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Webb narrows atmospheric possibilities for Earth-sized exoplanet TRAPPIST-1 d

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The James Webb Space Telescope narrows atmospheric possibilities for Earth-sized rocky exoplanet TRAPPIST-1 d. Illustration of a planet silhouetted in front of a star. The star shows a large eruption on one side and more wisps of red coming from its southern hemisphere. Two more planets appear in the background.

Webb narrows atmospheric possibilities for Earth-sized exoplanet TRAPPIST-1 d

The exoplanet TRAPPIST-1 d intrigues astronomers looking for possibly habitable worlds beyond our solar system because it is similar in size to Earth, rocky, and resides in an area around its star where liquid water on its surface is theoretically possible. But according to a new study using data from the NASA/ESA/CSA James Webb Space Telescope, it does not have an Earth-like atmosphere.

A protective atmosphere, a friendly Sun, and lots of liquid water — Earth is a special place. Using the unprecedented capabilities of the Webb, astronomers are on a mission to determine just how special, and rare, our home planet is. Can this temperate environment exist elsewhere, even around a different type of star? The TRAPPIST-1 system provides a tantalizing opportunity to explore this question, as it contains seven Earth-sized worlds orbiting the most common type of star in the galaxy: a red dwarf.

“Ultimately, we want to know if something like the environment we enjoy on Earth can exist elsewhere, and under what conditions. While the James Webb Space Telescope is giving us the ability to explore this question in Earth-sized planets for the first time, at this point we can rule out TRAPPIST-1 d from a list of potential Earth twins or cousins,”

said Caroline Piaulet-Ghorayeb of the University of Chicago and Trottier Institute for Research on Exoplanets (IREx) at Université de Montréal, lead author of the study published in The Astrophysical Journal.

Planet TRAPPIST-1 d

The TRAPPIST-1 system is located 40 light-years away and was revealed as the record-holder for most Earth-sized rocky planets around a single star in 2017, thanks to data from NASA’s retired Spitzer Space Telescope and other observatories. Due to that star being a dim, relatively cold red dwarf, the “habitable zone” – where the planet’s temperature may be just right, such that liquid surface water is possible – lies much closer to the star than in our solar system. TRAPPIST-1 d, the third planet from the red dwarf star, lies on the cusp of that temperate zone, yet its distance to its star is only 2 percent of Earth’s distance from the Sun. TRAPPIST-1 d completes an entire orbit around its star, its year, in only four Earth days.

Webb’s NIRSpec (Near-Infrared Spectrograph) instrument did not detect molecules from TRAPPIST-1 d that are common in Earth’s atmosphere, like water, methane, or carbon dioxide. However, Piaulet-Ghorayeb outlined several possibilities for the exoplanet that remain open for follow-up study.

“There are a few potential reasons why we don’t detect an atmosphere around TRAPPIST-1 d. It could have an extremely thin atmosphere that is difficult to detect, somewhat like Mars. Alternatively, it could have very thick, high-altitude clouds that are blocking our detection of specific atmospheric signatures — something more like Venus. Or, it could be a barren rock, with no atmosphere at all,” Piaulet-Ghorayeb said.

The star TRAPPIST-1

No matter what the case may be for TRAPPIST-1 d, it’s tough being a planet in orbit around a red dwarf star. TRAPPIST-1, the host star of the system, is known to be volatile, often releasing flares of high-energy radiation with the potential to strip off the atmospheres of its small planets, especially those orbiting most closely. Nevertheless, scientists are motivated to seek signs of atmospheres on the TRAPPIST-1 planets because red dwarf stars are the most common stars in our galaxy. If planets can hold on to an atmosphere here, under waves of harsh stellar radiation, they could, as the saying goes, make it anywhere.

“Webb’s sensitive infrared instruments are allowing us to delve into the atmospheres of these smaller, colder planets for the first time,” said Björn Benneke of IREx at Université de Montréal, a co-author of the study. “We’re really just getting started using Webb to look for atmospheres on Earth-sized planets, and to define the line between planets that can hold onto an atmosphere, and those that cannot.”

The outer TRAPPIST-1 planets

Webb observations of the outer TRAPPIST-1 planets are ongoing, which hold both potential and peril. On the one hand, Benneke said, planets e, f, g, and h may have better chances of having atmospheres because they are further away from the energetic eruptions of their host star. However, their distance and colder environment will make atmospheric signatures more difficult to detect, even with Webb’s infrared instruments.

“All hope is not lost for atmospheres around the TRAPPIST-1 planets,” Piaulet-Ghorayeb said. “While we didn’t find a big, bold atmospheric signature at planet d, there is still potential for the outer planets to be holding onto a lot of water and other atmospheric components.”

“Our detective work is just beginning. While TRAPPIST-1 d may prove a barren rock illuminated by a cruel red star, the outer planets TRAPPIST-1e, f, g, and h, may yet possess thick atmospheres,” added Ryan MacDonald, a co-author of the paper, now at the University of St Andrews in the United Kingdom, and previously at the University of Michigan. “Thanks to Webb we now know that TRAPPIST-1 d is a far cry from a hospitable world. We’re learning that the Earth is even more special in the cosmos.”

Illustration of a planet silhouetted in front of a star. The star shows a large eruption on one side and more wisps of red coming from its southern hemisphere. Two more planets appear in the background.
The James Webb Space Telescope narrows atmospheric possibilities for Earth-sized rocky exoplanet TRAPPIST-1 d. This artist’s concept depicts planet TRAPPIST-1 d passing in front of its turbulent star, with other members of the closely packed system shown in the background.
The TRAPPIST-1 system is intriguing to scientists for a few reasons. Not only does the system have seven Earth-sized rocky worlds, but its star is a red dwarf, the most common type of star in the Milky Way galaxy. If an Earth-sized world can maintain an atmosphere here, and thus have the potential for liquid surface water, the chance of finding similar worlds throughout the galaxy is much higher. In studying the TRAPPIST-1 planets, scientists are determining the best methods for separating starlight from potential atmospheric signatures in data from the NASA/ESA/CSA James Webb Space Telescope. The star TRAPPIST-1’s variability, with frequent flares, provides a challenging testing ground for these methods.
Credit: NASA, ESA, CSA, J. Olmsted (STScI)

Bibliographic information:

Caroline Piaulet-Ghorayeb et al.,  ApJ 989 181 2025, DOI: 10.3847/1538-4357/adf207

 

Press release from ESA Webb.

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Astronomy

Galaxy GS-NDG-9422 (9422): Webb finds potential missing link to first stars

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Galaxy GS-NDG-9422; 9422 A black background sprinkled with small, colourful galaxies in orange, blue, and white. On the left, a third of the way down from the top of the image, a very faint dot of a galaxy is outlined with a white square and pulled out in a graphic to be shown magnified. In the pullout square to the right, the galaxy is a hazy white dot edged in orange, with faint blue projections opposite each other at the 11 o’clock and 5 o’clock positions.

Galaxy GS-NDG-9422 (9422): Webb finds potential missing link to first stars

Looking deep into the early universe with the NASA/ESA/CSA James Webb Space Telescope, astronomers have found something unprecedented: a galaxy with an odd light signature, which they attribute to its gas outshining its stars.

A black background sprinkled with small, colourful galaxies in orange, blue, and white. On the left, a third of the way down from the top of the image, a very faint dot of a galaxy is outlined with a white square and pulled out in a graphic to be shown magnified. In the pullout square to the right, the galaxy is a hazy white dot edged in orange, with faint blue projections opposite each other at the 11 o’clock and 5 o’clock positions.
The galaxy GS-NDG-9422 may easily have gone unnoticed. However, what appears as a faint blur in this James Webb Space Telescope image may actually be a groundbreaking discovery that points astronomers on a new path of understanding galaxy evolution in the early universe.
Detailed information on the galaxy’s chemical makeup, captured by Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, indicates that the light we see in this image is coming from the galaxy’s hot gas, rather than its stars. That is the best explanation astronomers have discovered so far to explain the unexpected features in the light spectrum. They think that the galaxy’s stars are so extremely hot and massive that they are heating up the nebular gas in the galaxy to more than 80,000 degrees Celsius, allowing it to shine even brighter in near-infrared light than the stars themselves.
The authors of a new study on Webb’s observations of the galaxy think GS-NDG-9422 may represent a never-before-seen phase of galaxy evolution in the early universe, within the first billion years after the big bang. Their task now is to see if they can find more galaxies displaying the same features.
Credit: NASA, ESA, CSA, STScI, A. Cameron (University of Oxford)

Found approximately one billion years after the big bang, galaxy GS-NDG-9422 (9422) may be a missing-link phase of galactic evolution between the universe’s first stars and familiar, well-established galaxies.

“My first thought in looking at the galaxy’s spectrum was, ‘that’s weird,’ which is exactly what the Webb telescope was designed to reveal: totally new phenomena in the early universe that will help us understand how the cosmic story began,” said lead researcher Alex Cameron of the University of Oxford in the United Kingdom.

Cameron reached out to colleague Harley Katz, a theorist, to discuss the strange data. Working together, their team found that computer models of cosmic gas clouds heated by very hot, massive stars, to an extent that the gas shone brighter than the stars, was nearly a perfect match to Webb’s observations.

“It looks like these stars must be much hotter and more massive than what we see in the local universe, which makes sense because the early universe was a very different environment,” said Katz, of Oxford and the University of Chicago, U.S.A.

In the local universe, typical hot, massive stars have a temperature ranging between 40,000 to 50,000 degrees Celsius. According to the team, galaxy 9422 has stars hotter than 80,000 degrees Celsius.

The research team suspects that the galaxy is in the midst of a brief phase of intense star formation inside a cloud of dense gas that is producing a large number of massive, hot stars. The gas cloud is being hit with so many photons of light from the stars that it is shining extremely brightly.

In addition to its novelty, nebular gas outshining stars is intriguing because it is something predicted in the environments of the universe’s first generation of stars, which astronomers classify as Population III stars.

“We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity. However, its stars are different from what we are familiar with – the exotic stars in this galaxy could be a guide for understanding how galaxies transitioned from primordial stars to the types of galaxies we already know,” said Katz.

At this point, galaxy 9422 is one example of this phase of galaxy development, so there are still many questions to be answered. Are these conditions common in galaxies at this time period, or a rare occurrence? What more can they tell us about even earlier phases of galaxy evolution? Cameron, Katz, and their research colleagues are actively identifying more galaxies to add to this population to better understand what was happening in the universe within the first billion years after the big bang.

“It’s a very exciting time, to be able to use the Webb telescope to explore this time in the universe that was once inaccessible,” Cameron said. “We are just at the beginning of new discoveries and understanding.”

The research paper is published in the Monthly Notices of the Royal Astronomical Society.

A black background sprinkled with small, colourful galaxies in orange, blue, and white. On the left, a third of the way down from the top of the image, a very faint dot of a galaxy is outlined with a white square and pulled out in a graphic to be shown magnified. In the pullout square to the right, the galaxy is a hazy white dot edged in orange, with faint blue projections opposite each other at the 11 o’clock and 5 o’clock positions.
The galaxy GS-NDG-9422 may easily have gone unnoticed. However, what appears as a faint blur in this James Webb Space Telescope image may actually be a groundbreaking discovery that points astronomers on a new path of understanding galaxy evolution in the early universe.
Detailed information on the galaxy’s chemical makeup, captured by Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, indicates that the light we see in this image is coming from the galaxy’s hot gas, rather than its stars. That is the best explanation astronomers have discovered so far to explain the unexpected features in the light spectrum. They think that the galaxy’s stars are so extremely hot and massive that they are heating up the nebular gas in the galaxy to more than 80,000 degrees Celsius, allowing it to shine even brighter in near-infrared light than the stars themselves.
The authors of a new study on Webb’s observations of the galaxy think GS-NDG-9422 may represent a never-before-seen phase of galaxy evolution in the early universe, within the first billion years after the big bang. Their task now is to see if they can find more galaxies displaying the same features.
Credit: NASA, ESA, CSA, STScI, A. Cameron (University of Oxford)

 

Press release from ESA Webb.

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Genetics

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today

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Black Death shaped evolution of immunity genes, setting course for how we respond to disease today

Black Death shaped evolution of immunity genes, setting course for how we respond to disease today

An international team of scientists who analyzed centuries-old DNA from victims and survivors of the Black Death pandemic has identified key genetic differences that determined who lived and who died, and how those aspects of our immune systems have continued to evolve since that time.

Researchers from McMaster University, the University of Chicago, the Pasteur Institute and other organizations analyzed and identified genes that protected some against the devastating bubonic plague pandemic that swept through Europe, Asia and Africa nearly 700 years ago. Their study has been published in the journal Nature.

The same genes that once conferred protection against the Black Death are today associated with an increased susceptibility to autoimmune diseases such as Crohn’s and rheumatoid arthritis, the researchers report.

The team focused on a 100-year window before, during and after the Black Death, which reached London in the mid-1300s.  It remains the single greatest human mortality event in recorded history, killing upwards of 50 per cent of the people in what were then some of the most densely populated parts of the world.

 

More than 500 ancient DNA samples were extracted and screened from the remains of individuals who had died before the plague, died from it or survived the Black Death in London, including individuals buried in the East Smithfield plague pits used for mass burials in 1348-9.  Additional samples were taken from remains buried in five other locations across Denmark.

Scientists searched for signs of genetic adaptation related to the plague, which is caused by the bacterium Yersinia pestis.

They identified four genes that were under selection, all of which are involved in the production of proteins that defend our systems from invading pathogens and found that versions of those genes, called alleles, either protected or rendered one susceptible to plague.

Individuals with two identical copies of a particular gene, known as ERAP2, survived the pandemic at a much higher rates than those with the opposing set of copies, because the ‘good’ copies allowed for more efficient neutralization of Y. pestis by immune cells.

 

“When a pandemic of this nature – killing 30 to 50 per cent of the population – occurs, there is bound to be selection for protective alleles in humans, which is to say people susceptible to the circulating pathogen will succumb. Even a slight advantage means the difference between surviving or passing. Of course, those survivors who are of breeding age will pass on their genes,” explains evolutionary geneticist Hendrik Poinar, an author of the Nature paper, director of McMaster’s Ancient DNA Centre, and a principal investigator with the Michael G. DeGroote Institute for Infectious Disease Research and McMaster’s Global Nexus for Pandemics & Biological Threats.

Europeans living at the time of the Black Death were initially very vulnerable because they had had no recent exposure to Yersinia pestis. As waves of the pandemic occurred again and again over the following centuries, mortality rates decreased.

Researchers estimate that people with the ERAP2 protective allele (the good copy of the gene, or trait), were 40 to 50 per cent more likely to survive than those who did not.

“The selective advantage associated with the selected loci are among the strongest ever reported in humans showing how a single pathogen can have such a strong impact to the evolution of the immune system,” says human geneticist Luis Barreiro, an author on the paper, and professor in Genetic Medicine at the University of Chicago.

tooth Black Death shaped evolution of immunity genes, setting course for how we respond to disease today
Black Death shaped evolution of immunity genes, setting course for how we respond to disease today. Using DNA extracted from teeth of people who died before, during and after the Black Death pandemic, researchers were able to identify genetic differences that dictated who survived and who died from the virus. Credit: Matt Clarke/McMaster University

The team reports that over time our immune systems have evolved to respond in different ways to pathogens, to the point that what had once been a protective gene against plague in the Middle Ages is today associated with increased susceptibility to autoimmune diseases. This is the balancing act upon which evolution plays with our genome.

“This highly original work has been possible only through a successful collaboration between very complementary teams working on ancient DNA, on human population genetics and the interaction between live virulent Yersinia pestis and immune cells,” says Javier Pizarro-Cerda, head of the Yersinia Research Unit and director of the World Health Organization Collaborating Centre for Plague at the Pasteur Institute.

“Understanding the dynamics that have shaped the human immune system is key to understanding how past pandemics, like the plague, contribute to our susceptibility to disease in modern times,” says Poinar.

The findings, the result of seven years of work from graduate student Jennifer Klunk, formally of McMaster’s Ancient DNA Centre and postdoctoral fellow Tauras Vigylas, from the University of Chicago, allowed for an unprecedented look at the immune genes of victims of the Black Death.

The research was funded in part by the Social Sciences and Humanities Research Council of Canada (SSHRC), The National Institutes of Health (NIH) and the Canadian Institute for Advanced Research, under the Humans and the Microbiome program.

 

Press release from McMaster University, by Michelle Donovan on how the Black Death shaped the evolution of immunity genes, setting course for how we respond to disease today.

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