̽��ֱ�� of Cambridge - Cambridge Exoplanet Research Centre

New class of habitable exoplanets 'a big step forward' in search for life

sc604 — Wed, 25 Aug 2021 23:01:00 +0000

In the search for life elsewhere, astronomers have mostly looked for planets of a similar size, mass, temperature and atmospheric composition to Earth. However, astronomers from the ̽��ֱ�� of Cambridge believe there are more promising possibilities out there.

̽��ֱ��researchers have identified a new class of habitable planets, dubbed ‘Hycean’ planets – ocean-covered planets with hydrogen-rich atmospheres – which are more numerous and observable than Earth-like planets.

̽��ֱ��researchers say the results, reported in ̽��ֱ��Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next few years is a real possibility.

“Hycean planets open a whole new avenue in our search for life elsewhere,” said Dr Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research.

Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth’s most extreme aquatic environments.

These planets also allow for a far wider habitable zone, or ‘Goldilocks zone’, compared to Earth-like planets. This means that they could still support life even though they lie outside the range where a planet similar to Earth would need to be in order to be habitable.

Thousands of planets outside our Solar System have been discovered since the first exoplanet was identified nearly 30 years ago. ̽��ֱ��vast majority are planets between the sizes of Earth and Neptune and are often referred to as ‘super-Earths’ or ‘mini-Neptunes’: they can be predominantly rocky or ice giants with hydrogen-rich atmospheres, or something in between.

Most mini-Neptunes are over 1.6 times the size of Earth: smaller than Neptune but too big to have rocky interiors like Earth. Earlier studies of such planets have found that the pressure and temperature beneath their hydrogen-rich atmospheres would be too high to support life.

However, a recent study on the mini-Neptune K2-18b by Madhusudhan’s team found that in certain conditions these planets could support life. ̽��ֱ��result led to a detailed investigation into the full range of planetary and stellar properties for which these conditions are possible, which known exoplanets may satisfy those conditions, and whether their biosignatures may be observable.

̽��ֱ��investigation led the researchers to identify a new class of planets, Hycean planets, with massive planet-wide oceans beneath hydrogen-rich atmospheres. Hycean planets can be up to 2.6 times larger than Earth and have atmospheric temperatures up to nearly 200 degrees Celsius, depending on their host stars, but their oceanic conditions could be similar to those conducive for microbial life in Earth’s oceans. Such planets also include tidally locked ‘dark’ Hycean worlds that may have habitable conditions only on their permanent night sides, and ‘cold’ Hycean worlds that receive little radiation from their stars.

Planets of this size dominate the known exoplanet population, although they have not been studied in nearly as much detail as super-Earths. Hycean worlds are likely quite common, meaning that the most promising places to look for life elsewhere in the Galaxy may have been hiding in plain sight.

However, size alone is not enough to confirm whether a planet is Hycean: other aspects such as mass, temperature and atmospheric properties are required for confirmation.

When trying to determine what the conditions are like on a planet many light years away, astronomers first need to determine whether the planet lies in the habitable zone of its star, and then look for molecular signatures to infer the planet’s atmospheric and internal structure, which govern the surface conditions, presence of oceans and potential for life.

Astronomers also look for certain biosignatures which could indicate the possibility of life. Most often, these are oxygen, ozone, methane and nitrous oxide, which are all present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulphide, that are less abundant on Earth but can be promising indicators of life on planets with hydrogen-rich atmospheres where oxygen or ozone may not be as abundant.

“Essentially, when we’ve been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start,” said Madhusudhan. “But we think Hycean planets offer a better chance of finding several trace biosignatures.”

“It's exciting that habitable conditions could exist on planets so different from Earth,” said co-author Anjali Piette, also from Cambridge.

Madhusudhan and his team found that a number of trace terrestrial biomarkers expected to be present in Hycean atmospheres would be readily detectable with spectroscopic observations in the near future. ̽��ֱ��larger sizes, higher temperatures and hydrogen-rich atmospheres of Hycean planets make their atmospheric signatures much more detectable than Earth-like planets.

̽��ֱ��Cambridge team identified a sizeable sample of potential Hycean worlds which are prime candidates for detailed study with next-generation telescopes, such as the James Webb Space Telescope (JWST), which is due to be launched later this year. These planets all orbit red dwarf stars between 35-150 light years away: close by astronomical standards. Already planned JWST observations of the most promising candidate, K2-18b, could lead to the detection of one or more biosignature molecules.

“A biosignature detection would transform our understanding of life in the universe,” said Madhusudhan. “We need to be open about where we expect to find life and what form that life could take, as nature continues to surprise us in often unimaginable ways.”

Reference:
Nikku Madhusudhan, Anjali A. A. Piette, and Savvas Constantinou. ‘Habitability and Biosignatures of Hycean Worlds.’ ̽��ֱ��Astrophysical Journal (2021). DOI: 10.3847/1538-4357/abfd9c

( ̽��ֱ��paper can also be viewed on arXiv.)

A new class of exoplanet very different to our own, but which could support life, has been identified by astronomers, which could greatly accelerate the search for life outside our Solar System.

Hycean planets open a whole new avenue in our search for life elsewhere

Nikku Madhusudhan

Amanda Smith

Artist's impression of a Hycean planet

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Hubble sees new atmosphere forming on a rocky exoplanet

sc604 — Thu, 11 Mar 2021 14:00:00 +0000

̽��ֱ��planet GJ 1132 b appears to have begun life as a gaseous world with a thick blanket of atmosphere. Starting out at several times the radius of Earth, this ‘sub-Neptune’ quickly lost its primordial hydrogen and helium atmosphere, which was stripped away by the intense radiation from its hot, young star. In a short period of time, it was reduced to a bare core about the size of Earth.

To the surprise of astronomers, new observations from Hubble have uncovered a secondary atmosphere that has replaced the planet’s first atmosphere. It is rich in hydrogen, hydrogen cyanide, methane and ammonia, and also has a hydrocarbon haze. Astronomers theorise that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. This second atmosphere, which continues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma.

“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” said team member Paul Rimmer from the ̽��ֱ�� of Cambridge. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”

“We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

In some ways, GJ 1132 b has various parallels to Earth, but in some ways, it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. ̽��ֱ��team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

However, the planets’ formation histories are profoundly different. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemisphere permanently facing Earth.

“ ̽��ֱ��question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

̽��ֱ��phenomenon of tidal heating occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also exerts a gravitational pull on the planet. ̽��ֱ��consequences are that the planet is squeezed or stretched by this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own Solar System is the Jovian moon, Io, which has continuous volcanism as a result of a tidal tug-of-war between Jupiter and the neighbouring Jovian moons.

̽��ֱ��team believes the crust of GJ 1132 b is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell by tidal flexing. Hydrogen and other gases could be released through such cracks.

“This atmosphere, if it’s thin — meaning if it has a surface pressure similar to Earth — probably means you can see right down to the ground at infrared wavelengths. That means that if astronomers use the James Webb Space Telescope to observe this planet, there’s a possibility that they will see not the spectrum of the atmosphere, but rather the spectrum of the surface,” said Swain. “And if there are magma pools or volcanism going on, those areas will be hotter. That will generate more emission, and so they’ll potentially be looking at the actual geological activity — which is exciting!”

This result is significant because it gives exoplanet scientists a way to figure out something about a planet's geology from its atmosphere,” said Rimmer, who is affiliated both with Cambridge’s Cavendish Laboratory and Department of Earth Sciences. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”

Adapted from an ESA/JPL press release.

For the first time, scientists using the NASA/ESA Hubble Space Telescope have found evidence of volcanic activity reforming the atmosphere on a rocky planet around a distant star. ̽��ֱ��planet, GJ 1132 b, has a similar density, size, and age to Earth.

It is a window onto the geology of another world

Paul Rimmer

NASA, ESA, and R. Hurt (IPAC/Caltech)

Artist’s impression of the exoplanet GJ 1132 b

Yes

Astronomers identify new method of planet formation

sc604 — Fri, 12 Feb 2021 09:44:02 +0000

In the last 25 years, scientists have discovered over 4000 planets outside our solar system. From relatively small rock and water worlds to blisteringly hot gas giants, these planets display a remarkable variety.

This variety is not unexpected. ̽��ֱ��computer models which scientists use to study the formation of planets predict this variety as well. What the models struggle to explain is the observed mass distribution of exoplanets.

̽��ֱ��majority fall in the intermediate-mass category – planets with masses of several Earth masses to around that of Neptune. Even in our own solar system, the formation of Uranus and Neptune remains a mystery.

Now, scientists from the Universities of Cambridge and Zurich, associated with the Swiss NCCR PlanetS, have proposed an alternative explanation. Their results are published in the journal Nature Astronomy.

“When planets form from the so-called protoplanetary disk of gas and dust, gravitational instabilities could be the driving mechanism,” said co-author Professor Lucio Mayer from the ̽��ֱ�� of Zurich.

In this process, dust and gas in the disk clump together due to gravity and form dense spiral structures. These then grow into planetary building blocks and eventually planets.

̽��ֱ��scale on which this process occurs is very large – spanning the scale of the protoplanetary disk. “But over shorter distances – the scale of single planets – another force dominates: That of magnetic fields developing alongside the planets,” said Mayer.

These magnetic fields stir up the gas and dust of the disk and influence the formation of the planets.

“To get a complete picture of the planetary formation process, it is important to not only simulate the large-scale spiral structure in the disk: the small-scale magnetic fields around the growing planetary building blocks also have to be included,” said lead author Dr Hongping Deng from Cambridge’s Department of Applied Mathematics and Theoretical Physics.

However, the differences in scale and nature of gravity and magnetism make the two forces challenging to integrate into the same planetary formation model. So far, computer simulations that capture the effects of one of the forces well usually do poorly with the other.

To succeed, the team developed a new modelling technique. First, they needed a deep theoretical understanding of both gravity and magnetism. Then, they had to find a way to translate the understanding into a code that could efficiently compute these contrasting forces in unison. Finally, due to the immense number of necessary calculations, a powerful computer was required – like the Piz Daint at the Swiss National Supercomputing Centre (CSCS). “Apart from the theoretical insights and the technical tools that we developed, we were therefore also dependent on the advancement of computing power,” said Mayer.

“With our model, we were able to show for the first time that the magnetic fields make it difficult for the growing planets to continue accumulating mass beyond a certain point,” said Deng. “As a result, giant planets become rarer and intermediate-mass planets much more frequent – similar to what we observe in reality.”

“These results are only a first step, but they clearly show the importance of accounting for more physical processes in planet formation simulations,” said co-author Ravit Helled from the ̽��ֱ�� of Zurich. “Our study helps to understand potential pathways to the formation of intermediate-mass planets that are very common in our galaxy. It also helps us understand the protoplanetary disks in general.”

Reference:
Hongping Deng, Lucio Mayer and Ravit Helled. ‘Formation of intermediate-mass planets via magnetically controlled disk fragmentation.’ Nature Astronomy (2021). DOI: 10.1038/s41550-020-01297-6

Adapted from a ̽��ֱ�� of Zurich press release.

Scientists have suggested a new explanation for the abundance in intermediate-mass exoplanets – a long-standing puzzle in astronomy.

Jean Favre/CSCS

Artist's impression of the protoplanetary disk with magnetic field lines

Yes

Astronomers discover the first ‘ultrahot Neptune’: one of nature’s improbable planets

Anonymous — Mon, 21 Sep 2020 13:25:16 +0000

̽��ֱ��planet orbits so close to its star that its year lasts only 19 hours, and stellar radiation heats the planet to over 1700 degrees Celsius.

At these temperatures, heavy elements like iron can be ionised in the atmosphere and molecules disassociated, providing a unique laboratory to study the chemistry of planets outside the solar system.

Although the planet weighs twice as much as Neptune, it is also slightly larger and has a similar density. Therefore, LTT 9779b should have a huge core of around 28 Earth masses, and an atmosphere that makes up around 9% of the total planetary mass.

̽��ֱ��system itself is around two billion years old, and given the intense irradiation, a Neptune-like planet would not be expected to keep its atmosphere for so long, providing a puzzle for astronomers to solve; how such an improbable system came to be. ̽��ֱ��results are reported in the journal Nature Astronomy.

LTT 9779 is a Sun-like star located at a distance of 260 light years, a stone’s throw in astronomical terms. It is metal-rich, having twice the amount of iron in its atmosphere than the Sun. This could be a key indicator that the planet was originally a much larger gas giant, since these bodies tend to form close to stars with the highest iron abundances.

Initial indications of the existence of the planet were made using the Transiting Exoplanet Survey Satellite (TESS), as part of its mission to discover small transiting planets orbiting nearby and bright stars across the whole sky. Such transits are found when a planet passes directly in front of its parent star, blocking some of the starlight, and the amount of light blocked reveals the companion’s size. Planets like these, once fully confirmed, can allow astronomers to investigate their atmospheres, providing a deeper understanding of planet formation and evolution processes.

̽��ֱ��transit signal was confirmed in early November 2018 as originating from a planetary mass body, using observations taken at the ESO la Silla Observatory in northern Chile. HARPS uses the Doppler Wobble method to measure planet masses and orbital characteristics. When objects are found to transit, Doppler measurements can be organized to confirm the planetary nature in an efficient manner. In the case of LTT 9779b, the team were able to confirm the planet’s existence after only one week of observations.

Professor James Jenkins from the Department of Astronomy at the Universidad de Chile, who led the team, said: “ ̽��ֱ��discovery of LTT 9779b so early in the TESS mission was a complete surprise; a gamble that paid off. ̽��ֱ��majority of transit events with periods less than one day turnout to be false-positives, normally background eclipsing binary stars.”

̽��ֱ��planet was uncovered in only the second of 26 sectors of observations that TESS would be observing across the whole sky. Since no similar types of planets were detected in the TESS precursor missions Kepler and K2, the finding was even more exciting.

“We selected this candidate from a TESS alert due to its very short orbital period. After inspecting the light curve, we found it was a good candidate for an upcoming week-long observation campaign using the HARPS spectrograph in La Silla,” said co-author Matías Díaz, also from the Universidad de Chile. “We planned the observations carefully, to maximize the use of the spectrograph and sample the orbit of the candidate in an optimal way. During the first nights of data we saw the observations matched the predicted period of the candidate. Further analysis of the seven nights of observations in November were consistent with a massive Neptune planet.”

LTT 9779b exists in the ‘Neptunian Desert’, a region devoid of planets when we look at the population of planetary masses and sizes. Although icy giants seem to be a fairly common by-product of the planet formation process, this is not the case very close to their stars. ̽��ֱ��researchers believe these planets get stripped of their atmospheres over cosmic time, ending up as so-called Ultra Short Period planets.

̽��ֱ��Kepler mission found that Ultra Short Period planets, those that orbit their stars in one day or less, come mainly in the form of large gas giants or small rocky planets. Models tell us that planets like LTT 9779b should be stripped of their atmospheres through a process called photoevaporation as they move close to their stars. ̽��ֱ��large gas giants, on the other hand, have strong gravitational fields that can hold onto their atmospheres, and so we end up with a dearth of planets like Neptune with the shortest orbital periods.

“Planetary structure models tell us that the planet is a giant core dominated world, but crucially, there should exist two to three Earth-masses of atmospheric gas,” said Jenkins. “But if the star is so old, why does any atmosphere exist at all? Well, if LTT 9779b started life as a gas giant, then a process called Roche Lobe Overflow could have transferred significant amounts of the atmospheric gas onto the star.”

Roche Lobe Overflow is a process whereby a planet comes so close to its star that the star’s stronger gravity can capture the outer layers of the planet, causing it to transfer onto the star and so significantly decreasing the mass of the planet. Models predict outcomes similar to that of the LTT 9779 system, but they also require some fine-tuning.

“It could also be that LTT 9779b arrived at its current orbit quite late in the day, and so hasn’t had time to be stripped of the atmosphere. Collisions with other planets in the system could have thrown it inwards towards the star. Indeed, since it is such a unique and rare world, more exotic scenarios may be plausible,” said Jenkins.

Members of the Cambridge Astronomy department are part of the Next-Generation Transit Survey (NGTS). ̽��ֱ��NGTS team conducted follow-up observations of LT9779b’s transit to help confirm the planetary nature of the system and better constrain its properties.

“LTT 9779b is an intriguing planet, being the first of its kind discovered,” said co-author Dr Ed Gillen, from Cambridge’s Cavendish Laboratory. “It is particularly exciting because of its peculiarity: how did this planet come to arrive on such a short period orbit and why does it still possess an atmosphere? Fortunately, the planetary system is located nearby so we can study it in detail, which promises new insights into how such planets come to be and what they are made of.”

Reference:
James S. Jenkins et al. ‘An ultrahot Neptune in the Neptune desert.’ Nature Astronomy (2020). DOI: 10.1038/s41550-020-1142-z

Adapted from a Universidad de Chile press release.

An international team of astronomers, including researchers from the ̽��ֱ�� of Cambridge, has discovered a new class of planet, an ‘ultrahot Neptune’, orbiting the nearby star LTT 9779.

This planet is particularly exciting because of its peculiarity: how did this planet come to arrive on such a short period orbit and why does it still possess an atmosphere?

Ed Gillen

icardo Ramirez, Universidad de Chile

Artist's impression of LTT 9779b

Yes

‘Lost’ world’s rediscovery is step towards finding habitable planets

sc604 — Tue, 21 Jul 2020 07:39:47 +0000

̽��ֱ��planet, the size and mass of Saturn with an orbit of thirty-five days, is among hundreds of ‘lost’ worlds that astronomers, including from the ̽��ֱ�� of Cambridge, are using new techniques to track down and characterise, in the hope of finding cooler planets like those in our solar system, and even potentially habitable planets.

Reported in Astrophysical Journal Letters, the planet named NGTS-11b orbits a star 620 light-years away and is located five times closer to its sun than Earth is to our own.

̽��ֱ��planet was originally found in a search for planets in 2018 by the ̽��ֱ�� of Warwick-led team using data from NASA’s TESS telescope. This uses the transit method to spot planets, scanning for the tell-tale dip in light from the star that indicates that an object has passed between the telescope and the star.

However, TESS only scans most sections of the sky for 27 days. This means many of the longer period planets only transit once in the TESS data: without a second observation the planet is effectively lost. Researchers from Cambridge’s Cavendish Laboratory are part of the Next-Generation Transit Survey (NGTS) team which, after identifying a single transit event in the TESS data of the star NGTS-11, monitored the system in search of additional transits to confirm the planetary nature of the transiting object.

“By chasing that second transit down we’ve found a longer period planet. It’s the first of hopefully many such finds pushing to longer periods,” said lead author Dr Samuel Gill from the ̽��ֱ�� of Warwick. “These discoveries are rare but important, since they allow us to find longer period planets than other astronomers are finding. Longer period planets are cooler, more like the planets in our own solar system.”

NGTS-11b has a temperature of only 160°C – cooler than Mercury or Venus. Although this is still too hot to support life as we know it, it is closer to the Goldilocks zone than many previously discovered planets which typically have temperatures above 1000°C. ̽��ֱ��Goldilocks zone refers to a range of orbits that would allow a planet or moon to support liquid water: too close to its star and it will be too hot, but too far away and it will be too cold.

“While we have discovered many planets that orbit close to their host star, we know of fewer at longer periods and cooler temperatures, which makes NGTS-11b an interesting find that takes us one step closer to finding planets in the Goldilocks zone,” said co-author Dr Ed Gillen from Cambridge’s Cavendish Laboratory. “Longer period planets like NGTS-11b may help us to better understand the various evolutionary processes that planetary systems undergo both during and after their formation.”

NGTS has twelve state-of-the-art telescopes at its site in Chile, which means that researchers can monitor multiple stars for months on end, searching for lost planets. ̽��ֱ��dip in light from NGTS-11b is only 1% deep and occurs only once every 35 days, putting it out of reach of other telescopes.

There are hundreds of single transits detected by TESS that researchers will be monitoring using this method. This will allow them to discover cooler exoplanets of all sizes, including planets more like those in our own solar system. Some of these will be small rocky planets in the Goldilocks zone that are cool enough to host liquid water oceans and potentially extra-terrestrial life.

̽��ֱ��research was supported by the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Samuel Gill et al. ‘NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event.’ ̽��ֱ��Astrophysical Journal Letters (2020). DOI: 10.3847/2041-8213/ab9eb9

Adapted from a ̽��ֱ�� of Warwick press release.

̽��ֱ��rediscovery of a lost planet could pave the way for the detection of a world within the habitable ‘Goldilocks zone’ in a distant solar system.

NGTS-11b is an interesting find that takes us one step closer to finding planets in the Goldilocks zone

Ed Gillen

Y. Beletsky (LCO)/ESO

Paranal nights

Yes

Water common – yet scarce – in exoplanets

sc604 — Wed, 11 Dec 2019 10:22:21 +0000

A team of researchers, led by the ̽��ֱ�� of Cambridge, used atmospheric data from 19 exoplanets to obtain detailed measurements of their chemical and thermal properties. ̽��ֱ��exoplanets in the study span a large range in size – from ‘mini-Neptunes’ of nearly 10 Earth masses to ‘super-Jupiters’ of over 600 Earth masses – and temperature, from nearly 20°C to over 2000°C. Like the giant planets in our solar system, their atmospheres are rich in hydrogen, but they orbit different types of stars.

̽��ֱ��researchers found that while water vapour is common in the atmospheres of many exoplanets, the amounts were surprisingly lower than expected, while the amounts of other elements found in some planets were consistent with expectations. ̽��ֱ��results, which are part of a five-year research programme on the chemical compositions of planetary atmospheres outside our solar system, are reported in ̽��ֱ��Astrophysical Journal Letters.

“We are seeing the first signs of chemical patterns in extra-terrestrial worlds, and we’re seeing just how diverse they can be in terms of their chemical compositions,” said project leader Dr Nikku Madhusudhan from the Institute of Astronomy at Cambridge, who first measured low water vapour abundances in giant exoplanets five years ago.

In our solar system, the amount of carbon relative to hydrogen in the atmospheres of giant planets is significantly higher than that of the sun. This ‘super-solar’ abundance is thought to have originated when the planets were being formed, and large amounts of ice, rocks and other particles were brought into the planet in a process called accretion.

̽��ֱ��abundances of other elements have been predicted to be similarly high in the atmospheres of giant exoplanets - especially oxygen, which is the most abundant element in the universe after hydrogen and helium. This means that water, a dominant carrier of oxygen, is also expected to be overabundant in such atmospheres.

̽��ֱ��researchers used extensive spectroscopic data from space-based and ground-based telescopes, including the Hubble Space Telescope, the Spitzer Space Telescope, the Very Large Telescope in Chile and the Gran Telescopio Canarias in Spain. ̽��ֱ��range of available observations, along with detailed computational models, statistical methods, and atomic properties of sodium and potassium, allowed the researchers to obtain estimates of the chemical abundances in the exoplanet atmospheres across the sample.

̽��ֱ��team reported the abundance of water vapour in 14 of the 19 planets, and the abundance of sodium and potassium in six planets each. Their results suggest a depletion of oxygen relative to other elements and provide chemical clues into how these exoplanets may have formed without substantial accretion of ice.

“It is incredible to see such low water abundances in the atmospheres of a broad range of planets orbiting a variety of stars,” said Madhusudhan.

“Measuring the abundances of these chemicals in exoplanetary atmospheres is something extraordinary, considering that we have not been able to do the same for giant planets in our solar system yet, including Jupiter, our nearest gas giant neighbour,” said Luis Welbanks, lead author of the study and PhD student at the Institute of Astronomy.

Various efforts to measure water in Jupiter’s atmosphere, including NASA’s current Juno mission, have proved challenging. “Since Jupiter is so cold, any water vapour in its atmosphere would be condensed, making it difficult to measure,” said Welbanks. “If the water abundance in Jupiter were found to be plentiful as predicted, it would imply that it formed in a different way to the exoplanets we looked at in the current study.”

“We look forward to increasing the size of our planet sample in future studies,” said Madhusudhan. “Inevitably, we expect to find outliers to the current trends as well as measurements of other chemicals.”

These results show that different chemical elements can no longer be assumed to be equally abundant in planetary atmospheres, challenging assumptions in several theoretical models.

“Given that water is a key ingredient to our notion of habitability on Earth, it is important to know how much water can be found in planetary systems beyond our own,” said Madhusudhan.

Reference:
L. Welbanks, N. Madhusudhan, N. Allard, et al. ‘Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of H₂O, Na, and K.’ ̽��ֱ��Astrophysical Journal Letters (2019). DOI: 10.3847/2041-8213/ab5a89

̽��ֱ��most extensive survey of atmospheric chemical compositions of exoplanets to date has revealed trends that challenge current theories of planet formation and has implications for the search for water in the solar system and beyond.

We’re seeing just how diverse extra-terrestrial worlds can be in terms of their chemical compositions

Nikku Madhusudhan

Amanda Smith

Artist's impression of gas giant exoplanet

Yes

Professor Didier Queloz wins 2019 Nobel Prize in Physics for first discovery of an exoplanet

Anonymous — Tue, 08 Oct 2019 10:15:33 +0000

Professor Didier Queloz from the ̽��ֱ�� of Cambridge has been jointly awarded the 2019 Nobel Prize in Physics along with Professor James Peebles and Professor Michel Mayor for their pioneering advances in physical cosmology, and the discovery of an exoplanet orbiting a solar-type star.

Queloz is Professor of Physics at the ̽��ֱ��’s Cavendish Laboratory, and Fellow of Trinity College, Cambridge. He leads the Cambridge Exoplanet Research Centre. In 1995, along with Michel Mayor, Queloz made the first discovery of a planet outside our solar system, an exoplanet, orbiting the star 51 Pegasi. Queloz becomes the 109th affiliate of the ̽��ֱ�� of Cambridge to be awarded a Nobel Prize.

̽��ֱ��Royal Swedish Academy of Sciences announced the 2019 Prize this morning. ̽��ֱ��Nobel Assembly said: “ ̽��ֱ��discovery by 2019 Nobel Prize laureates Michel Mayor and Didier Queloz started a revolution in astronomy and over 4,000 exoplanets have since been found in the Milky Way. Strange new worlds are still being discovered, with an incredible wealth of sizes, forms and orbits.”

"This year’s Laureates have transformed our ideas about the cosmos. While James Peebles’ theoretical discoveries contributed to our understanding of how the universe evolved after the Big Bang, Michel Mayor and Didier Queloz explored our cosmic neighbourhoods on the hunt for unknown planets. Their discoveries have forever changed our conceptions of the world."

Above: Listen to audio from the press conference given by Prof Queloz on the day the Nobel Prize was awarded.

"It’s an incredible honour and I’m still trying to digest it," said Queloz on the day he was awarded the Nobel. "When we discovered the first exoplanet, it was pretty obvious that this was something important, even though not everyone believed us at the time. Back then, exoplanet research was a very small field. I think there were about fifty of us and we were seen as weirdos. Now there are probably over a thousand people working in the field.

"It’s a hot topic at the moment, so I’m really happy that the field of exoplanets has been recognised with a Nobel Prize," Queloz said. "When you are working so passionately at your research, it can be very disruptive to your family. My family has always been there for me and I’m grateful of their support. This Nobel Prize is also an acknowledgement of their incredible patience!"

Today, many regard the discovery of 51 Pegasi b by Queloz and Mayor at the ̽��ֱ�� of Geneva in 1995, as a moment in astronomy that forever changed the way we understand the universe and our place within it.

It was the first confirmation of an exoplanet – a planet that orbits a star other than our Sun. Until then, although astronomers had speculated as to the existence of these distant worlds, no planet other than those in our own solar system had ever been found.

This seminal discovery has spawned a revolution in astronomy both in terms of new instrumentation and understanding of planet formation and evolution. Since then Professor Queloz has been involved in a successful series of developments of precise spectrographs, considerable improving the precision of the Doppler technique.

Of the 1,900 or so confirmed exoplanets that have now been found – around a tenth of these by Queloz himself – many are different to anything we ever imagined, challenging existing theories of planet formation.

In 2007, in the emerging area of planetary transit detection, he established a successful international collaboration with the WASP team from UK, providing the spectroscopic confirmation and precise photometry follow-up to confirm and characterize planetary candidates. He also took an active part in the Corot mission, pioneering planet transit detection from space. He conducted a part of the work that led to the first transit detection of a rocky planet (Corot-7b).

In 2012 he received with Michel Mayor the 2011 BBVA Foundation Frontiers of Knowledge Award of Basic Sciences for developing new astronomical instruments and experimental techniques that led to the first observation of planets outside the Solar System.

In 2013 he became a professor at the ̽��ֱ�� of Cambridge, where he is leading a comprehensive research program with the goal of progressing our understanding of the formation, structure, and habitability of exoplanets, as well as to promote and share the excitement of this work with the public.

̽��ֱ�� ̽��ֱ��'s Vice-Chancellor, Professor Stephen Toope, said: "I am delighted to hear that Professor Didier Queloz has been awarded this year’s Nobel Prize in Physics. Didier’s discovery of planets beyond our solar system has ushered in a revolutionary new era for cosmology.

"This work represents an extraordinary scientific achievement but also offers humanity so much inspiration – the chance to imagine such distant and different, or perhaps similar, worlds. It gives me tremendous pleasure, on behalf of our community, to congratulate the ̽��ֱ�� of Cambridge’s latest Nobel Prize winner.”

Professor Andy Parker, Head of the Cavendish Laboratory, said: "Professor Queloz’s research has led to the discovery that planets are abundant throughout our galaxy, orbiting other stars. We can now estimate that there are tens of billions of potentially inhabitable exoplanets. This takes us one step closer to answering the question of whether we are alone in the Universe: it seems increasingly likely that life in some form will have found a foothold on these many new worlds.

" ̽��ֱ��current programme of work being carried out by Professor Queloz at the Cavendish Laboratory at Cambridge ̽��ֱ�� will search for signatures of life in the chemicals found in the exoplanet atmospheres. This groundbreaking research is extremely demanding technically, and addresses profound questions which fascinate all of humanity. We look forward to further breakthroughs as Professor Queloz continues his outstanding work."

Read a 2016 interview with Professor Queloz here.

My PI here in Cambridge, @DidierQueloz, just won the Physics Nobel Prize! We had to interrupt our SPECULOOS meeting to take an historical picture! Congrats Didier!!! pic.twitter.com/eGnsNAogcf
— Laetitia Delrez (@LaetitiaDelrez) October 8, 2019

New Nobel Laureate Didier Queloz was at a scientific meeting when news of his #NobelPrize broke. Here, fresh from celebrating with colleagues, he speaks with @nobelprize.

Interview to follow.

Photo: Nick Saffell. pic.twitter.com/7FyURzjzAq
— ̽��ֱ��Nobel Prize (@NobelPrize) October 8, 2019

A perspective from Lord Martin Rees, Astronomer Royal and Emeritus Professor of Cosmology and Astrophysics at the ̽��ֱ�� of Cambridge:

"Jim Peebles played a key role back in 1965 in appreciating and interpreting the ‘cosmic microwave background’ radiation – the ‘afterglow of creation’. He has been the most influential and respected leader of empirical cosmology with a sustained record of achievement spanning half a century.

" ̽��ֱ��study of exoplanets is perhaps the most vibrant field of astronomy. We now know that most stars are orbited by retinues of planets; there may be a billion planets in our galaxy resembling the Earth (similar in size and at a distance from their parent star where liquid water can exist). This takes us a step towards the fascinating question of detecting evidence for life on the nearest of these exoplanets. Queloz and Mayor not only discovered the first planet orbiting an ordinary star. ̽��ֱ��have also been among the leaders in the ongoing research that has led to the discovery of many thousands of other planetary systems, exhibiting an unexpected variety.

"These awards seem to show, incidentally, a welcome broadening of the Nobel criteria. In the past, astronomy has been included primarily when the discovery involves some new physics (neutron stars, gravitational waves, vacuum energy, etc). But this award highlights astronomy as also the grandest of the environmental sciences. And the award to Peebles will be welcomed by his friends and colleagues as recognition of a lifetime of sustained contributions and insights by an acknowledged intellectual leader, rather than a ‘one off’ achievement."

Queloz jointly wins the 2019 Physics Nobel for his work on the first confirmation of an exoplanet – a planet that orbits a star other than our Sun.

Back then, exoplanet research was a very small field. I think there were about fifty of us and we were seen as weirdos

Didier Queloz on the early days of his research

Exoplanet Hunter: In search of new Earths and life in the Universe

Professor Queloz in his office at the Cavendish Laboratory, Cambridge.

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Scientists identify exoplanets where life could develop as it did on Earth

sc604 — Wed, 01 Aug 2018 18:00:00 +0000

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge and the Medical Research Council Laboratory of Molecular Biology (MRC LMB), found that the chances for life to develop on the surface of a rocky planet like Earth are connected to the type and strength of light given off by its host star.

Their study, published in the journal Science Advances, proposes that stars which give off sufficient ultraviolet (UV) light could kick-start life on their orbiting planets in the same way it likely developed on Earth, where the UV light powers a series of chemical reactions that produce the building blocks of life.

̽��ֱ��researchers have identified a range of planets where the UV light from their host star is sufficient to allow these chemical reactions to take place, and that lie within the habitable range where liquid water can exist on the planet’s surface.

“This work allows us to narrow down the best places to search for life,” said Dr Paul Rimmer, a postdoctoral researcher with a joint affiliation at Cambridge’s Cavendish Laboratory and the MRC LMB, and the paper’s first author. “It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”

̽��ֱ��new paper is the result of an ongoing collaboration between the Cavendish Laboratory and the MRC LMB, bringing together organic chemistry and exoplanet research. It builds on the work of Professor John Sutherland, a co-author on the current paper, who studies the chemical origin of life on Earth.

In a paper published in 2015, Professor Sutherland’s group at the MRC LMB proposed that cyanide, although a deadly poison, was in fact a key ingredient in the primordial soup from which all life on Earth originated.

In this hypothesis, carbon from meteorites that slammed into the young Earth interacted with nitrogen in the atmosphere to form hydrogen cyanide. ̽��ֱ��hydrogen cyanide rained to the surface, where it interacted with other elements in various ways, powered by the UV light from the sun. ̽��ֱ��chemicals produced from these interactions generated the building blocks of RNA, the close relative of DNA which most biologists believe was the first molecule of life to carry information.

In the laboratory, Sutherland’s group recreated these chemical reactions under UV lamps, and generated the precursors to lipids, amino acids and nucleotides, all of which are essential components of living cells.

“I came across these earlier experiments, and as an astronomer, my first question is always what kind of light are you using, which as chemists they hadn’t really thought about,” said Rimmer. “I started out measuring the number of photons emitted by their lamps, and then realised that comparing this light to the light of different stars was a straightforward next step.”

̽��ֱ��two groups performed a series of laboratory experiments to measure how quickly the building blocks of life can be formed from hydrogen cyanide and hydrogen sulphite ions in water when exposed to UV light. They then performed the same experiment in the absence of light.

“There is chemistry that happens in the dark: it’s slower than the chemistry that happens in the light, but it’s there,” said senior author Professor Didier Queloz, also from the Cavendish Laboratory. “We wanted to see how much light it would take for the light chemistry to win out over the dark chemistry.”

̽��ֱ��same experiment run in the dark with the hydrogen cyanide and the hydrogen sulphite resulted in an inert compound which could not be used to form the building blocks of life, while the experiment performed under the lights did result in the necessary building blocks.

̽��ֱ��researchers then compared the light chemistry to the dark chemistry against the UV light of different stars. They plotted the amount of UV light available to planets in orbit around these stars to determine where the chemistry could be activated.

They found that stars around the same temperature as our sun emitted enough light for the building blocks of life to have formed on the surfaces of their planets. Cool stars, on the other hand, do not produce enough light for these building blocks to be formed, except if they have frequent powerful solar flares to jolt the chemistry forward step by step. Planets that both receive enough light to activate the chemistry and could have liquid water on their surfaces reside in what the researchers have called the abiogenesis zone.

Among the known exoplanets which reside in the abiogenesis zone are several planets detected by the Kepler telescope, including Kepler 452b, a planet that has been nicknamed Earth’s ‘cousin’, although it is too far away to probe with current technology. Next-generation telescopes, such as NASA’s TESS and James Webb Telescopes, will hopefully be able to identify and potentially characterise many more planets that lie within the abiogenesis zone.

Of course, it is also possible that if there is life on other planets, that it has or will develop in a totally different way than it did on Earth.

“I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us,” said Rimmer. “There’s an important distinction between what is necessary and what is sufficient. ̽��ֱ��building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. “Getting some idea of what fraction have been, or might be, primed for life fascinates me,” said Sutherland. “Of course, being primed for life is not everything and we still don’t know how likely the origin of life is, even given favourable circumstances - if it’s really unlikely then we might be alone, but if not, we may have company.”

̽��ֱ��research was funded by the Kavli Foundation and the Simons Foundation.

Reference:
Paul B. Rimmer et al. ‘ ̽��ֱ��Origin of RNA Precursors on Exoplanets.’ Science Advances (2018). DOI: 10.1126/sciadv.aar3302

Inset image: Diagram of confirmed exoplanets within the liquid water habitable zone (as well as Earth). Credit: Paul Rimmer

Scientists have identified a group of planets outside our solar system where the same chemical conditions that may have led to life on Earth exist.

This work brings us just a little bit closer to addressing the question of whether we are alone in the universe.

Paul Rimmer

NASA Ames/JPL-Caltech/T. Pyle

Artist's concept depicting one possible appearance of the planet Kepler-452b

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