The research, to be published May 12 in the journal Science Advances, pegs the age of Saturn’s rings at no more than 400 million years old. That makes the rings much younger than Saturn itself, which is about 4.5 billion years old.

“In a way, we’ve gotten closure on a question that started with James Clerk Maxwell,” said Kempf, associate professor in the Laboratory for Atmospheric and Space Physics (LASP) at CU Boulder.

The researchers arrived at that closure by studying what might seem like an unusual subject: dust.

Kempf explained that tiny grains of rocky material wash through Earth’s solar system on an almost constant basis. In some cases, this flux can leave behind a thin layer of dust on planetary bodies, including on the ice that makes up Saturn’s rings.

In the new study, he and his colleagues set out to put a date on Saturn’s rings by studying how rapidly this layer of dust builds up — a bit like telling how old a house is by running your finger along its surfaces.

“Think about the rings like the carpet in your house,” Kempf said. “If you have a clean carpet laid out, you just have to wait. Dust will settle on your carpet. The same is true for the rings.”

It was an arduous process: From 2004 to 2017, the team used an instrument called the Cosmic Dust Analyzer aboard NASA’s late Cassini spacecraft to analyze specks of dust flying around Saturn. Over those 13 years, the researchers collected just 163 grains that had originated from beyond the planet’s close neighborhood. But it was enough. Based on their calculations, Saturn’s rings have likely been gathering dust for only a few hundred million years.

The planet’s rings, in other words, are new phenomena, arising (and potentially even disappearing) in what amounts to a blink of an eye in cosmic terms.

“We know approximately how old the rings are, but it doesn’t solve any of our other problems,” Kempf said. “We still don’t know how these rings formed in the first place.”

From Galileo to Cassini

Researchers have been captivated by these seemingly-translucent rings for more than 400 years. In 1610, Italian astronomer Galileo Galilei first observed the features through a telescope, although he didn’t know what they were. (Galileo’s original drawings make the rings look a bit like the handles on a water jug). In the 1800s, Maxwell, a scientist from Scotland, concluded that Saturn’s rings couldn’t be solid but were, instead, made up of many individual pieces.

Today, scientists know that Saturn hosts seven rings comprised of countless chunks of ice, most no bigger than a boulder on Earth. Altogether, this ice weighs about half as much as Saturn’s moon Mimas and stretches nearly 175,000 miles from the planet’s surface.

Kempf added that for most of the 20th Century, scientists assumed that the rings likely formed at the same time as Saturn.

But that idea raised a few issues — namely, Saturn’s rings are sparkling clean. Observations suggest that these features are made up of roughly 98% pure water ice by volume, with only a tiny amount of rocky matter.

“It’s almost impossible to end up with something so clean,” Kempf said.

Cassini offered an opportunity to put a definitive age on Saturn’s rings. The spacecraft first arrived at Saturn in 2004 and collected data until it purposefully crashed into the planet’s atmosphere in 2017. The Cosmic Dust Analyzer, which was shaped a bit like a bucket, scooped up small particles as they whizzed by.

Engineers and scientists at LASP designed and built a much more sophisticated dust analyzer for NASA’s upcoming Europa Clipper mission, which is scheduled to launch in 2024.

The team estimated that this interplanetary grime would contribute far less than a gram of dust to each square foot of Saturn’s rings every year — a light sprinkle, but enough to add up over time. Previous studies had also suggested that the rings could be young but didn’t include definitive measures of dust accumulation.

Stroke of luck

The rings might already be vanishing. In a previous study, NASA scientists reported that the ice is slowly raining down onto the planet and could disappear entirely in another 100 million years.

That these ephemeral features existed at a time when Galileo and the Cassini spacecraft could observe them seems almost too good to be true, Kempf said — and it begs an explanation for how the rings formed in the first place. Some scientists, for example, have posited that Saturn’s rings may have formed when the planet’s gravity tore apart one of its moons.

“If the rings are short lived and dynamical, why are we seeing them now?” he said. “It’s too much luck.”

Co-authors on the new study include Nicolas Altobelli of the European Space Agency; Jürgen Schmidt of the Freie Universität Berlin; Jeffrey Cuzzi and Paul Estrada of the NASA Ames Research Center; and Ralf Srama of the Universität Stuttgart.

The explosion is more than ten times brighter than any known supernova (exploding star) and three times brighter than the brightest tidal disruption event, where a star falls into a supermassive black hole.

The explosion, known as AT2021lwx, has currently lasted over three years, compared to most supernovae which are only visibly bright for a few months. It took place nearly 8 billion light years away, when the universe was around 6 billion years old, and is still being detected by a network of telescopes.

The researchers believe that the explosion is a result of a vast cloud of gas, possibly thousands of times larger than our sun, that has been violently disrupted by a supermassive black hole. Fragments of the cloud would be swallowed up, sending shockwaves through its remnants, as well as into a large dusty ‘doughnut’ surrounding the black hole. Such events are very rare and nothing on this scale has been witnessed before.

Last year, astronomers witnessed the brightest explosion on record — a gamma-ray burst known as GRB 221009A. While this was brighter than AT2021lwx, it lasted for just a fraction of the time, meaning the overall energy released by the AT2021lwx explosion is far greater.

The findings of the research have been published today [Friday, 12 May 2023] in Monthly Notices of the Royal Astronomical Society.

Discovery

AT2021lwx was first detected in 2020 by the Zwicky Transient Facility in California, and subsequently picked up by the Asteroid Terrestrial-impact Last Alert System (ATLAS) based in Hawaii. These facilities survey the night sky to detect transient objects that rapidly change in brightness indicating cosmic events such as supernovae, as well as finding asteroids and comets. Until now the scale of the explosion has been unknown.

“We came upon this by chance, as it was flagged by our search algorithm when we were searching for a type of supernova,” says Dr Philip Wiseman, Research Fellow at the University of Southampton, who led the research. “Most supernovae and tidal disruption events only last for a couple of months before fading away. For something to be bright for two plus years was immediately very unusual.”

The team investigated the object further with several different telescopes: the Neil Gehrels Swift Telescope (a collaboration between NASA, the UK and Italy), the New Technology Telescope (operated by the European Southern Observatory) in Chile, and the Gran Telescopio Canarias in La Palma, Spain.

Measuring the explosion

By analysing the spectrum of the light, splitting it up into different wavelengths and measuring the different absorption and emission features of the spectrum, the team were able to measure the distance to the object.

“Once you know the distance to the object and how bright it appears to us, you can calculate the brightness of the object at its source. Once we’d performed those calculations, we realised this is extremely bright,” says Professor Sebastian Hönig from the University of Southampton, a co-author of the research.

The only things in the universe that are as bright as AT2021lwx are quasars — supermassive black holes with a constant flow of gas falling onto them at high velocity.

Professor Mark Sullivan, also of the University of Southampton and another co-author of the paper, explains: “With a quasar, we see the brightness flickering up and down over time. But looking back over a decade there was no detection of AT2021lwx, then suddenly it appears with the brightness of the brightest things in the universe, which is unprecedented.”

What caused the explosion?

There are different theories as to what could have caused such an explosion, but the Southampton-led team believe the most feasible explanation is an extremely large cloud of gas (mostly hydrogen) or dust that has come off course from its orbit around the black hole and been sent flying in.

The team are now setting out to collect more data on the explosion — measuring different wavelengths, including X-rays which could reveal the object’s surface and temperature, and what underlying processes are taking place. They will also carry out upgraded computational simulations to test if these match their theory of what caused the explosion.

Dr Philip Wiseman added: “With new facilities, like the Vera Rubin Observatory’s Legacy Survey of Space and Time, coming online in the next few years, we are hoping to discover more events like this and learn more about them. It could be that these events, although extremely rare, are so energetic that they are key processes to how the centres of galaxies change over time.”

Research lead Dr Elisa Girola from UQ’s Faculty of Science said this quirk of whale evolution could have consequences for breeding and behaviour.

“Humpback whales evolved over millions of years with noise from natural sources but noise from human-made vessels is foreign to their instincts,” Dr Girola said.

“It’s a surprising finding given engine noise has a similar frequency range to the wind.

“It’s possible the whales are picking out other differences such as wind noise being broadband and the same over large areas, while vessel noise is generated by a single-point source with specific peaks in frequency.

“We don’t know yet if this lack of response to boat noise is making whales communicate less effectively or making breeding practices more difficult.

“Male humpback whale singing is probably used to mediate reproductive interactions, but we can’t say if vessel noise is interfering.”

The audio data for the study was collected in late 2010 off Peregian Beach in Queensland, during the whales’ southward migration from breeding grounds in the lagoon of the Great Barrier Reef to feeding grounds in Antarctica.

Whale songs were recorded using an acoustic array of five hydrophone buoys, which sent signals back to the beach.

A 19-metre fishing boat was introduced to produce vessel noise.

The researchers say it is possible that humpback whales are using other strategies to compensate for vessel noise.

“Even with a 19-metre boat making a racket, the whales just didn’t sing any louder,” Dr Girola said.

“There are a few things going on — they might be using ‘spatial release from masking’, which is the ability to discriminate between audio signals coming from different directions.

“Or there’s ‘comodulation release from masking’ which is the ability to discriminate between signal and noise when the noise has distinctive frequency components and at least some of these components are not overlapping with the signal.

“There’s still so much more research to be done.

“Understanding humpback whales’ response to noise is important for developing mitigation policies for human activities at sea.

“I’m sure these beautiful, mysterious creatures will continue to surprise and amaze us.”

Because problems such asanxiety, depression and bipolar disorders can emerge in late adolescence and early adulthood, a better understanding of brain development may help clinicians offer therapies to treat these disorders.

“A fundamental understanding of the developmental trajectory of brain circuitry may help identify sensitive periods of development when doctors could offer therapies to their patients,” says Dora Hermes, Ph.D., a Mayo Clinic biomedical engineer and senior author of the study.

Called the human connectome, the structural system of neural pathways in the brain or nervous system develops as people age. But how structural changes affect the speed of neuronal signaling has not been well described.

“Just as transit time for a truck would depend on the structure of the road, so does the transmission speed of signals among brain areas depend on the structure of neural pathways,” Dr. Hermes explains. “The human connectome matures during development and aging, and can be affected by disease. All these processes may affect the speed of information flow in the brain. “In the study, Dr. Hermes and colleagues stimulated pairs of electrodes with a brief electrical pulse to measure the time it took signals to travel among brain regions in 74 research participants between the ages of 4 and 51. The intracranial measurements were done in a small population of patients who had electrodes implanted for epilepsy monitoring at University Medical Center Utrecht, Netherlands.

The response delays in connected brain regions showed that transmission speeds in the human brain increase throughout childhood and even into early adulthood. They plateau around 30 to 40 years of age.

The team’s data indicate that adult transmission speeds were about two times faster compared to those typically found in children. Transmission speeds also were typically faster in 30- or 40-year-old subjects compared to teenagers.

Brain transmission speed is measured in milliseconds, a unit of time equal to one-thousandth of a second. For example, the researchers measured the neuronal speed of a 4-year-old patient at 45 milliseconds for a signal to travel from the frontal to parietal regions of the brain. In a 38-year-old patient, the same pathway was measured at 20 milliseconds. For comparison, the blink of an eye takes about 100 to 400 milliseconds.

The researchers are working to characterize electrical stimulation-driven connectivity in the human brain. One of the next steps is to better understand how transmission speeds change with neurological diseases. They are collaborating with pediatric neurosurgeons and neurologists to understand how diseases change transmission speeds compared to what would be considered within the normal range for a certain age group.

The research is supported by the National Institute of Mental Health of the National Institutes of Health (R01MH122258).

The results have set the stage for revealing exciting novel insights about the Universe’s earliest moments.

The inflationary period, which occurred just after the Big Bang, is believed to have caused the Universe to expand exponentially. In many cosmological theories, the rapid expansion period is followed by the formation of oscillons. Oscillons are a type of localized non-linear massive structure that can form from fields, such as the inflaton field, which are oscillating at high frequencies. These structures can persist for long periods, and as the researchers found, their eventual decay can generate a significant amount of gravitational waves, which are ripples in space-time.

In their study, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Project Researcher Kaloian D. Lozanov, and Kavli IPMU Visiting Associate Scientist, International Center for Quantum-field Measurement Systems for Studies of the Universe and Particles (QUP) Senior Scientist, and High Energy Accelerator Research Organization (KEK) Theory Center Assistant Professor Volodymyr Takhistov, simulated the evolution of the inflaton field during the early Universe and found that oscillons were indeed present. They then found that oscillon decay was able to generate gravitational waves that would be detectable by upcoming gravitational wave observatories.

The findings provide a novel test of the early Universe dynamics independent of the conventionally studied cosmic microwave background radiation. The discovery of these gravitational waves would establish a new window into the Universe’s earliest moments, and could help shed light on some of the pressing fundamental questions in cosmology.

With the ongoing development of gravitational wave detectors and supercomputing resources, we can expect to gain even more insights into the Universe’s early moments in the coming years. Overall, the new study demonstrates the power of combining theoretical models with advanced computational techniques and observations to uncover new insights into the Universe’s evolution.

Details of their study were published in Physical Review Letters on May 2.