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Corticosteroid injections associated with progression of knee osteoarthritis

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Two studies comparing injections commonly used to relieve the pain of knee osteoarthritis found that corticosteroid injections were associated with the progression of the disease. Results of both studies were presented today at the annual meeting of the Radiological Society of North America (RSNA).

Osteoarthritis is the most common form of arthritis, affecting 32.5 million adults in the U.S. Knee osteoarthritis is a chronic, degenerative and progressive condition with an estimated incidence of 800,000 patients each year. More than 10% of patients with knee osteoarthritis seek noninvasive treatment for pain relief through corticosteroid or hyaluronic acid injections.

Researchers in both studies chose cohorts from the Osteoarthritis Initiative, a multicenter, longitudinal, observational study of nearly 5,000 participants with knee osteoarthritis currently in its 14th year of follow-up.

In the first study, researchers at the University of California, San Francisco included 210 Osteoarthritis Initiative participants, 70 of whom received intraarticular injections, and a control group of 140 who did not receive injections during a two-year period. Of the 70 patients who received injections, 44 were injected with corticosteroids, and 26 were injected with hyaluronic acid. The treatment and control groups were matched by age, sex, body mass index, pain and physical activity scores, and severity of disease.

MRI was performed on all patients at the time of the injection and two years before and after. The MRI scans were assessed using whole-organ magnetic resonance imaging score (WORMS), a grading system for knee osteoarthritis that focuses on the meniscus, bone marrow lesions, cartilage, joint effusion and ligaments. The researchers identified osteoarthritis progression by comparing the imaging scores from the initial scans and two-year follow-up scans.

This is the first direct comparison of corticosteroid and hyaluronic acid injections using the semi-quantitative, whole organ assessment of the knee with MRI.”

Upasana Upadhyay Bharadwaj, M.D., Research Fellow, Department of Radiology, University of California, San Francisco

Statistical analysis showed that corticosteroid knee injections were significantly associated with the overall progression of osteoarthritis in the knee, specifically in the lateral meniscus, lateral cartilage and medial cartilage.

Hyaluronic acid knee injections were not significantly associated with the progression of osteoarthritis in the knee. Compared to the control group, the group who received hyaluronic injections showed a decreased progression of osteoarthritis, specifically in bone marrow lesions.

“While both corticosteroid and hyaluronic acid injections are reported to help with symptomatic pain relief for knee osteoarthritis, our results conclusively show that corticosteroids are associated with significant progression of knee osteoarthritis up to two years post-injection and must be administered with caution,” Dr. Upadhyay Bharadwaj said. “Hyaluronic acid, on the other hand, may slow down progression of knee osteoarthritis and alleviate long term effects while offering symptomatic relief.”

In the second study, researchers at the Chicago Medical School of Rosalind Franklin University of Medicine and Science conducted a case-control study comparing the radiographic progression of osteoarthritis in patients who received injections of corticosteroids and hyaluronic acid.

“While these injections provide some patients with short-term pain relief, the effects of the injections on the progression of the disease are unknown,” said researcher and medical student Azad Darbandi.

Darbandi’s team selected a cohort of 150 patients with similar baseline characteristics from the Osteoarthritis Initiative database, including 50 patients who received corticosteroid injections, 50 who received hyaluronic acid injections, and 50 who were not injected over a 36-month time period. The groups were matched by sex, body mass index and X-ray findings.

Patients underwent X-ray imaging of the knee at baseline and two years later. The researchers analyzed the X-ray imaging, including joint space narrowing, formation of bone spurs, and bone thickening around the knee cartilage.

Compared to patients who received an injection of hyaluronic acid or no treatment at all, patients injected with corticosteroids had significantly more osteoarthritis progression, including medial joint space narrowing, a hallmark of the disease.

“Even though imaging findings for all patients were similar at baseline, the imaging hallmarks of osteoarthritis were worse two years later in patients who received corticosteroid injections compared to patients who received hyaluronic acid injections or no treatment at all,” Darbandi said. “The results suggest that hyaluronic acid injections should be further explored for the management of knee osteoarthritis symptoms, and that steroid injections should be utilized with more caution.”

“Knowing the long-term effects of these injections will help osteoarthritis patients and clinicians make more informed decisions for managing the disease and the pain it causes,” Dr. Upadhyay Bharadwaj added.

Dr. Upadhyay Bharadwaj’s co-authors are Thomas Link, M.D., Ph.D., Zehra Akkaya, Gabby Joseph, John Lynch, Ph.D., and Paula Giesler. Darbandi’s co-authors are Sean Hormozian, Atefe Pooyan, M.D., Ehsan Alipour, M.D., Firoozeh Shomal Zadeh, M.D., Parham Pezeshk, M.D., and Majid Chalian, M.D.

Source:

Radiological Society of North America

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Astronomers Have Spotted a Record-Breaking Magnetic Field in Space, And It’s Epic

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Far out in the Milky Way, roughly 22,000 light years from Earth, a star unlike any other roars with a magnetic force that beats anything physicists have ever seen. 

At a whopping 1.6 billion Tesla, a pulsar called Swift J0243.6+6124 smashes the previous records of around 1 billion Tesla, discovered surrounding the pulsars GRO J1008-57 and 1A 0535+262.

 

For a bit of context, your average novelty fridge magnet comes in at around 0.001 Tesla. The more powerful MRI machines manage to hit around 3 Tesla.

A few years ago, engineers earned a pat on the back for achieving a semi-respectable 1,200 Tesla, sustaining it for a blink of just 100 microseconds.

So it stands to reason that 1.6 billion Tesla is going to demand some truly mind-blowing physics. The kind only achievable by massive objects crammed into impossible volumes and spun at incredible speeds, fast enough to accelerate electrons to ridiculous velocities.

Swift J0243.6+6124 was already regarded as a star worth paying attention to. A type of super-compact cosmic heavyweight known as a pulsar, it’s the only X-ray source in our galaxy to fall into the ultra-luminous category.

It’s also the only example in the Milky Way of an X-ray pulsar with a Be-type companion star feeding it matter fast enough to generate radio-emitting jets of matter from its poles.

Those features alone add up to a unique opportunity in our galactic backyard astronomers can’t help but study in detail.

 

Measuring the magnetic field of a far-distant object is easier said than done, though. As strong as they are, those fields quickly weaken to become undetectable over distances of thousands of light years.

Fortunately clues can be found in the way that the ultra-bright glow of X-rays scatters from the electrons whizzing down the magnetic racetrack, something known as a cyclotron resonance scattering feature.

China’s launch of the X-ray observatory Insight-HXMT in 2017 provides astrophysicists with a way to capture signatures like these in distant emissions, leading to the measure of electron energies in the GRO J1008-57 field in 2020.

Fortunately, an outburst of activity in Swift J0243.6+6124 following Insight-HXMT’s launch also provided a glimpse into its own high-strength magnetic field, with a cyclotron resonance scattering feature buried within its X-ray spectrum.

Researchers from the Chinese Academy of Sciences and Sun Yat-Sen University in China, and the University of Tübingen in Germany, subsequently analyzed the feature to calculate the energy of its electrons to peak at an astonishing 146 kiloelectron volts, blitzing the 90 and 100 kiloelectron volts of the previous record holders.

 

Given Swift J0243.6+6124 is the only ultra-luminescent X-ray pulsar in our galaxy, having a precise measure on its magnetic field gives astronomers a better idea of what might be happening close to its surface.

As a type of neutron star, pulsars like Swift J0243.6+6124 are made of atoms squished into configurations far beyond anything we can create on Earth. Its magnetic properties help exclude or support various models that explain how its highly compact crust behaves.

Specifically, the nature of the neutron star’s magnetism confirms the likelihood that its field is complex, consisting of multiple poles.

That’s a solid win for astrophysicists keen to understand the mysteries of some of the most exotic objects in space.

For the rest of us, it’s enough just to try to imagine the might of a 1.6 billion Tesla magnet stuck to our fridge.

This research was published in The Astrophysical Journal Letters.

 

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An Ultra-Rare Cosmic Object Was Just Detected in The Milky Way, Astronomers Report

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A new member of a category of star so rare we can count the known number of them on our fingers and toes has just been discovered in the Milky Way.

It’s called MAXI J1816-195, located no greater than 30,000 light-years away. Preliminary observations and investigations suggest that it’s an accreting X-ray millisecond pulsar – of which only 18 others are known, according to a pulsar database compiled by astronomer Alessandro Patruno.

 

When numbers are that low, any new object represents an extremely exciting find that can yield important statistical information about how those objects form, evolve, and behave.

The discovery really is hot off the presses. X-ray light emanating from the object was first detected on 7 June by the Japanese Space Agency’s Monitor of All-sky X-ray Image (MAXI) instrument mounted on the outside of the ISS.

In a notice posted to The Astronomer’s Telegram (ATel), a team headed by astrophysicist Hitoshi Negoro of Nihon University in Japan posted that they’d identified a previously uncatalogued X-ray source, located in the galactic plane between the constellations of Sagittarius, Scutum, and Serpens. It was, they said, flaring relatively brightly, but they hadn’t been able to identify it based on the MAXI data.

It wasn’t long before other astronomers piled on. Using the Neil Gehrels Swift Observatory, a space-based telescope, astrophysicist Jamie Kennea of Pennsylvania State University and colleagues homed in on the location to confirm the detection with an independent instrument, and localize it.

Swift saw the object in X-rays, but not optical or ultraviolet light, at the location specified by the MAXI observations.

 

“This location does not lie at the location of any known catalogued X-ray source, therefore we agree that this is a new transient source MAXI J1816-195,” they wrote in a notice posted to ATel.

“In addition, archival observations by Swift/XRT of this region taken in 2017 June 22, do not reveal any point source at this location.”

Curiouser and curiouser.

Next up was the Neutron Star Interior Composition Explorer (NICER), an X-ray NASA instrument also mounted to the ISS, in an investigation led by astrophysicist Peter Bult of NASA’s Goddard Space Flight Center.

And this is where things started to get really interesting. NICER picked up X-ray pulsations at 528.6 Hz – suggesting that the thing is spinning at a rate of 528.6 times per second – in addition to an X-ray thermonuclear burst.

“This detection,” they wrote, “shows that MAXI J1816-195 is a neutron star and a new accreting millisecond X-ray pulsar.”

So what does that mean? Well, not all pulsars are built alike. At the very basic level, a pulsar is a type of neutron star, which is the collapsed core of a dead massive star that has gone supernova. These objects are very small and very dense – up to around 2.2 times the mass of the Sun, packed into a sphere just 20 kilometers (12 miles) or so across.

 

To be classified as a pulsar, a neutron star has to… pulse. Beams of radiation are launched from its poles; because of the way the star is angled, these beams sweep past Earth like the beams from a lighthouse. Millisecond pulsars are pulsars that spin so fast, they pulse hundreds of times a second.

Some pulsars are powered purely by rotation, but another type is powered by accretion. The neutron star is in a binary system with another star, their orbit so close that material is siphoned from the companion star and onto the neutron star. This material is channeled along the neutron star’s magnetic field lines to its poles, where it falls down onto the surface, producing hotspots that flare brightly in X-rays.

In some cases, the accretion process can spin up the pulsar to millisecond rotational speeds. This is the accreting X-ray millisecond pulsar, and it appears that MAXI J1816-195 belongs to this rare category.

The thermonuclear X-ray burst detected by NICER was likely the result of the unstable thermonuclear burning of material accumulated by the companion star.

Since the discovery is so new, observations in multiple wavelengths are ongoing. Follow-up has already been conducted using Swift, and the 2m Liverpool Telescope on the Canary Island of La Palma in Spain was employed to look for an optical counterpart, although none was detected. Other astronomers are also encouraged to climb aboard the MAXI J1816-195 train.

Meanwhile, a full pulsar timing analysis is being conducted, and will, Bult and his team said, be circulated as more data becomes available. You can follow along on ATel.

 

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Astronomers Witness The X-Ray ‘Fireball’ of a Stellar Nova For The First Time

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The brief, yet colossal eruption of a dead star undergoing a nova explosion has been captured by one of the most powerful X-ray instruments in space.

The joint German-Russian eROSITA telescope, aboard the Spektr-RG space observatory in the L2 Lagrange point (yes, Webb’s home), caught for the first time what is known as the ‘fireball’ phase of a classical nova. This X-ray data has finally confirmed via observation a 1990 prediction about the physics of novae.

 

The nova in question is known as YZ Reticuli, discovered on 15 July 2020, at a distance of around 8,250 light-years, near the southern constellation of Reticulum. Analysis revealed that this transient brightening was likely the result of what we call a classical nova – an eruption from a white dwarf star.

Here’s how it works. A white dwarf star is what we think of as a “dead” star – the collapsed core of a star that was up to around 8 times the mass of the Sun after it reached the end of its atomic fusion (main sequence) lifespan, and ejected its outer material. Other objects of this kind include neutron stars (between 8 and 30 solar masses) and black holes (anything bigger than that).

White dwarfs are small and dense: between the size of Earth and the Moon, roughly, and up to as massive as 1.4 Suns. That mass limit is known as the Chandrasekhar limit: if a white dwarf exceeds that limit, it becomes so unstable that it blows up in a spectacular supernova.

White dwarfs can also – frequently – be in binary systems with larger (albeit less massive) stars. If they’re in a close-enough mutual orbit, the white dwarf can siphon material from its binary companion.

 

That material is primarily hydrogen; it accumulates on the white dwarf’s surface, where it heats up. Eventually, the mass becomes so great that pressure and temperature at the bottom of the hydrogen layer are sufficient to ignite atomic fusion on the white dwarf’s surface; this triggers a thermonuclear explosion, violently expelling the excess material into space. Hello, nova.

During its second all-sky survey from June to December 2020, eROSITA repeatedly swept the region of sky containing the white dwarf. On its first 22 passes, everything looked just normal, hunky-as-dory could be. On the 23rd pass, however, beginning on 7 July 2020, an extremely bright, soft X-ray source appeared at what was later to be identified as YZ Reticuli – only to disappear again at the next pass, meaning the entire flash couldn’t have lasted more than eight hours.

This was 11 hours prior to the optical brightening of the source. This, astronomers say, was entirely consistent with theoretical modeling of the ‘fireball’ phase of a nova. (Previous observations of a nova fireball were taken in optical wavelengths, and concern the expanding ejecta as the star erupts – a different stage of the nova entirely.)

 

According to a prediction advanced in 1990, a very brief ‘fireball’ phase should take place between the runaway fusion that triggers the explosion and the brightening of the star in optical wavelengths. This phase should appear as a soft, short, and bright flash of X-radiation before the star brightens in optical wavelengths.

This, according to theory, happens because the expanding material reaches the white dwarf’s photosphere, or ‘surface’. For a brief period of time, the outward acceleration of that material matches the inward acceleration due to the star’s gravity, causing the white dwarf to heat up and shine with maximum luminosity, known as Eddington luminosity.

As the explosion continues to expand, it cools down, causing the light emitted to shift from the more energetic X-ray wavelengths into the optical. That’s usually when we see a nova brighten.

The results have allowed the team to make a few key measurements of the white dwarf in question. These include the precise timing of the thermonuclear reaction, and the temperature evolution of the white dwarf during the entire duration of the nova event. Theoretical work also suggests that the duration of the fireball phase corresponds to the mass of the white dwarf. Using this information, the team derived a mass of 0.98 times the mass of the Sun.

The observation, the team said, was a very lucky one. Over its four-year mission, eROSITA is expected to detect just one or two such fireballs, given the rate of novas in our galaxy.

“With the successful detection of the flash of YZ Reticuli by eROSITA, the existence of X-ray flashes has now been observationally confirmed,” the researchers write in their paper.

“Our detection also adds the missing piece to measure the total nova energetics and completes the whole picture of the photospheric evolution of the thermonuclear runaway.”

The research has been published in Nature.

 

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A Stupid Amount of Feasting Black Holes Was Detected in This Cosmic Spiderweb

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New images of the Spiderweb protocluster of galaxies reveal an unusually high number of active supermassive black holes.

Data from the Chandra X-ray Observatory collected over 8 days show that, in the volume of surveyed space, 14 black holes at the hearts of the galaxies, including the Spiderweb Galaxy at the center of the protocluster, are hungrily devouring material from the space around them.

 

This is a much higher rate than other, similar volumes of space, suggesting that up to a quarter of the most massive galaxies in the baby cluster are bound by actively growing black holes.

The Spiderweb protocluster, named for the Spiderweb galaxy at its center, is a growing cluster of galaxies whose light has traveled 10.6 billion light-years to reach us. It hails back to a period in cosmic time known as ‘Cosmic Noon’ – a short period approximately 2-3 billion years after the Big Bang in which galaxies formed stars at a furious rate.

Today, wherever it is, the Spiderweb cluster should have evolved into a massive, stable, gravitationally bound cluster of galaxies.

Studying such clusters while they are still in the early stages of assembling should yield insights into the evolution of the large-scale structure of the Universe. It can also tell us more about the processes that affect star formation rates and supermassive black hole (SMBH) activity in members of galaxy clusters.

The 14 active SMBHs, with the Spiderweb Galaxy in the center. (NASA/CXC/INAF/P. Tozzi et al./NAOJ/NINS/STScI)

But we don’t actually know how galaxy clusters evolve, so it’s difficult to ascertain which groups are genuine protoclusters, and which are unlikely to change. For that reason, scientists look for unusual, interesting targets displaying activity related to evolution, confirmed across multiple wavelengths.

The Chandra observations of the Spiderweb protocluster were part of this process. When an SMBH is actively accreting material, the process injects energy known as “feedback” into the galaxy around it, which in turn has a massive impact on star formation.

 

A team of scientists led by astrophysicist Paolo Tozzi of the National Institute for Astrophysics in Italy turned the telescope onto the cluster to look for the telltale X-ray emission from feeding supermassive black holes.

Although the black holes themselves give off no light, accretion is so energetic that it sends high-energy light blazing across the Universe. This is what the team detected. In a region of space roughly 11.3 million light-years across, 14 of the galaxies in the protocluster were seen to be emitting X-rays, suggesting that their SMBHs are active.

A multi-wavelength image of the Spiderweb Galaxy. (NASA/CXC/INAF/P. Tozzi et al./NAOJ/NINS/STScI)

This is much higher than other, similar samples of space at the same epoch, with the same range of galaxy masses. Up to 25 percent of the most massive galaxies in the protocluster could have active supermassive black holes, the researchers found. That’s five to 20 times higher than other samples.

This could have interesting implications for our understanding of how galaxy clusters grow, and affect galaxy formation and evolution. The finding suggests there is something specific to the Spiderweb protocluster environment that is triggering supermassive black hole activity.

 

It’s unclear what this environmental factor might be. It’s possible the gravitational interactions between the galaxies are moving material around, sweeping it towards the galactic centers where it can be devoured by the black holes.

Another possibility, the researchers said, is that the protocluster has somehow retained a large quantity of cold gas, which would be easier for the black holes to accrete than the hot gas we see in nearby galaxy clusters. Or maybe a combination of factors is at play.

Data from instruments that can see into different wavelengths, including the Hubble Space Telescope, should help shed some light (ha ha) on this mystery, the researchers said.

“By exploiting the available multiwavelength dataset on the Spiderweb field, we plan to further explore the properties of the X-ray protocluster members to investigate the main physical mechanism responsible for triggering the X-ray emission,” they wrote in their paper.

The research has been accepted into Astronomy & Astrophysics, and is available on arXiv.

 

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Breathtaking New Chandra Pics Show Cosmic Objects Like You’ve Never Seen Them Before

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Human vision may be limited to a specific range of wavelengths, but that doesn’t mean we’ll never understand the full complexity of light in our Universe.

Instruments can peer into the cosmos in regimes that are otherwise invisible to our eyes, showing us not just the dynamics of the stars, but their absolutely awe-inspiring beauty. This is what we see in a new collection of images from the Chandra X-ray Observatory that combines its data with other instruments for spectacular multi-wavelength views.

 

Because different wavelengths of light have different energies, these images can show us the dynamics of cosmic objects from low energy to high. This can help scientists unravel the mechanisms behind the glorious light-shows.

R Aquarii. (X-ray: NASA/CXC/SAO/R. Montez et al.; Optical: NASA/ESA/STScI)

R Aquarii, seen here in X-ray from Chandra (purple) and near-infrared and optical from the Hubble Space Telescope (red and blue) is a pair of stars locked in a violent dance of death 650 light-years from Earth. One of the stars is a red giant, known as a Mira variable star, at the very end of its lifespan. Stars of this kind have already lost at least half their material, and as they pulsate, they reach a brightness 1,000 times that of the Sun.

The other star is a white dwarf – a ‘dead’ star that has exhausted its nuclear fuel – and also has a lot going on. As the red giant ejects material, the white dwarf slurps it up. The material it devours from the red giant accumulates on its surface, occasionally triggering an enormous thermonuclear explosion that blasts the material out into space.

This violent interaction is creating clouds of dust and gas in a nebula around the binary, churned up by their gravitational interactions and explosive shock waves.

Cassiopeia A. (NASA/CXC/SAO; Optical: NASA/STScI; Radio: NSF/NRAO/VLA)

Cassiopeia A, located 11,000 light-years away, is one of the most famous and well-studied objects in the Milky Way. It’s what we call a supernova remnant – what’s left after a massive star has gone kaboom. Here, X-ray data from Chandra are combined with radio data from the Karl Jansky Very Large Array (dark purple, blue, and white) and optical data from Hubble (orange).

These different wavelengths can reveal what’s actually happening in the expanding cloud, consisting of the guts of a dead star. From these combined data, scientists are able to identify different elements within the explosion. The Chandra data alone revealed that the exploding star blasted off 10,000 Earth masses of sulfur; 20,000 Earth masses of silicon; 70,000 Earth masses of iron; and 1 million Earth masses of oxygen.

This is important information, because it tells us what elements were produced in the star when it died. In turn, scientists can use these data to learn more about the star when it was still burning, to make predictions about similar stars in our galaxy.

( NASA/CXC/SAO; Optical: NASA/STScI & Palomar Observatory 5-m Hale Telescope)

This image shows two different effects produced by a single dead star called PSR B2224+65. The pink streak is X-ray emission ejected from the poles of a type of neutron star called a pulsar. That’s the collapsed core of a dead massive star that emits pulsing radiation as it rotates.

That would be interesting enough, but PSR B2224+65 is also what we call a runaway star; it’s speeding through the galaxy after being punted into space at a speed of around 1,600 kilometers, or 1,000 miles, per second. That motion has created a wake in the interstellar medium; you can see it in the lower left of the image in optical wavelengths (blue). Because it looks uncannily like a guitar, astronomers have named it the Guitar Nebula.

Abell 2597. (NASA/CXC/SAO/G. Tremblay et al.; Optical: DSS; H-Alpha: LCO/IMACS/MMTF)

Some of the biggest collections of objects in the Universe are galaxy clusters. These clusters can contain thousands of galaxies, bound together by, and interacting via, gravity. This cluster is Abell 2597, roughly a billion light-years away, and multi-wavelength astronomy has helped scientists learn more about the behavior of the supermassive black hole in its central galaxy.

Just a few years ago, astronomers saw evidence that this behemoth is blasting out molecular gas as it gravitationally accretes material. This molecular gas is then falling into the black hole, and feeding the cycle anew. It’s a phenomenon known as a “fountain”. The hot outflow and cold infall were observed using two different instruments; then X-ray data from Chandra revealed that they’re part of the same process.

This image above shows the cluster in X-rays (blue) from Chandra, and optical from the Digitized Sky Survey (orange) and Las Campanas Observatory (red).

NGC 4490, the Cocoon Galaxy. (X-ray: NASA/CXC/SAO; Optical: NASA/STScI)

Finally, this image shows two galaxies that have merged. It’s called NGC 4490, or the Cocoon Galaxy, and, fascinatingly, multi-wavelength astronomy revealed a secret in its core. It has not one, but two supermassive black holes, one of which is only visible in optical data, and the other can only be seen in radio and infrared. Both had been seen separately, but it took years for astronomers to put the two together.

This double nucleus is the result of that merger process; each of the two galaxies had its own supermassive black hole. Eventually, the two black holes will also likely merge, resulting in one much bigger monster.

This image combines X-ray data from Chandra (purple) and optical data from Hubble (red, green and blue) to show the results of another close galactic encounter. NGC 4490 had a hit-and-run with a smaller galaxy, NGC 4485, which perturbed the gas and triggered waves of star formation, seen here in red.

You can download larger versions of these images on the Chandra website. Cover image credit: X-ray: NASA/CXC/SAO; Optical: NASA/STScI, Palomar Observatory, DSS; Radio: NSF/NRAO/VLA; H-Alpha: LCO/IMACS/MMTF

 

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The Hottest White Dwarf We Know of Is Up to Something Ghoulish With Its Neighbor

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There’s a dead star behaving very oddly 1,300 light-years away.

It’s a white dwarf named KPD 0005+5106, and X-ray data from the Chandra space telescope have revealed that it’s enacting extreme violence on an orbiting companion. Not only is it siphoning material from this object (which, to be fair, is pretty normal for white dwarfs), the star is giving its companion an absolute drubbing by blasting it with radiation from close proximity.

 

Even more interestingly, we can’t see what the companion actually is, making it tricky to predict its eventual fate, including how long it will take to be completely destroyed and what that will mean for the white dwarf.

“We didn’t know this white dwarf had a companion before we saw the X-ray data,” said astronomer You-Hua Chu of the Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA) in Taiwan. “We’ve looked for the companion with optical light telescopes but haven’t seen anything, which means it is a very dim star, a brown dwarf, or a planet.”

White dwarfs are what happens to a star under about eight times the mass of the Sun once it runs out of elements it can fuse in its core. As the fuel runs low, it will eject its outer layers into space until finally, the core is no longer able to support itself and collapses under its own gravity into a dense object about the size of Earth (and sometimes even smaller).

Although it may be without fuel to fuse, the white dwarf remains extremely hot, so hot that it will continue to shine brightly with thermal radiation for billions of years. The average white dwarf will have a temperature of over 100,000 Kelvin (99,727 degrees Celsius or 179,540 degrees Fahrenheit) once its core stops contracting. The Sun, for context, has an effective temperature of 5,772 Kelvin.

 

KPD 0005+5106 is an outlier. It’s the hottest white dwarf we’ve identified to date, with an effective temperature of 200,000 Kelvin. This makes it very interesting to scientists since it allows them to probe the limits of what’s possible in the Universe.

Researchers also KPD 0005+5106 observed exhibiting some unusual X-ray activity, so Chu and her team decided to take a closer look using Chandra. They found that the white dwarf increases and decreases in X-ray brightness on a regular basis, every 4.7 hours.

We know of at least one thing that can cause changes in the brightness of a white dwarf: if it’s stripping material from a companion object. That material will be siphoned down to the white dwarf, where it will make its way to the poles and glow brightly. As the star and its companion orbit each other, the hot spot moves in and out of view, causing variations in brightness.

That 4.7-hour period thus would correspond with the system’s orbital period – which would make them very close together indeed. According to the team’s calculations, the white dwarf and its companion would be separated by a distance of just 1.3 times the Sun’s radius. That’s around 900,000 kilometers (550,000 miles). That would mean insanely scorching temperatures.

 

“Whatever this object is,” said astronomer Jesús Toala of the National Autonomous University of Mexico, “it’s getting blasted with heat.”

The researchers investigated possible identities for the companion and concluded that it was most likely an exoplanet with a mass around that of Jupiter. Previous research has found that exoplanets can indeed be found around white dwarfs – if they’re distant enough during the red giant phase, they can survive the star’s transition, then migrate inwards. More than one candidate gas giant has been found orbiting a white dwarf.

According to the team’s models, however, this particular gas giant doesn’t have much longer to live, only a few hundred million years. The white dwarf would be gravitationally stripping it; this stripped material would form a ring around the star and be slowly slurped down onto it.

“This is a slow demise for this object that’s basically being ripped apart by constant gravitational forces,” said astrophysicist Martín Guerrero of The Institute of Astrophysics of Andalusia in Spain. “It would be a very unpleasant place to be.”

The team also studied two other white dwarf stars that display peculiar X-ray behavior. Although these other two stars were not quite as extreme as KPD 0005+5106, their behavior was similar, suggesting that they, too, have unseen companion objects.

This suggests that exoplanet survival around a white dwarf may be more common than we thought – although not, perhaps, for very long.

The team’s research was published earlier this year in The Astrophysical Journal.

 

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Astronomers spot light from behind a black hole for the first time — proving Einstein right, again

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For the first time ever, astronomers have directly detected light from behind a supermassive black hole. The discovery proves Albert Einstein’s theory of general relativity was right — again. 

Using the European Space Agency’s XMM-Newton and NASA’s NuSTAR space telescopes, researchers were observing the black hole as it flung X-rays out into the universe. The black hole is about 10 million times more massive than our sun, and is located in the center of a nearby spiral galaxy called I Zwicky, 1,800 million light-years away from Earth.

After observing a series of bright flares of X-rays, something unprecedented occurred — more flashes that were smaller, later and different “colors” than their predecessors. According to a study published this week in the journal Nature, the “echoes” of light appeared consistent with X-rays reflected from behind the black hole — a very strange place for light to originate.  

Black holes’ gravitational pulls are so powerful that light cannot escape them. However, light can “echo,” wrapping around the back of the celestial phenomenon and allowing astronomers to see it. 

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said lead author Dan Wilkins in a statement. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself.” 

While Einstein predicted the ability of a black hole’s gravity to bend light around it in 1916, it has never been confirmed — until now.

Researchers observed bright flares of X-ray emissions, produced as gas falls into a supermassive black hole. The flares echoed off of the gas falling into the black hole, and as the flares were subsiding, short flashes of X-rays were seen – corresponding to the reflection of the flares from the far side of the disk, bent around the black hole by its strong gravitational field.

Dan Wilkins


“Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein’s general theory of relativity in action,” said co-author Roger Blandford. 

Researchers weren’t even looking to confirm Einstein’s theory. They were originally attempting to uncover the mysteries of an odd feature of black holes known as the corona, the source of the bright X-ray light. 

“I’ve been building theoretical predictions of how these echoes appear to us for a few years,” said Wilkins. “I’d already seen them in the theory I’ve been developing, so once I saw them in the telescope observations, I could figure out the connection.”

The prevailing theory is that the corona forms after gas falls continuously into the black hole, forming a spinning disk around it, “like water flushing down a drain.” The gas disk is then heated up to millions of degrees, generating a twisted magnetic field that eventually snaps, releasing its energy and producing the corona.

“This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high energy electrons that then go on to produce the X-rays,” said Wilkins. 

From here, astronomers hope to use the various “colors” observed as the X-ray echoes travel around the black hole to create a 3D map of the black hole surroundings. They also hope to learn how the corona produces such bright flares.

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Science

Astronomers spot light from behind a black hole for the first time — proving Einstein right, again

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For the first time ever, astronomers have directly detected light from behind a supermassive black hole. The discovery proves Albert Einstein’s theory of general relativity was right — again. 

Using the European Space Agency’s XMM-Newton and NASA’s NuSTAR space telescopes, researchers were observing the black hole as it flung X-rays out into the universe. The black hole is about 10 million times more massive than our sun, and is located in the center of a nearby spiral galaxy called I Zwicky, 1,800 million light-years away from Earth.

After observing a series of bright flares of X-rays, something unprecedented occurred — more flashes that were smaller, later and different “colors” than their predecessors. According to a study published this week in the journal Nature, the “echoes” of light appeared consistent with X-rays reflected from behind the black hole — a very strange place for light to originate.  

Black holes’ gravitational pulls are so powerful that light cannot escape them. However, light can “echo,” wrapping around the back of the celestial phenomenon and allowing astronomers to see it. 

“Any light that goes into that black hole doesn’t come out, so we shouldn’t be able to see anything that’s behind the black hole,” said lead author Dan Wilkins in a statement. “The reason we can see that is because that black hole is warping space, bending light and twisting magnetic fields around itself.” 

While Einstein predicted the ability of a black hole’s gravity to bend light around it in 1916, it has never been confirmed — until now.

Researchers observed bright flares of X-ray emissions, produced as gas falls into a supermassive black hole. The flares echoed off of the gas falling into the black hole, and as the flares were subsiding, short flashes of X-rays were seen – corresponding to the reflection of the flares from the far side of the disk, bent around the black hole by its strong gravitational field.

Dan Wilkins


“Fifty years ago, when astrophysicists starting speculating about how the magnetic field might behave close to a black hole, they had no idea that one day we might have the techniques to observe this directly and see Einstein’s general theory of relativity in action,” said co-author Roger Blandford. 

Researchers weren’t even looking to confirm Einstein’s theory. They were originally attempting to uncover the mysteries of an odd feature of black holes known as the corona, the source of the bright X-ray light. 

“I’ve been building theoretical predictions of how these echoes appear to us for a few years,” said Wilkins. “I’d already seen them in the theory I’ve been developing, so once I saw them in the telescope observations, I could figure out the connection.”

The prevailing theory is that the corona forms after gas falls continuously into the black hole, forming a spinning disk around it, “like water flushing down a drain.” The gas disk is then heated up to millions of degrees, generating a twisted magnetic field that eventually snaps, releasing its energy and producing the corona.

“This magnetic field getting tied up and then snapping close to the black hole heats everything around it and produces these high energy electrons that then go on to produce the X-rays,” said Wilkins. 

From here, astronomers hope to use the various “colors” observed as the X-ray echoes travel around the black hole to create a 3D map of the black hole surroundings. They also hope to learn how the corona produces such bright flares.

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Science

Renaissance-Era Letter Sealed For Centuries Just Virtually Unfolded And Read For The First Time

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More than 600 years ago, someone intricately folded, sealed and posted a letter that was never delivered. Now, scientists have digitally “unfolded” this and other similarly locked letters found in a 17th-century trunk in The Hague, using X-rays. 

 

For centuries prior to the invention of sealed envelopes, sensitive correspondence was protected from prying eyes through complex folding techniques called ‘letterlocking’, which transformed a letter into its own secure envelope.

However, locked letters that survive to the present are fragile and can be opened physically only by slicing them to pieces. 

The new X-ray method offers researchers a non-invasive alternative, maintaining a letterpacket’s original folded shape.

For the first time, scientists applied this method to “locked” letters from the Renaissance period, kept in a trunk that had been in the collection of the Dutch postal museum in The Hague, The Netherlands, since 1926. 

Computer-generated unfolding animation of sealed letter DB-1538. (Unlocking History Research Group archive)

Related: Photos: Treasure trove of unopened 17th-century letters 

The trunk’s contents include more than 3,100 undelivered letters, of which 577 were unopened and letterlocked. Known as the Brienne Collection, the letters were written in Dutch, English, French, Italian, Latin and Spanish.

For unknown reasons, once the missives reached The Hague they were never delivered to their intended recipients, and were instead kept by a postmaster named Simon de Brienne, Live Science previously reported. 

 

Locked letters used different mechanisms to stay securely closed, including folds and rolls; slits and holes; tucks and adhesives; and a variety of cleverly constructed locks, according to a study published online March 2 in the journal Nature Communications.

To penetrate the layers of folded paper, the study authors used an X‐ray microtomography scanner engineered in the dental research labs at Queen Mary University of London (QMU).

Researchers designed the scanner to be exceptionally sensitive so that it could map the mineral content of teeth, “which is invaluable in dental research,” study co-author Graham Davis, a QMU professor of 3D X-ray imaging, said in a statement. 

“But this high sensitivity has also made it possible to resolve certain types of ink in paper and parchment,” Davis added.

The trunk filled with sealed letters. (Unlocking History Research Group archive)

“The rest of the team were then able to take our scan images and turn them into letters they could open virtually and read for the first time in over 300 years,” study co-author David Mills, an X-ray microtomography facilities manager at QMU, said in the statement.

From the scans, the team built 3D digital reconstructions of the letters, and then created a computational algorithm that deciphered the sophisticated folding techniques, crease by crease, opening the letters virtually “while preserving letterlocking evidence”, according to the study. 

 

The scientists digitally opened four letters using this groundbreaking method, deciphering the contents of one letter, DB-1627.

Penned on July 31, 1697, it was written by a man named Jacques Sennacques to his cousin Pierre Le Pers, who lived in The Hague. Sennacques, a legal professional in Lille, France, requested an official death certificate for a relative named Daniel Le Pers, “perhaps due to a question of inheritance”, the scientists wrote.

“His request issued, Sennacques then spends the rest of the letter asking for news of the family and commending his cousin to the graces of God,” the authors wrote. “We do not know exactly why Le Pers did not receive Sennacques’ letter, but given the itinerancy of merchants, it is likely that Le Pers had moved on.”

(Unlocking History Research Group archive)

Tens of thousands of such sealed documents can now be unfolded and read virtually, the researchers reported.

“This algorithm takes us right into the heart of a locked letter,” the research team said in the statement. “Using virtual unfolding to read an intimate story that has never seen the light of day — and never even reached its recipient — is truly extraordinary.”

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This article was originally published by Live Science. Read the original article here.

 

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