Neutron Stars: Ripples in Space-Time Could Reveal 'Strange Stars' - video

By looking for ripples in the fabric of space-time, scientists could soon detect "strange stars," objects made of stuff radically different from the particles that make up ordinary matter, researchers say.

The protons and neutrons that make up the nuclei of atoms are made of more basic particles known as quarks.

There are six types, or "flavours," of quarks: up, down, top, bottom, charm and strange. Each proton or neutron is made of three quarks: Each proton is composed of two up quarks and one down quark, and each neutron is made of two down quarks and one up quark.

In theory, matter can be made with other flavours of quarks as well. Since the 1970s, scientists have suggested that particles of "strange matter" known as strangelets, made of equal numbers of up, down and strange quarks, could exist.

In principle, strange matter should be heavier and more stable than normal matter, and might even be capable of converting ordinary matter it comes in contact with into strange matter.

Scene from a NASA animation showing two neutron stars colliding.

Credit: NASA's Goddard Space Flight Center

However, lab experiments have not yet created any strange matter, so its existence remains uncertain.

One place strange matter could naturally be created is inside neutron stars, the remnants of stars that died in catastrophic explosions known as supernovas.

Neutron stars are typically small, with diameters of about 12 miles (19 kilometers) or so, but are so dense that they weigh as much as the sun.

A chunk of a neutron star the size of a sugar cube can weigh as much as 100 million tons.

Under the extraordinary force of this extreme weight, some of the up and down quarks that make up neutron stars could get converted into strange quarks, leading to strange stars made of strange matter, researchers say.

A strange star that occasionally spurts out strange matter could quickly convert a neutron star orbiting it in a binary system into a strange star as well.

Prior research suggests that a neutron star that receives a seed of strange matter from a companion strange star could transition to a strange star in just 1 millisecond to 1 second.

The researchers suggest that events involving strange stars could explain two short gamma-ray bursts, giant explosions lasting less than 2 seconds, seen in deep space in 2005 and 2007.

The Laser Interferometer Gravitational-Wave Observatory (LIGO) did not detect gravitational waves from either of these events, dubbed GRB 051103 and GRB 070201.

Future research could detect strange-star events. Using the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), whose first observing run is scheduled for 2015, the researchers expect to detect about 0.13 mergers per year of neutron stars with strange stars, or about one such merger every eight years.

Using the Einstein Telescope currently being designed in the European Union, the scientists eventually expect to detect about 700 such events per year, or about two per day.

Cosmic explosion spotted in neighbouring galaxy - video

NASA's Swift satellite reported an enormous explosion occurred this morning at 8.15 AEST in our neighbouring galaxy, Andromeda. This explosion is known as a Gamma Ray Burst (GRB), one of the most powerful explosions in the Universe.

The exact cause is unknown but thought to be an explosion from when two Neutron Stars collide.

These Neutron Stars are the dead cores of massive stars, with the mass of our Sun crushed into the size of a small city. When they merge together, the explosion is so powerful it can be seen from across the Universe.

Swinburne University of Technology astronomer Dr Alan Duffy says these GRBs explosions are so large that if they occur within our galaxy they can potentially trigger mass extinctions on Earth.

"Telescopes around the world are currently trained on the Andromeda galaxy looking in all wavelengths of light to learn more about this once-in-a-lifetime event."

"The explosion seen in light will also potentially be visible in gravitational waves, a key prediction of Einstein, ending a long quest to detect these ripples in space time."

"Unfortunately the world-wide facility for detecting these events, LIGO, is currently shut down for an upgrade, missing out on the explosion and a potential Nobel Prize winning discovery."

This animation shows the merger of two neutron stars from a horizontal perspective. Theory predicts that these kinds of collisions would not produce a long afterglow because there isn't much "fuel" dust and gas from the objects and in the region to sustain an afterglow. 

Credit: NASA

"The night sky seen in high-energy light is continuously flashing as titanic explosions, bright enough to be seen from across the length of the Universe, erupt and travel to us. It's a violent world out there.

"The most astounding aspect of today is that colliding Neutron Stars exploded in less than a second, shining out in Gamma Rays which have travelled undisturbed for 2.5 million years until hitting NASA's Swift satellite, within minutes telescopes across the globe were tracking it and an hour later people around the world were following it on Twitter. It's been hectic.

Watch 2 Neutron Stars Merge and Form Black Hole - Video

An amazing new NASA video shows two super-dense neutron stars tearing each other apart in a cataclysmic cosmic merger that ultimately forms a black hole.

The neutron star collision video, which was produced by scientists at NASA's Goddard Space Flight Center, is a supercomputer simulation. It starts off with two neutron stars — the city-size, dense remnants of a violent supernova explosion — separated by about 11 miles (18 kilometers), NASA officials said.

One object contains about 1.7 times the mass of our sun, while the other weighs in at 1.4 solar masses.

The two neutron stars spiral toward each other, deforming. As they get closer and closer to each other, the bigger stellar remnant crushes the smaller one, causing it to erupt and form a spiral arm around the larger neutron star, according to NASA.

"At 13 milliseconds, the more massive star has accumulated too much mass to support it against gravity and collapses, and a new black hole is born," NASA officials said in a statement.

"The black hole's event horizon, its point of no return, is shown by the gray sphere. While most of the matter from both neutron stars will fall into the black hole, some of the less-dense, faster-moving matter manages to orbit around it, quickly forming a large and rapidly rotating torus."

Neutron stars form when a star that is eight to 30 times the mass of the sun explodes as a supernova, leaving behind the compressed, dense core.

One cubic centimeter (0.06 cubic inches) of neutron star matter outweighs Mount Everest, NASA officials said.

In 2013, scientists found that mergers of neutron stars could create the gold in the universe. A group of astronomers, led by Edo Berger of the Harvard-Smithsonian Center for Astrophysics, discovered that the collisions of neutron stars could eject as much as 10 moon masses' worth of gold.

CAASTRO Astronomers Make precise measurement of neutron star

The densely packed matter of a pulsar spins at incredible speeds, and emits radio waves that can be observed from Earth, but how neutron stars emit these waves is still a mystery. 

Credit: Swinburne Astronomy Productions /CAASTRO.

An international team of astronomers has made a measurement of a distant neutron star that is one million times more precise than the previous world's best.

The researchers were able to use the interstellar medium (ISM), the 'empty' space between stars and galaxies that is made up of sparsely spread charged particles, as a giant lens to magnify and look closely at the radio wave emission from a small rotating neutron star.

This technique yielded the highest resolution measurement ever achieved, equivalent to being able to see the double-helix structure of our genes from the Moon!

"Compared to other objects in space, neutron stars are tiny – only tens of kilometres in diameter – so we need extremely high resolution to observe them and understand their physics," Dr Jean-Pierre Macquart from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) in Perth, Australia, said.

Dr Macquart, a member of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), said neutron stars were particularly interesting objects to study, as some of them – called pulsars – gave off pulsed radio waves whose beams swept across telescopes at regular intervals.

"More than 45 years since astronomers discovered pulsars, we still don't understand the mechanism by which they emit radio wave pulses," he said.



A spinning neutron star emitting a stream of radio waves that appear as regular pulses when observed from Earth. Simulation credit to Swinburne Astronomy Productions /CAASTRO.

The researchers found they could use the distortions of these pulse signals as they passed through the turbulent interstellar medium (ISM) to reconstruct a close in view of the pulsar from thousands of individual sub-images of the pulsar.

"The best we could previously do was pointing a large number of radio telescopes across the world at the same pulsar, using the distance between the telescopes on Earth to get good resolution," Dr Macquart said.

The previous record using combined views from many telescopes was an angular resolution of 50 microarcseconds, but the team - led by Professor Ue-Li Pen of the Canadian Institute of Theoretical Astrophysics and a CAASTRO Partner Investigator, has now proven their 'interstellar lens' can get down to 50 picoarcseconds, or a million times more detail, resolving areas of less than 5km in the emission region.

"Our new method can take this technology to the next level and finally get to the bottom of some hotly debated theories about pulsar emission," Professor Pen said.

This new technique also opens up the possibilities for precise distance measurements to pulsars that orbit a companion star and 'image' their extremely small orbits, which is ultimately a new and highly sensitive test of Einstein's theory of General Relativity," Professor Pen said.

More information: Ue-Li Pen, Jean-Pierre Macquart, Adam T. Deller, and Walter Brisken. "50 picoarcsec astrometry of pulsar emission." MNRAS (May 01, 2014) Vol. 440 L36-L40 first published online February 14, 2014. DOI: 10.1093/mnrasl/slu010 . 

Also available on arXiv: http://adsabs.harvard.edu/abs/2014MNRAS.440L..36P

Spanish Research: Black hole that doesn't emit x-rays discovered near massive star

Trailed intensity image of the two lines constructed from the phase binned spectra. 

Two orbital cycles are displayed for clarity. 

The colour scale indicates counts normalised to the continuum, with the black colour corresponding to 0.98 and the white colour to 1.08 in Fe II and 1.16 in HeII. 

Credit: Nature 

Researchers in Instituto de Astrofísica de Canarias, Universidad de Alicante, Universitat de Barcelona, and Institut de Ciències de l’Espai (IEEC-CSIC), Spain have discovered a black hole that doesn't reveal itself through x-ray radiation thrown off by material that is being sucked into it.

In their paper published in the journal Nature, team members from several research institutions throughout Spain, report that the black hole appears to exist as a companion (binary) to a massive Be star that spins so fast it's surrounded by a gas disk.

I. Negueruela

Up until now, virtually all black holes have been discovered via x-ray radiation signals—as material is pulled in past the point of no return, radiation is flung out into space where it is noted by space scientists here on Earth.

In this new effort, the research team was able to identify the black hole because of its behaviour, rather than its signature.

Many Be stars have been found to have companions—most of the time they are supernova remnants (neutron stars) but never before has a Be star been found to have a black hole as a companion.

The star, named MWC 656 is really big—approximately 10 to 16 times as massive as our sun. It spins really fast too (approximately 671,000 mph) which the researchers say, explains why the black hole next to it doesn't emit any radiation.

J. Casares

They suggest that because the star is spinning so fast, it casts gas into a disk surrounding its equator which in turn is cast off towards the black hole, but rather than being pulled in, the gas joins an accretion disk that surrounds the "mouth" of the black hole, moving so fast (due to the angular momentum of the gas cast off from the star) that it can't be pulled in. Thus the disk simply continues to grow larger.

The black hole is pretty big too (approximately 3.8 to 6.9 more massive than our sun) which likely puts it in the category of stellar mass black holes—those that come into existence when a star runs out of fuel.

The discovery of the "silent" black hole suggests that many more like it might exist, which will undoubtedly lead researchers to look for more, now that they know what to look for.

More information: A Be-type star with a black-hole companion, Nature 505, 378–381 (16 January 2014) J. Casares, I. Negueruela, M. Ribó, I. Ribas, J. M. Paredes, A. Herrero & S. Simón-Díaz DOI: 10.1038/nature12916

New Type of Matter Found: 'Nuclear Pasta' in Neutron Stars

Artistic representation of a neutron star. The layer of "nuclear pasta" would be located in the innermost crust, near the core.

CREDIT: University of Alicante

A rare state of matter dubbed "nuclear pasta" appears to exist only inside ultra-dense objects called neutron stars, astronomers say.

There, the nuclei of atoms get crammed together so tightly that they arrange themselves in patterns akin to pasta shapes — some in flat sheets like lasagna and others in spirals like fusilli.

And these formations are likely responsible for limiting the maximum rotation speed of these stars, according to a new study.

"Such conditions are only reached in neutron stars, the most dense objects in the universe besides black holes," said astronomer José Pons of Alicante University in Spain.

This new phase of matter had been proposed by theorists years ago, but was never experimentally verified.

Now, Pons and his colleagues have used the spin rates of a class of neutron stars called pulsars to offer the first evidence that nuclear pasta exists.

Pulsars emit light in a pair of beams that shoot out like rays from a lighthouse. As the pulsars spin, the beams rotate in and out of view, making the stars appear to "pulse" on and off, and allowing astronomers to calculate how fast the stars are spinning.

Researchers have observed dozens of pulsars, but have never discovered one with a spin period longer than 12 seconds.

"In principle, that is not expected. You should see some with larger periods," Pons told reporters. A longer spin period would mean the star is spinning more slowly.

But the pasta matter could explain the absence of pulsars with longer spin periods. The researchers realized that if atomic nuclei inside the stars were reorganizing into pasta formations, this matter would increase the electric resistivity of the stars, making it harder for electrons to travel through the material.

This, in turn, would cause the stars' magnetic fields to dissipate much faster than expected. Normally, pulsars slow their spin down by radiating electromagnetic waves, which causes the stars to lose angular momentum.

But if the stars' magnetic fields are already limited, as would happen with pasta-matter, they cannot radiate electromagnetic waves as strongly, so they cannot spin down.

This keeps the pulsars stuck at a minimum spin speed, or a maximum spin period.

"Making this connection between the observational astronomical effect, which is the existence of this upper spin period limit, with the need for this layer in the inner crust, is what makes the connection between observations and theory," Pons said.

Neutron stars form when massive stars reach the end of their lives and run out of fuel for nuclear fusion. These aging stars explode in supernovas, their cores collapsing into small, dense objects.

The resulting masses are so dense, in fact, that normal atoms cannot exist anymore. Instead, protons and electrons essentially melt into each other, producing neutrons as well as lightweight particles called neutrinos.

The end result is a neutron star, whose mass is 90-percent neutrons.

In these stars' crusts, which have been found to be billions of times stronger than steel, normal atomic nuclei made of protons and neutrons can still exist, albeit densely squished, and this is where the new pasta formations appear.

In normal matter, the separation among nuclei is huge (relatively speaking), as positively charged atomic nuclei don't like to be near each other.

"But in neutron stars, matter is very packed and nuclei are so close to each other that they almost touch," Pons said."It's like a huge, gigantic nuclei, a huge continuum."

The research was published June 9 in the journal Nature Physics.

NASA Sextant Mission: Navigation by using Neutron Stars - Video

NASA's Goddard Space Flight Center is developing a new instrument that uses the natural beacons of pulsar radiation, to let spacecraft find their way in deep space. A test on ISS is planned. 

 Credit: NASA / GSFC