Massive Stars In The Early Universe May Have Been Progenitors Of Super-massive Black Holes (Astronomy)

Recent observations have shown that there is a supermassive black hole at the center of each galaxy. However, what is the origin of these supermassive black holes? It is still a mystery today. An international research team led by the National Astronomical Observatory of Japan and Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan has predicted an extreme supernova from a supermassive star, possible the progenitor of supermassive black holes. Their calculation suggested that this supernova can be observed by the James Webb Space Telescope (JWST) that will be launched by the end of 2021.

Studying the formation of supermassive black holes is a significant topic in modern astrophysics. The leading theory suggests the seeds of supermassive black holes formed after the death of the first massive stars in the early universe, and then these seeds continued to accumulate the surrounding gas and finally formed into supermassive black holes today. However, this theory was challenged because the most massive stars observed in the local universe are about one or two hundred solar masses. If the first stars with a few hundred solar masses die as black hole seeds, which need to maintain the highest accretion efficiency to form the supermassive black holes observed today. But it is very difficult to maintain a high accretion rate in a realistic environment.

Assistant Research Fellow, Ke-Jung Chen from ASIAA Taiwan proposed a relativistic instability supernova from a primordial supermassive star (104–105 solar masses) in his 2014 research paper. “There may be a small number of the first stars in the early universe with tens of thousands of solar masses. They are likely to be the progenitors of supermassive black holes in galaxies. Because the more massive of the black hole seed, the more efficient it is to swallow the surrounding matter. The black holes don’t need to maintain a high accretion rate to grow quickly,” said Chen.

But how to prove these massive stars once existed? This is an observational challenge, because most of these supermassive stars are to collapse into black holes. Based on the supernova model proposed by Chen, the research team performed a new radiation transport simulation and found that the upcoming JWST mission has a chance to observe this supernova! If it is actually observed by then, the origin of the supermassive black hole in the galaxy that comes from the first supermassive star can be confirmed. Let’s wait and see!

Featured image: A mirrored half-slice through the interior of a simulated exploding supermassive star of 55,500 solar masses one day after the onset of the explosion. The radius of outer circumference is close to the Earth’s orbit. Credit: K.-J. Chen


Reference: Takashi J Moriya, Ke-Jung Chen, Kimihiko Nakajima, Nozomu Tominaga, Sergei I Blinnikov, Observational properties of a general relativistic instability supernova from a primordial supermassive star, Monthly Notices of the Royal Astronomical Society, 2021;, stab622, https://doi.org/10.1093/mnras/stab622


Provided by ASIAA

Earth-sized Exoplanet May Have Lost its Original Atmosphere, But Gained A Second One Through Volcanism (Planetary Science)

Orbiting a red dwarf star 41 light-years away is an Earth-sized, rocky exoplanet called GJ 1132 b. In some ways, GJ 1132 b has intriguing parallels to Earth, but in other ways it is very different. One of the differences is that its smoggy, hazy atmosphere contains a toxic mix of hydrogen, methane and hydrogen cyanide. Scientists using NASA’s Hubble Space Telescope have found evidence this is not the planet’s original atmosphere, and that the first one was blasted away by blistering radiation from GJ 1132 b’s nearby parent star. The so-called “secondary atmosphere” is thought to be formed as molten lava beneath the planet’s surface continually oozes up through volcanic fissures. Gases seeping through these cracks seem to be constantly replenishing the atmosphere, which would otherwise also be stripped away by the star. This is the first time a secondary atmosphere has been detected on a world outside our solar system.

Scientists using NASA’s Hubble Space Telescope have found evidence that a planet orbiting a distant star may have lost its atmosphere but gained a second one through volcanic activity.

The planet, GJ 1132 b, is hypothesized to have begun as a gaseous world with a thick hydrogen blanket of atmosphere. Starting out at several times the diameter of Earth, this so-called “sub-Neptune” is believed to have quickly lost its primordial hydrogen and helium atmosphere due to the intense radiation of the hot, young star it orbits. In a short period of time, such a planet would be stripped down to a bare core about the size of Earth. That’s when things got interesting.

To the surprise of astronomers, Hubble observed an atmosphere which, according to their theory, is a “secondary atmosphere” that is present now. Based on a combination of direct observational evidence and inference through computer modeling, the team reports that the atmosphere consists of molecular hydrogen, hydrogen cyanide, methane and also contains an aerosol haze. Modeling suggests the aerosol haze is based on photochemically produced hydrocarbons, similar to smog on Earth.

Scientists interpret the current atmospheric hydrogen in GJ 1132 b as hydrogen from the original atmosphere which was absorbed into the planet’s molten magma mantle and is now being slowly released through volcanic processes to form a new atmosphere. The atmosphere we see today is believed to be continually replenished to balance the hydrogen escaping into space.

“It’s super exciting because we believe the atmosphere that we see now was regenerated, so it could be a secondary atmosphere,” said study co-author Raissa Estrela of NASA’s Jet Propulsion Laboratory (JPL) in Southern California. “We first thought that these highly irradiated planets could be pretty boring because we believed that they lost their atmospheres. But we looked at existing observations of this planet with Hubble and said, ‘Oh no, there is an atmosphere there.'”

The findings could have implications for other exoplanets, planets beyond our solar system.

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism that photo-evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said lead author Mark Swain of JPL. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism where you can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

This plot shows the spectrum of the atmosphere of an Earth-sized, rocky exoplanet, GJ 1132 b. The orange line represents the model spectrum. In comparison, the observed spectrum is shown as blue dots representing averaged data points, along with their error bars. This analysis is consistent with GJ 1132 b being predominantly a hydrogen atmosphere with a mix of methane and hydrogen cyanide. The planet also has aerosols which cause scattering of light. This is the first time a so-called “secondary atmosphere,” which was replenished after the planet lost its primordial atmosphere, has been detected on a world outside of our solar system. Credit: NASA, ESA, and P. Jeffries (STScI)

In some ways GJ 1132 b, located about 41 light-years from Earth, has tantalizing parallels to Earth, but in some ways it is very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. The team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

But the planets have profoundly different formation histories. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our Sun. GJ 1132 b is so close to its red dwarf star that it completes an orbit around its host star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times—just as our Moon keeps one hemisphere permanently facing Earth.

“The question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

Tidal heating is a phenomenon that occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also gravitationally pulls on the planet.

The consequences are that the planet is squeezed or stretched through this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own solar system is Jupiter’s moon Io, which has continuous volcanic activity due to a tidal tug-of-war from Jupiter and the neighboring Jovian moons.

Given GJ 1132 b’s hot interior, the team believes the planet’s cooler, overlying crust is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell due to tidal flexing. Hydrogen and other gases could be released through such cracks.

NASA’s upcoming James Webb Space Telescope has the ability to observe this exoplanet. Webb’s infrared vision may allow scientists to see down to the planet’s surface. “If there are magma pools or volcanism going on, those areas will be hotter,” explained Swain. “That will generate more emission, and so they’ll be looking potentially at the actual geologic activity—which is exciting!”

The team’s findings will be published an upcoming issue of The Astronomical Journal.

Featured image: This is an artist’s impression of the Earth-sized, rocky exoplanet GJ 1132 b, located 41 light-years away around a red dwarf star. Scientists using NASA’s Hubble Space Telescope have found evidence this planet may have lost its original atmosphere but gained a second one that contains a toxic mix of hydrogen, methane and hydrogen cyanide. Hubble detected the “fingerprints” of these gases as the parent star’s light filtered through the exoplanet’s atmosphere. The planet is too far away and too dim to be photographed by Hubble. This illustrates what astronomers believe is going on at this remote world. Beneath the planet’s smoggy, hazy atmosphere, there may be a thin crust only a few hundred feet thick. Molten lava beneath the surface continually oozes up through volcanic fissures. Gases seeping through these cracks seem to be constantly replenishing the atmosphere, which would otherwise be stripped away by blistering radiation from the planet’s close-by star. The gravitational pull from another planet in the system likely fractures GJ 1132 b’s surface to resemble a cracked eggshell. This is the first time a so-called “secondary atmosphere” has been detected on a planet outside of our solar system. Credit: NASA, ESA, and R. Hurt (IPAC/Caltech)


Reference: Mark R. Swain, Raissa Estrela, Gael M. Roudier, Christophe Sotin, Paul Rimmer, Adriana Valio, Robert West, Kyle Pearson, Noah Huber-Feely, Robert T. Zellem, “Detection of an Atmosphere on a Rocky Exoplanet”, ArXiv, 2021. https://arxiv.org/abs/2103.05657


Provided by ESA/Hubble Information Centre

New Vacuum Solar Telescope Reveals Acceleration of Magnetic Reconnection (Planetary Science)

Magnetic reconnection shows the reconfiguration of magnetic field geometry. It plays an elemental role in the rapid release of magnetic energy and its conversion to other forms of energy in magnetized plasma systems throughout the universe.

Researchers led by Dr. Li Leping from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) analyzed the evolution of magnetic reconnection and its nearby filament. The result suggested that the reconnection is significantly accelerated by the propagating disturbance caused by the adjacent filament eruption.

The study was published in the Astrophysical Journal on Feb. 20.

The New Vacuum Solar Telescope (NVST) is a one meter ground-based solar telescope, located in the Fuxian Solar Observatory of Yunnan Astronomical Observatories of Chinese Academy of Sciences (YNAO). It provides observations of the solar fine structures and their evolution in the solar lower atmosphere.

The NVST observed the active region 11696 on March 15, 2013, in the Hα channel, centered at 6562.8 angstrom with a bandwidth of 0.25 angstrom.

Employing the NVST Hα images with higher spatial resolution, the researchers studied the evolution of magnetic loops and their nearby filament in the active region, combining the Atmospheric Imaging Assembly (AIA) extreme ultraviolet (EUV) images and Helioseismic and Magnetic Imager (HMI) line-of-sight magnetograms on board the Solar Dynamic Observatory (SDO).

In NVST Hα images, two groups of fibrils converged and interacted with each other. Two sets of newly formed fibrils then appeared and retracted away from the interaction region.

“The result provides clear evidence of magnetic reconnection,” said Prof. Hardi Peter from Max-Planck Institute for Solar System Research (MPS), a co-author of this study. In AIA EUV images, the current sheet formed repeatedly in the reconnection region in the lower-temperature channels, and plasmoids appeared in the current sheet and propagated along it bi-directionally.

A filament was located to the southeast of the reconnection region. It erupted, and pushed away the loops covering the reconnection region. “The filament eruption leads to a disturbance propagating outward across the reconnection region,” said Dr. Li Leping, the first author of this study.

Thereafter, the current sheet became shorter and brighter, with a larger reconnection rate. It appeared in the AIA higher-temperature channels. In the current sheet, more and hotter plasmoids formed.

“Comparing with the observations before the filament eruption during the same time intervals, more thermal and kinetic energy is converted through reconnection after the filament eruption,” said Dr. LI. “The reconnection is thus significantly accelerated by the propagating disturbance caused by the nearby filament eruption.”

Featured image: Schematic diagram of magnetic reconnection between loops accelerated by a nearby filament eruption. Two groups of fibrils marked by L2 and L4 converge and reconnect with each other. Two sets of newly formed fibrils marked by L1 and L3 then appear and retract away from the reconnection region. Credit: LI Leping


Reference: Leping Li et al. Magnetic Reconnection between Loops Accelerated By a Nearby Filament Eruption, The Astrophysical Journal (2021). DOI: 10.3847/1538-4357/abd47e


Provided by Chinese Academy of Sciences

How The Habitability of Exoplanets is Influenced By Their Rocks? (Planetary Science)

The weathering of silicate rocks plays an important role to keep the climate on Earth clement. Scientists led by the University of Bern and the Swiss national center of competence in research (NCCR) PlanetS, investigated the general principles of this process. Their results could influence how we interpret the signals from distant worlds—including such that may hint towards life.

The conditions on Earth are ideal for life. Most places on our planet are neither too hot nor too cold and offer liquid water. These and other requirements for life, however, delicately depend on the right composition of the atmosphere. Too little or too much of certain gases—like carbon dioxide—and Earth could become a ball of ice or turn into a pressure cooker. When scientists look for potentially habitable planets, a key component is therefore their atmosphere.

Sometimes, that atmosphere is primitive and largely consists of the gases that were around when the planet formed—as is the case for Jupiter and Saturn. On terrestrial planets like Mars, Venus or Earth, however, such primitive atmospheres are lost. Instead, their remaining atmospheres are strongly influenced by surface geochemistry. Processes like the weathering of rocks alter the composition the atmosphere and thereby influence the habitability of the planet.

How exactly this works, especially under conditions very different from those on Earth, is what a team of scientists, led by Kaustubh Hakim of the Centre for Space and Habitability (CSH) at the University of Bern and the NCCR PlanetS, investigated. Their results were published today in The Planetary Science Journal.

Conditions are decisive

“We want to understand how the chemical reactions between the atmosphere and the surface of planets change the composition of the atmosphere. On Earth, this process—the weathering of silicate rocks assisted by water—helps to maintain a temperate climate over long periods of time,” Hakim explains. “When the concentration of CO2 increases, temperatures also rise because of its greenhouse effect. Higher temperatures lead to more intense rainfall. Silicate weathering rates increase, which in turn reduce the CO2 concentration and subsequently lower the temperature,” says the researcher.

However, it need not necessarily work the same way on other planets. Using computer simulations, the team tested how different conditions affect the weathering process. For example, they found that even in very arid climates, weathering can be more intense than on Earth if the chemical reactions occur sufficiently quickly. Rock types, too, influence the process and can lead to very different weathering rates according to Hakim. The team also found that at temperatures of around 70°C, contrary to popular theory, silicate weathering rates can decrease with rising temperatures. “This shows that for planets with very different conditions than on Earth, weathering could play very different roles,” Hakim says.

Implications for habitability and life detection

If astronomers ever find a habitable world, it will likely be in what they call the habitable zone. This zone is the area around a star, where the dose of radiation would allow water to be liquid. In the solar system, this zone roughly lies between Mars and Venus.

“Geochemistry has a profound impact on the habitability of planets in the habitable zone,” study co-author and professor of astronomy and planetary sciences at the University of Bern and member of the NCCR PlanetS, Kevin Heng, points out. As the team’s results indicate, increasing temperatures could reduce weathering and its balancing effect on other planets. What would potentially be a habitable world could turn out to be a hellish greenhouse instead.

As Heng further explains, understanding geochemical processes under different conditions is not only important to estimate the potential for life, but also for its detection. “Unless we have some idea of the results of geochemical processes under varying conditions, we will not be able to tell whether bio-signatures—possible hints of life like the Phosphine that was found on Venus last year—indeed come from biological activity,” the researcher concludes.

Featured image: Weathering of silicate rocks is part of the so-called carbon cycle that maintains a temperate climate on Earth over long periods of time. Credit: University of Bern, Illustration: Jenny Leibundgut


Reference: Kaustubh Hakim et al. Lithologic Controls on Silicate Weathering Regimes of Temperate Planets, The Planetary Science Journal (2021). DOI: 10.3847/PSJ/abe1b8 https://iopscience.iop.org/article/10.3847/PSJ/abe1b8


Provided by University of Bern

Real-time Observation of Frequency Bloch Oscillations With Fibre Loop Modulation (Physics)

BOs describe the periodic movement of electrons in solids to which an external static electric field is applied. However, it is challenging to measure the BOs directly in natural solids since the relaxation time of electrons is usually much shorter than the oscillation period. To date, analogies of electron BOs have been extended to the synthetic dimensions of time, frequency and angular momenta. In previous studies, the frequency BOs have been experimentally demonstrated in a nonlinear fibre with cross-phase modulation. However, the frequency spectrum has been obtained only at the output of the fibre, and thus the evolution process of BOs has been measured only indirectly. In addition, frequency BOs have been theoretically demonstrated in micro-resonators under temporal modulation. Considering the compact structure of ring resonators, the direct observation of BOs still faces difficulties in compensating for the power reduction when collecting signals.

In a new paper published in Light Science & Application, a team of scientists, led by Professor Bing Wang from School of Physics and Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China, and co-workers have directly observed the frequency BOs in a modulated fibre loop with time detuning. The spectrum of the incident optical pulse experienced a periodic movement in the frequency lattice formed by the phase modulation. The time detuning produced an effective electric-field force in the lattice, which was associated with the effective vector potential varying with the spectrum evolution. Additionally, the transient evolution of the spectrum was measured in real time by using the dispersive Fourier transformation (DFT) technique. Based on the frequency-domain BOs, a maximum frequency shift up to 82 GHz was achieved. The bandwidth of the input pulse was also broadened up to 312 GHz. The study offers a promising approach to realizing BOs in synthetic dimensions and may find applications in frequency manipulations in optical fibre communication systems. These scientists summarize the principle of the work:

a-c Experimental results of the frequency BOs under a time detuning of 2, 5 and 8 ps. d-f Simulated BOs corresponding to the experimental results in a-c. g, h Amplitude and period of the BOs as a function of the time detuning. © by Hao Chen, NingNing Yang, Chengzhi Qin, Wenwan Li, Bing Wang, Tianwen Han, Chi Zhang, Weiwei Liu, Kai Wang, Hua Long, Xinliang Zhang and Peixiang Lu

“The phase modulation induces the coupling between the adjacent frequency modes which constructs a lattice in the frequency dimension. As the optical pulse propagates in fibre loop, the roundtrip time can be adjusted by using an optical delay line. A small time detuning can be introduced between the pulse circulation time and modulation period, which serves as an effective electric-field force in the frequency lattice and thus land thus gives rise to frequency BOs. We show that the vector potential can also contribute to generation of the effective force, which varies with the propagation distance. “

“To realize real-time measurement of the pulse spectrum coupled out from the loop, a spectroscope based on the DFT is connected at the end of the fibre-loop circuit. A long dispersion-compensating fibre performs a Fourier transform, which maps the spectrum envelope of the optical pulse into a time-domain waveform. Thanks to the dispersion in fibre, real-time measurement of the frequency spectrum with a resolution of ~9.8 GHz can be achieved.”

a-c Experimental spectrum evolution with time detuning of 2, 5 and 8 ps, respectively. d-f Numerical results corresponding to a-c. © by Hao Chen, NingNing Yang, Chengzhi Qin, Wenwan Li, Bing Wang, Tianwen Han, Chi Zhang, Weiwei Liu, Kai Wang, Hua Long, Xinliang Zhang and Peixiang Lu

“We implement the incidence of both short and broad pulses and directly observe the oscillating and breathing modes of frequency BOs. As the short pulse propagates in the fibre loop, one sees that the spectrum of the incident pulse evolves along a cosinoidal trajectory, referring to frequency BOs. For a broad pulse, the spectrum manifests a breathing pattern accompanied by a self-focusing effect during evolution.” they added.

“Based on the present method, the spectrum manipulations overcome the microelectronic bandwidth limitation. This study may find many applications in high-efficiency frequency conversion and signal processing. Additionally, in the aid of BOs, we verified that the vector gauge potential can be employed to manipulate the optical properties of photons in synthetic frequency lattice, which provides a unique way to control light, especially in the field of topological photonics.” the scientists forecast.

Featured image: CW Laser, continuous-wave laser; ML Laser, mode-locked laser; BPF, bandpass filter; PC, polarization controller; AWG, arbitrary waveform generation; IM, intensity modulator; PBS, polarization beam splitter; FC, fibre coupler; RF, radio-frequency signal generator; EA, electrical amplifier; VA, variable attenuator; ODL, optical delay line; DCF, dispersion-compensating fibre; ISO, isolator; LD, laser diode; WDM, wavelength-division multiplexer; EDF, erbium-doped fibre; PD, photodetector; OSC, oscilloscope; OSA, optical spectrum analyser. © by Hao Chen, NingNing Yang, Chengzhi Qin, Wenwan Li, Bing Wang, Tianwen Han, Chi Zhang, Weiwei Liu, Kai Wang, Hua Long, Xinliang Zhang and Peixiang Lu


Reference: Chen, H., Yang, N., Qin, C. et al. Real-time observation of frequency Bloch oscillations with fibre loop modulation. Light Sci Appl 10, 48 (2021). https://www.nature.com/articles/s41377-021-00494-w https://doi.org/10.1038/s41377-021-00494-w


Provided by CIOMP

“Silent” Heart Attacks May Increase Risk of Stroke (Medicine)

Research Highlights:

  • Silent or unrecognized heart attacks may increase future stroke risk.
  • Researchers suggest silent heart attacks may be a new risk factor for stroke among adults 65 and older.
  • More research is needed to understand how best to prevent stroke among patients who have had a silent heart attack.

Silent heart attacks appear to increase stroke risk in adults 65 and older, according to preliminary research to be presented at the American Stroke Association International Stroke Conference 2021. The virtual meeting is March 17-19, 2021 and is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.

A silent heart attack, also known as a silent myocardial infarction, has no, minimal or unrecognized symptoms. An electrocardiogram (ECG) or some form of imaging of the heart like an echocardiogram or a cardiac magnetic resonance imaging (MRI) is needed for diagnosis.

“Long-term risk of death can be as high after a silent heart attack as it is with a recognized heart attack, and it turns out silent heart attacks are more frequent than traditional chest-crushing heart attacks in older adults,” said study author Alexander E. Merkler, M.D., assistant professor of neurology at Weill Cornell Medicine in New York City. “We found having a silent heart attack increases stroke risk, suggesting silent heart attacks may need to be recognized as a new risk factor for stroke.”

Merkler and colleagues analyzed health information on more than 4,200 adults who participated in the Cardiovascular Health Study. Participants were 65 years old or older at the start of the study and were enrolled from 1989-1990. Participants had annual study visits from 1989-1999 at multiple centers across the U.S. Researchers evaluated participants’ stroke risk for an average of 10 years, with follow-up through June 30, 2015.

Researchers found:

  • Participants who had evidence of a silent heart attack had a 47% increased risk of developing a stroke, compared to adults who did not have a silent heart attack.
  • Participants who had classic symptoms for a heart attack had an 80-fold increased risk of stroke within one month after their heart attack, compared to participants who were heart attack-free.
  • After the high-risk, one-month period, participants with classic symptoms for a heart attack had a 60% increased risk of having a stroke.

“Our research suggests the increased risk for having a stroke in those with silent heart attacks is similar to the risk found in traditional heart attacks. A silent heart attack may be capable of causing clots in the heart that dislodge and travel to the brain causing a stroke,” Merkler said.

The research indicates patients with evidence of a silent heart attack found on an ECG should be considered as having an increased risk of stroke.

“More research is needed to understand how best to treat patients with silent heart attacks to prevent stroke,” Merkler noted. “It may also be worthwhile to conduct studies aimed at evaluating whether routine cardiac evaluation for silent heart attacks is warranted in order to help stratify the risk of stroke.”

A major limitation of the study is that the majority of study participants were white. The results might not be applicable to younger adults or adults of other races or ethnic groups.

Co-authors of the study are Traci M. Bartz, M.S.; Hooman Kamel, M.D., M.S.; Elsayed Z. Soliman, M.D., M.Sc., M.S.; Virginia Howard, Ph.D.; Bruce M. Psaty, M.D., Ph.D.; Peter M. Okin, M.D.; Monika M. Safford, M.D.; Mitchell S.V. Elkind, M.D., M.S.; and W. T. Longstreth Jr., M.D., M.P.H. The authors’ disclosures are listed in the abstract.

The National Heart, Lung, and Blood Institute, the National Institute of Neurological Disorders and Stroke and the National Institute on Aging of the National Institutes of Health funded the study.

Featured image credit: American Heart Association


Provided by Heart

Not So Fast, Supernova: Highest-energy Cosmic Rays Detected in Star Clusters (Planetary Science)

The highest-energy cosmic rays come from subatomic interactions within star clusters, not supernovae, say Michigan Tech physicists and collaborators.

For decades, researchers assumed the cosmic rays that regularly bombard Earth from the far reaches of the galaxy are born when stars go supernova — when they grow too massive to support the fusion occurring at their cores and explode.

Those gigantic explosions do indeed propel atomic particles at the speed of light great distances. However, new research suggests even supernovae — capable of devouring entire solar systems — are not strong enough to imbue particles with the sustained energies needed to reach petaelectronvolts (PeVs), the amount of kinetic energy attained by very high-energy cosmic rays.

And yet cosmic rays have been observed striking Earth’s atmosphere at exactly those velocities, their passage marked, for example, by the detection tanks at the High-Altitude Water Cherenkov (HAWC) observatory near Puebla, Mexico. Instead of supernovae, the researchers posit that star clusters like the Cygnus Cocoon serve as PeVatrons — PeV accelerators — capable of moving particles across the galaxy at such high energy rates.

Their paradigm-shifting research provides compelling evidence for star forming regions to be PeVatrons and is published in two recent papers in Nature Astronomy and Astrophysical Journal Letters.

A characteristic of physics research is how collaborative it is. The research was conducted by Petra Huentemeyer, professor of physics at Michigan Technological University, along with recent graduate Binita Hona ’20, doctoral student Dezhi Huang, former MTU postdoc Henrike Fleischhack (now at Catholic University/NASA GSFC/CRESST II), Sabrina Casanova at the Institute of Nuclear Physics Polish Academy of Sciences in Krakow, Ke Fang at the University of Wisconsin and Roger Blanford at Stanford, along with numerous other collaborators of the HAWC Observatory.

What are PeVatrons?

PeVatrons are believed to be highest-energy sources of cosmic rays in our galaxy, and their definitive identification has so far been elusive. PeVatrons accelerate protons to petaelectronvolts (PeVs), an enormous amount of kinetic energy capable of slinging subatomic particles light-years across the galaxy.

From Whence They Came

Huentemeyer noted that HAWC and physicists from other institutions have measured cosmic rays from all directions and across many decades of energy. It’s in tracking the cosmic rays with the highest known energy, PeVs, that their origin becomes so important.

“Cosmic rays below PeV energy are believed to come from our galaxy, but the question is what are the accelerators that can produce them,” Huentemeyer said.

Fleischhack said the paradigm shift the researchers have uncovered is that before, scientists thought supernova remnants were the main accelerators of cosmic rays.

“They do accelerate cosmic rays, but they are not able to get to highest energies,” she said.

So, what is driving cosmic rays’ acceleration to PeV energy?

“There have been several other hints that star clusters could be part of the story,” Fleischhack said. “Now we are getting confirmation that they are able to go to highest energies.”

Star clusters are formed from the remnants of a supernova event. Known as star cradles, they contain violent winds and clouds of swirling debris — such as those noted by the researchers in Cygnus OB2 and cluster [BDS2003]8. Inside, several types of massive stars known as spectral type O and type B stars are gathered by the hundreds in an area about 30 parsecs (108 light-years) across.

“Spectral type O stars are the most massive,” Hona said. “When their winds interact with each other, shock waves form, which is where acceleration happens.”

The researchers’ theoretical models suggest that the energetic gamma-ray photons seen by HAWC are more likely produced by protons than by electrons.

“We will use NASA telescopes to search for the counterpart emission by these relativistic particles at lower energies,” Fang said.

The Cherenkov light detectors at the High-Altitude Water Cherenkov observatory. Image Credit: HAWC

Ingredients for Acceleration

The extremely high energy at which cosmic rays reach our planet is notable. Specific conditions are required to accelerate particles to such velocities.

The higher the energy, the more difficult it is to confine the particles — knowledge gleaned from particle accelerators here on Earth in Chicago and Switzerland. To keep particles from whizzing away, magnetism is required.

Stellar clusters — with their mixture of wind and nascent but powerful stars — are turbulent regions with different magnetic fields that can provide the confinement necessary for particles to continue to accelerate.

“Supernova remnants have very fast shocks where the cosmic ray can be accelerated; however, they don’t have the type of long confinement regions,” Casanova said. “This is what star clusters are useful for. They’re an association of stars that can create disturbances that confine the cosmic rays and make it possible for the shocks to accelerate them.”

But how is it possible to measure atomic interactions on a galactic scale 5,000 light-years from Earth? The researchers used 1,343 days of measurements from HAWC detection tanks.

Huang explained how the physicists at HAWC trace cosmic rays by measuring the gamma rays these cosmic rays produce at galactic acceleration sites: “We didn’t measure gamma rays directly; we measured the secondary rays generated. When gamma rays interact with the atmosphere, they generate secondary particles in particle showers.”

“When particle showers are detected at HAWC, we can measure the shower and the charge of secondary particles,” Huang said. “We use the particle charge and time information to reconstruct information from the primary gamma.”

What is a Cherenkov light detector?

A graphic depiction of the how Cherenkov light detectors function. Click image to expand. Image Credit: SWGO

More than 300 massive water tanks at HAWC sit waiting for cosmic ray showers — shower of particles that moves at nearly the speed of light toward the ground. When the particles hit the tanks, they produce coordinated flashes of blue light in the water, allowing researchers to reconstruct the energy and cosmic origin of the gamma ray that kicked off the cascade.

More Eyes on the Skies

In addition to HAWC, the researchers plan to work with the Southern Wide-field Gamma-ray Observatory (SWGO), an observatory currently in the planning stages that will feature Cherenkov light detectors like HAWC but will be located in the southern hemisphere.

“It would be interesting to see what we can see in the southern hemisphere,” Huentemeyer said. “We will have a good view of the galactic center that we don’t have in the northern hemisphere. SWGO could give us many more candidates in terms of star clusters.”

Future collaborations across hemispheres promise to help scientists around the world continue to explore the origins of cosmic rays and learn more about the galaxy itself.

Grants and Funding

This research is funded by the National Science Foundation (NSF), the U.S. Department of Energy Office of Science, the LDRD program of Los Alamos National Laboratory, CONACyT, México, and the Polish Science Centre (among others).

Featured image: A 24 micrometer infrared map from the Cocoon region with Spitzers MIPS overlaid with a gamma-ray significance map from HAWC (greenish-yellow to red indicate higher gamma-ray significance). The map is centered at Cocoon with about 4.6 degrees in x and y direction. Image Credit: Binita Hona

Reference: Huentemeyer, P. (2021). HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon. Nature Astronomy. http://doi.org/10.1038/s41550-021-01318-y


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First Lab-grown Mini-thyroids Use Patients Own Tissue (Biology)

New research unlocks new clues for treating hypothyroidism

Hormones produced by the thyroid gland are essential regulators of organ function. The absence of these hormones either through thyroid dysfunction due to, for example, irradiation, thyroid cancer or autoimmune disease or thyroidectomy leads to symptoms like fatigue, feeling cold, constipation, and weight gain. The condition called hypothyroidism is estimated to affect up to 11% of the global population. Although hypothyroidism can be treated by hormone replacement therapy, some patients have persistent symptoms and/or experience side effects. To investigate potential alternative treatment strategies for these patients, researchers have now for the first time succeeded in generating thyroid mini-organs in the lab. In a new study published in Stem Cell ReportsRobert Coppes and colleagues from the University of Groningen, the Netherlands, used healthy thyroid tissue from patients undergoing surgical removal of the thyroid to grow mini-thyroid organs in a lab which resembled thyroid glands in their structure and protein content. The thyroid mini-organs contained stem cells which re-grew and formed new mini-organs when the structures were dissociated, providing a potentially unlimited source of lab-grown thyroid tissue. Importantly, the thyroid mini-organs could be matured and produced thyroid hormones in the cultures. Preliminary proof that these structures could potentially replace thyroid tissue came from experiments in mice with hypothyroidism, where transplantation of the mini-organs increased serum levels of thyroid hormones and extended the lifespan of the animals compared to un-transplanted mice. Further studies are required, however the study lays the foundation for generating thyroid mini-organs from surgically removed tissue and may potentially lead to a new therapy for hypothyroidism in the future.

Featured image: Human thyroid organoid displaying functionality through thyroglobulin (green) production and proliferative capacity by Ki67 (red). © Vivian ML Ogundipe


Paper title: Generation and Differentiation of Adult Tissue-Derived Human Thyroid Organoids


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Adding Triglyceride-lowering Omega-3 Based Medication To Statins May Lower Stroke Risk (Medicine)

Research Highlights:

  • Adding the triglyceride-lowering medication icosapent ethyl cut the risk of a first stroke by an additional 36% in patients already taking statin medications to treat high cholesterol.
  • In previous research, icosapent ethyl reduced the risk of major cardiovascular events.
  • The prescription medication is a highly purified form of an omega-3 fatty acid. The study’s results do not apply to supplements available over-the-counter.

Taking the triglyceride-lowering medication icosapent ethyl cut the risk of stroke by an additional 36% in people at increased risk of cardiovascular disease who already have their bad cholesterol levels under control using statin medications, according to preliminary research to be presented at the American Stroke Association’s International Stroke Conference 2021. The virtual meeting is March 17-19, 2021 and is a world premier meeting for researchers and clinicians dedicated to the science of stroke and brain health.

“Icosapent ethyl is a new way to further reduce the risk of stroke in patients with atherosclerosis or who are at high risk of stroke, who have elevated triglyceride levels and are already taking statins,” said Deepak L. Bhatt, M.D., M.P.H., lead author of the study and executive director of interventional cardiovascular programs at the Brigham and Women’s Hospital Heart & Vascular Center in Boston.

Icosapent ethyl is a prescription medication that is a highly purified form of the omega-3 fatty acid eicosapentaenoic acid. “It is very different in terms of purity compared to omega-3 fatty acid supplements available over-the-counter, and these results do not apply to supplements,” said Bhatt, who is also professor of medicine at Harvard Medical School.

Icosapent ethyl was first approved in July 2012 by the U.S. Food and Drug Administration as an adjunct treatment to dietary changes to lower triglycerides in people with extremely high levels of triglycerides (higher than 500 mg/dL). Triglycerides are fats from food that are carried in the blood; normal levels for an adult are below 150 mg/dL.

In late 2018, the REDUCE-IT trial, an 8,000-person multinational study, demonstrated that icosapent ethyl could benefit people with heart disease, diabetes or triglyceride levels above 150 mg/dL and whose LDL (bad) cholesterol levels were already under control using statin medication. In the trial, adding icosapent ethyl (compared with a placebo) reduced the risk of serious cardiovascular events (heart attack, heart-related death, stroke, need for an artery-opening procedure or hospitalization for heart-related chest pain) by 25%.

In December 2019, the FDA approved icosapent ethyl as a secondary treatment to reduce the risk of cardiovascular events among adults with elevated triglyceride levels, and it is now recommended in some professional guidelines. Icosapent ethyl is not included in the American Heart Association’s 2018 Cholesterol Guidelines that were published online prior to the availability of the REDUCE-IT primary results.

In the current analyses, REDUCE-IT Stroke, researchers performed an additional analysis of the impact of icosapent ethyl on stroke in the same 8,000 participants of the original REDUCE-IT trial. They found:

  • the risk of a first fatal or nonfatal ischemic stroke was reduced by 36% for patients treated with icosapent ethyl;
  • for every 1,000 patients treated with icosapent ethyl for 5 years, about 14 strokes were averted; and
  • the risk of a bleeding stroke was very low, and no difference was found among those taking icosapent ethyl.

“Know your triglyceride levels. If they are elevated, ask your doctor if you should be taking icosapent ethyl to further reduce your risk of heart attack and stroke,” Bhatt said. “Your doctor may also recommend that you change your diet, exercise, lose weight if needed to lower your triglyceride levels, and may prescribe a statin medication if you need to lower your LDL cholesterol levels.”

“One study limitation is that icosapent ethyl may increase the risk of minor bleeding,” Bhatt added.

Co-authors are Gabriel Steg, M.D.; Michael Miller, M.D.; Eliot A. Brinton, M.D.; Terry A. Jacobson, M.D.; Steven B. Ketchum, Ph.D.; Rebecca A. Juliano, Ph.D.; Lixia Jiao, Ph.D.; Ralph T. Doyle Jr., B.A.; Craig Granowitz, M.D., Ph.D.; Jean-Claude Tardif, M.D.; John Gregson, Ph.D.; C. Michael Gibson, M.D.; Megan C. Leary, M.D.; and Christie M. Ballantyne, M.D. The author’s disclosures are listed in the abstract.

The study was funded by Amarin Pharma.


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