It was the brightest supernova in nearly 400 years when it lit the skies of the southern hemisphere in February 1987. Supernova 1987A – the explosion of a blue supergiant star in the nearby mini-galaxy known as the Large Magellanic Cloud – amazed the astronomical community. It offered them an unprecedented opportunity to observe an exploding star in real-time with modern instruments and telescopes. But something was missing. After the supernova faded, astronomers expected to find a neutron star (a hyper-dense, collapsed stellar core, made largely of neutrons) left-over at the heart of the explosion. They saw nothing.Continue reading “Astronomers Think They’ve Found the Neutron Star Remnant Left Behind from Supernova 1987A”
When stars reach the end of their main sequence, they undergo a gravitational collapse, ejecting their outermost layers in a supernova explosion. What remains afterward is a dense, spinning core primarily made up of neutrons (aka. a neutron star), of which only 3000 are known to exist in the Milky Way Galaxy. An even rarer subset of neutron stars are magnetars, only two dozen of which are known in our galaxy.
These stars are especially mysterious, having extremely powerful magnetic fields that are almost powerful enough to rip them apart. And thanks to a new study by a team of international astronomers, it seems the mystery of these stars has only deepened further. Using data from a series of radio and x-ray observatories, the team observed a magnetar last year that had been dormant for about three years, and is now behaving somewhat differently.
The study, titled “Revival of the Magnetar PSR J1622–4950: Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR“, recently appeared in The Astrophysical Journal. The team was led by Dr Fernando Camilo – the Chief Scientist at the South African Radio Astronomy Observatory (SARAO) – and included over 200 members from multiple universities and research institutions from around the world.
Magnetars are so-named because their magnetic fields are up to 1000 times stronger than those of ordinary pulsating neutron stars (aka. pulsars). The energy associated with these these fields is so powerful that it almost breaks the star apart, causing them to be unstable and display great variability in terms of their physical properties and electromagnetic emissions.
Whereas all magnetars are known to emit X-rays, only four have been known to emit radio waves. One of these is PSR J1622-4950 – a magnetar located about 30,000 light years from Earth. As of early 2015, this magnetar had been in a dormant state. But as the team indicated in their study, astronomers using the CSIRO Parkes Radio Telescope in Australia noted that it was becoming active again on April 26th, 2017.
At the time, the magnetar was emitting bright radio pulses every four seconds. A few days later, Parkes was shut down as part of a month-long planned maintenance routine. At about the same time, South Africa’s MeerKAT radio telescope began monitoring the star, despite the fact that it was still under construction and only 16 of its 64 radio dishes were available. Dr Fernando Camilo describes the discovery in a recent SKA South Africa press release:
“[T]he MeerKAT observations proved critical to make sense of the few X-ray photons we captured with NASA’s orbiting telescopes – for the first time X-ray pulses have been detected from this star, every 4 seconds. Put together, the observations reported today help us to develop a better picture of the behaviour of matter in unbelievably extreme physical conditions, completely unlike any that can be experienced on Earth”.
After the initial observations were made by the Parkes and MeerKAT observatories, follow-up observations were conducted using the XMM-Newton x-ray space observatory, Swift Gamma-Ray Burst Mission, the Chandra X-ray Observatory, and the Nuclear Spectroscopic Telescope Array (NuSTAR). With these combined observations, the team noted some very interesting things about this magnetar.
For one, they determined that PSR J1622-4950’s radio flux density, while variable, was approximately 100 times greater than it was during its dormant state. In addition, the x-ray flux was at least 800 times larger one month after reactivation, but began decaying exponentially over the course of a 92 to 130 day period. However, the radio observations noted something in the magnetar’s behavior that was quite unexpected.
While the overall geometry that was inferred from PSR J1622-4950’s radio emissions was consistent with what had been determined several years prior, their observations indicated that the radio emissions were now coming from a different location in the magnetosphere. This above all indicates how radio emissions from magnetars could differ from ordinary pulsars.
This discovery has also validated the MeerKAT Observatory as a world-class research instrument. This observatory is part of the Square Kilometer Array (SKA), the multi-radio telescope project that is building the world’s largest radio telescope in Australia, New Zealand, and South Africa. For its part, MeerKAT uses 64 radio antennas to gather radio images of the Universe to help astronomers understand how galaxies have evolved over time.
Given the sheer volume of data collected by these telescopes, MeerKAT relies on both cutting edge-technology and a highly-qualified team of operators. As Abbott indicated, “we have a team of the brightest engineers and scientists in South Africa and the world working on the project, because the problems that we need to solve are extremely challenging, and attract the best”.
Prof Phil Diamond, the Director-General of the SKA Organization leading the development of the Square Kilometer Array, was also impressed by the contribution of the MeerKAT team. As he stated in an SKA press release:
“Well done to my colleagues in South Africa for this outstanding achievement. Building such telescopes is extremely difficult, and this publication shows that MeerKAT is becoming ready for business. As one of the SKA precursor telescopes, this bodes well for the SKA. MeerKAT will eventually be integrated into Phase 1 of SKA-mid telescope bringing the total dishes at our disposal to 197, creating the most powerful radio telescope on the planet”.
When the SKA goes online, it will be one of the most powerful ground-based telescopes in the world and roughly 50 times more sensitive than any other radio instrument. Along with other next-generation ground-based and space-telescopes, the things it will reveal about our Universe and how it evolved over time are expected to be truly groundbreaking.
Host: Fraser Cain (@fcain)
Special Guest: Daniel Stern, Project Scientist on NuSTAR.
Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg )
Alessondra Springmann (@sondy)
Kimberly Cartier (@AstroKimCartier )
Continue reading “Weekly Space Hangout – Nov. 13, 2015: Daniel Stern, Project Scientist on NuSTAR”
Morgan Rehnberg (cosmicchatter.org / @MorganRehnberg )
Alessondra Springmann (@sondy)
Continue reading “Weekly Space Hangout – May 1, 2015: Prof. Coel Hellier, WASP & SuperWASP”
The combined observations from two generations of X-Ray space telescopes have now revealed a more complete picture of the nature of high-speed winds expelled from super-massive black holes. Scientist analyzing the observations discovered that the winds linked to these black holes can travel in all directions and not just a narrow beam as previously thought. The black holes reside at the center of active galaxies and quasars and are surrounded by accretion discs of matter. Such broad expansive winds have the potential to effect star formation throughout the host galaxy or quasar. The discovery will lead to revisions in the theories and models that more accurately explain the evolution of quasars and galaxies.
The observations were by the XMM-Newton and NuSTAR x-ray space telescopes of the quasar PDS 456. The observations were combined into the graphic, above. PDS 456 is a bright quasar residing in the constellation Serpens Cauda (near Ophiuchus). The data graph shows both a peak and a trough in the otherwise nominal x-ray emission profile as shown by the NuSTAR data (pink). The peak represents X-Ray emissions directed towards us (i.e.our telescopes) while the trough is X-Ray absorption that indicates that the expulsion of winds from the super-massive black hole is in many directions – effectively a spherical shell. The absorption feature caused by iron in the high speed wind is the new discovery.
X-Rays are the signature of the most energetic events in the Cosmos but also are produced from some of the most docile bodies – comets. The leading edge of a comet such as Rosetta’s P67 generates X-Ray emissions from the interaction of energetic solar ions capturing electrons from neutral particles in the comet’s coma (gas cloud). The observations of a super-massive black hole in a quasar billions of light years away involve the generation of x-rays on a far greater scale, by winds that evidently has influence on a galactic scale.
The study of star forming regions and the evolution of galaxies has focused on the effects of shock waves from supernova events that occur throughout the lifetime of a galaxy. Such shock waves trigger the collapse of gas clouds and formation of new stars. This new discovery by the combined efforts of two space telescope teams provides astrophysicists new insight into how star and galaxy formation takes place. Super-massive blackholes, at least early in the formation of a galaxy, can influence star formation everywhere.
Both the ESA built XMM-Newton and the NuSTAR X-Ray space telescope, a SMEX class NASA mission, use grazing incidence optics, not glass (refraction) or mirrors (reflection) as in conventional visible light telescopes. The incidence angle of the X-rays must be very shallow and consequently the optics are extended out on a 10 meter (33 foot) truss in the case of NuSTAR and over a rigid frame on the XMM-Newton.
The ESA built XMM-Newton was launched in 1999, an older generation design that used a rigid frame and structure. All the fairing volume and lift capability of the Ariane 5 launch vehicle was needed to put the Newton in orbit. The latest X-Ray telescope – NuSTAR – benefits from tens years of technological advances. The detectors are more efficient and faster and the rigid frame was replaced with a compact truss which required all of 30 minutes to deploy. Consequently, NuSTAR was launched on a Pegasus rocket piggybacked on a L-1011, a significantly smaller and less expensive launch system.
So now these observations are effectively delivered to the theorists and modelers. The data is like a new ingredient in the batter from which a galaxy and stars are formed. The models of galaxy and star formation will improve and will more accurately describe how quasars, with their active super-massive black-holes, transition into more quiescent galaxies such as our own Milky Way.
What if you had x-ray vision like Superman? Or if those funny-looking glasses they advertised in comic books in the 60s actually worked?* Then with those our Sun might look something like this, lighting up with brilliant flares of high-energy x-rays as seen by NASA’s super-sensitive NuSTAR Space Telescope (with a little help from SDO.)
Of course NASA’s orbiting NuSTAR x-ray telescope is not like a typical medical imaging system. Instead of looking for broken bones, NuSTAR (short for Nuclear Spectroscopic Telescope Array) is made to detect high-energy particles blasting across the Universe from exotic objects like supermassive black holes, pulsars, and supernovae.
But astronomers suggested turning NuSTAR’s gaze upon our own Sun to see what sorts of x-ray activity may be going on there.
“At first I thought the whole idea was crazy,” said Fiona Harrison, a Professor of Physics and Astronomy at Caltech and PI for the NuSTAR mission. “Why would we have the most sensitive high energy X-ray telescope ever built, designed to peer deep into the universe, look at something in our own back yard?”
As it turns out NuSTAR was able to reveal some very interesting features on the Sun, showing where the corona is being heated to very high temperatures. The image above shows NuSTAR’s first observations, overlaid onto data acquired by NASA’s Solar Dynamics Observatory.
NuSTAR data is shown in green and blue, revealing high-energy emission around – but not exactly aligned with – active regions on the Sun where solar plasma is being heated to more than 3 million degrees. The red represents ultraviolet light captured by SDO and shows material in the solar atmosphere at a slightly cooler 1 million degrees.
Because the Sun isn’t terribly intense in high energy x-ray output it’s safe to observe it with NuSTAR — it’s not likely to burn out the telescope’s sensors. But what NuSTAR can detect may help astronomers determine the exact mechanisms behind the intense coronal heating that occurs in and above the Sun’s chromosphere. If so-called “nanoflares” — miniature and as-yet-invisible versions of solar flares — are responsible, for instance, NuSTAR might be able to catch them in action for the first time.
“NuSTAR will be exquisitely sensitive to the faintest X-ray activity happening in the solar atmosphere, and that includes possible nanoflares,” said David Smith, solar physicist and member of the NuSTAR team at the University of California, Santa Cruz.
In addition NuSTAR could potentially detect the presence of axions in the Sun’s core — hypothesized particles that may make up dark matter in the Universe.
NuSTAR may not be a “solar telescope” per se, but that won’t stop astronomers from using its unique abilities to learn more about the star we intimately share space with.
“NuSTAR will give us a unique look at the Sun, from the deepest to the highest parts of its atmosphere.”
– David Smith, solar physicist, University of California Santa Cruz
*I never did get my box of 100 army men, either. Then again, I may have ordered a few decades too late.
A research team led by Caltech astronomers of Pasadena California have discovered an ultraluminous X-ray (ULX) source that is pulsating. Their analysis concluded that the source in a nearby galaxy – M82 – is from a rotating neutron star, a pulsar. This is the first ULX source attributed to a pulsar.
Matteo Bachetti of the Université de Toulouse in France first identified the pulsating source and is the lead author of the paper, “An ultraluminous X-ray source powered by an accreting neutron star” in the journal Nature. Caltech astronomer Dr. Fiona Harrison, the team leader, stated “This compact little stellar remnant is a real powerhouse. We’ve never seen anything quite like it. We all thought an object with that much energy had to be a black hole.”
What is most extraordinary is that this discovery places even more strain on theories already hard pressed to explain the existence of ultraluminous X-Ray sources. The burden falls on the shoulder of the theorists.
The source of the observations is the NuSTAR space telescope, a SMEX class NASA mission. It is a Wolter telescope that uses grazing incidence optics, not glass (refraction) or mirrors (reflection) as in visible light telescopes. The incidence angle of the X-rays must be very shallow and consequently the optics are extended out on a 10 meter (33 feet) truss. NuSTAR records its observations with a time stamp such as taking a video of the sky. The video recording in high speed is not in visible everyday light but what is called hard x-rays. Only gamma rays are more energetic. X-rays emanate from the most powerful sources and events in the Universe. NuStar observes in the energy range of X-Rays from 5 to 80 KeV (electron volt)while the famous Chandra space telescope observes in the .1 to 10 KeV range. Chandra is one NASA’s great space telescope, was launched by the Space Shuttle Columbia (STS-93) in 1999. Chandra has altered our view of the Universe as dramatically as the first telescope constructed by Galileo. NuSTAR carries on the study of X-rays to higher energies and with greater acuity.
ULX sources are rare in the Universe but this is the first pulsating ULX. After analysis, they concluded that this is not a black hole but rather its little brother, a spinning neutron star as the source. More specifically, this is an accreting binary pulsar; matter from a companion star is being gravitationally attracted by and accreting onto the pulsar.
Take a neutron star and spin it up to anywhere from 700 rotations per second to a mere one rotation every 10 seconds. Now you have a neutron star called a pulsar. Spinning or not, these are the remnants of supernovae, stellar explosions that can outshine a galaxy of 300 billion stars. Just one teaspoon of neutron star material weighs 10 million tons (9,071,847,400 kg). That is the same weight as 900 Great Pyramids of Giza all condensed to one teaspoon. As incredible a material and star that a neutron star is, they were not thought to be the source of any ultraluminous X-Ray sources. This view has changed with the analysis of observations by this research team utilizing NuSTAR. The telescope name – NuSTAR – stands for Nuclear Spectroscopic Telescope Array.
There is nothing run of the mill about black holes. Dr. Stephen Hawking only conceded after 25 years, in 2004 (the Thorne-Hawking Bet) that Black Holes exist. And still today it is not absolutely certain. Recall the Universe Today weekly – Space Hangout on September 26 – “Do Black Holes exist?” and the article by Jason Major, “There are no such things as Black Holes.”
Pulsars stars are nearly as exotic as black holes, and all astronomers accept the existence of these spinning neutron stars. There are three final states of a dying star. Stars like our Sun at the end of their life become very dense White Dwarf stars, about the size of the Earth. Neutron stars are the next “degenerate” state of a dying exhausted star. All the electrons have merged with the protons in the material of the star to become neutrons. A neutron star is a degenerate form of matter effectively made up of all neutron particles. Very dense, these stars are really small, the size of cities, about 16 miles in diameter. The third type of star in its final state is the Black Hole.
A spinning neutron star creates a magnetic field, the most powerful of such fields in the Universe. They are like a dipole of a bar magnet and because of how magnetic fields confine the hot gases – plasma – of the neutron star, constant streams of material flow down and light streams out from the magnetic poles.
Recently, the Earth has had incredible northern lights, aurora. These lights are also from hot gases — a plasma — at the top of our atmosphere. Likewise, hot energetic particles from the Sun are funneled down into the magnetic poles of the Earth’s field that creates the northern lights. For spinning neutron stars – pulsars – the extreme light from the magnetic poles are like beacons. Just like our Earth, the magnetic poles and the spin axis poles do not coincide. So the intense beacon of light will rotate around and periodically point at the Earth. The video of the first illustration describes this action.
The light beacons from pulsars are very bright but theory, until now, has been supported by observations. No ultraluminous X-ray sources should be pulsars. The newly discovered pulsar is outputting 100 times more energy than any other. Discoveries like the one by these astronomers utilizing NuSTAR is proof that there remains more to discover and understand and new telescopes will be conceived to help resolve questions raised by NuSTAR or Chandra.
Further reading: JPL
Supernovas are some of the most energetic and powerful events in the observable Universe. Briefly outshining entire galaxies, they are the final, dying outbursts of stars several times more massive than our Sun. And while we know supernovas are responsible for creating the heavy elements necessary for everything from planets to people to power tools, scientists have long struggled to determine the mechanics behind the sudden collapse and subsequent explosion of massive stars.
Now, thanks to NASA’s NuSTAR mission, we have our first solid clues to what happens before a star goes “boom.”
The image above shows the supernova remnant Cassiopeia A (or Cas A for short) with NuSTAR data in blue and observations from the Chandra X-ray Observatory in red, green, and yellow. It’s the shockwave left over from the explosion of a star about 15 to 25 times more massive than our Sun over 330 years ago*, and it glows in various wavelengths of light depending on the temperatures and types of elements present.
Previous observations with Chandra revealed x-ray emissions from expanding shells and filaments of hot iron-rich gas in Cas A, but they couldn’t peer deep enough to get a better idea of what’s inside the structure. It wasn’t until NASA’s Nuclear Spectroscopic Telescope Array — that’s NuSTAR to those in the know — turned its x-ray vision on Cas A that the missing puzzle pieces could be found.
And they’re made of radioactive titanium.
Many models have been made (using millions of hours of supercomputer time) to try to explain core-collapse supernovas. One of the leading ones has the star ripped apart by powerful jets firing from its poles — something that’s associated with even more powerful (but focused) gamma-ray bursts. But it didn’t appear that jets were the cause with Cas A, which doesn’t exhibit elemental remains within its jet structures… and besides, the models relying on jets alone didn’t always result in a full-blown supernova.
As it turns out, the presence of asymmetric clumps of radioactive titanium deep within the shells of Cas A, revealed in high-energy x-rays by NuSTAR, point to a surprisingly different process at play: a “sloshing” of material within the progenitor star that kickstarts a shockwave, ultimately tearing it apart.
Watch an animation of how this process occurs:
The sloshing, which occurs over a time span of a mere couple hundred milliseconds — literally in the blink of an eye — is likened to boiling water on a stove. When the bubbles break through the surface, the steam erupts.
Only in this case the eruption leads to the insanely powerful detonation of an entire star, blasting a shockwave of high-energy particles into the interstellar medium and scattering a periodic tableful of heavy elements into the galaxy.
In the case of Cas A, titanium-44 was ejected, in clumps that echo the shape of the original sloshing asymmetry. NuSTAR was able to image and map the titanium, which glows in x-ray because of its radioactivity (and not because it’s heated by expanding shockwaves, like other lighter elements visible to Chandra.)
“Until we had NuSTAR we couldn’t really see down into the core of the explosion,” said Caltech astronomer Brian Grefenstette during a NASA teleconference on Feb. 19.
“Previously, it was hard to interpret what was going on in Cas A because the material that we could see only glows in X-rays when it’s heated up. Now that we can see the radioactive material, which glows in X-rays no matter what, we are getting a more complete picture of what was going on at the core of the explosion.”
– Brian Grefenstette, lead author, Caltech
Okay, so great, you say. NASA’s NuSTAR has found the glow of titanium in the leftovers of a blown-up star, Chandra saw some iron, and we know it sloshed and ‘boiled’ a fraction of a second before it exploded. So what?
“Now you should care about this,” said astronomer Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics. “Supernovae make the chemical elements, so if you bought an American car, it wasn’t made in Detroit two years ago; the iron atoms in that steel were manufactured in an ancient supernova explosion that took place five billion years ago. And NuSTAR shows that the titanium that’s in your Uncle Jack’s replacement hip were made in that explosion too.
“We’re all stardust, and NuSTAR is showing us where we came from. Including our replacement parts. So you should care about this… and so should your Uncle Jack.”
And it’s not just core-collapse supernovas that NuSTAR will be able to investigate. Other types of supernovas will be scrutinized too — in the case of SN2014J, a Type Ia that was spotted in M82 in January, even right after they occur.
“We know that those are a type of white dwarf star that detonates,” NuSTAR principal investigator Fiona Harrison responded to Universe Today during the teleconference. “This is very exciting news… NuSTAR has been looking at [SN2014J] for weeks, and we hope to be able to say something about that explosion as well.”
One of the most valuable achievements of the recent NuSTAR findings is having a new set of observed constraints to place on future models of core-collapse supernovas… which will help provide answers — and likely new questions — about how stars explode, even hundreds or thousands of years after they do.
“NuSTAR is pioneering science, and you have to expect that when you get new results, it’ll open up as many questions as you answer,” said Kirshner.
Launched in June of 2012, NuSTAR is the first focusing hard X-ray telescope to orbit Earth and the first telescope capable of producing maps of radioactive elements in supernova remnants.
*As Cas A resides 11,000 light-years from Earth, the actual date of the supernova would be about 11,330 years ago. Give or take a few.
One star player in this week’s findings out of the 223rd meeting of the American Astronomical Society has been the Nuclear Spectroscopic Telescope Array Mission, also known as NuSTAR. On Thursday, researchers revealed some exciting new results and images from the mission, as well as what we can expect from NuSTAR down the road.
Part of a new series of low-cost missions, NuSTAR is the first of its kind to employ a space telescope focusing on the high energy X-ray end of the spectrum centered around 5-80 KeV.
Daniel Stern, part of the NuSTAR team at JPL Caltech, revealed a new X-ray image of the now-famous supernova remnant dubbed “The Hand of God.” Discovered by the Einstein X-ray observatory in 1982, the Hand is home to pulsar PSR B1509-58 or B1509 for short, and sits about 18,000 light years away in the southern hemisphere constellation Circinus. B1509 spins about 7 times per second, and the supernova that formed the pulsar is estimated to have occurred 20,000 years ago and would’ve been visible form Earth about 2,000 years ago.
While the Chandra X-ray observatory has scrutinized the region before, NuSTAR can peer into its very heart. In fact, Stern notes that views from NuSTAR take on less of an appearance of a “Hand” and more of a “Fist”. Of course, the appearance of any nebula is a matter of perspective. Pareidolia litter the deep sky, whether it’s the Pillars of Creation to the Owl Nebula. We can’t help but being reminded of the mysterious “cosmic hand” that the Guardians of Oa of Green Lantern fame saw when they peered back at the moment of creation. Apparently, the “Hand” is also rather Simpson-esque, sporting only three “fingers!”
NuSTAR is the first, and so far only, focusing hard X-ray observatory deployed in orbit. NuSTAR employs what’s known as grazing incidence optics in a Wolter telescope configuration, and the concentric shells of the detector look like layers on an onion. NuSTAR also requires a large focal length, and employs a long boom that was deployed shortly after launch.
The hard X-ray regime that NuSTAR monitors is similar to what you encounter in your dentist’s office or in a TSA body scanner. Unlike the JEM-X monitor aboard ESA’s INTERGRAL or the Swift observatory, which have a broad resolution of about half a degree to a degree, NuSTAR has an unprecedented resolution of about 18 arc seconds.
The first data release from NuSTAR was in late 2013. NuSTAR is just begging to show its stuff, however, in terms of what researchers anticipate that it’s capable of.
“NuSTAR is uniquely able to map the Titanium-44 emission, which is a radioactive tracer of (supernova) explosion physics,” Daniel Stern told Universe Today.
NuSTAR will also be able to pinpoint high energy sources at the center of our galaxy. “No previous high-energy mission has had the imaging resolution of NuSTAR,” Stern told Universe Today. ”Our order-of-magnitude increase in image sharpness means that we’re able to map out that very rich region of the sky, which is populated by supernovae remnants, X-ray binaries, as well as the big black hole at the center of our Galaxy, Sagittarius A* (pronounced “A-star).”
Yale University researcher Francesca Civano also presented a new image from NuSTAR depicting black holes that were previously obscured from view. NuSTAR is especially suited for this, gazing into the hearts of energetic galaxies that are invisible to observatories such Chandra or XMM-Newton. The image presented covers the area of Hubble’s Cosmic Evolution Survey, known as COSMOS in the constellation Sextans. In fact, Civano notes that NuSTAR has already seen the highest number of obscured black hole candidates to date.
“This is a hot topic in astronomy,” Civano said in a recent press release. “We want to understand how black holes grew and the degree to which they are obscured.”
To this end, NuSTAR researchers are taking a stacked “wedding cake” approach, looking at successively larger slices of the sky from previous surveys. These include looking at the quarter degree field of the Great Observatories Origins Deep Survey (GOOD-S) for 18 days, the two degree wide COSMOS field for 36 days, and the large four degree Swift-BAT fields for 40 day periods hunting for serendipitous sources.
Interestingly, NuSTAR has also opened the window on the hard X-ray background that permeates the universe as well. This peaks in the 20-30 KeV range, and is the combination of the X-ray emissions of millions of black holes.
“For several decades already, we’ve known what the sum total emission of the sky is across the X-ray regime,” Stern told Universe Today. “The shape of this cosmic X-ray background peaks strongly in the NuSTAR range. The most likely interpretation is that there are a large number of obscured black holes out there, objects that are hard to find in other energy bands. NuSTAR should find these sources.”
And NuSTAR may just represent the beginning of a new era in X-ray astronomy. ESA is moving ahead with its next generation flagship X-ray mission, known as Athena+, set to launch sometime next decade. Ideas abound for wide-field imagers and X-ray polarimeters, and one day, we may see a successor to NuSTAR dubbed the High-Energy X-ray Probe or (HEX-P) make it into space.
But for now, expect some great science out of NuSTAR, as it unlocks the secrets of the X-ray universe!
A distinctive flash of light emanating from a dying star may make it possible for astronomers to watch a black hole being born, according to new research.
This burst of light, which might last three to 10 days, could be visible in optical light and also in infrared, which shows the heat signature of cosmic objects. While not as bright as a supernova — an exploding star — this signal could occur somewhere in the sky as often as once a year, according to simulations performed at the California Institute of Technology.
“That flash is going to be very bright, and it gives us the best chance for actually observing that this event occurred,” stated Caltech postdoctoral scholar Tony Piro, who led the research that is published in Astrophysical Journal Letters. “This is what you really want to look for.”
A big star essentially turns into a black hole when it falls into itself due to its large mass. The collapse shoots out protons and electrons from the core, creating neutrons and temporarily turning the core into a neutron star (a really, really dense object). This process also makes up neutrinos, which are infinitesimal but also extremely fast, moving nearly as fast as light does and bleeding the star of energy.
A 1980 paper, CalTech stated, showed that “this rapid loss of mass means that the gravitational strength of the dying star’s core would abruptly drop.” Hydrogen-filled layers at the top of the star would then fall outward and create a shock wave moving at more than two million miles an hour.
More recently, astronomers at the University of California, Santa Cruz discovered that the shock wave’s friction against the gas would heat up the plasma and make it glow, potentially for as long as a year. But that would be very faint from Earth-borne telescopes.
This is where the new CalTech research comes in. The university is already involved in black hole research, including the Nuclear Spectroscopic Telescope Array (NuSTAR). You can check out a video about NuSTAR below.
Piro’s simulations focus on when shock waves hit the surface of the star. It’s this process that would produce a burst of light, perhaps 10 to 100 times brighter than the other glow that astronomers foresaw.
The next step will be trying to observe these events as soon as they happen. Caltech advertised several survey possibilities related to its research: the Palomar Transient Factory, the intermediate Palomar Transient Factory that started work in February and the even more advanced Zwicky Transient Facility (ZTF) that is expected to start up in 2015.
Of course, it’s quite possible that other telescopes on the ground or orbit could work to confirm this signal.