Neutron Star Archives

January 6, 2014March 14, 2017 by Fraser Cain

Will The Sun Explode?

All stars die, some more violently than others.

Once our own Sun has consumed all the hydrogen fuel in its core, it too will reach the end of its life. Astronomers estimate this to be a short 7 billion years from now. For a few million years, it will expand into a red giant, puffing away its outer layers. Then it’ll collapse down into a white dwarf and slowly cool down to the background temperature of the Universe.

I’m sure you know that some other stars explode when they die. They also run out of fuel in their core, but instead of becoming a red giant, they detonate in a fraction of a second as a supernova.

So, what’s the big difference between stars like our Sun and the stars that can explode as supernovae?

Mass. That’s it.

Supernova progenitors – these stars capable of becoming supernovae – are extremely massive, at least 8 to 12 times the mass of our Sun. When a star this big runs out of fuel, its core collapses. In a fraction of a second, material falls inward to creating an extremely dense neutron star or even a black hole. This process releases an enormous amount of energy, which we see as a supernova.

If a star has even more mass, beyond 140 times the mass of the Sun, it explodes completely and nothing remains at all. If these other stars can detonate like this, is it possible for our Sun to explode?

Could there be some chain reaction we could set off, some exotic element a rare comet could introduce on impact, or a science fiction doomsday ray we could fire up to make the Sun explode?

Nope, quite simply, it just doesn’t have enough mass. The only way this could ever happen is if it was much, much more massive, bringing it to that lower supernovae limit.

In other words, you would need to crash an equally massive star into our Sun. And then do it again, and again.. and again… another half dozen more times. Then, and only then would you have an object massive enough to detonate as a supernova.

We don't have to worry about our sun exploding into a supernova. — We don’t have to worry about our sun exploding into a supernova.

Now, I’m sure you’re all resting easy knowing that solar detonation is near the bottom of the planetary annihilation list. I’ve got even better news. Not only will this never happen to the Sun, but there are no large stars close enough to cause us any damage if they did explode.
A supernova would need to go off within a distance of 100 light-years to irradiate our planet.

According to Dr. Phil Plait from Bad Astronomy, the closest star that could detonate as a supernova is the 10 solar mass Spica, at a distance of 260 light-years. No where near close enough to cause us any danger.

So don’t worry about our Sun exploding or another nearby star going supernova and wiping us out. You can put your feet up and relax, as it’s just not going to happen.

December 9, 2013December 23, 2015 by Elizabeth Howell

This Spooky X-Ray ‘Hand’ Demonstrates A Pulsar Star Mystery

This X-ray nebula appears to look like a human hand. The ghostly shape comes courtesy of a pulsar star called PSR B1509-58 (B1509 for short) that is just 12 miles or 19 kilometers in diameter. The nebula itself is 150 light-years across. Image taken by NASA's Chandra X-ray Observatory. Credit: NASA/CXC/CfA/P. Slane et al.

That spooky hand in the image above is producing questions for scientists. While the shape only coincidentally looks like a human hand, scientists are still trying to figure out how a small star produced such a large shape visible in X-rays.

Pulsar star PSR B1509-58 (or B1509 for short) is a 12-mile (19-kilometer) remnant of a much larger star that exploded and left behind a quickly spinning neutron star. Energy leaves mostly via neutrino (or neutral particle) emission, with a bit more coming out via beta decay, or a radioactive process where charged particles leave from atoms.

Using a new model, scientists found that so much energy comes out from neutrino emission that there shouldn’t be enough left for the beta decay to set off the X-rays you see here in this image, or in other situations. Yet it’s still happening. And that’s why they’re hoping to take a closer look at the situation.

“Scientists are intrigued by what exactly powers these massive explosions, and understanding this would yield important insights about the fundamental forces in nature, especially on the astronomical/cosmological scale,” stated Peter Moller, who is with the theoretical division of Los Alamos National Laboratory and participated in the research.

Preliminary studies indicate that to better understand what’s happening on the surface of these objects, computer models must endeavor to “describe the shape of each individual nuclide” (or atom that has a certain number of protons and neutrons in its nucleus). That’s because not all of these nuclides are simple spheres.

Using facilities at Los Alamos, scientists created databases with different types of nuclides that had various beta-decay properties. They then plugged this into a Michigan State University model of neutron stars to see what energy was released as the stars accrete or come together.

Accretion can cause neutron stars to flare violently

The results stood against what was a “common assumption”, the scientists stated, that the radioactive action would be enough to power the X-rays. They urge more study on this front, especially using a proposed Facility for Rare Isotope Beams that would be built at Michigan State, using funding from the U.S. Department of Energy Office of Science. FRIB project participants are hoping that will be ready in the 2020s.

You can read more about the research in the Dec. 1 edition of Nature. It was led by Hendrik Schatz, a professor at the National Superconducting Cyclotron Laboratory at Michigan State.

Source: Los Alamos National Laboratory

May 29, 2013December 23, 2015 by Elizabeth Howell

Suddenly Slowing Star Could Give Hints Of Its Interior

Why would a spinning star suddenly slow down? Even after writing a scientific paper about the phenomenon, astronomers still appear to be in shock-and-awe mode about what they saw.

“I looked at the data and was shocked — the … star had suddenly slowed down,” stated Rob Archibald, a graduate student at McGill University in Montreal. “These stars are not supposed to behave this way.”

Archibald led a group that was observing a neutron star, a type of really, really dense object created after huge stars run out of gas and collapse. The studied star (called 1E 2259+586, if you’re curious) has a massive magnetic field that places it in a subcategory of neutron stars called magnetars.

Anyway, the astronomers were watching over the magnetar with the NASA Swift X-ray telescope, just to get a sense of the star’s rotation and also to keep an eye out for the odd X-ray explosion commonly seen in stars of this type. But to see its spin rate reduce — that was definitely something unexpected.

An artistic impression of a magnetar with a very complicated magnetic field at its interior and a simple small dipolar field outside. Credits: ESA - Author: Christophe Carreau — An artistic impression of a magnetar with a very complicated magnetic field at its interior and a simple small dipolar field outside. Credits: ESA – Author: Christophe Carreau

Previous neutron star observations have showed them suddenly rotating faster (as if spinning up to several hundred times a second wasn’t enough.) This maneuver is called a glitch, and is thought to happen because the neutron has some sort of fluid (sometimes called a “superfluid”) inside that drives the rotation.

So now, the astronomers had evidence of an “anti-glitch”, a star slowing down instead of speeding up. It wasn’t by much (just a third of a part per million in the seven-second rotation rate), but while it happened they also saw X-rays substantially increase from the magnetar. Astronomers believe that something major happened either inside, or near the surface of the star.

The magnetic field surrounding the mysterious magnetar (NASA) — The magnetic field surrounding a magnetar (NASA)

And, astronomers added, if they can figure out what is happening, it could shed some light on what exactly is going on in that dense interior. Maybe the fluid is rotating at different rates, or something else is going on.

“Such behaviour is not predicted by models of neutron star spin-down and, if of internal origin, is suggestive of differential rotation in the magnetar, supporting the need for a rethinking of glitch theory for all neutron stars,” read a paper on the results.

The work was released today (May 29) at the Canadian Astronomical Society (CASCA)’s annual meeting, held this year in Vancouver.

You can read the entire paper in Nature.

Credit: CASCA/McGill University

February 15, 2013December 23, 2015 by Jason Major

Galactic Gas Cloud Could Help Spot Hidden Black Holes

Illustration of gas cloud G2 approaching Sgr A* . Our central supermassive black hole periodically snacks on clouds and other material like this. That gives off X-rays and other emissions. (ESO/MPE/M.Schartmann/J.Major)

The heart of our Milky Way galaxy is an exotic place. It’s swarming with gigantic stars, showered by lethal blasts of high-energy radiation and a veritable cul-de-sac for the most enigmatic stellar corpses known to science: black holes. And at the center of the whole mélange is the granddaddy of all the black holes in the galaxy — Sagittarius A*, a supermassive monster with 4 million times more mass than the Sun packed into an area smaller than the orbit of Mercury.

Sgr A* dominates the core of the Milky Way with its powerful gravity, trapping giant stars into breakneck orbits and actively feeding on anything that comes close enough. Recently astronomers have been watching the movement of a large cloud of gas that’s caught in the pull of Sgr A* — they’re eager to see what exactly will happen once the cloud (designated G2) enters the black hole’s dining room… it will, in essence, be the first time anyone watches a black hole eat.

But before the dinner bell rings — estimated to be sometime this September — the cloud still has to cover a lot of space. Some scientists are now suggesting that G2’s trip through the crowded galactic nucleus could highlight the locations of other smaller black holes in the area, revealing their hiding places as it passes.

In a new paper titled “G2 can Illuminate the Black Hole Population near the Galactic Center” researchers from Columbia University in New York City and the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts propose that G2, a cloud of cool ionized gas over three times more massive than Earth, will likely encounter both neutron stars and other black holes on its way around (and/or into) SMBH Sgr A*.

*Estimated number of stellar-mass black holes to be encountered by G2 along its trajectory (Bartos et al.)*

The team notes that there are estimated to be around 20,000 stellar-mass black holes and about as many neutron stars in the central parsec of the galaxy. (A parsec is equal to 3.26 light-years, or 30.9 trillion km. In astronomical scale it’s just over 3/4 the way to the nearest star from the Sun.) In addition there may also be an unknown number of intermediate-mass black holes lurking within the same area.

These ultra-dense stellar remains are drawn to the center region of the galaxy due to the effects of dynamical friction — drag, if you will — as they move through the interstellar material.

Of course, unless black holes are feeding and actively throwing out excess gobs of hot energy and matter due to their sloppy eating habits, they are very nearly impossible to find. But as G2 is observed moving along its elliptical path toward Sgr A*, it could very well encounter a small number of stellar- and intermediate-mass black holes and neutron stars. According to the research team, such interactions may be visible with X-ray spotting spacecraft like NASA’s Chandra and NuSTAR.

*NuSTAR X-ray image of a flare emitted by Sgr A* in July 2012 (NASA/JPL-Caltech)*

The chances of G2 encountering black holes and interacting with them in such a way as to produce bright enough x-ray flares that can be detected depends upon a lot of variables, like the angles of interaction, the relative velocities of the gas cloud and black holes, the resulting accretion rates of in-falling cloud matter, and the temperature of the accretion material. In addition, any observations must be made at the right time and for long enough a duration to capture an interaction (or possibly multiple interactions simultaneously) yet also be able to discern them from any background X-ray sources.

Still, according to the researchers such observations would be important as they could provide valuable information on galactic evolution, and shed further insight into the behavior of black holes.

Read the full report here, and watch an ESO news video about the anticipated behavior of the G2 gas cloud around the SMBH Sgr A* below:

This research was conducted by Imre Bartos, Zoltán Haiman, and Bence Kocsis of Columbia University and Szabolcs Márka of the Harvard-Smithsonian Center for Astrophysics.

February 2, 2012December 24, 2015 by Tammy Plotner

Supernova G350 Kicks Up Some X-Ray Dust

Vital clues about the devastating ends to the lives of massive stars can be found by studying the aftermath of their explosions. In its more than twelve years of science operations, NASA's Chandra X-ray Observatory has studied many of these supernova remnants sprinkled across the Galaxy. Credit: X-ray: NASA/CXC/SAO/I.Lovchinsky et al, IR: NASA/JPL-Caltech

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Located some 14,700 light years from the Earth toward the center of our galaxy, a newly photographed supernova remnant cataloged as G350.1+0.3 is making astronomers scratch their heads. The star which created this unusual visage is suspected to have blown its top some 600 to 1,200 years ago. Although it would have been as bright as the event which created the “Crab”, chances are no one saw it due to the massive amounts of gas and dust at the Milky Way’s heart. Now NASA’s Chandra X-ray Observatory and the ESA’s XMM-Newton telescope has drawn back the curtain and we’re able to marvel at what happens when a supernova imparts a powerful X-ray “kick” to a neutron star!

g350_420_labeled — Credit: X-ray: NASA/CXC/SAO/I.Lovchinsky et al, IR: NASA/JPL-Caltech

Photographic proof from Chandra and XMM-Newton are full of clues which give rise to the possibility that a compact object located in the influence of G350.1+0.3 may be the core region of a shattered star. Since it is off-centered from the X-ray emissions, it must have received a powerful blast of energy during the supernova event and has been moving along at a speed of 3 million miles per hour ever since. This information agrees with an “exceptionally high speed derived for the neutron star in Puppis A and provides new evidence that extremely powerful ‘kicks’ can be imparted to neutron stars from supernova explosions.”

As you look at the photo, you’ll notice one thing in particular… the irregular shape. The Chandra data in this image appears as gold while the infrared data from NASA’s Spitzer Space Telescope is colored light blue. According to the research team, this unusual configuration may have been caused by the stellar debris field imparting itself into the surrounding cold molecular gas.

These results appeared in the April 10, 2011 issue of The Astrophysical Journal. The scientists on this paper were Igor Lovchinsky and Patrick Slane (Harvard-Smithsonian Center for Astrophysics), Bryan Gaensler (University of Sydney, Australia), Jack Hughes (Rutgers University), Stephen Ng (McGill University), Jasmina Lazendic (Monash University Clayton, Australia), Joseph Gelfand (New York University, Abu Dhabi), and Crystal Brogan (National Radio Astronomy Observatory).

Original Story Source: NASA Chandra News Release.

December 1, 2011December 24, 2015 by Jason Major

Did a Neutron Star Create the “Christmas Burst”?

A neutron star's outer atmosphere engulfs another star in this concept rendering. (NASA/GSFC)

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On December 25, 2010, at 1:38 p.m. EST, NASA’s Swift Burst Alert Telescope detected a particularly long-lived gamma-ray burst in the constellation Andromeda. Lasting nearly half an hour, the burst (known as GRB 101225A) originated from an unknown distance, leaving astronomers to puzzle over exactly what may have created such a dazzling holiday display.

Now there’s not just one but two theories as to what caused this burst, both reported in papers by a research team from the Institute of Astrophysics in Granada, Spain. The papers will appear in the Dec. 1 issue of Nature.

Gamma-ray bursts are the Universe’s most luminous explosions. Most occur when a massive star runs out of nuclear fuel. As the star’s core collapses, it creates a black hole or neutron star that sends intense jets of gas and radiation outwards. As the jets shoot into space they strike gas previously shed by the star and heat it, generating bright afterglows.

If a GRB jet happens to be aimed towards Earth it can be detected by instruments like those aboard the Swift spacecraft.

Luckily GRBs usually come from vast distances, as they are extremely powerful and could potentially pose a danger to life on Earth should one strike directly from close enough range. Fortunately for us the odds of that happening are extremely slim… but not nonexistent. That is one reason why GRBs are of such interest to astronomers… gazing out into the Universe is, in one way, like looking down the barrels of an unknown number of distant guns.

The 2010 “Christmas burst”, as the event also called, is suspected to feature a neutron star as a key player. The incredibly dense cores that are left over after a massive star’s death, neutron stars rotate extremely rapidly and have intense magnetic fields.

One of the new theories envisions a neutron star as part of a binary system that also includes an expanding red giant. The neutron star may have potentially been engulfed by the outer atmosphere of its partner. The gravity of the neutron star would have caused it to acquire more mass and thus more momentum, making it spin faster while energizing its magnetic field. The stronger field would have then fired off some of the stellar material into space as polar jets… jets that then interacted with previously-expelled gases, creating the GRB detected by Swift.

This scenario puts the source of the Christmas burst at around 5.5 billion light-years away, which coincides with the observed location of a faint galaxy.

An alternate theory, also accepted by the research team, involves the collision of a comet-like object and a neutron star located within our own galaxy, about 10,000 light-years away. The comet-like body could have been something akin to a Kuiper Belt Object which, if in a distant orbit around a neutron star, may have survived the initial supernova blast only to end up on a spiraling path inwards.

The object, estimated to be about half the size of the asteroid Ceres, would have broken up due to tidal forces as it neared the neutron star. Debris that impacted the star would have created gamma-ray emission detectable by Swift, with later-arriving material extending the duration of the GRB into the X-ray spectrum… also coinciding with Swift’s measurements.

Both of these scenarios are in line with processes now accepted by researchers as plausible explanations for GRBs thanks to the wealth of data provided by the Swift telescope, launched in 2004.

“The beauty of the Christmas burst is that we must invoke two exotic scenarios to explain it, but such rare oddballs will help us advance the field,” said Chryssa Kouveliotou, a co-author of the study at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

More observations using other instruments, such as the Hubble Space Telescope, will be needed to discern which of the two theories is most likely the case… or perhaps rule out both, which would mean something else entirely is the source of the 2010 Christmas burst!

October 7, 2011December 24, 2015 by Tammy Plotner

The Crab Gets Cooked With Gamma Rays

X-ray: NASA/CXC/ASU/J. Hester et al.; Optical: NASA/HST/ASU/J. Hester et al.; Radio: NRAO/AUI/NSF Image of the Crab Nebula combines visible light (green) and radio waves (red) emitted by the remnants of a cataclysmic supernova explosion in the year 1054. and the x-ray nebula (blue) created inside the optical nebula by a pulsar (the collapsed core of the massive star destroyed in the explosion). The pulsar, which is the size of a small city, was discovered only in 1969. The optical data are from the Hubble Space Telescope, and the radio emission from the National Radio Astronomy Observatory, and the X-ray data from the Chandra Observatory.

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It’s one of the most famous sights in the night sky… and 957 years ago it was bright enough to be seen during the day. This supernova event was one of the most spectacular of its kind and it still delights, amazes and even surprises astronomers to this day. Think there’s nothing new to know about M1? Then think again…

An international collaboration of astrophysicists, including a group from the Department of Physics in Arts & Sciences at Washington University in St. Louis, has detected pulsed gamma rays coming from the heart of the “Crab”. Apparently the central neutron star is putting off energies that can’t quite be explained. These pulses between range 100 and 400 billion electronvolts (Gigaelectronvolts, or GeV), far higher than 25 GeV, the most energetic radiation recorded. To give you an example, a 400 GeV photon is almost a trillion times more energetic than a light photon.

“This is the first time very-high-energy gamma rays have been detected from a pulsar – a rapidly spinning neutron star about the size of the city of Ames but with a mass greater than that of the Sun,” said Frank Krennrich, an Iowa State professor of physics and astronomy and a co-author of the paper.

We can thank the Arizona based Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of four 12-meter Cherenkov telescopes covered in 350 mirrors for the findings. It is continually monitoring Earth’s atmosphere for the fleeting signals of gamma-ray radiation. However, findings like these on such a well-known object is nearly unprecedented.

“We presented the results at a conference and the entire community was stunned,” says Henric Krawczynski, PhD, professor of physics at Washington University. The WUSTL group led by James H. Buckley, PhD, professor of physics, and Krawczynski is one of six founding members of the VERITAS consortium.

crabpulsar — An X-ray image of the Crab Nebula and pulsar. Image by the Chandra X-ray Observatory, NASA/CXC/SAO/F. Seward.

We know the Crab’s story and how its pulsar sweeps around like a lighthouse… But Krennrich said such high energies can’t be explained by the current understanding of pulsars. Not even curvature radiation can be at the root of these gamma-ray emissions.

“The pulsar in the center of the nebula had been seen in radio, optical, X-ray and soft gamma-ray wavelengths,” says Matthias Beilicke, PhD, research assistant professor of physics at Washington University. “But we didn’t think it was radiating pulsed emissions above 100 GeV. VERITAS can observe gamma-rays between100 GeV and 30 trillion electronvolts (Teraelectronvolts or TeV).”

Just enough to cook one crab… well done!

Original Story Source: Iowa State University News Release. For Further Reading: Washington University in St. Louis News Release.