Black Holes Archives

April 22, 2009December 24, 2015 by Nancy Atkinson

Dark Matter, Dark Energy; Now There’s “Dark Gulping”

The HST WFPC2 image of gravitational lensing in the galaxy cluster Abell 2218, indicating the presence of large amount of dark matter (credit Andrew Fruchter at STScI).

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For all you dark matter and dark energy fans out there, now there’s another new “dark” to add to the list. It’s called “dark gulping,” and it involves a process which may explain how supermassive black holes were able to form in the early universe. Astronomers from the University College of London (UCL) propose that dark gulping occurred when there were gravitational interactions between the invisible halo of dark matter in a cluster of galaxies and the gas embedded in the dark matter halo. This occurred when the Universe was less than a billion years old. They found that the interactions cause the dark matter to form a compact central mass, which can be gravitationally unstable, and collapse. The fast dynamical collapse is the dark gulping.

Dr. Curtis Saxton and Professor Kinwah Wu, both of UCL’s Mullard Space Science Laboratory, developed a model to study the process. They say that the dark gulping would have happened very rapidly, without a trace of electro-magnetic radiation being emitted.

There are several theories for how supermassive black holes form. One possibility is that a single large gas cloud collapses. Another is that a black hole formed by the collapse of a giant star swallows up enormous amounts of matter. Still another possibility is that a cluster of small black holes merge together. However, all these options take many millions of years and are at odds with recent observations that suggest that black holes were present when the Universe was less than a billion years old. Dark gulping may provide a solution to how the slowness of gas accretion was circumvented, enabling the rapid emergence of giant black holes. The affected dark mass in the compact core is compatible with the scale of supermassive black holes in galaxies today.

Dark matter appears to gravitationally dominate the dynamics of galaxies and galaxy clusters. However, there is still a great deal of conjecture about origin, properties and distribution of dark particles. While it appears that dark matter doesn’t interact with light, it does interacts with ordinary matter via gravity. “Previous studies have ignored the interaction between gas and the dark matter,” said Saxton, “but, by factoring it into our model, we’ve achieved a much more realistic picture that fits better with observations and may also have gained some insight into the presence of early supermassive black holes.”?

According to the model, the development of a compact mass at the core is inevitable. Cooling by the gas causes it to flow gently in towards the center. The gas can be up to 10 million degrees at the outskirts of the halos, which are few million light years in diameter, with a cooler zone towards the core, which surrounds a warmer interior a few thousand light years across. The gas doesn’t cool indefinitely, but reaches a minimum temperature, which fits well with X-ray observations of galaxy clusters.

The model also investigates how many dimensions the dark particles move in, as these determine the rate at which the dark halo expands and absorbs and emits heat, and ultimately affect the distribution of dark mass the system.

“In the context of our model, the observed core sizes of galaxy cluster halos and the observed range of giant black hole masses imply that dark matter particles have between seven and ten degrees of freedom,”?said Saxton. ?”With more than six, the inner region of the dark matter approaches the threshold of gravitational instability, opening up the possibility of dark gulping taking place.?

The findings have been published in the Monthly Notices of the Royal Astronomical Society.

Source: RAS

April 22, 2009April 26, 2016 by Anne Minard

Black Hole Jets Pack One, Two Punch in Radio, Gamma Rays

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Compact, ultrabright jets at supermassive black holes in active galaxies were already known to pack an impressive punch in radio waves. And now, an international team of scientists says they’re kicking out high-energy gamma rays too.

Distant galaxies host the super massive black holes, which are billions of times heavier than our Sun but are confined to a region no larger than our solar system. The rapidly rotating black holes attract stars, gas and dust, creating huge magnetic fields. The magnetic forces can trap some of the infalling gas and focus it into narrow jets that flow away from the core of the galaxy at velocities approaching the speed of light.

Theoreticians and observers alike have been puzzling for decades about the nature and composition of these energetic radio-emitting jets, and if they also radiate in other parts of the electromagnetic spectrum.

Some hints were provided by the EGRET instrument on the Compton Gamma Ray Observatory telescope in the late 1990s and more recent discoveries of X-ray emission made by the Chandra Observatory.

Now, astronomers from Germany, the United States and Spain have paired observations of the bright gamma-ray sky by NASA’s orbiting Fermi Gamma-ray Space Telescope with those from the ground-based Very Long Baseline Array radio telescope in the United States to observe the material expelled with enormous speeds away from the black holes in the heart of very remote galaxies. These ejections take the form of narrow jets in radio telescope images, and appear to be producing the gamma-rays detected by Fermi.

“These objects are amazing: finally we know for sure that the fastest, most compact, and brightest jets that we see with radio telescopes are the ones which are able to kick the light up to the highest energies,” said Yuri Kovalev, Humboldt Fellow and scientist at the Max Planck Institute for Radio Astronomy.

The gamma-ray bright sources are now shown to be brighter, more compact and faster at light year scales than the gamma-ray quiet sources.

Fermi, formerly known as GLAST, has been operational since the summer of 2008. The telescope records an image of the whole sky every few hours to explore the most extreme environments in the universe, including pulsars and gamma-ray bursts, as well as black holes in galactic nuclei. Gamma-ray observations alone are not enough to discern the exact location of the radiation, however. The VLBA serves as a magnifying glass for zeroing in on the most energetic processes in the distant universe. Many objects found by Fermi to be extreme in gamma-rays are emitting strong bursts of radio emission at the same time.

The Very Long Baseline Array is a continent-wide system of ten radio telescope antennas, ranging from Hawaii in the west to the U.S. Virgin Islands in the east. Dedicated in 1993, the VLBA is operated by the U.S. National Radio Astronomy Observatory and is designed to monitor the brightest objects in the Universe at the highest available resolution in astronomy.

The work for astronomers does not stop here: the team has concluded that the region of the jet closest to the black hole is undoubtedly the place where the gamma-ray and the radio bursts of light originate in about the same time. However, some parts of the puzzle have yet to be resolved, they say: some bright gamma-ray sources in the sky appear to have no radio or optical counterpart — their nature is still completely unknown.

Source: Max-Planck Institute. The findings are being reported in two publications in the May 1, 2009 issue of Astrophysical Journal Letters (here and here).

Links:

Very Long Baseline Array
VLBA Monitoring of AGN Jets: The MOJAVE Project
Fermi Gamma-ray Space Telescope LAT Group

April 22, 2009December 24, 2015 by Nancy Atkinson

Oldest and Most Distant Water in the Universe Detected

The image is made from HST data and shows the four lensed images of the dusty red quasar, connected by a gravitational arc of the quasar host galaxy. The lensing galaxy is seen in the centre, between the four lensed images. Credit: John McKean/HST Archive data

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Astronomers have found the most distant signs of water in the Universe to date. The water vapor is thought to be contained in a maser, a jet ejected from a supermassive black hole at the center of a galaxy, named MG J0414+0534. The radiation from the water maser was emitted when the Universe was only about 2.5 billion years old, a fifth of its current age. “The radiation that we detected has taken 11.1 billion years to reach the Earth, said Dr. John McKean of the Netherlands Institute for Radio Astronomy (ASTRON). “However, because the Universe has expanded like an inflating balloon in that time, stretching out the distances between points, the galaxy in which the water was detected is about 19.8 billion light years away.”

The water emission is seen as a maser, where molecules in the gas amplify and emit beams of microwave radiation in much the same way as a laser emits beams of light. The faint signal is only detectable by using a technique called gravitational lensing, where the gravity of a massive galaxy in the foreground acts as a cosmic telescope, bending and magnifying light from the distant galaxy to make a clover-leaf pattern of four images of MG J0414+0534. The water maser was only detectable in the brightest two of these images.

“We have been observing the water maser every month since the detection and seen a steady signal with no apparent change in the velocity of the water vapor in the data we’ve obtained so far, McKean said. “This backs up our prediction that the water is found in the jet from the supermassive black hole, rather than the rotating disc of gas that surrounds it.”

Detection of the earliest and most distant water. CREDIT: Milde Science Communication, STScI, CFHT, J.-C. Cuillandre, Coelum.

Although since the initial discovery the team has looked at five more systems that have not had water masers, they believe that it is likely that there are many more similar systems in the early Universe. Surveys of nearby galaxies have found that only about 5% have powerful water masers associated with active galactic nuclei. In addition, studies show that very powerful water masers are extremely rare compared to their less luminous counterparts. The water maser in MG J0414+0534 is about 10,000 times the luminosity of the Sun, which means that if water masers were equally rare in the early Universe, the chances of making this discovery would be improbably slight.

“We found a signal from a really powerful water maser in the first system that we looked at using the gravitational lensing technique. From what we know about the abundance of water masers locally, we could calculate the probability of finding a water maser as powerful as the one in MG J0414+0534 to be one in a million from a single observation. This means that the abundance of powerful water masers must be much higher in the distant Universe than found locally because I’m sure we are just not that lucky!” said Dr McKean.

The discovery of the water maser was made by a team led by Dr. Violette Impellizzeri using the 100-metre Effelsberg radio telescope in Germany during July to September 2007. The discovery was confirmed by observations with the Expanded Very Large Array in the USA in September and October 2007. The team included Alan Roy, Christian Henkel and Andreas Brunthaler, from the Max Planck Institute for Radio Astronomy, Paola Castangia from Cagliari Observatory and Olaf Wucknitz from the Argelander Institute for Astronomy at Bonn University. The findings were published in Nature in December 2008.

The team is now analyzing high-resolution data to find out how close the water maser lies to the supermassive black hole, which will give them new insights into the structure at the center of active galaxies in the early Universe.

“This detection of water in the early Universe may mean that there is a higher abundance of dust and gas around the super-massive black hole at these epochs, or it may be because the black holes are more active, leading to the emission of more powerful jets that can stimulate the emission of water masers. We certainly know that the water vapour must be very hot and dense for us to observe a maser, so right now we are trying to establish what mechanism caused the gas to be so dense,” said Dr McKean.

McKean presented the team’s findings at the European Week of Astronomy and Space Science in the UK this week.

Source: RAS

March 31, 2009December 24, 2015 by Nancy Atkinson

What Would the View Be Like From Within a Black Hole?

The view from within a black hole? Credit: University of Colorado

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If you fell into a black hole, would you be engulfed in darkness? Could you see out beyond the event horizon? Are there wormholes inside black holes? Do black holes give birth to baby universes? Believe it or not, these questions may have been answered. Andrew Hamilton from the University of Colorado and Gavin Polhemus have created a video showing what falling into a Schwarzschild black hole might look like to the person falling in. The two researchers warn that based on our experience in the 3D world, we might imagine that falling through the horizon would be like falling through any other surface. However, they say, it’s not. And likely, a person falling into the black hole would be able to see outside of the event horizon.

“When an observer outside the horizon observes the horizon of a black hole,” the researchers say, “they are actually observing the outgoing horizon. When they subsequently fall through the horizon, they do not fall through the horizon they were looking at, the outgoing horizon; rather, they fall through the ingoing horizon, which was invisible to them until they actually passed through it. Once inside the horizon, the infaller sees both outgoing and ingoing horizons.”

As you might expect, this work has created a lot of interest, and the servers hosting the videos has already crashed once, but now has been put on a new server. Watch several different videos. along with written commentary here.

While this work is great fun to watch and delve into, it also has great scientific merit. Calculating what the universe looks like from inside a black hole is an important exercise because it forces physicists to examine how the laws of physics behave at a breaking point. For example, near the singularity, the observer’s view in the horizontal plane is highly blueshifted, but all directions other than horizontal appear highly redshifted.

Also, the principle of locality is severely tested inside a black hole. This is the idea that a point in space can only be influenced by its immediate surroundings. But when space is infinitely stretched, as physicists think it is at the heart of a black hole, the concept of “immediate surroundings” doesn’t make sense. So the concept of locality begins to lose its meaning too.

And that provides an interesting “thought laboratory” in which physicists can ask how ideas such as quantum mechanics and relativity might break down.

It also provides some other entertaining results. For example, space is so heavily curved inside a black hole that ordinary binocular vision would be no good for determining distances, says Hamilton. But trinoculars might work.

Read the paper here.

Sources: Technology Review Blog

March 25, 2009March 24, 2012 by Anne Minard

Don’t ‘Supermassive’ Me: Black Holes Regulate Their Own Mass

Stellar-mass black holes, between 7 and 25 times the Sun’s mass, are called “micro-quasars” when they spawn powerful jets of particles and radiation, miniature versions of those seen in quasars. Stellar-mass black holes are on the small end of the scale opposite supermassive black holes, including those in quasars, which weigh millions to billions of times the mass of the Sun.

The micro-quasars’ jets may be part of a secret weapon for keeping their petite figures, according to new research.

Continue reading “Don’t ‘Supermassive’ Me: Black Holes Regulate Their Own Mass”

March 4, 2009December 24, 2015 by Anne Minard

Astronomers Detect Two Black Holes in a Cosmic Dance

Artist's conception of the binary supermassive black hole system. Credit P. Marenfeld, NOAO

Paired black holes are theorized to be common, but have escaped detection — until now.

Astronomers Todd Boroson and Tod Lauer, from the National Optical Astronomy Observatory (NOAO) in Tucson, Arizona, have found what looks like two massive black holes orbiting each other in the center of one galaxy. Their discovery appears in this week’s issue of Nature.

Astronomers have long suspected that most large galaxies harbor black holes at their center, and that most galaxies have undergone some kind of merger in their lifetime. But while binary black hole systems should be common, they have proved hard to find. Boroson and Lauer believe they’ve found a galaxy that contains two black holes, which orbit each other every 100 years or so. They appear to be separated by only 1/10 of a parsec, a tenth of the distance from Earth to the nearest star.

After a galaxy forms, it is likely that a massive black hole can also form at its center. Since many galaxies are found in cluster of galaxies, individual galaxies can collide with each other as they orbit in the cluster. The mystery is what happens to these central black holes when galaxies collide and ultimately merge together. Theory predicts that they will orbit each other and eventually merge into an even larger black hole.

“Previous work has identified potential examples of black holes on their way to merging, but the case presented by Boroson and Lauer is special because the pairing is tighter and the evidence much stronger,” wrote Jon Miller, a University of Michigan astronomer, in an accompanying editorial.

The material falling into a black hole emits light in narrow wavelength regions, forming emission lines which can be seen when the light is dispersed into a spectrum. The emission lines carry the information about the speed and direction of the black hole and the material falling into it. If two black holes are present, they would orbit each other before merging and would have a characteristic dual signature in their emission lines. This signature has now been found.

The smaller black hole has a mass 20 million times that of the sun; the larger one is 50 times bigger, as determined by the their orbital velocities.

Boroson and Lauer used data from the Sloan Digital Sky Survey, a 2.5-meter (8-foot) diameter telescope at Apache Point in southern New Mexico to look for this characteristic dual black hole signature among 17,500 quasars.

Quasars are the most luminous versions of the general class of objects known as active galaxies, which can be a hundred times brighter than our Milky Way galaxy, and powered by the accretion of material into supermassive black holes in their nuclei. Astronomers have found more than 100,000 quasars.

Boroson and Lauer had to eliminate the possibility that they were seeing two galaxies, each with its own black hole, superimposed on each other. To try to eliminate this superposition possibility, they determined that the quasars were at the same red-shift determined distance and that there was a signature of only one host galaxy.

“The double set of broad emission lines is pretty conclusive evidence of two black holes,” Boroson said. “If in fact this were a chance superposition, one of the objects must be quite peculiar. One nice thing about this binary black hole system is that we predict that we will see observable velocity changes within a few years at most. We can test our explanation that the binary black hole system is embedded in a galaxy that is itself the result of a merger of two smaller galaxies, each of which contained one of the two black holes.”

LEAD IMAGE CAPTION (more): Artist’s conception of the binary supermassive black hole system. Each black hole is surrounded by a disk of material gradually spiraling into its grasp, releasing radiation from x-rays to radio waves. The two black holes complete an orbit around their center of mass every 100 years, traveling with a relative velocity of 6000 kilometers (3,728 miles) per second. (Credit P. Marenfeld, NOAO)

Source: NOAO

March 1, 2009December 24, 2015 by Ian O'Neill

Is There a Mysterious Black Hole Constant?

Space-time warping as a small black hole orbits a larger black hole (Don Davis)

[/caption]If you found yourself in the unfortunate situation of orbiting a black hole, you may be in for a rather dizzying and unpredictable ride. If the black hole is spinning, it will flatten out under centrifugal forces, much like the Earth bulges slightly at the equator, but the black hole’s bulge will be radically greater. As the shape of the black hole changes, so does its gravitational profile.

As you are not orbiting a spherical black hole, you can no longer expect to have a boring, predictable orbit; your orbit will become wild and chaotic, seemingly random. However, it would appear that there is an underlying constant to the mayhem, and what’s more, it seems this constant has also been observed in a more pedestrian system: a three-body Newtonian system. So what’s the link? Physicists aren’t quite sure…

When a massive star exhausts its fuel, it may collapse in on itself to create a black hole (after some exciting supernova action). The angular momentum of the original star is expected to be preserved, producing a rapidly spinning black hole. If the black hole “has no hair” (i.e. it has no electrical charge), the gravitational field solely depends on its mass and spin. If there is deformation due to the spin, the gravitational field changes, sending any orbiting body (like a neutron star) on a crazy roller-coaster ride.

In a new paper by Clifford Will of Washington University in St. Louis, the excited physicist describes the scenario. “The orbits go wild — they gyrate and spin, they’re incredibly complex. It’s fantastic,” Will says.

However, physicist Brandon Carter discovered a mathematical constant back in 1968, showing these apparently chaotic orbits are predictable, and that it even applies to orbits around extremely warped space-time. “Black holes have this extra constant that restores the regularity of the orbits,” comments Saul Teukolsky of Cornell University. “It’s a mystery. Every other situation where we have these extra constants, we have symmetry. But there’s no symmetry for an orbiting black hole — that’s why it is regarded as a miracle.”

Quite simply, physicists have no idea why the Carter constant could arise from the General Relativity description of a spinning black hole. Now, to make the problem even more perplexing, Will carried out a classical (Newtonian) 2-body simulation with a third body orbiting. Again, the same constant appeared. It would appear that there is something special about the predictability of an orbit around this black hole configuration.

Teukolsky, who worked on similar problems for his Ph.D. in 1970, remains baffled by these results. However, Will continues to investigate the problem, by including a term for black hole frame dragging. In this situation, the spinning black hole will drag space-time around it, “creases” (or ripples) in space time being pulled with the direction of spin. In this case, the Carter constant disappears, only to return when higher order terms are added to the equations.

This all means one of two things. Either it is simply an artefact in the mathematics, a curiosity that will eventually be rooted out of the equations. However, there is a tantalising possibility that we are seeing a characteristic of exotic rotating black holes, where the configuration of the surrounding fabric of space-time can allow a predictable orbit to come out of the apparent chaos…

Source: Science News

Here’s an article about black body radiation.

February 9, 2009December 24, 2015 by Nancy Atkinson

NuSTAR Will Ride Pegasus XL to Orbit

Artist concept of NuSTAR in orbit. Credit: NASA/JPL

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NASA announced today Orbital Sciences Corporation will launch the first high energy X-ray telescope, NuSTAR (Nuclear Spectroscopic Telescope Array) on board a Pegasus XL rocket. Orbital has also been the prime industrial contractor for building NuSTAR itself. The spacecraft will fly in 2011, launching from the Ronald Reagan Ballistic Missile Defense Test Site located at the Pacific Ocean’s Kwajalein Atoll. NuSTAR is the first satellite to fly a focusing X-ray telescope in space for energies in the 8-80 keV range, searching for black holes and supernova remnants.

NuSTAR was canceled in February 2006, but NASA restarted the program in September 2007, after Alan Stern took over as associate administrator for the Science Mission Directorate NASA. “NuSTAR has more than 500 times the sensitivity of previous instruments that detect black holes,” Stern said in 2007. “It’s a great opportunity for us to explore an important astronomical frontier.”

NuSTAR will conduct a census for black holes, map radioactive material in young supernovae remnants, and study the origins of cosmic rays and the extreme physics around collapsed stars.

A Pegasus rocket in flight. Credit: Orbital Science Corp.

The Pegasus is one of the most reliable launch system for the deployment of small satellites weighing up to 1,000 pounds into low-Earth orbit. Its patented air-launch system, where the rocket is launched from beneath Orbital’s “Stargazer” L-1011 carrier aircraft over the ocean, reduces cost and provides customers with unparalleled flexibility to operate from virtually anywhere on Earth. The Pegasus rocket has been flying since 1990, and has successfully conducted over 54 space launch missions.

The total cost of the NuSTAR launch services is approximately $36 million dollars. This estimated cost includes the task ordered launch service for a Pegasus XL rocket, plus additional services under other contracts for payload processing, launch vehicle integration, and tracking, data and telemetry support.

Source: NASA

January 28, 2009December 24, 2015 by Nancy Atkinson

A Disturbance in the Force in Centaurus A

Centaurus A. Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

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There are some interesting dynamics going on with Centaurus A, an elliptical galaxy about 13 million light-years away. This is a very active and luminous region of space and a great disturbance is going on as another spiral galaxy is trying to get in on the action by merging with Centaurus A. But astronomers now have new insight on what causing all the ruckus: a supermassive black hole at the core of Centaurus A. Jets and lobes emanating from the central black hole have been imaged at submillimeter wavelengths for the first time by using the 12-meter Atacama Pathfinder Experiment (APEX) telescope in Chile. By using a combination of visible and X-ray wavelengths, astronomers were able to produce this striking new image. Help me APEX, you are our only hope!

Centaurus A (NGC 5128) is one of our closest galactic neighbors, and is located in the southern constellation of Centaurus. The supermassive black hole is the source of the force: strong radio and X-ray emissions. Visible in the image is a dust ring encircling the giant galaxy, and the fast-moving radio jets ejected from the galaxy center. In submillimeter light, the heat glow from the central dust disc can be seen and also the emission from the central radio source.

APEX was also able to discern – for the first time in the submillimeter – the inner radio lobes north and south of the disc. Measurements of this emission, which occurs when fast-moving electrons spiral around the lines of a magnetic field, reveal that the material in the jet is travelling at approximately half the speed of light. In the X-ray emission, we see the jets emerging from the centre of Centaurus A and, to the lower right of the galaxy, the glow where the expanding lobe collides with the surrounding gas, creating a shockwave.

Zoom 13 Million Light-years to See Heart of Active Galaxy

Galaxy NGC 253 is shown here as observed with the WFI instrument, while the insert shows a close-up of the central parts as observed with the NACO instrument on ESO's Very Large Telescope and the ACS on the NASA/ESA Hubble Space Telescope. Credit: ESO

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Using data from the Very Large Telescope’s powerful near-infrared eyes, astronomers have created a movie that takes you across 13 million light-years to galaxy NGC 253, an active galaxy filled with young, massive and dusty stellar nurseries. “We now think that these are probably very active nurseries that contain many stars bursting from their dusty cocoons,” says Jose Antonio Acosta-Pulido, a member of the team from Instituto de Astrofísica de Canarias in Spain. NGC 253 is known as a starburst galaxy, after its very intense star formation activity. Each bright region could contain as many as one hundred thousand young, massive stars. And in the center of this galaxy appears a strikingly familiar sight: a virtual twin of our own Milky Way’s supermassive black hole.

Watch the movie. (For different viewing options, click here).

The astronomers used NACO, a sharp-eyed adaptive optics instrument on the VLT to study the fine detail in NGC 253, one of the brightest and dustiest spiral galaxies in the sky. Adaptive Optics (AO) corrects for the blurring effect introduced by the Earth’s atmosphere. This turbulence causes the stars to twinkle in a way that delights poets, but frustrates astronomers, since it smears out the images. With AO in action the telescope can produce images that are as sharp as is theoretically possible, as if the telescope were in space.

NACO revealed features in the galaxy that were only 11 light-years across. “Our observations provide us with so much spatially resolved detail that we can, for the first time, compare them with the finest radio maps for this galaxy — maps that have existed for more than a decade,” says Juan Antonio Fernández-Ontiveros, the lead author of the paper reporting the results.

Close-up of the central regions of the starburst galaxy NGC 253. Credit: ESO

Astronomers identified 37 distinct bright regions packed into a tiny region at the core of the galaxy, comprising just one percent of the galaxy’s total size. This is three times more than seen previously. The astronomers combined their NACO images with data from the infrared instrument on VLT, the VISIR, as well as with images from the NASA/ESA Hubble Space Telescope and radio observations made by the Very Large Array and the Very Large Baseline Interferometer. Combining these observations, taken in different wavelength regimes, provided a clue to the nature of these regions.

In looking at all the data together, astronomers concluded that the center of NGC 253 hosts a scaled-up version of Sagittarius A*, the bright radio source that lies at the core of the Milky Way and which we know harbors a massive black hole. “We have thus discovered what could be a twin of our Galaxy’s Centre,” says co-author Almudena Prieto.

Source: ESO