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A warm Jupiter orbiting a cool star

A planet observed crossing in front of, or transiting, a low-mass star has been determined to be about the size of Jupiter. While hundreds of Jupiter-sized planets have been discovered orbiting larger sun-like stars, it is rare to see these planets orbiting low-mass host stars and the discovery could help astronomers to better understand how these giant planets form.

“This is only the fifth Jupiter-sized planet transiting a low-mass star that has been observed and the first with such a long orbital period, which makes this discovery really exciting,” said Caleb Cañas, lead author of the paper and a Ph.D. student at Penn State and NASA Earth and Space Science Fellow.

Originally detected by NASA’s Transiting Exoplanet Survey Satellite (TESS) spacecraft, astronomers characterized the planet’s mass, radius, and its orbital period using the Habitable-zone Planet Finder (HPF), an astronomical spectrograph built by a Penn State team and installed on the 10m Hobby-Eberly Telescope at McDonald Observatory in Texas. A paper describing the research appears in the September 2020 issue of the Astronomical Journal and is publicly accessible on arXiv.

“A transiting Jupiter-sized planet is amenable to further observations to see how well the orbit is aligned with the spin-axis of the host star and to constrain how it could have formed,” said Cañas. “Furthermore, the low mass of the host star and the long orbital period result in a Jupiter with a moderate temperature compared to similar planets detected with NASA’s Kepler space telescope.”

The host star, TOI-1899, is a low-mass (M dwarf) star about 419 light years away from Earth. The planet, TOI-1899 b, is two-thirds the mass of Jupiter, ten percent larger in radius than Jupiter, and is 0.16 astronomical units (AU) — a measure defined as the distance between the Earth and the sun — from its host star such that a full year on TOI-1899 takes only 29 Earth days. For comparison, the four other transiting Jupiter-size planets around comparable stars complete their orbits in less than 4 days.

The planet was detected by TESS using the transit method, which searches for stars showing periodic dips in their brightness as a telltale sign of an orbiting object crossing in front of the star and blocking a portion of its light. The signal was later confirmed as a planet using precision observations from the HPF spectrograph that measure the planet’s mass by analyzing how it causes its host start to the wobble.

From a formation and orbital evolution perspective, there is not a clear dividing line between warm Jupiters and the large planets even closer to their host stars, the more commonly discovered hot Jupiters.

“Warm Jupiters like TOI-1899 b orbit surprisingly close to their star,” said Rebekah Dawson, assistant professor of astronomy and astrophysics at Penn State and an author of the paper. “Even though the planet’s orbital period is long compared to many other giant planets detected and characterized through the transit method, it still places the giant planet much closer to its star than we’d expect from classical formation theories. Detailed characterization of their physical and orbital properties, system architecture, and host stars — as the HPF team has done for TOI-1899 b — allow us test theories for how giant planets can form or be displaced so close to their star.”

The Habitable-zone Planet Finder was delivered to the 10m Hobby Eberly Telescope at McDonald Observatory in late 2017, and started full science operations in late 2018. HPF is designed to detect and characterize planets in the Habitable-zone — the region around the star where a planet could sustain liquid water on its surface — around nearby M-dwarf stars, but is also capable of making sensitive measurements for planets outside the habitable zone.

“This warm Jupiter is a compelling target for atmospheric characterization with upcoming missions like the James Webb Space Telescope,” said Suvrath Mahadevan, professor of astronomy and astrophysics at Penn State, the principal investigator of the HPF spectrograph, and an author of the paper. “HPF was critical in helping us to confirm this, but detecting a second transit is important to very precisely pin down its period.”

In addition to data from HPF, additional data were obtained with the 3.5m Telescope at the Kitt Peak National Observatory (KPNO) in Arizona and the 3m Shane Telescope at Lick Observatory for high contrast imaging and photometric observations with the 0.9m WIYN Telescope at KPNO, 0.5 m ARCSAT telescope at Apache Point Observatory, and the 0.43 m telescope at the Richard S. Perkin Observatory in New York.

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Europe’s largest Solar Telescope GREGOR unveils magnetic details of the Sun

The Sun is our star and has a profound influence on our planet, life, and civilization. By studying the magnetism on the Sun, we can understand its influence on Earth and minimize damage of satellites and technological infrastructure. The GREGOR telescope allows scientists to resolve details as small as 50 km on the Sun, which is a tiny fraction of the solar diameter of 1.4 million km. This is as if one saw a needle on a soccer field perfectly sharp from a distance of one kilometer.

“This was a very exciting, but also extremely challenging project. In only one year we completely redesigned the optics, mechanics, and electronics to achieve the best possible image quality.” said Dr. Lucia Kleint, who led the project and the German solar telescopes on Tenerife. A major technical breakthrough was achieved by the project team in March this year, during the lockdown, when they were stranded at the observatory and set up the optical laboratory from the ground up. Unfortunately, snow storms prevented solar observations. When Spain reopened in July, the team immediately flew back and obtained the highest resolution images of the Sun ever taken by a European telescope.

Prof. Dr. Svetlana Berdyugina, professor at the Albert-Ludwig University of Freiburg and Director of the Leibniz Institute for Solar Physics (KIS), is very happy about the outstanding results: “The project was rather risky because such telescope upgrades usually take years, but the great team work and meticulous planning have led to this success. Now we have a powerful instrument to solve puzzles on the Sun.” The new optics of the telescope will allow scientists to study magnetic fields, convection, turbulence, solar eruptions, and sunspots in great detail. First light images obtained in July 2020 reveal astonishing details of sunspot evolution and intricate structures in solar plasma.

Telescope optics are very complex systems of mirrors, lenses, glass cubes, filters and further optical elements. If only one element is not perfect, for example due to fabrication issues, the performance of the whole system suffers. This is similar to wearing glasses with the wrong prescription, resulting in a blurry vision. Unlike for glasses, it is however very challenging to detect which elements in a telescope may be causing issues. The GREGOR team found several of those issues and calculated optics models to solve them. For example, astigmatism is one of such optical problems, which affects 30-60% people’s vision, but also complex telescopes. At GREGOR this was corrected by replacing two elements with so-called off-axis parabolic mirrors, which had to be polished to 6 nm precision, about 1/10000 of the diameter of a hair. Combined with several further enhancements the redesign led to the sharp vision of the telescope. A technical description of the redesign was recently published by the Astronomy & Astrophysics journal in a recent article led by Dr. L. Kleint.

European researchers have access to observations with the GREGOR telescope through national programs and a program funded by the European commission. New scientific observations are starting in September 2020.

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New observations of black hole devouring a star reveal rapid disk formation

When a star passes too close to a supermassive black hole, tidal forces tear it apart, producing a bright flare of radiation as material from the star falls into the black hole. Astronomers study the light from these “tidal disruption events” (TDEs) for clues to the feeding behavior of the supermassive black holes lurking at the centers of galaxies.

New TDE observations led by astronomers at UC Santa Cruz now provide clear evidence that debris from the star forms a rotating disk, called an accretion disk, around the black hole. Theorists have been debating whether an accretion disk can form efficiently during a tidal disruption event, and the new findings, accepted for publication in the Astrophysical Journal and available online, should help resolve that question, said first author Tiara Hung, a postdoctoral researcher at UC Santa Cruz.

“In classical theory, the TDE flare is powered by an accretion disk, producing x-rays from the inner region where hot gas spirals into the black hole,” Hung said. “But for most TDEs, we don’t see x-rays — they mostly shine in the ultraviolet and optical wavelengths — so it was suggested that, instead of a disk, we’re seeing emissions from the collision of stellar debris streams.”

Coauthors Enrico Ramirez-Ruiz, professor of astronomy and astrophysics at UCSC, and Jane Dai at the University of Hong Kong developed a theoretical model, published in 2018, that can explain why x-rays are usually not observed in TDEs despite the formation of an accretion disk. The new observations provide strong support for this model.

“This is the first solid confirmation that accretion disks form in these events, even when we don’t see x-rays,” Ramirez-Ruiz said. “The region close to the black hole is obscured by an optically thick wind, so we don’t see the x-ray emissions, but we do see optical light from an extended elliptical disk.”

The telltale evidence for an accretion disk comes from spectroscopic observations. Coauthor Ryan Foley, assistant professor of astronomy and astrophysics at UCSC, and his team began monitoring the TDE (named AT 2018hyz) after it was first detected in November 2018 by the All Sky Automated Survey for SuperNovae (ASAS-SN). Foley noticed an unusual spectrum while observing the TDE with the 3-meter Shane Telescope at UC’s Lick Observatory on the night of January 1, 2019.

“My jaw dropped, and I immediately knew this was going to be interesting,” he said. “What stood out was the hydrogen line — the emission from hydrogen gas — which had a double-peaked profile that was unlike any other TDE we’d seen.”

Foley explained that the double peak in the spectrum results from the Doppler effect, which shifts the frequency of light emitted by a moving object. In an accretion disk spiraling around a black hole and viewed at an angle, some of the material will be moving toward the observer, so the light it emits will be shifted to a higher frequency, and some of the material will be moving away from the observer, its light shifted to a lower frequency.

“It’s the same effect that causes the sound of a car on a race track to shift from a high pitch as the car comes toward you to a lower pitch when it passes and starts moving away from you,” Foley said. “If you’re sitting in the bleachers, the cars on one turn are all moving toward you and the cars on the other turn are moving away from you. In an accretion disk, the gas is moving around the black hole in a similar way, and that’s what gives the two peaks in the spectrum.”

The team continued to gather data over the next few months, observing the TDE with several telescopes as it evolved over time. Hung led a detailed analysis of the data, which indicates that disk formation took place relatively quickly, in a matter of weeks after the disruption of the star. The findings suggest that disk formation may be common among optically detected TDEs despite the rarity of double-peaked emission, which depends on factors such as the inclination of the disk relative to observers.

“I think we got lucky with this one,” Ramirez-Ruiz said. “Our simulations show that what we observe is very sensitive to the inclination. There is a preferred orientation to see these double-peak features, and a different orientation to see x-ray emissions.”

He noted that Hung’s analysis of multi-wavelength follow-up observations, including photometric and spectroscopic data, provides unprecedented insights into these unusual events. “When we have spectra, we can learn a lot about the kinematics of the gas and get a much clearer understanding of the accretion process and what is powering the emissions,” Ramirez-Ruiz said.

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Beam me up: Researchers use ‘behavioral teleporting’ to study social interactions

Teleporting is a science fiction trope often associated with Star Trek. But a different kind of teleporting is being explored at the NYU Tandon School of Engineering, one that could let researchers investigate the very basis of social behavior, study interactions between invasive and native species to preserve natural ecosystems, explore predator/prey relationship without posing a risk to the welfare of the animals, and even fine-tune human/robot interfaces.

The team, led by Maurizio Porfiri, Institute Professor at NYU Tandon, devised a novel approach to getting physically separated fish to interact with each other, leading to insights about what kinds of cues influence social behavior.

The innovative system, called “behavioral teleporting” — the transfer of the complete inventory of behaviors and actions (ethogram) of a live zebrafish onto a remotely located robotic replica — allowed the investigators to independently manipulate multiple factors underpinning social interactions in real-time. The research, “Behavioral teleporting of individual ethograms onto inanimate robots: experiments on social interactions in live zebrafish,” appears in the Cell Press journal iScience.

The team, including Mert Karakaya, a Ph.D. candidate in the Department of Mechanical and Aerospace Engineering at NYU Tandon, and Simone Macrì of the Centre for Behavioral Sciences and Mental Health, Istituto Superiore di Sanità, Rome, devised a setup consisting of two separate tanks, each containing one fish and one robotic replica. Within each tank, the live fish of the pair swam with the zebrafish replica matching the morphology and locomotory pattern of the live fish located in the other tank.

An automated tracking system scored each of the live subjects’ locomotory patterns, which were, in turn, used to control the robotic replica swimming in the other tank via an external manipulator. Therefore, the system allowed the transfer of the complete ethogram of each fish across tanks within a fraction of a second, establishing a complex robotics-mediated interaction between two remotely-located live animals. By independently controlling the morphology of these robots, the team explored the link between appearance and movements in social behavior.

The investigators found that the replica teleported the fish motion in almost all trials (85% of the total experimental time), with a 95% accuracy at a maximum time lag of less than two-tenths of a second. The high accuracy in the replication of fish trajectory was confirmed by equivalent analysis on speed, turn rate, and acceleration.

Porfiri explained that the behavioral teleporting system avoids the limits of typical modeling using robots.

“Since existing approaches involve the use of a mathematical representation of social behavior for controlling the movements of the replica, they often lead to unnatural behavioral responses of live animals,” he said. “But because behavioral teleporting ‘copy/pastes’ the behavior of a live fish onto robotic proxies, it confers a high degree of precision with respect to such factors as position, speed, turn rate, and acceleration.”

Porfiri’s previous research proving robots are viable as behavior models for zebrafish showed that schools of zebrafish could be made to follow the lead of their robotic counterparts.

“In humans, social behavior unfolds in actions, habits, and practices that ultimately define our individual life and our society,” added Macrì. “These depend on complex processes, mediated by individual traits — baldness, height, voice pitch, and outfit, for example — and behavioral feedback, vectors that are often difficult to isolate. This new approach demonstrates that we canisolate influences on the quality of social interaction and determine which visual features really matter.”

The research included experiments to understand the asymmetric relationship between large and small fish and identify leader/follower roles, in which a large fish swam with a small replica that mirrored the behavior of the small fish positioned in the other tank and vice-versa.

Karakaya said the team was surprised to find that the smaller — not larger — fish “led” the interactions.

“There are no strongly conclusive results on why that could be, but one reason might be due to the ‘curious’ nature of the smaller individuals to explore a novel space,” he said. “In known environments, large fish tend to lead; however, in new environments larger and older animals can be cautious in their approach, whereas the smaller and younger ones could be ‘bolder.'”

The method also led to the discovery that interaction between fish was not determined by locomotor patterns alone, but also by appearance.

“It is interesting to see that, as is the case with our own species, there is a relationship between appearance and social interaction,” he added.

Karakaya added that this could serve as an important tool for human interactions in the near future, whereby, through the closed-loop teleporting, people could use robots as proxies of themselves.

“One example would be the colonies on Mars, where experts from Earth could use humanoid robots as an extension of themselves to interact with the environment and people there. This would provide easier and more accurate medical examination, improve human contact, and reduce isolation. Detailed studies on the behavioral and psychological effects of these proxies must be completed to better understand how these techniques can be implemented into daily life.”

This work was supported by the National Science Foundation, the National Institute on Drug Abuse, and the Office of Behavioral and Social Sciences Research.

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How colliding neutron stars could shed light on universal mysteries

An important breakthrough in how we can understand dead star collisions and the expansion of the Universe has been made by an international team, led by the University of East Anglia.

They have discovered an unusual pulsar — one of deep space’s magnetized spinning neutron-star ‘lighthouses’ that emits highly focused radio waves from its magnetic poles.

The newly discovered pulsar (known as PSR J1913+1102) is part of a binary system — which means that it is locked in a fiercely tight orbit with another neutron star.

Neutron stars are the dead stellar remnants of a supernova. They are made up of the most dense matter known — packing hundreds of thousands of times the Earth’s mass into a sphere the size of a city.

In around half a billion years the two neutron stars will collide, releasing astonishing amounts of energy in the form of gravitational waves and light.

But the newly discovered pulsar is unusual because the masses of its two neutron stars are quite different — with one far larger than the other.

This asymmetric system gives scientists confidence that double neutron star mergers will provide vital clues about unsolved mysteries in astrophysics — including a more accurate determination of the expansion rate of the Universe, known as the Hubble constant.

The discovery, published today in the journal Nature, was made using the Arecibo radio telescope in Puerto Rico.

Lead researcher Dr Robert Ferdman, from UEA’s School of Physics, said: “Back in 2017, scientists at the Laser Interferometer Gravitational-Wave Observatory (LIGO) first detected the merger of two neutron stars.

“The event caused gravitational-wave ripples through the fabric of space time, as predicted by Albert Einstein over a century ago.”

Known as GW170817, this spectacular event was also seen with traditional telescopes at observatories around the world, which identified its location in a distant galaxy, 130 million light years from our own Milky Way.

Dr Ferdman said: “It confirmed that the phenomenon of short gamma-ray bursts was due to the merger of two neutron stars. And these are now thought to be the factories that produce most of the heaviest elements in the Universe, such as gold.”

The power released during the fraction of a second when two neutron stars merge is enormous — estimated to be tens of times larger than all stars in the Universe combined.

So the GW170817 event was not surprising. But the enormous amount of matter ejected from the merger and its brightness was an unexpected mystery.

Dr Ferdman said: “Most theories about this event assumed that neutron stars locked in binary systems are very similar in mass.

“Our new discovery changes these assumptions. We have uncovered a binary system containing two neutron stars with very different masses.

“These stars will collide and merge in around 470 million years, which seems like a long time, but it is only a small fraction of the age of the Universe.

“Because one neutron star is significantly larger, its gravitational influence will distort the shape of its companion star — stripping away large amounts of matter just before they actually merge, and potentially disrupting it altogether.

“This ‘tidal disruption’ ejects a larger amount of hot material than expected for equal-mass binary systems, resulting in a more powerful emission.

“Although GW170817 can be explained by other theories, we can confirm that a parent system of neutron stars with significantly different masses, similar to the PSR J1913+1102 system, is a very plausible explanation.

“Perhaps more importantly, the discovery highlights that there are many more of these systems out there — making up more than one in 10 merging double neutron star binaries.”

Co-author Dr Paulo Freire from the Max Planck Institute for Radio Astronomy in Bonn, Germany, said: “Such a disruption would allow astrophysicists to gain important new clues about the exotic matter that makes up the interiors of these extreme, dense objects.

“This matter is still a major mystery — it’s so dense that scientists still don’t know what it is actually made of. These densities are far beyond what we can reproduce in Earth-based laboratories.”

The disruption of the lighter neutron star would also enhance the brightness of the material ejected by the merger. This means that along with gravitational-wave detectors such as the US-based LIGO and the Europe-based Virgo detector, scientists will also be able to observe them with conventional telescopes.

Dr Ferdman said: “Excitingly, this may also allow for a completely independent measurement of the Hubble constant — the rate at which the Universe is expanding. The two main methods for doing this are currently at odds with each other, so this is a crucial way to break the deadlock and understand in more detail how the Universe evolved.”

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Stellar fireworks celebrate birth of giant cluster

Astronomers created a stunning new image showing celestial fireworks in star cluster G286.21+0.17.

Most stars in the universe, including our Sun, were born in massive star clusters. These clusters are the building blocks of galaxies, but their formation from dense molecular clouds is still largely a mystery.

The image of cluster G286.21+0.17, caught in the act of formation, is a multi-wavelength mosaic made out of more than 750 individual radio observations with the Atacama Large Millimeter/submillimeter Array (ALMA) and 9 infrared images from the NASA/ESA Hubble Space Telescope. The cluster is located in the Carina region of our galaxy, about 8000 light-years away.

Dense clouds made of molecular gas (purple ‘fireworks streamers’) are revealed by ALMA. The telescope observed the motions of turbulent gas falling into the cluster, forming dense cores that ultimately create individual stars.

The stars in the image are revealed by their infrared light, as seen by Hubble, including a large group of stars bursting out from one side of the cloud. The powerful winds and radiation from the most massive of these stars are blasting away the molecular clouds, leaving faint wisps of glowing, hot dust (shown in yellow and red).

“This image shows stars in various stages of formation within this single cluster,” said Yu Cheng of the University of Virginia in Charlottesville, Virginia, and lead author of two papers published in The Astrophysical Journal.

Hubble revealed about a thousand newly-formed stars with a wide range of masses. Additionally, ALMA showed that there is a lot more mass present in dense gas that still has to undergo collapse. “Overall the process may take at least a million years to complete,” Cheng added.

“This illustrates how dynamic and chaotic the process of star birth is,” said co-author Jonathan Tan of Chalmers University in Sweden and the University of Virginia and principal investigator of the project. “We see competing forces in action: gravity and turbulence from the cloud on one side, and stellar winds and radiation pressure from the young stars on the other. This process sculpts the region. It is amazing to think that our own Sun and planets were once part of such a cosmic dance.”

“The phenomenal resolution and sensitivity of ALMA are evident in this stunning image of star formation,” said Joe Pesce, NSF Program Officer for NRAO/ALMA. “Combined with the Hubble Space Telescope data we can clearly see the power of multiwavelength observations to help us understand these fundamental universal processes.”

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First exposed planetary core discovered allows glimpse inside other worlds

The surviving core of a gas giant has been discovered orbiting a distant star by University of Warwick astronomers, offering an unprecedented glimpse into the interior of a planet.

The core, which is the same size as Neptune in our own solar system, is believed to be a gas giant that was either stripped of its gaseous atmosphere or that failed to form one in its early life.

The team from the University of Warwick’s Department of Physics reports the discovery today (1 July) in the journal Nature, and is thought to be the first time the exposed core of a planet has been observed.

It offers the unique opportunity to peer inside the interior of a planet and learn about its composition.

Located around a star much like our own approximately 730 light years away, the core, named TOI 849 b orbits so close to its host star that a year is a mere 18 hours and its surface temperature is around 1800K.

TOI 849 b was found in a survey of stars by NASA’s Transiting Exoplanet Survey Satellite (TESS), using the transit method: observing stars for the tell-tale dip in brightness that indicates that a planet has passed in front of them. It was located in the ‘Neptunian desert’ — a term used by astronomers for a region close to stars where we rarely see planets of Neptune’s mass or larger.

The object was then analysed using the HARPS instrument, on a program led by the University of Warwick, at the European Southern Observatory’s La Silla Observatory in Chile. This utilises the Doppler effect to measure the mass of exoplanets by measuring their ‘wobble’ — small movements towards and away from us that register as tiny shifts in the star’s spectrum of light.

The team determined that the object’s mass is 2-3 times higher than Neptune but it is also incredibly dense, with all the material that makes up that mass squashed into an object the same size.

Lead author Dr David Armstrong from the University of Warwick Department of Physics said: “While this is an unusually massive planet, it’s a long way from the most massive we know. But it is the most massive we know for its size, and extremely dense for something the size of Neptune, which tells us this planet has a very unusual history. The fact that it’s in a strange location for its mass also helps — we don’t see planets with this mass at these short orbital periods.

“TOI 849 b is the most massive terrestrial planet — that has an earth like density — discovered. We would expect a planet this massive to have accreted large quantities of hydrogen and helium when it formed, growing into something similar to Jupiter. The fact that we don’t see those gases lets us know this is an exposed planetary core.

“This is the first time that we’ve discovered an intact exposed core of a gas giant around a star.”

There are two theories as to why we are seeing the planet’s core, rather than a typical gas giant. The first is that it was once similar to Jupiter but lost nearly all of its outer gas through a variety of methods. These could include tidal disruption, where the planet is ripped apart from orbiting too close to its star, or even a collision with another planet. Large-scale photoevaporation of the atmosphere could also play a role, but can’t account for all the gas that has been lost.

Alternatively, it could be a ‘failed’ gas giant. The scientists believe that once the core of the gas giant formed then something could have gone wrong and it never formed an atmosphere. This could have occurred if there was a gap in the disc of dust that the planet formed from, or if it formed late and the disc ran out of material.

Dr Armstrong adds: “One way or another, TOI 849 b either used to be a gas giant or is a ‘failed’ gas giant.

“It’s a first, telling us that planets like this exist and can be found. We have the opportunity to look at the core of a planet in a way that we can’t do in our own solar system. There are still big open questions about the nature of Jupiter’s core, for example, so strange and unusual exoplanets like this give us a window into planet formation that we have no other way to explore.

“Although we don’t have any information on its chemical composition yet, we can follow it up with other telescopes. Because TOI 849 b is so close to the star, any remaining atmosphere around the planet has to be constantly replenished from the core. So if we can measure that atmosphere then we can get an insight into the composition of the core itself.”

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A binary star as a cosmic particle accelerator

Scientists have identified the binary star Eta Carinae as a new kind of source for very high-energy (VHE) cosmic gamma-radiation. Eta Carinae is located 7500 lightyears away in the constellation Carina in the Southern Sky and, based on the data collected, emits gamma rays with energies up to 400 gigaelectronvolts (GeV), some 100 billion times more than the energy of visible light.

With a specialised telescope in Namibia a DESY-led team of researchers has proven a certain type of binary star as a new kind of source for very high-energy cosmic gamma-radiation. Eta Carinae is located 7500 lightyears away in the constellation Carina (the ship’s keel) in the Southern Sky and, based on the data collected, emits gamma rays with energies all the way up to 400 gigaelectronvolts (GeV), some 100 billion times more than the energy of visible light. The team headed by DESY’s Stefan Ohm, Eva Leser and Matthias Füßling is presenting its findings, made at the gamma-ray observatory High Energy Stereoscopic System (H.E.S.S.), in the journal Astronomy & Astrophysics. An accompanying multimedia animation explains the phenomenon. “With such visualisations we want to make the fascination of research tangible,” emphasises DESY’s Director of Astroparticle Physics, Christian Stegmann.

Eta Carinae is a binary system of superlatives, consisting of two blue giants, one about 100 times, the other about 30 times the mass of our sun. The two stars orbit each other every 5.5 years in very eccentric elliptical orbits, their separation varying approximately between the distance from our Sun to Mars and from the Sun to Uranus. Both these gigantic stars fling dense, supersonic stellar winds of charged particles out into space. In the process, the larger of the two loses a mass equivalent to our entire Sun in just 5000 years or so. The smaller one produces a fast stellar wind travelling at speeds around eleven million kilometres per hour (about one percent of the speed of light).

A huge shock front is formed in the region where these two stellar winds collide, heating up the material in the wind to extremely high temperatures. At around 50 million degrees Celsius, this matter radiates brightly in the X-ray range. The particles in the stellar wind are not hot enough to emit gamma radiation, though. “However, shock regions like this are typically sites where subatomic particles are accelerated by strong prevailing electromagnetic fields,” explains Ohm, who is the head of the H.E.S.S. group at DESY. When particles are accelerated this rapidly, they can also emit gamma radiation. In fact, the satellites “Fermi,” operated by the US space agency NASA, and AGILE, belonging to the Italian space agency ASI, already detected energetic gamma rays of up to about 10 GeV coming from Eta Carinae in 2009.

“Different models have been proposed to explain how this gamma radiation is produced,” Füßling reports. “It could be generated by accelerated electrons or by high-energy atomic nuclei.” Determining which of these two scenarios is correct is crucial: very energetic atomic nuclei account for the bulk of the so-called Cosmic Rays, a subatomic cosmic hailstorm striking Earth constantly from all directions. Despite intense research for more than 100 years, the sources of the Cosmic Rays are still not exhaustively known. Since the electrically charged atomic nuclei are deflected by cosmic magnetic fields as they travel through the universe, the direction from which they arrive at Earth no longer points back to their origin. Cosmic gamma rays, on the other hand, are not deflected. So, if the gamma rays emitted by a specific source can be shown to originate from high-energy atomic nuclei, one of the long-sought accelerators of cosmic particle radiation will have been identified.

“In the case of Eta Carinae, electrons have a particularly hard time getting accelerated to high energyies, because they are constantly being deflected by magnetic fields during their acceleration, which makes them lose energy again,” says Leser. “Very high-energy gamma radiation begins above the 100 GeV range, which is rather difficult to explain in Eta Carinae to stem from electron acceleration.” The satellite data already indicated that Eta Carinae also emits gamma radiation beyond 100 GeV, and H.E.S.S. has now succeeded in detecting such radiation up to energies of 400 GeV around the time of the close encounter of the two blue giants in 2014 and 2015. This makes the binary star the first known example of a source in which very high-energy gamma radiation is generated by colliding stellar winds.

“The analysis of the gamma radiation measurements taken by H.E.S.S. and the satellites shows that the radiation can best be interpreted as the product of rapidly accelerated atomic nuclei,” says DESY’s PhD student Ruslan Konno, who has published a companion study, together with scientists from the Max Planck Institute for Nuclear Physics in Heidelberg. “This would make the shock regions of colliding stellar winds a new type of natural particle accelerator for cosmic rays.” With H.E.S.S., which is named after the discoverer of Cosmic Rays, Victor Franz Hess, and the upcoming Cherenkov Telescope Array (CTA), the next-generation gamma-ray observatory currently being built in the Chilean highlands, the scientists hope to investigate this phenomenon in greater detail and discover more sources of this kind.

“I find science and scientific research extremely important,” says Nicolai, who sees close parallels in the creative work of artists and scientists. For him, the appeal of this work also lay in the artistic mediation of scientific research results: “particularly the fact that it is not a film soundtrack, but has a genuine reference to reality,” emphasizes the musician and artist. Together with the exclusively composed sound, this unique collaboration of scientists, animation artists and musician has resulted in a multimedia work that takes viewers on an extraordinary journey to a superlative double star some 7500 light years away.

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Hubble watches the ‘flapping’ of cosmic bat shadow in the Serpens Nebula

The young star HBC 672 is known by its nickname of Bat Shadow because of its wing-like shadow feature. The NASA/ESA Hubble Space Telescope has now observed a curious “flapping” motion in the shadow of the star’s disc for the first time. The star resides in a stellar nursery called the Serpens Nebula, about 1300 light-years away.

The Hubble Space Telescope captured a striking observation of the fledgling star’s unseen, planet-forming disc in 2018. This disc casts a huge shadow across a more distant cloud in a star-forming region — like a fly wandering into the beam of a flashlight shining on a wall.

Now, astronomers have serendipitously observed the Bat Shadow’s “flapping.” This may have been caused by a planet pulling on the disc and warping it. “You have a star that is surrounded by a disc, and the disc is not like Saturn’s rings — it’s not flat. It’s puffed up. And so that means that the light from the star, if it goes straight up, can continue straight up — it’s not blocked by anything. But if it tries to go along the plane of the disc, it doesn’t get out, and it casts a shadow,” explained lead author Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, USA, whose team have published these results.

This “flapping” finding was also a surprise. Pontoppidan and his team observed the shadow in several filters over a period of 13 months. When they combined the old and new images, the shadow appeared to have moved.

The shadow is so large — about 200 times the diameter of our Solar System — that light doesn’t travel instantaneously across it. In fact, it takes about 45 days for the light to travel from the star out to the best defined edge of the shadow.

Pontoppidan and his team calculate that a planet warping the disc would orbit its star in no fewer than 180 days. They estimate that it would be about the same distance from its star as Earth is from the Sun. Pontoppidan’s team also suggest the disc must be flared, with an angle that increases with distance — like a trumpet. This shape of its two peaks and two dips would explain the “flapping” of the shadow. The team also speculates that a planet is embedded in the disc, inclined to the disc’s plane. If it’s not a planet, a less likely explanation is a lower-mass stellar companion orbiting HBC 672 outside the plane of the disc. Pontoppidan and his team doubt this is the case, based on the thickness of the disc. There is also no current evidence for a binary companion).

The disc is a circling structure of gas, dust, and rock, and is too small and too distant to be seen, even by Hubble. However, based on the projected shadow, scientists do know that its height-to-radius ratio is 1:5.

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Is teleportation possible? Yes, in the quantum world

“Beam me up” is one of the most famous catchphrases from the Star Trek series. It is the command issued when a character wishes to teleport from a remote location back to the Starship Enterprise.

While human teleportation exists only in science fiction, teleportation is possible in the subatomic world of quantum mechanics — albeit not in the way typically depicted on TV. In the quantum world, teleportation involves the transportation of information, rather than the transportation of matter.

Last year scientists confirmed that information could be passed between photons on computer chips even when the photons were not physically linked.

Now, according to new research from the University of Rochester and Purdue University, teleportation may also be possible between electrons.

In a paper published in Nature Communications and one to appear in Physical Review X, the researchers, including John Nichol, an assistant professor of physics at Rochester, and Andrew Jordan, a professor of physics at Rochester, explore new ways of creating quantum-mechanical interactions between distant electrons. The research is an important step in improving quantum computing, which, in turn, has the potential to revolutionize technology, medicine, and science by providing faster and more efficient processors and sensors.

‘SPOOKY ACTION AT A DISTANCE’

Quantum teleportation is a demonstration of what Albert Einstein famously called “spooky action at a distance” — also known as quantum entanglement. In entanglement — one of the basic of concepts of quantum physics — the properties of one particle affect the properties of another, even when the particles are separated by a large distance. Quantum teleportation involves two distant, entangled particles in which the state of a third particle instantly “teleports” its state to the two entangled particles.

Quantum teleportation is an important means for transmitting information in quantum computing. While a typical computer consists of billions of transistors, called bits, quantum computers encode information in quantum bits, or qubits. A bit has a single binary value, which can be either “0” or “1,” but qubits can be both “0” and “1” at the same time. The ability for individual qubits to simultaneously occupy multiple states underlies the great potential power of quantum computers.

Scientists have recently demonstrated quantum teleportation by using electromagnetic photons to create remotely entangled pairs of qubits.

Qubits made from individual electrons, however, are also promising for transmitting information in semiconductors.

“Individual electrons are promising qubits because they interact very easily with each other, and individual electron qubits in semiconductors are also scalable,” Nichol says. “Reliably creating long-distance interactions between electrons is essential for quantum computing.”

Creating entangled pairs of electron qubits that span long distances, which is required for teleportation, has proved challenging, though: while photons naturally propagate over long distances, electrons usually are confined to one place.

ENTANGLED PAIRS OF ELECTRONS

In order to demonstrate quantum teleportation using electrons, the researchers harnessed a recently developed technique based on the principles of Heisenberg exchange coupling. An individual electron is like a bar magnet with a north pole and a south pole that can point either up or down. The direction of the pole — whether the north pole is pointing up or down, for instance — is known as the electron’s magnetic moment or quantum spin state. If certain kinds of particles have the same magnetic moment, they cannot be in the same place at the same time. That is, two electrons in the same quantum state cannot sit on top of each other. If they did, their states would swap back and forth in time.

The researchers used the technique to distribute entangled pairs of electrons and teleport their spin states.

“We provide evidence for ‘entanglement swapping,’ in which we create entanglement between two electrons even though the particles never interact, and ‘quantum gate teleportation,’ a potentially useful technique for quantum computing using teleportation,” Nichol says. “Our work shows that this can be done even without photons.”

The results pave the way for future research on quantum teleportation involving spin states of all matter, not just photons, and provide more evidence for the surprisingly useful capabilities of individual electrons in qubit semiconductors.

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