Credits: ESO

IN BRIEF

• Vacuum birefringence has been observed by a team of scientists for the first time ever using the European Southern Observatory's (ESO) Very Large Telescope (VLT).
• The team observed neutron star RX J1856.5-375, which is about 400 light-years from Earth, with just visible light, pushing the limits of existing telescope technology.

A LITTLE LESS STRANGE

Vacuum birefringence is a weird quantum phenomenon that has only ever been observed on an atomic scale. It occurs when a neutron star is surrounded by a magnetic field so intense, it’s given rise to a region in empty space where matter randomly appears and vanishes.

This polarization of light in a vacuum due to strong magnetic fields was first thought to be possible in the 1930s by physicists Werner Heisenberg and Hans Heinrich Euler as a product of the theory of quantum electrodynamics (QED). The theory describes how light and matter interact.

Now, for the first time ever, this strange quantum effect has been observed by a team of scientists from INAF Milan (Italy) and from the University of Zielona Gora (Poland).

Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), a research team led by Roberto Mignani observed neutron star RX J1856.5-375, which is about 400 light-years from Earth.

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Natalie Wolchoverm --  October 25, 2017 

Newly discovered “standard sirens” provide an independent, clean way to measure how fast the universe is expanding.

To many cosmologists, the best thing about neutron-star mergers is that these events scream into space an otherwise close-kept secret of the universe. Scientists combined the gravitational and electromagnetic signals from the recently detected collision of two of these stars to determine, in a cleaner way than with other approaches, how fast the fabric of the universe is expanding — a much-contested number called the Hubble constant.

In the days since the neutron-star collision was announced, Hubble experts have been surprised to find themselves discussing not whether events like it could settle the controversy, but how soon they might do so.

Scientists have hotly debated the cosmic expansion rate ever since 1929, when the American astronomer Edwin Hubble first established that the universe is expanding - and that it therefore had a beginning. How fast it expands reflects what’s in it (since matter, dark energy and radiation push and pull in different ways) and how old it is, making the value of the Hubble constant crucial for understanding the rest of cosmology.

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The core of a neutron star is such an extreme environment that physicists can’t agree on what happens inside. But a new space-based experiment — and a few more colliding neutron stars — should reveal whether neutrons themselves break down.

Joshua Sokol - Contributing Writer - October 30, 2017

The alerts started in the early morning of Aug. 17. Gravitational waves produced by the wreck of two neutron stars — dense cores of dead stars — had washed over Earth. The thousand-plus physicists of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) rushed to decode the space-time vibrations that rolled across the detectors like a drawn-out peal of thunder. Thousands of astronomers scrambled to witness the afterglow. But officially, all this activity was kept secret. The data had to be collected and analyzed, the papers written. The outside world wouldn’t know for two more months.

The strict ban put Jocelyn Read and Katerina Chatziioannou, two members of the LIGO collaboration, in a bit of an awkward situation. In the afternoon on the 17th, the two were scheduled to lead a panel at a conference dedicated to the question of what happens under the almost unfathomable conditions in a neutron star’s interior. Their panel’s topic? What a neutron-star merger would look like. “We sort of went off at the coffee break and sat around just staring at each other,” said Read, a professor at California State University, Fullerton. “OK, how are we going to do this?”

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ESO will hold a press conference on 16 October 2017 at 16:00 CEST, at its Headquarters in Garching, Germany, to present groundbreaking observations of an astronomical phenomenon that has never been witnessed before.

The event will be introduced from ESO’s Paranal Observatory in Chile by the Director General, Xavier Barcons, and will feature talks by representatives of many research groups around Europe.

This invitation is addressed exclusively at media representatives. To participate in the conference, bona fide members of the media must register by completing an online form. Please indicate whether you wish to come in person to the press conference or if you will participate online only.

By registering for the conference, journalists agree to honour an embargo, details of which will be provided after registration, and not to publish or discuss any of the material presented before the start of the conference on 16 October 2017 at 16:00 CEST.

On site journalists will have a question and answer session with panelists during the conference. We will also take questions from journalists participating online. In-person individual interviews right after the conference are also possible.

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Are we about to make a breakthrough to go beyond black holes? Here’s what it means if we do!

If there’s one major difference between General Relativity and Newtonian gravity, it’s this: in Einstein’s theory, nothing lasts forever. Even if you had two perfectly stable masses in orbit around one another — masses that never burned out, lost material, or otherwise changed — their orbits would eventually decay. Whereas in Newtonian gravity, two masses would orbit their mutual center of gravity for an eternity, relativity tells us that a tiny amount of energy gets lost with every moment that one mass is accelerated by the gravitational field it passes through. That energy doesn’t disappear, but gets carried away in the form of gravitational waves. Over long enough time periods, enough energy is radiated away that those two orbiting masses will touch and merge together. Three times, now, LIGO has seen this happen for black holes. But it may be about to take the next step, and see neutron stars merge for the first time.

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Sept. 5, 2017

By following up on mysterious high-energy sources mapped out by NASA's Fermi Gamma-ray Space Telescope, the Netherlands-based Low Frequency Array (LOFAR) radio telescope has identified a pulsar spinning at more than 42,000 revolutions per minute, making it the second-fastest known.

A pulsar is the core of a massive star that exploded as a supernova. In this stellar remnant, also called a neutron star, the equivalent mass of half a million Earths is crushed into a magnetized, spinning ball no larger than Washington, D.C. The rotating magnetic field powers beams of radio waves, visible light, X-rays and gamma rays. If a beam happens to sweep across Earth, astronomers observe regular pulses of emission and classify the object as a pulsar.

"Roughly a third of the gamma-ray sources found by Fermi have not been detected at other wavelengths," said Elizabeth Ferrara, a member of the discovery team at NASA's Goddard Space Center in Greenbelt, Maryland. "Many of these unassociated sources may be pulsars, but we often need follow-up from radio observatories to detect the pulses and prove it. There's a real synergy across the extreme ends of the electromagnetic spectrum in hunting for them."

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July 17, 2017

NASA’s new Neutron star Interior Composition Explorer (NICER) mission to study the densest observable objects in the universe has begun science operations.

Launched June 3 on an 18-month baseline mission, NICER will help scientists understand the nature of the densest stable form of matter located deep in the cores of neutron stars using X-ray measurements.

NICER operates around the clock on the International Space Station (ISS). In the two weeks following launch, NICER underwent extraction from the SpaceX Dragon spacecraft, robotic installation on ExPRESS Logistics Carrier 2 on board ISS and initial deployment. Commissioning efforts began June 14, as NICER deployed from its stowed launch configuration. All systems are functioning as expected.

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This image shows the configuration of NICER's 56 X-ray mirrors that will gather scientific observations and play an instrumental role in demonstration X-ray navigation. Credit: NASA

Nearly 50 years after British astrophysicist Jocelyn Bell discovered the existence of rapidly spinning neutron stars, NASA will launch the world's first mission devoted to studying these unusual objects.

The agency also will use the same platform to carry out the world's first demonstration of X-ray navigation in space.
The agency plans to launch the two-in-one Neutron Star Interior Composition Explorer, or NICER, aboard SpaceX CRS-11, a cargo resupply mission to the International Space Station to be launched aboard a Falcon 9 rocket.
About a week after its installation as an external attached payload, this one-of-a-kind investigation will begin observing neutron stars, the densest objects in the universe. The mission will focus especially on pulsars—those neutron stars that appear to wink on and off because their spin sweeps beams of radiation past us, like a cosmic lighthouse.

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May 26, 2017

A new NASA mission is headed for the International Space Station next month to observe one of the strangest observable objects in the universe.

Launching June 1, the Neutron Star Interior Composition Explorer (NICER) will be installed aboard the space station as the first mission dedicated to studying neutron stars, a type of collapsed star that is so dense scientists are unsure how matter behaves deep inside it.

A neutron star begins its life as a star between about seven and 20 times the mass of our sun. When this type of star runs out of fuel, it collapses under its own weight, crushing its core and triggering a supernova explosion. What remains is an ultra-dense sphere only about 12 miles (20 kilometers) across, the size of a city, but with up to twice the mass of our sun squeezed inside. On Earth, one teaspoon of neutron star matter would weigh a billion tons.

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The dishes of the Karl G. Jansky Very Large Array are seen making thefirst-ever precision localization of a Fast Radio Burst, and therebypointing the way to the host galaxy of FRB121102. Credit: Danielle Futselaar (artsource.nl)

One of the rare and brief bursts of cosmic radio waves that have puzzled astronomers since they were first detected nearly 10 years ago has finally been tied to a source: an older dwarf galaxy more than 3 billion light years from Earth.

Fast radio bursts, which flash for just a few milliseconds, created a stir among astronomers because they seemed to be coming from outside our galaxy, which means they would have to be very powerful to be seen from Earth, and because none of those first observed were ever seen again.

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Colour composite photo of the sky field around the lonely neutron star RX J1856.5-3754 in the constellation of Corona Australis and the related cone-shaped nebula. It is based on a series of exposures obtained with the multi-mode FORS2 instrument at VLT KUEYEN through three different optical filters. The trail of an asteroid is seen in the field with intermittent blue, green and red colours. RX J1856.5-3754 is exactly in the centre of the image. Image credit: ESO.

By studying the light emitted from an extraordinarily dense and strongly magnetised neutron star using ESO’s Very Large Telescope, astronomers may have found the first observational indications of a strange quantum effect, first predicted in the 1930s. The polarisation of the observed light suggests that the empty space around the neutron star is subject to a quantum effect known as vacuum birefringence.
A team led by Roberto Mignani from INAF Milan (Italy) and from the University of Zielona Gora (Poland), used ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile to observe the neutron star RX J1856.5-3754, about 400 light-years from Earth.

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Andromeda's pulsing neutron star. Credit: Andromeda: ESA/Herschel/PACS/SPIRE/J. Fritz, U. Gent/XMM-Newton/EPIC/W. Pietsch, MPE; data: P. Esposito et al. (2016)

Decades of searching in the Milky Way's nearby 'twin' galaxy Andromeda have finally paid off, with the discovery of an elusive breed of stellar corpse, a neutron star, by ESA's XMM-Newton space telescope.

Andromeda, or M31, is a popular target among astronomers. Under clear, dark skies it is even visible to the naked eye. Its proximity and similarity in structure to our own spiral galaxy, the Milky Way, make it an important natural laboratory for astronomers. It has been extensively studied for decades by telescopes covering the whole electromagnetic spectrum.
Despite being extremely well studied, one particular class of object had never been detected: spinning neutron stars.
Neutron stars are the small and extraordinarily dense remains of a once-massive star that exploded as a powerful supernova at the end of its natural life. They often spin very rapidly and can sweep regular pulses of radiation towards Earth, like a lighthouse beacon appearing to flash on and off as it rotates.

Read more 

L. G. Spitler, P. Scholz, J. W. T. Hessels, S. Bogdanov, A. Brazier, F. Camilo, S. Chatterjee, J. M. Cordes, F. Crawford, J. Deneva, R. D. Ferdman, P. C. C. Freire, V. M. Kaspi, P. Lazarus, R. Lynch, E. C. Madsen, M. A. McLaughlin, C. Patel, S. M. Ransom, A. Seymour, I. H. Stairs, B. W. Stappers, J. van Leeuwen & W. W. Zhu

Nature (2016) doi:10.1038/nature17168

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections9. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events10. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst4. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

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Gamma ray picture of the Milky Way, as seen by the NASA Fermi satellite. Inserts: two independent statistical analyses showed that the distribution of photons is clumpy rather than smooth, indicating that the excess gamma rays from the center of our galaxy are unlikely to be caused by dark matter annihilation.
Image courtesy of Christoph Weniger, UvA , © UvA/Princeton

The excess of gamma rays from the center of the Milky Way probably originates from rapidly rotating neutron stars and not from dark matter annihilation as previously claimed.

he puzzling excess of gamma rays from the center of the Milky Way probably originates from rapidly rotating neutron stars, or millisecond pulsars, and not from dark matter annihilation, as previously claimed. This is the conclusion of new data analyses by two independent research teams from the University of Amsterdam (UvA), Netherlands, and Princeton University/Massachusetts Institute of Technology (MIT).

In 2009, observations with the Fermi Large Area Telescope revealed an excess of high-energy photons, or gamma rays, at the center of our galaxy. It was long speculated that this gamma ray excess could be a signal of dark matter annihilation. If true, it would constitute a breakthrough in fundamental physics and a major step forward in our understanding of the matter constituents of the universe.

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Artist's concept of a millisecond pulsar. Credit: NASA

January 26, 2016 by Tomasz Nowakowski

(Phys.org)—NASA's Fermi Gamma-ray Space Telescope has once again proven that it is an excellent tool to search for rotating neutron stars emitting beams of electromagnetic radiation, known as pulsars. A team of astronomers, led by H. Thankful Cromartie of the University of Virginia, has recently used the 305-meter Arecibo radio telescope in Puerto Rico to observe unidentified sources of gamma rays detected by the Large Area Telescope (LAT) onboard the Fermi spacecraft. As it turns out, six of these objects indicated by LAT are rapidly rotating neutron stars, with periods of a few thousandths of a second, called millisecond pulsars (MSPs). The scientists published their results online on Jan. 20 on the arXiv pre-print server.

The objects of the study were chosen from the LAT's 4-year point source catalog. The astronomers chose 34 from over 1,000 unidentified sources of gamma rays to observe them in detail with the Arecibo telescope. The catalog provided crucial spectral data that helped distinguish possible MSPs from other gamma-ray-emitting objects, like active galactic nuclei (AGNs).

"Overall, the search for MSPs in the galactic disk has been made extremely efficient by employing Fermi-LAT data in selecting radio search targets," the researchers noted in their paper posted on arXiv.

Arecibo observations were conducted from June to September 2013. The telescope's raw sensitivity and its large gain makes it a very efficient tool for finding millisecond pulsars. Thanks to Arecibo, the researchers were able to detect six MSPs with rotation periods ranging between 1.99 and 4.66 ms. One of the newly detected pulsars is a typical neutron star, a white dwarf binary with an 83-day orbital period. According to the research, the other MSPs are in interacting compact binaries wit orbital period less than eight hours.

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