Dr Mathew Smith and Dr Georgios Dimitriadis from Lancaster University are both members of the Zwicky Transient Facility (ZTF), a wide-field sky astronomical survey using a new camera attached to the Samuel Oschin Telescope at Palomar Observatory in California.

Type Ia Supernovae are the dramatic explosions of white dwarf stars at the ends of their lives. Cosmologists use them to probe distances across the universe by comparing their fluxes, as further objects appear dimmer.

The ZTF cosmology science working group is today publishing twenty-one articles studying these 3628 Type Ia Supernovae, forming a Special Issue in Astronomy & Astrophysics.

Lancaster astrophysicist Dr Mathew Smith, co-leader of the ZTF SN Ia DR2 release, said: “This release provides a game-changing dataset for supernova cosmology. It opens the door to new discoveries about both the expansion of the universe and the fundamental physics of supernovae.”

This is the first time that astrophysicists have access to such a large and homogeneous dataset. Type Ia supernovae are rare, occurring approximately once per thousand years in a typical galaxy, but ZTF’s depth and survey strategy enable researchers to detect nearly four per night. In only two and a half years, ZTF has doubled the number available Type Ia Supernovae for cosmology acquired for the last 30 years to almost three thousand.

Head of the ZTF Cosmology Science working group Dr Mickael Rigault from the Institut des deux Infinis de Lyon (CNRS / Claude Bernard University) said: “”For the past five years, a group of thirty experts from around the world have collected, compiled, assembled, and analysed these data. We are now releasing it to the entire community. This sample is so unique in terms of size and homogeneity, that we expect it to significantly impact the field of Supernovae cosmology and to lead to many additional new discoveries in addition to results we have already published.”

The ZTF camera, installed on the 48-inch Schmidt telescope at Palomar Observatory, scans the entire northern sky daily in three optical bands, reaching a depth of 20.5 magnitude — one million times fainter than the dimmest stars visible to the naked eye. This sensitivity allows ZTF to detect nearly all supernovae within 1.5 billion light-years of Earth.

Professor Kate Maguire from Trinity College Dublin, a co-author of the study, said: “Thanks to ZTF’s unique ability to scan the sky rapidly and deeply, we have captured multiple supernovae within days — or even hours — of explosion, providing novel constraints on how they end their lives.”

The acceleration of the expansion of the Universe, awarded by the Nobel prize in 2011, was discovered in the late 90s using approximately a hundred of these Supernovae. Since then, cosmologists are investigating the reason for this acceleration caused by the dark energy that plays the role of an anti-gravity force across the Universe.

Co-author Professor Ariel Goobar, Director of the Oskar Klein Centre in Stockholm, one of the founding institutions of ZTF, and also member of the team that discovered the accelerated expansion of the Universe in 1998 said: “Ultimately, the aim is to address one of our time’s biggest questions in fundamental physics and cosmology, namely what is most of the Universe made of? For that we need the ZTF supernova data.”

One of the key outcomes of these studies is that Type Ia Supernovae intrinsically vary as a function of their host environment, more so than expected before, and the correction mechanism assumed so far has to be revisited. This could change how we measure the expansion history of the Universe and may have important consequences for current deviation observed in the standard model of cosmology.

Dr Rigault said: “With this large and homogeneous dataset, we can explore Type Ia supernovae with an unprecedented level of precision and accuracy. This is a crucial step toward honing the use of Type Ia Supernovae in cosmology and assess if current deviations in cosmology are due to new fundamental physics or unknown problem in the way we derive distances.”

The study — led by the University of Exeter and the Ascension Island Government — examined three seamounts off Ascension Island in the South Atlantic Ocean.

Two were shallow seamounts, with peaks less than 100 metres below the surface — and these were teeming with vast numbers of predators, including sharks and tuna.

“Seamounts have been likened to oases of life in the comparative deserts of the open ocean,” said Dr Sam Weber, from the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“However, this hasn’t been studied in detail — meaning we’ve been unsure about why seamounts attract so many marine top predators.”

Some seamounts create upwellings of minerals that support bountiful phytoplankton (tiny drifting plants that are the first link in ocean food chains).

Such quantities of phytoplankton can support increased numbers of other species, from zooplankton (which eat phytoplankton) all the way to top predators like sharks.

But this study found no evidence of increased “primary productivity” of phytoplankton at the Ascension seamounts.

Instead, enrichment of marine life (measured by “biomass” — the total weight of organic material) goes up with each level of the food web.

Zooplankton were twice as common at shallow seamounts than in the open ocean, while shark biomass was 41 times higher.

“Our findings suggest that several factors combine to make seamounts so rich in sea life, especially predators,” Dr Weber said.

“While primary productivity is not higher at the seamounts we studied, filter feeders may benefit from prey being ‘blown over’ the peak, and the peak may also stop prey species from retreating into deeper water to avoid predators. This effectively concentrates food in one predictable spot in the ocean.

“Also, some predators appear to use seamounts as ‘hubs’ to gather, socialise, mate or rest, and as a base to return to after hunting in the open ocean. This may lead to more top predators on seamounts than you would expect based on the amount of food available.”

The findings suggest certain species tend to gather at seamounts — including Galapagos and silky sharks, and yellowfin and bigeye tuna.

Some individual animals were found to be “resident” — living at a particular seamount most of the time — and others visited both shallow seamounts in the study (80km apart).

The study also found a “halo” of increased marine life around seamounts, extending at least 5km into the open ocean.

The seamounts in the study are all within the Ascension Island Marine Protected Area — a 445,000 square km zone where no large-scale commercial fishing or seabed mining are allowed.

“Our results reinforce the conservation significance of shallow seamounts for many top predators,” Dr Weber said.

“This research also offers fundamental insights into seamounts’ role as activity hubs and oases for marine species and shows how these remarkable habitats influence the oceans that surround them.”

Data for the study was collected by a National Geographic Pristine Seas expedition aboard the British Antarctic Survey research vessel RRS James Clark Ross

The research was funded by a European Union BEST grant and the UK government’s Darwin Initiative.

The play-like behaviour of the flies described by the researchers, involving voluntary passive movements such as swinging, bobbing, sliding or turning, has now been demonstrated in insects for the first time. “This could help us to find out how we humans also develop efficient self-awareness of our bodies,” explains Huetteroth, whose study was funded by the German Research Foundation (DFG).

In collaboration with Northumbria University, the researchers conducted a detailed analysis of how the flies interacted with the carousel. While many flies avoided the carousel, others visited it repeatedly and for long periods. When two carousels rotated alternately, the flies even actively followed the stimulation.

The scientists placed a total of 190 individual flies in a carousel arena, a glass dome about one centimetre high, and then filmed them for 3 to 14 days. The positions of the flies in the recordings were then automatically recognised and tracked using special software. Only a fraction of the data generated was included in the study. “Using several carousels, we generated and analysed a total of around seven years of film data,” says Dr Tilman Triphan, the first author of the study. This effort was necessary because, unlike most behavioural experiments on flies, the researchers had to rely on the insects’ voluntary behaviour. There was not enough space under the glass dome for the flies to fly onto the carousel. “However, we were able to distinguish whether the flies had deliberately walked onto the carousel or jumped onto it in an uncoordinated way. This allowed us to show that unplanned visits to the carousel were rather atypical for the playing flies,” says co-author Dr Clara H. Ferreira, an assistant Professor at Northumbria University.

According to Huetteroth, the findings will now allow a detailed investigation of the underlying genetic, neuronal and biochemical factors that influence the fruit fly’s playful behaviour and the benefits this has for playful creatures in general.

Cocoa (Theobroma cacao L.) is a vital cash-crop for four to six million small-holder farmers across the tropics, and supports a global chocolate industry valued at over USD 100 billion annually. The combination of millions of farmers relying on cocoa for their livelihoods, and increasing global demand for the crop, has driven cocoa plantation expansion and intensification of farming practices, often at the expense of biodiversity and long-term sustainability.

A new research study led by the University of Oxford, in collaboration with Westlake University, China, Universidade Estadual de Santa Cruz, Brazil, and University of Göttingen, Germany, has highlighted the significant risks posed to cocoa production by climate change. However, the authors also identified farm management solutions that can both climate-proof cocoa crops and boost productivity without the need to expand plantations into forests.

The research, conducted across three major cocoa-producing countries — Brazil, Ghana, and Indonesia, which together account for 33% of global cocoa production — investigated key factors influencing cocoa yields. The findings revealed that increasing pollination rates above current levels could boost yields by 20%. This demonstrates that insufficient pollination is occurring to produce the maximum possible yield for many cocoa plantations. Separate to the impact of pollination, sites where temperatures were up to 7 degrees warmer had 20-31% lower cocoa yields, underscoring the vulnerability of cocoa-producing regions to the effects of climate change.

Co-author Dr Acheampong Atta-Boateng, who recently completed his doctoral work at the University of Oxford, said: ‘Cocoa is pollinated by tiny insects such as midges and thrips, and it comes as quite a surprise that most of the time there simply isn’t enough pollination happening to produce the cocoa crop that is possible.’

To support sustainable cocoa production, researchers recommend practical strategies to enhance pollination, such as maintaining leaf litter and other understory biomass, preserving soil organic matter, providing moderate shade, and reducing agricultural chemical use. These practices not only increase pollinator abundance, but also help regulate plantation temperatures and improve soil health, ensuring long-term plantation resilience.

Dr Tonya Lander, from the University of Oxford and first author of the study said: ‘This research shows that sustainable agricultural methods can significantly improve cocoa yields without farm expansion or intensification. By adopting biodiversity-centred, climate-resilient farming techniques, the cocoa sector can both increase production and safeguard farmers’ livelihoods.’

Dr Tom Wanger of Westlake University, China added: ‘The rising demand for cocoa and the short-term economic benefits to farmers has led to plantation expansion and ecological homogenization at the expense of biodiversity and vital ecosystem services, like pollination. This study highlights the long-term risks of this approach, and how pollination can be a solution that works alongside climate-resilient agricultural systems to achieve long-term, ecologically and financially sustainable solutions.’

In a new study published in Nature, the scientists report using NASA’s James Webb Space Telescope (JWST) to observe the Phoenix cluster — a sprawling collection of gravitationally bound galaxies that circle a central massive galaxy some 5.8 billion light years from Earth. The cluster is the largest of its kind that scientists have so far observed. For its size and estimated age, the Phoenix should be what astronomers call “red and dead” — long done with any star formation that is characteristic of younger galaxies.

But astronomers previously discovered that the core of the Phoenix cluster appeared surprisingly bright, and the central galaxy seemed to be churning out stars at an extremely vigorous rate. The observations raised a mystery: How was the Phoenix fueling such rapid star formation?

In younger galaxies, the “fuel” for forging stars is in the form of extremely cold and dense clouds of interstellar gas. For the much older Phoenix cluster, it was unclear whether the central galaxy could undergo the extreme cooling of gas that would be required to explain its stellar production, or whether cold gas migrated in from other, younger galaxies.

Now, the MIT team has gained a much clearer view of the cluster’s core, using JWST’s far-reaching, infrared-measuring capabilities. For the first time, they have been able to map regions within the core where there are pockets of “warm” gas. Astronomers have previously seen hints of both very hot gas, and very cold gas, but nothing in between.

The detection of warm gas confirms that the Phoenix cluster is actively cooling and able to generate a huge amount of stellar fuel on its own.

“For the first time we have a complete picture of the hot-to-warm-to-cold phase in star formation, which has really never been observed in any galaxy,” says study lead author Michael Reefe, a physics graduate student in MIT’s Kavli Institute for Astrophysics and Space Research. “There is a halo of this intermediate gas everywhere that we can see.”

“The question now is, why this system?” adds co-author Michael McDonald, associate professor of physics at MIT. “This huge starburst could be something every cluster goes through at some point, but we’re only seeing it happen currently in one cluster. The other possibility is that there’s something divergent about this system, and the Phoenix went down a path that other systems don’t go. That would be interesting to explore.”

Hot and cold

The Phoenix cluster was first spotted in 2010 by astronomers using the South Pole Telescope in Antarctica. The cluster comprises about 1,000 galaxies and lies in the constellation Phoenix, after which it is named. Two years later, McDonald led an effort to focus in on Phoenix using multiple telescopes, and discovered that the cluster’s central galaxy was extremely bright. The unexpected luminosity was due to a firehose of star formation. He and his colleagues estimated that this central galaxy was turning out stars at a staggering rate of about 1,000 per year.

“Previous to the Phoenix, the most star-forming galaxy cluster in the universe had about 100 stars per year, and even that was an outlier. The typical number is one-ish,” McDonald says. “The Phoenix is really offset from the rest of the population.”

Since that discovery, scientists have checked in on the cluster from time to time for clues to explain the abnormally high stellar production. They have observed pockets of both ultrahot gas, of about 1 million degrees Fahrenheit, and regions of extremely cold gas, of 10 kelvins, or 10 degrees above absolute zero.

The presence of very hot gas is no surprise: Most massive galaxies, young and old, host black holes at their cores that emit jets of extremely energetic particles that can continually heat up the galaxy’s gas and dust throughout a galaxy’s lifetime. Only in a galaxy’s early stages does some of this million-degree gas cool dramatically to ultracold temperatures that can then form stars. For the Phoenix cluster’s central galaxy, which should be well past the stage of extreme cooling, the presence of ultracold gas presented a puzzle.

“The question has been: Where did this cold gas come from?” McDonald says. “It’s not a given that hot gas will ever cool, because there could be black hole or supernova feedback. So, there are a few viable options, the simplest being that this cold gas was flung into the center from other nearby galaxies. The other is that this gas somehow is directly cooling from the hot gas in the core.”

Neon signs

For their new study, the researchers worked under a key assumption: If the Phoenix cluster’s cold, star-forming gas is coming from within the central galaxy, rather than from the surrounding galaxies, the central galaxy should have not only pockets of hot and cold gas, but also gas that’s in a “warm” in-between phase. Detecting such intermediate gas would be like catching the gas in the midst of extreme cooling, serving as proof that the core of the cluster was indeed the source of the cold stellar fuel.

Following this reasoning, the team sought to detect any warm gas within the Phoenix core. They looked for gas that was somewhere between 10 kelvins and 1 million kelvins. To search for this Goldilocks gas in a system that is 5.8 billion light years away, the researchers looked to JWST, which is capable of observing farther and more clearly than any observatory to date.

The team used the Medium-Resolution Spectrometer on JWST’s Mid-Infrared Instrument (MIRI), which enables scientists to map light in the infrared spectrum. In July of 2023, the team focused the instrument on the Phoenix core and collected 12 hours’ worth of infrared images. They looked for a specific wavelength that is emitted when gas — specifically neon gas — undergoes a certain loss of ions. This transition occurs at around 300,000 kelvins, or 540,000 degrees Fahrenheit — a temperature that happens to be within the “warm” range that the researchers looked to detect and map. The team analyzed the images and mapped the locations where warm gas was observed within the central galaxy.

“This 300,000-degree gas is like a neon sign that’s glowing in a specific wavelength of light, and we could see clumps and filaments of it throughout our entire field of view,” Reefe says. “You could see it everywhere.”

Based on the extent of warm gas in the core, the team estimates that the central galaxy is undergoing a huge degree of extreme cooling and is generating an amount of ultracold gas each year that is equal to the mass of about 20,000 suns. With that kind of stellar fuel supply, the team says it’s very likely that the central galaxy is indeed generating its own starburst, rather than using fuel from surrounding galaxies.

“I think we understand pretty completely what is going on, in terms of what is generating all these stars,” McDonald says. “We don’t understand why. But this new work has opened a new way to observe these systems and understand them better.”

This work was funded, in part, by NASA.