V1674 Herculis is a classical nova hosted by a white dwarf and dwarf companion and is currently the fastest classical nova on record. While studying V1674Her with the VLBA, Montana Williams, a graduate student at New Mexico Tech who is leading the investigation into the VLBA properties of this nova, confirmed the unexpected: non-thermal emission coming from it. This data is important because it tells Williams and her collaborators a lot about what’s happening in the system. What the team has found is anything but the simple heat-induced explosions scientists previously expected from classical novae.

“Classical novae have historically been considered simple explosions, emitting mostly thermal energy,” said Williams. “However, based on recent observations with the Fermi Large Area Telescope, this simple model is not entirely correct. Instead, it seems they’re a bit more complicated. Using the VLBA, we were able to get a very detailed picture of one of the main complications, the non-thermal emission.”

Very long baseline interferometry (VLBI) detections of classical novae with dwarf companions like V1674Her are rare. They’re so rare, in fact, that this same type of detection, with resolved radio synchrotron components, has been reported just one other time to date. That’s partly because of the assumed nature of classical novae.

“VLBI detections of novae are only recently becoming possible because of improvements to VLBI techniques, most notably the sensitivity of the instruments and the increasing bandwidth or the amount of frequencies we can record at a given time,” said Williams. “Additionally, because of the previous theory of classical novae they weren’t thought to be ideal targets for VLBI studies. We now know this isn’t true because of multi-wavelength observations which indicate a more complex scenario.”

That rarity makes the team’s new observations an important step in understanding the hidden lives of classical novae and what ultimately leads to their explosive behavior.

“By studying images from the VLBA and comparing them to other observations from the Very Large Array (VLA), Fermi-LAT, NuSTAR, and NASA-Swift, we can determine what might be the cause of the emission and also make adjustments to the previous simple model,” said Williams. “Right now, we’re trying to determine if the non-thermal energy is coming from clumps of gas running into other clumped gas which produces shocks, or something else.”

Because Fermi-LAT and Nu-Star observations had already indicated that there might be non-thermal emission coming from V1674Her, that made the classical nova an ideal candidate for study because Williams and her collaborators are on a mission to either confirm or deny those types of findings. It was also more interesting, or cute, as Williams puts it, because of its hyper-fast evolution, and because, unlike supernovae, the host system isn’t destroyed during that evolution, but rather, remains almost completely intact and unchanged after the explosion. “Many astronomical sources don’t change much over the course of a year or even 100 years. But this nova got 10,000 times brighter in a single day, then faded back to its normal state in just about 100 days,” she said. “Because the host systems of classical novae remain intact they can be recurrent, which means we might see this one erupt, or cutely explode, again and again, giving us more opportunities to understand why and how it does.”

The National Radio Astronomy Observatory (NRAO) is a major facility of the National Science Foundation (NSF) operated under cooperative agreement by Associated Universities, Inc.

Now, a new Cornell University-led study measures methane and carbon dioxide emissions from 30 small lakes and ponds (one acre or less) in temperate areas of Europe and North America, revealing that the smallest and shallowest bodies of water exhibit the greatest variability over time.

The paper marks an important step toward calibrating climate models so they better predict emissions from inland waterbodies, and it points to the need to study small waterbodies more closely.

“This study helps understand both the drivers of greenhouse gas concentrations, and importantly, what makes some ponds more variable in their concentrations,” said Meredith Holgerson, assistant professor of ecology and evolutionary biology and senior author of the study, published in the journal Limnology and Oceanography.

“The paper points to patterns across a broad geographic range, such that we can actually get in and predict which waterbodies are going to vary and will be most variable, and it confirms that we need to go out and sample frequently,” said Nicholas Ray, a postdoctoral researcher in Holgerson’s lab and the paper’s first author.

Holgerson and colleagues have previously estimated that shallow lakes and ponds may contribute 5% of the global methane emissions to the atmosphere. But without accurate measurements across many water bodies, they said, the true number could be as little as half or as much as twice that percentage.

While some small lakes and ponds emit greenhouse gasses in consistent, predictable amounts, others are highly variable. Understanding these dynamics is important as carbon dioxide and methane act as greenhouse gases in the atmosphere, with methane being 25 times more potent at trapping heat than carbon dioxide.

Each body of water analyzed was sampled over the 2018 and 2019 summers at three times in three locations, including the deepest point and then two locations on opposite ends (but not too close to the shore).

“One key result we found was that the smaller the system is, in regard to surface area, the higher emissions are likely to be,” Ray said.

For carbon dioxide, samples were consistent in all parts of the waterbody, which revealed that researchers likely only needed to collect a sample from one location to get an accurate prediction of the whole body of water. Methane, on the other hand, required samples from multiple locations to get an accurate measure. Also, for methane, shallower systems were more variable, suggesting stratification of the water column in deeper water may prevent gases from rising to the surface.

For carbon dioxide, the amount of plant life in the water played a large role in variability over time. For methane, variability was more driven by the water depth and likely associated with stratification in the water column.

Among other uses, the study sets the groundwork for informing a New York state climate mitigation strategy to build more ponds to help farmers better handle droughts.

“We’re working to identify how ponds can be built, or if there are simple management strategies people can employ, to minimize emissions,” Ray said.

This easy-to-make sponge-jamming device can help stiff robots handle delicate items carefully by mimicking the nuanced touch, or variable stiffness, of a human.

Robots can skip, jump and do somersaults, but they’re too rigid to hold an egg easily. Variable-stiffness devices are potential solutions for contact compliance on hard robots to reduce damage, or for improving the load capacity of soft robots.

This study, published at the IEEE International Conference on Robotics and Automation (ICRA) 2023, shows that variable stiffness can be achieved by a silicone sponge.

Lead author Tianqi Yue from Bristol’s Department of Engineering Mathematics explained: “Stiffness, also known as softness, is important in contact scenarios.

“Robotic arms are too rigid so they cannot make such a soft human-like grasp on delicate objects, for example, an egg.

“What makes humans different from robotic arms is that we have soft tissues enclosing rigid bones, which act as a natural mitigating mechanism.

“In this paper, we managed to develop a soft device with variable stiffness, to be mounted on the end robotic arm for making the robot-object contact safe.”

Silicone sponge is a cheap and easy-to-fabricate material. It is a porous elastomer just like the cleaning sponge used in everyday tasks.

By squeezing the sponge, the sponge stiffens which is why it can be transformed into a variable-stiffness device.

This device could be used in industrial robots in scenarios including gripping jellies, eggs and other fragile substances. It can also be used in service robots to make human-robot interaction safer.

Mr Yue added: “We managed to use a sponge to make a cheap and nimble but effective device that can help robots achieve soft contact with objects. The great potential comes from its low cost and light weight.

“We believe this silicone-sponge based variable-stiffness device will provide a novel solution in industry and healthcare, for example, tunable-stiffness requirement on robotic polishing and ultrasound imaging.”

The team will now look at making the device achieve variable stiffness in multiple directions, including rotation.