News from around the universe

12 March 2024

Record-breaking image of a dead star’s scattered remains

This billowing mass of dust filaments and gas tendrils stretching across 100 light years of space is the Vela supernova remnant – the scattered ashes of a star that exploded about 11,000 years ago. The image was acquired by the Dark Energy Camera (DECam), mounted on the Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile. DECam was originally designed to conduct a survey of distant galaxies to measure the strength of dark energy as it accelerates the universe’s expansion and draws those galaxies away from us. On completion of that survey, however, DECam has been used in a more general fashion. It is one of the most powerful wide-field instruments ever built, and this image of the Vela supernova remnant is proof of its capabilities. It’s the largest image ever released by the camera at 1.3 gigapixels in size.

The image has to be large to capture all that detail across such a large swath of sky. The Vela supernova remnant is a nebula that is about 100 light years across. Because it’s about 800 light years away from us, this means the Vela supernova remnant spans an area on the celestial sphere 20 times larger than the angular diameter of the full Moon. The Vela supernova remnant itself is of crucial astronomical importance. It gives us a good look at the late stages of the development of such a remnant and offers insight into how material blown out by the supernova gradually disperses into the interstellar medium, which is the thin mist of gas that fills the space between stars.

The shock wave from the ancient stellar explosion that formed the Vela supernova remnant is still expanding into space, where it is colliding with the interstellar medium and compressing it, creating the delicate filaments we can see in the image. Absorption lines from elements like calcium, carbon, copper, germanium, krypton, magnesium, nickel, oxygen and silicon – many of them ionised and doubly ionised – have been detected in the supernova debris as well. These are heavy elements forged either by fusion processes within the star before it exploded or by the ferocious energies unleashed by the explosion itself.

9 March 2024

Webb hones in on a star-forming region

Spectacular new images from the James Webb Space Telescope reveal the stunning and intricate details of a star-birthing region in the Triangulum Galaxy. Webb imaged the star-forming region NGC 604, located some 2.7 million light years from Earth, using its Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). The gas clouds that fill this starbirthing region are estimated to be around 1,300 light years across, and NGC 604 is estimated to be relatively young at just 3.5 million years old. The Webb images show tendrils and envelopes of gas that enshroud over 200 stars in the very early stages of their lives. These stars, some of which have masses around 100 times that of the Sun, are rare to find in concentrations like this in the nearby universe. These infant stars emit intense radiation, especially over ultraviolet wavelengths, and blow out powerful stellar winds that carve out cavities in NGC 604’s gas. These cavernous voids can be seen as huge, dark ‘bubbles’ surrounded by wispy tendrils.

In the NIRCam image, tendrils of gas are prominently seen as bright-red threads extending from those voids. A ghostly blueand-white glow around these tendrils is the result of ultraviolet light ionising hydrogen gas. Bright-orange streaks in this NIRCam image indicate the presence of carbonbased molecules called polycyclic aromatic hydrocarbons (PAHs). This is significant because PAHs play an important role in forming both stars and planets, and are considered important building blocks for life here on Earth. However, where PAHs originate remains a mystery. Further from the dark voids are deeper red clouds which signify the presence of unionised molecular hydrogen. It is in this cooler gas where stars are more likely to form. Spotted throughout the NIRCam image are bright, blue stars in the process of creating voids of their own.

28 February 2024

Rippling sand dunes and icy cliffs spied near Mars’ north pole

The Martian north polar region is a strange and fascinating place, even by the standards of its strange and fascinating planet. There, the dust that coats the surface of Mars mixes with water ice. Layers upon layers of dust and ice stack miles deep, covering a region the size of France. For much of the Martian year, this region is buried under a cap of frozen carbon dioxide, also known as dry ice. But when Martian summer comes, the dry ice disappears into the planet’s atmosphere. And it was in the midst of summer that the European Space Agency’s Mars Express orbiter captured a little slice of the north polar landscape.

The Mars Express image shows the frontier between two distinct regions. To the left is Olympia Planum, a vast expanse of sweeping sand dunes that appear as little wrinkles in a field of dust. And on the other side is Planum Boreum, which includes the north pole itself, which is out of frame to the image’s right. Planum Boreum is strikingly smooth – a sign that the surface is very young, largely untouched by the ravages of erosion and meteor impacts. Indeed, Planum Boreum likely gets a yearly refresh every time the winter ice comes and goes. This borderland is cut apart by crescent-shaped cliffs, the largest of them about 20 kilometres (12 miles) wide. These cliffs are the result of winds wearing away the surface. The cliffs are part of a spiral of troughs spindled across the entire north pole. Mars Express has now been orbiting the Red Planet for more than two decades, having arrived there on 25 December 2003. The spacecraft has not only snapped a wealth of high-definition images of the Martian surface, but also studied the atmosphere of Mars and probed the planet’s interior.

14 March 2024

Icy building blocks of life found swirling around infant stars

Using Webb, astronomers have identified several of the icy building blocks of life in the gas and dust swirling around two infant stars, or protostars. The molecules spotted range from relatively simple molecules like methane to complex compounds like acetic acid and ethanol. Complex organic molecules (COMs) in solid icy forms had previously been predicted to exist around protostars that have not yet begun birthing planets, though this prediction stemmed from Earth-based experiments. The theory had been tentatively confirmed in the past using space telescopes including Webb, which found diverse ices in the darkest, coldest regions of a molecular cloud as part of the Early Release Science Ice Age program. But thanks to observations of the clouds around protostars IRAS 23385 and IRAS 2A, taken with Webb’s highly sensitive Mid-Infrared Instrument (MIRI) as part of the JWST Observations of Young protoStars program, the presence of these ices has now been confirmed.

Of particular interest for future study is the material around the low-mass protostar IRAS 2A, which may have similarities with our Sun when it was in its primordial stages over 4.6 billion years ago. That means the same chemical ices identified around IRAS 2A were likely present in the first stages of our Solar System’s development, eventually finding themselves delivered to the primitive Earth. “This finding contributes to one of the longstanding questions in astrochemistry,” team leader and Leiden University researcher Will Rocha said. “What is the origin of COMs in space? Are they made in the gas phase or in ice? The detection of COMs in ices suggests that solid-phase chemical reactions on the surfaces of cold dust grains can build complex kinds of molecules.” It’s worth noting that COMs have technically been detected around protostars before, but in the form of warm gas. Research has suggested that these gases are created when the solid ice is transformed into such gas directly, therefore skipping the liquid phase. This is a process called sublimation. Detecting these icy COMs could help better understand the origins of even larger molecules in space.

DARPA picks Northrop Grumman to develop a ‘lunar railroad’ concept

Railroads could open the Moon to serious and sustained economic development, just as they did in the American West in the late 19th century. That’s apparently the hope of the US Defense Advanced Research Projects Agency (DARPA), which is supporting the development of a lunar railroad concept proposed by aerospace giant Northrop Grumman. “The envisioned lunar railroad network could transport humans, supplies and resources for commercial ventures across the lunar surface, contributing to a space economy for the United States and international partners,” Northrop Grumman representatives wrote in a press statement on 19 March.

Northrop Grumman was one of 14 companies that DARPA selected this past December to participate in its 10-Year Lunar Architecture (LunA-10) Capability Study, which aims to help humanity extend its economic footprint into deep space. “A large paradigm shift is coming in the next ten years for the lunar economy,” Michael Nayak, program manager in DARPA’s Strategic Technology Office, said last August, when the agency announced the LunA-10 project.

“To get to a turning point faster, LunA-10 uniquely aims to identify solutions that can enable multi-mission lunar systems – imagine a wireless power station that can also provide communications and navigation in its beam,” Nayak said. Such work, he added, will accelerate “key technologies that may be used by the government and the commercial space industry, and ultimately to catalyse economic vibrancy on the Moon.”

Northrop Grumman’s statement did not provide funding details. DARPA gives a ballpark number in its August 2023 announcement, stating that selected studies “will receive an Other Transaction award not to exceed $1,000,000 (around £795,000).” The selected LunA-10 companies will share their work at the Lunar Surface Innovation Consortium Spring Meeting next month and write up final reports that will be released in June.

The Europa Clipper may only need one ice grain to detect life on Jupiter’s ocean moon

A single grain of ice ejected from Jupiter’s ocean moon Europa could be enough to reveal evidence of alien life. “With suitable instrumentation, such as the SUrface Dust Analyzer (SUDA) on NASA’s Europa Clipper space probe, it might be easier than we thought to find life, or traces of it, on icy moons,” said Frank Postberg of Freie Universität Berlin. The Europa Clipper is scheduled to blast off in October 2024. It’s expected to arrive in 2030, then perform nearly 50 close flybys of Europa, skimming the icy surface at altitudes as low as 25 kilometres (16 miles). The mission’s primary objective is to learn more about the habitability of Europa’s subterranean ocean and the thickness of the ice shell above it. In 2006, the Cassini mission to Saturn discovered plumes of water vapour belching out from Enceladus’ ocean through large fractures in the surface. Under the assumption that the Europa Clipper may also fly through an icy moon plume, scientists led by Fabian Klenner of the University of Washington in Seattle investigated whether SUDA might be able to detect any life carried up from the ocean on the plume. SUDA is designed to study particles of Europa’s surface ice and dust sputtered into space as the moon is constantly bombarded by micrometeorites, but perhaps it could analyse ice grains in the plumes, too.

Simulating high-velocity impacts of ice grains on the instrument in a laboratory would be pretty impractical, so instead Klenner’s team fired a thin, fast-moving jet of water vapour loaded with a bacterium called Sphingopyxis alaskensis into a vacuum chamber. S. alaskensis is found in seawater off the coast of Alaska, and is at home in cold temperatures surviving off few nutrients. It’s one of the closest things we have to a life form on Earth that could survive in Europa’s ocean.

More pertinently to the Europa Clipper’s potential for finding such life, the bacteria “are extremely small, capable of fitting into ice grains that are emitted from an ocean world like Enceladus or Europa,” said Klenner. The vacuum resulted in the water jet disintegrating into droplets that froze as ice grains. The grains were then studied with a mass spectrometer, mimicking how SUDA will study any grains that it picks up in real life.

The results of the experiment showed that S. alaskensis, or at least the parts of it that form ocean scum, could indeed be detected from studying just a single ice grain.

Scientists find a galaxy supercluster as massive as 26 quadrillion Suns

Astronomers have discovered a cavalcade of monster superclusters, incredibly massive collections of galaxies and galaxy clusters. The most striking example of these 662 new superclusters is located around 3 billion light years away from Earth and has been named the Einasto Supercluster. The Einasto Supercluster is staggering in terms of its sheer size and mass. It contains the same mass as around 26 quadrillion Suns. This supercluster is so vast that it would take a light signal 360 million years to travel from one side of it to the other.

From the sample discovered, the team, led by astronomers from Tartu Observatory, was able to calculate the average supercluster mass and size. The researchers determined that the typical mass of a supercluster in this collection is around 6 quadrillion solar masses, while the typical size is around 200 million light years across. To put this into perspective, the average supercluster is around 2,000 times larger than the Milky Way. In terms of mass, if the Sun were the same mass as a golf ball, one of these superclusters would have the same mass as Mount Everest. While exploring the properties of these superclusters, the team found that the clusters of galaxies within the superclusters are heavier than those found outside the superclusters. This demonstrates that galaxies in superclusters grow and evolve differently from galaxies outside such environments.

NASA is beefing up the SLS rocket for its Artemis program

NASA hasn’t yet sent an astronaut to space for the Artemis program, but the effort is already targeting upgrades. A more powerful version of the Space Launch System (SLS) will launch in the coming decade for more ambitious Moon missions, starting with Artemis IV. The larger version, called Block 1B, can carry both crew and big pieces of hardware towards the Moon as NASA aims to build a settlement at the lunar south pole. Features of the upgraded SLS will include a “more powerful second stage and an adapter for large cargos,” NASA officials said. Testing on more powerful RS-25 engines for SLS is happening right now at NASA’s Stennis Space Center, upgrading the engine type first developed for the Space Shuttle program. NASA is performing a 12-engine hotfire certification series for the new RS-25 type to be ready for Artemis V and beyond.

The greater Artemis program eventually aims for a long-term Moon settlement near water ice resources. A coalition of nations is heading there under the NASA-led Artemis Accords, although most of the 35 signatories are not contributing hardware, and instead are committing to following US-led peaceful space exploration norms. Artemis I, an uncrewed mission, flew around the Moon in 2022 and astronaut missions are coming up soon. Artemis II will send four astronauts around the Moon no earlier than 2025, while Artemis III is aiming for a 2026 crewed touchdown. Numerous technical reasons delayed the launches of Artemis II and III in January, but development continues.

These first three lunar missions use the interim cryogenic propulsion stage to boost the Orion spacecraft, which is a single-engine stage. The missions, starting with Artemis IV, will instead use a four-engine stage called the Exploration Upper Stage (EUS). One of the benefits of EUS is a different battery that will allow it to operate for eight hours – four times what Artemis I and III are designed for. Then, missions starting with Artemis V will receive more powerful RS-25 engines. Artemis IV and beyond will also have a universal stage adapter that has more storage area and more than 286 cubic metres (10,000 cubic feet) of space to carry large components. That’s plenty of room for big items, such as modules for NASA’s future Gateway space station around the Moon.

Mysterious ‘unparticles’ may be pushing the universe apart

The ever-accelerating expansion of the universe may be driven by a mysterious form of matter called ‘unparticles’, which do not obey the Standard Model of particle physics, a new theoretical paper suggests. Scientists widely acknowledge that the universe is expanding, though the cause of that expansion remains elusive. One of the most popular proposed explanations is a mysterious entity called dark energy in the form of a cosmological constant, which leads to expansion at a rate independent of the age of the universe and the temperature of matter and radiation. However, recent astronomical observations challenge this hypothesis, prompting physicists to explore alternatives to what dark energy could be.

In a new paper, researchers analysed the idea that dark energy is instead made of a theoretical form of matter called unparticles. They found that this theory aligns better with observations than the prevalent standard cosmological model, which assumes a cosmological constant. “Observationally, discrepancies arise in the values of the universe’s expansion rate and the growth of large-scale structures between measurements,” study co-author Utkarsh Kumar, a cosmologist at Ariel University, said. “Various observations, including cosmic microwave background measurements, dimming of supernovae and many others, contribute to this tension.”

Quantities such as the Hubble constant, which determines the rate of expansion, and the so-called S8, which contains information about the formation of large-scale structures, are not measured directly.

Instead, they are calculated from observations of the cosmic microwave background – leftover radiation from the Big Bang – and distant stars and galaxies using mathematical theories. However, different theories yield different values of these parameters from the same data, posing a huge tension in cosmology.

To address this problem, the authors of the new study, published in December 2023 in the Journal of Cosmology and Astroparticle Physics, suggest that the expansion of the universe is driven not by a cosmological constant but by unparticles, which had previously been considered in the context of particle physics. “The idea of unparticles was introduced by [theoretical physicist Howard] Georgi over a decade ago,” lead study author Ido Ben-Dayan, also of Ariel University, said. “In fundamental physics, we usually discuss fields, like the electric field, where particles are excitations of that field. In the electric field case, these are photons.” In almost all cases, Ben-Dayan added, particles are excitations with a well-defined mass and momentum.

However, “unparticles are the result of a set of fields where their excitations do not have a well-defined momentum and mass,” Ben-Dayan said. “Thus, at the macroscopic level, they behave as a fluid. A special outcome of this property is that their equation of state, describing the ratio between the pressure they exert and their energy density, depends on temperature.” This equation of state strongly resembles the equation for the cosmological constant. Moreover, the very weak interaction of unparticles with regular matter, which is predicted by all theoretical models of the substance, makes it an excellent candidate for dark energy.

NASA’s DART mission hammered its target asteroid into a new shape

The shape of the asteroid Dimorphos was changed when NASA’s Double Asteroid Redirection Test (DART) deliberately crashed into it in 2022 as part of a test of humanity’s planetary defence capabilities. DART was designed to show whether we could divert a potentially hazardous asteroid away from Earth. It was sent to a binary asteroid in which the 170-metre (560-foot) wide Dimorphos orbits a larger 760-metre (2,493- foot) wide space rock called Didymos. When DART impacted Dimorphos on 26 September 2022, astronomers were able to measure how much the impact had nudged the asteroid by measuring how the space rock’s orbit around Didymos changed.

Now, scientists have shown that it seems DART didn’t just give Dimorphos a push – it hit Dimorphos with enough kinetic energy to reshape it. “The entire shape of the asteroid has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon,” said Shantanu Naidu of NASA’s Jet Propulsion Laboratory (JPL) in California. Originally, Dimorphos would have been an oblate spheroid, which is kind of like a squashed ball. The impact of DART at five kilometres (three miles) per second sent shock waves through the asteroid, resulting in it becoming more elongated and shifting its axis of rotation off centre. The new shape is inferred by astronomers from the light curve of the Didymos-Dimorphos system, which is aligned in such a way that we can see them transiting and eclipsing one another.

This conclusion from Naidu’s team is also shared in work published in February by a group spearheaded by Sabina Raducan of the University of Bern in Switzerland. Raducan’s team concluded that the impact had resulted in up to one per cent of Dimorphos’ mass being ejected into space, and another eight per cent being redistributed across the surface as the asteroid absorbed the impact energy and reshaped itself. The conclusion was that to allow itself to morph in such a way, Dimorphos must be a loose rubble pile – an agglomeration of dirt and rocks held together by weak gravity which can easily be reshaped, as opposed to a rigid structure that would not give as easily. “The results of the study agree with others that are being published,” said Tom Statler, who is program scientist in the Science Mission Directorate’s Planetary Science Division at NASA Headquarters. “Seeing separate groups analyse the data and independently come to the same conclusions is a hallmark of a solid scientific result.”

The new study also confirms how much Dimorphos’ orbit around Didymos was altered by DART’s impact. Prior to the impact, Dimorphos revolved around Didymos once every 11 hours and 55 minutes, with an orbital radius of 1,189 metres (3,900 feet). Studies of the light curve, coupled with radar observations from the Deep Space Network’s Goldstone Solar System Radar in California, show that Dimorphos’ orbital period has reduced to 11 hours, 22 minutes and 3 seconds, within an error margin of 1.5 seconds. Its orbital radius has also been reduced to 1,152 metres (3,780 feet).

Given that Dimorphos’ axis of rotation is now offset from its geographical centre, Dimorphos now rocks backwards and forwards as it orbits Didymos – a swaying motion that’s detectable through the shape of the light curve. “Before impact the times of the [transit] events occurred regularly, showing a circular orbit,” said JPL’s Steve Chesley. “After impact there were very slight timing differences, showing something was askew. We never expected to get this kind of accuracy.”

DART was designed to test whether it would be possible to alter the trajectory of a small but dangerous asteroid if it were on a collision course with Earth. The experiment exceeded scientists’ expectations in terms of how much DART nudged Dimorphos and what the impact is teaching us about how asteroids behave when faced with such kinetic violence. “DART is not only showing us the pathway to an asteroid-deflection technology, it’s revealing a new fundamental understanding of what asteroids are and how they behave,” said Statler.

But the study of Didymos and Dimorphos is not over yet. In October 2024, the European Space Agency (ESA) will launch the Hera spacecraft, which is a mission to encounter the two asteroids and inspect how much damage DART did to Dimorphos, in addition to studying the nature of the asteroids more closely.