Tag Archives: neutron

Artist's rendering.

We might have found the first black hole to eat a neutron star

We might have found the first ever recorded case of a black hole swallowing a neutron star.

Artist's rendering.

Artist’s rendering of the black hole consuming the neutron star.
Image credits Carl Knox / OzGrav Centre of Excellence.

Research led by members from The Australian National University (ANU) report detecting a black hole swallowing a neutron star for the first time on Wednesday 14 August 2019.

Big Meal

“About 900 million years ago, this black hole ate a very dense star, known as a neutron star, like Pac-man—possibly snuffing out the star instantly,” said Professor Susan Scott from the ANU Research School of Physics, who leads the General Relativity Theory and Data Analysis Group.

Both neutron stars and black holes are super-dense remnands of dead stars, and some of the most extreme forms of matter in the known universe. And now, we might have stumbled upon a merger of these two.

Earlier this month, gravitational-wave sensor arrays in the United States and Italy detected ripples in space and time which point to a previously unseen event of cataclysmic proportions — a black hole consuming a neutron star. We’re safe in our corner of the solar system, however: the event took place around 8,550 million trillion kilometres away from Earth.

Professor Scott, also a Chief Investigator with the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), says that the discovery completes the “trifecta of observations” that the team has been striving towards: the merger of two black holes, the collision of two neutron stars, and the merger between a black hole and a neutron star.

“The ANU SkyMapper Telescope responded to the detection alert and scanned the entire likely region of space where the event occurred, but we’ve not found any visual confirmation,” she explains.

Researchers are still crunching the data to confirm the exact size of the two stellar bodies. Until the final results are published in peer-reviewed scientific journals, take them with a pinch of salt — however, preliminary data suggests it’s highly that what we’re seeing is a black hole enveloping a neutron star.

“Scientists have never detected a black hole smaller than five solar masses or a neutron star larger than about 2.5 times the mass of our Sun,” Professor Scott said.

“Based on this experience, we’re very confident that we’ve just detected a black hole gobbling up a neutron star.

“However, there is the slight but intriguing possibility that the swallowed object was a very light black hole—much lighter than any other black hole we know about in the Universe. That would be a truly awesome consolation prize.”

The data was recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO), the most advanced instrument of its kind ever build that comprises twin detectors in the US, and Virgo, a gravitational-wave detector in Italy run by the European Gravitational Observatory.

Neutron star.

The Universe’s densest stars have a maximum mass limit, researchers find

Researchers from the Goethe University in Frankfurt have refined our understanding of neutron stars by calculating the hard limit for their mass: these extreme stellar bodies cannot exceed 2.16 solar masses.

Neutron star.

Image credits Kevin Gill / Flickr.

Neutron stars are one of the most extreme displays of matter around. They’re the naked cores of massive stars, compressed into pure matter in their death throes moments before a supernova detonates. Neutron stars aren’t made of regular atoms (which are over 99.999% empty space) rather they resemble one huge atomic nucleus. True to their name, neutron stars are incandescent bodies of neutron next to neutron.

In many ways, neutron stars are the closest matter can get to a black hole without collapsing space-time around it. Which also raises an interesting question — how massive can these stars actually become?

Weight-watching

With radiuses that generally fall under 12 kilometers (7.45 miles) but with masses that can be twice as great as that of our sun, neutron stars produce gravitational fields comparable to those of black holes. Unlike their black-hole brethren, however, neutron stars can’t grow indefinitely. Since they’re so immensely dense, there’s almost no force in nature that can withstand their gravitational force. So, the logic goes, if they become massive enough, that same gravitational pull will overcome the neutron’s ability to resist it. Going by that same train of thought, there should be a point beyond which even the addition of a single neutron will send the neutron star collapsing into a black hole.

Researchers have been trying to determine that exact point ever since neutron stars were first discovered in the 1960s — a question which they’ve only managed to answer now, as astrophysicists at the Goethe University Frankfurt have successfully calculated the strict upper limit for a neutron star’s maximum mass.

With an accuracy within a few percentage points, the maximum mass of non-rotating neutron stars cannot exceed 2.16 solar masses, the team reports.

 

The result was based on the “universal relations” approach developed in Frankfurt a few years ago. In broad strokes, these relations say that since all neutrons stars “look alike”, their properties can be expressed in terms of dimensionless quantities. The next piece of the puzzle was supplied by the LIGO experiment, in the form of data on the gravitational-wave signals and subsequent electromagnetic radiation discharge (kilonova) recorded last year during the merging of two neutron stars.

The LIGO data was instrumental in solving the problem as they allowed the team to decouple the calculations from the equation of state — a model we use to describe matter and its composition at various depths in a star.

“The beauty of theoretical research is that it can make predictions,” says Professor Luciano Rezzolla, the paper’s first author. “Theory, however, desperately needs experiments to narrow down some of its uncertainties.”

“It’s therefore quite remarkable that the observation of a single binary neutron star merger that occurred millions of light years away combined with the universal relations discovered through our theoretical work have allowed us to solve a riddle that has seen so much speculation in the past.”

The results were published in a Letter titled “Using Gravitational-wave Observations and Quasi-universal Relations to Constrain the Maximum Mass of Neutron Stars” in The Astrophysical Journal. They were confirmed a few days after publication by groups from the USA and Japan who followed different and independent approaches.

New measurement of a proton leaves us with more questions than answers

Six years ago, physicists announced the results of a new measurement of the proton — and the particle turned out to be too short. Since then, a lot of effort has been put into checking their results — and again, the latest measurements have revealed smaller than expected results. Physicists are now left scratching their collective heads trying to pin down the elusive measurements of this particle.

Image via Pixabay

Protons are positively charged particles that, together with neutrons, form the nuclei of atoms. They’re really, really tiny — for years, the proton’s radius was set at about 0.877 femtometers. One femtometer being equal to 10−15 meters, slightly over a quadrillionth of a meter in diameter. This number, however, was changed in 2010, when Randolf Pohl from the Max Planck Institute of Quantum Optics in Germany used a novel measuring technique and got a better measurement for a proton’s size.

His team started from a simple hydrogen atom — which has one proton and one electron — and substituted its electron for a heavier particle called a muon. They then fired a laser at the altered atom, measuring the resulting change in its energy levels to calculate the size of the nucleus — which in the case of hydrogen is a single proton. They reported that their measurement of the particle came out 4% smaller than what other methods showed.

Measurements performed in 2013 confirmed the findings, setting the world of particle physics ablaze trying to find the answer to the “proton radius puzzle.”

Pohl also applied this technique to deuterium, a hydrogen isotope with one proton and one neutron — also known as a deutron in this case — in the nucleus. Accurately calculating the size of the deutron took plenty of time. Today, the team published the long-awaited result and, you’ll never guess it, it came up short again, this time by 0.8%.

Evangeline J. Downie at the George Washington University in Washington DC says that these numbers show the proton radius puzzle is here to stay.

“It tells us that there’s still a puzzle,” says Downie. “It’s still very open, and the only thing that’s going to allow us to solve it is new data.”

Several other similar experiments, both at Pohl’s and other labs around the world, are already underway. One such experiment will re-use the muon technique to measure the nucleus size of heavier atoms, such as helium.

Pohl believes the issue may not be with the proton itself, but rather with an incorrect measurement of the Rydberg constant which describes the wavelengths of light emitted by an excited atom. This constant’s value has been established very precisely in other experiments however, so something has to have gone really wrong for it to be inaccurate.

One other explanation proposes new particles that cause unexpected interactions between the proton and the muon, without changing its relationship with the electron. That could mean that the key to the puzzle lies beyond the standard model of particle physics.

“If at some point in the future, somebody will discover something beyond the standard model, it would be like this,” says Pohl.

New exotic particle behaviour found at CERN

The Large Hadron Collider at CERN has started doing some serious business. This time, an extremely rare particle containing equal parts of matter and antimatter popped up during experiments at the world’s largest and hottest particle accelerator.

CREDIT: CERN/Maximilien Brice, Rachel Barbier

 

The particle, named a B meson is made out of one quark (the building blocks of protons and neutrons) and one antiquark (the building blocks of antiprotons and antineutrons). What are antiprotons and antineutrons ? Well, they are just like their positive brothers… only they are negative. They have the exact same properties, only opposite in signs. For example, an antiproton has the exact same charge a proton has, but it is negative instead of positive.

All normal particles are thought to have antimatter analogues, and when matter and antimatter meets, they destroy each other. Scientists believe that at first, matter and antimatter were created equally, but if this is the case, then where is all the antimatter ? The most plausible solution would be that a huge quantity of matter and antimatter annihilated each other, and the remaining matter is what we see in our universe today.

The particle in case, the B meson, is thought to have been common right after the Big Bang, but it is believed that at the moment, it doesn’t occure naturally in nature. They aren’t stable, and after created, quickly start decaying; this process, a B meson decay has long been theoretized, but never seen before.

“Our experiment is set up to measure the decays of B mesons,” sayd Sheldon Stone, physicist at Syracuse University. “We discovered some new and interesting decay modes of B mesons, which hadn’t ever been seen before.”

Studying this type of behaviour can provide the answer to the ultimate question of antimatter – why do we see all this matter around us today, and no antimatter. Meanwhile, the search for the elusive Higgs boson is continued.

“When the universe was created in the Big Bang about 14 billion years ago, the number of particles and antiparticles was the same,” Stone said. “One of the major questions that we really don’t know the answer to is why are there particles around now and not antiparticles. By studying the differences we can learn maybe what the physics is behind that difference.”

Amazing NASA pic shows how galaxies collide

I gotta say, this is one of the most beautiful pictures I’ve seen all year ! This amazing image released by NASA shows a collision betweet two galaxies that began 100 million years ago (when dinosaurs were still kings) and is still happening today. The bright sources you see are in fact produced by huge amounts of material that falls on black holes and neutron stars (remnants of massive stars).

Credits: X-ray: NASA/CXC/SAO/J.DePasquale; IR: NASA/JPL-Caltech; Optical: NASA/STScI

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.