eager to find out what surprising results CHEOPS will bring next; what is sure now is that CHEOPS will continue to make new discoveries for years to come,” concludes Benz.

Unlike previous satellites designed to find new exoplanets – planets orbiting stars other than our Sun – by observing tens of thousands of stars simultaneously, CHEOPS has been optimized to observe a single star at a time and it targets stars already known to host exoplanets. The aim of CHEOPS is therefore to go beyond a mere census of exoplanets, and measure some of their key characteristics, in particular their size, with an exquisite precision. This precision is what allows astronomer to infer what these planets are made of: combining the CHEOPS size measurement with the previously known planet mass yields the density: dense planets like the Earth are mainly composed of rocks and metals, while planets with low densities like Jupiter are mostly made out of gas. Since these compositions are the result of the planet formation process, getting to know them opens a window to the past history of planetary systems, putting our own Solar System in context.

Observation of exoplanet properties

“In this respect, the mission has been extremely successful,” highlights Willy Benz, Professor emeritus of astrophysics at the University of Bern and head of the CHEOPS consortium, “the precision of CHEOPS has exceeded all expectations and has allowed us to determine properties of several of the most interesting exoplanets.”

For example, by closely observing how the luminosity changes as the planet WASP-103b passes in front of its star, scientists from the CHEOPS team have observed that the planet is deformed into the shape of a rugby ball due to the intense gravity of the nearby star. Such planets are so hot that CHEOPS has also been able to detect them glowing along their orbit around their stars. “The glow detected with CHEOPS for the planet WASP-189b is only a few millionth of the light emitted by the star, and is related to the temperature of the planet atmosphere and its cloud coverage. So it is clear that CHEOPS can do much more than ‘simply’ measuring planet sizes,” explains Prof. David Ehrenreich of the University of Geneva, who is co-chairing the international team of over a hundred of scientists involved in the exploitation of the mission.

More exciting discoveries with the extended mission

The primary mission of CHEOPS was planned to last for three and a half years, that is until September 2023. The outstanding quality of the science produced by the mission is attested by the publication of over fifty scientific articles based on CHEOPS data in international journals. The satellite was successfully operated amidst a global pandemic, and its health is excellent with respect to the harsh conditions of space, where it is constantly bombarded by cosmic rays and high-energy radiation. All these elements have pushed the CHEOPS team to propose extending the mission beyond 2023.

The extension of CHEOPS operations has now been confirmed by the ESA Science Programme Committee until at least 2026, provided ongoing support from national contributors and partners. The CHEOPS team members are originating from 40 institutions across Europe: in addition to ESA, 11 countries, including Switzerland in a leading role, have come together to fund and build the telescope between 2012 and 2019. “CHEOPS can continue to count on the strong support of the participating Funding Agencies, including Switzerland, for the extension of the mission, and that the Swiss lead in the CHEOPS mission (including its extended operations) is possible due to the membership of Switzerland in ESA and through its participation in the PRODEX program,” says Oliver Botta, chair of the CHEOPS Steering Committee.

With the newly approved mission extension, the CHEOPS team plans to continue using CHEOPS for what it does best while at the same time trying out new observations. “We have only scratched the surface of the capabilities of CHEOPS, there is much more science that can be done with the satellite and we look forward to exploring it during the extension,” declares Benz. “A very exciting result would be the discovery of the first exomoon,” reveals Ehrenreich. “Many planets in our Solar System have moons, so we expect to find some around exoplanets, and we are currently observing some candidates. It is challenging to detect exomoons though, because they are small, hence their signatures are faint. However, CHEOPS is precise enough to find exomoons as small as the planet Mars, which is twice the size of our Moon. If such moons exist in the systems we observe, we could find them during the extended mission.”

A unique role in the landscape of space missions

Another unique characteristic of CHEOPS is its ability to combine forces with other space missions such as the James Webb Space Telescope (JWST), which is a joint mission of NASA and ESA. CHEOPS can refine our knowledge of already known exoplanets to select the best candidates to be observed with JWST to probe the atmospheres of these planets. “Thanks to CHEOPS observations, we have been granted valuable JWST time to observe the planets in the TOI-178 system to determine their atmospheric composition, which will help to understand the dynamical history of the system,” specifies Prof. Yann Alibert of the University of Bern. Alibert is coordinating the CHEOPS program dedicated to the follow-up of multiplanetary systems discovered by NASA’s satellite TESS. “This is an example of a great synergy between CHEOPS and other missions: TESS originally found 3 planets orbiting the star TOI-178. When CHEOPS looked at this system, it discovered three more planets and revealed an outstanding and fragile orbital harmony, leading us to hypothesize that it has been unperturbed for billions of years,” explains Alibert.

“Scientists are eager to find out what surprising results CHEOPS will bring next; what is sure now is that CHEOPS will continue to make new discoveries for years to come,” concludes Benz.

Unlike previous satellites designed to find new exoplanets – planets orbiting stars other than our Sun – by observing tens of thousands of stars simultaneously, CHEOPS has been optimized to observe a single star at a time and it targets stars already known to host exoplanets. The aim of CHEOPS is therefore to go beyond a mere census of exoplanets, and measure some of their key characteristics, in particular their size, with an exquisite precision. This precision is what allows astronomer to infer what these planets are made of: combining the CHEOPS size measurement with the previously known planet mass yields the density: dense planets like the Earth are mainly composed of rocks and metals, while planets with low densities like Jupiter are mostly made out of gas. Since these compositions are the result of the planet formation process, getting to know them opens a window to the past history of planetary systems, putting our own Solar System in context.

Observation of exoplanet properties

“In this respect, the mission has been extremely successful,” highlights Willy Benz, Professor emeritus of astrophysics at the University of Bern and head of the CHEOPS consortium, “the precision of CHEOPS has exceeded all expectations and has allowed us to determine properties of several of the most interesting exoplanets.”

For example, by closely observing how the luminosity changes as the planet WASP-103b passes in front of its star, scientists from the CHEOPS team have observed that the planet is deformed into the shape of a rugby ball due to the intense gravity of the nearby star. Such planets are so hot that CHEOPS has also been able to detect them glowing along their orbit around their stars. “The glow detected with CHEOPS for the planet WASP-189b is only a few millionth of the light emitted by the star, and is related to the temperature of the planet atmosphere and its cloud coverage. So it is clear that CHEOPS can do much more than ‘simply’ measuring planet sizes,” explains Prof. David Ehrenreich of the University of Geneva, who is co-chairing the international team of over a hundred of scientists involved in the exploitation of the mission.

More exciting discoveries with the extended mission

The primary mission of CHEOPS was planned to last for three and a half years, that is until September 2023. The outstanding quality of the science produced by the mission is attested by the publication of over fifty scientific articles based on CHEOPS data in international journals. The satellite was successfully operated amidst a global pandemic, and its health is excellent with respect to the harsh conditions of space, where it is constantly bombarded by cosmic rays and high-energy radiation. All these elements have pushed the CHEOPS team to propose extending the mission beyond 2023.

The extension of CHEOPS operations has now been confirmed by the ESA Science Programme Committee until at least 2026, provided ongoing support from national contributors and partners. The CHEOPS team members are originating from 40 institutions across Europe: in addition to ESA, 11 countries, including Switzerland in a leading role, have come together to fund and build the telescope between 2012 and 2019. “CHEOPS can continue to count on the strong support of the participating Funding Agencies, including Switzerland, for the extension of the mission, and that the Swiss lead in the CHEOPS mission (including its extended operations) is possible due to the membership of Switzerland in ESA and through its participation in the PRODEX program,” says Oliver Botta, chair of the CHEOPS Steering Committee.

With the newly approved mission extension, the CHEOPS team plans to continue using CHEOPS for what it does best while at the same time trying out new observations. “We have only scratched the surface of the capabilities of CHEOPS, there is much more science that can be done with the satellite and we look forward to exploring it during the extension,” declares Benz. “A very exciting result would be the discovery of the first exomoon,” reveals Ehrenreich. “Many planets in our Solar System have moons, so we expect to find some around exoplanets, and we are currently observing some candidates. It is challenging to detect exomoons though, because they are small, hence their signatures are faint. However, CHEOPS is precise enough to find exomoons as small as the planet Mars, which is twice the size of our Moon. If such moons exist in the systems we observe, we could find them during the extended mission.”

A unique role in the landscape of space missions

Another unique characteristic of CHEOPS is its ability to combine forces with other space missions such as the James Webb Space Telescope (JWST), which is a joint mission of NASA and ESA. CHEOPS can refine our knowledge of already known exoplanets to select the best candidates to be observed with JWST to probe the atmospheres of these planets. “Thanks to CHEOPS observations, we have been granted valuable JWST time to observe the planets in the TOI-178 system to determine their atmospheric composition, which will help to understand the dynamical history of the system,” specifies Prof. Yann Alibert of the University of Bern. Alibert is coordinating the CHEOPS program dedicated to the follow-up of multiplanetary systems discovered by NASA’s satellite TESS. “This is an example of a great synergy between CHEOPS and other missions: TESS originally found 3 planets orbiting the star TOI-178. When CHEOPS looked at this system, it discovered three more planets and revealed an outstanding and fragile orbital harmony, leading us to hypothesize that it has been unperturbed for billions of years,” explains Alibert.

“Scientists are eager to find out what surprising results CHEOPS will bring next; what is sure now is that CHEOPS will continue to make new discoveries for years to come,” concludes Benz.

Quelle: University of Bern

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Update: 19.03.2023

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Europe's exoplanet-hunting CHEOPS mission extended through 2026

'We have only scratched the surface of the capabilities of CHEOPS.'

Europe's CHEOPS spacecraft will continue investigating planets outside our solar system until at least 2026.

The European Space Agency (ESA) announced on March 9 that CHEOPS will continue its exoplanet-studying mission — which includes selecting "golden target" worlds for deeper investigation by the James Webb Space Telescope (JWST) — for at least another three years, with the potential to extend this further until 2029.

Launched in December 2019 from ESA’s spaceport in French Guiana, CHEOPS (short for "Characterising Exoplanet Satellite") is designed to study planets with sizes between that of Earth and of Neptune as they cross, or transit, the face of bright stars. But it has had impressive results with objects well outside this size range.

The mission has taken exoplanet science beyond simple detection, to a deeper investigation of the atmospheres of these worlds as well as accurately measuring their size and shape. Exoplanets with interesting atmospheric compositions can then be passed to more powerful telescopes like JWST, meaning CHEOPS plays a key role in our hunt for planets that could potentially support life.

"In this respect, the mission has been extremely successful," CHEOPS consortium head Willy Benz, a professor emeritus of astrophysics at the University of Bern in Switzerland, said in a statement(opens in new tab). "The precision of CHEOPS has exceeded all expectations and has allowed us to determine properties of several of the most interesting exoplanets."

An example of CHEOPS' contribution to science was the discovery that the gas giant WASP-103 b, first spotted in 2014, has a distended, flattened shape similar to that of a rugby ball. The ESA spacecraft made this determination in 2021 by examining the brightness drop the planet causes as it transits the face of its star. 

The compressed shape of WASP-103 b is believed to be the result of tidal interactions with its parent star, and the revelation marked the first time the shape of an exoplanet had been so well defined. 

CHEOPS has also had an impact closer to home. Just this year, observations from the spacecraft were used to discover that Quaoar, a dwarf planet in our solar system, is surrounded by a ring of dust. The ring is exceptional because it is farther out from its parent body than any ring previously discovered, challenging theories of how such structures form.

An artist’s impression of the dwarf planet Quaoar and its ring. Quaoar’s moon Weywot is shown on the left.  (Image credit: ESA)

The primary science mission of CHEOPS was only initially planned to last for three and a half years, until September 2023, but ESA said the spacecraft is in excellent health after over three years in Earth orbit. 

During this time, CHEOPS has coped admirably with the rigors of space, such as the bombardment of cosmic rays and high-energy radiation, while on Earth its operating team worked to keep the spacecraft operational through the global pandemic. 

There are many exciting observing opportunities left for CHEOPS. For example, the mission team hopes to use the spacecraft to discover the first exomoon —  a moon orbiting a planet outside the solar system. Exomoons are tough to spot due to their comparatively small size and thus the faint signature they cause as they pass in front of a star, but the CHEOPS team thinks the spacecraft is sensitive enough to make such a detection.

"We have only scratched the surface of the capabilities of CHEOPS. There is much more science that can be done with the satellite, and we look forward to exploring it during the extension," Benz said. "Scientists are eager to find out what surprising results CHEOPS will bring next; what is sure now is that CHEOPS will continue to make new discoveries for years to come."

Quelle: SC

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Update: 10.06.2023

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Elusive planets play “hide and seek” with CHEOPS

With the help of the CHEOPS space telescope an international team of European astronomers managed to clearly identify the existence of four new exoplanets. The four mini-Neptunes are smaller and cooler, and more difficult to find than the so-called Hot Jupiter exoplanets which have been found in abundance. Two of the four resulting papers are led by researchers from the University of Bern and the University of Geneva who are also members of the National Centre of Competence in Research (NCCR) PlanetS.

CHEOPS is a joint mission by the European Space Agency (ESA) and Switzerland, under the leadership of the University of Bern in collaboration with the University of Geneva. Since its launch in December 2019, the extremely precise measurements of CHEOPS have contributed to several key discoveries in the field of exoplanets.

NCCR PlanetS members Dr. Solène Ulmer-Moll of the Universities of Bern and Geneva, and Dr. Hugh Osborn of the University of Bern, exploited the unique synergy of CHEOPS and the NASA satellite TESS, in order to detect a series of elusive exoplanets. The planets, called TOI 5678 b and HIP 9618 c respectively, are the size of Neptune or slightly smaller with 4.9 and 3.4 Earth radii. The respective papers have just been published in the journals Astronomy & Astrophysics andMonthly Notices of the Royal Astronomical Society. Publishing in the same journals, two other members of the international team, Amy Tuson from the University of Cambridge (UK) and Dr. Zoltán Garai from the "ELTE Gothard Astrophysical Observatory (Hungary), used the same technique to identify two similar planets in other systems.

The synergy of two satellites

The CHEOPS satellite observes the luminosity of stars in order to capture the slight dimming that occurs when, and if, an orbiting planet happens to pass in front of its star from our point of view. By searching for these dimming events, called “transits”, scientists have been able to discover the majority of the thousands of exoplanets known to orbit stars other than our Sun.

“NASA’s TESS satellite excels at detecting the transits of exoplanets, even for the most challenging small planets. However, it changes its field of view every 27 days in order to scan rapidly most of the sky, which prevents it from finding planets on longer orbital periods,” explains Hugh Osborn. Still, the TESS satellite was able to observe single transits around the stars TOI 5678 and HIP 9618. When returning to the same field of view after two years, it could again observe similar transits around the same stars. Despite these observations, it was still not possible to conclude unequivocally to the presence of planets around those stars as information was incomplete.

“This is where CHEOPS comes into play: Focusing on a single-star at a time, CHEOPS is a follow-up mission which is perfect to continue observing these stars to find the missing bits of information,” complements Solène Ulmer-Moll.

A lengthy game of “hide and seek”

Suspecting the presence of exoplanets, the CHEOPS team designed a method to avoid spending blindly precious observing time in the hope to detect additional transits. They adopted a targeted approach based on the very few clues the transits observed by TESS provided. Based on this, Osborn developed a software which proposes and prioritizes candidate periods for each planet. “We then play a sort of ‘hide and seek’ game with the planets, using the CHEOPS satellite,” as Osborn says.

“We point CHEOPS towards a target at a given time, and depending if we observe a transit or not, we can eliminate some of the possibilities and try again at another time until there is a unique solution for the orbital period.” It took five and four attempts respectively for the scientists to clearly confirm the existence of the two exoplanets and determine that TOI 5678 b has a period of 48 days, while HIP 9618 c has a period of 52.5 days.

Ideal targets for the JWST

The story does not end there for the scientists. With the newly found constrained periods, they could turn to ground-based observations using another technique called radial velocity, which enabled the team to determine masses of respectively 20 and 7.5 Earth masses for TOI 5678 b and HIP 9618 c. With both the size and mass of a planet, its density is known, and scientists can get an idea of what it is made off. “For mini-Neptunes however, density is not enough, and there are still a few hypotheses as for the composition of the planets: they could either be rocky planets with a lot of gas, or planets rich in water and with a very steamy atmosphere,” explains Ulmer-Moll. “Since the four newly discovered exoplanets are orbiting bright stars, it also makes them targets of prime interest for the mission of the James Webb Space Telescope JWST which might help to solve the riddle of their composition,” Ulmer-Moll continues.

Most exoplanets atmospheres observed so far have been from Hot Jupiters, which are very big and hot exoplanets orbiting close to their parent star. “The four new planets which we detected have much more moderate temperatures of ‘only’ 217 to 277ºC. These temperatures enable clouds and molecules to survive, which would otherwise be destroyed by the intense heat of Hot Jupiters. And they may potentially be detected by the JWST,” as Osborn explains. Smaller in size and with a longer orbital period than Hot Jupiters, the four newly detected planets are a first step towards the observation of transiting Earth-like planets.

Quelle: University of Bern

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Update: 11.07.2023

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Cheops shows scorching exoplanet acts like a mirror

Data from ESA’s exoplanet mission Cheops has led to the surprising revelation that an ultra-hot exoplanet that orbits its host star in less than a day is covered by reflective clouds of metal, making it the shiniest exoplanet ever found.

Aside from the Moon, the brightest object in our night sky is planet Venus, whose thick cloud layer reflects around 75% of the Sun’s light. By comparison, Earth only reflects around 30% of incoming sunlight.

Now for the first time, astronomers have found an exoplanet that can match Venus’ shininess: planet LTT9779 b. New detailed measurements by ESA’s Cheops mission reveal that this planet reflects a whopping 80% of the light shone on it by its host star.

Cheops’ high-precision measurements were a targeted follow-up from the planet’s initial discovery and characterisation in 2020 by NASA’s TESS mission and ground-based instruments such as the ESO HARPS instrument in Chile.

The exoplanet is around the size of Neptune, making it the largest “mirror” in the Universe that we know of today. The reason for its high reflectivity is that it is covered by metallic clouds. These are mostly made of silicate – the same stuff that sand and glass are made of – mixed with metals like titanium.

“Imagine a burning world, close to its star, with heavy clouds of metals floating aloft, raining down titanium droplets,” says James Jenkins, astronomer at Diego Portales University and CATA (Santiago, Chile). James co-authored a scientific paper describing the new research, published in the journal Astronomy & Astrophysics today.

This infographic shows the host star as a big yellow circle on the left, with the shiny exoplanet orbiting as a small circle around it in white/grey. The exoplanet orbits its star in around 19 hours. In the middle of the infographic, a schematic of the interior of the exoplanet is shown, with cloud layers of silicate (glass) and titanate in grey and white. On the right, three facts about the exoplanet are shown. It has a mass 1.7 times that of Neptune and a radius 1.2 times that of Neptune. The exoplanet’s dayside temperature is around 2000 °C.]

A sky filled with clouds of metal

The fraction of light that an object reflects is called its ‘albedo’. Most planets have a low albedo, either because they have an atmosphere that absorbs a lot of light, or because their surface is dark or rough. Exceptions tend to be frozen ice-worlds, or planets like Venus which have a reflective cloud layer.

LTT9779 b’s high albedo came as a surprise because the planet’s side facing its star is estimated to be around 2000 °C. Any temperature above 100 °C is too hot for clouds of water to form, but the temperature of this planet’s atmosphere should even be too hot for clouds made of metal or glass.

“It was really a puzzle, until we realised we should think about this cloud formation in the same way as condensation forming in a bathroom after a hot shower,” notes Vivien Parmentier, researcher at the Observatory of Côte d’Azur (France) and co-author of this research. Vivien explains: “To steam up a bathroom you can either cool the air until water vapour condenses, or you can keep the hot water running until clouds form because the air is so saturated with vapour that it simply can’t hold any more. Similarly, LTT9779 b can form metallic clouds despite being so hot because the atmosphere is oversaturated with silicate and metal vapours.”

The planet that shouldn’t exist

Being shiny isn’t the only surprising thing about LTT9779 b. Its size and temperature make it a so-called ‘ultra-hot Neptune’, but no other planets of this size and mass have been found to orbit so close to their star. This means it lives in what’s known as the ‘hot Neptune desert’.

The planet has a radius 4.7 times as big as Earth’s, and a year on LTT9779 b takes just 19 hours. All previously discovered planets that orbit their star in less than a day are either ‘hot Jupiters’ – gas giants with a radius at least ten times larger than Earth’s – or rocky planets smaller than two Earth radii.

“It’s a planet that shouldn’t exist,” says Vivien. “We expect planets like this to have their atmosphere blown away by their star, leaving behind bare rock.”

First author Sergio Hoyer of the Marseille Astrophysics Laboratory comments: “'We believe these metal clouds help the planet to survive in the hot Neptune desert. The clouds reflect light and stop the planet from getting too hot and evaporating. Meanwhile, being highly metallic makes the planet and its atmosphere heavy and harder to blow away.”

The shiniest known exoplanet: LTT9779 b
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Studying an exoplanet by looking when it’s hidden

To determine LTT9779 b’s properties, ESA’s exoplanet-characterising Cheops mission looked when the planet moved behind its host star. Because the planet reflects light, the star and planet combined send more light towards the space telescope right before the planet is out of view than right after. The difference in visible light received right before and after the planet is hidden tells you how much light the planet reflects.

This project relied on Cheops’ precision and 24/7 coverage. “Precisely measuring the tiny change in signal from the star eclipsing the planet was only possible with Cheops,” says Sergio.

ESA’s Cheops project scientist Maximilian Günther adds: “Cheops is the first ever space mission dedicated to the follow-up and characterisation of already known exoplanets. Unlike large survey missions focused on discovering new exoplanet systems, Cheops has enough flexibility to swiftly focus on interesting targets and can reach a coverage and precision that we often simply cannot get any other way.”

By looking at the same exoplanet with different instruments, we get the full picture. “LTT9779 b is an ideal target for follow-up with the exceptional capabilities of both the Hubble and James Webb space telescopes,” notes ESA science operations scientist Emily Rickman. “They will allow us to explore this exoplanet with a wider wavelength range including infrared and UV light to better understand the composition of its atmosphere.”

The future of exoplanet research is bright, as Cheops is the first of a trio of dedicated exoplanet missions. It will be joined by Plato in 2026, which will focus on Earth-like planets orbiting at a possibly life-supporting distance from their star. Ariel is set to join the fleet in 2029 and will specialise in studying exoplanet atmospheres.

Quelle: ESA