Star’s Dying Gasp May Signal Black Hole’s Birth

Where is the Nearest Black Hole
Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)

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.

Combining observations done with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist's impression.  Credit: ESO/L. Calçada
Combining observations done with ESO’s Very Large Telescope and NASA’s Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist’s impression. Credit: ESO/L. Calçada

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.

Source: California Institute of Technology

Astronomers Watch as a Black Hole Eats a Rogue Planet

Screen capture from the ESA video.

In Star Wars, the Millennium Falcon narrowly escaped being devoured by an exogorth (space slug) slumbering inside an asteroid crater. An unsuspecting rogue giant planet wasn’t as lucky. Astronomers using the Integral space observatory were able to watch as the planet was eaten by a black hole that had been inactive for decades. It woke up just in time to make a meal out of the unwary planet.

“The observation was completely unexpected, from a galaxy that has been quiet for at least 20–30 years,” says Marek Nikolajuk of the University of Bialystok, Poland, lead author of the paper in Astronomy & Astrophysics.

Nikolajuk and his team added that the event is a preview of a similar feeding event that is expected to take place with the black hole at the center of our own Milky Way Galaxy.

The discovery in galaxy NGC 4845, 47 million light-years away, was made by Integral, with follow-up observations from ESA’s XMM-Newton, NASA’s Swift and Japan’s MAXI X-ray monitor on the International Space Station.

Astronomers were using Integral to study a different galaxy when they noticed a bright X-ray flare coming from another location in the same wide field-of-view. Using XMM-Newton, the origin was confirmed as NGC 4845, a galaxy never before detected at high energies.

Along with Swift and MAXI, the emission was traced from its maximum in January 2011, when the galaxy brightened by a factor of a thousand, and then as it subsided over the course of the year.

By analyzing the characteristics of the flare, the astronomers could determine that the emission came from a halo of material around the galaxy’s central black hole as it tore apart and fed on an object of 14–30 Jupiter masses, and so the astronomers say the object was either a super-Jupiter or a brown dwarf.

This object appears to have been ‘wandering,’ which would fit the description of recent studies that have suggested that free-floating planetary-mass objects of this kind may occur in large numbers in galaxies, ejected from their parent solar systems by gravitational interactions.

The black hole in the center of NGC 4845 is estimated to have a mass of around 300,000 times that of our own Sun. The astronomers said it also appears to enjoy playing with its food: the way the emission brightened and decayed shows there was a delay of 2–3 months between the object being disrupted and the heating of the debris in the vicinity of the black hole.

“This is the first time where we have seen the disruption of a substellar object by a black hole,” said co-author Roland Walter of the Observatory of Geneva, Switzerland. “We estimate that only its external layers were eaten by the black hole, amounting to about 10% of the object’s total mass, and that a denser core has been left orbiting the black hole.”

The flaring event in NGC 4845 might be similar to what is expected to happen with the supermassive black hole at the center of our own Milky Way Galaxy, perhaps even this year, when an approaching Earth-mass gas cloud is expected to meet its demise.

Along with the object seen being eaten by the black hole in NGC 4845, these events will tell astronomers more about what happens to the demise of different types of objects as they encounter black holes of varying sizes.

“Estimates are that events like these may be detectable every few years in galaxies around us, and if we spot them, Integral, along with other high-energy space observatories, will be able to watch them play out just as it did with NGC 4845,” said Christoph Winkler, ESA’s Integral project scientist.

The team’s paper: Tidal disruption of a super-Jupiter in NGC 4845

Source: ESA

Hubble Uncovers Hidden Mysteries in Messier 77

The NASA/ESA Hubble Space Telescope has captured this vivid image of spiral galaxy Messier 77 — a galaxy in the constellation of Cetus, some 45 million light-years away from us. The streaks of red and blue in the image highlight pockets of star formation along the pinwheeling arms, with dark dust lanes stretching across the galaxy’s starry centre. The galaxy belongs to a class of galaxies known as Seyfert galaxies, which have highly ionised gas surrounding an intensely active centre. Credit: NASA, ESA & A. van der Hoeven

Discovered on October 29, 1780 by Pierre Mechain, this active Seyfert galaxy is magnificent to behold in amateur equipment and even more so in NASA/ESA Hubble Space Telescope photographs. Located in the constellation of Cetus and positioned about 45 million light years away, this spiral galaxy has a claim to fame not only for being strong in star formation, but as one of the most studied galaxies of its type. Cutting across its face are red hued pockets of gas where new suns are being born and dark dustlanes twist around its powerful nucleus.

When Mechain first observed this incredible visage, he mistook it for a nebula and Messier looked at it, but did not record it. (However, do not fault Messier for lack of interest at this time. His wife and newly born son had just died and he was mourning.) In 1783, Sir William Herschel saw it as an “Ill defined star surrounded by nebulousity.” but would change his tune some 8 years later when he reported: “A kind of much magnified stellar cluster; it contains some bright stars in the centre.” His son, John Herschel, would go on to catalog it – not being very descriptive either.

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This video zooms in on spiral galaxy Messier 77. The sequence begins with a view of the night sky near the constellation of Cetus. It then zooms through observations from the Digitized Sky Survey 2, and ends with a view of the galaxy obtained by Hubble. Credit:NASA, ESA, Digitized Sky Survey 2. Acknowledgement: A. van der Hoeven

At almost double the size of the Milky Way, we now know it is a barred spiral galaxy. According to spectral analysis, Messier 77 has very broad emission lines, indicating that giant gas clouds are rapidly moving out of this galaxy’s core, at several hundreds of kilometers per second. This makes M77 a Seyfert Type II galaxy – one with an expanding core of starbirth. In itself, that’s quite unique considering the amount of energy needed to expand at that rate and further investigations found a 12 light-year diameter, point-like radio source at its core enveloped in a 100 light year swath of interstellar matter. A miniature quasar? Perhaps… But whatever it is has a measurement of 15 million solar masses!

Deep at its heart, Messier 77 is beating out huge amounts of radiation – radiation suspected to be from an intensely active black hole. Here the “galaxy stuff” is constantly being drawn towards the center, heating and lighting up the frequencies. Just this area alone can shine tens of thousands of times brighter than most galaxies… but is there anything else hiding there?

“Active galactic nuclei (AGNs) display many energetic phenomena—broad emission lines, X-rays, relativistic jets, radio lobes – originating from matter falling onto a supermassive black hole. It is widely accepted that orientation effects play a major role in explaining the observational appearance of AGNs.” says W. Jaffe (et al). “Seen from certain directions, circum-nuclear dust clouds would block our view of the central powerhouse. Indirect evidence suggests that the dust clouds form a parsec-sized torus-shaped distribution. This explanation, however, remains unproved, as even the largest telescopes have not been able to resolve the dust structures.”

Before you leave, look again. Clustered about Messier 77’s spiral arms are deep red pockets – a sign of newly forming stars. Inside the ruby regions, neophyte stars are ionising the gas. The dust lanes also appear crimson as well – a phenomenon called “reddening” – where the dust absorbs the blue light and highlights the ruddy color. A version of this image won second place in the Hubble’s Hidden Treasures Image Processing Competition, entered by contestant Andre van der Hoeven.

Twistin’ the night away…

Black Holes, Fermi Bubbles and the Milky Way

Deep at the heart of our galaxy lurks a black hole. This isn’t exciting news, but neither is it a very exciting place. Or is it? While all might be quiet on the western front now, there may be evidence that our galactic center was once home to some pretty impressive activity – activity which may have included multiple collision events and mergers of black holes as it gorged on a satellite galaxies. Thanks to new insights from a pair of assistant professors, Kelly Holley-Bockelmann at Vanderbilt and Tamara Bogdanovic at Georgia Institute of Technology, we have more evidence which points to the Milky Way’s incredibly active past.

“Tamara and I had just attended an astronomy conference in Aspen, Colorado, where several of these new observations were announced,” said Holley-Bockelmann. “It was January 2010 and a snow storm had closed the airport. We decided to rent a car to drive to Denver. As we drove through the storm, we pieced together the clues from the conference and realized that a single catastrophic event – the collision between two black holes about 10 million years ago – could explain all the new evidence.”

Now, imagine a night sky illuminated by a a huge nebula, one that covers half the celestial sphere. This isn’t a dream, it’s a reality. These massive lobes of high-energy radiation are known as Fermi bubbles and they cover a region some 30,000 light years on either side of the Milky Way’s core. While we can’t observe them directly in visible light, these particles are moving along at close to 186,000 miles per second and glowing in x-ray and gamma ray wavelengths.

According to Fulai Guo and William G. Mathews of the University of California at Santa Cruz: “The Fermi bubbles provide plausible evidence for a recent powerful AGN jet activity in our Galaxy, shedding new insights into the origin of the halo CR population and the channel through which massive black holes in disk galaxies release feedback energy during their growth.”

However, our galactic center is home to more than just some incredible bubbles – it’s the location of three of the most massive clusters of young stars within the Milky Way’s realm. Known as the Central, Arches and Quintuplet clusters, each grouping houses several hundred hot, young stars which dwarf the Sun. They will live short, bright, violent lives… burning out in a scant few million years. Because they live fast and die young, these cluster stars must have formed within recent years during a eruption of star formation near the galactic center – another clue to this cosmic puzzle.

“Because of their high mass, and apparent top-heavy IMF, the Galactic Center clusters contain some of the most massive stars in the Galaxy. This is important, as massive stars are key ingredients and probes of astrophysical phenomena on all size and distance scales, from individual star formation sites, such as Orion, to the early Universe during the age of reionization when the first stars were born. As ingredients, they control the dynamical and chemical evolution of their local environs and individual galaxies through their influence on the energetics and composition of the interstellar medium.” says Donald F. Figer. “They likely play an important role in the early evolution of the first galaxies, and there is evidence that they are the progenitors of the most energetic explosions in the Universe, seen as gamma ray bursts. As probes, they define the upper limits of the star formation process and their presence likely ends further formation of nearby lower mass stars. They are also prominent output products of galactic mergers, starburst galaxies, and active galactic nuclei.”

To deepen the mystery, take a closer look at our central black hole. It spans about 40 light seconds in diameter and weighs about four million solar masses. According to what we know, this should produce intensive gravitational tides – ones that should be sucking in the surroundings. So how is it that astronomers have uncovered groups of new, bright stars closer than 3 light years from the event horizon? Of course, they could be on their way to oblivion, but the data shows these stars seem to have formed there. That’s quite a feat considering it would require a molecular cloud 10,000 times more dense than the one located at our galactic center! Shouldn’t there also be old stars located there as well? The answer is yes, there should be… but there are far fewer than what we can observe and what current theoretical models predict.

Holley-Bockelmann wasn’t about to let the problem rest. When she returned home, she enlisted the aid of Vanderbilt graduate student Meagan Lang to help solve the riddle. Then they recruited Pau Amaro-Seoane from the Max Planck Institute for Gravitational Physics in Germany, Alberto Sesana from the Institut de Ciències de l’Espai in Spain, and Vanderbilt Research Assistant Professor Manodeep Sinha to help. With so many bright minds to help solve this riddle, they soon arrived at a plausible explanation – one which matches observations and allows for testable predictions.

According to their theory, a Milky Way satellite galaxy began migrating towards our core. As it merged with our galaxy, its mass was torn away, leaving only its black hole and a small collection of gravitationally bound stars. After several million years, this “leftover” eventually reached the galactic center and the black holes began to merge. As the smaller black hole was swirled around the larger, it plowed up huge furrows of gas and dust, pushing it into the larger black hole and created the Fermi bubbles. The dueling gravitational forces weren’t gentle… these intense tides were quite capable of compressing the molecular clouds surrounding the core into the density required to produce fresh, young stars. Perhaps the very young stars we now observe at the galactic center?

However, there’s more to the picture than meets the eye. This same plowing of the cosmic turf would have also pushed out existing older stars from the vicinity of the massive central black hole. It’s a scene which fits current models where a black hole merger flings stars out into the galaxy at hyper velocities… a scene which fits the observation of a lack of old stars at the boundaries of our supermassive black hole.

“The gravitational pull of the satellite galaxy’s black hole could have carved nearly 1,000 stars out of the galactic centre,” said Bogdanovic. “Those stars should still be racing through space, about 10,000 light years away from their original orbits.”

Can any of this be proved? The answer is yes. Thanks to large scale surveys like the Sloan Digital Sky Survey, we should be able to pinpoint stars moving at a higher velocity than stars which haven’t been subjected to a similar interaction. If astronomers like Holley-Bockelmann and Bogdanovic look at the hard evidence, they are likely to discover a credible number of high velocity stars which will validate their Milky Way merger model.

Or are they just blowing bubbles?

NuSTAR Puts New Spin On Supermassive Black Holes

A supermassive black hole has been found in an unusual spot: an isolated region of space where only small, dim galaxies reside. Image credit: NASA/JPL-Caltech
A team of astronomers from South Africa have noticed a series of supermassive black holes in distant galaxies that are all spinning in the same direction. Credit: NASA/JPL-Caltech

Checking out the spin rate on a supermassive black hole is a great way for astronomers to test Einstein’s theory under extreme conditions – and take a close look at how intense gravity distorts the fabric of space-time. Now, imagine a monster … one that has a mass of about 2 million times that of our Sun, measures 2 million miles in diameter and rotating so fast that it’s nearly breaking the speed of light.

A fantasy? Not hardly. It’s a supermassive black hole located at the center of spiral galaxy NGC 1365 – and it is about to teach us a whole lot more about how black holes and galaxies mature.

What makes researchers so confident they have finally taken definitive calculations of such an incredible spin rate in a distant galaxy? Thanks to data taken by the Nuclear Spectroscopic Telescope Array, or NuSTAR, and the European Space Agency’s XMM-Newton X-ray satellites, the team of scientists has peered into the heart of NGC 1365 with x-ray eyes – taking note of the location of the event horizon – the edge of the spinning hole where surrounding space begins to be dragged into the mouth of the beast.

“We can trace matter as it swirls into a black hole using X-rays emitted from regions very close to the black hole,” said the coauthor of a new study, NuSTAR principal investigator Fiona Harrison of the California Institute of Technology in Pasadena. “The radiation we see is warped and distorted by the motions of particles and the black hole’s incredibly strong gravity.”

However, the studies didn’t stop there, they advanced to the inner edge to encompass the location of the accretion disk. Here is the “Innermost Stable Circular Orbit” – the proverbial point of no return. This region is directly related to a black hole’s spin rate. Because space-time is distorted in this area, some of it can get even closer to the ISCO before being pulled in. What makes the current data so compelling is to see deeper into the black hole through a broader range of x-rays, allowing astronomers to see beyond veiling clouds of dust which only confused past readings. These new findings show us it isn’t the dust that distorts the x-rays – but the crushing gravity.

Scientists measure the spin rates of supermassive black holes by spreading the X-ray light into different colors. Image credit: NASA/JPL-Caltech
Scientists measure the spin rates of supermassive black holes by spreading the X-ray light into different colors. Image credit: NASA/JPL-Caltech

“This is the first time anyone has accurately measured the spin of a supermassive black hole,” said lead author Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics (CfA) and INAF — Arcetri Observatory.

“If I could have added one instrument to XMM-Newton, it would have been a telescope like NuSTAR,” said Norbert Schartel, XMM-Newton Project Scientist at the European Space Astronomy Center in Madrid. “The high-energy X-rays provided an essential missing puzzle piece for solving this problem.”

Even though the central black hole in NGC 1365 is a monster now, it didn’t begin as one. Like all things, including the galaxy itself, it evolved with time. Over millions of years it gained in girth as it consumed stars and gas – possibly even merging with other black holes along the way.

“The black hole’s spin is a memory, a record, of the past history of the galaxy as a whole,” explained Risaliti.

“These monsters, with masses from millions to billions of times that of the sun, are formed as small seeds in the early universe and grow by swallowing stars and gas in their host galaxies, merging with other giant black holes when galaxies collide, or both,” said the study’s lead author, Guido Risaliti of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and the Italian National Institute for Astrophysics.

This new spin on black holes has shown us that a monster can emerge from “ordered accretion” – and not simply random multiple events. The team will continue their studies to see how factors other than black hole spin changes over time and continue to observe several other supermassive black holes with NuSTAR and XMM-Newton.

“This is hugely important to the field of black hole science,” said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington, D.C. “NASA and ESA telescopes tackled this problem together. In tandem with the lower-energy X-ray observations carried out with XMM-Newton, NuSTAR’s unprecedented capabilities for measuring the higher energy X-rays provided an essential, missing puzzle piece for unraveling this problem.”

Original Story Source: JPL/NASA News Release.

Pulsar Jackpot Scours Old Data for New Discoveries

Space Shuttle Atlantis passes behind the Parkes radio telescope after final undocking from the International Space Station in July 2011. (Image Copyright: John Sarkissian; used with permission).

Chalk another one up for Citizen Science.  Earlier this month, researchers announced the discovery of 24 new pulsars. To date, thousands of pulsars have been discovered, but what’s truly fascinating about this month’s discovery is that came from culling through old data using a new method.

A pulsar is a dense, highly magnetized, swiftly rotating remnant of a supernova explosion. Pulsars where first discovered by Jocelyn Bell Burnell and Antony Hewish in 1967. The discovery of a precisely timed radio beacon initially suggested to some that they were the product of an artificial intelligence. In fact, for a very brief time, pulsars were known as LGM’s, for “Little Green Men.” Today, we know that pulsars are the product of the natural death of massive stars.

The data set used for the discovery comes from the Parkes 64-metre radio observatory based out of New South Wales, Australia. The installation was the first to receive telemetry from the Apollo 11 astronauts on the Moon and was made famous in the movie The Dish.  The Parkes Multi-Beam Pulsar Survey (PMPS) was conducted in the late 1990’s, making thousands of 35-minute recordings across the plane of the Milky Way galaxy. This survey turned up over 800 pulsars and generated 4 terabytes of data. (Just think of how large 4 terabytes was in the 90’s!)

Artist's conception of a pulsar. (Credit: NASA/GSFC).
Artist’s conception of a pulsar. (Credit: NASA/GSFC).

The nature of these discoveries presented theoretical astrophysicists with a dilemma. Namely, the number of short period and binary pulsars was lower than expected. Clearly, there were more pulsars in the data waiting to be found.

Enter Citizen Science. Using a program known as Einstein@Home, researchers were able to sift though the recordings using innovative modeling techniques to tease out 24 new pulsars from the data.

“The method… is only possible with the computing resources provided by Einstein@Home” Benjamin Knispel of the Max Planck Institute for Gravitational Physics told the MIT Technology Review in a recent interview. The study utilized over 17,000 CPU core years to complete.

Einstein@Home screenshot. (Credit: LIGO Consortium).
Einstein@Home screenshot. (Credit: LIGO Consortium).

Einstein@Home is a program uniquely adapted to accomplish this feat. Begun in 2005, Einstein@Home is a distributed computing project which utilizes computing power while machines are idling to search through downloaded data packets. Similar to the original distributed computing program SETI@Home which searches for extraterrestrial signals, Einstein@Home culls through data from the LIGO (Laser Interferometer Gravitational Wave Observatory) looking for gravity waves. In 2009, the Einstein@Home survey was expanded to include radio astronomy data from the Arecibo radio telescope and later the Parkes observatory.

Among the discoveries were some rare finds. For example, PSR J1748-3009 Has the highest known dispersion measure of any millisecond pulsar (The dispersion measure is the density of free electrons observed moving towards the viewer). Another find, J1750-2531 is thought to belong to a class of intermediate-mass binary pulsars. 6 of the 24 pulsars discovered were part of binary systems.

These discoveries also have implications for the ongoing hunt for gravity waves by such projects as LIGO. Specifically, a through census of binary pulsars in the galaxy will give scientists a model for the predicted rate of binary pulsar mergers. Unlike radio surveys, LIGO seeks to detect these events via the copious amount of gravity waves such mergers should generate. Begun in 2002, LIGO consists of two gravity wave observatories, one in Hanford Washington and one in Livingston Louisiana just outside of Baton Rouge. Each LIGO detector consists of two 2 kilometre Fabry-Pérot arms in an “L” configuration which allow for ultra-precise measurements of a 200 watt laser beam shot through them.  Two detectors are required to pin-point the direction of an incoming gravity wave on the celestial sphere. You can see the orientation of the “L’s” on the display on the Einstein@Home screensaver. Two geographically separate detectors are also required to rule out local interference. A gravity wave from a galactic source would ripple straight through the Earth.

Arial view of LIGO Livingston. (Image credit: The LIGO Scientific Collaboration).
Arial view of LIGO Livingston. (Image credit: The LIGO Scientific Collaboration).

Such a movement would be tiny, on the order of 1/1,000th the diameter of a proton, unnoticed by all except the LIGO detectors. To date, LIGO has yet to detect gravity waves, although there have been some false alarms. Scientists regularly interject test signals into the data to see if system catches them. The lack of detection of gravity waves by LIGO has put some constraints on certain events. For example, LIGO reported a non-detection of gravity waves during the February 2007 short gamma-ray burst event GRB 070201. The event arrived from the direction of the Andromeda Galaxy, and thus was thought to have been relatively nearby in the universe. Such bursts are thought to be caused by neutron star and/or black holes mergers. The lack of detection by LIGO suggests a more distant event. LIGO should be able to detect a gravitational wave event out to 70 million light years, and Advanced LIGO (AdLIGO) is set to go online in 2014 and will increase its sensitivity tenfold.

The control room at LIGO Livingston. (Photo by Author).
The control room at LIGO Livingston. (Photo by Author).

Knowledge of where these potential pulsar mergers are by such discoveries as the Parkes radio survey will also give LIGO researchers clues of targets to focus on. “The search for pulsars isn’t easy, especially for these “quiet” ones that aren’t doing the equivalent of “screaming” for our attention,” Says LIGO Livingston Data Analysis and EPO Scientist Amber Stuver. The LIGO consortium developed the data analysis technique used by Einstein@Home. The direct detection of gravitational waves by LIGO or AdLIGO would be an announcement perhaps on par with CERN’s discovery of the Higgs Boson last year. This would also open up a whole new field of gravitational wave astronomy and perhaps give new stimulus to the European Space Agencies’ proposed Laser Interferometer Space Antenna (LISA) space-based gravity wave detector. Congrats to the team at Parkes on their discovery… perhaps we’ll have the first gravity wave detection announcement out of LIGO as well in years to come!

-Read the original paper on the discovery of 24 new pulsars here.

-Amber Stuver blogs about Einstein@Home & the spin-off applications of gravity wave technology at Living LIGO.

-Parkes radio telescope image is copyrighted and used with the permission of CSIRO Operations Scientist John Sarkissian.

-For a fascinating read on the hunt for gravity waves, check out Gravity’s Ghost.

 

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)
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.)
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.

Read more: Chandra Stares Deep Into the Heart of Sagittarius A*

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

New Research Sheds Light On Black Hole Growth

The black hole that has grown the most can be found in the Sombrero galaxy . The researchers estimate that this black hole has been swallowing the equivalent of one Sun every twenty years and is now over 500 million times as heavy as the Sun. ESO Public Image Release

In a new study led by University of Central Lancashire astronomer Dr. Victor Debattista, researchers are looking into the mystery of how black holes grow and evolve. For many years, astronomers surmised black holes took on mass when their host galaxies merged, but now new modeling techniques show that black holes in spiral galaxies are forced to take on mass.

“Recent Hubble Space Telescope (HST) observations have revealed that a majority of active galactic nuclei (AGN) are resident in isolated disk galaxies, contrary to the usual expectation that AGN are triggered by mergers.” says Debattista. “Here we develop a new test of the cosmic evolution of supermassive black holes (SMBHs) in disk galaxies by considering the local population of SMBHs. We show that substantial SMBH growth in spiral galaxies is required as disks assemble.”

Weighing in a range of one million to one billion times that of the Sun, the black holes located at the core of most galaxies would appear to be gaining at much quicker rates than expected. These are not just exceptions – more like rules. Even the Milky Way’s quiescent black hole might be gaining as much mass as the Sun every 3,000 years. Past observations have shown growth during collision events, when huge amounts of gas around the black hole become intensely hot and shine as an active galactic nucleus. This is a process which can be spotted as far back as the first formations in our Universe. However, these new simulations are giving insight into large scale growth without the need for violence.

“The X-ray-selected sample of moderate luminosity AGN consists of more than 50% disk galaxies, with ongoing mergers evident no more frequently than in nonactive galaxies.” explains the research team. “Some show that even heavily obscured quasars are hosted largely by disks, not by mergers. Studies of star-formation using Herschel find that the specific star formation rates of X-ray selected AGN hosts are no different from those of inactive galaxies, also indicating that AGN hosts are not undergoing fundamentally different behaviors”

These modeling techniques, combined with current observations done with the Hubble Space Telescope, give credence to the theory that black holes can gain significant mass even in “quiet” spiral galaxies. As a matter of fact, there is a strong possibility that AGNs present in some spiral galaxies may even outnumber galaxy mergers. To make this concept even more exciting, astronomers are anticipating an event later this year in our own galaxy – an event where a gas cloud near the Milky Way’s nucleus will encounter our own central black hole. According to predictions, our black hole may take on as much as 15 Earth masses in a period of 10 years from this cloud.

This concept of black hole growth isn’t entirely new, though. According to other research done with the Hubble Space Telescope and led by Dr. Stelios Kazantzidis of Ohio State University and Professor Frank C. van den Bosch of Yale University, they had previously pinpointed mass properties of black holes – making size predictions which utilized the speed of stars residing in the galaxies. In this instance, the team disproved previous assumptions that black holes were unable to grow while the host galaxy grew. Their comparison of spiral and elliptical galaxies “found there is no mismatch between how big their black holes are.” This means black holes would be gaining in mass – growing along at the same rate as the galaxy itself.

“These simulations show that it is no longer possible to argue that black holes in spiral galaxies do not grow efficiently. ” comments Debattista on this new research. ” Our simulations will allow us to refine our understanding of how black holes grew in different types of galaxies.”

Messier 106: Amateur and Professional Astronomers Join Together to Peer Into the Eyes of Creation

Traveling to distant galaxies may have interesting consequences. Credit: Hubble Release, Messier 106

Nearly four million light years away in the direction of the constellation of Canes Venatici, a visage of creation awaited to be revealed. Now, thanks to the teamwork of the astronomical image processors at the Space Telescope Science Institute in Baltimore, Maryland, and world-renowned astrophotographers Robert Gendler and Jay GaBany, we’re able to see combined Hubble Space Telescope data with ground-based telescope imaging. Let’s look deep into spiral galaxy, Messier 106.

This wasn’t an overnight imaging project. “A few months ago the Hubble Heritage Team contacted me and asked if I’d be interested in making a large format image of M106 from the available data on the Hubble Legacy Archive,” says Gendler. “I agreed and went to work downloading a large number of data sets from the HLA. I realized this would be a massive project. The image would be a mosaic of more than 30 panels and would incorporate both wideband and narrowband data sets.”

With the cooperation of Jay GaBany, they combined their own observations/images of this magnificent structure and compiled it with Hubble data – filling in areas where no data was available. The resulting image is a portrait of such depth and beauty that it’s almost like looking into the eyes of creation itself.

Be swept away…

If you’re drawn to the core of Messier 106, there’s good reason. It isn’t just an ordinary spiral galaxy, it’s one that has a peculiar jet flow which can be detected in radio and in H-alpha wavelengths. “Due to the special geometry of the galaxy, the jets emerge from the nuclear region through the galactic disk,” says Marita Krause (et al). “Also the distribution of molecular gas looks different from that in other spiral galaxies.” It is just this difference that makes NGC 4258 (M106) stand out a bit from the crowd and so worthy of further processing. According to new modeling techniques the “concentration of CO along the ridges is due to interaction of the rotating gas clouds with the jet’s magnetic field by ambipolar diffusion. This magnetic interaction is thought to increase the time the molecular clouds reside near the jet thus leading to the quasi-static CO ridge.”

Knowing those jets are present and the hunger to reveal them through imaging became the driving force for R. Jay GaBany. “Since the early 1960s, M106, also known as NGC 4258, has been known to exhibit an extra pair of arms, located between the spiral arms comprised of stars, dust and gas. But an explanation for their existence remained elusive until earlier in this decade,” says Jay. “My contribution to the image came from my 2010 image of M-106 that revealed the full extent of its amazing jets. My image include 22 hours of white light exposures through clear, red, blue and green filters plus and other 15 hours of imaging through a 6nm narrow band h-alpha filter.”

Messier 106 Courtesy of R. Jay GaBany
Messier 106 Courtesy of R. Jay GaBany

“Seen in the light emitted by hydrogen molecules when they become ionized, these arms display an artificial red hue to make them visible in the image I produced. The extra arms are now believed to be caused by high energy jets emanating from an active 40 million solar mass super-massive black hole menacing the galaxy’s center,” explains GaBany. “Because the jets are tilted at a low inclination they pierce the disk and surrounding halo of this galaxy. So, as the jets pass through regions of gas, they create an expanding cocoon of shock waves that heats the surrounding material causing it to release radiation in optical wavelengths. The curvature and fraying seen at their extremities represents previous trajectories of the jet due to past precession. Precession is a change in the orientation of the rotation axis of a spinning object. For example, the wobble of a spinning top.”

Yet, that’s not all. This low luminosity Seyfert II galaxy is also hosting a maser – its warped disk of water molecules discovered in 1994. Through radio observations, M106 became the first of its kind to show the exact location of the core of an AGN (active galactic nucleus). According to a study done by JR Herrnstein (et al): “NGC 4258 is an exceptional laboratory for the study of AGN accretion processes. The nuclear maser reveals details about the kinematics and structure of the accretion disk on subparsec scales and permits the determination of the central mass with great precision.”

And there is still more…

Deep inside lurks that known supermassive black hole – one that’s extremely active and produces bright microwave radiation. But, don’t stop there. Ordinarily a spiral galaxy has two arms, but M106 has double. These ethereal “extras” can be seen as faint ribbons of gas at optical wavelengths, but become solidified when viewed in x-ray and radio. Here the structure is formed in hot gas rather than stars. While this process was once a mystery to astronomers, new information suggests they may arise from the black hole activity, making them a unique artifact. What could cause it? These “extra arms” could be the result of the violent turbulence at the core – where gases are superheated and interact with their denser counterparts causing them to illuminate. At the perimeter of the galactic structure, the gases are more loose and the arching formation could be the product of the movement of jet activity.

“One goal I had early on was to feature the well known ‘anomalous arms’ of M106,” said Gendler. “This feature, peculiar to M106, is thought to arise from superheated gases, energized by accretion of matter into the galaxy’s massive black hole. The anomalous arms emit light in the visual spectrum around 656nm (hydrogen alpha) and I found a fair amount of hydrogen alpha data sets for the arms in the HLA.”

Gendler was responsible for all the image assembly and processing. “Assembling the image required over two months,” he said. “The quality of the data ranged from good to very poor. The central galaxy had sufficient color data but away from the center the Hubble data was incomplete and in some areas did not exist. I then decided to use ground based data from my own image and Jay GaBany’s image of M106 to fill in areas of missing or incomplete Hubble data. I also used ground based data to boost the signal of the outer areas of the galaxy as the Hubble data was sparse and of short exposure for the more remote areas of the galaxy.”

All in all, Messier 106 is a galaxy that deserves attention – attention and a loving touch given by two of the very best amateur astronomers and dedicated astrophotographers to be found.

Original News Source: HubbleSite Image Release.