Green hydrogen is hydrogen gas produced by splitting water using electrolysis powered entirely by renewable electricity. It is important because it provides a clean fuel option for industries that are very difficult to decarbonise using other methods. Sectors such as steel, cement, glass, and chemicals require extremely high temperatures (1,000–1,600°C), which are hard to achieve reliably or cheaply with electricity alone, so they still rely heavily on fossil fuels.
In this work, the researchers examined whether using green hydrogen actually reduces emissions across different sectors, comparing it not only with fossil fuels but also with other low‑emission alternatives such as heat pumps, electric vehicles, and biofuels. They carried out a prospective life cycle assessment covering all stages of hydrogen (production, transport, and use) using projected 2030 conditions that include cleaner electricity grids, improved electrolyser efficiency, updated industrial processes, and expected hydrogen transport methods. They then compared green hydrogen to alternative technologies across eight applications: producing methanol, ammonia, steel, and aviation fuels; powering fuel‑cell passenger cars; providing low‑temperature domestic heat; supplying high‑temperature industrial heat; and balancing the electricity grid over long periods.
Across all eight applications, green hydrogen produced fewer emissions than fossil fuels, although often only marginally. However, when compared to other low‑emission technologies, green hydrogen often performed similarly or worse. This is because producing and transporting hydrogen still generates emissions, especially when the electricity used is not extremely low‑carbon, and because electrolysis itself is relatively inefficient. Green hydrogen only outperforms other clean options when it is produced using very low‑carbon electricity (such as wind power) and used on‑site without transport. Under these ideal conditions, it becomes the preferred option for ammonia and steel production, industrial and domestic heating, and long‑term grid balancing.
To maximise hydrogen’s climate benefit, emissions must be reduced across the entire supply chain, and hydrogen should be prioritised only in applications where it genuinely outperforms other clean alternatives. The authors propose a climate ladder to help rank and prioritise hydrogen use across sectors, guiding smarter policy and investment decisions.
Climate-optimal use of green hydrogen
Kiane de Kleijne et al 2025 Prog. Energy 7 034001
Research and development of hydrogen carrier based solutions for hydrogen compression and storage Martin Dornheim et al. (2022)
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An unusual signal initially picked up by the LIGO and Virgo gravitational wave detectors and subsequently by optical telescopes around the world may have been a “superkilonova” – that is, a kilonova that took place inside a supernova. According to a team led by astronomers at the California Institute of Technology (Caltech) in the US, the event in question happened in a galaxy 1.3 billion light years away and may have been the result of a merger between two or more neutron stars, including at least one that was less massive than our Sun. If confirmed, it would be the first superkilonova ever recorded – something that study leader Mansi Kasliwal says would advance our understanding of what happens to massive stars at the end of their lives.
A supernova is the explosion of a massive star that occurs either because the star no longer produces enough energy to prevent gravitational collapse, or because it suddenly acquires large amounts of matter from a disintegrating nearby object. Such explosions are an important source of heavy elements such as carbon and iron in the universe.
Kilonovae are slightly different. They occur when two neutron stars collide, producing heavier elements such as gold and uranium. Both types of events can be detected from the ripples they produce in spacetime – gravitational waves – and from the light they give off that propagates across the cosmos to Earth-based observers.
The first – and so far only – confirmed observation of a kilonova came in 2017 as a result of two neutron stars colliding. This event, known as GW170817, produced gravitational waves that were detected by the Laser Interferometer Gravitational-wave Observatory (LIGO), which is operated by the US National Science Foundation, and by its European partner Virgo. Several ground-based and space telescopes also observed light signals associated with GW170817, which enabled astronomers to build a clear picture of what happened.
Kasliwal and colleagues now believe they have evidence for a second kilonova with a very different cause. They say that this event, initially called ZTF 25abjmnps and then renamed AT2025ulz, could be a kilonova driven by a supernova – something that has never been observed before, although theorists predicted it was possible.
The gravitational waves from AT2025ulz reached Earth on 18 August 2025 and were picked up by the LIGO detectors in Louisiana and Washington and by Virgo in Italy. Scientists there quickly alerted colleagues to the signal, which appeared to be coming from a merger between two objects, one of which was unusually small. A few hours later, the Zwicky Transient Facility (ZTF) at California’s Palomar Observatory identified a rapidly fading red object 1.3 billion light-years away that appeared to be in the same location as the gravitational wave source.
Several other telescopes that were previously part of the Kasliwal-led GROWTH (Global Relay of Observatories Watching Transients Happen) programme, including the W M Keck Observatory in Hawaiʻi and the Fraunhofer telescope at the Wendelstein Observatory in Germany, picked up the event’s trail. Their observations confirmed that the light eruption had faded fast and glowed at red light wavelengths – exactly what was observed with GW170817.
A few days later, though, something changed. AT2025ulz grew brighter, and telescopes began to pick up hydrogen lines in its light spectra – a finding that suggested it was a Type IIb (stripped-envelope core-collapse) supernova, not a kilonova.
Kasliwal, however, remained puzzled. While she agrees that AT2025ulz does not resemble GW170817, she argues that it also doesn’t look like a run-of-the-mill supernova.
In her view, that leaves two possibilities. The first involves a process called fragmentation in which a rapidly spinning star explodes in a supernova and collects a disc of material around it as it collapses. This disc material subsequently aggregates into a tiny neutron star in much the same way as planets form. The second possibility is that a rapidly spinning massive star exploded as a supernova and then split into two tiny neutron stars, both much less massive than our Sun, which later merged. In other words, a supernova may have produced twin neutron stars that then merged to make a kilonova inside it – that is, a superkilonova.
“We have never seen any hints of anything like this before,” Kasliwal says. “It is amazing to me that nature may make tiny neutron stars smaller than a solar mass and more than one neutron star may be born inside a stripped-envelope supernova.”
While Kasliwal describes the data as “tantalizing”, she acknowledges that firm evidence for a superkilonova would require nebular infrared spectroscopy from either the W M Keck Observatory or the James Webb Space Telescope (JWST). On this occasion, that’s not going to be possible, as the event occurred outside JWST’s visibility window and was too far away for Keck to gather infrared spectra – though Kasliwal says the team did get “beautiful” optical spectra from Keck.
The only real way to test the superkilonova theory would be to find more events like AT2025ulz, and Kasliwal is hoping to do just that. “We will be keeping a close eye on any future events in which there are hints that the neutron star is sub-solar and look hard for a young stripped envelope supernova that could have exploded at the same time,” she tells Physics World. “Future superkilonova discoveries will open up this entirely new avenue into our understanding of what happens to massive stars.”
The study is detailed in The Astrophysical Journal Letters.
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A Falcon 9 launched a batch of Starlink satellites on Feb. 7 after SpaceX completed an investigation into an engine malfunction during the rocket’s previous launch five days earlier.
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An investor in two space companies that went public in the past year said an upcoming SpaceX IPO could generate new investor interest while also triggering a wave of consolidation.
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Starfish’s Otter spacecraft will support relocation and life extension of military satellites
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China launched its experimental reusable spacecraft for the fourth time late Friday, once again maintaining strict secrecy around the mission.
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After losing about 20% of its civil servant workforce in the past year, NASA’s administrator says the agency plans to bring more expertise in-house and reduce its reliance on contractors.
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While Viasat has no plans to join the rush to deploy orbital data centers, the satellite operator sees a role providing the communications links needed to connect such systems with users on Earth and other spacecraft.
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In 2025, more than 322,000 civil servants left jobs voluntarily or were dismissed out of a workforce of roughly 2.4 million. The 13% drop in staffing is the largest single-year decline since the end of World War II. In total, more than 5,000 people who were part of the federal space workforce left their positions. […]
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In 2025, more than 322,000 civil servants left jobs voluntarily or were dismissed out of a workforce of roughly 2.4 million. The 13% drop in staffing is the largest single-year decline since the end of World War II. In total, more than 5,000 people who were part of the federal space workforce left their positions. […]
The post ‘Serving the country and pushing the boundaries of human existence is very purposeful.’ appeared first on SpaceNews.
In 2025, more than 322,000 civil servants left jobs voluntarily or were dismissed out of a workforce of roughly 2.4 million. The 13% drop in staffing is the largest single-year decline since the end of World War II. In total, more than 5,000 people who were part of the federal space workforce left their positions. […]
The post ‘I loved thinking about how to make science possible for America and for the world’ appeared first on SpaceNews.
In 2025, more than 322,000 civil servants left jobs voluntarily or were dismissed out of a workforce of roughly 2.4 million. The 13% drop in staffing is the largest single-year decline since the end of World War II. In total, more than 5,000 people who were part of the federal space workforce left their positions. […]
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