"It's a cosmic miracle," said Volker Bromm of The University of Texas at Austin, referring to the precise set of conditions present half a billion years after the Big Bang that allowed these behemoths to emerge. "It's the only time in the history of the universe when conditions are just right" for them to form.

Astronomers have discovered evidence for an unusual kind of black hole born extremely early in the universe. They showed that a recently discovered unusual source of intense radiation is likely powered by a "direct-collapse black hole," a type of object predicted by theorists more than a decade ago.

These direct-collapse black holes may be the solution to a long-standing puzzle in astronomy: How did supermassive black holes form in the early epochs of the universe? There is strong evidence for their existence, as they are needed to power the highly luminous quasars detected in the young universe. However, there are several problems that should prevent their formation, and the conventional growth process is much too slow.

Astronomers think they know how supermassive black holes weighing in at millions of suns grow in the heart of most galaxies in our present epoch. They get started from a "seed" black hole, created when an extremely massive star collapses. This seed black hole has the mass of about 100 suns. It pulls in gas from its surroundings, becoming much more massive, and eventually may merge with other seed black holes. This entire process is called accretion.

The accretion theory does not explain supermassive black holes in extremely distant -- and therefore young -- quasars. Visible to us despite its distance of billions of light-years, a quasar's incredible brightness comes from matter spiralling into a supermassive black hole, heating to millions of degrees, creating jets that shine as beacons across the universe.

These early galaxies may have contained the first generation of stars created after the Big Bang. And although these stars can collapse to form black holes, they don't work as early quasar seeds. There is no surrounding gas for the black hole to feed on. That gas has been blown away by winds from the hot, newly formed stars.

"Star formation is the enemy of forming massive black holes" in early galaxies, Bromm said. "Stars produce feedback that blows away the surrounding gas cloud."

For decades, astronomers have called this conundrum "the quasar seed problem." In 2003, Bromm and Loeb came up with a theoretical idea to get an early galaxy to form a supermassive seed black hole, by suppressing the otherwise prohibitive energy input from star formation. Astronomers later dubbed this process "direct collapse."

Begin with a "primordial cloud of hydrogen and helium, suffused in a sea of ultraviolet radiation," Bromm said. "You crunch this cloud in the gravitational field of a dark-matter halo. Normally, the cloud would be able to cool, and fragment to form stars. However, the ultraviolet photons keep the gas hot, thus suppressing any star formation. These are the desired, near-miraculous conditions: collapse without fragmentation! As the gas gets more and more compact, eventually you have the conditions for a massive black hole."

This set of cosmic conditions is exquisitely sensitive to the time period in the universe's history -- this process does not happen in galaxies today.

"The quasars observed in the early universe resemble giant babies in a delivery room full of normal infants," observed Avi Loeb of the HarvardSmithsonian Center for Astrophysics. "One is left wondering: what is special about the environment that nurtured these giant babies? Typically the cold gas reservoir in nearby galaxies like the Milky Way is consumed mostly by star formation.

"The theory we proposed when Bromm was my postdoc (at Harvard) suggested that the conditions in the first generation of galaxies were different," he said. "Instead of making many normal stars, these galaxies formed a single supermassive star at their centre that ended up collapsing to a seed black hole. Hence the gas in these environments was used to feed this seed black hole rather than make many normal stars."

Bromm and Loeb published their theory in 2003. "But it was all theoretical back then," Bromm said.

Fast forward a dozen years, and Bromm is now a professor at The University of Texas at Austin with postdocs and graduate students of his own. That's where Aaron Smith comes in.

Smith, Bromm, and Loeb had become interested in a galaxy called CR7, identified from a Hubble Space Telescope survey called COSMOS (in a paper led by Jorryt Matthee of Leiden University). Hubble spied CR7 at 1 billion years after the Big Bang.

David Sobral of the University of Lisbon had made follow-up observations of CR7 with some of the world's largest ground-based telescopes, including Keck and the VLT. These uncovered some extremely unusual features in the light signature coming from CR7. Specifically a certain hydrogen line in the spectrum, known as "Lyman-alpha," was several times brighter than expected. Remarkably, the spectrum also showed an unusually bright helium line.

"Whatever is driving this source is very hot -- hot enough to ionize helium," Smith said. Bromm agreed. "You need it to be 100,000 degrees Celsius -- very hot, a very hard UV source" for that to happen, he said.

These and other unusual features in the spectrum, such as the absence of any detected lines from elements heavier than helium (in astronomical parlance, "metals,") together with the source's distance -- and therefore its cosmic epoch -- meant that it could either be a cluster of primordial stars or a supermassive black hole likely formed by direct collapse.

Smith ran simulations for both scenarios using the Stampede supercomputer at UT Austin's Texas Advanced Computing Center.

"We developed a novel code," Smith said, explaining that his code modelled the system differently than previous simulations. "The old models were like a snapshot; this one is like a movie," he explained.

The type of modelling Smith used is called "radiation hydrodynamics," Bromm said. "It's the most expensive approach in terms of computer processing power." The new code paid off, though. The star cluster scenario "spectacularly failed," Smith said, while the direct collapse black hole model performed well.

Bromm said their work is about more than understanding the inner workings of one early galaxy.

"With CR7, we had one intriguing observation. We are trying to explain it, and to predict what future observations will find. We are trying to provide a comprehensive theoretical framework."

In addition to Smith, Bromm, and Loeb's work, NASA recently announced the discovery of two additional direct-collapse black hole candidates based on observations with the Chandra X-ray Observatory. It seems astronomers are "converging on this model," for solving the quasar seed problem, Smith said.

Time is running out for the galaxy NGC 3801, seen in the image at the top of the page combining light from across the spectrum, ranging from ultraviolet to radio. NASA's Galaxy Evolution Explorer and other instruments have helped catch the galaxy NGC 3801 in the act of destroying its cold, gaseous fuel for new stars. Astronomers believe this marks the beginning of its transition from a vigorous spiral galaxy to a quiescent elliptical galaxy whose star-forming days are long past.

Visible light from the Sloan Digital Sky Survey is seen in yellow shining from all of the galaxy's stars. Notice that NGC 3801 is starting to possess a broadly elliptical shape, the characteristic shape a galaxy assumes after forming from a merger of spiral galaxies. Some star formation is still taking place in NGC 3801, as shown in the ultraviolet by the Galaxy Evolution Explorer (colored blue), and in the dusty disk revealed in infrared light by NASA's Spitzer Space Telescope (red).

According to theory, that lingering star formation will soon be quenched by shock waves from two powerful jets shooting out of NGC 3801's central giant black hole. Radio emissions from those jets appear in this image in green. Like a cosmic leaf blower, the jets' expanding shock waves will blast away the remaining cool star-making gas in NGC 3801. The galaxy will become "red and dead," as astronomers say, full of old, red stars and lacking in any new stellar younglings.

The Daily Galaxy via RAS

Image credit top of page: NASA

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To grasp the blueprint of early planetary life, said Martin Rahm at Cornell. "We must think outside of green-blue, Earth-based biology: "We are used to our own conditions here on Earth. Our scientific experience is at room temperature and ambient conditions. Titan is a completely different beast." Although Earth and Titan both have flowing liquids, Titan's temperatures are very low, and there is no liquid water. "So if we think in biological terms, we're probably going to be at a dead end."

NASA's Cassini and Huygen's missions have provided a wealth of data about chemical elements found on Saturn's moon Titan, and Cornell scientists have uncovered a chemical trail that suggests prebiotic conditions may exist there.

Titan, Saturn's largest moon, features terrain with Earthlike attributes such as lakes, rivers and seas, although filled with liquid methane and ethane instead of water. Its dense atmosphere - a yellow haze - brims with nitrogen and methane. When sunlight hits this toxic atmosphere, the reaction produces hydrogen cyanide - a possible prebiotic chemical key.

"This paper is a starting point, as we are looking for prebiotic chemistry in conditions other than Earth's," said Martin Rahm, postdoctoral researcher in chemistry and lead author of the new study, "Polymorphism and Electronic Structure of Polyimine and Its Potential Significance for Prebiotic Chemistry on Titan," published in the Proceedings of the National Academy of Sciences, July 4.

Hydrogen cyanide is an organic chemical that can react with itself or with other molecules - forming long chains, or polymers, one of which is called polyimine. The chemical is flexible, which helps mobility under very cold conditions, and it can absorb the sun's energy and become a possible catalyst for life.

"Polyimine can exist as different structures, and they may be able to accomplish remarkable things at low temperatures, especially under Titan's conditions," said Rahm, who works in the lab of Roald Hoffmann, winner of the 1981 Nobel Prize in chemistry and Cornell's Frank H.T. Rhodes Professor of Humane Letters Emeritus. Rahm and the paper's other scientists consulted with Hoffmann on this work.

"We need to continue to examine this, to understand how the chemistry evolves over time. We see this as a preparation for further exploration," said Rahm. "If future observations could show there is prebiotic chemistry in a place like Titan, it would be a major breakthrough. This paper is indicating that prerequisites for processes leading to a different kind of life could exist on Titan, but this only the first step."

The Daily Galaxy via Cornell University

The Daily Galaxy via ESA

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The British writer Martin Amis once said we are about five Einsteins away from explaining the universe's existence. We took a step closer this past January, when an ancient signal from deep space verified that gravitational waves and black holes exist and opens a window on unknown mysteries of the cosmos. "It is by far the most powerful explosion humans have ever detected except for the big bang." said Caltech's Kip Thorne. "With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the dark side of the universe—objects and phenomena that are made from warped spacetime."

“This is not just the detection of gravitational waves," said David Reitze, Executive Director of the LIGO Laboratory. "What's really exciting is what comes next. Four hundred years ago, Galileo turned a telescope to the sky and opened the era of modern observational astronomy. I think we're doing something equally important here today. I think we're opening the window of gravitational astronomy.”

“This is just the beginning,” said Gabriela González of aLIGO. “Now that we know binary black holes are there, we'll begin listening to the universe.” Evidence of “ripples in spacetime” detected by the LIGO Scientific Collaboration marks the dawn of gravitational wave astronomy, say astrophysicists. The gravitational waves were generated when two black holes merged 1.3 billion years ago.

“It tells us something about the power of the human mind to understand nature at its deepest level," said cosmologist Neil Turok, Director of Perimeter Institute, one old the world's leading experts on the cosmological constant and a cyclic model of the universe.

“This was truly a scientific moon shot, and we did it,” said Reitze.

In the early hours of September 14, 2015, during an engineering test a few days before the official search was to begin, aLIGO's two detectors recorded a very characteristic signal made by both facilities of the Laser Interferometer Gravitational-Wave Observatory (LIGO) in Washington and Louisiana simultaneously. After numerous consistency checks, the resulting 5-sigma discovery was published.

The measured gravitational waves match those expected from two large black holes merging after a death spiral in a distant galaxy, with the resulting new black hole momentarily vibrating in a rapid ringdown. A phenomenon predicted by Einstein, the historic discovery confirms a cornerstone of humanity's understanding of gravity and basic physics. It is also the most direct detection of black holes ever.

BHmerger_LIGO_3600 (1)

The illustration above depicts the two merging black holes with the signal strength of the two detectors over 0.3 seconds superimposed across the bottom. Expected future detections by Advanced LIGO and other gravitational wave detectors may not only confirm the spectacular nature of this measurement but hold tremendous promise of giving humanity a new way to see and explore our universe.

“It was exactly what you would expect from Einstein's general relativity from two black holes spiralling and merging together,” said Reitze. “It took months of careful checking and rechecking to make sure what we saw was something that was a gravitational wave. We've convinced ourselves that's the case.”

Gravitational waves are ripples in the fabric of spacetime, created when two massive objects such as black holes or neutron stars hurtle around each other at extremely high speeds and collide. First put forward 100 years ago as a consequence of Albert Einstein's theory of general relativity, they have challenged theorists and experimentalists alike as one of the few elements of the theory that had not been experimentally proven. Until now.

LIGO, a system of two identical interferometers constructed to detect the tiny vibrations of passing gravitational waves, was conceived and built by MIT and Caltech researchers, funded by the US National Science Foundation.

The original LIGO experiment ran from 2002 to 2010 as a proof of concept. After significant upgrades to the detectors in Louisiana and Washington, Advanced LIGO did its first observation run in September 2015.

The first detection, at the Louisiana observatory, had a peak value of 10-21 meters. “For four kilometers [the length of the LIGO detector], that's a tiny, tiny fraction of a proton diameter. That's incredibly tiny,” said González. “We know it's real, because seven milliseconds later, we saw the same thing in the Hanford detector. This is it. This is how we know we have gravitational waves.”

The signals exactly match what Einsteinian gravitation predicts for the merger of two black holes. The signals also indicate the wave carried three solar masses of energy. The signal is so strong, the researchers reported in a paper published in Physical Review Letters, that it exceeds the “five sigma” standard of statistical significance physicists use to claim a discovery.

“The LIGO measurement is a spectacular confirmation of not just one, but two of the key predictions of Einstein's theory of gravity: the existence of gravitational waves and black holes,” Turok said. “Einstein developed his theory based on clues from experiment and prior theories, but even more on a remarkable intuition that gravitation is due to the bending of spacetime. A full century later, we're seeing his predictions verified with exquisite precision."

Even more than verifying Einstein, LIGO's detection of gravitational waves provides science with a new tool with which to potentially answer many more basic questions.

And it might lead researchers to the next great scientific theory, Perimeter researcher Luis Lehner said during the “Ripple Effects” panel hosted by the Perimeter Institute following the LIGO announcement. “When we can get more and more data, we might be able to see departures [from what is expected], and that may guide us in what replaces relativity,” he said.

As more gravitational wave detectors come online in the next few years, scientists will be able to glean increasingly rich information about the universe around us. “That will give us a very important network that will allow us to ... reduce serendipity from astronomy, at least for some sources,” Lehner said.

For many scientists, the most exciting prospect is that gravitational wave astronomy could enable researchers to probe the “dark” universe: objects and forces that don't absorb, reflect, or emit light, yet make up 96 percent of the universe.

Perimeter Associate Faculty member Avery Broderick said this is a seismic shift in astronomy, which has been studying the light side of the universe for 10,000 years.

“When we get this new window on the universe, history and experience has shown us that we find something totally different, something totally unexpected. This has happened over and over again in astronomy, where we've opened up windows in the X-ray and the radio, and we see a totally different universe,” Broderick said.

“I would be shocked if we don't see the same thing when we look with gravitational eyes, and see the gravitational wave universe as totally different. This is going to be absolutely critical to understanding how the dark universe and the light universe fit together.”

Perimeter cosmologist Latham Boyle is also excited about the unknowns that gravitational waves could now reveal. As he explained during the Perimeter panel, there was a span of decades between the discovery of radio waves and their use in astronomy.

“For 40 or 50 years, nobody built radio telescopes,” Boyle said. “Finally, when they did, there was a flood of all kinds of crazy discoveries. [There was] the cosmic microwave background radiation, which is kind of a cosmic selfie, then they discovered these things called pulsars, and they discovered quasars.

“They discovered all this stuff that people would have called you crazy if you'd suggested it before. As soon as you turned it on, it was out there. It's just a historical fact that often you see wilder stuff. That's one of the most exciting things for me.”

The Daily Galaxy via Caltech and The Perimeter Institute

Image credit: Binary black hole wikimedia.org/wikipedia/commons

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Since its detection in 2014, the brown dwarf known as WISE 0855 has fascinated astronomers. Only 7.2 light-years from Earth, it is the coldest known object outside of our solar system and is just barely visible at infrared wavelengths with the largest ground-based telescopes. A team led by astronomers at UC Santa Cruz has succeeded in obtaining an infrared spectrum of WISE 0855 using the Gemini North telescope in Hawaii, providing the first details of the object's composition and chemistry. Among the findings is strong evidence for the existence of clouds of water or water ice, the first such clouds detected outside of our solar system.

"We would expect an object that cold to have water clouds, and this is the best evidence that it does," said Andrew Skemer, assistant professor of astronomy and astrophysics at UC Santa Cruz. Skemer is first author of a paper on the new findings to be published in Astrophysical Journal Letters and currently available online.

A brown dwarf is essentially a failed star, having formed the way stars do through the gravitational collapse of a cloud of gas and dust, but without gaining enough mass to spark the nuclear fusion reactions that make stars shine. With about five times the mass of Jupiter, WISE 0855 resembles that gas giant planet in many respects. Its temperature is about 250 degrees Kelvin, or minus 10 degrees Fahrenheit, making it nearly as cold as Jupiter, which is 130 degrees Kelvin.

"WISE 0855 is our first opportunity to study an extrasolar planetary-mass object that is nearly as cold as our own gas giants," Skemer said.

Previous observations of the brown dwarf, published in 2014, provided tentative indications of water clouds based on very limited photometric data. Skemer, a coauthor of the earlier paper, said obtaining a spectrum (which separates the light from an object into its component wavelengths) is the only way to detect an object's molecular composition.

WISE 0855 is too faint for conventional spectroscopy at optical or near-infrared wavelengths, but thermal emission from the deep atmosphere at wavelengths in a narrow window around 5 microns offered an opportunity where spectroscopy would be "challenging but not impossible," he said.

The team used the Gemini-North telescope in Hawaii and the Gemini Near Infrared Spectrograph to observe WISE 0855 over 13 nights for a total of about 14 hours.

"It's five times fainter than any other object detected with ground-based spectroscopy at this wavelength," Skemer said. "Now that we have a spectrum, we can really start thinking about what's going on in this object. Our spectrum shows that WISE 0855 is dominated by water vapor and clouds, with an overall appearance that is strikingly similar to Jupiter."

The researchers developed atmospheric models of the equilibrium chemistry for a brown dwarf at 250 degrees Kelvin and calculated the resulting spectra under different assumptions, including cloudy and cloud-free models. The models predicted a spectrum dominated by features resulting from water vapor, and the cloudy model yielded the best fit to the features in the spectrum of WISE 0855.

Comparing the brown dwarf to Jupiter, the team found that their spectra are strikingly similar with respect to water absorption features. One significant difference is the abundance of phosphine in Jupiter's atmosphere. Phosphine forms in the hot interior of the planet and reacts to form other compounds in the cooler outer atmosphere, so its appearance in the spectrum is evidence of turbulent mixing in Jupiter's atmosphere. The absence of a strong phosphine signal in the spectrum of WISE 0855 implies that it has a less turbulent atmosphere.

"The spectrum allows us to investigate dynamical and chemical properties that have long been studied in Jupiter's atmosphere, but this time on an extrasolar world," Skemer said.

The Daily Galaxy via University of California Santa Cruz