Tag Archives: pulsar

Einstein’s Theory of General Relativity aces its toughest test yet in 16-year-old study of unique pulsar system

Artist impression of PSR J0737-3039 A/B. Credit: Michael Kramer/MPIfR.

Since Albert Einstein first proposed his landmark theory of general relativity in 1916, it has stood every test scientists have thrown at it, no matter how rigorous — and there were numerous such attempts to find holes in the theory that posits gravity is actually a distortion of the fabric of space-time caused by massive objects. For instance, general relativity has perfectly described observations of stars closely passing the supermassive black hole in the Milky Way’s galactic center or the existence of gravitational waves, whose discovery was awarded the Nobel Prize in Physics in 2017.

Now, scientists have announced general relativity passed with flying colors one of its toughest tests yet, an ambitious observation of a double-pulsar system made by seven different radio telescopes across the world spanning 16 years. According to the researchers led by Michael Kramer from the Max Planck Institute for Radio Astronomy in Germany, the observed effects agreed with general relativity with an accuracy of at least 99.99%.

Pulsars are highly magnetized, fast-spinning neutron stars that emit flashes of electromagnetic radiation out of the poles in opposite directions. These objects are extremely compact, fitting a mass greater than that of the Sun into a sphere the size of a large city. Although the light emitted by these cosmic objects is steady, the beams of light are not aligned with the pulsar’s axis of rotation, so, from Earth’s perspective, pulsars appear to flicker because they also spin very fast. They’re often compared to a lighthouse, for this reason.

Neutron stars are ideal cosmic laboratories for testing general relativity due to their huge gravitational influence. Only black holes are denser and thus more prone to exhibiting extreme effects of general relativity, but pulsars are much easier to observe thanks to their flickering lights and radio signals.

For their new study, the international team of astronomers targeted a unique pair of pulsars (the only pulsar binary system known thus far), known as PSR J0737-3039 A/B, located some 2,4000 light-years away in the constellation Puppis.

One of the two pulsars rotates 44 times a second while the other is much slower, completing a revolution around its own axis every 2.8 seconds. They each are about 30% more massive than the Sun, but measure only about 24 km in diameter. Together, they complete an orbit around a common center of mass in just 147 minutes. This is one very busy system, which produces unusual high gravitational pull and intense magnetic fields — the ultimate testing ground for Einstein’s cornerstone theory, allowing scientists to carry out experiments with a precision 25 times better than single pulsar systems and 1,000 times better than currently possible using gravitational wave detectors.

From 2003 to 2019, seven radio telescopes kept an eye on the double pulsar system, covering the most important bands in the radio spectrum ranging from 334 MHz to 2520 Mhz.

The fast orbital motion of the rotating neutron stars allowed the researchers to test General Relativity on seven different predictors, including gravitational waves, light propagation (light is delayed and bent by gravity), time dilation, mass-energy equivalence (the famous E=mc2), and the effects of electromagnetic radiation on the pulsars’ orbital motion. All seven of these predictors unfolded as observed in the cosmic experiment.

“We needed to find ways of testing Einstein’s theory at an intermediate scale to see if it still holds true. Fortunately, just the right cosmic laboratory, known as the ‘double pulsar,’ was found using the Parkes telescope in 2003. Our observations of the double pulsar over the past 16 years proved to be amazingly consistent with Einstein’s general theory of relativity, within 99.99 percent to be precise,” said Dr. Dick Manchester, a fellow at CSIRO.

Einstein hasn’t been proven wrong yet again — and that may actually be a problem. General relativity is not compatible with other fundamental forces that are described by quantum mechanics. Physicists believe that general relativity must break down at some point in order to account for these discrepancies. Finding a deviation from general relativity would thus open the door to new physics that might eventually unify all the fundamental forces of nature under a single theory.

“We’ll be back in the future using new radio telescopes and new data analysis hoping to spot a weakness in general relativity that will lead us to an even better gravitational theory,” said Adam Deller, Associate Professor from Swinburne University and the ARC Center of Excellence for Gravitational Waves (OzGrav).

The findings appeared in the journal Physical Review X.

Astronomers map the surface of a pulsar for the first time

Pulsars are spinning neutron stars — tiny, compacted remnants of once-massive stars. Pulsars spin rapidly, beaming radiation into space like a lighthouse. For this reason, they act as beacons, making them indispensable tools in astronomers’ arsenal when surveying the galaxy. But a series of new studies, which mapped the surface of a pulsar for the very first time, shows that we still have much to learn about these mysterious objects.

Astronomers didn’t expect to find three hotspots on a pulsar’s southern hemisphere. Credit: NASA.

The groundbreaking studies were performed by two groups, one led by researchers at the University of Amsterdam, and the other led by astronomers at the University of Maryland. Although their roles differed, both teams examined X-ray light from the pulsar J0030+0451, which lies about 1,100-light-years away in the constellation Pisces.

J0030’s X-rays were detected and analyzed by the aptly named Neutron star Interior Composition Explorer (NICER) instrument, aboard the International Space Station where there isn’t an atmosphere to cloud measurements.

“From its perch on the space station, NICER is revolutionizing our understanding of pulsars,” said Paul Hertz, astrophysics division director at NASA Headquarters in Washington. “Pulsars were discovered more than 50 years ago as beacons of stars that have collapsed into dense cores, behaving unlike anything we see on Earth. With NICER we can probe the nature of these dense remnants in ways that seemed impossible until now.”

Inside neutron stars, intense gravitational forces crush protons and electrons together, turning them into neutrons. Such stars pack more mass than the sun into a sphere no larger than Manhattan, making them some of the densest objects in the universe. The new study determined that the pulsar has a mass between 1.3 and 1.4 times that of the sun, crammed into a sphere roughly 16 miles (26 km) in diameter.

The disproportionate mass-size ratio wasn’t surprising. What was really unexpected was the location of J0030’s hotspots.

Pulsars spin between 7 and 40,000 times a minute and form intense magnetic fields. The rapid spin and magnetic fields generate powerful beams of electromagnetic radiation, and as the pulsar rotates, these beams sweep the sky like a lighthouse. Scientists have always thought that these beams are fired from two hotspots, one for each magnetic pole.

But, at least in J0030’s case, there are two or three of these hotspots, all located in the southern hemisphere. There was none in the northern hemisphere, as textbooks suggest.

In order to map the pulsar’s hotspots, the researchers had to compute where the X-rays received by NICER originated on the neutron star’s surface — and this required computations that would have taken a normal computer about a decade to complete. Luckily, this turned out fine in just a month using the Dutch national supercomputer Cartesius.

There are at least two features that make this investigation unique. First of all, it’s the first time that astronomers have been able to detect photons from a pulsar this fast — NICER measures radiation on a photon-by-photon basis with an unparalleled precision of 100 nanoseconds — which enabled the computer model to account for the rotation of the pulsar. Secondly, the model also considered the fact that the X-ray radiation can also come from the side of the pulsar, thanks to the curvature of space-time.

These results indicate that a pulsar’s magnetic field is much more complex than previously assumed — or at least not as simple as the traditional two-pole model. Now, scientists will have to repeat the accomplishment with other pulsars. Such investigations may help answer many burning questions. For example, astronomers would like to know what exactly mater looks like in the ultra-dense core of a neutron star.

“It’s remarkable, and also very reassuring, that the two teams achieved such similar sizes, masses and hot spot patterns for J0030 using different modeling approaches,” said Zaven Arzoumanian, NICER science lead at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It tells us NICER is on the right path to help us answer an enduring question in astrophysics: What form does matter take in the ultra-dense cores of neutron stars?”

The findings appeared in The Astrophysical Journal Letters.

Peculiar pulsar slows down before ‘glitching’

Artist impression of a pulsar. Credit: University of British Columbia.

Pulsars are rotating neutron stars that emit a focused beam of electromagnetic radiation, resulting in their nickname as “lighthouses” of the universe. Pulsars come in all shapes and sizes, and some behave quite weirdly and seemingly chaotic — but that doesn’t mean there isn’t a pattern.

Vela, a neutron star located nearly 1,000 light-years away from Earth in the southern sky, is famous among astronomers because it “glitches” once every three years, suddenly speeding up its rotational period before slowing down back to normal.

Scientists aren’t sure why this weird star is behaving this way but new observations suggest that Vela seems to slow down its rotation rate immediately before the glitch. This was the first time astronomers have ever seen anything like this.

Neutron stars are the remnants of huge dead stars and represent some of the densest objects in the universe. Imagine an object with the mass of a sun squashed down to the size of a city — that’s how dense these objects can get.

Most neutron stars are observed as pulsars, which rotate at very regular intervals ranging from milliseconds to seconds. 

For their new study, astronomers at the Monash University School of Physics and Astronomy reanalyzed observations of the Vela glitch made in December 2016.

This more thorough analysis revealed that Vela — which normally makes 11 rotations per second — started rotating even faster and then slowed down to a more normal speed very quickly.

Artist impression of the three components in the neutron star. Credit: Carl Knox

Although astronomers aren’t sure why this happens, the observation is consistent with theoretical models that suggest that neutron stars have three internal components.

“One of these components, a soup of superfluid neutrons in the inner layer of the crust, moves outwards first and hits the rigid outer crust of the star causing it to spin up,” said Dr. Paul Lasky, an astronomer at the Monash School of Physics and Astronomy and co-author of the new study published in the journal Nature Astronomy.

“But then, a second soup of superfluid that moves in the core catches up to the first causing the spin of the star to slow back down.”

Ultimately, what this new study shows is that a pulsar glitch isn’t a straightforward, single-step process. Instead, a complex interplay of internal forces seems to generate sophisticated behaviors in the neutron stars, although the exact mechanisms are still a mystery. In the future, new observations and theoretical models may reveal more.

Dame Susan Jocelyn Bell Burnell in 1967, the year she found the first evidence of a pulsar. Credit: Wikimedia Commons.

She lost the Nobel Prize to her supervisor in 1974 — now, she got a $3 million physics prize, and donated all of it

Dame Susan Jocelyn Bell Burnell in 1967, the year she found the first evidence of a pulsar. Credit: Wikimedia Commons.

Dame Susan Jocelyn Bell Burnell in 1967, the year she found the first evidence of a pulsar. Credit: Wikimedia Commons.

While she was still a graduate student at the University of Cambridge studying strange far-away objects in distant galaxies, Jocelyn Bell Burnell came across something peculiar. A squiggle periodically appeared on the 96-feet-long chart paper etched in red ink, indicating the presence of mysterious, pulsating radio waves.

She extracted more data but the blip in the charts disappeared — only to oddly return a month later.

When Burnell showed the data to her supervisor, Antony Hewish,  the professor dismissed the readings as some artificial radio interference. For the young student, this came as a strong hit. She who was having a row with imposter syndrome — the belief that you’re an inadequate and incompetent failure, despite evidence that indicates you’re skilled and quite successful — and wanted to prove herself. So nevertheless, she continued to pore through the data.

Burnell was convinced the anomaly was not indicative of interference because the radio waves were generated by something moving at the same speed as the stars. The source had to be in space somewhere. She was right.

Today, we now know that these sort of sources are, in fact, dense, rapidly spinning neutron stars that emit radiations. These objects are called pulsars and are considered one of the greatest astronomical achievements of the 20th century. Pulsars have helped scientists detect exoplanets, design better spacecraft navigation, or test Einstein’s theory of general relativity.

The discovery was so important that it was awarded the 1974 Nobel Prize. But it wasn’t Burnell who received it — the distinction went to Hewish, the professor who dismissed her finding.

“[I]n those days students weren’t recognized by the committee,” Burnell said in 2009, apparently not very fazed by the lack of recognition for her hard work.

It was 1967 when Burnell first noticed the blips in her radio telescope charts. Now, more than fifty years later, her work has been awarded an important recognition: the Special Breakthrough Prize in Fundamental Physics — and a check for $3 million.

The awards were founded in 2013 by science and technology gurus including Mark Zuckerberg, Anne Wojcicki (co-founder and CEO of personal genomics company 23andMe), and Jack Ma, founder of the Alibaba Group. They’re the largest science prizes in the world, financially speaking, dwarfing the Nobels by a large margin.

“Professor Bell Burnell thoroughly deserves this recognition. Her curiosity, diligent observations and rigorous analysis revealed some of the most interesting and mysterious objects in the Universe,” said Yuri Milner, one of the founders of the Breakthrough Prizes, in a statement.

Laudably, Burnell chose to donate her prize money to the UK Institute of Physics, which will be used to fund grants for physics students from under-represented groups.

“I don’t want or need the money myself and it seemed to me that this was perhaps the best use I could put to it,” she told the BBC.

“Jocelyn Bell-Burnell’s work on the discovery of Pulsars really did contribute to a major breakthrough in our understanding of the universe.  Her generous decision to donate the prize money to bringing more women, under-represented ethnic minorities and refugees into the world of physics, can hopefully help to increase the flow of breakthrough moments in the future,” Richard Catlow, Vice-President of the Royal Society, said in a statement.

And in the same good spirit, the accomplished physicist really never held a grudge for getting snubbed the Nobel. In fact, she saw any good things out of it.

“I feel I’ve done very well out of not getting a Nobel prize,” she told The Guardian. “If you get a Nobel prize you have this fantastic week and then nobody gives you anything else. If you don’t get a Nobel prize you get everything that moves. Almost every year there’s been some sort of party because I’ve got another award. That’s much more fun.”

pulsar-cosmos

Astronomers are on the lookout for low-frequency gravitational waves generated by merging supermassive black holes

pulsar-cosmos

Credit: NASA.

In just a year, scientists have confirmed not one but five gravitational waves. But don’t worry, if you thought gravitational waves — essentially ripples in the fabric of space-time — are now dull and mundane, scientists found new ways to keep them interesting. New research showed that it’s theoretically possible to pick up the low-frequency gravitational waves generated by events such as the merger of two supermassive black holes. The discovery could be ten years away.

Intergalactic waves

Gravitational waves have made a lot of headlines lately so what’s with all the hype?

The existence of gravitational waves, which were first predicted by Einstein’s Theory of General Relativity about a hundred years ago, was only confirmed only last year. The event was recorded by the Laser Interferometer Gravitational-Wave Observatory (LIGO), whose founders were awarded this year’s Nobel Prize in Physics. 

Gravity waves are essentially ripples in the fabric of spacetime that are generated by interactions between very massive accelerating cosmic objects, such as neutron stars or black holes. Physicists liken gravity waves to the waves generated when a stone is thrown into a pond.

Gravity waves are basically ripples/distortions in the medium that we live in, space-time itself. Credit: ESO/NASA.

Gravity waves are basically ripples/distortions in the medium that we live in, space-time itself. Credit: ESO/NASA.

LIGO was founded in 1992, so it took them 25 years to prove their existence. That’s because detecting a gravity wave is no easy feat. To spot gravitational waves directly for the first time, scientists had to measure a distance change 1,000 times smaller than the width of a proton using interferometers, basically mirrors placed 4 kilometers apart.

In the case of the September 14, 2015, observation which was announced on February 11, 2016, scientists observed gravitational waves produced by the collision of black holes with a mass about a dozen times that of the Sun. Since then, gravitational waves have been spotted another four times. The most recent observation of a gravitational wave was generated by the merger of two neutron stars, which are the collapsed cores of large stars — they’re the smallest and, at the same time, densest stars we know of. The event was detected both by LIGO and by traditional telescopes which picked up light from the gamma-ray bursting out of the neutron star merger.

‘Hearing bass singers, not just sopranos’

Astronomers, however, would like to also detect far stronger gravitational waves, such as those produced by the merger of supermassive black holes — behemoth black holes whose mass can be millions if not billions of times greater than that of the Sun. The problem is that neither LIGO nor VIRGO can register low-frequency signals such as those generated by extremely massive events.

Thankfully, scientists have already thought of a solution. According to a new paper published in the journal Nature Astronomy, it’s quite possible to detect gravitational waves from merging supermassive black holes by studying the subtle anomalies in pulsars.

A pulsar is a rapidly rotating neutron star which emits electromagnetic signals. These objects are also very dense, holding the mass of the sun in about the size of a large city. Pulsars radiate two steady, narrow beams of light in opposite directions. Although the light from the beam is steady, pulsars appear to flicker because they also spin. For this reason, pulsars have earned the nickname ‘cosmic lighthouses’.

With enough data, by studying the periodicity and strength of the pulsar signals, scientists can infer the presence and strength of a gravitational wave if the pulsar signal is delayed even by a tiny amount.

“A difference between when the pulsar signals should arrive, and when they do arrive, can signal a gravitational wave,” says Chiara Mingarelli, lead author of the new study and a research fellow at the Center for Computational Astrophysics at the Flatiron Institute in New York City. “And since the pulsars we study are about 3,000 light-years away, they act as a galactic-scale gravitational-wave detector.”

In order to predict where and when supermassive black hole mergers might occur, researchers employed data from the 2 Micron All-Sky Survey (2MASS), which they combined with galaxy merger rates recorded by the Illustris simulation project. 

Out of the 5,000 galaxies that they studied, the scientists narrowed the list down to 90 pairs of supermassive black holes, the most massive of which are expected to merge within the next four million years. Mingarelli and colleagues are confident that by expanding the “pulsar timing array over the next 10 years or so, there is a high likelihood of detecting gravitational waves from at least one supermassive black hole binary.”

Ultimately, detecting a gravitational wave generated by merging supermassive black holes could teach us more about how galaxies form and merge, helping us unravel the secrets of the universe.

Astronomers discover the first white dwarf pulsar in history, ending half a century of searching

Scientists at the University of Warwick have discovered the first white dwarf pulsar we’ve ever seen. The super-dense body is housed in an exotic binary star system 380 light-years away from Earth.

Image credits Mark Garlick / University of Warwick.

Professors Tom Marsh and Boris Gänsicke of the University’s Astrophysics Group together with Dr David Buckley from the South African Astronomical Observatory, have made astronomical history — they have identified the first white dwarf pulsar humanity has ever seen, in the neighboring system of AR Scorpii (AR Sco). Astronomers have been on the lookout for this class of pulsar for over half a century now.

Small but lively

AR Sco is only 380 light-years away from Earth, in the Scorpius constellation. It has two stars — a very rapidly spinning former star known as a white dwarf pulsar, and an actual star known as a red dwarf — locked together in a 3.6-hour orbit.

The red dwarf isn’t very noticeable in and of itself. It weighs one-third of a Solar mass (the biggest ones reach one-half of a solar mass). It ‘burns’ hydrogen just like our Sun but at a much slower rate. So it’s not particularly hot or very bright at all. Standard red dwarf across the board.

However, its choice of companions creates some spectacular interaction which brought the scientists’ attention to the system in the first place. Its neighboring pulsar isn’t much bigger than Earth, but it’s an estimated 200,000 times denser. Like other pulsars, it’s a very lively celestial body.

What sets it apart is the way it formed. Neutron stars/pulsars are the naked cores of huge stars squashed by supernovae into pure matter — they’re one huge atomic nuclei, without any empty space for electron orbits or personal space or whatnot. It’s the closest a star can get to a black hole without turning to the dark side. The white dwarf pulsar is smaller, less dense, and formed after the outer layers of a Sun-like star breezed away into a planetary nebula.

“White dwarfs and pulsars represent distinct classes of compact objects that are born in the wake of stellar death,” NASA explains.

“A white dwarf forms when a star similar in mass to our sun runs out of nuclear fuel. As the outer layers puff off into space, the core gravitationally contracts into a sphere about the size of Earth, but with roughly the mass of our sun. […] neutron stars are even denser, cramming roughly 1.3 solar masses into a city-sized sphere.”

“Pulsars give off radio and X-ray pulsations in lighthouse-like beams.”

A white dwarf pulsar, like AR Sco, doesn’t cool off into a black dwarf but retains enough energy to accelerate subatomic particles as a pulsar.

“Similar to neutron-star pulsars, the pulsed luminosity of AR Sco is powered by the spin-down of the rapidly rotating white dwarf that is highly magnetized,” the paper reads.

It has an electromagnetic field 100 million times more powerful than our planet’s and makes a full rotation in just under two minutes. Because of this gargantuan magnetic field, AR Sco acts kind of like a natural particle accelerator. We’re talking about monumental levels of energy here. Matter inside it is squashed down to extreme conditions and emits huge levels of radiation and charged particles as focused ‘beams’. These occasionally whip at its neighbor, causing the entire system to spectacularly brighten and fade every two minutes.

Whipped bright

“The new data show that AR Sco’s light is highly polarised, showing that the magnetic field controls the emission of the entire system, and a dead ringer for similar behaviour seen from the more traditional neutron star pulsars,” Prof Marsh says.

The beams radiate outwards from the pulsar’s magnetic poles. Think of it like a huge lighthouse in space spinning really fast. Each time the beam hits the atmosphere of the red dwarf, it speeds up electrons there to almost the speed of light. This interaction is what causes the red dwarf’s brightness to flicker. It suggests that the star’s inner workings are dominated by its neighbor’s kinetic energy — an effect which has never been observed before, not even in similar types of binary stars.

Graphical simulation of a pulsar. Credit: Giphy.

Graphical simulation of a pulsar. Credit: Giphy.

“AR Sco is like a gigantic dynamo: a magnet, size of the Earth, with a field that is ~10.000 stronger than any field we can produce in a laboratory, and it is rotating every two minutes. This generates an enormous electric current in the companion star, which then produces the variations in the light we detect,” Professor Boris Gänsicke added.

The distance between the two stars is around 1.4 million kilometers — which is three times the distance between the Moon and the Earth.

The full paper ‘Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii’, has been published in the journal Nature Astronomy.

Artist illustration of Pulsar in J140135. Credit: NASA

How to weigh a star: a new mathematical method

A novel mathematical model can weigh the mass of a pulsar – a rapidly rotating magnetized neutran star – using principles of nuclear physics, rather than gravity. Up until now, the mass of a star could only be determined in relation with other bodies, based on the gravitational pull these exerted. Now, using the new model scientists will be able to study pulsars in isolation, allowing for more precise measurements than ever before.

Artist illustration of Pulsar in J140135. Credit: NASA

Artist illustration of Pulsar in J140135. Credit: NASA

When very massive stars die, typically in a supernova explosion, what’s leftover is a rotating neutron star that emits a  focused beam of electromagnetic radiation, only visible if you’re standing in its path like a lighthouse. These rotating neutron stars are called “pulsars” in short because these emissions seem to be pulsing into outer space.

When a pulsar first forms, it has the most energy and fastest rotational speed. As it releases electromagnetic power through its beams, it gradually slows down. Within 10 to 100 million years, it slows to the point that its beams shut off and the pulsar becomes quiet. But although older pulsars rotate stably, the younger ones go through periods of slowing or speeding called ‘glitches’. Scientists think these glitches are caused by the motion of the superfluids found inside the neutron stars. This motion transfers energy, causing them to pick up rotation or slow down.

“Imagine the pulsar as a bowl of soup, with the bowl spinning at one speed and the soup spinning faster. Friction between the inside of the bowl and its contents, the soup, will cause the bowl to speed up. The more soup there is, the faster the bowl will be made to rotate,” says , Nils Andersson a Professor of Applied Mathematics at University of Southampton.

The Southampton team fed radio and X-ray data into their model to eventually determine the mass of pulsars that glitch. This could prove extremely useful for future, next generation observatories like the  Square Kilometre Array (SKA) and the Low Frequency Array (LOFAR). “Our results provide an exciting new link between the study of distant astronomical objects and laboratory work in both high-energy and low-temperature physics. It is a great example of interdisciplinary science,” says Professor Andersson.

blitzar

Scientists Observe Giant Burst of Radio Waves

Scientists have observed a massive burst of radio waves, helping them narrow down the potential sources of these huge bursts of energy. These events, also called blitzars, last about a millisecond but give off as much energy as the sun does in a million years.

blitzar

Image via The Register.

These are quite possibly the most interesting and shocking sources of energy in the Universe. It’s not clear how they form, and the best theory is that blitzars start when a spinning neutron star with a big mass starts to collapse. The necessary condition is that the star is spinning very fast. Over a few million years, the pulsar’s strong magnetic field radiates energy away and slows its spin. Eventually the weakening centrifugal force is no longer able to stop the pulsar from its transformation into a black hole. At this moment of blitzar formation, part of the pulsar’s magnetic field outside the black hole is suddenly cut off from its vanished source – and this is where the burst starts.

A total of nine blitzars have been reported since the first was discovered in 2007, but none of them were captured “live” – all of them were found by looking through older data. Now, astronomers have finally surprised such an event in the act using the Parkes Telescope.

“This is a major breakthrough,” says Duncan Lorimer of West Virginia University in Morgantown, who was part of the team that discovered the first fast radio burst.

Within only a few hours, other telescopes also tuned in to see the blitzar, but none of them observed any afterglow – which is a neat finding in itself, Emily Petroff of Swinburne University in Melbourne, Australia said. This observation also revealed a new, interesting property – the waves appear to be circularly polarised rather than linearly polarised. This means that they don’t vibrate in a single plane, but in two.

“It’s something nobody has ever measured before,” Petroff says. But it’s hard to know how to interpret it, she says.

So far, while this is very exciting data, scientists are still not clear what conclusions to draw. Keith Bannister from Australia’s national science agency in Sydney said:

“Nobody knows what to make of it,” he says. “All the ideas are very exotic so ruling them out is all you can do at the moment.”

Journal reference: Monthly Notices of the Royal Astronomical Society, accepted, arxiv.org/abs/1412.0342

 

Pulsars with black holes could hold the ‘holy grail’ of gravity

Pulsars and black holes, two of the most enigmatic celestial bodies in the Universe may actually hold the key to understanding how Einstein’s theory of relativity and gravity interact.

Artistic depiction of a pulsar and the emitted radiation. Image via National Radio Astronomy Observatory.

A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. Pulsars are from when a star that turns becomes a supernova and then collapses into a neutron star; the neutron star maintains its angular momentum, but because it has lost most of its mass, it starts to spin incredibly fast –  usually between a 2 and 50 times per second! The longest known spin period is just over 8 seconds. Due to this spin, pulsars are also excellent time keepers, as they emit intermittent light at regular intervals. Now, researchers believe that pulsars could be used to put Einstein’s theory of relativity to the test, especially if a pulsar would be found in the vicinity of a black hole. The only problem is that so far, this scenario has never been encountered.

“Pulsars act as very precise timekeepers, such that any deviation in their pulses can be detected,” Diego F. Torres, ICREA researcher from the Institute of Space Sciences (IEEC-CSIC), explains. “If we compare the actual measurements with the corrections to the model that we have to use in order for the predictions to be correct, we can set limits or directly detect the deviation from the base theory.”

Deviations mentioned by Torres occur when there is an object with significant mass close to the pulsar; in the lack of a black hole, that’s usually a white dwarf or another neutron star. By analyzing the interactions between pulsar-white dwarf or pulsar-neutron star interactions, astrophysicists can put not only the theory of gravity, but also Einstein’s relativity to the test. In the theory of relativity, the gravitational movement of a body results from the accelerating force exerted by the gravitational fields and nothing else. It is relatively constant in direction and magnitude. In other words, if you set up a free-fall experiment in a laboratory, the results will be independent on where the laboratory is in space and time and will depend only on the gravitational force(s).

This has been confirmed by previous observations, but in a new study, Torres and his colleague Manjari Bagchi argue that if you really want to put this idea to the test, you need to find a pulsar-black hole system; all that’s left now… is to actually find one.

The combined computing power of 200,000 private PCs helps astronomers take an inventory of the Milky Way

It’s a good day for crowdsourcing – the Einstein@Home project, which connects home and office PCs of volunteers from around the world to a global supercomputer announced that through the participation of volunteers alone, astronomers were able to discover 24 new pulsars.

That’s right, you can do top notch science, from your very own home… without actually doing anything. Einstein@Home is a World Year of Physics 2005 and an International Year of Astronomy 2009 project supported by the American Physical Society (APS) and by a number of international organizations. Basically, through it, you can use your computer’s idle time to search for weak astrophysical signals from spinning neutron stars (also called pulsars).

Searching for pulsars is a bit like looking for a needle in a haystack: you have to search for characteristics like how fast it is spinning, how far it is away, and other parameters. The best way to do this, is to try many different combinations of all these characteristics and just try for each one, whether it looks like there’s a pulsar in the data. But there’s no clear limit and no way of knowing in advance what the parameters will be, so this is a really computer-intensive task – which is why astrophysicists need our help.

“We could only conduct our search thanks to the enormous computing power provided by the Einstein@Home volunteers,” says Benjamin Knispel, researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Hannover, and lead author of the study now published in The Astrophysical Journal. “Through the participation of the public, we discovered 24 new pulsars in our Milky Way, which had previously been missed – and some of them are particularly interesting.”

Understanding and studying pulsars is very important for a series of astrophysical clues they hold – they’re also an excellent testing area for Einstein’s theory of relativity.

Each week, 50,000 volunteers from around the world “donate” idle compute cycles on their 200,000 home and office PCs to Einstein@Home – together, they make a difference. You can too, so if your computer is turned on all the time, and you’re not really worried about an additional $5/month you’ll pay for electricity, why not?

You can sign up here, and you can sign off anytime you want to.

We now know the birth place of the biggest guitar in the galaxy

guitarIn case you’re wondering, the biggest ‘guitar’ in our galaxy is in fact a pulsar that was nicknamed The Guitar Pulsar. It’s basically a stellar corpse that emits a beam of electromagnetic radiation that just shreds interstellar gas, creating a wake of hot hydrogen shaped just like a guitar.

Little is known about these remnants, from any point of view. In order to track down it’s birthplace, Nina Tetzlaff at the University of Jena in Germany and her colleagues calculated the location of 140 groups of stars, as they were 5 millions ago.

The pulsar was practically launched from a cluster of massive stars, moving at about 1500 kilometres per second, which is just huge. They were able to pinpoint the exact location it was formed, but why it moved so fast still remains a mystery. Speeds over 1000 km/s are practically not used in current astronomy models, and are considered by many to be borderline impossible.

Nasa discovers a dozen pulsars that change understanding about dying stars

Recently, NASA’s Fermi Gamma-ray Space Telescope discovered no more, no less than 12 pulsars, and it also detected gamma ray pulse from 18 others. These findings are forcing scientists to rethink what we know about dying stars, as they totally underestimated the power of these stellar cilinders.

“We know of 1,800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them,” says Roger Romani of Stanford University, Calif. “Now, for dozens of pulsars, we’re seeing the actual power of these machines.”

Pulsars are rotating neutron stars, highly magnetized, that emit a beam of electromagnetic radiation with a period of the pulse variating from 8.5 seconds to just 1.5 miliseconds. They are what remains when a massive star explodes. They’re also incredible cosmic dynamos and despite the fact that scientists don’t fully understand this process, they can say for sure that very intense electric and magnetic fields spin and accelerate particles to speeds very close to that of light.

Most pulsars were found because they emitted pulses at radio wavelength which are emitted from the pulsar’s poles. If these poles and the star’s spin axis are not alligned exactly, then the beams would be swept across the sky, meaning that we can detect them only if such a beam meats a radio telescope. But data is often inaccurate or biased because these telescopes are situated on Earth

“That has colored our understanding of neutron stars for 40 years,” Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar’s total power. Its gamma rays, on the other hand, account for 10 percent or more. “For the first time, Fermi is giving us an independent look at what heavy stars do. “

“We used to think the gamma rays emerged near the neutron star’s surface from the polar cap, where the radio beams form,” addsAlice Harding of NASA’s Goddard Space Flight Center in Greenbelt, Md. “The new gamma-ray-only pulsars put that idea to rest.”

Now, scientists have their hands full with this new class of gamma-ray pulsars, which they believe arise far above the neutron star. Due to the fact that rotation powers their emissions they tend to slow down a bit as they “age”; however, Fermi picked up emissions from gamma rays from seven millisecond pulsars (which are called this way because they spin somewhere between 100 and 1000 times a second!!!). They tend to sometimes “break the rules”, and “cohabitate” with a normal star, residing in binary systems.

Here are some animations to give you a better and more visual understanding of this.

Quick Time animation
Credit: NASA/Fermi/Cruz deWilde

These gamma-ray pulsars show that gamma rays must form in a broader region than believed previously. Here, you can see the radio beams (green) never intersect Earth, but the pulsed gamma rays (magenta) do.


Animation 2
Credit: NASA/Goddard Space Flight Center Conceptual Image Lab


But gamma ray pulsars are no longer lighthouses, as pointed out here.


Animation 3
Credit: NASA/Dana Berry

Isolated pulsars slowly slow down their spin, but if a pulsar “lives” in a binary system with a normal star, it actually goes faster and faster. As a result, you could have a pulsar that spins in just a few miliseconds. How fast can they go?? It’s still uncertain.