Trans-Neptunian objects (TNOs) are small icy bodies that orbit the Sun beyond Neptune. Binary TNOs occur when two of these objects orbit each other while together or-biting the Sun. Leiva and Buie discovered two objects in a particularly close gravitational configuration. The pair was detected using a stellar occultation, which occurs when an object passes between Earth and a distant star which hides, or “occults,” the star from view. Observers located in the path of the object’s shadow can record the star blinking out and reappearing. The length of time that the object blocks the starlight can be used to determine its size.

“In this instance, the occulted star also turned out to be a binary system. Binary stars are not unusual and binary objects are not unusual,” Buie said. “But it is unusual that we had a binary TNO occulting a binary star.”

“What’s also interesting and unusual is this object’s characteristics,” Leiva said. “The two components are quite close, only 350 kilometers apart. Most binary TNOs are very separated, usually 1,000 kilometers or more. This closeness makes this type of binary TNO difficult to detect with other methods, which is what RECON was designed to accomplish.”

The discovery of the new TNO was made possible by RECON, a collection of 56 observation stations stretching from Yuma, Arizona, to Orville, Washington. The NSF-funded project provides each station with an array of observation equipment, including 11-inch telescopes. High school teachers are trained by Leiva, Buie and Fiske Planetarium Director Dr. John Keller to operate the stations and observe occultations so they can then teach students how to make the same observations. RECON has seen several students go on to do research related to their observations in college.

“To me this project is citizen science at its best,” Buie said. “They’re learning as well as making observations and helping to collect data. If they didn’t do this, we wouldn’t learn about these objects.”

RECON stations are commonly placed in small communities along an ideal line, from the southern to the northern border of the United States, for observation of stellar occultations. Eight additional stations were established in Canada in 2018 by colleagues of Leiva and Buie.

Going forward, Leiva and Buie will continue to search for previously unobserved TNOs, with the aim of discovering whether close binaries are common or unusual in our Solar System.

“Most models of the Solar System indicate that binaries are very common, particularly close binaries like this one,” Leiva said. “If you have an accurate measurement of how common they are, you can fine tune these models.”

“Our overarching aim is to know how common close binary TNOs are,” Buie said. “Is this object one in a million or just like 90% of them? This is fueling our knowledge for building better models of how the Solar System formed.”

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“The 3D finger vein biometric authentication method we developed enables levels of specificity and anti-spoofing that were not possible before,” said Jun Xia, from University at Buffalo, The State University of New York, research team leader. “Since no two people have exactly the same 3D vein pattern, faking a vein biometric authentication would require creating an exact 3D replica of a person’s finger veins, which is basically not possible.”

In the Optical Society (OSA) journal Applied Optics, the researchers describe their new approach, which represents the first time that photoacoustic tomography has been used for 3D finger vein biometric authentication. Tests of the method on people showed that it can correctly accept or reject an identity 99 percent of the time.

“Due to the COVID-19 pandemic, many jobs and services are now performed remotely,” said research team member Giovanni Milione, from NEC Laboratories America, Inc. “Because our technique detects invisible features in 3D, it could be used to enable better authentication techniques to protect personnel data and sensitive documents.”

Adding depth information

Although other biometric authentication approaches based on finger veins have been developed, they are all based on 2D images. The additional depth from a 3D image increases security by making it more difficult to fake an identity and less likely that the technique will accept the wrong person or reject the right one.

To accomplish 3D biometric authentication using the veins in a person’s fingers, the researchers turned to photoacoustic tomography, an imaging technique that combines light and sound. First, light from a laser is used to illuminate the finger. If the light hits a vein, it creates a sound much in the same way that a grill creates a “poof” sound when it is first lit. The system then detects that sound with an ultrasound detector and uses it to reconstruct a 3D image of the veins.

“It has been challenging to use photoacoustic tomography for 3D finger vein biometric authentication because of the bulky imaging system, small field of view and inconvenient positioning of the hand,” said Xia. “We addressed these issues in the new system design through a better combination of light and acoustic beams and custom-made transducers to improve the imaging field of view.”

Designing a practical system

To better integrate light illumination and acoustic detection, the researcher fabricated a new light- and acoustic-beam combiner. They also designed an imaging window that allows the hand to be naturally placed on the platform, similar to a full-size fingerprint scanner. Another critical development was a new matching algorithm, developed by Wenyao Xu from the Computer science and Engineering department that allows biometric identification and matching of features in 3D space.

The researchers tested their new system with 36 people by imaging their four left and four right fingers. The tests showed that the approach was not only feasible but also accurate, especially when multiple fingers were used.

“We envision this technique being used in critical facilities, such as banks and military bases, that require a high level of security,” said Milione. “With further miniaturization 3D vein authentication could also be used in personal electronics or be combined with 2D fingerprints for two-factor authentication.”

The researchers are now working to make the system even smaller and to reduce the imaging time to less than one second. They note that it should be possible to implement the photoacoustic system in smartphones since ultrasound systems have already been developed for use in smartphones. This could enable portable or wearable systems that perform biometric authentication in real time.

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Secondary forests — areas of new forest growing on land that has previously been deforested — form a key part of policies aiming to tackle net carbon emissions and mitigate climate change.

In 2017 there were nearly 130,000 square kilometres of secondary forest in the Brazilian Amazon — roughly equivalent to the size of England.

Despite their scale and importance for climate targets, our understanding of their contribution to the tropical carbon balance is incomplete. It was not clear to what extent carbon emissions from deforestation have been offset by secondary forest growth, or how this has varied over time.

A new study by an international team of researchers from the UK and Brazil, published by Global Change Biology, used open source MapBiomas data to map the age, extent and carbon stock of secondary forests across the Brazilian Amazon between 1986 and 2017.

After calculating how much carbon had been lost through deforestation, the scientists discovered that, in more than 30 years, the regrowth of secondary forests in the Brazilian Amazon has offset less than 10 per cent of emissions from the loss of old-growth forests.

Charlotte Smith, a PhD researcher at Lancaster University and lead author of the study, said: “Secondary forests have an incredible potential to store large quantities of carbon. However, it takes a long time for them to build this carbon stock, so without a drastic decline in the rate of deforestation their environmental benefits will continue to be undermined.”

Despite a fifth of deforested land now being covered in secondary forest, the researchers found that most secondary forests are relatively young — more than 85 per cent are younger than 20 years old and almost half (42 per cent) are less than five years old.

This is because secondary forests are also subject to deforestation. Areas of land have been repeatedly deforested — thus limiting secondary forests’ effectiveness as a carbon store. “Of all the secondary forest mapped over the 32-year period, 60 per cent had been deforested again by 2017,” said Charlotte.

The researchers then looked at other factors known to affect secondary forest growth and carbon up-take, such as climate, landscape and proximity to old-growth forests, which can act as a source of seeds.

They found that the majority of secondary forests are situated far from primary forests, in the drier parts of the Amazon. These factors suggest they will be relatively poor for taking-up carbon.

The findings highlight that halting deforestation, particularly of old-growth forest, is essential and that secondary forest growth alone is not sufficient to control carbon emissions in the Amazon.

Co-author, Professor Jos Barlow, said: “Although secondary forests could be an important part of the solution to climate change, it is also important not to overstate their relevance. Deforestation rates in the Brazilian Amazon surpassed 10,000km2 last year, and will almost certainly surpass that in 2020.”

The researchers hope that these results will help inform policies and management proposals that can mitigate climate change more effectively. “We show that preventing further deforestation remains the most urgent priority to mitigate climate change,” said Charlotte.

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