The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.
The largest and nearest of the giant outer planets, Jupiter’s colourful clouds present an ever-changing kaleidoscope of shapes and colours. This is a planet where there is always stormy weather: cyclones, anticyclones, wind shear, and the largest storm in the Solar System, the Great Red Spot. Jupiter has no solid surface and is perpetually covered with largely ammonia ice-crystal clouds that are only about 48 kilometres thick in an atmosphere that’s tens of thousands of kilometres deep and give the planet its banded appearance. The bands are produced by air flowing in different directions at various latitudes with speeds approaching 560 kilometres per hour. Lighter-hued areas where the atmosphere rises are called zones. Darker regions where air falls are called belts. When these opposing flows interact, storms and turbulence appear. Hubble tracks these dynamic changes every year with unprecedented clarity, and there are always surprises. The many large storms and small white clouds seen in Hubble’s latest images are evidence for a lot of activity going on in Jupiter’s atmosphere right now.
The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.
Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter’s atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.
Credit:
NASA, ESA, J. DePasquale (STScI), A. Simon (NASA-GSFC)
The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images, taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.
[left image] – Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter’s atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.
[right image] – Storm activity also appears in the opposite hemisphere. A pair of storms: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.
The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.
Toward the left edge of the image is the innermost Galilean moon, Io — the most volcanically active body in the Solar System, despite its small size (only slightly larger than Earth’s moon). Hubble resolves volcanic outflow deposits on the surface. Hubble’s sensitivity to blue and violet wavelengths clearly reveals interesting surface features.
Credit: NASA, ESA, J. DePasquale (STScI), A. Simon (NASA-GSFC)
The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in this new image, taken on 6 January 2024, that captures both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.
A pair of storms is visible: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.
The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.
Toward the left edge of the image is the innermost Galilean moon, Io — the most volcanically active body in the Solar System, despite its small size (only slightly larger than Earth’s moon). Hubble resolves volcanic outflow deposits on the surface. Hubble’s sensitivity to blue and violet wavelengths clearly reveals interesting surface features.
Credit:
NASA, ESA, J. DePasquale (STScI), A. Simon (NASA-GSFC)
This 12-panel series of NASA/ESA Hubble Space Telescope images, taken on 5–6 January 2024, presents snapshots of a full rotation of the giant planet Jupiter. The Great Red Spot can be used to measure the planet’s real rotation rate of nearly 10 hours. The innermost Galilean satellite, Io, is seen in several frames, along with its shadow crossing over Jupiter’s cloud tops. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL).
Credit:
NASA, ESA, J. DePasquale (STScI), A. Simon (NASA-GSFC)
The giant planet Jupiter, in all its banded glory, is revisited by the NASA/ESA Hubble Space Telescope in these latest images taken on 5–6 January 2024, that capture both sides of the planet. Hubble monitors Jupiter and the other outer Solar System planets every year under the Outer Planet Atmospheres Legacy programme (OPAL). This is because these large worlds are shrouded in clouds and hazes stirred up by violent winds, leading to a kaleidoscope of ever-changing weather patterns.
[left image] – Big enough to swallow Earth, the classic Great Red Spot stands out prominently in Jupiter’s atmosphere. To its lower right, at a more southerly latitude, is a feature sometimes dubbed Red Spot Jr. This anticyclone was the result of storms merging in 1998 and 2000, and it first appeared red in 2006 before returning to a pale beige in subsequent years. This year it is somewhat redder again. The source of the red coloration is unknown but may involve a range of chemical compounds: sulphur, phosphorus or organic material. Staying in their lanes, but moving in opposite directions, Red Spot Jr. passes the Great Red Spot about every two years. Another small red anticyclone appears in the far north.
[right image] – Storm activity also appears in the opposite hemisphere. A pair of storms: a deep red cyclone and a reddish anticyclone, appear to be next to each other at right of centre. They look so red that at first glance, it looks like Jupiter skinned a knee. These storms are rotating in opposite directions, indicating an alternating pattern of high- and low-pressure systems. For the cyclone, there’s an upwelling on the edges with clouds descending in the middle causing a clearing in the atmospheric haze.
The storms are expected to bounce past each other because their opposing clockwise and counterclockwise rotations make them repel each other.
Toward the left edge of the image is the innermost Galilean moon, Io — the most volcanically active body in the Solar System, despite its small size (only slightly larger than Earth’s moon). Hubble resolves volcanic outflow deposits on the surface. Hubble’s sensitivity to blue and violet wavelengths clearly reveals interesting surface features.
Credit:
NASA, ESA, J. DePasquale (STScI), A. Simon (NASA-GSFC)
This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble’s ultra-sharp vision reveals a phenomenon called ring spokes. Saturn’s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern. In 1981, NASA’s Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble’s Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets. Hubble’s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years. This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth’s diameter! The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn’s powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery. Credit: Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC)
This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble’s ultra-sharp vision reveals a phenomenon called ring spokes.
Saturn’s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.
In 1981, NASA’s Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble’s Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.
Hubble’s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.
This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth’s diameter!
The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn’s powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery. This image was created with Hubble data from proposal 16995 (A. Simon).
This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble’s ultra-sharp vision reveals a phenomenon called ring spokes. Saturn’s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern. In 1981, NASA’s Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble’s Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets. Hubble’s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years. This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth’s diameter! The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn’s powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery. Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC)
JWST rings in the holidays with the ringed planet Uranus
The NASA/ESA/CSA James Webb Space Telescope recently trained its sights on unusual and enigmatic Uranus, an ice giant that spins on its side. Webb captured this dynamic world with rings, moons, storms, and other atmospheric features — including a seasonal polar cap. The image expands upon a two-colour version released earlier this year, adding additional wavelength coverage for a more detailed look.
This image of Uranus from NIRCam (Near-Infrared Camera) on the NASA/ESA/CSA James Webb Space Telescope shows the planet and its rings in new clarity. The planet’s seasonal north polar cap gleams in a bright white, and Webb’s exquisite sensitivity resolves Uranus’ dim inner and outer rings, including the Zeta ring—the extremely faint and diffuse ring closest to the planet. This Webb image also shows 14 of the planet’s 27 moons: Oberon, Titania, Umbriel, Juliet, Perdita, Rosalind, Puck, Belinda, Desdemona, Cressida, Ariel, Miranda, Bianca, and Portia. One day on Uranus is about 17 hours, so the planet’s rotation is relatively quick. This makes it supremely difficult for observatories with a sharp eye like Webb to capture one simple image of the entire planet – storms and other atmospheric features, and the planet’s moons, move visibly within minutes. This image combines several longer and shorter exposures of this dynamic system to correct for those slight changes throughout the observing time. Webb’s extreme sensitivity also picks up a smattering of background galaxies—most appear as orange smudges, and there are two larger, fuzzy white galaxies to the right of the planet in this field of view. Credit: NASA, ESA, CSA, STScI
With its exquisite sensitivity, Webb captured Uranus’ dim inner and outer rings, including the elusive Zeta ring—the extremely faint and diffuse ring closest to the planet. It also imaged many of the planet’s 27 known moons, even seeing some small moons within the rings.
In visible wavelengths, Uranus appeared as a placid, solid blue ball. In infrared wavelengths, Webb is revealing a strange and dynamic ice world filled with exciting atmospheric features.
One of the most striking of these is the planet’s seasonal north polar cap. Compared to the image from earlier this year, some details of the cap are easier to see in these newer images. These include the bright, white, inner cap and the dark lane in the bottom of the polar cap, toward the lower latitudes.
Several bright storms can also be seen near and below the southern border of the polar cap. The number of these storms, and how frequently and where they appear in Uranus’s atmosphere, might be due to a combination of seasonal and meteorological effects.
This image of Uranus from NIRCam (Near-Infrared Camera) on the NASA/ESA/CSA James Webb Space Telescope shows the planet and its rings in new clarity. The Webb image exquisitely captures Uranus’s seasonal north polar cap, including the bright, white, inner cap and the dark lane in the bottom of the polar cap. Uranus’ dim inner and outer rings are also visible in this image, including the elusive Zeta ring—the extremely faint and diffuse ring closest to the planet. This Webb image also shows 9 of the planet’s 27 moons. They are the blue dots that surround the planet’s rings. Clockwise starting at 2 o’clock, they are: Rosalind, Puck, Belinda, Desdemona, Cressida, Bianca, Portia, Juliet, and Perdita. The orbits of these moons share the 98-degree tilt of their parent planet relative to the plane of the solar system. One day on Uranus is about 17 hours, so the planet’s rotation is relatively quick. This makes it supremely difficult for observatories with a sharp eye like Webb to capture one simple image of the entire planet – storms and other atmospheric features, and the planet’s moons, move visibly within minutes. This image combines several longer and shorter exposures of this dynamic system to correct for those slight changes throughout the observing time. Credit: NASA, ESA, CSA, STScI
The polar cap becomes prominent when the planet’s pole begins to point towards the Sun, as it approaches solstice and receives more sunlight. Uranus reaches its next solstice in 2028, and astronomers are eager to watch any possible changes in the structure of these features. Webb will help disentangle the seasonal and meteorological effects that influence Uranus’s storms, which is critical to help astronomers understand the planet’s complex atmosphere.
Because Uranus orbits on its side at a tilt of about 98 degrees, it has the most extreme seasons in the Solar System. For nearly a quarter of each Uranian year, the Sun shines over one pole, plunging the other half of the planet into a dark, 21-year-long winter.
With Webb’s unparalleled infrared resolution and sensitivity, astronomers now see Uranus and its unique features with groundbreaking new clarity. These details, especially of the close-in Zeta ring, will be invaluable to planning any future missions to Uranus.
Uranus can also serve as a proxy for studying the many far-off, similarly sized exoplanets that have been discovered in the last few decades. This “exoplanet in our backyard” can help astronomers understand how planets of this size work, what their meteorology is like, and how they formed. This can in turn help us understand our own solar system as a whole by placing it in a larger context.
This image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam), shows compass arrows, scale bar, and colour key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). The scale bar is labelled 16 arcseconds. The length of the scale bar is approximately one-seventh the total width of the image This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter. Webb’s NIRCam filters for this image are F140M (blue), F210M (cyan), F300M (yellow), and F460M (orange). Credit: NASA, ESA, CSA, STScI
Webb finds carbon source on surface of Jupiter’s moon Europa
Jupiter’s moon Europa is one of a handful of worlds in our Solar System that could potentially harbour conditions suitable for life. Previous research has shown that beneath its water-ice crust lies a salty ocean of liquid water with a rocky seafloor. However, planetary scientists had not confirmed whether or not that ocean contained the chemicals needed for life, particularly carbon.
Webb’s NIRCam (Near Infrared Camera) captured this picture of the surface of Jupiter’s moon Europa. Webb identified carbon dioxide on the icy surface of Europa that likely originated in the moon’s subsurface ocean. This discovery has important implications for the potential habitability of Europa’s ocean. The moon appears mostly blue because it is brighter at shorter infrared wavelengths. The white features correspond with the chaos terrain Powys Regio (left) and Tara Regio (centre and right), which show enhanced carbon dioxide ice on the surface. Credit: NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)
Astronomers using data from the NASA/ESA/CSA James Webb Space Telescope have identified carbon dioxide in a specific region on the icy surface of Europa. Analysis indicates that this carbon likely originated in the subsurface ocean and was not delivered by meteorites or other external sources. Moreover, it was deposited on a geologically recent timescale. This discovery has important implications for the potential habitability of Europa’s ocean.
“On Earth, life likes chemical diversity — the more diversity, the better. We’re carbon-based life. Understanding the chemistry of Europa’s ocean will help us determine whether it’s hostile to life as we know it, or whether it might be a good place for life,”
said Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of one of two independent papers describing the findings.
“We now think that we have observational evidence that the carbon we see on Europa’s surface came from the ocean. That’s not a trivial thing. Carbon is a biologically essential element,”
added Samantha Trumbo of Cornell University in Ithaca, New York, lead author of the second paper analysing this data.
NASA plans to launch its Europa Clipper spacecraft, which will perform dozens of close flybys of Europa to further investigate whether it could have conditions suitable for life, in October 2024.
A Surface-Ocean Connection
Webb finds that on Europa’s surface, carbon dioxide is most abundant in a region called Tara Regio — a geologically young area of generally resurfaced terrain known as ‘chaos terrain’. The surface ice has been disrupted, and there has likely been an exchange of material between the subsurface ocean and the icy surface.
“Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,” explained Trumbo. “Now we’re seeing that carbon dioxide is heavily concentrated there as well. We think this implies that the carbon probably has its ultimate origin in the internal ocean.”
“Scientists are debating to what extent Europa’s ocean connects to its surface. I think that question has been a big driver of Europa exploration,” said Villanueva. “This suggests that we may be able to learn some basic things about the ocean’s composition even before we drill through the ice to get the full picture.”
Both teams identified the carbon dioxide using data from the integral field unit of Webb’s Near-Infrared Spectrograph (NIRSpec). This instrument mode provides spectra with a resolution of 320 x 320 kilometres over a field of view of diameter 3128 kilometres on the surface of Europa, allowing astronomers to determine where specific chemicals are located.
This graphic shows a map of Europa’s surface with NIRCam (Near Infrared Camera) in the first panel and compositional maps derived from NIRSpec/IFU (Near Infrared Spectrograph’s Integral Field Unit) data in the following three panels. In the compositional maps, the white pixels correspond to carbon dioxide in the large-scale region of disrupted chaos terrain known as Tara Regio (centre and right), with additional concentrations within portions of the chaos region Powys Regio (left). The second and third panels show evidence of crystalline carbon dioxide, while the fourth panel indicates a complexed and amorphous form of carbon dioxide. Astronomers using Webb have found carbon on the chaos terrain of Tara Regio and Powys Regio. Surface ices in these regions have been disrupted, and there has likely been a relatively recent exchange of material between the subsurface ocean and the icy surface. Carbon, a universal building block for life as we know it, likely originated in Europa’s ocean. The discovery suggests a potentially habitable environment in the salty subsurface ocean of Europa. The NIRSpec/IFU images appear pixelated because Europa is 10 x 10 pixels across in the detector’s field of view. Credit: NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)
Carbon dioxide isn’t stable on Europa’s surface. Therefore, the scientists say it’s likely that it was supplied on a geologically recent timescale — a conclusion bolstered by its concentration in a region of young terrain.
“These observations only took a few minutes of the observatory’s time,”
said Heidi Hammel of the Association of Universities for Research in Astronomy, a Webb interdisciplinary scientist leading Webb’s Cycle 1 Guaranteed Time Observations of the Solar System.
“Even in this short period of time, we were able to do really big science. This work gives a first hint of all the amazing Solar System science we’ll be able to do with Webb.”
Searching for a Plume
Villanueva’s team also looked for evidence of a plume of water vapour erupting from Europa’s surface. Researchers using the NASA/ESA Hubble Space Telescope reported tentative detections of plumes in 2013, 2016, and 2017. However, finding definitive proof has been difficult.
The new Webb data show no evidence of plume activity, which allowed Villanueva’s team to set a strict upper limit on the rate at which material is potentially being ejected. The team stressed, however, that their non-detection does not rule out a plume.
“There is always a possibility that these plumes are variable and that you can only see them at certain times. All we can say with 100% confidence is that we did not detect a plume at Europa when we made these observations with Webb,” said Hammel.
These findings may help inform NASA’s Europa Clipper mission, as well as ESA’s Jupiter Icy Moons Explorer, Juice, which was launched on 14 April 2023. Juice will make detailed observations of the giant gas planet and its three large ocean-bearing moons — Ganymede, Callisto and Europa — with a suite of remote sensing, geophysical and in situ instruments. The mission will characterise these moons as both planetary objects and possible habitats, explore Jupiter’s complex environment in depth, and study the wider Jupiter system as an archetype for gas giants across the Universe.
“This is a great first result of what Webb will bring to the study of Jupiter’s moons,” said co-author Guillaume Cruz-Mermy, formerly of Université Paris-Saclay and current ESA Research Fellow at the European Space Astronomy Centre. “I’m looking forward to seeing what else we can learn about their surface properties from these and future observations.”
The two papers associated with this research will be published in Science on 21 September 2023.
Webb’s NIRCam (Near Infrared Camera) captured this picture of the surface of Jupiter’s moon Europa. Webb identified carbon dioxide on the icy surface of Europa that likely originated in the moon’s subsurface ocean. This discovery has important implications for the potential habitability of Europa’s ocean. The moon appears mostly blue because it is brighter at shorter infrared wavelengths. The white features correspond with the chaos terrain Powys Regio (left) and Tara Regio (centre and right), which show enhanced carbon dioxide ice on the surface. Credit: NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)
GJ 367 b, A PLANET WITH AN IRON HEART IN AN EXTRASOLAR SYSTEM
THE DISCOVERY MADE BY A TEAM AT THE UNIVERSITY OF TURIN ADDS TO THE PUZZLE HOW PLANETS FORM
Researchers at the University of Turin and at the Thüringer Landessternwarte have confirmed that the extrasolar planet GJ 367 b has an ultra-high density – almost twice the density of Earth. The research team also found two more planets that orbit the same star.
Over the past decades, astronomers have found several thousand extrasolar planets. Extrasolar planets orbit stars outside our solar system. The next frontier in this research field is to learn more about their composition and internal structure, in order to develop a better understanding of how planets form.
Elisa Goffo is part of the international KESPRINT collaboration, which confirmed that the ultra-short period exoplanet GJ 367 b, whose orbital period is only 7.7 hours, is also ultra-dense. The density of a planet can be determined from its mass and radius. GJ 367 b is ultra-dense because the researchers found its density to be 10.2 grams per cubic centimeter. That is almost twice the density of Earth, suggesting that this extrasolar planet consists almost entirely of iron.
An unusual composition
Such a composition of a planet is very rare, raising questions about its formation.
“You could compare GJ 367 b to an Earth-like planet with its rocky mantle stripped away. This could have important implications for the formation of GJ 367 b. We believe that the planet might have formed like the Earth, with a dense core made mainly of iron, surrounded by a silicate-rich mantle. A catastrophic event could have stripped away its rocky mantle, leaving the dense core of the planet naked. Alternatively, GJ 367 b was born in an iron-rich region of the protoplanetary disc”,
explains Elisa Goffo. While observing GJ 367 b, the team discovered two additional low-mass planets that orbit around the star GJ 367 in 11.5 days and 34 days, respectively. These three planets and their star comprise an extrasolar system.
GJ 367 b was first found with the Transiting Exoplanet Survey Satellite (TESS), a space telescope operated by NASA. TESS uses the transit method to measure the radii of exoplanets – among other properties. In order to precisely measure the mass of GJ 367 b and confirm that the planet has a very high density, the KESPRINT researchers at the University of Turin and at the Thüringer Landessternwarte acquired nearly 300 radial velocity measurements using the HARPS spectrograph, a high-precision instrument installed at the 3.6 meter telescope operated by the European Southern Observatory (ESO) at La Silla Observatory, Chile.
“Thanks to our intensive observations with the HARPS spectrograph we discovered the presence of two additional low-mass planets with orbital periods of 11.5 and 34 days, which reduce the number of possible scenarios that might have led to the formation of such a dense planet”, says Davide Gandolfi, Professor at the University of Turin. “While GJ 367 b might have formed in an iron-rich environment, we do not exclude a formation scenario involving violent events like giant planet collisions.”
Artie Hatzes, director at the Thüringer Landessternwarte, underscores the relevance of this discovery: “GJ 367 b is an extreme case of an exoplanet. Before we can develop viable theories of its formation, we must precisely measure the planetary mass and radius. We expect an extrasolar system to consist of several planets, so it was important to search for and to find other planets orbiting in the system – to study its architecture.”
MORE INFORMATION
KESPRINT: Consisting of more than 40 members in nine countries (Czech Republic, Denmark, Germany, Italy, Japan, Spain, Sweden, UK, USA), the KESPRINT research consortium is devoted to the confirmation and characterization of transiting exoplanets found by space missions (e.g. Kepler, K2, TESS), with a special emphasis on the characterization of the smallest planets. Its members are from the Dipartimento di Fisica, Università di Torino, Italy, Thüringer Landessternwarte Tautenburg, Germany, Institute of Planetary Research, German Aerospace Center (DLR), Germany, Technische Universität Berlin, Germany, Rheinisches Institut für Umweltforschung an der Universität zu Köln, Germany, Astronomical Institute of the Czech Academy of Sciences, Czech Republic, Chalmers University of Technology, Sweden, Instituto de Astrofísica de Canarias, Spain, Mullard Space Science Laboratory, University College London, UK, University of Oxford, UK, Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Denmark, Astronomy Department and Van Vleck Observatory, Wesleyan University, USA, McDonald Observatory, The University of Texas at Austin, USA, The University of Tokyo, Japan, Astrobiology Center, National Institute of Natural Sciences, Japan.
GJ 367 b and the exoplanet naming convention: Planets are usually named after their host stars, adding a lowercase letter. A planet around the star GJ 367 is called GJ 367 b, c, or d. However, the planet GJ 367 b and its star GJ 367 were named in 2022 during the “NameExoWorlds” project coordinated by the International Astronomical Union. The planet GJ 367 b is called Tahay and its star is called Añañuca, after Chilean wildflowers.
The 7.7 hours period during which GJ 367 b orbits its star stands out even among other ultra-short period planets because it is such a short orbit. One year on this planet is only 7.7 hours long. Its mass is 60 % that of Earth’s mass. Its radius is 70 % that of Earth’s radius. Therefore, it is smaller and less massive than the Earth.
Due to its proximity to the host star, the dayside surface of the planet is expected to have a temperature of almost 1.100 degrees Celsius. The star GJ 367 (Añañuca) is located roughly 31 light years from Earth, i.e., it takes about 31 years for the light to travel this distance.
How the transit method works: NASA’s TESS telescope uses the transit method to search for planets around stars other than the Sun. A transit occurs when a planet moves between its host star and us. Whenever it passes in front of its star, it blocks a small portion of the star’s light. The transit method measures this change in brightness, which yields the orbital period and inclination, the planetary radius, and other parameters.
How the radial velocity method works: The KESPRINT team observes exoplanets with the radial velocity method, which detects the existence of a planet around a star via the Doppler effect. We usually say that planets orbit stars, but that’s not entirely true: planets and stars orbit around their common center of mass! Stars emit light at different colors that become bluer or redder depending on whether the stars are moving toward or away from us while orbiting around the center of mass. When combined with the transit method, radial velocity measurements provide the mass of the planet.
The Physics Department at the University of Turin. Over the past decade, the Exoplanet group at the Physics Department of the University of Turin has focused on the detection and characterization of planets orbiting stars other than the Sun, especially those transiting their host stars, combining space-based observations with high-precision spectroscopy. The group at the University of Turin has led and coordinated the observations of GJ 367 carried out with the HARPS spectrograph.
The James Webb Space Telescope adds another ringed world with new image of Uranus
Webb’s infrared image highlights the planet’s dramatic rings and dynamic atmosphere.
Following in the footsteps of the Neptune image released in 2022, the NASA/ESA/CSA James Webb Space Telescope has taken a stunning image of the Solar System’s other ice giant, the planet Uranus. The new image features dramatic rings as well as bright features in the planet’s atmosphere. The Webb data demonstrate the observatory’s unprecedented sensitivity by revealing the faintest dusty rings, which have only ever been imaged by two other facilities: the Voyager 2 spacecraft as it flew past the planet in 1986, and the Keck Observatory with advanced adaptive optics.
The seventh planet from the Sun, Uranus is unique: it rotates on its side, at a nearly 90-degree angle from the plane of its orbit. This causes extreme seasons since the planet’s poles experience many years of constant sunlight followed by an equal number of years of complete darkness. (Uranus takes 84 years to orbit the Sun.) Currently, it is late spring at the northern pole, which is visible here; Uranus’s northern summer will be in 2028. In contrast, when Voyager 2 visited Uranus it was summer at the south pole. The south pole is now on the ‘dark side’ of the planet, out of view and facing the darkness of space.
This zoomed-in image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam) on 6 February 2023, reveals stunning views of the planet’s rings. The planet displays a blue hue in this representative-colour image, made by combining data from two filters (F140M, F300M) at 1.4 and 3.0 microns, shown here as blue and orange, respectively.
On the right side of the planet is an area of brightening at the pole facing the Sun, known as a polar cap. This polar cap is unique to Uranus because it is the only planet in the Solar System that is tilted on its side, which causes its extreme seasons. A new aspect of the polar cap revealed by Webb is a subtle brightening near the Uranian north pole.
At the edge of the polar cap lies a bright cloud and a few fainter extended features can be seen just beyond the cap’s edge; a second very bright cloud is seen at the planet’s left limb. Such clouds are typical for Uranus at infrared wavelengths, and are likely connected to storm activity.
Credit:
NASA, ESA, CSA, STScI, J. DePasquale (STScI)
This annotated, zoomed-in image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam) on 6 February 2023, reveals stunning views of the planet’s rings, as well as clouds and the polar cap.
On the right side of the planet is an area of brightening at the pole facing the Sun, known as a polar cap. This polar cap is unique to Uranus because it is the only planet in the Solar System that is tilted on its side, which causes its extreme seasons. A new aspect of the polar cap revealed by Webb is a subtle brightening near the Uranian north pole.
At the edge of the polar cap lies a bright cloud and a few fainter extended features can be seen just beyond the cap’s edge; a second very bright cloud is seen at the planet’s left limb. Such clouds are typical for Uranus at infrared wavelengths, and are likely connected to storm activity.
The planet displays a blue hue in this representative-colour image, made by combining data from two filters (F140M, F300M) at 1.4 and 3.0 microns, which are assigned to blue and orange, respectively.
Credit:
NASA, ESA, CSA, STScI, J. DePasquale (STScI)
This infrared image from Webb’s Near-Infrared Camera (NIRCam) combines data from two filters at 1.4 and 3.0 microns, shown here in blue and orange, respectively. The planet displays a blue hue in the resulting representative-colour image.
When Voyager 2 looked at Uranus, its camera saw an almost featureless blue-green ball at visible wavelengths. At infrared wavelengths, and with Webb’s greater sensitivity, we see more detail, showing how dynamic the atmosphere of Uranus really is.
On the right side of the planet is an area of brightening at the pole facing the Sun, known as a polar cap. This polar cap is unique to Uranus — it seems to appear when the pole enters direct sunlight in the summer and vanishes in the autumn; these Webb data will help scientists understand the currently mysterious mechanism behind this feature. Webb has revealed a surprising aspect of the polar cap: a subtle enhanced brightening at the centre of the cap. The sensitivity of Webb’s NIRCam and the longer wavelengths it can see may explain why we can see this enhanced polar feature of Uranus when it has not been seen with other powerful telescopes like the NASA/ESA Hubble Space Telescope and the Keck Observatory.
At the edge of the polar cap lies a bright cloud and a few fainter extended features can be seen just beyond the cap’s edge; a second very bright cloud is seen at the planet’s left limb. Such clouds are typical for Uranus at infrared wavelengths, and are likely connected to storm activity.
This planet is characterised as an ice giant because of the chemical make-up of its interior. Most of its mass is thought to be a hot, dense fluid of ‘icy’ materials — water, methane and ammonia — above a small rocky core.
Uranus has 13 known rings and 11 of them are visible in this Webb image. Some of these rings are so bright as seen by Webb that when they are close together, they appear to merge into a larger ring. Nine are classed as the main rings of the planet, and two are the fainter dusty rings (such as the diffuse zeta ring closest to the planet) that weren’t discovered until the 1986 flyby by Voyager 2. Scientists expect that future Webb images of Uranus will reveal the two faint outer rings that were discovered with Hubble during the 2007 ring-plane crossing.
This wider view of the Uranian system with Webb’s NIRCam instrument features the planet Uranus as well as six of its 27 known moons (most of which are too small and faint to be seen in this short exposure). A handful of background objects, including many galaxies, are also seen.
Credit:
NASA, ESA, CSA, STScI, J. DePasquale (STScI)
This wider view of the Uranian system with Webb’s NIRCam instrument features the planet Uranus as well as six of its 27 known moons (most of which are too small and faint to be seen in this short exposure). A handful of background objects, including many galaxies, are also seen.
Credit:
NASA, ESA, CSA, STScI, J. DePasquale (STScI)
Webb also captured many of Uranus’s 27 known moons (most of which are too small and faint to be seen here); the six brightest are identified in the wide-view image. This was only a short (12-minute) exposure image of Uranus with just two filters. It is just the tip of the iceberg of what Webb can do when observing this mysterious planet. Additional studies of Uranus are happening now, and more are planned in Webb’s first year of science operations.
Hubble monitors changing weather and seasons on Jupiter and Uranus
Ever since its launch in 1990, the NASA/ESA Hubble Space Telescope has been an interplanetary weather observer, keeping an eye on the ever-changing atmospheres of the largely gaseous outer planets. And it’s an unblinking eye that allows Hubble’s sharpness and sensitivity to monitor a kaleidoscope of complex activities over time. Today new images are shared of Jupiter and Uranus.
Hubble monitors changing weather and seasons on Jupiter and Uranus. Note: The planets do not appear in this image to scale. Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
The outer planets beyond Mars do not have solid surfaces to affect weather as on Earth. And sunlight is much less able to drive atmospheric circulation. Nevertheless, these are ever-changing worlds. And Hubble – in its role as interplanetary meteorologist – is keeping track, as it does every year. Jupiter’s weather is driven from the inside out, as more heat percolates up from its interior than it receives from the Sun. This heat indirectly drives colour-change cycles in the clouds, like the cycle that’s currently highlighting a system of alternating cyclones and anticyclones. Uranus has seasons that pass by at a snail’s pace because it takes 84 years to complete one orbit about the Sun. But those seasons are extreme, because Uranus is tipped on its side. As summer approaches in the northern hemisphere, Hubble sees a growing polar cap of high-altitude photochemical haze that looks similar to the smog over cities on Earth.
Inaugurated in 2014, the Hubble Space Telescope’s Outer Planet Atmospheres Legacy (OPAL) programme has been providing us with yearly views of the giant planets. Here are some recent images.
Jupiter
Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
The forecast for Jupiter is for stormy weather at low northern latitudes. A prominent string of alternating storms is visible, forming a ‘vortex street’ as some planetary astronomers call it. This is a wave pattern of nested cyclones and anticyclones, locked together like the alternating gears of a machine moving clockwise and counterclockwise. If the storms get close enough to each other and merge together, they could build an even larger storm, potentially rivalling the current size of the Great Red Spot. The staggered pattern of cyclones and anticyclones prevents individual storms from merging. Activity is also seen interior to these storms; in the 1990s Hubble didn’t see any cyclones or anticyclones with built-in thunderstorms, but these storms have sprung up in the last decade. Strong colour differences indicate that Hubble is seeing different cloud heights and depths as well.
The orange moon Io photobombs this view of Jupiter’s multicoloured cloud tops, casting a shadow toward the planet’s western limb. Hubble’s resolution is so sharp that it can see Io’s mottled-orange appearance, the result of its numerous active volcanoes. These volcanoes were first discovered when the Voyager 1 spacecraft flew by in 1979. The moon’s molten interior is overlaid by a thin crust through which the volcanoes eject material. Sulphur takes on various hues at different temperatures, which is why Io’s surface is so colourful. This image was taken on 12 November 2022.
Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
Jupiter’s legendary Great Red Spot takes centre stage in this view. Though this vortex is big enough to swallow Earth, it has actually shrunk to the smallest size it has ever been according to observation records dating back 150 years. Jupiter’s icy moon Ganymede can be seen transiting the giant planet at lower right. Slightly larger than the planet Mercury, Ganymede is the largest moon in the Solar System. It is a cratered world and has a mainly water-ice surface with apparent glacial flows driven by internal heat. This image was taken on 6 January 2023.
Jupiter and its large ocean-bearing moons (Ganymede, Callisto and Europa) are the target of ESA’s Jupiter Icy Moons Explorer (Juice). Preparations are currently underway to ready Juice for liftoff from Europe’s Spaceport in French Guiana on 13 April 2023 [1].
Jupiter (November 2022 and January 2023). Credit:NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
Credit:NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
Uranus
Planetary oddball Uranus rolls around the Sun on its side as it follows its 84-year orbit, rather than spinning in a more ’vertical’ position as Earth does. Its weirdly tilted ‘horizontal’ rotation axis is angled just eight degrees off the plane of the planet’s orbit. One recent theory proposes that Uranus once had a massive moon that gravitationally destabilised it and then crashed into it. Other possibilities include giant impacts during the formation of the planets, or even giant planets exerting resonant torques on each other over time. The consequences of Uranus’s tilt are that for stretches of time lasting up to 42 years, parts of one hemisphere are completely without sunlight. When the Voyager 2 spacecraft visited during the 1980s, the planet’s south pole was pointed almost directly at the Sun. Hubble’s latest view shows the northern pole now tipping toward the Sun.
Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
This is a Hubble view of Uranus taken in 2014, seven years after the northern spring equinox when the Sun was shining directly over the planet’s equator, and shows one of the first images from the OPAL programme. Multiple storms with methane ice-crystal clouds appear at mid-northern latitudes above the planet’s cyan-tinted lower atmosphere. Hubble imaged the ring system edge-on in 2007, but the rings are seen starting to open up seven years later in this view. At this time, the planet had multiple small storms and even some faint cloud bands.
As seen in 2022, Uranus’s north pole shows a thickened photochemical haze that looks similar to the smog over cities. Several little storms can be seen near the edge of the polar haze boundary. Hubble has been tracking the size and brightness of the north polar cap and it continues to get brighter year after year. Astronomers are disentangling multiple effects – from atmospheric circulation, particle properties, and chemical processes — that control how the atmospheric polar cap changes with the seasons. At the Uranian equinox in 2007, neither pole was particularly bright. As the northern summer solstice approaches in 2028 the cap may grow brighter still, and will be aimed directly toward Earth, allowing good views of the rings and the north pole; the ring system will then appear face-on. This image was taken on 10 November 2022.
Uranus (November 2014 and November 2022). Credit:
NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
Uranus (November 2014 and November 2022) compass image. Credit:
NASA, ESA, STScI, A. Simon (NASA-GSFC), M. H. Wong (UC Berkeley), J. DePasquale (STScI)
Notes
[1] Ganymede is the main target of ESA’s Jupiter Icy Moons Explorer (Juice). As humanity’s next bold mission to the outer Solar System, Juice will complete numerous flybys around Ganymede, and eventually enter orbit around the moon. The mission will explore various key topics: Ganymede’s mysterious magnetic field, its hidden ocean, its complex core, its ice content and shell, its interactions with its local environment and that of Jupiter, its past and present activity, and whether or not the moon could be a habitable environment.
More information
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
The HST observations featured in this release include those from program 16790, 13937 , and 16995 (A. Simon).
Press release from ESA Hubble about the telescope observing the changing weather and seasons on Jupiter and Uranus.
Webb spots swirling, gritty clouds on VHS 1256 b, a remote planet
Researchers observing with the NASA/ESA/CSA James Webb Space Telescope have pinpointed silicate cloud features in a distant planet’s atmosphere. The atmosphere is constantly rising, mixing, and moving during its 22-hour day, bringing hotter material up and pushing colder material down. The resulting brightness changes are so dramatic that it is the most variable planetary-mass object known to date. The science team also made extraordinarily clear detections of water, methane and carbon monoxide with Webb’s data, and found evidence of carbon dioxide. This is the largest number of molecules ever identified all at once on a planet outside our Solar System.
This illustration conceptualises the swirling clouds identified by the James Webb Space Telescope in the atmosphere of the exoplanet VHS 1256 b. The planet is about 40 light-years away and orbits two stars that are locked in their own tight rotation. Its clouds, which are filled with silicate dust, are constantly rising, mixing, and moving during its 22-hour day. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
Catalogued as VHS 1256 b, the planet is about 40 light-years away and orbits not one, but two stars over a 10 000-year period.
“VHS 1256 b is about four times farther from its stars than Pluto is from our Sun, which makes it a great target for Webb,” said science team lead Brittany Miles of the University of Arizona. “That means the planet’s light is not mixed with light from its stars.” Higher up in its atmosphere, where the silicate clouds are churning, temperatures reach a scorching 830 degrees Celsius.
Within those clouds, Webb detected both larger and smaller silicate dust grains, which are shown on a spectrum.
“The finer silicate grains in its atmosphere may be more like tiny particles in smoke,” noted co-author Beth Biller of the University of Edinburgh in the United Kingdom. “The larger grains might be more like very hot, very small sand particles.”
VHS 1256 b has low gravity compared to more massive brown dwarfs [1], which means that its silicate clouds can appear and remain higher in its atmosphere where Webb can detect them. Another reason its skies are so turbulent is the planet’s age. In astronomical terms, it’s quite young. Only 150 million years have passed since it formed — and it will continue to change and cool over billions of years.
A research team led by Brittany Miles of the University of Arizona used two instruments known as spectrographs aboard the James Webb Space Telescope, one on its Near Infrared Spectrograph (NIRSpec) and another on its Mid-Infrared Instrument (MIRI), to observe a vast section of near- to mid-infrared light emitted by the planet VHS 1256 b. They plotted the light on the spectrum, identifying signatures of silicate clouds, water, methane and carbon monoxide. They also found evidence of carbon dioxide. Credit: NASA, ESA, CSA, J. Olmsted (STScI), B. Miles (University of Arizona), S. Hinkley (University of Exeter), B. Biller (University of Edinburgh), A. Skemer (University of California, Santa Cruz)
In many ways, the team considers these findings to be the first ‘coins’ pulled out of a spectrum that researchers view as a treasure chest of data. In many ways, they’ve only begun identifying its contents.
“We’ve identified silicates, but a better understanding of which grain sizes and shapes match specific types of clouds is going to take a lot of additional work,” Miles said. “This is not the final word on this planet — it is the beginning of a large-scale modelling effort to fit Webb’s complex data.”
Although all of the features the team observed have been spotted on other planets elsewhere in the Milky Way by other telescopes, other research teams typically identified only one at a time.
“No other telescope has identified so many features at once for a single target,” said co-author Andrew Skemer of the University of California, Santa Cruz. “We’re seeing a lot of molecules in a single spectrum from Webb that detail the planet’s dynamic cloud and weather systems.”
The team came to these conclusions by analysing data known as spectra gathered by two instruments aboard Webb, the Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI). Since the planet orbits at such a great distance from its stars, the researchers were able to observe it directly, rather than using the transit technique [2] or a coronagraph [3] to take this data.
There will be plenty more to learn about VHS 1256 b in the months and years to come as this team — and others — continue to sift through Webb’s high-resolution infrared data. “There’s a huge return on a very modest amount of telescope time,” Biller added. “With only a few hours of observations, we have what feels like unending potential for additional discoveries.”
What might become of this planet billions of years from now? Since it’s so far from its stars, it will become colder over time, and its skies may transition from cloudy to clear.
The researchers observed VHS 1256 b as part of Webb’s Early Release Science program, which is designed to help transform the astronomical community’s ability to characterise planets and the discs from which they form.
The team’s paper, entitled “The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b,” will be published in The Astrophysical Journal Letters on 22 March.
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.”
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.
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.
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)
Webb Reveals an Exoplanet Atmosphere as Never Seen Before
The NASA/ESA/CSA James Webb Space Telescope just scored another first: a molecular and chemical profile of a distant world’s skies.
This image shows an artist’s impression of the planet WASP-39 b and its star. The planet has a fuzzy orange-blue atmosphere with hints of longitudinal cloud bands below. The left quarter of the planet (the side facing the star) is lit, while the rest is in shadow. The star is bright yellowish-white, with no clear features. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
The NASA/ESA/CSA James Webb Space Telescope just scored another first: a molecular and chemical portrait of a distant world’s skies. While Webb and other space telescopes, including the NASA/ESA Hubble Space Telescope, have previously revealed isolated ingredients of this heated planet’s atmosphere, the new readings provide a full menu of atoms, molecules, and even signs of active chemistry and clouds. The latest data also give a hint of how these clouds might look up close: broken up rather than as a single, uniform blanket over the planet.
The telescope’s array of highly sensitive instruments was trained on the atmosphere of WASP-39 b, a “hot Saturn” (a planet about as massive as Saturn but in an orbit tighter than Mercury) orbiting a star some 700 light-years away. This Saturn-sized exoplanet was one of the first examined by the NASA/ESA/CSA James Webb Space Telescope when it began regular science operations. The results have excited the exoplanet science community. Webb’s exquisitely sensitive instruments have provided a profile of WASP-39 b’s atmospheric constituents and identified a plethora of contents, including water, sulphur dioxide, carbon monoxide, sodium and potassium.
Image Description: Graphic titled “Hot Gas Giant Exoplanet WASP-39 b Atmosphere Composition.” The graphic includes four graphs—transmission spectra—arranged in a 2 by 2 grid with an illustration of the planet and its star in the background. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
This graph displays data from Webb’s NIRISS instrument, showing fingerprints of potassium (K), water (H2O), and carbon monoxide (CO). Credit: NASA, ESA, CSA, J. Olmsted (STScI)
This graph displays data from Webb’s NIRCam instrument, showing a prominent water signature. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
This graph displays data from Webb’s NIRSpec instrument, indicating signatures of water, sulfur dioxide (SO2), carbon dioxide (CO2), and carbon monoxide (CO). Credit: NASA, ESA, CSA, J. Olmsted (STScI)
This graph displays data from Webb’s NIRSpec instrument, indicating signatures of potassium (K), water (H2O), carbon monoxide (CO), sulfur dioxide (SO2), carbon dioxide (CO2), and sodium (Na). Credit: NASA, ESA, CSA, J. Olmsted (STScI)
The findings bode well for the capability of Webb’s instruments to conduct the broad range of investigations of exoplanets — planets around other stars — hoped for by the science community. That includes probing the atmospheres of smaller, rocky planets like those in the TRAPPIST-1 system.
“We observed the exoplanet with several instruments that together cover a broad swath of the infrared spectrum and a panoply of chemical fingerprints inaccessible until JWST,” said Natalie Batalha, an astronomer at the University of California, Santa Cruz, who contributed to and helped coordinate the new research. “Data like these are a game changer.”
The suite of discoveries is detailed in a set of five new scientific papers, three of which are in press and two of which are under review. Among the unprecedented revelations is the first detection in an exoplanet atmosphere of sulphur dioxide, a molecule produced from chemical reactions triggered by high-energy light from the planet’s parent star. On Earth, the protective ozone layer in the upper atmosphere is created in a similar way.
“This is the first time we have seen concrete evidence of photochemistry — chemical reactions initiated by energetic stellar light — on exoplanets,” said Shang-Min Tsai, a researcher at the University of Oxford in the United Kingdom and lead author of the paper explaining the origin of sulphur dioxide in WASP-39 b’s atmosphere. “I see this as a really promising outlook for advancing our understanding of exoplanet atmospheres with [this mission].”
This led to another first: scientists applying computer models of photochemistry to data that require such physics to be fully explained. The resulting improvements in modelling will help build the technological know-how needed to interpret potential signs of habitability in the future.
“Planets are sculpted and transformed by orbiting within the radiation bath of the host star,” Batalha said. “On Earth, those transformations allow life to thrive.”
The planet’s proximity to its host star — eight times closer than Mercury is to our Sun — also makes it a laboratory for studying the effects of radiation from host stars on exoplanets. Better knowledge of the star-planet connection should bring a deeper understanding of how these processes affect the diversity of planets observed in the galaxy.
Other atmospheric constituents detected by the Webb telescope include sodium (Na), potassium (K), and water vapour (H2O), confirming previous space- and ground-based telescope observations as well as finding additional fingerprints of water, at these longer wavelengths, that haven’t been seen before.
Webb also saw carbon dioxide (CO2) at higher resolution, providing twice as much data as reported from its previous observations. Meanwhile, carbon monoxide (CO) was detected, but obvious signatures of both methane (CH4) and hydrogen sulphide (H2S) were absent from the Webb data. If present, these molecules occur at very low levels.
To capture this broad spectrum of WASP-39 b’s atmosphere, an international team numbering in the hundreds independently analysed data from four of the Webb telescope’s finely calibrated instrument modes.
“We had predicted what [the telescope] would show us, but it was more precise, more diverse and more beautiful than I think I actually believed it would be,” said Hannah Wakeford, an astrophysicist at the University of Bristol in the United Kingdom who investigates exoplanet atmospheres.
Having such a complete roster of chemical ingredients in an exoplanet atmosphere also gives scientists a glimpse of the abundance of different elements in relation to each other, such as the carbon-to-oxygen or potassium-to-oxygen ratios. That in turn provides insight into how this planet — and perhaps others — formed out of the disc of gas and dust surrounding the parent star in its younger years.
WASP-39 b’s chemical inventory suggests a history of smashups and mergers of smaller bodies called planetesimals to create an eventual goliath of a planet.
“The abundance of sulphur [relative to] hydrogen indicated that the planet presumably experienced significant accretion of planetesimals that can deliver [these ingredients] to the atmosphere,” said Kazumasa Ohno, a UC Santa Cruz exoplanet researcher who worked on Webb data. “The data also indicates that the oxygen is a lot more abundant than the carbon in the atmosphere. This potentially indicates that WASP-39 b originally formed far away from the central star.
By precisely revealing the details of an exoplanet atmosphere, the Webb telescope’s instruments performed well beyond scientists’ expectations — and promise a new phase of exploration of the broad variety of exoplanets in the galaxy.
“We are going to be able to see the big picture of exoplanet atmospheres,” said Laura Flagg, a researcher at Cornell University and a member of the international team. “It is incredibly exciting to know that everything is going to be rewritten. That is one of the best parts of being a scientist.”
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Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.
Webb is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).
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.
