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Image of the quasar host galaxy from the UC San Diego research team’s data. The distance to this quasar galaxy is ~9.3 billion light years. The four-color image shows findings from use of the Keck Observatory and ALMA. As seen from Keck Observatory, the green colors highlight the energetic gas across the galaxy that is being illuminated by the quasar. The blue color represents powerful winds blowing throughout the galaxy. The red-orange colors represent the cold molecular gas in the system as seen from ALMA. The supermassive black hole sits at the center of the bright red-orange circular area slightly below the middle of the image. Credit: A. VAYNER AND TEAM
Stars forming in galaxies appear to be influenced by the supermassive black hole at the center of the galaxy, but the mechanism of how that happens has not been clear to astronomers until now.
“Supermassive black holes are captivating,” says lead author Shelley Wright, a University of California San Diego Professor of Physics.
UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)
NIROSETI AT UCSC Lick Observatory, attached to the existing Nickel 1-meter telescope, developed at Dunlap Institute, U Toronto
“Understanding why and how galaxies are affected by their supermassive black holes is an outstanding puzzle in their formation, says Wright”
In a study published today in The Astrophysical Journal,
Wright, graduate student Andrey Vayner, and their colleagues examined the energetics surrounding the powerful winds generated by the bright, vigorous supermassive black hole (known as a “quasar”) at the center of the 3C 298 host galaxy, located approximately 9.3 billion light years away.
“We study supermassive black holes in the very early universe when they are actively growing by accreting massive amounts of gaseous material,” says Wright. “While black holes themselves do not emit light, the gaseous material they chew on is heated to extreme temperatures, making them the most luminous objects in the universe.”
The UC San Diego team’s research revealed that the winds blow out through the entire galaxy and impact the growth of stars.
“This is remarkable that the supermassive black hole is able to impact stars forming at such large distances,” says Wright.
Today, neighboring galaxies show that the galaxy mass is tightly correlated with the supermassive black hole mass. Wright’s and Vayner’s research indicates that 3C 298 does not fall within this normal scaling relationship between nearby galaxies and the supermassive black holes that lurk at their center. But, in the early universe, their study shows that the 3C 298 galaxy is 100 times less massive than it should be given its behemoth supermassive black hole mass.
This implies that the supermassive black hole mass is established well before the galaxy, and potentially the energetics from the quasar are capable of controlling the growth of the galaxy.
To conduct the study, the UC San Diego researchers utilized multiple state-of-the-art astronomical facilities. The first of these was Keck Observatory’s instrument OSIRIS (OH-Suppressing Infrared Imaging Spectrograph) and its advanced adaptive optics (AO) system.
Keck OSIRIS
An AO system allows ground-based telescopes to achieve higher quality images by correcting for the blurring caused by the Earth’s atmosphere. The resulting images are as good as those obtained from space.
The second major facility was the Atacama Large Millimeter/submillimeter Array, known as “ALMA,” an international observatory in Chile that is able to detect millimeter wavelengths using up to 66 antennae to achieve high-resolution images of the gas surrounding the quasar.
ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres
“The most enjoyable part of researching this galaxy has been putting together all the data from different wavelengths and techniques,” said Vayner. “Each new dataset that we obtained on this galaxy answered one question and helped us put some of the pieces of the puzzle together. However, at the same time, it created new questions about the nature of galaxy and supermassive black hole formation.”
Wright agreed, saying that the data sets were “tremendously gorgeous” from both Keck Observatory and ALMA, offering a wealth of new information about the universe.
These findings are the first results from a larger survey of distant quasars and their energetics’ impact on star formation and galaxy growth. Vayner and the team will continue developing results on more distant quasars using the new facilities and capabilities from Keck Observatory and ALMA.
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To advance the frontiers of astronomy and share our discoveries with the world.
The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.
Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
December 6, 2017 [Today in social media]
Joshua Sokol
Olena Shmahalo/Quanta Magazine
The two Carnegie Magellan telescopes: Baade (left) and Clay (right)
Astronomers have at least two gnawing questions about the first billion years of the universe, an era steeped in literal fog and figurative mystery. They want to know what burned the fog away: stars, supermassive black holes, or both in tandem? And how did those behemoth black holes grow so big in so little time?
Now the discovery of a supermassive black hole smack in the middle of this period is helping astronomers resolve both questions. “It’s a dream come true that all of these data are coming along,” said Avi Loeb, the chair of the astronomy department at Harvard University.
The black hole, announced today in the journal Nature, is the most distant ever found. It dates back to 690 million years after the Big Bang. Analysis of this object reveals that reionization, the process that defogged the universe like a hair dryer on a steamy bathroom mirror, was about half complete at that time.
First Stars and Reionization Era, Caltech
The researchers also show that the black hole already weighed a hard-to-explain 780 million times the mass of the sun.
A team led by Eduardo Bañados, an astronomer at the Carnegie Institution for Science in Pasadena, found the new black hole by searching through old data for objects with the right color to be ultradistant quasars — the visible signatures of supermassive black holes swallowing gas. The team went through a preliminary list of candidates, observing each in turn with a powerful telescope at Las Campanas Observatory in Chile.
Carnegie Institution for Science Las Campanas Observatory telescopes in the southern Atacama Desert of Chile approximately 100 kilometres (62 mi) northeast of the city of La Serena,near the southern end and over 2,500 m (8,200 ft) high.
On March 9, Bañados observed a faint dot in the southern sky for just 10 minutes. A glance at the raw, unprocessed data confirmed it was a quasar — not a nearer object masquerading as one — and that it was perhaps the oldest ever found. “That night I couldn’t even sleep,” he said.
Eduardo Bañados at the Las Campanas Observatory in Chile, where the new quasar was discovered. Courtesy of Eduardo Bañados. Baade and Clay in the background.
The new black hole’s mass, calculated after more observations, adds to an existing problem. Black holes grow when cosmic matter falls into them. But this process generates light and heat. At some point, the radiation released by material as it falls into the black hole carries out so much momentum that it blocks new gas from falling in and disrupts the flow. This tug-of-war creates an effective speed limit for black hole growth called the Eddington rate. If this black hole began as a star-size object and grew as fast as theoretically possible, it couldn’t have reached its estimated mass in time.
Other quasars share this kind of precocious heaviness, too. The second-farthest one known, reported on in 2011, tipped the scales at an estimated 2 billion solar masses after 770 million years of cosmic time.
These objects are too young to be so massive. “They’re rare, but they’re very much there, and we need to figure out how they form,” said Priyamvada Natarajan, an astrophysicist at Yale University who was not part of the research team. Theorists have spent years learning how to bulk up a black hole in computer models, she said. Recent work suggests that these black holes could have gone through episodic growth spurts during which they devoured gas well over the Eddington rate.
Bañados and colleagues explored another possibility: If you start at the new black hole’s current mass and rewind the tape, sucking away matter at the Eddington rate until you approach the Big Bang, you see it must have initially formed as an object heavier than 1,000 times the mass of the sun. In this approach, collapsing clouds in the early universe gave birth to overgrown baby black holes that weighed thousands or tens of thousands of solar masses. Yet this scenario requires exceptional conditions that would have allowed gas clouds to condense all together into a single object instead of splintering into many stars, as is typically the case.
Cosmic Dark Ages
Cosmic Dark Ages. ESO.
Even earlier in the early universe, before any stars or black holes existed, the chaotic scramble of naked protons and electrons came together to make hydrogen atoms. These neutral atoms then absorbed the bright ultraviolet light coming from the first stars. After hundreds of millions of years, young stars or quasars emitted enough light to strip the electrons back off these atoms, dissipating the cosmic fog like mist at dawn.
Lucy Reading-Ikkanda/Quanta Magazine
Astronomers have known that reionization was largely complete by around a billion years after the Big Bang.
Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation
At that time, only traces of neutral hydrogen remained. But the gas around the newly discovered quasar is about half neutral, half ionized, which indicates that, at least in this part of the universe, reionization was only half finished. “This is super interesting, to really map the epoch of reionization,” said Volker Bromm, an astrophysicist at the University of Texas.
When the light sources that powered reionization first switched on, they must have carved out the opaque cosmos like Swiss cheese.
Inflationary Universe. NASA/WMAP
But what these sources were, when it happened, and how patchy or homogeneous the process was are all debated. The new quasar shows that reionization took place relatively late. That scenario squares with what the known population of early galaxies and their stars could have done, without requiring astronomers to hunt for even earlier sources to accomplish it quicker, said study coauthor Bram Venemans of the Max Planck Institute for Astronomy in Heidelberg.
More data points may be on the way. For radio astronomers, who are gearing up to search for emissions from the neutral hydrogen itself, this discovery shows that they are looking in the right time period. “The good news is that there will be neutral hydrogen for them to see,” said Loeb. “We were not sure about that.”
The team also hopes to identify more quasars that date back to the same time period but in different parts of the early universe. Bañados believes that there are between 20 and 100 such very distant, very bright objects across the entire sky. The current discovery comes from his team’s searches in the southern sky; next year, they plan to begin searching in the northern sky as well.
“Let’s hope that pans out,” said Bromm. For years, he said, the baton has been handed off between different classes of objects that seem to give the best glimpses at early cosmic time, with recent attention often going to faraway galaxies or fleeting gamma-ray bursts. “People had almost given up on quasars,” he said.
Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.
Artist’s impression of a distant quasar sporting a relativistic jet. Could the radio-loudness of such a quasar depend on its central black hole’s spin? [ESO/M. Kornmesser]
A cloud of gas surrounds the distant quasar SDSS J102009.99+104002.7 in this image from ESO’s Very Large Telescope.
ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level
The name “quasar” is a shortening of “quasi-stellar radio source”, though we now know that only a small fraction of quasars are radio-loud. [ESO/Arrigoni Battaia et al.]
Some distant active galaxies are louder in radio wavelengths than others. A new study explores whether this difference could be due to how quickly the supermassive black holes at their centers are spinning.
Loud and Quiet Quasars
Quasars, the most luminous type of active galactic nuclei, are powered by the accretion of material onto the supermassive black holes located at the centers of the galaxies. These distant beasts tend to fall into two general categories:
1. radio-loud quasars, which host powerful relativistic radio jets and make up roughly 10% of the quasar population, and
2. radio-quiet quasars, which feature only weak core radio emission and make up the remaining 90% of quasars.
What causes this distinction in jet behavior? Many theories have been put forward, but today we’ll explore one potential factor in particular: the spin of the black hole.
Histogram of the [O III] equivalent width for radio-loud (solid red) vs. radio-quiet (dashed blue) quasars, for three different definitions of radio-loudness. [Adapted from Schulze et al. 2017]
In the spin paradigm, it’s postulated that the angular momentum from a black hole’s spin — which can be retrograde, prograde, or nonexistent — is what allows (or doesn’t allow) for the launch of relativistic jets. In this picture, radio-loud quasars should have rapidly spinning supermassive black holes at their centers, whereas radio-quiet quasars should host low-spin black holes.
A Tricky Measurement
Past studies examining the spin paradigm suggest that it doesn’t hold up — several radio-quiet quasars were found to host black holes with apparently high spin. But measuring black-hole spins is notoriously tricky, with each method relying on a number of inferences. It’s possible that the method used to infer the high spins of these radio-quiet quasars might not have yielded accurate results.
A team of scientists led by Andreas Schulze (National Astronomical Observatory of Japan) has now proposed an alternative approach to test the spin paradigm. Schulze and collaborators suggest using the strength of a particular emission line, [O III], to indirectly measure the black holes’ average radiative efficiency — i.e., how much of the energy of the mass accreting onto the black holes is converted into radiation. If the average efficiency for a sample of radio-loud quasars is different than that for a sample of radio-quiet quasars, this would mean a difference in black-hole spins for the two samples.
Counting Spin Back In
[O III] equivalent width for the radio-loud (solid red) and radio-quiet (dashed blue) samples as a function of redshift. [Schulze et al. 2017]
Using a sample of nearly 8,000 quasars identified in the Sloan Digital Sky Survey, the authors find that the [O III] line strength is enhanced by a factor of at least 1.5 in a radio-loud sample, compared to a radio-quiet sample matched in redshift, black-hole mass, and accretion rate.
SDSS Telescope at Apache Point Observatory, NM, USA, Altitude 2,788 meters (9,147 ft)
Schulze and collaborators argue that this suggests the black-hole spins of the radio-loud quasar population are systematically higher than those of the radio-quiet population.
The authors caution that, like other tactics used to learn about black-hole spins, their approach relies on a number of key assumptions — and their results certainly don’t mean that spin must be the only factor differentiating between radio-loud and radio-quiet quasars. The results do suggest, however, that we shouldn’t count spin out of the game: it may play an important role in determining the loudness of these distant accreting monsters.
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ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metresALMA
28 November, 2017
Valeria Foncea Rubens
Education & Public Outreach Officer (EPO)
Alonso de Córdova 3107
Vitacura 763-0355, Santiago – Chile
T: 56 2-224676258 / 97-5871963
At the center of our galaxy, in the immediate vicinity of its supermassive black hole, is a region wracked by powerful tidal forces and bathed in intense ultraviolet light and X-ray radiation. These harsh conditions, astronomers surmise, do not favor star formation, especially low-mass stars like our Sun. Surprisingly, new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) suggest otherwise.
ALMA has revealed the telltale signs of eleven low-mass stars forming perilously close — within three light-years — to the Milky Way’s supermassive black hole, known to astronomers as Sagittarius A* (Sgr A*).
SGR A* NASA’s Chandra X-Ray Observatory
At this distance, tidal forces driven by the supermassive black hole should be energetic enough to rip apart clouds of dust and gas before they can form stars.
The presence of these newly discovered protostars (the formative stage between a dense cloud of gas and a young, shining star) suggests that the conditions necessary to birth low-mass stars may exist even in one of the most turbulent regions of our galaxy and possibly in similar locales throughout the Universe.
Double-lobe feature produced by jets from newly forming star near the galactic center. ALMA discovered 11 of these telltale signs of star formation remarkably close to the supermassive black hole at the center of our galaxy.
Credit: ALMA (ESO/NAOJ/NRAO), Yusef-Zadeh et al.; B. Saxton (NRAO/AUI/NSF)
NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)
“Despite all odds, we see the best evidence yet that low-mass stars are forming startlingly close to the supermassive black hole at the center of the Milky Way,” said Farhad Yusef-Zadeh, an astronomer at Northwestern University in Evanston, Illinois, and lead author on the paper. “This is a genuinely surprising result and one that demonstrates just how robust star formation can be, even in the most unlikely of places.”
The ALMA data also suggest that these protostars are about 6,000 years old. “This is important because it is the earliest phase of star formation we have found in this highly hostile environment,” Yusef-Zadeh said.
The team of researchers identified these protostars by seeing the classic “double lobes” of material that bracket each of them, creating a cosmic hourglass-like shape of gas that signals the early stages of star formation. Molecules, like carbon monoxide (CO), in these lobes glow brightly in millimeter-wavelength light, which ALMA can observe with remarkable precision and sensitivity.
Infant stars, like those recently identified near the supermassive black hole at the center of our galaxy, are surrounded by a swirling disk of dust and gas. In this artist’s conception of infant solar system, the young star pulls material from its surroundings into rotating disk (right) and generates outflowing jets of material (left). Credit: Bill Saxton (NRAO/AUI/NSF)
Protostars form from interstellar clouds of dust and gas. Dense pockets of material in these clouds collapse under their own gravity and grow by accumulating more and more star-forming gas from their parent clouds. A portion of this infalling material, however, never makes it onto the surface of the star. Instead, it is ejected as a pair of high-velocity jets from the protostar’s north and south poles. Extremely turbulent environments, however, can disrupt the normal procession of material onto a protostar, while intense radiation – from massive nearby stars and supermassive black holes — can blast away the parent cloud, thwarting the formation of all but the most massive of stars.
The Milky Way’s galactic center, with its 4 million solar mass black hole, is located approximately 25,000 light-years from Earth in the direction of the constellation Sagittarius. Vast stores of interstellar dust obscure this region, hiding it from optical telescopes. Radio waves, including the millimeter and submillimeter light that ALMA sees, are able to penetrate this dust, giving radio astronomers a clearer picture of the dynamics and content of this hostile environment.
Prior ALMA observations of the region surrounding Sgr A* by Yusef-Zadeh and his team revealed multiple massive infant stars that are estimated to be about 6 million years old. These objects, known as proplyds, are common features in more placid star-forming regions, like the Orion Nebula.
Orion Nebula M. Robberto NASA ESA Space Telescope Science Institute Hubble
Though the galactic center is a challenging environment for star formation, it is possible for particularly dense cores of hydrogen gas to cross the necessary threshold and forge new stars, despite the extreme conditions.
The new ALMA observations, however, revealed something even more remarkable, signs that eleven low-mass protostars are forming within 1 parsec – a scant 3 light-years – of the galaxy’s central black hole. Yusef-Zadeh and his team used ALMA to confirm that the masses and momentum transfer rates – the ability of the protostar jets to plow through surrounding interstellar material – are consistent with young protostars found throughout the disk of our galaxy.
An ALMA image of the center of the Milky Way galaxy revealing 11 young protostars within about 3 light-years of our galaxy’s supermassive black hole. The lines indicate the direction of the bipolar lobes created by high-velocity jets from the protostars. The star indicates the location of Sagittarius A*, the 4 million solar mass supermassive black hole at the center of our galaxy.
Credit: ALMA (ESO/NAOJ/NRAO), Yusef-Zadeh et al.; B. Saxton (NRAO/AUI/NSF)
Additional Information
The research team was composed by F. Yusef-Zadeh[1], M. Wardle[2], D. Kunneriath[3], M. Royster[1], A. Wootten[3] & D. A. Roberts[1]
[1] Department of Physics and Astronomy Northwestern University, Evanston, IL 60208
[2] Dept of Physics and Astronomy, Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney NSW 2109, Australia
[3] National Radio Astronomy Observatory, Charlottesville, VA 22903 4Fort Worth Museum of Science and History, Fort Worth, TX 76107
ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
The idea of traveling back in time has long fascinated humans, such as in Back To The Future’s Delorean DMC-12. After decades of research, we may have hit upon a solution that’s physically possible. Image credit: Ed g2s of Wikimedia Commons.
And you don’t even need a Delorean at 88 MPH.
It’s one of the greatest tropes in movies, literature, and television shows: the idea that we could travel back in time to alter the past. From the time turner in Harry Potter to Back To The Future to Groundhog Day, traveling back in time provides us with the possibility of righting wrongs in our own past. To most people, it’s an idea that’s relegated to the realm of fiction, as every law of physics indicates that motion forward through time is an absolute necessity. Philosophically, there’s also a famous paradox that seems to indicate the absurdity of such a possibility: if traveling backwards through time were possible, you’d be able to go back and kill your grandfather before your parents were ever conceived, rendering your own existence impossible. For a long time, there seemed to be no way to go back. But thanks to some very interesting properties of space and time in Einstein’s General Relativity, traveling back in time may be possible after all.
An illustration of the early Universe as consisting of quantum foam, where quantum fluctuations are large, varied, and important on the smallest of scales. Positive and negative energy fluctuations can create minuscule, quantum wormholes. Image credit: NASA/CXC/M.Weiss.
The place to start is with the physical idea of a wormhole. In our known Universe, we have tiny, minuscule quantum fluctuations in the fabric of spacetime on the smallest of scales. These include energy fluctuations in both the positive and negative directions, often very close by one another. A very strong, dense, positive energy fluctuation would create curved space in one particular fashion, while a strong, dense, negative energy fluctuation would curve space in exactly the opposite fashion. If you connected these two curvature regions together, you could — for a brief instant — arrive at the notion of a quantum wormhole. If the wormhole lasted for long enough, you could even potentially transport a particle through it, allowing it to instantly disappear from one location in spacetime and reappear in another.
Exact mathematical plot of a Lorentzian wormhole. If one end of a wormhole is built out of positive mass/energy, while the other is built of negative mass/energy, the wormhole can become traversible. Image credit: Wikimedia Commons user Kes47.
If we want to scale that up, however, to allow something like a human being through, that’s going to take some work. While every known particle in our Universe has positive energy and either positive or zero mass, it’s eminently possible to have negative mass/energy particles in the framework of General Relativity. Sure, we haven’t discovered any yet, but according to all the rules of theoretical physics, there’s nothing forbidding it.
If this negative mass/energy matter exists, then creating both a supermassive black hole and the negative mass/energy counterpart to it, while then connecting them, should allow for a traversible wormhole. No matter how far apart you took these two connected objects from one another, if they had enough mass/energy — of both the positive and negative kind — this instantaneous connection would remain. All of that is great for instantaneous travel through space. But what about time? Here’s where the laws of special relativity come in.
A “light clock” will appear to run different for observers moving at different relative speeds, but this is due to the constancy of the speed of light. Einstein’s law of special relativity governs how these time and distance transformations take place, but it means that the stationary and the moving parties age at different rates. Image credit: John D. Norton, via http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_clocks_rods/.
If you travel close to the speed of light, you experience a phenomenon known as time dilation. Your motion through space and your motion through time are related by the speed of light: the greater your motion through space, the less your motion through time. Imagine you had a destination that was 40 light years away, and you were able to travel at incredibly high speeds: over 99.9% the speed of light. If you got into a spaceship and traveled very close to the speed of light towards that star, then stopped, turned around, and returned back to Earth, you’d find something odd.
Due to time dilation and length contraction, you might reach your destination in only a year, and then come back in just another year. But back on Earth, 82 years would have passed. Everyone you know would have aged tremendously. This is the standard way time travel physically works: it takes you into the future, with the amount of travel forward in time dependent only on your motion through space.
Is time travel possible? With a large enough wormhole, such as one created by a supermassive black hole connected to its negative mass/energy counterpart, it just might be. Image credit: Wikimedia Commons user Kjordand.
But if you construct a wormhole like we just described, the story changes. Imaging one end of the wormhole remains close to motionless, such as remaining close to Earth, while the other one goes off on a relativistic journey close to the speed of light. You then enter the rapidly-moving end of the wormhole after it’s been in motion for perhaps a year. What happens?
Well, a year isn’t the same for everyone, particularly if they’re moving through time and space differently! If we talk about the same speeds as we did earlier, the “in motion” end of the wormhole would have aged 40 years, but the “at rest” end would only have aged by 1 year. Step into the relativistic end of the wormhole, and you arrive back on Earth only one year after the wormhole was created, while you yourself may have had 40 years of time to pass.
If, 40 years ago, someone had created such a pair of entangled wormholes and sent them off on this journey, it would be possible to step into one of them today, in 2017, and wind up back in time at the mouth of the other one… back in 1978. The only issue is that you yourself couldn’t also have been at that location back in 1978; you needed to be with the other end of the wormhole, or traveling through space to try and catch up with it.
Warp travel, as envisioned for NASA. If you created a wormhole between two points in space, with one mouth moving relativistically relative to the other, observers at either traversible end would have aged by vastly different amounts. Image credit: NASA / Digital art by Les Bossinas (Cortez III Service Corp.), 1998.
Satisfyingly, we discover that this form of time travel also forbids the grandfather paradox! Even if the wormhole were created before your parents were conceived, there’s no way for you to exist at the other end of the wormhole early enough to go back and find your grandfather prior to that critical moment. The best you can do is to put your newborn father and mother on a ship to catch the other end of the wormhole, have them live, age, conceive you, and then send yourself back through the wormhole. You’ll be able to meet your grandfather when he’s still very young — perhaps even younger than you are now — but it will still, by necessity, occur at a moment in time after your parents were born.
A great many unusual things become possible in the Universe if negative mass/energy is real, abundant, and controllable, but traveling backwards in time might be the wildest one we’ve ever imagined. Owing to the oddities of both special and general relativity, time travel to the past might not be forbidden after all!
“Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan
31 March, 2017 [Appeared now in RSS]
Javier Méndez (Public Relations Officer)
outreach@ing.iac.es
Based on spectroscopic observations taken with the William Herschel Telescope (WHT) in 2015, astronomers from the Department of Physics and Astronomy at the University of Sheffield have found the first evidence for a stellar tidal disruption event (TDE) in a galaxy with a massive on-going starburst.
Until now, TDEs — in which stars are ripped apart by supermassive black holes in the nuclei of galaxies — had been found in surveys of many thousands of galaxies, and the rate deduced for such events was low: one event every 10,000 to 100,000 years per galaxy. However, the Sheffield team detected a TDE in repeat WHT spectroscopic observations of a sample of just 15 ultra-luminous infrared galaxies (ULIRGs) over a period of only 10 years. Since ULIRGs represent the peaks of major galaxy mergers, this suggests that the rate of TDEs is substantially enhanced in mergers.
Artist’s impression of the tidal disruption event in F01004-2237. Credits and copyright: Mark Garlick.
The team first observed the 15 ULIRGs in the sample with WHT/ISIS in 2005, during a project to study merger-induced star formation. However, when they observed the sample again in 2015 — this time to study the outflows driven by the active galactic nuclei (AGN) triggered in the mergers — they noticed that the nuclear spectrum of one galaxy (F01004-2237) appeared strikingly different. In particular, the object showed unusually strong and broad helium emission lines.
Comparison of the optical spectrum of F01004-2237 taken in September 2015 using the ISIS spectrograph on the WHT with that taken in September 2000 using the STIS spectrograph on the Hubble Space Telescope (HST). Note the detection of a broad component to the HeI 4686Å emission line in 2015 that is not visible in the Hβ and Hγ Balmer lines. ING.
NASA/ESA Hubble Telescope
Alerted to the possibility of an unusual transient event, the team then searched the Catalina Sky Survey database for evidence of variability, and discovered that F01004-2237 (z=0.117835) underwent a spectacular flare in its optical V-band light in 2010.
Catalina Sky Survey (CSS) light curves for F01004-2237 (solid blue points) and the other 14 ULIRGs in the spectroscopic sample (black dotted lines and red dashed line). Note that, whereas F01004-2237 has shown a substantial flare in its V-band brightness (ΔmV=0.45±0.02 mag) over the ~10 years of the survey, none of the other sources have shown similar flares. The data used are available from the CSS data release 2 website.
The particular combination of variability and post-flare spectrum observed in F01004-2237 is unlike any known supernova or AGN, but is characteristic of TDEs. According to Clive Tadhunter, who led the research: “The enhanced rate of TDEs in major galaxy mergers is likely to be due to a combination of the high stellar densities associated with the circum-nuclear starbursts, and the movement of the two supermassive black holes from the progenitor galaxies through these dense star fields as they merge together.”
The study, published in the journal Nature Astronomy, was supported by a grant from the UK Science and Technology Facilities Council.
Infrared image of the Milky Way galaxy. (SDSS Collaboration)
SDSS Telescope at Apache Point Observatory, NM, USA, Altitude2,788 meters (9,147 ft)
A research team led by Keivan Stassun, Stevenson Professor of Physics and Astronomy, will continue Vanderbilt’s contribution to one of the most successful international collaborations in astronomy and astrophysics in the past two decades as it embarks on the fifth generation of the Sloan Digital Sky Survey (SDSS-V) in 2020. Stassun currently chairs the executive committee of SDSS-IV. Vanderbilt has been a project partner since SDSS-III.
The Sloan Digital Sky Survey is responsible for creating the most detailed three-dimensional maps of the universe ever made, with deep multicolor images of one third of the sky, and characterizing the spectra, which provides information about elemental composition, of more than 3 million astronomical objects. The Alfred P. Sloan Foundation has announced that it will continue its support of the collaboration with a $16 million grant for SDSS-V.
“For more than 20 years, the Sloan Digital Sky Survey has defined excellence in astronomy,” said Paul L. Joskow, president of the Alfred P. Sloan Foundation. “SDSS-V continues that august tradition by combining cutting-edge research, international collaboration, technological innovation and cost-effective grassroots governance. The Sloan Foundation is proud to be a core supporter of SDSS-V.”
SDSS-V will shift the survey’s focus from broadly cosmological investigation into the structure and expansion of the universe toward a closer analysis of our nearest stars and galaxies. It will consist of three projects, each mapping different components of the universe: the Milky Way Mapper, the Black Hole Mapper and the Local Volume Mapper. The first mapper focuses on the formation of the Milky Way and its stars and planets. The second will study the formation, growth and ultimate sizes of the supermassive black holes found at the centers of galaxies. The Local Volume Mapper will create the first complete spectroscopic maps of several important nearby galaxies.
Stassun’s team will work on the Milky Way Mapper project, focusing particularly on the stars orbited by the Earth-like planets that will be tracked by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission. Stassun is a deputy investigator on that project as well, which will give his team unusually comprehensive insight into the nearby solar systems that may have the potential to harbor or sustain life.
NASA/TESS
“Between the TESS mission and SDSS-V, Vanderbilt is going to be at this world-leading nexus of a major space mission and a major international collaboration on Earth focused on finding new habitable planets around other stars and making detailed measurements of them,” Stassun said. “We’ll be finding other Earths with TESS and figuring out what those solar systems are made of with SDSS-V.”
Vanderbilt’s membership in SDSS-V gives Stassun’s team proprietary access to the project’s data products for a period of two years. This includes leadership opportunities for Vanderbilt postdoctoral scientists, including Jonathan Bird, Stevenson Postdoctoral Fellow, who helped to develop the Milky Way Mapper concept. He will serve as one of the project leads for the Milky Way Mapper.
“SDSS-V ushers in a new era of industrial-scale stellar spectroscopy,” Bird said. “The Milky Way Mapper will produce a fantastically comprehensive picture of the Milky Way that will enable diverse and exciting science, from where the oxygen that we breathe was formed and dispersed to how unique—or how ordinary—our galaxy may be in the cosmos.”
SDSS-V will also incorporate an educational effort designed to broaden the participation of underrepresented groups in the survey. The SDSS’ Faculty and Student Team (FAST) program is the first of its kind spearheaded by an astronomy collaboration. Led by Vanderbilt Associate Professor of Astrophysics Kelly Holley-Bockelmann, the FAST program focuses on building serious, long-term research relationships between faculty/student teams and SDSS partner institutions.
“We targeted faculty and their students at institutions with strong track records of serving underrepresented students. Building capacity at the faculty level magnifies the effort as the faculty ‘pay it forward’ to many students in the long-term,” said Holley-Bockelmann, who is also the Vanderbilt director of the Fisk-Vanderbilt Masters-to-Ph.D. Bridge Program. “I got to see firsthand how talented these FAST students are—so much so that we admitted them to the Bridge Program to get Ph.D.’s in astronomy!”
Following the proprietary period, in the tradition of previous Sloan Surveys, SDSS-V will continue to make its data publicly available in a format that is helpful to a broad range of users, from the youngest students to both amateur and professional astronomers.
In addition to the Sloan Foundation grant, SDSS-V currently has commitments of support from 18 institutions around the world, including the Carnegie Institution for Science, the Max Planck Institute for Astronomy, Max-Planck-Institute for Extraterrestrial Physics, University of Utah, the Israeli Centers of Research Excellence, the Kavli Institute for Astronomy and Astrophysics at Peking University, Harvard University, Ohio State University, Penn State University, Georgia State University, University of Wisconsin, Caltech, New Mexico State University, the Space Telescope Science Institute, University of Washington, Vanderbilt University, University of Warwick, Leibniz Institut für Astrophysik Potsdam, Katholieke Universiteit Leuven, Monash University and Yale University, with additional partnership agreements underway. Vanderbilt’s participation is made possible by financial support through the Stevenson endowment.
Commodore Cornelius Vanderbilt was in his 79th year when he decided to make the gift that founded Vanderbilt University in the spring of 1873.
The $1 million that he gave to endow and build the university was the commodore’s only major philanthropy. Methodist Bishop Holland N. McTyeire of Nashville, husband of Amelia Townsend who was a cousin of the commodore’s young second wife Frank Crawford, went to New York for medical treatment early in 1873 and spent time recovering in the Vanderbilt mansion. He won the commodore’s admiration and support for the project of building a university in the South that would “contribute to strengthening the ties which should exist between all sections of our common country.”
McTyeire chose the site for the campus, supervised the construction of buildings and personally planted many of the trees that today make Vanderbilt a national arboretum. At the outset, the university consisted of one Main Building (now Kirkland Hall), an astronomical observatory and houses for professors. Landon C. Garland was Vanderbilt’s first chancellor, serving from 1875 to 1893. He advised McTyeire in selecting the faculty, arranged the curriculum and set the policies of the university.
For the first 40 years of its existence, Vanderbilt was under the auspices of the Methodist Episcopal Church, South. The Vanderbilt Board of Trust severed its ties with the church in June 1914 as a result of a dispute with the bishops over who would appoint university trustees.
kirkland hallFrom the outset, Vanderbilt met two definitions of a university: It offered work in the liberal arts and sciences beyond the baccalaureate degree and it embraced several professional schools in addition to its college. James H. Kirkland, the longest serving chancellor in university history (1893-1937), followed Chancellor Garland. He guided Vanderbilt to rebuild after a fire in 1905 that consumed the main building, which was renamed in Kirkland’s honor, and all its contents. He also navigated the university through the separation from the Methodist Church. Notable advances in graduate studies were made under the third chancellor, Oliver Cromwell Carmichael (1937-46). He also created the Joint University Library, brought about by a coalition of Vanderbilt, Peabody College and Scarritt College.
Remarkable continuity has characterized the government of Vanderbilt. The original charter, issued in 1872, was amended in 1873 to make the legal name of the corporation “The Vanderbilt University.” The charter has not been altered since.
The university is self-governing under a Board of Trust that, since the beginning, has elected its own members and officers. The university’s general government is vested in the Board of Trust. The immediate government of the university is committed to the chancellor, who is elected by the Board of Trust.
The original Vanderbilt campus consisted of 75 acres. By 1960, the campus had spread to about 260 acres of land. When George Peabody College for Teachers merged with Vanderbilt in 1979, about 53 acres were added.
wyatt centerVanderbilt’s student enrollment tended to double itself each 25 years during the first century of the university’s history: 307 in the fall of 1875; 754 in 1900; 1,377 in 1925; 3,529 in 1950; 7,034 in 1975. In the fall of 1999 the enrollment was 10,127.
In the planning of Vanderbilt, the assumption seemed to be that it would be an all-male institution. Yet the board never enacted rules prohibiting women. At least one woman attended Vanderbilt classes every year from 1875 on. Most came to classes by courtesy of professors or as special or irregular (non-degree) students. From 1892 to 1901 women at Vanderbilt gained full legal equality except in one respect — access to dorms. In 1894 the faculty and board allowed women to compete for academic prizes. By 1897, four or five women entered with each freshman class. By 1913 the student body contained 78 women, or just more than 20 percent of the academic enrollment.
National recognition of the university’s status came in 1949 with election of Vanderbilt to membership in the select Association of American Universities. In the 1950s Vanderbilt began to outgrow its provincial roots and to measure its achievements by national standards under the leadership of Chancellor Harvie Branscomb. By its 90th anniversary in 1963, Vanderbilt for the first time ranked in the top 20 private universities in the United States.
Vanderbilt continued to excel in research, and the number of university buildings more than doubled under the leadership of Chancellors Alexander Heard (1963-1982) and Joe B. Wyatt (1982-2000), only the fifth and sixth chancellors in Vanderbilt’s long and distinguished history. Heard added three schools (Blair, the Owen Graduate School of Management and Peabody College) to the seven already existing and constructed three dozen buildings. During Wyatt’s tenure, Vanderbilt acquired or built one-third of the campus buildings and made great strides in diversity, volunteerism and technology.
The university grew and changed significantly under its seventh chancellor, Gordon Gee, who served from 2000 to 2007. Vanderbilt led the country in the rate of growth for academic research funding, which increased to more than $450 million and became one of the most selective undergraduate institutions in the country.
On March 1, 2008, Nicholas S. Zeppos was named Vanderbilt’s eighth chancellor after serving as interim chancellor beginning Aug. 1, 2007. Prior to that, he spent 2002-2008 as Vanderbilt’s provost, overseeing undergraduate, graduate and professional education programs as well as development, alumni relations and research efforts in liberal arts and sciences, engineering, music, education, business, law and divinity. He first came to Vanderbilt in 1987 as an assistant professor in the law school. In his first five years, Zeppos led the university through the most challenging economic times since the Great Depression, while continuing to attract the best students and faculty from across the country and around the world. Vanderbilt got through the economic crisis notably less scathed than many of its peers and began and remained committed to its much-praised enhanced financial aid policy for all undergraduates during the same timespan. The Martha Rivers Ingram Commons for first-year students opened in 2008 and College Halls, the next phase in the residential education system at Vanderbilt, is on track to open in the fall of 2014. During Zeppos’ first five years, Vanderbilt has drawn robust support from federal funding agencies, and the Medical Center entered into agreements with regional hospitals and health care systems in middle and east Tennessee that will bring Vanderbilt care to patients across the state.
studentsToday, Vanderbilt University is a private research university of about 6,500 undergraduates and 5,300 graduate and professional students. The university comprises 10 schools, a public policy center and The Freedom Forum First Amendment Center. Vanderbilt offers undergraduate programs in the liberal arts and sciences, engineering, music, education and human development as well as a full range of graduate and professional degrees. The university is consistently ranked as one of the nation’s top 20 universities by publications such as U.S. News & World Report, with several programs and disciplines ranking in the top 10.
Cutting-edge research and liberal arts, combined with strong ties to a distinguished medical center, creates an invigorating atmosphere where students tailor their education to meet their goals and researchers collaborate to solve complex questions affecting our health, culture and society.
Vanderbilt, an independent, privately supported university, and the separate, non-profit Vanderbilt University Medical Center share a respected name and enjoy close collaboration through education and research. Together, the number of people employed by these two organizations exceeds that of the largest private employer in the Middle Tennessee region.
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October 30, 2017
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
Elizabeth.landau@jpl.nasa.gov
This artist’s concept shows a black hole with an accretion disk — a flat structure of material orbiting the black hole – and a jet of hot gas, called plasma. Credit: NASA/JPL-Caltech
Black holes are famous for being ravenous eaters, but they do not eat everything that falls toward them. A small portion of material gets shot back out in powerful jets of hot gas, called plasma, that can wreak havoc on their surroundings. Along the way, this plasma somehow gets energized enough to strongly radiate light, forming two bright columns along the black hole’s axis of rotation. Scientists have long debated where and how this happens in the jet.
Astronomers have new clues to this mystery. Using NASA’s NuSTAR space telescope and a fast camera called ULTRACAM on the William Herschel Observatory in La Palma, Spain, scientists have been able to measure the distance that particles in jets travel before they “turn on” and become bright sources of light.
NASA NuSTAR X-ray telescope
ULTRACAM on the William Herschel Observatory in La Palma, Spain
ING 4 meter William Herschel Telescope at Roque de los Muchachos Observatory on La Palma in the Canary Islands, 2,396 m (7,861 ft)
This distance is called the “acceleration zone.” The study is published in the journal Nature Astronomy.
Scientists looked at two systems in the Milky Way called “X-ray binaries,” each consisting of a black hole feeding off of a normal star. They studied these systems at different points during periods of outburst — which is when the accretion disk — a flat structure of material orbiting the black hole — brightens because of material falling in.
One system, called V404 Cygni, had reached nearly peak brightness when scientists observed it in June 2015. At that time, it experienced the brightest outburst from an X-ray binary seen in the 21st century. The other, called GX 339-4,was less than 1 percent of its maximum expected brightness when it was observed. The star and black hole of GX 339-4 are much closer together than in the V404 Cygni system.
Despite their differences, the systems showed similar time delays – about one-tenth of a second — between when NuSTAR first detected X-ray light and ULTRACAM detected flares in visible light slightly later. That delay is less than the blink of an eye, but significant for the physics of black hole jets.
“One possibility is that the physics of the jet is not determined by the size of the disc, but instead by the speed, temperature and other properties of particles at the jet’s base,” said Poshak Gandhi, lead author of the study and astronomer at the University of Southampton, United Kingdom.
The best theory scientists have to explain these results is that the X-ray light originates from material very close to the black hole. Strong magnetic fields propel some of this material to high speeds along the jet. This results in particles colliding near light-speed, energizing the plasma until it begins to emit the stream of optical radiation caught by ULTRACAM.
Where in the jet does this occur? The measured delay between optical and X-ray light explains this. By multiplying this amount of time by the speed of the particles, which is nearly the speed of light, scientists determine the maximum distance traveled.
This expanse of about 19,000 miles (30,000 kilometers) represents the inner acceleration zone in the jet, where plasma feels the strongest acceleration and “turns on” by emitting light. That’s just under three times the diameter of Earth, but tiny in cosmic terms, especially considering the black hole in V404 Cygni weighs as much as 3 million Earths put together.
“Astronomers hope to refine models for jet powering mechanisms using the results of this study,” said Daniel Stern, study co-author and astronomer based at NASA’s Jet Propulsion Laboratory, Pasadena, California.
Making these measurements wasn’t easy. X-ray telescopes in space and optical telescopes on the ground have to look at the X-ray binaries at exactly the same time during outbursts for scientists to calculate the tiny delay between the telescopes’ detections. Such coordination requires complex planning between the observatory teams. In fact, coordination between NuSTAR and ULTRACAM was only possible for about an hour during the 2015 outburst, but that was enough to calculate the groundbreaking results about the acceleration zone.
The results also appear to connect with scientists’ understanding of supermassive black holes, much bigger than the ones in this study. In one supermassive system called BL Lacertae, weighing 200 million times the mass of our Sun, scientists have inferred time delays millions of times greater than what this study found. That means the size of the acceleration area of the jets is likely related to the mass of the black hole.
“We are excited because it looks as though we have found a characteristic yardstick related to the inner workings of jets, not only in stellar-mass black holes like V404 Cygni, but also in monster supermassive ones,” Gandhi said.
The next steps are to confirm this measured delay in observations of other X-ray binaries, and to develop a theory that can tie together jets in black holes of all sizes.
“Global ground and space telescopes working together were key to this discovery. But this is only a peek, and much remains to be learned. The future is really bright for understanding the extreme physics of black holes,” said Fiona Harrison, principal investigator of NuSTAR and professor of astronomy at Caltech in Pasadena.
NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. Caltech manages JPL for NASA.
Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.
Supermassive black holes a billion times heavier than the sun are too big to have formed conventionally. NASA Goddard Space Flight Center
A central mystery surrounds the supermassive black holes that haunt the cores of galaxies: How did they get so big so fast? Now, a new, computer simulation–based study suggests that these giants were formed and fed by massive clouds of gas sloshing around in the aftermath of the big bang.
“This really is a new pathway,” says Volker Bromm, an astrophysicist at the University of Texas in Austin who was not part of the research team. “But it’s not … the one and only pathway.”
Astronomers know that, when the universe was just a billion years old, some supermassive black holes were already a billion times heavier than the sun. That’s much too big for them to have been built up through the slow mergers of small black holes formed in the conventional way, from collapsed stars a few dozen times the mass of the sun. Instead, the prevailing idea is that these behemoths had a head start. They could have condensed directly out of seed clouds of hydrogen gas weighing tens of thousands of solar masses, and grown from there by gravitationally swallowing up more gas. But the list of plausible ways for these “direct-collapse” scenarios to happen is short, and each option requires a perfect storm of circumstances.
For theorists tinkering with computer models, the trouble lies in getting a massive amount of gas to pile up long enough to collapse all at once, into a vortex that feeds a nascent black hole like water down a sink drain. If any parts of the gas cloud cool down or clump up early, they will fragment and coalesce into stars instead. Once formed, radiation from the stars would blow away the rest of the gas cloud.
Computer models show how supersonic streams of gas coalesce around nuggets of dark matter—forming the seed of a supermassive black hole. Shingo Hirano
One option, pioneered by Bromm and others, is to bathe a gas cloud in ultraviolet light, perhaps from stars in a next-door galaxy, and keep it warm enough to resist clumping. But having a galaxy close enough to provide that service would be quite the coincidence.
The new study proposes a different origin. Both the early universe and the current one are composed of familiar matter like hydrogen, plus unseen clumps of dark matter.
Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.
Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et alDark Matter Particle Explorer ChinaDEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton MineLUX Dark matter Experiment at SURF, Lead, SD, USAADMX Axion Dark Matter Experiment, U Uashington
Today, these two components move in sync. But very early on, normal matter may have sloshed back and forth at supersonic speeds across a skeleton provided by colder, more sluggish dark matter. In the study, published today in Science, simulations show that where these surges were strong, and crossed the path of heavy clumps of dark matter, the gas resisted premature collapse into stars and instead flowed into the seed of a supermassive black hole. These scenarios would be rare, but would still roughly match the number of supermassive black holes seen today, says Shingo Hirano, an astrophysicist at the University of Texas and lead author of the study.
Priya Natarajan, an astrophysicist at Yale University, says the new simulation represents important computational progress. But because it would have taken place at a very distant, early moment in the history of the universe, it will be difficult to verify. “I think the mechanism itself in detail is not going to be testable,” she says. “We will never see the gas actually sloshing and falling in.”
But Bromm is more optimistic, especially if such direct-collapse black hole seeds also formed slightly later in the history of the universe. He, Natarajan, and other astronomers have been looking for these kinds baby black holes, hoping to confirm that they do, indeed, exist and then trying to work out their origins from the downstream consequences.
In 2016, they found several candidates, which seem to have formed through direct collapse and are now accreting matter from clouds of gas. And earlier this year, astronomers showed that the early, distant universe is missing the glow of x-ray light that would be expected from a multitude of small black holes—another sign favoring the sudden birth of big seeds that go on to be supermassive black holes. Bromm is hopeful that upcoming observations will provide more definite evidence, along with opportunities to evaluate the different origin theories. “We have these predictions, we have the signatures, and then we see what we find,” he says. “So the game is on.”
A galaxy cluster mini-halo as seen around the galaxy NGC 1275 in the radio, with its main structures labeled: the northern extension, the two eastern spurs, the concave edge to the south, the south-western edge and a plume of emission to the south-south-west. Astronomers used radio and X-ray data to conclude that mini-halos, rather than being simple structures resulting from turbulence, are actually the result of multiple processes. Gendron-Marsolais et al.
A mini-halo is a faint, diffuse region of radio emission that surrounds a cluster of galaxies. So far about thirty of these cluster mini-halos have been detected via their X-ray and radio emission, the result of radiation from electrons in the ionized gas, including one mini-halo in the nearby Perseus cluster of galaxies. These electrons are thought to arise from activity around a supermassive black hole at a galactic nucleus, which injects steams of particles into the intracluster medium and which also produces turbulence and shocks. One issue puzzling astronomers is that such electrons should rapidly lose their energy, faster than the time it takes for them to reach the mini-halo regions. Suggested solutions include processes in which turbulence reaccelerates the electrons, and in which cosmic rays generate new ones.
CfA astronomer Reinout van Weeren and his colleagues used the radio Karl G. Jansky Very Large Array (JVLA) to obtain the first detailed study of the structure of the mini-halo in Perseus, and to compare it with Chandra X-Ray images.
NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USANASA/Chandra Telescope
They find that the radio emission comes primarily from gas behind a cold front as would be expected if the gas is sloshing around within the cluster as particles are re-accelerated. They also detect unexpected, filamentary structures that seem to be associated with edges of X-ray features. The scientists conclude that mini-halos are not simply diffuse structures produced by a single process, but reflect a variety of structures and processes including turbulent re-acceleration of electrons, relativistic activity from the black hole jets, and also some magnetic field effects. Not least, the results demonstrate the sensitivity of the new JVLA and the need to obtain such sensitive images to understand the mini-halo phenomenon.
The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.
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