THE MOST!
Supernova SN2016aps: Brightest supernova ever imaged is over twice as bright as all other known supernovae.
Supernova Discovered That Outshines All Others – Over Twice as Bright and Energetic
This is an artist’s impression of a supernova. Credit: Aaron Geller (Northwestern University)
A supernova at least twice as bright and energetic, and likely much more massive than any yet recorded has been identified by an international team of astronomers, led by the University of Birmingham.
The team, which included experts from Harvard, Northwestern University and Ohio University, believe the supernova, dubbed SN2016aps, could be an example of an extremely rare ‘pulsational pair-instability’ supernova, possibly formed from two massive stars that merged before the explosion. Their findings are published today (April 13, 2020) in Nature Astronomy.
Such an event so far only exists in theory and has never been confirmed through astronomical observations.
Dr. Matt Nicholl, of the School of Physics and Astronomy and the Institute of Gravitational Wave Astronomy at the University of Birmingham, is lead author of the study. He explains: “We can measure supernovae using two scales – the total energy of the explosion, and the amount of that energy that is emitted as observable light, or radiation.
“In a typical supernova, the radiation is less than 1 percent of the total energy. But in SN2016aps, we found the radiation was five times the explosion energy of a normal-sized supernova. This is the most light we have ever seen emitted by a supernova.”
In order to become this bright, the explosion must have been much more energetic than usual. By examining the light spectrum, the team were able to show that the explosion was powered by a collision between the supernova and a massive shell of gas, shed by the star in the years before it exploded.
“While many supernovae are discovered every night, most are in massive galaxies,” said Dr Peter Blanchard, from Northwestern University and a coauthor on the study. “This one immediately stood out for further observations because it seemed to be in the middle of nowhere. We weren’t able to see the galaxy where this star was born until after the supernova light had faded.”
The team observed the explosion for two years, until it faded to 1 percent of its peak brightness. Using these measurements, they calculated the mass of the supernova was between 50 to 100 times greater than our sun (solar masses). Typically supernovae have masses of between 8 and 15 solar masses.
“Stars with extremely large mass undergo violent pulsations before they die, shaking off a giant gas shell. This can be powered by a process called the pair instability, which has been a topic of speculation for physicists for the last 50 years,” says Dr Nicholl. “If the supernova gets the timing right, it can catch up to this shell and release a huge amount of energy in the collision. We think this is one of the most compelling candidates for this process yet observed, and probably the most massive.”
“SN2016aps also contained another puzzle,” added Dr. Nicholl. “The gas we detected was mostly hydrogen – but such a massive star would usually have lost all of its hydrogen via stellar winds long before it started pulsating. One explanation is that two slightly less massive stars of around, say 60 solar masses, had merged before the explosion. The lower mass stars hold onto their hydrogen for longer, while their combined mass is high enough to trigger the pair instability.”
“Finding this extraordinary supernova couldn’t have come at a better time,” according to Professor Edo Berger, a coauthor from Harvard University. “Now that we know such energetic explosions occur in nature, NASA’s new James Webb Space Telescope will be able to see similar events so far away that we can look back in time to the deaths of the very first stars in the Universe.”
Supernova 2016aps was first detected in data from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), a large-scale astronomical survey program. The team also used data from the Hubble Space Telescope, the Keck and Gemini Observatories, in Hawaii, and the MDM and MMT Observatories in Arizona. Other collaborating institutions included Stockholm University, Copenhagen University, California Institute of Technology, and Space Telescope Science Institute.
Reference: “An extremely energetic supernova from a very massive star in a dense medium” by Matt Nicholl, Peter K. Blanchard, Edo Berger, Ryan Chornock, Raffaella Margutti, Sebastian Gomez, Ragnhild Lunnan, Adam A. Miller, Wen-fai Fong, Giacomo Terreran, Alejandro Vigna-Gómez, Kornpob Bhirombhakdi, Allyson Bieryla, Pete Challis, Russ R. Laher, Frank J. Masci and Kerry Paterson, 13 April 2020, Nature Astronomy.
DOI: 10.1038/s41550-020-1066-7
The research was funded through a Royal Astronomical Society Research Fellowship, along with grants from the National Science Foundation, NASA and the Horizon 2020 European Union Framework.
source: scitechdaily.com
MORE OF THE MOST! Quasar outflow!
Cosmic tempest: Astronomers detect most energetic outflow from a distant quasar
Researchers using the Gemini North telescope on Hawai'i's Maunakea have detected the most energetic wind from any quasar ever measured. This outflow, which is travelling at nearly 13% of the speed of light, carries enough energy to dramatically impact star formation across an entire galaxy. The extragalactic tempest lay hidden in plain sight for 15 years before being unveiled by innovative computer modeling and new data from the international Gemini Observatory.
The most energetic wind from a quasar has been revealed by a team of astronomers using observations from the international Gemini Observatory, a program of NSF's NOIRLab. This powerful outflow is moving into its host galaxy at almost 13% of the speed of light, and stems from a quasar known as SDSS J135246.37+423923.5 which lies roughly 60 billion light-years from Earth.
"While high-velocity winds have previously been observed in quasars, these have been thin and wispy, carrying only a relatively small amount of mass," explains Sarah Gallagher, an astronomer at Western University (Canada) who led the Gemini observations. "The outflow from this quasar, in comparison, sweeps along a tremendous amount of mass at incredible speeds. This wind is crazy powerful, and we don't know how the quasar can launch something so substantial".
As well as measuring the outflow from SDSS J135246.37+423923.5, the team was also able to infer the mass of the supermassive black hole powering the quasar. This monstrous object is 8.6 billion times as massive as the Sun -about 2000 times the mass of the black hole in the center of our Milky Way and 50% more massive than the well-known black hole in the galaxy Messier 87.
This result is published in the Astrophysical Journal and the quasar studied here now holds the record for the most energetic quasar wind measured to date, with a wind more energetic than those recently reported in a study of 13 quasars.
Despite its mass and energetic outflow, the discovery of this powerhouse languished in a quasar survey for 15 years before the combination of Gemini data and the team's innovative computer modeling method allowed it to be studied in detail.
"We were shocked—this isn't a new quasar, but no one knew how amazing it was until the team got the Gemini spectra," explains Karen Leighly, an astronomer at the University of Oklahoma who was one of the scientific leads for this research. "These objects were too hard to study before our team developed our methodology and had the data we needed, and now it looks like they might be the most interesting kind of windy quasars to study."
Quasars—also known as quasi-stellar objects—are a type of extraordinarily luminous astrophysical object residing in the centres of massive galaxies. Consisting of a supermassive black hole surrounded by a glowing disk of gas, quasars can outshine all the stars in their host galaxy and can drive winds powerful enough to influence entire galaxies.
"Some quasar-driven winds have enough energy to sweep the material from a galaxy that is needed to form stars and thus quench star formation," explains Hyunseop (Joseph) Choi, a graduate student at the University of Oklahoma and the first author of the scientific paper on this discovery. "We studied a particularly windy quasar, SDSS J135246.37+423923.5, whose outflow is so thick that it's difficult to detect the signature of the quasar itself at visible wavelengths."
Despite the obstruction, the team was able to get a clear view of the quasar using the Gemini Near-Infrared Spectrograph (GNIRS) on Gemini North to observe at infrared wavelengths. Using a combination of high-quality spectra from Gemini and a pioneering computer modeling approach, the astronomers uncovered the nature of the outflow from the object—which proved, remarkably, to be more energetic than any quasar outflow previously measured.
The team's discovery raises important questions, and also suggests there could be more of these quasars waiting to be found.
We don't know how many more of these extraordinary objects are in our quasar catalogs that we just don't know about yet," concludes Choi "Since automated software generally identifies quasars by strong emission lines or blue color—two properties our object lacks—there could be more of these quasars with tremendously powerful outflows hidden away in our surveys."
"This extraordinary discovery was made possible with the resources provided by the international Gemini Observatory; the discovery opens new windows and opportunities to explore the Universe further in the years to come," said Martin Still, an astronomy program director at the National Science Foundation, which funds Gemini Observatory from the U.S. as part of an international collaboration. "The Gemini Observatory continues to advance our knowledge of the Universe by providing the international science community with forefront access to telescope instrumentation and facilities."
THE MOST CLOSE 'BLACK HOLE', I'll Call This a Gravitational Anchor Point.
Astronomers find closest black hole to Earth
A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1000 light-years from Earth. The black hole is closer to our Solar System than any other found to date and forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.
"We were totally surprised when we realised that this is the first stellar system with a black hole that can be seen with the unaided eye," says Petr Hadrava, Emeritus Scientist at the Academy of Sciences of the Czech Republic in Prague and co-author of the research. Located in the constellation of Telescopium, the system is so close to us that its stars can be viewed from the southern hemisphere on a dark, clear night without binoculars or a telescope. "This system contains the nearest black hole to Earth that we know of," says ESO scientist Thomas Rivinius, who led the study published today in Astronomy & Astrophysics.
The team originally observed the system, called HR 6819, as part of a study of double-star systems. However, as they analysed their observations, they were stunned when they revealed a third, previously undiscovered body in HR 6819: a black hole. The observations with the FEROS spectrograph on the MPG/ESO 2.2-metre telescope at La Silla showed that one of the two visible stars orbits an unseen object every 40 days, while the second star is at a large distance from this inner pair.
Dietrich Baade, Emeritus Astronomer at ESO in Garching and co-author of the study, says: "The observations needed to determine the period of 40 days had to be spread over several months. This was only possible thanks to ESO's pioneering service-observing scheme under which observations are made by ESO staff on behalf of the scientists needing them."
The hidden black hole in HR 6819 is one of the very first stellar-mass black holes found that do not interact violently with their environment and, therefore, appear truly black. But the team could spot its presence and calculate its mass by studying the orbit of the star in the inner pair. "An invisible object with a mass at least 4 times that of the Sun can only be a black hole," concludes Rivinius, who is based in Chile.
Astronomers have spotted only a couple of dozen black holes in our galaxy to date, nearly all of which strongly interact with their environment and make their presence known by releasing powerful X-rays in this interaction. But scientists estimate that, over the Milky Way's lifetime, many more stars collapsed into black holes as they ended their lives. The discovery of a silent, invisible black hole in HR 6819 provides clues about where the many hidden black holes in the Milky Way might be. "There must be hundreds of millions of black holes out there, but we know about only very few. Knowing what to look for should put us in a better position to find them," says Rivinius. Baade adds that finding a black hole in a triple system so close by indicates that we are seeing just "the tip of an exciting iceberg."
Already, astronomers believe their discovery could shine some light on a second system. "We realised that another system, called LB-1, may also be such a triple, though we'd need more observations to say for sure," says Marianne Heida, a postdoctoral fellow at ESO and co-author of the paper. "LB-1 is a bit further away from Earth but still pretty close in astronomical terms, so that means that probably many more of these systems exist. By finding and studying them we can learn a lot about the formation and evolution of those rare stars that begin their lives with more than about 8 times the mass of the Sun and end them in a supernova explosion that leaves behind a black hole."
The discoveries of these triple systems with an inner pair and a distant star could also provide clues about the violent cosmic mergers that release gravitational waves powerful enough to be detected on Earth. Some astronomers believe that the mergers can happen in systems with a similar configuration to HR 6819 or LB-1, but where the inner pair is made up of two black holes or of a black hole and a neutron star. The distant outer object can gravitationally impact the inner pair in such a way that it triggers a merger and the release of gravitational waves. Although HR 6819 and LB-1 have only one black hole and no neutron stars, these systems could help scientists understand how stellar collisions can happen in triple star systems.
This research was presented in the paper "A naked-eye triple system with a nonaccreting black hole in the inner binary", published today in Astronomy & Astrophysics.
source: phys.org
Strongest magnetic field in universe directly detected by X-ray space observatory
The Insight-HXMT team has performed extensive observations of the accreting X-ray pulsar GRO J1008-57 and has discovered a magnetic field of ~1 billion Tesla on the surface of the neutron star. This is the strongest magnetic field conclusively detected in the universe. This work, published in the Astrophysical Journal, was primarily conducted by scientists from the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences and Eberhard Karls University of Tübingen, Germany.
Scientists studied the X-ray pulsar GRO J1008-57 detected by Insight-HXMT during its outburst in August 2017. They discovered for the first time a cyclotron resonant scattering feature (CRSF) at 90 keV at a significance level of > 20σ. (Note that the scientific community confirms a new scientific discovery when its significance level is larger than 5σ.) According to theoretical calculations, the magnetic field that corresponds to this CRSF is up to 1 billion Tesla, which is tens of millions of times stronger than what can be generated in Earth laboratories.
Insight-HXMT is the first Chinese X-ray astronomical satellite. It comprises scientific payloads, including a high-energy telescope, a medium-energy telescope, a low-energy telescope, and a space environment monitor. Compared with other X-ray satellites, Insight-HXMT has outstanding advantages in the detection of cyclotron lines (especially at high energies) due to its broadband (1-250keV) spectral coverage, large effective area at high energies, high time resolution, low dead time and negligible pile-up effects for bright sources.
Neutron stars have the strongest magnetic fields in the universe. Neutron star X-ray binaries are systems consisting of a neutron star and a normal stellar companion. The neutron star accretes matter and forms a surrounding accretion disk. If the magnetic field is strong, the accreted matter is channeled by magnetic lines onto the surface of the neutron star, resulting in X-ray radiations.
As a result, these sources are also called "pulsars." Previous studies have shown that a peculiar absorption feature (known as a "cyclotron resonant scattering feature") can sometimes be found in the spectrum of X-ray pulsars. Scientists believe this is caused by transitions between the discrete Landau levels of electronic motion perpendicular to the magnetic field. Such a scattering feature acts as a direct probe to the magnetic field near the neutron star's surface.
Insight-HXMT was proposed by IHEP in 1993 and was successfully launched in June 2017. IHEP is responsible for scientific payloads, ground segments and scientific research involving this satellite.
source: phys.org
Should this be named The Teslatron?
FAST RADIO BURST ORIGIN/ MAGNETAR Distance Measured via Parallax, Determined to be at 8100 Light Years Distance!
Closing In on Source of Fast Radio Bursts: VLBA Makes First Direct Distance Measurement to Magnetar
Artist’s conception of a magnetar — a superdense neutron star with an extremely strong magnetic field. In this illustration, the magnetar is emitting a burst of radiation. Credit: Sophia Dagnello, NRAO/AUI/NSF
Astronomers using the National Science Foundation’s Very Long Baseline Array (VLBA) have made the first direct geometric measurement of the distance to a magnetar within our Milky Way Galaxy — a measurement that could help determine if magnetars are the sources of the long-mysterious Fast Radio Bursts (FRBs).
Magnetars are a variety of neutron stars — the superdense remains of massive stars that exploded as supernovae — with extremely strong magnetic fields. A typical magnetar magnetic field is a trillion times stronger than the Earth’s magnetic field, making magnetars the most magnetic objects in the Universe. They can emit strong bursts of X-rays and gamma rays, and recently have become a leading candidate for the sources of FRBs.
A magnetar called XTE J1810-197, discovered in 2003, was the first of only six such objects found to emit radio pulses. It did so from 2003 to 2008, then ceased for a decade. In December of 2018, it resumed emitting bright radio pulses.
A team of astronomers used the VLBA to regularly observe XTE J1810-197 from January to November of 2019, then again during March and April of 2020. By viewing the magnetar from opposite sides of the Earth’s orbit around the Sun, they were able to detect a slight shift in its apparent position with respect to background objects much more distant. This effect, called parallax, allows astronomers to use geometry to directly calculate the object’s distance.
By observing an object from opposite sides of the Earth’s orbit around the Sun, as illustrated in this artist’s conception, astronomers were able to detect the slight shift in the object’s apparent position with respect to much more distant background objects. This effect, called parallax, allows scientists then to use geometry to directly calculate the distance to the object — in this case a magnetar within our own Milky Way galaxy. The illustration is not to scale. Credit: Sophia Dagnello, NRAO/AUI/NSF
“This is the first parallax measurement for a magnetar, and shows that it is among the closest magnetars known — at about 8100 light-years — making it a prime target for future study,” said Hao Ding, a graduate student at the Swinburne University of Technology in Australia.
On April 28, a different magnetar, called SGR 1935+2154, emitted a brief radio burst that was the strongest ever recorded from within the Milky Way. While not as strong as FRBs coming from other galaxies, this burst suggested to astronomers that magnetars could generate FRBs.
Fast radio bursts were first discovered in 2007. They are very energetic, and last at most a few milliseconds. Most have come from outside the Milky Way. Their origin remains unknown, but their characteristics have indicated that the extreme environment of a magnetar could generate them.
“Having a precise distance to this magnetar means that we can accurately calculate the strength of the radio pulses coming from it. If it emits something similar to an FRB, we will know how strong that pulse is,” said Adam Deller, also of Swinburne University. “FRBs vary in their strength, so we would like to know if a magnetar pulse comes close or overlaps with the strength of known FRBs,” he added.
“A key to answering this question will be to get more distances to magnetars, so we can expand our sample and obtain more data. The VLBA is the ideal tool for doing this,” said Walter Brisken, of the National Radio Astronomy Observatory.
In addition, “We know that pulsars, such as the one in the famous Crab Nebula, emit ‘giant pulses,’ much stronger than their usual ones. Determining the distances to magnetars will help us understand this phenomenon, and learn if maybe FRBs are the most extreme example of giant pulses,” Ding said.
The ultimate goal is to determine the exact mechanism that produces FRBs, the scientists said.
Ding, Deller, Brisken, and their colleagues reported their results in the Monthly Notices of the Royal Astronomical Society.
Reference: “A magnetar parallax” by H Ding, A T Deller, M E Lower, C Flynn, S Chatterjee, W Brisken, N Hurley-Walker, F Camilo, J Sarkissian and V Gupta, 21 August 2020, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/staa2531
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
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 | NEUTRON STAR, TURNING INTO RARE ULTRA-MAGNETIC OBJECT, REVEALS FAMILY TREE
In a lucky observation, scientists say they have discovered a neutron star in the act of changing into a rare class of extremely magnetic objects called magnetars. No such event has been witnessed definitively until now. This discovery marks only the tenth confirmed magnetar ever found and the first transient magnetar. The transient nature of this object, discovered in July 2003 with NASA's Rossi X-ray Timing Explorer, may ultimately fill in important gaps in neutron star evolution. Dr. Alaa Ibrahim of George Washington University and NASA Goddard Space Flight Center in Greenbelt, Md., presents this result today at the meeting of the American Astronomical Society in Atlanta.
A neutron star is the core remains of a star at least eight times more massive than the Sun that exploded in a supernova event. Neutron stars are highly compact, highly magnetic, fast-spinning objects with about a Sun's worth of mass compressed into a sphere roughly ten miles in diameter. A magnetar is up to a thousand times more magnetic than ordinary neutron stars. At a hundred trillion (10^14) Gauss, they are so magnetic that they could strip a credit card clean at a distance of 100,000 miles. The Earth's magnetic field, in comparison, is about 0.5 Gauss, and a strong refrigerator magnet is about 100 Gauss. Magnetars are brighter in X rays than they are in visible light, and they are the only stars known that shine predominantly by magnetic power. The observation presented today supports the theory that some neutron stars are born with these ultrahigh magnetic fields, but they may be at first too dim to see and measure. In time, however, these magnetic fields act to slow the neutron star's spin. This act of slowing releases energy, making the star brighter. Additional disturbances in the star's magnetic field and crust can make it brighter yet, leading to the measurement of its magnetic field. The newly discovered star, dim as recent as a year ago, is named XTE J1810-197.
"The discovery of this source came courtesy of another magnetar that we were monitoring, named SGR 1806-20," said Ibrahim. He and his colleagues detected XTE J1810-197 with the Rossi Explorer about a degree to the northeast of SGR 1806-20, within the Milky Way galaxy about 15,000 light years away in the constellation Sagittarius. Scientists pinpointed the location of the source with NASA's Chandra X-ray Observatory, which provides more accurate positioning than Rossi. Checking archive data from the Rossi Explorer, Dr. Craig Markwardt of NASA Goddard estimated that XTE J1810-197 became active (that is, 100 times brighter than before) around January 2003. Looking back even further with archived data from ASCA and ROSAT, two decommissioned international satellites, the team could spot XTE J1810-197 as a very dim, isolated neutron star as early as 1990. Thus, the history of XTE J1810-197 emerged.
The inactive state of XTE J1810-197, Ibrahim said, was similar to that of other puzzling objects called Compact Central Objects (CCOs) and Dim Isolated Neutron Stars (DINSs). These objects are thought to be neutron stars created in the hearts of star explosions, and some still reside there, but they are too dim to study in detail. One mark of a neutron star is its magnetic field. But to measure this, scientists need to know the neutron star's spin period and the rate that it is slowing down, called the "spin down". When XTE J1810-197 lit up, the team could measure its spin (1 revolution per 5 seconds, typical of magnetars), its spin down, and thus its magnetic field strength (300 trillion Gauss). In the alphabet soup of neutron stars, there are also Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs). Both of these are now considered to be the same kind of objects, magnetars; and another presentation at today's meeting by Dr. Peter Woods et al. supports this connection. These objects periodically but unpredictably erupt with X-ray and gamma-ray light. CCOs and DINSs appear not to have a similar active state. Although the concept is still speculative, an evolutionary pattern may be emerging, Ibrahim said. The same neutron star, endowed with an ultrahigh magnetic field, may pass through each of these four phases during its lifetime. The proper order, however, remains unclear. "Discussion of such a pattern has surfaced in the scientific community in recent years, and XTE J1810-197's transient nature provides the first tangible evidence in favor of such a kinship," Ibrahim said. "With a few more examples of stars showing a similar trend, a magnetar family tree may emerge." "The observation implies that magnetars could be more common than what is seen but exist in a prolonged dim state," said team member Dr. Jean Swank of NASA Goddard. "Magnetars seem now to be in a perpetual carnival mode; SGRs are turning into AXPs and AXPs can start behaving like SGRs anytime and without warning," said team member Dr. Chryssa Kouveliotou of NASA Marshall, who is receiving the Rossi Award at the AAS meeting for her work on magnetars. "What started with a few odd sources, may soon be proven to encompass a huge number of objects in our Galaxy." Additional supporting data came from the Interplanetary Network and the Russian-Turkish Optical Telescope. Ibrahim's colleagues on this observation also include Dr. William Parke of George Washington University; Drs. Scott Ransom, Mallory Roberts and Vicky Kaspi of McGill University; Dr. Peter Woods of NASA Marshall; Dr. Samar Safi-Harb of the University of Manitoba; Dr. Solen Balman of the Middle East Technical University in Ankara; and Dr. Kevin Hurley of University of California at Berkeley. Drs. Eric Gotthelf and Jules Halpern of Columbia University provided important data from Chandra. | ||||||||||||||||||||
source: https://www.nasa.gov/centers/goddard/news/topstory/2004/0106magnetar.html
Most powerful magnetar in the Milky Way Galaxy It's magnetar PSR J1745-2900! It orbits Sagittarius A* at only 1 light year.
Extremely Powerful Cosmic “Dark Matter Detector” Probed by Astrophysicist
Artist’s depiction of a magnetar. Credit: ESO/L. Calçada
A University of Colorado at Boulder astrophysicist is searching the light coming from a distant, and extremely powerful celestial object, for what may be the most elusive substance in the universe: dark matter.
In two recent studies, Jeremy Darling, a professor in the Department of Astrophysical and Planetary Sciences, has taken a deep look at PSR J1745-2900. This body is a magnetar, or a type of collapsed star that generates an incredibly strong magnetic field.
“It’s the best natural dark matter detector we know about,” said Darling, also of the Center for Astrophysics and Space Astronomy (CASA) at CU Boulder.
He explained that dark matter is a sort of cosmic glue—an as-of-yet unidentified particle that makes up roughly 27% of the mass of the universe and helps to bind together galaxies like our own Milky Way. To date, scientists have mostly led the hunt for this invisible matter using laboratory equipment.
Darling has taken a different approach in his latest research: Drawing on telescope data, he’s peering at PSR J1745-2900 to see if he can detect the faint signals of one candidate for dark matter—a particle called the axion—transforming into light. So far, the scientist’s search has come up empty. But his results could help physicists working in labs around the world to narrow down their own hunts for the axion.
The new studies are also a reminder that researchers can still look to the skies to solve some of the toughest questions in science, Darling said. He published his first round of results this month in The Astrophysical Journal Letters and Physical Review Letters.
“In astrophysics, we find all of these interesting problems like dark matter and dark energy, then we step back and let physicists solve them,” he said. “It’s a shame.”
Natural experiment
Darling wants to change that—in this case, with a little help from PSR J1745-2900.
This magnetar orbits the supermassive black hole at the center of the Milky Way Galaxy from a distance of less than a light-year away. And it’s a force of nature: PSR J1745-2900 generates a magnetic field that is roughly a billion times more powerful than the most powerful magnet on Earth.
An image of the middle of the Milky Way Galaxy showing the location of the supermassive black hole at its center, called Sagittarius A*, and the nearby magnetar PSR J1745-2900. Credit: NASA/CXC/FIT/E
“Magnetars have all of the magnetic field that a star has, but it’s been crunched down into an area about 20 kilometers across,” Darling said.
And it’s where Darling has gone fishing for dark matter.
He explained that scientists have yet to locate a single axion, a theoretical particle first proposed in the 1970s. Physicists, however, predict that these ephemeral bits of matter may have been created in monumental numbers during the early life of the universe—and in large enough quantities to explain the cosmos’ extra mass from dark matter. According to theory, axions are billions or even trillions of times lighter than electrons and would interact only rarely with their surroundings.
That makes them almost impossible to observe, with one big exception: If an axion passes through a strong magnetic field, it can transform into light that researchers could, theoretically, detect.
Scientists, including a team at JILA on the CU Boulder campus, have used lab-generated magnetic fields to try to capture that transition in action. Darling and other scientists had a different idea: Why not try the same search but on a much bigger scale?
“Magnetars are the most magnetic objects we know of in the universe,” he said. “There’s no way we could get close to that strength in the lab.”
Narrowing in
To make use of that natural magnetic field, Darling drew on observations of PSR J1745-2900 taken by the Karl G. Jansky Very Large Array, an observatory in New Mexico. If the magnetar was, indeed, transforming axions into light, that metamorphosis might show up in the radiation emerging from the collapsed star.
The effort is a bit like looking for a single needle in a really, really big haystack. Darling said that while theorists have put limits on how heavy axions might be, these particles could still have a wide range of possible masses. Each of those masses, in turn, would produce light with a specific wavelength, almost like a fingerprint left behind by dark matter.
Several of the 28 dish antennae that make up the Very Large Array, located in Socorro, New Mexico, USA. Credit: CGP Grey, CC BY 2.0
Darling hasn’t yet spotted any of those distinct wavelengths in the light coming from the magnetar. But he has been able to use the observations to probe the possible existence of axions across the widest range of masses yet—not bad for his first attempt. He added that such surveys can complement the work happening in Earth-based experiments.
Konrad Lehnert agreed. He’s part of an experiment led by Yale University—called, not surprisingly, HAYSTAC—that is seeking out axions using magnetic fields created in labs across the country.
Lehnert explained that astrophysical studies like Darling’s could act as a sort of scout in the hunt for axions—identifying interesting signals in the light of magnetars, which laboratory researchers could then dig into with much greater precision.
“These well-controlled experiments would be able to sort out which of the astrophysical signals might have a dark matter origin,” said Lehnert, a fellow at JILA, a joint research institute between CU Boulder and the National Institute of Standards and Technology (NIST).
Darling plans to continue his own search, which means looking even closer at the magnetar at the center of our galaxy: “We need to fill in those gaps and go even deeper.”
References:
“New Limits on Axionic Dark Matter from the Magnetar PSR J1745-2900” by Jeremy Darling, 7 September 2020, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/abb23f
“Search for Axionic Dark Matter Using the Magnetar PSR J1745-2900” by Jeremy Darling, 17 September 2020, Physical Review Letters.
DOI: 10.1103/PhysRevLett.125.121103
source: scitechdaily.com
THE MOST METAL POOR GLOBULAR CLUSTER! It challenges galaxy formation 'theories'.
RBC EXT8
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RBC EXT8 is a globular cluster in the galaxy Messier 31, 27 kpc from the galaxy center. The spectral lines reveal levels of iron 800 times lower than our sun. Its position is right ascension 00h53m14s.53, declination +41°33′24′′. (J2000 equinox) according to the Revised Bologna Catalogue (10).[1] It's magnitude is 15.79, and 15.5" across.[2]
References[edit]
- ^ An extremely metal-deficient globular cluster in the Andromeda Galaxy 14 Oct 2020, Søren S. Larsen, Aaron J. Romanowsky, Jean P. Brodie, Asher Wasserman,
- ^ The outer halo globular cluster system of M31 - I. The final PAndAS catalogue Monthly Notices of the Royal Astronomical Society · April 2014
sourced from: https://www.sciencenews.org/article/globular-star-cluster-surprising-few-heavy-elements
