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Astronomy

Webb captures evidence of a lightweight planet around TWA 7

By ScientifiCult 25 June 2025

Webb captures evidence of a lightweight planet around TWA 7

Astronomers using the NASA/ESA/CSA James Webb Space Telescope have captured compelling evidence of a planet with a mass similar to Saturn orbiting the young nearby star TWA 7. If confirmed, this would represent Webb’s first direct image discovery of a planet, and the lightest planet ever seen with this technique.

The international team, led by Dr. Anne-Marie Lagrange, CNRS researcher at the Observatoire de Paris-PSL and Université Grenoble Alpes in France, detected a faint infrared source in the disc of debris surrounding TWA 7 using JWST’s Mid-Infrared Instrument (MIRI) and its coronagraph. The source is located about 1.5 arcseconds from the star on the sky which, at the distance of TWA7, is roughly fifty times the distance of the Earth to the Sun. This matches the expected position of a planet that would explain key features seen in the debris disc.

Using the coronagraph on Webb’s Mid-Infrared Instrument (MIRI) on 21 June 2024, the team carefully suppressed the bright glare of the host star to reveal faint nearby objects. This technique, called high-contrast imaging, enables astronomers to directly detect planets that would otherwise be lost in the overwhelming light from their host star. After subtracting residual starlight using advanced image processing, a faint infrared source was revealed near TWA 7, distinguishable from background galaxies or Solar System objects. The source is located in a gap in one of three dust rings that were discovered around TWA 7 by previous ground-based observations. Its brightness, colour, distance from the star, and position within the ring are consistent with theoretical predictions for a young, cold, Saturn-mass planet sculpting the surrounding debris disc.

“Our observations reveal a strong candidate for a planet shaping the structure of the TWA 7 debris disc, and its position is exactly where we expected to find a planet of this mass,” said Dr. Lagrange.

“This observatory enables us to capture images of planets with masses similar to those in the solar system, which represents an exciting step forward in our understanding of planetary systems, including our own,”

added co-author Mathilde Malin of Johns Hopkins University and the Space Telescope Science Institute in Baltimore.

Initial analysis suggests that the object — referred to as TWA 7b — could be a young, cold planet with a mass around 0.3 times that of Jupiter (~100 Earth masses) and a temperature near 320 Kelvin (roughly 47 degrees Celsius). Its location aligns with a gap in the disc, hinting at a dynamic interaction between the planet and its surroundings.

Debris discs filled with dust and rocky material are found around both young and older stars, although they are more easily detected around younger stars as they are brighter. They often feature visible rings or gaps, thought to be created by planets that have formed around the star, but such a planet has yet to be detected within a debris disc. Once verified, this discovery would mark the first time a planet has been directly associated with sculpting a debris disc and could offer the first observational hint of a trojan disc — a collection of dust trapped in the planet’s orbit.

TWA 7, also known as CE Antliae, is a young (~6.4 million years old) M-type star located about 111 light-years away in the TW Hydrae association. Its nearly face-on disc made it an ideal target for Webb’s high-sensitivity mid-infrared observations.

The findings highlight Webb’s ability to explore previously unseen, low-mass planets around nearby stars. Ongoing and future observations will aim to better constrain the properties of the candidate, verify its planetary status, and deepen our understanding of planet formation and disc evolution in young systems.This preliminary result showcases the exciting new frontier that JWST is opening for exoplanet discovery and characterisation.

These observations were taken as part of the Webb observing programme #3662. The results have been published today in Nature.

An image of a nearby star and its vicinity. The star itself has been blocked out and its bright light has been removed. A dashed circle with a star symbol at the centre of the image marks the star’s location. A fuzzy blue disc surrounds the star. An orange spot, near to the star and inside this disc, is identified as a planet orbiting the star. A fainter orange spot far from the centre marks a distant star. — Astronomers using the NASA/ESA/CSA James Webb Space Telescope have captured compelling evidence of a planet with a mass similar to Saturn orbiting the young nearby star TWA 7. If confirmed, this would represent Webb’s first direct image discovery of a planet, and the lightest planet ever seen with this technique. Using the coronagraph on Webb’s Mid-Infrared Instrument (MIRI) on 21 June 2024, the team carefully suppressed the bright glare of the host star to reveal faint nearby objects. This technique, called high-contrast imaging, enables astronomers to directly detect planets that would otherwise be lost in the overwhelming light from their host star. After subtracting residual starlight using advanced image processing, a faint infrared source was revealed near TWA 7, distinguishable from background galaxies or Solar System objects. The source is located in a gap in one of three dust rings that were discovered around TWA 7 by previous ground-based observations. Its brightness, colour, distance from the star, and position within the ring are consistent with theoretical predictions for a young, cold, Saturn-mass planet sculpting the surrounding debris disc. Initial analysis suggests that the object — referred to as TWA 7b — could be a young, cold planet with a mass around 0.3 times that of Jupiter (~100 Earth masses) and a temperature near 320 Kelvin (roughly 47 degrees Celsius). In this image from MIRI, light from the star TWA 7 has been subtracted. The location of the star is marked with a circle and a star symbol at the centre of the image. This leaves light from the debris disc around the star, as well as other infrared sources, visible. The bright spot to the upper right of the star is the source identified as TWA 7b, within the debris disc. The more distant orange spot visible in the left of the image is an unrelated background star. Only a single MIRI band was used in this image (seen here in orange). The blue colour visible in the image results from an additional band taken by the SPHERE instrument of ESO’s Very Large Telescope (VLT), which showcases the location of the disc surrounding the host star and the exoplanet creating a gap within the disc that is revealed by MIRI.
Credit: ESA/Webb, NASA, CSA, A.M. Lagrange, M. Zamani (ESA/Webb)

Bibliographic information:

Lagrange, AM., Wilkinson, C., Mâlin, M. et al. Evidence for a sub-Jovian planet in the young TWA 7 disk, Nature (2025), DOI: https://doi.org/10.1038/s41586-025-09150-4

Press release from ESA Webb.

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Webb images young, giant exoplanets in HR 8799, detects carbon dioxide

By ScientifiCult 17 March 2025

Webb images young, giant exoplanets in HR 8799, detects carbon dioxide

Findings suggest giant exoplanets in HR 8799 system likely formed like Jupiter and Saturn.

The NASA/ESA/CSA James Webb Space Telescope has captured direct images of multiple gas giant planets within an iconic planetary system. HR 8799, a young system 130 light-years away, has long been a key target for planet formation studies.

This image shows the planetary system HR 8799. The image background is black. At the centre of the image, there is a symbol representing a star labeled HR 8799. This star blocks the light from the host star. There are four exoplanets, which look like fuzzy dots, pictured in the image surrounding the star. Furthest from the star is a fuzzy, faint blue dot, labeled b, at the 10 o’clock position. At the one o’clock position, second furthest from the star is a blueish-white fuzzy dot labeled c. Just below that is an orange dot labeled e. At the four o’clock position, still nearby the star, is another fuzzy white dot labeled d. — The NASA/ESA/CSA James Webb Space Telescope has provided the clearest look yet at the iconic multi-planet system HR 8799. The observations detected carbon dioxide in each of the planets, which provides strong evidence that the system’s four giant planets formed much like Jupiter and Saturn, by slowly building solid cores that attract gas from within a protoplanetary disk. Colours are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by a coronagraph. The colours in this image, which represent different wavelengths captured by Webb’s NIRCam, tell researchers about the temperatures and composition of the planets. HR 8799 b, which orbits around 10.1 billion kilometres from the star, is the coldest of the bunch, and the richest in carbon dioxide. HR 8799 e orbits 2.4 billion kilometres from its star, and likely formed closer to the host star, where there were stronger variations in the composition of material. In this image, the colour blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

The observations indicate that the well-studied planets of HR 8799 are rich in carbon dioxide gas. This provides strong evidence that the system’s four giant planets formed much like Jupiter and Saturn, by slowly building solid cores that attract gas from within a protoplanetary disk.

The results also confirm that Webb can infer the chemistry of exoplanet atmospheres through imaging. This technique complements Webb’s powerful spectroscopic instruments, which resolve the atmospheric composition.

“By spotting these strong carbon dioxide features, we have shown there is a sizable fraction of heavier elements, like carbon, oxygen, and iron, in these planets’ atmospheres,” said William Balmer, of Johns Hopkins University in Baltimore. “Given what we know about the star they orbit, that likely indicates they formed via core accretion, which is an exciting conclusion for planets that we can directly see.”

Graphic titled “Exoplanet HR 8799 e: Carbon Dioxide in Gas Giant Exoplanet” has three data points with error bars and a best-fit model for low metal content and high metal content on a graph of Amount of Light from the Planet on the y-axis versus Wavelength of Light in microns on x-axis. Y-axis ranges from less light at bottom to more light at top. X-axis ranges from 3.6 to 5.0 microns. Webb NIRCam data consists of 3 points, plotted in red, with white error bars above and below each point. The best-fit models are jagged blue and yellow lines with several broad peaks and valleys. Two features are labeled with vertical columns. From 4.3 microns to nearly 4.4 microns, a green column is labeled Carbon Dioxide CO2. From nearly 4.4 microns to nearly 4.8 microns, a red column is labeled Carbon Monoxoide CO2. — This graph shows a spectrum of one of the planets in the HR 8799 system, HR 8799 e, which displays the amounts of near-infrared light detected from the planet by Webb at different wavelengths.
The blue and yellow lines are a best-fit model for an atmosphere that would be either low or high in metals heavier than helium, including carbon, also known as metallicity. The Webb data is consistent with a high metallicity planet. Spectral fingerprints of carbon dioxide and carbon monoxide appear in data collected by Webb’s NIRCam (Near-Infrared Camera). Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

Balmer is the lead author of the study announcing the results published today in The Astrophysical Journal. Balmer and his team’s analysis also includes Webb’s observation of a system 97 light-years away called 51 Eridani.

HR 8799 is a young system about 30 million years old, a fraction of our solar system’s 4.6 billion years. Still hot from their tumultuous formation, the planets within HR 8799 emit large amounts of infrared light that give scientists valuable data on how they formed.

Giant planets can take shape in two ways: by slowly building solid cores with heavier elements that attract gas, just like the giants in our solar system, or when particles of gas rapidly coalesce into massive objects from a young star’s cooling disk, which is made mostly of the same kind of material as the star. Knowing which formation model is more common can give scientists clues to distinguish between the types of planets they find in other systems.

“Our hope with this kind of research is to understand our own solar system, life, and ourselves in comparison to other exoplanetary systems, so we can contextualize our existence,” Balmer said. “We want to take pictures of other solar systems and see how they’re similar or different when compared to ours. From there, we can try to get a sense of how weird our solar system really is—or how normal.”

Of the nearly 6,000 exoplanets discovered, few have been directly imaged, as even giant planets are many thousands of times fainter than their stars. The images of HR 8799 and 51 Eridani were made possible by Webb’s NIRCam (Near-Infrared Camera) coronagraph, which blocks light from bright stars to reveal otherwise hidden worlds.

This image shows the exoplanet 51 Eri b. The image is mostly black, with very faint residual red dots apparent in the central region of the image. At the centre of the image, there is a symbol representing a star labeled 51 Eri. This star blocks the light from the host star. To the left of the circle is a fuzzy bright red circle, which is the exoplanet, labeled b. — The NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera) captured this image of Eridani 51 b, a cool, young exoplanet that orbits 17.7 billion kilometres from its star. Its distance is equivalent to a location between the orbits of Neptune and Saturn in our solar system. The observations detected the planet is rich in carbon dioxide, providing strong evidence that the planet formed much like Jupiter and Saturn, by slowly building a solid core that attracted gas from within a protoplanetary disk.
The 51 Eridani system is 96 light-years from Earth. This image includes filters representing 4.1-micron light as red. Credit: NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI)

This technology allowed the team to look for infrared light emitted by the planets in wavelengths that are absorbed by specific gases. The team found that the four HR 8799 planets contain more heavy elements than previously thought.

“Webb’s unique capabilities are allowing us to explore the wide diversity of these directly-imaged planets for the first time. This gives us important clues as to how such planetary systems have formed.” said Emily Rickman of the European Space Agency, a co-author of the study. “These new observations reiterate how valuable the HR 8799 multi-planet system is as a stepping stone to understand the formation of exoplanetary systems and of our own Solar System.”

The team is paving the way for more detailed observations to determine whether objects they see orbiting other stars are truly giant planets or objects such as brown dwarfs, which form like stars but don’t accumulate enough mass to ignite nuclear fusion.

“We have other lines of evidence that hint at these four HR 8799 planets forming using this bottom-up approach,” said Laurent Pueyo, an astronomer at the Space Telescope Science Institute in Baltimore, who co-led the work. “How common is this for planets we can directly image? We don’t know yet, but we’re proposing more Webb observations to answer that question.”

“We knew Webb could measure colours of the outer planets in directly imaged systems,” added Rémi Soummer, director of STScI’s Russell B. Makidon Optics Lab and former lead for Webb coronagraph operations. “We have been waiting for 10 years to confirm that our finely tuned operations of the telescope would also allow us to access the inner planets. Now the results are in and we can do interesting science with it.”

The NIRCam observations of HR 8799 and 51 Eridani were conducted as part of Guaranteed Time Observations programmes 1194 and 1412 respectively.

Press release from ESA Webb.

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Webb and Hubble telescopes affirm Universe’s expansion rate, puzzle persists

By ScientifiCult 11 March 2024

Webb and Hubble telescopes affirm Universe’s expansion rate, puzzle persists

Webb measurements shed new light on a decade-long mystery.

The rate at which the Universe is expanding, known as the Hubble constant, is one of the fundamental parameters for understanding the evolution and ultimate fate of the cosmos. However, a persistent difference, called the Hubble Tension, is seen between the value of the constant measured with a wide range of independent distance indicators and its value predicted from the afterglow of the Big Bang. The NASA/ESA/CSA James Webb Space Telescope has confirmed that the Hubble Space Telescope’s keen eye was right all along, erasing any lingering doubt about Hubble’s measurements.

One of the scientific justifications for building the NASA/ESA Hubble Space Telescope was to use its observing power to provide an exact value for the expansion rate of the Universe. Prior to Hubble’s launch in 1990, observations from ground-based telescopes yielded huge uncertainties. Depending on the values deduced for the expansion rate, the Universe could be anywhere between 10 and 20 billion years old. Over the past 34 years Hubble has shrunk this measurement to an accuracy of less than one percent, splitting the difference with an age value of 13.8 billion years. This has been accomplished by refining the so-called ‘cosmic distance ladder’ by measuring important milepost markers known as Cepheid variable stars.

A horizontal two-panel image of pixelated, black-and-white star fields. The left image is labelled Webb Near-IR and has a few dozen points of light of varying brightness. At the centre of the image, one bright point is circled. The right image is labelled Hubble Near-IR and has more indistinct, blurry patches whose overall brightness is similar to the more defined regions in the left image. At the centre, a light grey pixel is circled. — At the centre of these side-by-side images is a special class of star used as a milepost marker for measuring the Universe’s rate of expansion — a Cepheid variable star. The two images are very pixelated because each is a very zoomed-in view of a distant galaxy. Each of the pixels represents one or more stars. The image from the James Webb Space Telescope is significantly sharper at near-infrared wavelengths than Hubble (which is primarily a visible-ultraviolet light telescope). By reducing the clutter with Webb’s crisper vision, the Cepheid stands out more clearly, eliminating any potential confusion. Webb was used to look at a sample of Cepheids and confirmed the accuracy of the previous Hubble observations that are fundamental to precisely measuring the Universe’s expansion rate and age.
Credit: NASA, ESA, CSA, STScI, A. Riess (JHU/STScI)

However, the Hubble value does not agree with other measurements that imply that the Universe was expanding faster after the Big Bang. These observations were made by the ESA Planck satellite’s mapping of the cosmic microwave background radiation — a blueprint for how the Universe would evolve structure after it cooled down from the Big Bang.

The simple solution to the dilemma would be to say that maybe the Hubble observations are wrong, as a rresult of some inaccuracy creeping into its measurements of the deep-space yardsticks. Then along came the James Webb Space Telescope, enabling astronomers to crosscheck Hubble’s results. Webb’s infrared views of Cepheids agreed with Hubble’s optical-light data. Webb confirmed that the Hubble telescope’s keen eye was right all along, erasing any lingering doubt about Hubble’s measurements.

The bottom line is that the so-called Hubble Tension between what happens in the nearby Universe compared to the early Universe’s expansion remains a nagging puzzle for cosmologists. There may be something woven into the fabric of space that we don’t yet understand.

Does resolving this discrepancy require new physics? Or is it a result of measurement errors between the two different methods used to determine the rate of expansion of space?

Hubble and Webb have now tag-teamed to produce definitive measurements, furthering the case that something else — not measurement errors — is influencing the expansion rate.

“With measurement errors negated, what remains is the real and exciting possibility that we have misunderstood the Universe,”

said Adam Riess, a physicist at Johns Hopkins University in Baltimore. Riess holds a Nobel Prize for co-discovering the fact that the Universe’s expansion is accelerating, owing to a mysterious phenomenon now called ‘dark energy’.

As a crosscheck, an initial Webb observation in 2023 confirmed that Hubble’s measurements of the expanding Universe were accurate. However, hoping to relieve the Hubble Tension, some scientists speculated that unseen errors in the measurement may grow and become visible as we look deeper into the Universe. In particular, stellar crowding could affect brightness measurements of more distant stars in a systematic way.

The SH0ES (Supernova H0 for the Equation of State of Dark Energy) team, led by Riess, obtained additional observations with Webb of objects that are critical cosmic milepost markers, known as Cepheid variable stars, which can now be correlated with the Hubble data.

“We’ve now spanned the whole range of what Hubble observed, and we can rule out a measurement error as the cause of the Hubble Tension with very high confidence,” Riess said.

The team’s first few Webb observations in 2023 were successful in showing Hubble was on the right track in firmly establishing the fidelity of the first rungs of the so-called cosmic distance ladder.

Astronomers use various methods to measure relative distances in the Universe, depending upon the object being observed. Collectively these techniques are known as the cosmic distance ladder — each rung or measurement technique relies upon the previous step for calibration.

But some astronomers suggested that, moving outward along the ‘second rung’, the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance. Such inaccuracies could occur because the light of a Cepheid could blend with that of an adjacent star — an effect that could become more pronounced with distance as stars crowd together on the sky and become harder to distinguish from one another.

The observational challenge is that past Hubble images of these more distant Cepheid variables look more huddled and overlapping with neighbouring stars at ever greater distances between us and their host galaxies, requiring careful accounting for this effect. Intervening dust further complicates the certainty of the measurements in visible light. Webb slices through the dust and naturally isolates the Cepheids from neighbouring stars because its vision is sharper than Hubble’s at infrared wavelengths.

“Combining Webb and Hubble gives us the best of both worlds. We find that the Hubble measurements remain reliable as we climb farther along the cosmic distance ladder,” said Riess.

A face-on spiral galaxy with four spiral arms that curve outward in a counterclockwise direction. The spiral arms are filled with young, blue stars and peppered with purplish star-forming regions that appear as small blobs. The middle of the galaxy is much brighter and more yellowish, and has a distinct narrow linear bar angled from 11 o’clock to 5 o’clock. Dozens of red background galaxies are scattered across the image. The background of space is black. — This image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. This is the most distant galaxy in which Hubble has identified Cepheid variable stars. These are important milepost markers for measuring the expansion rate of the Universe. The distance calculated from Cepheids has been cross-correlated with a Type Ia supernova in the galaxy. Type Ia supernovae are so bright they are used to measure cosmic distances far beyond the range of the Cepheids, extending measurements of the Universe’s expansion rate deeper into space.
Credit: NASA, ESA, CSA, STScI, A. Riess (JHU/STScI)

The new Webb observations include five host galaxies of eight Type Ia supernovae containing a total of 1000 Cepheids, and reach out to the farthest galaxy where Cepheids have been well measured — NGC 5468, at a distance of 130 million light-years.

“This spans the full range where we made measurements with Hubble. So, we’ve gone to the end of the second rung of the cosmic distance ladder,”

said co-author Gagandeep Anand of the Space Telescope Science Institute in Baltimore, which operates the Webb and Hubble Telescopes for NASA.

Together, Hubble’s and Webb’s confirmation of the Hubble Tension sets up other observatories to possibly settle the mystery, including NASA’s upcoming Nancy Grace Roman Space Telescope and ESA’s recently launched Euclid mission.

At present it’s as though the distance ladder observed by Hubble and Webb has firmly set an anchor point on one shoreline of a river, and the afterglow of the Big Bang observed by Planck from the beginning of the Universe is set firmly on the other side. How the Universe’s expansion was changing in the billions of years between these two endpoints has yet to be directly observed.

“We need to find out if we are missing something on how to connect the beginning of the Universe and the present day,” said Riess.

These findings were published in the 6 February 2024 issue of The Astrophysical Journal Letters.

Press release from ESA Webb.

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Webb Confirms Its First Exoplanet, LHS 475 b

By ScientifiCult 11 January 2023

Researchers have confirmed the presence of an exoplanet, a planet that orbits another star, using the NASA/ESA/CSA James Webb Space Telescope for the first time: formally classified as LHS 475 b, the planet is almost exactly the same size as our own, clocking in at 99% of Earth’s diameter.

The research team is led by Kevin Stevenson and Jacob Lustig-Yaeger, both of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. The team chose to observe this target with Webb after carefully reviewing data from NASA’s Transiting Exoplanet Survey Satellite (TESS) which hinted at the planet’s existence. Webb’s Near-Infrared Spectrograph (NIRSpec) captured the planet easily and clearly with only two transit observations.

“There is no question that the planet is there. Webb’s pristine data validate it,” said Lustig-Yaeger. “The fact that it is also a small, rocky planet is impressive for the observatory,” Stevenson added.

“These first observational results from an Earth-sized, rocky planet open the door to many future possibilities for studying rocky planet atmospheres with Webb,” agreed Mark Clampin, Astrophysics Division director at NASA Headquarters in Washington. “Webb is bringing us closer and closer to a new understanding of Earth-like worlds outside the Solar System, and the mission is only just getting started.”

Exoplanet LHS 475 b (Illustration) — Based on new evidence from the NASA/ESA/CSA James Webb Space Telescope, this illustration shows the exoplanet LHS 475 b. It is rocky and almost precisely the same size as Earth. The planet whips around its star in just two days, far faster than any planet in the Solar System. Researchers will follow up this summer with additional observations with Webb, which they hope will allow them to definitively conclude if the planet has an atmosphere. LHS 475 b is relatively close, 41 light-years away, in the constellation Octans.
Credit:
NASA, ESA, CSA, L. Hustak (STScI)

Among all operating telescopes, only Webb is capable of characterising the atmospheres of Earth-sized exoplanets. The team attempted to assess what is in the planet’s atmosphere by analysing its transmission spectrum. Although the data show that this is an Earth-sized terrestrial planet, they do not yet know if it has an atmosphere.

“The observatory’s data are beautiful,” said Erin May, also of the Johns Hopkins University Applied Physics Laboratory. “The telescope is so sensitive that it can easily detect a range of molecules, but we can’t yet draw any definitive conclusions about the planet’s atmosphere.”

Although the team can’t conclude what is present, they can definitely say what is not present.

“There are some terrestrial-type atmospheres that we can rule out,” explained Lustig-Yaeger. “It can’t have a thick methane-dominated atmosphere, similar to that of Saturn’s moon Titan.”

The team also notes that while it’s possible the planet has no atmosphere, there are some atmospheric compositions that have not been ruled out, such as a pure carbon dioxide atmosphere.

“Counterintuitively, a 100% carbon dioxide atmosphere is so much more compact that it becomes very challenging to detect,” said Lustig-Yaeger.

Exoplanet LHS 475 b — How do researchers spot a distant planet? By observing the changes in light as it orbits its star. A light curve from the NASA/ESA/CSA James Webb Space Telescope’s Near-Infrared Spectrograph (NIRSpec) shows the change in brightness from the LHS 475 star system over time as the planet transited the star on 31 August 2022. LHS 475 b is a rocky, Earth-sized exoplanet that orbits a red dwarf star roughly 41 light-years away, in the constellation Octans. The planet is extremely close to its star, completing one orbit in two Earth-days. Confirmation of the presence of the planet was made possible by Webb’s data. Credit: NASA, ESA, CSA, L. Hustak (STScI), K. Stevenson, J. Lustig-Yaeger, E. May (Johns Hopkins University Applied Physics Laboratory), G. Fu (Johns Hopkins University), and S. Moran (University of Arizona)

Even more precise measurements are required for the team to distinguish a pure carbon dioxide atmosphere from no atmosphere at all. The researchers are scheduled to obtain additional spectra with further observations this summer.

Webb also revealed that the planet is a few hundred degrees warmer than Earth, so if clouds are detected it may lead the researchers to conclude that the planet is more like Venus, which has a carbon dioxide atmosphere and is perpetually shrouded in thick cloud.

“We’re at the forefront of studying small, rocky exoplanets,” Lustig-Yaeger said. “We have barely begun scratching the surface of what their atmospheres might be like.”

The researchers also confirmed that the planet completes an orbit in just two days, information that was almost instantaneously revealed by Webb’s precise light curve. Although LHS 475 b is closer to its star than any planet in the Solar System, its red dwarf star is less than half the temperature of the Sun, so the researchers project it still could support an atmosphere.

A flat line in a transmission spectrum, like this one, can be exciting — it can tell us a lot about the planet. Researchers used the NASA/ESA/CSA James Webb Space Telescope’s Near-Infrared Spectrograph (NIRSpec) to observe exoplanet LHS 475 b on 31 August 2022. As this spectrum shows, Webb did not observe a detectable quantity of any element or molecule. The data (white dots) are consistent with a featureless spectrum representative of a planet that has no atmosphere (yellow line). The purple line represents a pure carbon dioxide atmosphere and is indistinguishable from a flat line at the current level of precision. The green line represents a pure methane atmosphere, which is not favoured since methane, if present, would be expected to block more starlight at 3.3 microns.
Credit:
NASA, ESA, CSA, L. Hustak (STScI), K. Stevenson, J. Lustig-Yaeger, E. May (Johns Hopkins University Applied Physics Laboratory), G. Fu (Johns Hopkins University), and S. Moran (University of Arizona)

The researchers’ findings have opened up the possibility of pinpointing Earth-sized planets orbiting smaller red dwarf stars.

“This rocky planet confirmation highlights the precision of the mission’s instruments,” Stevenson said. “And it is only the first of many discoveries that it will make.” Lustig-Yaeger agreed: “With this telescope, rocky exoplanets are the new frontier.”

LHS 475 b is relatively close, at only 41 light-years away, in the constellation Octans.

The team’s results were presented at a press conference of the American Astronomical Society (AAS) on Wednesday 11 January, 2023.

Webb Confirms Its First Exoplanet, LHS 475 b — Based on new evidence from the NASA/ESA/CSA James Webb Space Telescope, this illustration reflects the conclusion that the exoplanet LHS 475 b is rocky and almost precisely the same size as Earth. The planet whips around its star in just two days, far faster than any planet in the Solar System. Researchers will follow up this summer with additional observations with Webb, which they hope will allow them to definitively conclude if the planet has an atmosphere. LHS 475 b is relatively close, 41 light-years away, in the constellation Octans.
Credit:
NASA, ESA, CSA, L. Hustak (STScI)

Press release from ESA Webb

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