Discovery Nearly Doubles Known Quasars From The Ancient Universe

Quasars are supermassive black holes that sit at the center of enormous galaxies, accreting matter. They shine so brightly that they are often referred to as beacons and are among the most-distant objects in the universe that we can currently study. New work from a team led by Carnegie’s Eduardo Bañados has discovered 63 new quasars from when the universe was only a billion years old.

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This is the largest sample of such distant quasars presented in a single scientific article, almost doubling the number of ancient quasars previously known. The findings will be published by The Astrophysical Journal Supplement Series.

“Quasars are among the brightest objects and they literally illuminate our knowledge of the early universe,” Bañados said.

But until now, the population of known ancient quasars was fairly small, so scientists’ ability to glean information from them was limited. One of the main challenges is finding these distant quasars, which are extremely rare. Scientists have searched for them for decades, but the effort is comparable to finding a needle in a haystack.

The quasars discovered by Bañados and his team will provide valuable information from the first billion years after the Big Bang, which is a period of great interest to astronomers.

Why?

The universe was created in the Big Bang and hot matter exploded everywhere. But then it cooled off enough for the first protons and electrons to form and then to coalesce into hydrogen atoms, which resulted in a dark universe for a long time. It wasn’t until these atomic nuclei formed larger structures that light was able to shine once again in the universe. This happened when gravity condensed the matter and eventually formed the first sources of illumination, which might have included quasars.

There is still a lot about this era when the universe’s lights were turned back on that science doesn’t understand. But having more examples of ancient quasars will help experts to figure out what happened in those first billion years after the Big Bang.

“The formation and evolution of the earliest light sources and structures in the universe is one of the greatest mysteries in astronomy,” Bañados said. “Very bright quasars such as the 63 discovered in this study are the best tools for helping us probe the early universe. But until now, conclusive results have been limited by the very small sample size of ancient quasars.”

The coming years will see a great improvement in what we know about the early universe thanks to these discoveries.

Ripples In Fabric Of Space-time? Hundreds Of Undiscovered Black Holes

New research by the University of Surrey published today in the journal Monthly Notices of the Royal Astronomical Society has shone light on a globular cluster of stars that could host several hundred black holes, a phenomenon that until recently was thought impossible.

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Globular clusters are spherical collections of stars which orbit around a galactic centre such as our Milky-way galaxy. Using advanced computer simulations, the team at the University of Surrey were able to see the un-see-able by mapping a globular cluster known as NGC 6101, from which the existence of black holes within the system was deduced. These black holes are a few times larger than the Sun, and form in the gravitational collapse of massive stars at the end of their lives. It was previously thought that these black holes would almost all be expelled from their parent cluster due to the effects of supernova explosion, during the death of a star.

“Due to their nature, black holes are impossible to see with a telescope, because no photons can escape,” explained lead author Miklos Peuten of the University of Surrey. “In order to find them we look for their gravitational effect on their surroundings. Using observations and simulations we are able to spot the distinctive clues to their whereabouts and therefore effectively ‘see’ the un-seeable.”

It is only as recently as 2013 that astrophysicists found individual black holes in globular clusters via rare phenomena in which a companion star donates material to the black hole. This work, which was supported by the European Research Council (ERC), has shown that in NGC 6101 there could be several hundred black holes, overturning old theories as to how black holes form.

Co-author Professor Mark Gieles, University of Surrey continued, “Our work is intended to help answer fundamental questions related to dynamics of stars and black holes, and the recently observed gravitational waves. These are emitted when two black holes merge, and if our interpretation is right, the cores of some globular clusters may be where black hole mergers take place.”

The researchers chose to map this particular ancient globular cluster due to its recently found distinctive makeup, which suggested that it could be different to other clusters. Compared to other globular clusters NGC 6101 appears dynamically young in contrast to the ages of the individual stars. Also the cluster appears inflated, with the core being under-populated by observable stars.

Using computer simulation, the team recreated every individual star and black hole in the cluster and their behaviour. Over the whole lifetime of thirteen billion years the simulation demonstrated how NGC 6101 has evolved. It was possible to see the effects of large numbers of black holes on the visible stars, and to reproduce what was observed for NGC6101. From this, the researchers showed that the unexplainable dynamical apparent youth is an effect of the large black hole population.

“This research is exciting as we were able to theoretically observe the spectacle of an entire population of black holes using computer simulations. The results show that globular clusters like NGC 6101, which were always considered boring are in fact the most interesting ones, possibly each harbouring hundreds of black holes. This will help us to find more black holes in other globular clusters in the Universe. ” concluded Peuten.

Loneliest Young Star Seen By Spitzer And WISE

Alone on the cosmic road, far from any known celestial object, a young, independent star is going through a tremendous growth spurt.

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The unusual object, called CX330, was first detected as a source of X-ray light in 2009 by NASA’s Chandra X-Ray Observatory while it was surveying the bulge in the central region of the Milky Way. Further observations indicated that this object was emitting optical light as well. With only these clues, scientists had no idea what this object was.

But when Chris Britt, postdoctoral researcher at Texas Tech University in Lubbock, and colleagues were examining infrared images of the same area taken with NASA’s Wide-field Infrared Survey Explorer (WISE), they realized this object has a lot of warm dust around it, which must have been heated by an outburst.

Comparing WISE data from 2010 with Spitzer Space Telescope data from 2007, researchers determined that CX330 is likely a young star that had been outbursting for several years. In fact, in that three-year period its brightness had increased by a few hundred times.

Astronomers looked at data about the object from a variety of other observatories, including the ground-based SOAR, Magellan, and Gemini telescopes. They also used the large telescope surveys VVV and the OGLE-IV to measure the intensity of light emitted from CX330. By combining all of these different perspectives on the object, a clearer picture emerged.

“We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere,” said Britt, lead author of a study on CX330 recently published in the Monthly Notices of the Royal Astronomical Society.

The lone star’s behavior has similarities to FU Orionis, a young outbursting star that had an initial three-month outburst in 1936-7. But CX330 is more compact, hotter and likely more massive than the FU Orionis-like objects known. The more isolated star launches faster “jets,” or outflows of material that slam into the gas and dust around it.

“The disk has probably heated to the point where the gas in the disk has become ionized, leading to a rapid increase in how fast the material falls onto the star,” said Thomas Maccarone, study co-author and associate professor at Texas Tech.

Most puzzling to astronomers, FU Orionis and the rare objects like it—there are only about 10 of them—are located in star-forming regions. Young stars usually form and feed from their surrounding gas and dust-rich regions in star-forming clouds. By contrast, the region of star formation closest to CX330 is over a thousand light-years away.

“CX330 is both more intense and more isolated than any of these young outbursting objects that we’ve ever seen,” said Joel Green, study co-author and researcher at the Space Telescope Science Institute in Baltimore. “This could be the tip of the iceberg—these objects may be everywhere.”

In fact, it is possible that all stars go through this dramatic stage of development in their youth, but that the outbursts are too short in cosmological time for humans to observe many of them.

How did CX330 become so isolated? One idea is that it may have been born in a star-forming region, but was ejected into its present lonely pocket of the galaxy. But this is unlikely, astronomers say. Because CX330 is in a youthful phase of its development—likely less than 1 million years old—and is still eating its surrounding disk, it must have formed near its present location in the sky.

“If it had migrated from a star-forming region, it couldn’t get there in its lifetime without stripping its disk away entirely,” Britt said.

CX330 may also help scientists study the way stars form under different circumstances. One scenario is that stars form through turbulence. In this “hierarchical” model, a critical density of gas in a cloud causes the cloud to gravitationally collapse into a star. A different model, called “competitive accretion,” suggests that stars begin as low-mass cores that fight over the mass of material left in the cloud. CX330 more naturally fits into the first scenario, as the turbulent circumstances would theoretically allow for a lone star to form.

It is still possible that other intermediate- to low-mass stars are in the immediate vicinity of CX330, but have not been detected yet.

When CX330 was last viewed in August 2015, it was still outbursting. Astronomers plan to continue studying the object, including with future telescopes that could view it in other wavelengths of light.

Outbursts from a young star change the chemistry of the star’s disk, from which planets may eventually form. If the phenomenon is common, that means that planets, including our own, may carry the chemical signatures of an ancient disk of gas and dust scarred by stellar outbursts.

But as CX330 is continuing to devour its disk with increasing voracity, astronomers do not expect that planets are forming in its system.

“If it’s truly a massive star, its lifetime is short and violent, and I wouldn’t recommend being a planet around it,” Green said. “You could experience some pretty intense heat for a few centuries.”

The Role Of Magnetic Fields In Star Formation

The star forming molecular clump W43-MM1 is very massive and dense, containing about 2100 solar masses of material in a region only one-third of a light year across (for comparison, the nearest star to the Sun is a bit over four light years away).

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Previous observations of this clump found evidence for infalling motions (signaling that material is still accumulating onto a new star) and weak magnetic fields. These fields are detected by looking for polarized light, which is produced when radiation scatters off of elongated dust grains aligned by magnetic fields. The Submillimeter Array recently probed this source with high spatial resolutions and found evidence for even stronger magnetic fields in places. One of the outstanding issues in star formation is the extent to which magnetic fields inhibit the collapse of material onto stars, and this source seems to offer a particularly useful example.

CfA astronomers Josep Girart and TK Sridharan and their colleagues have used the ALMA submillimeter facility to obtain images with spatial scales as small as 0.03 light years. Their detailed polarization maps show that the magnetic field is well ordered all across the clump, which itself is actually fifteen smaller fragments, one of which (at 312 solar masses) appears to be the most massive fragment known.

The scientists analyze the magnetic field strengths and show that, even in the least massive fragment the field is not strong enough to inhibit gravitational collapse. In fact, they find indications that gravity, as it pulls material inward, drags the magnetic field lines along. They are, however, unable to rule out possible further fragmentation. The research is the most precise study of magnetic fields in star forming massive clumps yet undertaken, and provides a new reference point for theoretical models.

Scientists Observe A Superluminous Supernova That Appears To Have Exploded Twice

Supernovae are among the most violent phenomena in the universe. They are huge explosions that end the lives of certain types of stars. These explosions release immense amounts of energy, so much that some can be observed from Earth with the naked eye, appearing as points of light that are briefly brighter than all the millions of stars in the galaxies where they are found. Following an intense burst of light lasting a few weeks, supernovae start to fade gradually until they have effectively burned out.

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There are several types of supernovae. The astronomers classify them by their observable characteristics, which give clues about their origin. Among the most well known are those of type Ia .When a white dwarf, the final state of a star slightly more massive than the sun, absorbs mass from another nearby star or merges with another white dwarf, its mass grows until it becomes unstable and a thermonuclear explosion occurs. As these events produce a characteristic luminosity, they can be used by astronomers as “standard candles” to measure large distances in the universe, like sailors to inferring the distance of a known lighthouse at night by estimating its brightness.

The other types of supernovae are produced when very massive stars exhaust their fuel, so that nuclear fusion in their interiors comes to an end. This fusion not only causes stars to emit light and heat, but keeps them in equilibrium so that they don’t collapse under their own gravity. When the fusion stops, the centre of the star collapses and the outer layers are flung outwards with violence, causing a supernova, while the centre implodes, leaving a neutron star—or for very massive stars, a black hole.

In recent years, a new type of supernova has been discovered, about which very little is yet known, and which are brighter and longer-lasting. Astronomers call them superluminous supernovae (SLSN). Although only about a dozen of them are known, an international group of researchers has used the Gran Telescopio CANARIAS (GTC) to observe a superluminous supernova almost from the moment it occurred. The research has revealed surprising behaviour, because this supernova showed an initial increase in brightness that later declined for a few days, and then increased again much more strongly. The scientists have combined from the GTC with other observations in order to try to explain the origin of the phenomenon.

“Superluminous supernovas are up to a hundred times more energetic than type 1a supernovae because they can remain bright for up to six months before fading, rather than just a few weeks,” explains Mathew Smith, a postdoctoral researcher at the University of Southampton (UK) and the person directing this study, whose results have been published in the specialized journal The Astrophysical Journal Letters. “What we have managed to observe, which is completely new, is that before the major explosion, there is a shorter, less luminous outburst, which we can pick out because it is followed by a dip in the light curve, and which lasts just a few days.”

It is the first time that something like this has been observed in a supernova. “From our data, we have tried to determine if this is a characteristic unique to this object, or whether it is a common feature of all superluminous supernovae, but has not been observed before, which is perfectly possible given their unpredictable nature,” says the scientist.

This new, intriguing object, given the cryptic name of DES14X3taz by the astronomers, was discovered on December 21, 2014 by the Dark Energy Survey, an international project that surveys the night sky, making precision measurements of over 300 million galaxies that are situated thousands of millions of light years from Earth, and incidentally detecting thousands of supernovae and other transient phenomena. The objective of this survey is to explain the expansion of the universe, and to find clues to the nature of dark energy. To do this, astronomers are using an extremely sensitive 570 megapixel digital camera on the four metre Victor M. Blanco telescope at the Inter-American Observatory at Cerro Tololo (Chile).

Once DES14X3taz had been identified as a possible superluminous supernova, an immediate observation was requested on the GTC, which turned its powerful eye toward it over two nights of observation, January 26 and February 6, 2015. GTC devotes some of its observing time to “targets of opportunity,” so that other programmed observations can postponed to prioritize such transient phenomena, which may offer unrepeatable opportunities.

“The GTC, with its huge 10.4m mirror, and its OSIRIS instrument, is the ideal tool to observer this SNSL, which is at a vast distance and because we are looking for information in the visible and the near infrared,” says Smith, who is a participant in the Dark Energy Survey. Thanks to the observations made with the GTC and other telescopes, Smith and his collaborators could reconstruct the evolution of the brightness of DES14X3taz from almost the moment of its detection. They have also determined its absolute brightness with great precision, as well as its distance, some 6,400 million light years.

2-lightshedona

After comparing their observations with several physical models, the astronomers concluded in their article that the most plausible explanation is that the mechanism causing this supernova is the birth of a “magnetar,” a neutron star that rotates very rapidly on its axis. In the data, the initial peak of the brightness graph is followed by rapid cooling of the object, after which there is a quicker rise in brightness. This is consistent with the emission of a huge bubble of material into the surrounding space, which cools rapidly as it grows in size.

“We think that a very massive star, some 200 times the mass of the Sun, collapses to form a magnetar. In the process, the first explosion occurs, which expels into space a quantity of matter equivalent to the mass of our sun, and this gives rise to the first peak of the graph. The second peak occurs when the star collapses to form the magnetar, which is a very dense object rotating rapidly on its axis, and which heats up the matter expelled from the first explosion. This heating is what generates the second peak in the luminosity,” explains Smith.

This understanding may allow us to “standardize” superluminous supernovae as has occurred for the type Ia supernovae for use as a reference source for distance measurement on large scales in the universe. Its high luminosity may make these objects useful for calculating distances on larger scales, and with greater accuracy than current techniques. However, before we get to that point, we need a much deeper understanding of their origin and their nature.

Another mystery about this new type of supernova is that, until recently, all the examples detected have been in small galaxies with low metallicity (low content in heavy elements), which is not well understood. “It is a part of the mystery of these objects,” says Smith, and adds that among future priorities, we need to detect more superluminous supernovae and observe them from the moment they explode in real time with a telescope the size of the GTC.

Experimentation Suggests Vikings Could Have Used Sunstone To Navigate

A team of researchers from several institutions in Hungary has conducted experiments meant to test the possibility that the Vikings actually did use sunstones to navigate. In their paper published in Proceedings of the Royal Society A, the team describes the experiments they carried out, their results and why they now believe it is possible to use a sunstone as a navigational aid during times when the skies are covered with clouds.

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The exploits of the Vikings have been well documented—they conducted raids across Europe from the late 790s till 1066, when the Normans famously conquered England. But as more recent research has established, they were also long-distance seafaring travelers, venturing as far as the Middle East and North America. But how they found their way across vast stretches of ocean has been a bit of a mystery, particularly during times when there were no stars or sun in the sky to guide them. Some historical evidence such as Icelandic legends have mentioned travel under snowy skies using sunstones and a study of a Viking wreck conducted in 2002 revealed that a crystal (Icelandic spar) had been onboard that was found near other implements used for navigation.

Modern sunstone is a type of crystal that, when viewed from different angles, offers a spangled optical effect. In this new effort, the researchers have conducted a study designed to test the possibility that such crystals could really have helped Vikings find their way across the ocean.

They believe it was a three step process: (1) determine the direction of light from the sky using the sunstone held up to the sky, (2) use that information to determine the direction of sunlight and then (3) use a shadow stick to determine which direction was north. The team previously conducted tests to measure the accuracy of the first two steps and, apparently satisfied with the results, have now conducted experiments with the third.

To test the third step, the researchers asked 10 volunteers to try to work out the position of the sun in a digital planetarium using dots to stand in for results of using a sunstone. After conducting a total of 2,400 trials, the researchers report that 48 percent resulted in producing an accurate reading to within just one degree. They noted also that the volunteers did best when the virtual sun was near the horizon, showing that the method worked best at dawn and dusk. The team suggests their results indicate that it was possible that the Vikings used sunstones to navigate under cloudy skies.

Jupiter’s Great Red Spot Heats Planet’s Upper Atmosphere

Researchers from Boston University’s (BU) Center for Space Physics report today in Nature that Jupiter’s Great Red Spot may provide the mysterious source of energy required to heat the planet’s upper atmosphere to the unusually high values observed.

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Sunlight reaching Earth efficiently heats the terrestrial atmosphere at altitudes well above the sur-face—even at 250 miles high, for example, where the International Space Station orbits. Jupiter is over five times more distant from the Sun, and yet its upper atmosphere has temperatures, on av-erage, comparable to those found at Earth. The sources of the non-solar energy responsible for this extra heating have remained elusive to scientists studying processes in the outer solar system.

“With solar heating from above ruled out, we designed observations to map the heat distribution over the entire planet in search for any temperature anomalies that might yield clues as to where the energy is coming from,” explained Dr. James O’Donoghue, research scientist at BU, and lead author of the study.

Astronomers measure the temperature of a planet by observing the non-visible, infra-red (IR) light it emits. The visible cloud tops we see at Jupiter are about 30 miles above its rim; the IR emissions used by the BU team came from heights about 500 miles higher. When the BU observ-ers looked at their results, they found high altitude temperatures much larger than anticipated whenever their telescope looked at certain latitudes and longitudes in the planet’s southern hemi-sphere.

“We could see almost immediately that our maximum temperatures at high altitudes were above the Great Red Spot far below—a weird coincidence or a major clue?” O’Donoghue added.

Jupiter’s Great Red Spot (GRS) is one of the marvels of our solar system. Discovered within years of Galileo’s introduction of telescopic astronomy in the 17th Century, its swirling pattern of colorful gases is often called a “perpetual hurricane.” The GRS has varied is size and color over the centuries, spans a distance equal to three earth-diameters, and has winds that take six days to complete one spin. Jupiter itself spins very quickly, completing one revolution in only ten hours.

“The Great Red Spot is a terrific source of energy to heat the upper atmosphere at Jupiter, but we had no prior evidence of its actual effects upon observed temperatures at high altitudes,” ex-plained Dr. Luke Moore, a study co-author and research scientist in the Center for Space Physics at BU.

Solving an “energy crisis” on a distant planet has implications within our solar system, as well as for planets orbiting other stars. As the BU scientists point out, the unusually high temperatures far above Jupiter’s visible disk is not a unique aspect of our solar system. The dilemma also oc-curs at Saturn, Uranus and Neptune, and probably for all giant exoplanets outside our solar sys-tem.

“Energy transfer to the upper atmosphere from below has been simulated for planetary atmos-pheres, but not yet backed up by observations,” O’Donoghue said. “The extremely high tempera-tures observed above the storm appear to be the ‘smoking gun’ of this energy transfer, indicating that planet-wide heating is a plausible explanation for the ‘energy crisis.’ “