While Earth’s atmosphere is constantly changing, many spectacular storms and atmospheric waves on Saturn remain stable for decades or even centuries.

Images from NASA’s Voyager craft as it flew-by the planet in the early 1980s revealed a large and long-lived hexagonal atmospheric wave around Saturn’s north pole.

Yet despite decades of observations from other craft such as the Cassini mission, no similar wave has been reported in the southern hemisphere or elsewhere.

Now, Agustín Sánchez-Lavega from the University of the Basque Country in Bilbao and colleagues have spotted a growing decagon-shaped wave around the planet’s south pole.

The researchers discover the phenomenon thanks to images from NASA’s Hubble Space Telescope as well as ground-based telescopes as the planet’s south pole came back into view from Earth due to Saturn’s axial tilt.

It seems that the 10-sided wave developed between 2023 and 2025 and may still be evolving, in contrast to the 40-plus years of steadiness shown by the hexagon.

The longitudes of the decagon’s vertices oscillate over a period of 32 days, and its movements suggest it may be trapped by the curvature of an atmospheric jet.

The researchers suggest the wave could have been created by a spatially periodic disturbance in the jet peak or driven by an “anticyclonic vortex” to its north.

However, further study is required to better understand how it formed and how it compares to the hexagon structure in the north.

“The most intriguing part to me is that this seems to have just formed recently,” notes study co-author Amy Simon from NASA’s Goddard Space Flight Center in Maryland. “The question is, why did it suddenly form now when we haven’t seen one before?”

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Astronomers have created a spectacular composite image of a dying star’s remains in the act of being recycled.

The image shows the Helix Nebula, a bright ring of gas that is located 650 light-years from Earth in the constellation Aquarius.

Resembling a giant human eye, its familiar ring formed from material expelled by a star near the end of its life. The remnant of that star, a white dwarf, lies at the nebula’s centre.

Astronomers trained the Modular Optical Telephoto Hyperspectral Robotic Array (MOTHRA) on the nebula while it was still being constructed at the El Sauce Observatory in Chile’s Coquimbo Region.

When complete later this year, MOTHRA will use 1,140 high-end telephoto lenses and filters that function as a giant 4.8-m aperture refractor telescope to detect the extremely faint glow of gas across large swaths of the sky.

In the image above, the MOTHRA data are shown in black and were collected in November 2025 using 190 or so lenses. These have been combined with previous observations made by the Hubble Space Telescope and the Kitt Peak 4 m telescope, which are shown in colour.

The MOTHRA data reveal a collection of 22 complete or partial arc-shaped glowing shock waves on the eastern side of the nebula.

Dubbed bow shocks, the waves resemble those that form in front of a boat moving through water. In the Helix Nebula, mostly invisible clumps of stellar debris dart rapidly through the thin gas among stars. The glowing bow shocks mark where those clumps collided with the surrounding gas.

By studying the image, astronomers traced the star’s debris as it is stripped, broken apart and gradually mixed into interstellar space.

“We are seeing material shed near the end of a star’s life being broken apart and returned to the galaxy,” notes Yale University astronomer Pieter van Dokkum, who led the study. “That handoff – from recognizable stellar debris to the diffuse gas between the stars – has been very difficult to observe.”

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Researchers in the US have proposed a new metric to determine the economic viability of future fusion power plants. The measure is similar to one used by fusion researchers to ascertain the output of fusion reactions, which is known as the Q factor.

Nuclear fusion, which powers the stars, involves two light nuclei binding to form a heavier nucleus, releasing huge amounts of energy in the process. Harnessing fusion on Earth using the hydrogen isotopes deuterium and tritium could lead to an environmentally friendly and almost limitless energy source.

In the 1950s, the engineer and physicist John Lawson laid out what became known as the “Lawson criterion” for fusion. It describes the combinations of temperature, plasma density and energy confinement time that can produce net energy from the plasma due to fusion, regardless of its absolute power or volume.

Specifically it calculates a factor known as “plasma Q”, which is the ratio of fusion power produced to the external power required to sustain the plasma, with a Q = 1 meaning break-even.

When it comes to magnetic confinement, in which magnetic fields are used to contain a high-temperature plasma, the Joint European Torus based in Oxfordshire, UK, which ended experiments in 2024, achieved a Q of 0.67 in 1997.

The ITER experimental fusion reactor, which is currently being built in Cadarache, France, aims to have a Q of 10 when fully operational towards the end of the 2030s.

Developments in industry have also sped up in recent years and just last month the Fusion Industry Association released a report finding that private fusion companies raised almost $4.5bn in funding over the past year – a 70% increase over the previous year.

The report discovered that 71% of the 65 companies surveyed expect the first fusion plant to deliver commercial electricity by the 2030s. Others, however, remain unconvinced that fusion will soon be a viable energy source.

With that in mind, researchers are now proposing a framework for understanding what is required to make fusion energy commercially viable in the marketplace.

While the costs of basic experiments can be easily documented, estimating the costs of a fusion reactor is somewhat more challenging.

“It’s challenging to reduce complex scientific and engineering requirements to economic consequences,” says economist Andrew Lo from the Massachusetts Institute of Technology (MIT), who co-authored the new study (J. Fusion Energy 45 49). “But if we don’t do that, we’re not going to get the funding we need to achieve the impact we want.”

A new ‘Q’

The new framework includes 10 parameters that evaluate the economic viability of a fusion energy power plant. Some of these are scientific and physical, dealing with the energy consumed and produced in a given plant.

Other parameters are based on engineering and economics, such as the costs of plant construction, returns from invested capital, the efficiency of converting fusion power into an economic product as well as the durability of components used in the energy conversion.

The “economic Q” is then given as the ratio of capital gained to that expended.

MIT nuclear engineer Dennis Whyte, who also co-authored the study, says that the framework is about what it takes to achieve a net-positive economic return with the economic Q needing to be greater than 1 for basic viability.

Whyte, who was yesterday appointed chief executive of the United Kingdom Atomic Energy Authority, adds that the parameters do not depend on the size of the reactor being built, so any inputs can be scaled to a given project or power output.

“When you’ve got a framework to evaluate it in a quantitative way, it tells you about the literal worth of making a particular design decision,” adds Whyte. “That seems to me at this moment of fusion development absolutely critical, and what we’ve been missing.”

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