SPACE NEWS
Uranus aurora discovery offers clues to habitable icy worlds
University of Leicester astronomers confirm the existence of an infrared (IR) aurora on Uranus
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AN ARTISTIC REPRESENTATION OF HOW THE NORTHERN INFRARED AURORA WOULD HAVE LOOKED LIKE IN 2006 (MARKED IN RED). THE DARKER RED LOCATIONS INDICATE CONFIRMED AURORA LOCATIONS, WITH FAINTER RED USED TO MARK POSSIBLE AURORA LOCATIONS. CREDIT TO NASA, ESA AND M. SHOWALTER (SETI INSTITUTE) FOR THE BACKGROUND IMAGE OF URANUS, AS WAS OBSERVED BY THE HUBBLE SPACE TELESCOPE (IN THE VISIBLE SPECTRUM) IN AUGUST 2005.
view moreCREDIT: CREDIT TO NASA, ESA AND M. SHOWALTER (SETI INSTITUTE) FOR THE BACKGROUND IMAGE OF URANUS, AS WAS OBSERVED BY THE HUBBLE SPACE TELESCOPE (IN THE VISIBLE SPECTRUM) IN AUGUST 2005.
The presence of an infrared aurora on the cold, outer planet of Uranus has been confirmed for the first time by University of Leicester astronomers.
The discovery could shed light on the mysteries behind the magnetic fields of the planets of our solar system, and even on whether distant worlds might support life.
The team of scientists, supported by the Science and Technology Facilities Council (STFC), have obtained the first measurements of the infrared (IR) aurora at Uranus since investigations began in 1992. While the ultraviolet (UV) aurorae of Uranus has been observed since 1986, no confirmation of the IR aurora had been observed until now. The scientists’ conclusions have been published in the journal Nature Astronomy.
The ice giants Uranus and Neptune are unusual planets in our solar system as their magnetic fields are misaligned with the axes in which they spin. While scientists have yet to find an explanation for this, clues may lie in Uranus’s aurora.
Aurorae are caused by highly energetic charged particles, which are funnelled down and collide with a planet's atmosphere via the planet's magnetic field lines. On Earth, the most famous result of this process are the spectacles of the Northern and Southern Lights. At planets such as Uranus, where the atmosphere is predominately a mix of hydrogen and helium, this aurora will emit light outside of the visible spectrum and in wavelengths such as the infrared (IR).
The team used infrared auroral measurements taken by analysing specific wavelengths of light emitted from the planet, using the Keck II telescope. From this, they can analyse the light (known as emission lines) from these planets, similar to a barcode. In the infrared spectrum, the lines emitted by a charged particle known as H3+ will vary in brightness depending on how hot or cold the particle is and how dense this layer of the atmosphere is. Hence, the lines act like a thermometer into the planet.
Their observations revealed distinct increases in H3+ density in Uranus’s atmosphere with little change in temperature, consistent with ionisation caused by the presence of an infrared aurora. Not only does this help us better understand the magnetic fields of the outer planets of our own solar system, but it may also help in identifying other planets that are suitable of supporting life.
Lead author Emma Thomas, a PhD student in the University of Leicester School of Physics and Astronomy, said: “The temperature of all the gas giant planets, including Uranus, are hundreds of degrees Kelvin/Celsius above what models predict if only warmed by the sun, leaving us with the big question of how these planets are so much hotter than expected? One theory suggests the energetic aurora is the cause of this, which generates and pushes heat from the aurora down towards the magnetic equator.
“A majority of exoplanets discovered so far fall in the sub-Neptune category, and hence are physically similar to Neptune and Uranus in size. This may also mean similar magnetic and atmospheric characteristics too. By analysing Uranus's aurora which directly connects to both the planet's magnetic field and atmosphere, we can make predictions about the atmospheres and magnetic fields of these worlds and hence their suitability for life.
"This paper is the culmination of 30 years of auroral study at Uranus, which has finally revealed the infrared aurora and begun a new age of aurora investigations at the planet. Our results will go on to broaden our knowledge of ice giant auroras and strengthen our understanding of planetary magnetic fields in our solar system, at exoplanets and even our own planet."
The results may also give scientists an insight into a rare phenomenon on Earth, in which the north and south pole switch hemisphere locations known as geomagnetic reversal.
Emma adds: “We don't have many studies on this phenomena and hence do not know what effects this will have on systems that rely on Earth's magnetic field such as satellites, communications and navigation. However, this process occurs every day at Uranus due to the unique misalignment of the rotational and magnetic axes. Continued study of Uranus's aurora will provide data on what we can expect when Earth exhibits a future pole reversal and what that will mean for its magnetic field.”
Averaged emission spectrum between 3.4 and 4.0μm, with annotated positions of valuable H3+ emission lines (known as Q lines) found at specific wavelength locations, the brightness of each line is determined by both temperature and density of the H3+ particles in a planet's atmosphere
Measured infrared brightness from the upper atmosphere of Uranus over a 6-hour period, areas highlighted with a black border and no hash or dots are locations of enhanced emission (aurora). Hashed areas means possible aurora though the signal is too weak to confirm and dotted areas means no aurora in these points.
Measured infrared brightness from the upper atmosphere of Uranus combined with rings of magnetic field lines which occur as the planet rotations (which produces the oval shape we see in most aurora). These rings are called shells and we expect the majority of auroral signal to occur between the dashed and dotted lines (as seen in 1986), which a portion of our results do.
Movie of the telescope imager [VIDEO] |
Condensed movie of the telescope imager (on the 5th September 2006) as it focused on Uranus, with moons Titania, Miranda, Umbriel and Oberon visible. There is a double exposure of all objects in the movie, which is an effect of subtracting images to minimise the effect of Earth's atmosphere as we look up into the sky. We also see possible galaxies and stars in this movie!
CREDIT
Source: University of Leicester
JOURNAL
Nature Astronomy
ARTICLE TITLE
Detection of the infrared aurora at Uranus with Keck-NIRSPEC
ARTICLE PUBLICATION DATE
23-Oct-2023
New research sheds light on early galaxy formation
Researchers have created a model of the early universe that better corresponds to observations
Peer-Reviewed PublicationIMAGE:
RESEARCHERS HAVE DEVELOPED A NEW COMPUTER SIMULATION OF THE EARLY UNIVERSE THAT CLOSELY ALIGNS WITH OBSERVATIONS MADE BY THE JAMES WEBB SPACE TELESCOPE (JWST).
view moreCREDIT: NASA, ESA AND S. BECKWITH (STSCI) AND THE HUDF TEAM
Researchers have developed a new computer simulation of the early universe that closely aligns with observations made by the James Webb Space Telescope (JWST).
Initial JWST observations hinted that something may be amiss in our understanding of early galaxy formation. The first galaxies studied by JWST appeared to be brighter and more massive than theoretical expectations.
The findings, published in The Open Journal of Astrophysics, by researchers at Maynooth University, Ireland, with collaborators from US based Georgia Institute of Technology, show that observations made by JWST do not contradict theoretical expectations. The so-called ‘Renaissance simulations’ used by the team are a series of highly sophisticated computer simulations of galaxy formation in the early Universe.
The simulation can resolve very small dark matter clumps and can track these clumps as they coagulate and build up as dark matter halos which then host the types of galaxies that we observe. The simulations can also model the formation of the very first stars that form in our Universe - Population III stars - which are expected to be much more massive and brighter than present-day stars.
The simulations used by the MU team showed that these galaxies are consistent with the models that dictate the physics of the cosmological simulations.
Speaking about the findings, lead author Joe M. McCaffrey, PhD student at Maynooth’s Department of Theoretical Physics, said: “We have shown that these simulations are crucial in understanding our origin in the Universe. In future, we hope to use these same simulations to investigate the growth of massive black holes in the early Universe.”
Commenting on the research and future direction of his research team, Dr John Regan, Associate Professor at Maynooth’s Department of Theoretical Physics, said: “The JWST has revolutionised our understanding of the early Universe. Using its incredible power we are now able to glimpse the Universe as it was only a few hundred million years after the Big Bang - a time when the Universe was less than 1% of its current age. What JWST is showing us is that the young Universe was bursting with massive star formation and an evolving population of massive black holes. The next steps will be to use these observations to guide our theoretical models - something which up until very recently was simply impossible.”
JOURNAL
The Open Journal of Astrophysics
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
No Tension: JWST Galaxies at z>10 Consistent with Cosmological Simulations
Mystery of the Martian core solved
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ANALYSIS OF MARTIAN SEISMIC DATA RECORDED BY THE INSIGHT MISSION IN COMBINATION WITH FIRST-PRINCIPLES SIMULATIONS OF THE SEISMIC PROPERTIES OF LIQUID METAL ALLOYS HAVE REVEALED THAT MARS’S LIQUID IRON CORE IS SURROUNDED BY A 150-KM THICK MOLTEN SILICATE LAYER, AS A CONSEQUENCE OF WHICH ITS CORE IS SMALLER THAN PREVIOUSLY PROPOSED. THE DECREASE IN CORE RADIUS IMPLIES A HIGHER DENSITY THAN ESTIMATED EARLIER AND IS COMPATIBLE WITH A METAL CORE CONSISTING OF 9–15 WT% OF LIGHT ELEMENTS, CHIEFLY S, C, O, AND H.
view moreCREDIT: ©2023 CREATIVE COMMONS ATTRIBUTION-NONCOMMERCIAL-SHAREALIKE 4.0 INTERNATIONAL (CC BY-NC-SA 4.0) - THIBAUT ROGER - NCCR PLANETS - ETH ZURICH.
For four years, NASA’s InSight lander recorded tremors on Mars with its seismometer. Researchers at ETH Zurich collected and analysed the data transmitted to Earth to determine the planet’s internal structure. “Although the mission ended in December 2022, we’ve now discovered something very interesting,” says Amir Khan, a Senior Scientist in the Department of Earth Sciences at ETH Zurich.
An analysis of recorded marsquakes, combined with computer simulations, paint a new picture of the planet’s interior. Sandwiched between Mars’s liquid iron alloy core and its solid silicate mantle lies a layer of liquid silicate (magma) about 150 kilometres thick. “Earth doesn’t have a completely molten silicate layer like that,” Khan says.
This finding, now published in the scientific journal Nature alongside a study led by Henri Samuel, Institut de Physique de Globe de Paris, that reaches a similar conclusion using complimentary methods, also provides new information on the size and composition of Mars’ core, resolving a mystery that researchers have until now been unable to explain.
An analysis of the initially observed marsquakes had shown that the average density of the Martian core had to be significantly lower than that of pure liquid iron. The Earth’s core, for example, consists of about 90 percent iron by weight. Light elements such as sulphur, carbon, oxygen, and hydrogen make up a combined total of around 10 percent by weight. Initial estimates of the density of the Martian core showed that it is comprised of a much larger share of light elements – around 20 percent by weight. “This represents a very large complement of light elements, bordering on the impossible. We have been wondering about this result ever since,” says Dongyang Huang, a postdoctoral researcher in the Department of Earth Sciences at ETH Zurich.
Fewer light elements
The new observations show that the radius of the Martian core has decreased from the initially determined range of 1,800–1,850 kilometres to somewhere in the range of 1,650– 1,700 kilometres, which is about 50 percent of the radius of Mars. If the Martian core is smaller than previously thought but has the same mass, it follows that its density is greater and that it, therefore, contains fewer light elements. According to the new calculations, the proportion of light elements dropped to between 9 and 14 percent by weight. “This means that the average density of the Martian core is still somewhat low, but no longer inexplicable in the context of typical planet formation scenarios,” says Paolo Sossi, Assistant Professor in the Department of Earth Sciences at ETH Zurich and member of the National Centres of Competence in Research (NCCRs) PlanetS. The fact that the Martian core contains a significant amount of light elements indicates that it must have formed very early, possibly when the Sun was still surrounded by the nebula gas from which light elements could have accumulated in the Martian core.
The initial calculations were based on tremors that had occurred in close proximity to the InSight lander. However, in August and September 2021, the seismometer registered two quakes on the opposite side of Mars. One of them was caused by a meteorite impact. “These quakes produced seismic waves that traversed the core,” explains Cecilia Duran, a doctoral student in the Department of Earth Sciences at ETH Zurich. “This allowed us to illuminate the core.” In the case of the earlier marsquakes, by contrast, the waves were reflected at the core-mantle boundary, providing no information about the deepest interior of the Red Planet. As a result of these new observations, the researchers have now been able to determine the density and seismic wave speed of the fluid core up to a depth of about 1,000 kilometres.
Supercomputer simulations
To infer the composition of the material from such profiles, researchers usually compare the data with that of synthetic iron alloys containing different proportions of light elements (S, C, O, and H). In the lab, these alloys are exposed to high temperatures and pressures equivalent to those found in Mars’s interior, allowing researchers to measure density and seismic wave speed directly. At the moment, however, most experiments are conducted at conditions prevailing in the Earth’s interior and are, therefore, not immediately applicable to Mars. Consequently, the ETH Zurich researchers resorted to a different method. They computed the properties of a wide variety of alloys using quantum-mechanical calculations, which they carried out at the Swiss National Supercomputing Centre (CSCS) in Lugano, Switzerland.
When the researchers compared the calculated profiles with their measurements based on the InSight seismic data, they encountered a problem. It turned out that no iron-light element alloys simultaneously matched the data at both the top and centre of the Martian core. At the core-mantle boundary, for example, the iron alloy would have had to contain much more carbon than in the core’s interior. “It took us a while to realise that the region we had previously considered to be the outer liquid iron core wasn’t the core after all, but the deepest part of the mantle,” explains Huang. In support of this, the researchers also found that the density and seismic wave speed measured and computed in the outermost 150 kilometres of the core were consistent with those of liquid silicates – the same material, in solid form, of which the Martian mantle is composed.
Further analysis of earlier marsquakes and additional computer simulations confirmed this result. It is only regrettable that dusty solar panels and the resulting lack of power made it impossible for the InSight lander to provide additional data that could have shed more light on the composition and structure of Mars’s interior. “Yet, InSight was a very successful mission that provided us with a lot of new data and insights that will be analysed for years to come,” Khan says.
JOURNAL
Nature
ARTICLE TITLE
Evidence for a liquid silicate layer atop the Martian core
ARTICLE PUBLICATION DATE
26-Oct-2023
Scientists discover molten layer covering Martian core
New NASA InSight research reveals a liquid silicate ‘blanket’ wrapped around Mars’ core, leading to new clues about the planet’s evolutionary history and the loss of its potential to sustain life
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AN ARTIST'S DEPICTION OF THE LIQUID SILICATE LAYER WRAPPED AROUND THE MARTIAN CORE.
view moreCREDIT: COPYRIGHT IPGP-CNES.
NASA’s InSight mission to Mars helped scientists map out Mars’ internal structure, including the size and composition of its core, and provided general hints about its tumultuous formation.
But findings from a new paper published in the journal Nature could lead to reanalysis of that data. An international team of researchers discovered the presence of a molten silicate layer overlying Mars’ metallic core—providing new insights into how Mars formed, evolved and became the barren planet it is today.
Published on October 25, 2023, the team’s paper details the use of seismic data to locate and identify a thin layer of molten silicates (rock-forming minerals that make up the crust and mantle of Mars and Earth) lying between the Martian mantle and core. With the discovery of this molten layer, the researchers determined that Mars’ core is both denser and smaller than previous estimates, a conclusion that better aligns with other geophysical data and analysis of Martian meteorites.
Vedran Lekic, a professor of geology at the University of Maryland and co-author of the paper, compared the molten layer to a ‘heating blanket’ covering the Martian core.
“The blanket not only insulates the heat coming from the core and prevents the core from cooling, but also concentrates radioactive elements whose decay generates heat” Lekic said. “And when that happens, the core is likely to be unable to produce the convective motions that would create a magnetic field—which can explain why Mars currently doesn’t have an active magnetic field around it.”
Without a functional protective magnetic field around itself, a terrestrial planet such as Mars would be extremely vulnerable to harsh solar winds and lose all the water on its surface, making it incapable of sustaining life. Lekic added that this difference between Earth and Mars could be attributed to differences in internal structure and the different planetary evolution paths the two planets took.
“The thermal blanketing of Mars’ metallic core by the liquid layer at the base of the mantle implies that external sources are necessary to generate the magnetic field recorded in the Martian crust during the first 500 to 800 million years of its evolution,” said the paper’s lead author Henri Samuel, a scientist with the French National Center for Scientific Research. “These sources could be energetic impacts or core motion generated by gravitational interactions with ancient satellites which have since then disappeared.”
The team’s conclusions support theories that Mars was at one time a molten ocean of magma that later crystallized to produce a layer of silicate melt enriched in iron and radioactive elements at the base of the Martian mantle. The heat emanating from the radioactive elements would then have dramatically altered the thermal evolution and cooling history of the red planet.
“These layers, if widespread, can have pretty big consequences for the rest of the planet,” Lekic said. “Their existence can help tell us whether magnetic fields can be generated and maintained, how planets cool over time, and also how the dynamics of their interiors change over time.”
NASA’s InSight mission officially ended in December 2022 after more than four years of collecting data on Mars, but the analysis of the observations continues. Samuel, Lekic and their co-authors are among the latest researchers to reexamine prior models of Mars using seismology to confirm the planet’s structure and turbulent history.
"This new discovery of a molten layer is just one example of how we continue to learn new things from the completed InSight mission,” Lekic said. “We hope that the information we’ve gathered on planetary evolution using seismic data is paving the way for future missions to celestial bodies like the moon and other planets like Venus.”
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The paper, “Geophysical evidence for an enriched molten silicate layer above Mars’ core,” was published in Nature on October 25, 2023.
This research was supported by NASA (Award Nos. 80NSSC18K1628, 80NSSC19M0216 and 80NSSC18K1680), the National Center for Space Studies and the French National Research Agency (Award Nos. ANR-19-CE31-0008-08 and ANR-18-IDEX-0001), the European Research Council (Award No. 101019965) and the U.K. Space Agency (Award No. ST/W002515/1). This story does not necessarily reflect the views of these organizations.
JOURNAL
Nature
METHOD OF RESEARCH
Data/statistical analysis
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Geophysical evidence for an enriched molten silicate layer above Mars’ core
ARTICLE PUBLICATION DATE
25-Oct-2023
Massive space explosion observed creating elements needed for life
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A TEAM OF SCIENTISTS HAS USED NASA’S JAMES WEBB SPACE TELESCOPE TO OBSERVE AN EXCEPTIONALLY BRIGHT GAMMA-RAY BURST, GRB 230307A, AND ITS ASSOCIATED KILONOVA. KILONOVAS—AN EXPLOSION PRODUCED BY A NEUTRON STAR MERGING WITH EITHER A BLACK HOLE OR WITH ANOTHER NEUTRON STAR—ARE EXTREMELY RARE, MAKING IT DIFFICULT TO OBSERVE THESE EVENTS. THE HIGHLY SENSITIVE INFRARED CAPABILITIES OF WEBB HELPED SCIENTISTS IDENTIFY THE HOME ADDRESS OF THE TWO NEUTRON STARS THAT CREATED THE KILONOVA.
THIS IMAGE FROM WEBB’S NIRCAM (NEAR-INFRARED CAMERA) INSTRUMENT HIGHLIGHTS GRB 230307A’S KILONOVA AND ITS FORMER HOME GALAXY AMONG THEIR LOCAL ENVIRONMENT OF OTHER GALAXIES AND FOREGROUND STARS. THE NEUTRON STARS WERE KICKED OUT OF THEIR HOME GALAXY AND TRAVELED THE DISTANCE OF ABOUT 120,000 LIGHT-YEARS, APPROXIMATELY THE DIAMETER OF THE MILKY WAY GALAXY, BEFORE FINALLY MERGING SEVERAL HUNDRED MILLION YEARS LATER.
view moreCREDIT: NASA, ESA, CSA, STSCI, ANDREW LEVAN (IMAPP, WARW)
Scientists have observed the creation of rare chemical elements in the second-brightest gamma-ray burst ever seen – casting new light on how heavy elements are made.
Researchers examined the exceptionally bright gamma-ray burst GRB 230307A, which was caused by a neutron star merger. The explosion was observed using an array of ground and space-based telescopes, including NASA’s James Webb Space Telescope, Fermi Gamma-ray Space Telescope, and Neil Gehrels Swift Observatory.
Publishing their findings today in Nature (25 Oct), the international research team which included experts from the University of Birmingham, reveal that they found the heavy chemical element tellurium, in the aftermath of the explosion.
Other elements such as iodine and thorium, which are needed to sustain life on earth, are also likely to be amongst the material ejected by the explosion, also known as a kilonova.
Dr Ben Gompertz, Assistant Professor of Astronomy at the University of Birmingham, and co-author of the study explains: “Gamma-ray bursts come from powerful jets travelling at almost the speed of light – in this case driven by a collision between two neutron stars. These stars spent several billion years spiralling towards one another before colliding to produce the gamma-ray burst we observed in March this year. The merger site is the approximate length of the Milky Way (about 120,000 light-years) outside of their home galaxy, meaning they must have been launched out together.
“Colliding neutron stars provide the conditions needed to synthesise very heavy elements, and the radioactive glow of these new elements powered the kilonova we detected as the blast faded. Kilonovae are extremely rare and very difficult to observe and study, which is why this discovery is so exciting.”
GRB 230307A was one of the brightest gamma-ray bursts ever observed - over a million times brighter than the entire Milky Way Galaxy combined. This is the second time individual heavy elements have been detected using spectroscopic observations after a neutron star merger, providing invaluable insight into how these vital building blocks needed for life are formed.
Lead author of the study Andrew Levan, Professor of Astrophysics at Radboud University in the Netherlands, said: “Just over 150 years since Dmitri Mendeleev wrote down the periodic table of elements, we are now finally in the position to start filling in those last blanks of understanding where everything was made, thanks to the James Webb Telescope.”
GRB 230307A lasted for 200 seconds, meaning it is categorised as a long-duration gamma-ray burst. This is unusual as short gamma-ray bursts, which last less than two seconds, are more commonly caused by neutron star mergers. Long gamma-ray bursts like this one are usually caused by the explosive death of a massive star.
The researchers are now seeking to learn more about how these neutron star mergers work and how they power these huge element-generating explosions.
Dr Samantha Oates, a co-author of the study while a postdoctoral research fellow at the University of Birmingham (now a lecturer at Lancaster University) said: “Just a few short years ago discoveries like this one would not have been possible, but thanks to the James Webb Space Telescope we can observe these mergers in exquisite detail.”
Dr Gompertz concludes: “Until recently, we didn’t think mergers could power gamma-ray bursts for more than two seconds. Our next job is to find more of these long-lived mergers and develop a better understanding of what drives them – and whether even heavier elements are being created. This discovery has opened the door to a transformative understanding of our universe and how it works.”
ENDS
For more information please contact Ellie Hail, Communications Officer, University of Birmingham at e.hail@bham.ac.uk or alternatively on +44 (0)7966 311 409. You can also contact the Press Office out of hours on +44 (0)121 414 2772.
Notes to editors
Image caption/credit: This image from Webb’s NIRCam (Near-Infrared Camera) instrument highlights GRB 230307A’s kilonova and its former home galaxy among their local environment of other galaxies and foreground stars. Credit: NASA, ESA, CSA, STScI, Andrew Levan (IMAPP, Warw).
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JOURNAL
Nature
METHOD OF RESEARCH
Observational study
ARTICLE TITLE
Heavy element production in a compact object merger observed by JWST
ARTICLE PUBLICATION DATE
25-Oct-2023
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