Scientists regenerate neurons in mice with spinal cord injury and optic nerve damage

Neuron illustration

Like power lines in an electrical grid, long wiry projections that grow outward from neurons -- structures known as axons -- form interconnected communication networks that run from the brain to all parts of the body. But unlike an outage in a power line, which can be fixed, a break in an axon is permanent. Each year thousands of patients confront this reality, facing life-long losses in sensation and motor function from spinal cord injury and related conditions in which axons are badly damaged or severed.

New research by scientists at the Lewis Katz School of Medicine Temple University (LKSOM) shows, however, that gains in functional recovery from these injuries may be possible, thanks to a molecule known as Lin28, which regulates cell growth. In a study published online in the journal Molecular Therapy, the Temple researchers describe the ability of Lin28 -- when expressed above its usual levels -- to fuel axon regrowth in mice with spinal cord injury or optic nerve injury, enabling repair of the body's communication grid.

"Our findings show that Lin28 is a major regulator of axon regeneration and a promising therapeutic target for central nervous system injuries," explained Shuxin Li, MD, PhD, Professor of Anatomy and Cell Biology and in the Shriners Hospitals Pediatric Research Center at the Lewis Katz School of Medicine at Temple University and senior investigator on the new study. The research is the first to demonstrate the regenerative ability of Lin28 upregulation in the injured spinal cord of animals.

"We became interested in Lin28 as a target for neuron regeneration because it acts as a gatekeeper of stem cell activity," said Dr. Li. "It controls the switch that maintains stem cells or allows them to differentiate and potentially contribute to activities such as axon regeneration."

To explore the effects of Lin28 on axon regrowth, Dr. Li and colleagues developed a mouse model in which animals expressed extra Lin28 in some of their tissues. When full-grown, the animals were divided into groups that sustained spinal cord injury or injury to the optic nerve tracts that connect to the retina in the eye.

Another set of adult mice, with normal Lin28 expression and similar injuries, were given injections of a viral vector (a type of carrier) for Lin28 to examine the molecule's direct effects on tissue repair.

Extra Lin28 stimulated long-distance axon regeneration in all instances, though the most dramatic effects were observed following post-injury injection of Lin28. In mice with spinal cord injury, Lin28 injection resulted in the growth of axons to more than three millimeters beyond the area of axon damage, while in animals with optic nerve injury, axons regrew the entire length of the optic nerve tract. Evaluation of walking and sensory abilities after Lin28 treatment revealed significant improvements in coordination and sensation.

"We observed a lot of axon regrowth, which could be very significant clinically, since there currently are no regenerative treatments for spinal cord injury or optic nerve injury," Dr. Li explained.

One of his goals in the near-term is to identify a safe and effective means of getting Lin28 to injured tissues in human patients. To do so, his team of researchers will need to develop a vector, or carrier system for Lin28, that can be injected systemically and then hone in on injured axons to deliver the therapy directly to multiple populations of damaged neurons.

Dr. Li further wants to decipher the molecular details of the Lin28 signaling pathway. "Lin28 associates closely with other growth signaling molecules, and we suspect it uses multiple pathways to regulate cell growth," he explained. These other molecules could potentially be packaged along with Lin28 to aid neuron repair.

Read more at Science Daily

Mind-controlled arm prostheses that 'feel' are now a part of everyday life

Touch definition

For the first time, people with arm amputations can experience sensations of touch in a mind-controlled arm prosthesis that they use in everyday life. A study in the New England Journal of Medicine reports on three Swedish patients who have lived, for several years, with this new technology -- one of the world's most integrated interfaces between human and machine.

The advance is unique: the patients have used a mind-controlled prosthesis in their everyday life for up to seven years. For the last few years, they have also lived with a new function -- sensations of touch in the prosthetic hand. This is a new concept for artificial limbs, which are called neuromusculoskeletal prostheses -- as they are connected to the user's nerves, muscles, and skeleton.

The research was led by Max Ortiz Catalan, Associate Professor at Chalmers University of Technology, in collaboration with Sahlgrenska University Hospital, University of Gothenburg, and Integrum AB, all in Gothenburg, Sweden. Researchers at Medical University of Vienna in Austria and the Massachusetts Institute of Technology in the USA were also involved.

"Our study shows that a prosthetic hand, attached to the bone and controlled by electrodes implanted in nerves and muscles, can operate much more precisely than conventional prosthetic hands. We further improved the use of the prosthesis by integrating tactile sensory feedback that the patients use to mediate how hard to grab or squeeze an object. Over time, the ability of the patients to discern smaller changes in the intensity of sensations has improved," says Max Ortiz Catalan.

"The most important contribution of this study was to demonstrate that this new type of prosthesis is a clinically viable replacement for a lost arm. No matter how sophisticated a neural interface becomes, it can only deliver real benefit to patients if the connection between the patient and the prosthesis is safe and reliable in the long term. Our results are the product of many years of work, and now we can finally present the first bionic arm prosthesis that can be reliably controlled using implanted electrodes, while also conveying sensations to the user in everyday life," continues Max Ortiz Catalan.

Since receiving their prostheses, the patients have used them daily in all their professional and personal activities.

The new concept of a neuromusculoskeletal prosthesis is unique in that it delivers several different features which have not been presented together in any other prosthetic technology in the world:

• It has a direct connection to a person's nerves, muscles, and skeleton.
• It is mind-controlled and delivers sensations that are perceived by the user as arising from the missing hand.
• It is self-contained; all electronics needed are contained within the prosthesis, so patients do not need to carry additional equipment or batteries.
• It is safe and stable in the long term; the technology has been used without interruption by patients during their everyday activities, without supervision from the researchers, and it is not restricted to confined or controlled environments.

The newest part of the technology, the sensation of touch, is possible through stimulation of the nerves that used to be connected to the biological hand before the amputation. Force sensors located in the thumb of the prosthesis measure contact and pressure applied to an object while grasping. This information is transmitted to the patients' nerves leading to their brains. Patients can thus feel when they are touching an object, its characteristics, and how hard they are pressing it, which is crucial for imitating a biological hand.

"Currently, the sensors are not the obstacle for restoring sensation," says Max Ortiz Catalan. "The challenge is creating neural interfaces that can seamlessly transmit large amounts of artificially collected information to the nervous system, in a way that the user can experience sensations naturally and effortlessly."

The implantation of this new technology took place at Sahlgrenska University Hospital, led by Professor Rickard Brånemark and Doctor Paolo Sassu. Over a million people worldwide suffer from limb loss, and the end goal for the research team, in collaboration with Integrum AB, is to develop a widely available product suitable for as many of these people as possible.

"Right now, patients in Sweden are participating in the clinical validation of this new prosthetic technology for arm amputation," says Max Ortiz Catalan. "We expect this system to become available outside Sweden within a couple of years, and we are also making considerable progress with a similar technology for leg prostheses, which we plan to implant in a first patient later this year."

More about: How the technology works

The implant system for the arm prosthesis is called e-OPRA and is based on the OPRA implant system created by Integrum AB. The implant system anchors the prosthesis to the skeleton in the stump of the amputated limb, through a process called osseointegration (osseo = bone). Electrodes are implanted in muscles and nerves inside the amputation stump, and the e-OPRA system sends signals in both directions between the prosthesis and the brain, just like in a biological arm.

The prosthesis is mind-controlled, via the electrical muscle and nerve signals sent through the arm stump and captured by the electrodes. The signals are passed into the implant, which goes through the skin and connects to the prosthesis. The signals are then interpreted by an embedded control system developed by the researchers. The control system is small enough to fit inside the prosthesis and it processes the signals using sophisticated artificial intelligence algorithms, resulting in control signals for the prosthetic hand's movements.

The touch sensations arise from force sensors in the prosthetic thumb. The signals from the sensors are converted by the control system in the prosthesis into electrical signals which are sent to stimulate a nerve in the arm stump. The nerve leads to the brain, which then perceives the pressure levels against the hand.

The neuromusculoskeletal implant can connect to any commercially available arm prosthesis, allowing them to operate more effectively.

More about: How the artificial sensation is experienced

People who lose an arm or leg often experience phantom sensations, as if the missing body part remains although not physically present. When the force sensors in the prosthetic thumb react, the patients in the study feel that the sensation comes from their phantom hand. Precisely where on the phantom hand varies between patients, depending on which nerves in the stump receive the signals. The lowest level of pressure can be compared to touching the skin with the tip of a pencil. As the pressure increases, the feeling becomes stronger and increasingly 'electric'.

More about: The research

The current study dealt with patients with above-elbow amputations, and this technology is close to becoming a finished product. The research team is working in parallel with a new system for amputations below the elbow. In those cases, instead of one large bone (humerus), there are two smaller bones (radius and ulna) to which the implant needs to be anchored. The group is also working on adapting the system for leg prostheses.

In addition to applications within prosthetics, the permanent interface between human and machine provides entirely new opportunities for scientific research into how the human muscular and nervous systems work.

Read more at Science Daily

New insight into bacterial structure to help fight against superbugs

Scientists from the University of Sheffield have produced the first high-resolution images of the structure of the cell wall of bacteria, in a study that could further understanding of antimicrobial resistance.

The research, published in Nature, revealed a new and unexpected structure of the outer bacterial layers of the bacterium Staphylococcus aureus.

The findings set a new framework for understanding how bacteria grow and how antibiotics work, overturning previous theories about the structure of the outer bacterial layers.

The images give unprecedented insight into the composition of the bacterial cell wall and will inform new approaches to developing antibiotics in order to combat antibiotic resistance. There are no other examples of studies of the cell wall in any organism at comparable resolution, down to the molecular scale.

Laia Pasquina Lemonche, a PhD Researcher from the University of Sheffield's Department of Physics and Astronomy, said: "Many antibiotics work by inhibiting the bacteria's production of a cell wall, a strong but permeable skin around the bacteria which is critical for its survival.

"We still don't understand how antibiotics like penicillin kill bacteria, but this isn't surprising because until now we had remarkably little information about the actual organisation of the bacterial cell wall. This study provides that essential stepping stone which we hope will lead to both a better understanding of how antibiotics work and to the future development of new approaches to combat antimicrobial resistance."

The team used an advanced microscopy technique called Atomic Force Microscopy (AFM), which works by using a sharp needle to feel the shape of a surface and build an image similar to a contour map, but at the scale of individual molecules.

Professor Jamie Hobbs, Professor of Physics at the University of Sheffield, said: "It is by physicists and biologists working together that we've been able to make these breakthroughs in our understanding of the bacterial cell wall."

The researchers are now using the same techniques to understand how antibiotics change the architecture of the cell wall and also how changes in the cell wall are important in antimicrobial resistance.

From Science Daily

A new machine learning method streamlines particle accelerator operations

Each year, researchers from around the world visit the Department of Energy's SLAC National Accelerator Laboratory to conduct hundreds of experiments in chemistry, materials science, biology and energy research at the Linac Coherent Light Source (LCLS) X-ray laser. LCLS creates ultrabright X-rays from high-energy beams of electrons produced in a giant linear particle accelerator.

Experiments at LCLS run around the clock, in two 12-hour shifts per day. At the start of each shift, operators must tweak the accelerator's performance to prepare the X-ray beam for the next experiment. Sometimes, additional tweaking is needed during a shift as well. In the past, operators have spent hundreds of hours each year on this task, called accelerator tuning.

Now, SLAC researchers have developed a new tool, using machine learning, that may make part of the tuning process five times faster compared to previous methods. They described the method in Physical Review Letters on March 25.

Tuning the beam

Producing LCLS's powerful X-ray beam starts with the preparation of a high-quality electron beam. Some of the electrons' energy then gets converted into X-ray light inside special magnets. The properties of the electron beam, which needs to be dense and tightly focused, are a critical factor in how good the X-ray beam will be.

"Even a small difference in the density of the electron beam can have a huge difference in the amount of X-rays you get out at the end," says Daniel Ratner, head of SLAC's machine learning initiative and a member of the team that developed the new technique.

The accelerator uses a series of 24 special magnets, called quadrupole magnets, to focus the electron beam similarly to how glass lenses focus light. Traditionally, human operators carefully turned knobs to adjust individual magnets between shifts to make sure the accelerator was producing the X-ray beam needed for a particular experiment. This process took up a lot of the operators' time -- time they could spend on other important tasks that improve the beam for experiments.

A few years ago, LCLS operators adopted a computer algorithm that automated and sped up this magnet tuning. However, it came with its own disadvantages. It aimed at improving the X-ray beam by making random adjustments to the magnets' strengths. But unlike human operators, this algorithm had no prior knowledge of the accelerator's structure and couldn't make educated guesses in its tuning that might have ultimately led to even better results.

This is why SLAC researchers decided to develop a new algorithm that combines machine learning -- "smart" computer programs that learn how to get better over time -- with knowledge about the physics of the accelerator.

"The machine learning approach is trying to tie this all together to give operators better tools so that they can focus on other important problems," says Joseph Duris, a SLAC scientist who led the new study.

A better beam, faster

The new approach uses a technique called a Gaussian process, which predicts the effect a particular accelerator adjustment has on the quality of the X-ray beam. It also generates uncertainties for its predictions. The algorithm then decides which adjustments to try for the biggest improvements.

For example, it may decide to try a dramatic adjustment whose outcome is very uncertain but could lead to a big payoff. That means this new, adventurous algorithm has a better chance than the previous algorithm of making the tweaks needed to create the best possible X-ray beam.

The SLAC researchers also used data from previous LCLS operations to teach the algorithm which magnet strengths have typically led to brighter X-rays, giving the algorithm a way of making educated guesses about the adjustments it should try. This equips the algorithm with knowledge and expertise that human operators naturally have, and that the previous algorithm lacked.

"We can rely on that physics knowledge, that institutional knowledge, in order to improve the predictions," Duris says.

Insights into the magnets' relationships to each other also improved the technique. The quadrupole magnets work in pairs, and to increase their focusing power, the strength of one magnet in a pair must be increased while the other's is decreased.

With the new process, tuning the quadrupole magnets has become about three to five times faster, the researchers estimate. It also tends to produce higher-intensity beams than the previously used algorithm.

"Our ability to increase our tuning efficiency is really, really critical to being able to deliver a beam faster and with better quality to people who are coming from all over the world to run experiments," says Jane Shtalenkova, an accelerator operator at SLAC who worked with Duris, Ratner and others to develop the new tool.

Beyond LCLS

The same method can be extended to tune other electron or X-ray beam properties that scientists may want to optimize for their experiments. For example, researchers could apply the technique to maximize the signal they get out of their sample after it's hit by LCLS's X-ray beam.

This flexibility also makes the new algorithm useful for other facilities.

Read more at Science Daily

Computational techniques explore 'the dark side of amyloid aggregation in the brain'

As physicians and families know too well, though Alzheimer's disease has been intensely studied for decades, too much is still not known about molecular processes in the brain that cause it. Now researchers at the University of Massachusetts Amherst say new insights from analytic theory and molecular simulation techniques offer a better understanding of amyloid fibril growth and brain pathology.

As senior author Jianhan Chen notes, the "amyloid hypothesis" was promising -- amyloid protein fibrils are a central feature in Alzheimer's, Parkinson's disease and other neurodegenerative diseases. "But the process is really difficult to study," he says. "For many years people thought the fibril might the harmful factor in the brain. But after billions of dollars of investment failed to deliver an Alzheimer's drug, that thinking is really questioned. We now believe that the fibril is not the toxic species, but it's the earlier forms, soluble oligomers or proto-fibrils. That's what we wanted to study."

Chen and first author Zhiguang Jia, a research scientist in Chen's computational biophysics lab, explored how building-block peptides form fibrils. "We are really proud of this work because, to the best of our knowledge, for the first time we have described the comprehensive process of how fibril growth can happen. We illustrate that the effects of disease-causing mutations often arise from the cumulative effects of many small perturbations. A comprehensive description is absolutely critical to generate reliable and testable hypothesis," he adds. Details of their multi-scale approach with many atomistic simulations are in Proceedings of the National Academy of Sciences.

Chen adds, "The process is slow and very complex. All the nonproductive pathways are usually hidden and have never been described in a comprehensive and quantitative fashion. It is like the dark side of the moon."

Chen says their model is "parameter-free and purely based on physics, with no fitting or assumptions needed. We provide a complete description of the process and the physics just comes out naturally. It's really satisfying; we feel it's a real breakthrough."

He and Jia focused first on how peptides in disordered solution behave. The process starts with peptides in a partially unfolded conformation, Chen notes. They describe both productive and non-productive aggregation processes and point out that non-productive ones can take a very long time to disengage from interactions. "It's like hiking in the woods without a path," Chen says. "It's like a maze. And if one peptide takes a mistaken pathway, it has start over and retry many, many times."

A key insight was to account for these many non-productive pathways -- too many possibilities -- that slow movement and cause a "kinetic bottleneck," he says. Another important insight, Chen points out, is that the "energy landscape" as biophysicists call it, is crucial. With "usual" structured proteins, in spite of their great complexity, they fold quickly because the underlying energy landscape is well structured to support quick, efficient folding.

By contrast, fibril growth occurs in a "really flat" energy landscape, he adds. "There are many, many mistakes before you fall into the hole that will lead to fibril formation." Biochemists call it "unguided search," he says, adding that "bumbling" is a good way to describe it.

Modeling and characterizing such unguided systems are extremely difficult, the biophysicist notes. "To use a simulation to predict the process, you need a complete description of the whole maze or you can never grasp it, and this is almost impossible. To describe comprehensively the search space, you must compromise resolution of peptide modeling. When you limit the resolution of the model, you'll not be able to faithfully capture the impacts of disease mutations, for example."

He says these conflicting requirements -- resolution and completeness -- must be satisfied at the same time. "Our approach is the first to satisfy both. This is one of our technical breakthroughs," Chen says.

Read more at Science Daily

Reduced obesity for weighted-vest wearers

Scientists from the University of Gothenburg, Sweden, have found a new method of reducing human body weight and fat mass using weighted vests. The new study indicates that there is something comparable to built-in bathroom scales that contributes to keeping our body weight and, by the same token, fat mass constant.

The researchers hypothesized that loading the vests with weights would result in a compensatory body-weight decrease. Sixty-nine people with a body mass index (BMI) of 30-35, the lowest obesity category, took part in the clinical study. Their instructions were to wear a weighted vest eight hours a day for three weeks, and otherwise live as usual.

All the study participants wore weighted vests but, by drawing of lots, they were assigned to one of two groups. The control group wore only light vests weighing 1 kg, while the treatment group wore heavy vests weighing some 11 kg. When the three weeks had passed, the experimental subjects who wore the heavier vests had lost 1.6 kg in weight, while those wearing the light vests had lost 0.3 kg.

"We think it's very interesting that the treatment with the heavier weighted vests reduced fat mass while muscle mass simultaneously remained intact," says Professor Claes Ohlsson of Sahlgrenska Academy, University of Gothenburg.

"The effect on fat mass we found, from this short experiment, exceeded what's usually observed after various forms of physical training. But we weren't able to determine whether the reduction was in subcutaneous fat (just under the skin) or the dangerous visceral kind (belly fat) in the abdominal cavity that's most strongly associated with cardiovascular diseases and diabetes," says Professor John-Olov Jansson of Sahlgrenska Academy, University of Gothenburg.

In previous animal studies published in 2018, the scientists showed that there is an energy balance system that endeavors to keep body weight constant: the "gravitostat," as they have dubbed it. In mice, this regulation takes place partly by influencing appetite. To work, the system must contain a kind of personal weighing machine. The researchers' new clinical study shows that similar built-in scales exists in humans as well.

If people do a lot of sitting, what seems to happen is that the reading on our personal scales falls too low. This may explain why sitting is so clearly associated with obesity and ill-health. Weighted vests can raise the reading on the scales, resulting in weight loss.

Many questions about how the gravitostat works remain for the researchers to answer. Aspects they want to study include whether, in wearers of weighted vests, changed energy expenditure, appetite and mobility help them to lose weight. The scientists also want to see whether the weight reduction continues for the vest wearers over periods longer than three weeks, and whether the dangerous visceral fat is reduced by the treatment.

From Science Daily

Evidence of Late Pleistocene human colonization of isolated islands beyond Wallace's Line

A new article published in Nature Communications applies stable isotope analysis to a collection of fossil human teeth from the islands of Timor and Alor in Wallacea to study the ecological adaptations of the earliest members of our species to reach this isolated part of the world. Because the Wallacean islands are considered extreme, resource poor settings, archaeologists believed that early seafaring populations would have moved rapidly through this region without establishing permanent communities. Nevertheless, this has so far been difficult to test.

This study, led by scientists from the Department of Archaeology, Max Planck Institute for the Science of Human History (MPI SHH), alongside colleagues from the Australian National University and Universitas Gadjah Mada, used an isotopic methodology that reveals the resources consumed by humans during the period of tooth formation. They demonstrate that the earliest human fossil so far found in the region, dating to around 42,000-39,000 years ago, relied upon coastal resources. Yet, from 20,000 years ago, humans show an increasing reliance on tropical forest environments, away from the island coasts. The results support the idea that one distinguishing characteristic of Homo sapiens is high ecological flexibility, especially when compared to other hominins known from the same region.

Pleistocene hominin adaptations in Southeast Asia

Over the last two decades, archaeological evidence from deserts, high-altitude settings, tropical rainforests, and maritime habitats seem to increasingly suggest that Late Pleistocene humans rapidly adapted to a number of extreme environments. By contrast, our closest hominin relatives, such as Homo erectus and Neanderthals, apparently used various mixtures of forests and grasslands, albeit from as far apart as the Levant, Siberia, and Java. However, this apparent distinction needs testing, especially as finds of another closely related hominin, the Denisovans, have been found on the high-altitude Tibetan Plateau.

As one of the corresponding authors on the new paper, Sue O'Connor of Australian National University says, "The islands beyond Wallace's Line are ideal places to test the adaptive differences between our species and other hominins. These islands were never connected to mainland Southeast Asia during the Pleistocene, and would have ensured that hominins had to make water crossings to reach it." Tropical forest settings like those in Wallacea are often considered barriers to human expansion and are a far cry from the sweeping 'savannahs' with an abundance of medium to large mammals that hominins are believed to have relied on.

Fossils and stone tools show that hominins made it to Wallacean islands at least one million years ago, including the famous 'Hobbit,' or Homo floresiensis, on the island of Flores. When our own species arrived 45,000 years ago (or perhaps earlier), it is thought to have quickly developed the specialized use of marine habitats, as evidenced by one of the world's earliest fish hooks found in the region. Nevertheless, as co-author Ceri Shipton puts it "the extent of this maritime adaptation has remained hotly debated and difficult to test using snapshots based on, often poorly preserved, animal remains."

Stable isotope analysis and Late Pleistocene humans

This new paper uses stable carbon isotopes measured from fossil human teeth to directly reconstruct the long-term diets of past populations. Although this method has been used to study the diets and environments of African hominins for nearly half a century, it has thus far been scarcely applied to the earliest members of our own species expanding within and beyond Africa. Using the principle 'you are what you eat,' researchers analyzed powdered hominin tooth enamel from 26 individuals dated between 42,000 and 1,000 years ago to explore the types of resources they consumed during tooth formation.

The new paper shows that the earliest human fossil available from the region, excavated from the site of Asitau Kuru on Timor, was indeed reliant on maritime resources, suggesting a well-tuned adaptation to the colonization of coastal areas. "This fits with our existing models of rapid human movement through Wallacea on the way to Australia," says co-author Shimona Kealy of the Australian National University.

From around 20,000 years ago, however, human diets seem to have switched inland, towards the supposedly impoverished resources of the island forests. Although some individuals maintained the use of coastal habitats, the majority seemingly began to adapt to the populations of small mammals and tropical forest plants in the region. As co-author Mahirta at Universitas Gadjah Mada puts it, "Coastal resources such as shellfish and reef fish are easy to exploit and available year-round, however growing populations likely forced early island occupants to look inland to other resources."

A species defined by flexibility

This study provides the first direct insights into the adaptations of our own species as it settled in a series of challenging island environments in Wallacea. "Early human populations here, and elsewhere, could not only successfully use the enormous variety of often-extreme Pleistocene environments," suggests Patrick Roberts, lead author of the study and Group Leader at MPI SHH, "they could also specialize in them over substantial periods of time. As a result, even if some local populations did fail, the species as a whole would go on to become tremendously prolific."

Read more at Science Daily

Asteroid 1998 OR2 to safely fly past Earth this week

A large near-Earth asteroid will safely pass by our planet on Wednesday morning, providing astronomers with an exceptional opportunity to study the 1.5-mile-wide (2-kilometer-wide) object in great detail.

The asteroid, called 1998 OR2, will make its closest approach at 5:55 a.m. EDT (2:55 a.m. PDT). While this is known as a "close approach" by astronomers, it's still very far away: The asteroid will get no closer than about 3.9 million miles (6.3 million kilometers), passing more than 16 times farther away than the Moon.

Asteroid 1998 OR2 was discovered by the Near-Earth Asteroid Tracking program at NASA's Jet Propulsion Laboratory in July 1998, and for the past two decades astronomers have tracked it. As a result, we understand its orbital trajectory very precisely, and we can say with confidence that this asteroid poses no possibility of impact for at least the next 200 years. Its next close approach to Earth will occur in 2079, when it will pass by closer -- only about four times the lunar distance.

Despite this, 1998 OR2 is still categorized as a large "potentially hazardous asteroid" because, over the course of millennia, very slight changes in the asteroid's orbit may cause it to present more of a hazard to Earth than it does now. This is one of the reasons why tracking this asteroid during its close approach -- using telescopes and especially ground-based radar -- is important, as observations such as these will enable an even better long-term assessment of the hazard presented by this asteroid.

Close approaches by large asteroids like 1998 OR2 are quite rare. The previous close approach by a large asteroid was made by asteroid Florence in September 2017. That 3-mile-wide (5-kilometer-wide) object zoomed past Earth at 18 lunar distances. On average, we expect asteroids of this size to fly by our planet this close roughly once every five years.

Since they are bigger, asteroids of this size reflect much more light than smaller asteroids and are therefore easier to detect with telescopes. Almost all near-Earth asteroids (about 98%) of the size of 1998 OR2 or larger have already been discovered, tracked and cataloged. It is extremely unlikely there could be an impact over the next century by one of these large asteroids, but efforts to discover all asteroids that could pose an impact hazard to Earth continue.

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Newly discovered exoplanet dethrones former king of Kepler-88 planetary system

Our solar system has a king. The planet Jupiter, named for the most powerful god in the Greek pantheon, has bossed around the other planets through its gravitational influence. With twice the mass of Saturn, and 300 times that of Earth, Jupiter's slightest movement is felt by all the other planets. Jupiter is thought to be responsible for the small size of Mars, the presence of the asteroid belt, and a cascade of comets that delivered water to young Earth.

Do other planetary systems have gravitational gods like Jupiter?

A team of astronomers led by the University of Hawaii Institute for Astronomy (UH IfA) has discovered a planet three times the mass of Jupiter in a distant planetary system.

The discovery is based on six years of data taken at W. M. Keck Observatory on Maunakea in Hawaii. Using the High-Resolution Echelle Spectrometer (HIRES) instrument on the 10-meter Keck I telescope, the team confirmed that the planet, named Kepler-88 d, orbits its star every four years, and its orbit is not circular, but elliptical. At three times the mass of Jupiter, Kepler-88 d is the most massive planet in this system.

The system, Kepler-88, was already famous among astronomers for two planets that orbit much closer to the star, Kepler-88 b and c (planets are typically named alphabetically in the order of their discovery).

Those two planets have a bizarre and striking dynamic called mean motion resonance. The sub-Neptune sized planet b orbits the star in just 11 days, which is almost exactly half the 22-day orbital period of planet c, a Jupiter-mass planet. The clockwork-like nature of their orbits is energetically efficient, like a parent pushing a child on a swing. Every two laps planet b makes around the star, it gets pumped. The outer planet, Kepler-88 c, is twenty times more massive than planet b, and so its force results in dramatic changes in the orbital timing of the inner planet.

Astronomers observed these changes, called transit timing variations, with the NASA Kepler space telescope, which detected the precise times when Kepler-88 b crossed (or transited) between the star and the telescope. Although transit timing variations (TTVs for short) have been detected in a few dozen planetary systems, Kepler-88 b has some of the largest timing variations. With transits arriving up to half a day early or late, the system is known as "the King of TTVs."

The newly discovered planet adds another dimension to astronomers' understanding of the system.

"At three times the mass of Jupiter, Kepler-88 d has likely been even more influential in the history of the Kepler-88 system than the so-called King, Kepler-88 c, which is only one Jupiter mass," says Dr. Lauren Weiss, Beatrice Watson Parrent Postdoctoral Fellow at UH IfA and lead author on the discovery team. "So maybe Kepler-88 d is the new supreme monarch of this planetary empire -- the empress."

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Spitzer telescope reveals the precise timing of a black hole dance

This image shows two massive black holes in the OJ 287 galaxy. The smaller black hole orbits the larger one, which is also surrounded by a disk of gas. When the smaller black hole crashes through the disk, it produces a flare brighter than 1 trillion stars.

Black holes aren't stationary in space; in fact, they can be quite active in their movements. But because they are completely dark and can't be observed directly, they're not easy to study. Scientists have finally figured out the precise timing of a complicated dance between two enormous black holes, revealing hidden details about the physical characteristics of these mysterious cosmic objects.

The OJ 287 galaxy hosts one of the largest black holes ever found, with over 18 billion times the mass of our Sun. Orbiting this behemoth is another black hole with about 150 million times the Sun's mass. Twice every 12 years, the smaller black hole crashes through the enormous disk of gas surrounding its larger companion, creating a flash of light brighter than a trillion stars -- brighter, even, than the entire Milky Way galaxy. The light takes 3.5 billion years to reach Earth.

But the smaller black hole's orbit is oblong, not circular, and it's irregular: It shifts position with each loop around the bigger black hole and is tilted relative to the disk of gas. When the smaller black hole crashes through the disk, it creates two expanding bubbles of hot gas that move away from the disk in opposite directions, and in less than 48 hours the system appears to quadruple in brightness.

Because of the irregular orbit, the black hole collides with the disk at different times during each 12-year orbit. Sometimes the flares appear as little as one year apart; other times, as much as 10 years apart. Attempts to model the orbit and predict when the flares would occur took decades, but in 2010, scientists created a model that could predict their occurrence to within about one to three weeks. They demonstrated that their model was correct by predicting the appearance of a flare in December 2015 to within three weeks.

Then, in 2018, a group of scientists led by Lankeswar Dey, a graduate student at the Tata Institute of Fundamental Research in Mumbai, India, published a paper with an even more detailed model they claimed would be able to predict the timing of future flares to within four hours. In a new study published in the Astrophysical Journal Letters, those scientists report that their accurate prediction of a flare that occurred on July 31, 2019, confirms the model is correct.

The observation of that flare almost didn't happen. Because OJ 287 was on the opposite side of the Sun from Earth, out of view of all telescopes on the ground and in Earth orbit, the black hole wouldn't come back into view of those telescopes until early September, long after the flare had faded. But the system was within view of NASA's Spitzer Space Telescope, which the agency retired in January 2020.

After 16 years of operations, the spacecraft's orbit had placed it 158 million miles (254 million kilometers) from Earth, or more than 600 times the distance between Earth and the Moon. From this vantage point, Spitzer could observe the system from July 31 (the same day the flare was expected to appear) to early September, when OJ 287 would become observable to telescopes on Earth.

"When I first checked the visibility of OJ 287, I was shocked to find that it became visible to Spitzer right on the day when the next flare was predicted to occur," said Seppo Laine, an associate staff scientist at Caltech/IPAC in Pasadena, California, who oversaw Spitzer's observations of the system. "It was extremely fortunate that we would be able to capture the peak of this flare with Spitzer, because no other human-made instruments were capable of achieving this feat at that specific point in time."

Ripples in Space

Scientists regularly model the orbits of small objects in our solar system, like a comet looping around the Sun, taking into account the factors that will most significantly influence their motion. For that comet, the Sun's gravity is usually the dominant force, but the gravitational pull of nearby planets can change its path, too.

Determining the motion of two enormous black holes is much more complex. Scientists must account for factors that might not noticeably impact smaller objects; chief among them are something called gravitational waves. Einstein's theory of general relativity describes gravity as the warping of space by an object's mass. When an object moves through space, the distortions turn into waves. Einstein predicted the existence of gravitational waves in 1916, but they weren't observed directly until 2015 by the Laser Interferometer Gravitational Wave Observatory (LIGO).

The larger an object's mass, the larger and more energetic the gravitational waves it creates. In the OJ 287 system, scientists expect the gravitational waves to be so large that they can carry enough energy away from the system to measurably alter the smaller black hole's orbit -- and therefore timing of the flares.

While previous studies of OJ 287 have accounted for gravitational waves, the 2018 model is the most detailed yet. By incorporating information gathered from LIGO's detections of gravitational waves, it refines the window in which a flare is expected to occur to just 1 1/2 days.

To further refine the prediction of the flares to just four hours, the scientists folded in details about the larger black hole's physical characteristics. Specifically, the new model incorporates something called the "no-hair" theorem of black holes.

Published in the 1960s by a group of physicists that included Stephen Hawking, the theorem makes a prediction about the nature of black hole "surfaces." While black holes don't have true surfaces, scientists know there is a boundary around them beyond which nothing -- not even light -- can escape. Some ideas posit that the outer edge, called the event horizon, could be bumpy or irregular, but the no-hair theorem posits that the "surface" has no such features, not even hair (the theorem's name was a joke).

In other words, if one were to cut the black hole down the middle along its rotational axis, the surface would be symmetric. (The Earth's rotational axis is almost perfectly aligned with its North and South Poles. If you cut the planet in half along that axis and compared the two halves, you would find that our planet is mostly symmetric, though features like oceans and mountains create some small variations between the halves.)

Finding Symmetry

In the 1970s, Caltech professor emeritus Kip Thorne described how this scenario -- a satellite orbiting a massive black hole -- could potentially reveal whether the black hole's surface was smooth or bumpy. By correctly anticipating the smaller black hole's orbit with such precision, the new model supports the no-hair theorem, meaning our basic understanding of these incredibly strange cosmic objects is correct. The OJ 287 system, in other words, supports the idea that black hole surfaces are symmetric along their rotational axes.

So how does the smoothness of the massive black hole's surface impact the timing of the smaller black hole's orbit? That orbit is determined mostly by the mass of the larger black hole. If it grew more massive or shed some of its heft, that would change the size of smaller black hole's orbit. But the distribution of mass matters as well. A massive bulge on one side of the larger black hole would distort the space around it differently than if the black hole were symmetric. That would then alter the smaller black hole's path as it orbits its companion and measurably change the timing of the black hole's collision with the disk on that particular orbit.

"It is important to black hole scientists that we prove or disprove the no-hair theorem. Without it, we cannot trust that black holes as envisaged by Hawking and others exist at all," said Mauri Valtonen, an astrophysicist at University of Turku in Finland and a coauthor on the paper.

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