Wednesday, July 18, 2018

Supersharp Images from New VLT Adaptive Optics

Neptune from the VLT with MUSE/GALACSI Narrow Field Mode adaptive optics

PR Image eso1824b
Neptune from the VLT with and without adaptive optics

PR Image eso1824c
Neptune from the VLT and Hubble

PR Image eso1824d
MUSE images of the globular star cluster NGC 6388


ESOcast 172 Light: Supersharp Images from New VLT Adaptive Optics (4K UHD)
ESOcast 172 Light: Supersharp Images from New VLT Adaptive Optics (4K UHD)

Zooming in on the globular star cluster NGC 6388
Zooming in on the globular star cluster NGC 6388 

ESO’s Very Large Telescope (VLT) has achieved first light with a new adaptive optics mode called laser tomography — and has captured remarkably sharp test images of the planet Neptune, star clusters and other objects. The pioneering MUSE instrument in Narrow-Field Mode, working with the GALACSI adaptive optics module, can now use this new technique to correct for turbulence at different altitudes in the atmosphere. It is now possible to capture images from the ground at visible wavelengths that are sharper than those from the NASA/ESA Hubble Space Telescope. The combination of exquisite image sharpness and the spectroscopic capabilities of MUSE will enable astronomers to study the properties of astronomical objects in much greater detail than was possible before.

The MUSE (Multi Unit Spectroscopic Explorer) instrument on ESO’s Very Large Telescope (VLT) works with an adaptive optics unit called GALACSI. This makes use of the Laser Guide Star Facility, 4LGSF, a subsystem of the Adaptive Optics Facility (AOF). The AOF provides adaptive optics for instruments on the VLTs Unit Telescope 4 (UT4). MUSE was the first instrument to benefit from this new facility and it now has two adaptive optics modes — the Wide Field Mode and the Narrow Field Mode [1].

The MUSE Wide Field Mode coupled to GALACSI in ground-layer mode corrects for the effects of atmospheric turbulence up to one kilometre above the telescope over a comparatively wide field of view. But the new Narrow Field Mode using laser tomography corrects for almost all of the atmospheric turbulence above the telescope to create much sharper images, but over a smaller region of the sky [2]

With this new capability, the 8-metre UT4 reaches the theoretical limit of image sharpness and is no longer limited by atmospheric blur. This is extremely difficult to attain in the visible and gives images comparable in sharpness to those from the NASA/ESA Hubble Space Telescope. It will enable astronomers to study in unprecedented detail fascinating objects such as supermassive black holes at the centres of distant galaxies, jets from young stars, globular clusters, supernovae, planets and their satellites in the Solar System and much more.

Adaptive optics is a technique to compensate for the blurring effect of the Earth’s atmosphere, also known as astronomical seeing, which is a big problem faced by all ground-based telescopes. The same turbulence in the atmosphere that causes stars to twinkle to the naked eye results in blurred images of the Universe for large telescopes. Light from stars and galaxies becomes distorted as it passes through our atmosphere, and astronomers must use clever technology to improve image quality artificially.

To achieve this four brilliant lasers are fixed to UT4 that project columns of intense orange light 30 centimetres in diameter into the sky, stimulating sodium atoms high in the atmosphere and creating artificial Laser Guide Stars. Adaptive optics systems use the light from these “stars” to determine the turbulence in the atmosphere and calculate corrections one thousand times per second, commanding the thin, deformable secondary mirror of UT4 to constantly alter its shape, correcting for the distorted light.

MUSE is not the only instrument to benefit from the Adaptive Optics Facility. Another adaptive optics system, GRAAL, is already in use with the infrared camera HAWK-I. This will be followed in a few years by the powerful new instrument ERIS. Together these major developments in adaptive optics are enhancing the already powerful fleet of ESO telescopes, bringing the Universe into focus.

This new mode also constitutes a major step forward for the ESO’s Extremely Large Telescope, which will need Laser Tomography to reach its science goals. These results on UT4 with the AOF will help to bring ELT’s engineers and scientists closer to implementing similar adaptive optics technology on the 39-metre giant.


[1] MUSE and GALACSI in Wide-Field Mode already provides a correction over a 1.0-arcminute-wide field of view, with pixels 0.2 by 0.2 arcseconds in size. This new Narrow-Field Mode from GALACSI covers a much smaller 7.5-arcsecond field of view, but with much smaller pixels just 0.025 by 0.025 arcseconds to fully exploit the exquisite resolution.

[2] Atmospheric turbulence varies with altitude; some layers cause more degradation to the light beam from stars than others. The complex adaptive optics technique of Laser Tomography aims to correct mainly the turbulence of these atmospheric layers. A set of pre-defined layers are selected for the MUSE/GALACSI Narrow Field Mode at 0 km (ground layer; always an important contributor), 3, 9 and 14 km altitude. The correction algorithm is then optimised for these layers to enable astronomers to reach an image quality almost as good as with a natural guide star and matching the theoretical limit of the telescope.

More Information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 15 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Joël Vernet
ESO MUSE and GALACSI Project Scientist
Garching bei München, Germany
Tel: +49 89 3200 6579

Roland Bacon
MUSE Principal Investigator / Lyon Centre for Astrophysics Research (CRAL)
Cell: +33 6 08 09 14 27

Calum Turner
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591

Source: ESO/News

Tuesday, July 17, 2018

Astronomers Find a Famous Exoplanet’s Doppelgänger

Direct Wircam image of 2MASS 0249 system taken wiht CFHT's infrared camera WIRCam. 2MASS 0249c is located 2000 astronomical units from the host brown dwarfs that are unresolved in this image. Credits: T. Dupuy, M. Liu

The infrared spectra of 2MASS 0249c and beta Pictoris b are similar, as expected for two objects of comparable mass that formed in the same stellar nursery. Unlike 2MASS 0249c, beta Pictoris b orbits much closer to its massive host star and is imbedded in a bright circumstellar disk. Credits: T. Dupuy, ESO/A.-M. Lagrange et al.

When it comes to extrasolar planets, appearances can be deceiving. Astronomers have imaged a new planet, and it appears nearly identical to one of the best studied gas-giant planets. But this doppelgänger differs in one very important way: its origin. “We have found a gas-giant planet that is a virtual twin of a previously known planet, but it looks like the two objects formed in different ways,” said Trent Dupuy, astronomer at the Gemini Observatory and leader of the study.

Emerging from stellar nurseries of gas and dust, stars are born like kittens in a litter, in bunches and inevitably wandering away from their birthplace. These litters comprise stars that vary greatly, ranging from tiny runts incapable of generating their own energy (called brown dwarfs) to massive stars that end their lives with supernova explosions. In the midst of this turmoil, planets form around these new stars. And once the stellar nursery exhausts its gas, the stars (with their planets) leave their birthplace and freely wander the Galaxy. Because of this exodus, astronomers believe there should be planets born at the same time from the same stellar nursery, but orbiting stars that have moved far away from each other over the eons, like long-lost siblings.

“To date, exoplanets found by direct imaging have basically been individuals, each distinct from the other in their appearance and age. Finding two exoplanets with almost identical appearances and yet having formed so differently opens a new window for understanding these objects,” said Michael Liu, astronomer at the University of Hawai`i Institute for Astronomy, and a collaborator on this work.

Dupuy, Liu, and their collaborators have identified the first case of such a planetary doppelgänger. One object has long been known: the 13-Jupiter-mass planet beta Pictoris b, one of the first planets discovered by direct imaging, back in 2009. The new object, dubbed 2MASS 0249 c, has the same mass, brightness, and spectrum as beta Pictoris b.

After discovering this object with the Canada-France-Hawaii Telescope (CFHT), Dupuy and collaborators then determined that 2MASS 0249 c and beta Pictoris b were born in the same stellar nursery. On the surface, this makes the two objects not just look-alikes but genuine siblings.

However, the planets have vastly different living situations, namely the types of stars they orbit. The host for beta Pictoris b is a star 10 times brighter than the Sun, while 2MASS 0249 c orbits a pair of brown dwarfs that are 2000 times fainter than the Sun. Furthermore, beta Pictoris b is relatively close to its host, about 9 astronomical units (AU, the distance from the Earth to the Sun), while 2MASS 0249 c is 2000 AU from its binary host.

These drastically different arrangements suggest that the planets’ upbringings were not at all alike. The traditional picture of gas-giant formation, where planets start as small rocky cores around their host star and grow by accumulating gas from the star’s disk, likely created beta Pictoris b. In contrast, the host of 2MASS 0249 c did not have enough of a disk to make a gas giant, so the planet likely formed by directly accumulating gas from the original stellar nursery.

“2MASS 0249 c and beta Pictoris b show us that nature has more than one way to make very similar looking exoplanets,” says Kaitlin Kratter, astronomer at the University of Arizona and a collaborator on this work. "beta Pictoris b probably formed like we think most gas giants do, starting from tiny dust grains. In contrast, 2MASS 0249 c looks like an underweight brown dwarf that formed from the collapse of a gas cloud. They’re both considered exoplanets, but 2MASS 0249 c illustrates that such a simple classification can obscure a complicated reality.”

The team first identified 2MASS 0249 c using images from CFHT, and their repeated observations revealed this object is orbiting at a large distance from its host. The system belongs to the beta Pictoris moving group, a widely dispersed set of stars named for its famous planet-hosting star. The team’s observations with the W. M. Keck Telescope determined that the host is actually a closely separated pair of brown dwarfs. So altogether, the 2MASS 0249 system comprises two brown dwarfs and one gas-giant planet. Follow-up spectroscopy of 2MASS 0249 c with the NASA Infrared Telescope Facility and the Astrophysical Research Consortium 3.5-meter Telescope at Apache Point Telescope demonstrated that it shares a remarkable resemblance to beta Pictoris b.

The 2MASS 0249 system is an appealing target for future studies. Most directly imaged planets are very close to their host stars, inhibiting detailed studies of the planets due to the bright light from the stars. In contrast, the very wide separation of 2MASS 0249 c from its host binary will make measurements of properties like its surface weather and composition much easier, leading to a better understanding of the characteristics and origins of gas-giant planets.

This work is accepted for publication in the Astronomical Journal.

This work has been supported by the National Science Foundation under Grant No. AST-1518339. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Additional information : arXiv link to the Paper

Contact Information:

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Mary Beth Laychak, Outreach manager
Canada-France-Hawaii Telescope

Science contacts

Trent Dupuy
Gemini Observatory

Michael Liu
UH Institute for Astronomy

Monday, July 16, 2018

VLA Gives Tantalizing Clues About Source of Energetic Cosmic Neutrino

Supermassive black hole at core of galaxy accelerates particles in jets moving outward at nearly the speed of light. In a Blazar, one of these jets is pointed nearly straight at Earth. Credit: Sophia Dagnello, NRAO/AUI/NSF

Astronomers pinpoint likely source of high-energy cosmic rays for first time

A single, ghostly subatomic particle that traveled some 4 billion light-years before reaching Earth has helped astronomers pinpoint a likely source of high-energy cosmic rays for the first time. Subsequent observations with the National Science Foundation’s (NSF) Karl G. Jansky Very Large Array (VLA) have given the scientists some tantalizing clues about how such energetic cosmic rays may be formed at the cores of distant galaxies.

On September 22, 2017, an observatory called IceCube, made up of sensors distributed through a square kilometer of ice under the South Pole, recorded the effects of a high-energy neutrino coming from far beyond our Milky Way Galaxy. Neutrinos are subatomic particles with no electrical charge and very little mass. Since they interact only very rarely with ordinary matter, neutrinos can travel unimpeded for great distances through space.

Follow-up observations with orbiting and ground-based telescopes from around the world soon showed that the neutrino likely was coming from the location of a known cosmic object — a blazar called TXS 0506+056, about 4 billion light-years from Earth. Like most galaxies, blazars contain supermassive black holes at their cores. The powerful gravity of the black hole draws in material that forms a hot rotating disk. Jets of particles traveling at nearly the speed of light are ejected perpendicular to the disk. Blazars are a special class of galaxies, because in a blazar, one of the jets is pointed almost directly at Earth.

Theorists had suggested that these powerful jets could greatly accelerate protons, electrons, or atomic nuclei, turning them into the most energetic particles known in the Universe, called ultra-high energy cosmic rays. The cosmic rays then could interact with material near the jet and produce high-energy photons and neutrinos, such as the neutrino detected by IceCube.

Cosmic rays were discovered in 1912 by physicist Victor Hess, who carried instruments in a balloon flight. Subsequent research showed that cosmic rays are either protons, electrons, or atomic nuclei that have been accelerated to speeds approaching that of light, giving some of them energies much greater than those of even the most energetic electromagnetic waves. In addition to the active cores of galaxies, supernova explosions are probable sites where cosmic rays are formed. The galactic black-hole engines, however, have been the prime candidate for the source of the highest-energy cosmic rays, and thus of the high-energy neutrinos resulting from their interactions with other matter.

“Tracking that high-energy neutrino detected by IceCube back to TXS 0506+056 makes this the first time we’ve been able to identify a specific object as the probable source of such a high-energy neutrino,” said Gregory Sivakoff, of the University of Alberta in Canada.

Following the IceCube detection, astronomers looked at TXS 0506+056 with numerous telescopes and found that it had brightened at wavelengths including gamma rays, X-rays, and visible light. The blazar was observed with the VLA six times between October 5 and November 21, 2017.

“The VLA data show that the radio emission from this blazar was varying greatly at the time of the neutrino detection and for two months afterward. The radio frequency with the brightest radio emission also was changing,” Sivakoff said.

TXS 0506+056 has been monitored over a number of years with the NSF’s Very Long Baseline Array (VLBA), a continent-wide radio telescope system that produces extremely detailed images. The high-resolution VLBA images have shown bright knots of radio emission that travel outward within the jets at speeds nearly that of light. The knots presumably are caused by denser material ejected sporadically through the jet.

“The behavior we saw with the VLA is consistent with the emission of at least one of these knots. It’s an intriguing possibility that such knots may be associated with generating high-energy cosmic rays and thus the kind of high-energy neutrino that IceCube found,” Sivakoff said.

The scientists continue to study TXS 0506+056. “There are a lot of exciting phenomena going on in this object,” Sivakoff concluded.

“The era of multi-messenger astrophysics is here,” said NSF Director France Córdova. “Each messenger — from electromagnetic radiation, gravitational waves and now neutrinos — gives us a more complete understanding of the Universe, and important new insights into the most powerful objects and events in the sky. Such breakthroughs are only possible through a long-term commitment to fundamental research and investment in superb research facilities.”

Sivakoff and numerous colleagues from institutions around the world are reporting their findings in the journal Science.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Dave Finley, 
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“Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A”,

Sunday, July 15, 2018

Could gravitational waves reveal how fast our universe is expanding?

Artist’s depiction of the last instances of a neutron star and black hole merger, as the neutron star is destroyed by the tidal pull of the black hole (at the center of the disk). Image: A. Tonita, L. Rezzolla, F. Pannarale

Signals from rare black hole-neutron star pairs could pinpoint rate at which universe is growing, researchers say.

Since it first exploded into existence 13.8 billion years ago, the universe has been expanding, dragging along with it hundreds of billions of galaxies and stars, much like raisins in a rapidly rising dough.

Astronomers have pointed telescopes to certain stars and other cosmic sources to measure their distance from Earth and how fast they are moving away from us — two parameters that are essential to estimating the Hubble constant, a unit of measurement that describes the rate at which the universe is expanding.

But to date, the most precise efforts have landed on very different values of the Hubble constant, offering no definitive resolution to exactly how fast the universe is growing. This information, scientists believe, could shed light on the universe’s origins, as well as its fate, and whether the cosmos will expand indefinitely or ultimately collapse.

Now scientists from MIT and Harvard University have proposed a more accurate and independent way to measure the Hubble constant, using gravitational waves emitted by a relatively rare system: a black hole-neutron star binary, a hugely energetic pairing of a spiraling black hole and a neutron star. As these objects circle in toward each other, they should produce space-shaking gravitational waves and a flash of light when they ultimately collide.

In a paper published today in Physical Review Letters, the researchers report that the flash of light would give scientists an estimate of the system’s velocity, or how fast it is moving away from the Earth. The emitted gravitational waves, if detected on Earth, should provide an independent and precise measurement of the system’s distance. Even though black hole-neutron star binaries are incredibly rare, the researchers calculate that detecting even a few should yield the most accurate value yet for the Hubble constant and the rate of the expanding universe.

“Black hole-neutron star binaries are very complicated systems, which we know very little about,” says Salvatore Vitale, assistant professor of physics at MIT and lead author of the paper. “If we detect one, the prize is that they can potentially give a dramatic contribution to our understanding of the universe.”

Vitale’s co-author is Hsin-Yu Chen of Harvard.

Competing constants

Two independent measurements  of the Hubble constant were made recently, one using NASA's Hubble Space Telescope and another using the European Space Agency's Planck satellite. The Hubble Space Telescope’s measurement is based on observations of a type of star known as a Cepheid variable, as well as on observations of supernovae. Both of these objects are considered “standard candles,” for their predictable pattern of brightness, which scientists can use to estimate the star’s distance and velocity.

The other type of estimate is based on observations of the fluctuations in the cosmic microwave background — the electromagnetic radiation that was left over in the immediate aftermath of the Big Bang, when the universe was still in its infancy. While the observations by both probes are extremely precise, their estimates of the Hubble constant disagree significantly.

“That’s where LIGO comes into the game,” Vitale says.

LIGO, or the Laser Interferometry Gravitational-Wave Observatory, detects gravitational waves — ripples in the Jell-O of space-time, produced by cataclysmic astrophysical phenomena.

“Gravitational waves provide a very direct and easy way of measuring the distances of their sources,” Vitale says. “What we detect with LIGO is a direct imprint of the distance to the source, without any extra analysis.”

In 2017, scientists got their first chance at estimating the Hubble constant from a gravitational-wave source, when LIGO and its Italian counterpart Virgo detected a pair of colliding neutron stars for the first time. The collision released a huge amount of gravitational waves, which researchers measured to determine the distance of the system from Earth. The merger also released a flash of light, which astronomers focused on with ground and space telescopes to determine the system’s velocity.

With both measurements, scientists calculated a new value for the Hubble constant. However, the estimate came with a relatively large uncertainty of 14 percent, much more uncertain than the values calculated using the Hubble Space Telescope and the Planck satellite.

Vitale says much of the uncertainty stems from the fact that it can be challenging to interpret a neutron star binary’s distance from Earth using the gravitational waves that this particular system gives off.   

“We measure distance by looking at how ‘loud’ the gravitational wave is, meaning how clear it is in our data,” Vitale says. “If it’s very clear, you can see how loud it is, and that gives the distance. But that’s only partially true for neutron star binaries.”

That’s because these systems, which create a whirling disc of energy as two neutron stars spiral in toward each other, emit gravitational waves in an uneven fashion. The majority of gravitational waves shoot straight out from the center of the disc, while a much smaller fraction escapes out the edges. If scientists detect a “loud” gravitational wave signal, it could indicate one of two scenarios: the detected waves stemmed from the edge of a system that is very close to Earth, or the waves emanated from the center of a much further system.

“With neutron star binaries, it’s very hard to distinguish between these two situations,” Vitale says.

A new wave

In 2014, before LIGO made the first detection of gravitational waves, Vitale and his colleagues observed that a binary system composed of a black hole and a neutron star could give a more accurate distance measurement, compared with neutron star binaries. The team was investigating how accurately one could measure a black hole’s spin, given that the objects are known to spin on their axes, similarly to Earth but much more quickly.

The researchers simulated a variety of systems with black holes, including black hole-neutron star binaries and neutron star binaries. As a byproduct of this effort, the team noticed that they were able to more accurately determine the distance of black hole-neutron star binaries, compared to neutron star binaries. Vitale says this is due to the spin of the black hole around the neutron star, which can help scientists better pinpoint from where in the system the gravitational waves are emanating.

“Because of this better distance measurement, I thought that black hole-neutron star binaries could be a competitive probe for measuring the Hubble constant,” Vitale says. “Since then, a lot has happened with LIGO and the discovery of gravitational waves, and all this was put on the back burner.”

Vitale recently circled back to his original observation, and in this new paper, he set out to answer a theoretical question:

“Is the fact that every black hole-neutron star binary will give me a better distance going to compensate for the fact that potentially, there are far fewer of them in the universe than neutron star binaries?” Vitale says.

To answer this question, the team ran simulations to predict the occurrence of both types of binary systems in the universe, as well as the accuracy of their distance measurements. From their calculations, they concluded that, even if neutron binary systems outnumbered black hole-neutron star systems by 50-1, the latter would yield a Hubble constant similar in accuracy to the former.

More optimistically, if black hole-neutron star binaries were slightly more common, but still rarer than neutron star binaries, the former would produce a Hubble constant that is four times as accurate.

“So far, people have focused on binary neutron stars as a way of measuring the Hubble constant with gravitational waves,” Vitale says. “We’ve shown there is another type of gravitational wave source which so far has not been exploited as much: black holes and neutron stars spiraling together,” Vitale says. “LIGO will start taking data again in January 2019, and it will be much more sensitive, meaning we’ll be able to see objects farther away. So LIGO should see at least one black hole-neutron star binary, and as many as 25, which will help resolve the existing tension in the measurement of the Hubble constant, hopefully in the next few years.”

This research was supported, in part, by the National Science Foundation and the LIGO Laboratory.

Saturday, July 14, 2018

The Eagle Nebula (M16): "X"-ploring the Eagle Nebula and "Pillars of Creation"

Pillars of Creatio/M16
Credit: X-ray: NASA/CXC/INAF/M.Guarcello et al.; Optical: NASA/STScI
JPEG (797 kb) - Large JPEG (8 MB) -Tiff (15.8 MB) - More Images

Field of ViewX-ray/Optical
Credit: X-ray: NASA/CXC/INAF/M.Guarcello et al.; Optical: NASA/STScI

Optical and infrared identifications with stars were used to sort out chance interlopers in the foreground or background, and to determine that more than two-thirds of the sources are likely young stars that are members of the NGC 6611 cluster.

Chandra's unique ability to resolve and locate X-ray sources made it possible to identify hundreds of very young stars, and those still in the process of forming (known as "protostars"). Infrared observations from NASA's Spitzer Space Telescope and the European Southern Observatory indicate that 219 of the X-ray sources in the Eagle Nebula are young stars surrounded by disks of dust and gas and 964 are young stars without these disks.

Combined with the Chandra observations, the data show that X-ray activity in young stars with disks is, on average, a few times less intense that in young stars without disks. This behavior is likely due to the interaction of the disk with the magnetic field of the host star. Much of the matter in the disks around these protostars will eventually be blown away by radiation from their host stars, but, in certain cases, some of it may form into planets.

This new composite image shows the region around the Pillars, which are about 5,700 light years from Earth. The image combines X-ray data from NASA's Chandra X-ray Observatory and Hubble Space Telescope optical data. The optical image, taken with filters to emphasize the interstellar gas and dust, shows dusty brown nebula immersed in a blue-green haze, and a few stars that appear as pink dots in the image. The Chandra data reveal X-rays from hot outer atmospheres from stars. In this image, low, medium, and high-energy X-rays detected by Chandra have been colored red, green, and blue.

In the image, some of the X-ray sources appear to be located in the Pillars. However, an analysis of the absorption of X-rays from these sources indicates that almost all of these sources belong to the larger Eagle Nebula rather than being immersed in the Pillars.

Three X-ray sources appear to lie near the tip of the largest Pillar. Infrared observations show a protostar containing four or five times the mass of the Sun is located near one of these sources — the blue one near the tip of the Pillar. This source exhibits strong absorption of low-energy X-rays, consistent with a location inside the Pillar. Similar arguments show that one of these sources is associated with a disk-less star outside the Pillar, and one is a foreground object.

A paper by Mario Guarcello, currently at the National Institute for Astronomy in Italy, and colleagues describing these results appeared in The Astrophysical Journal. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Fast Facts for The Eagle Nebula (M16):

Scale: Image is about 2.5 arcmin (5.13 light years across) across
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 18h 18m 51.79s | Dec -13º 49' 54.93"
Constellation: Serpens
Observation Date: 07/30/2001
Observation Time: 22 hours
Obs. ID: 978
Instrument: ACIS
References: M. Guarcello et al. 2012, ApJ, 753, 117; arXiv:1205.2111
Color Code: X-ray (larger point sources): Red (0.5-1.5 keV); Green (1.5-2.5 keV); Blue (2.5-7.0 keV); Optical (diffuse emission & smaller point sources): Red, Green and Blue
Distance Estimate: About 5,700 light years

Friday, July 13, 2018

Hubble and Gaia Team Up to Fuel Cosmic Conundrum

Using two of the world’s most powerful space telescopes — NASA’s Hubble and ESA’s Gaia — astronomers have made the most precise measurements to date of the universe’s expansion rate. This is calculated by gauging the distances between nearby galaxies using special types of stars called Cepheid variables as cosmic yardsticks. By comparing their intrinsic brightness as measured by Hubble, with their apparent brightness as seen from Earth, scientists can calculate their distances. Gaia further refines this yardstick by geometrically measuring the distances to Cepheid variables within our Milky Way galaxy. This allowed astronomers to more precisely calibrate the distances to Cepheids that are seen in outside galaxies.  Science: NASA, ESA, and A. Riess (STScI/JHU)

Using the power and synergy of two space telescopes, astronomers have made the most precise measurement to date of the universe’s expansion rate.

The results further fuel the mismatch between measurements for the expansion rate of the nearby universe, and those of the distant, primeval universe — before stars and galaxies even existed.

This so-called “tension” implies that there could be new physics underlying the foundations of the universe. Possibilities include the interaction strength of dark matter, dark energy being even more exotic than previously thought, or an unknown new particle in the tapestry of space.

Combining observations from NASA’s Hubble Space Telescope and the European Space Agency’s (ESA) Gaia space observatory, astronomers further refined the previous value for the Hubble constant, the rate at which the universe is expanding from the big bang 13.8 billion years ago.

But as the measurements have become more precise, the team’s determination of the Hubble constant has become more and more at odds with the measurements from another space observatory, ESA’s Planck mission, which is coming up with a different predicted value for the Hubble constant.

Planck mapped the primeval universe as it appeared only 360,000 years after the big bang. The entire sky is imprinted with the signature of the big bang encoded in microwaves. Planck measured the sizes of the ripples in this Cosmic Microwave Background (CMB) that were produced by slight irregularities in the big bang fireball. The fine details of these ripples encode how much dark matter and normal matter there is, the trajectory of the universe at that time, and other cosmological parameters.

These measurements, still being assessed, allow scientists to predict how the early universe would likely have evolved into the expansion rate we can measure today. However, those predictions don’t seem to match the new measurements of our nearby contemporary universe.

“With the addition of this new Gaia and Hubble Space Telescope data, we now have a serious tension with the Cosmic Microwave Background data,” said Planck team member and lead analyst George Efstathiou of the Kavli Institute for Cosmology in Cambridge, England, who was not involved with the new work.

“The tension seems to have grown into a full-blown incompatibility between our views of the early and late time universe,” said team leader and Nobel Laureate Adam Riess of the Space Telescope Science Institute and the Johns Hopkins University in Baltimore, Maryland. “At this point, clearly it’s not simply some gross error in any one measurement. It’s as though you predicted how tall a child would become from a growth chart and then found the adult he or she became greatly exceeded the prediction. We are very perplexed.”

In 2005, Riess and members of the SHOES (Supernova H0 for the Equation of State) Team set out to measure the universe’s expansion rate with unprecedented accuracy. In the following years, by refining their techniques, this team shaved down the rate measurement’s uncertainty to unprecedented levels. Now, with the power of Hubble and Gaia combined, they have reduced that uncertainty to just 2.2 percent.

Because the Hubble constant is needed to estimate the age of the universe, the long-sought answer is one of the most important numbers in cosmology. It is named after astronomer Edwin Hubble, who nearly a century ago discovered that the universe was uniformly expanding in all directions—a finding that gave birth to modern cosmology.

Galaxies appear to recede from Earth proportional to their distances, meaning that the farther away they are, the faster they appear to be moving away. This is a consequence of expanding space, and not a value of true space velocity. By measuring the value of the Hubble constant over time, astronomers can construct a picture of our cosmic evolution, infer the make-up of the universe, and uncover clues concerning its ultimate fate.

The two major methods of measuring this number give incompatible results. One method is direct, building a cosmic “distance ladder” from measurements of stars in our local universe. The other method uses the CMB to measure the trajectory of the universe shortly after the Big Bang and then uses physics to describe the universe and extrapolate to the present expansion rate. Together, the measurements should provide an end-to-end test of our basic understanding of the so-called “Standard Model” of the universe. However, the pieces don’t fit
Using Hubble and newly released data from Gaia, Riess’ team measured the present rate of expansion to be 73.5 kilometers (45.6 miles) per second per megaparsec. This means that for every 3.3 million light-years farther away a galaxy is from us, it appears to be moving 73.5 kilometers per second faster. However, the Planck results predict the universe should be expanding today at only 67.0 kilometers (41.6 miles) per second per megaparsec. As the teams’ measurements have become more and more precise, the chasm between them has continued to widen, and is now about 4 times the size of their combined uncertainty.

Over the years, Riess’ team has refined the Hubble constant value by streamlining and strengthening the “cosmic distance ladder,” used to measure precise distances to nearby and far-off galaxies. They compared those distances with the expansion of space, measured by the stretching of light from nearby galaxies. Using the apparent outward velocity at each distance, they then calculated the Hubble constant.

To gauge the distances between nearby galaxies, his team used a special type of star as cosmic yardsticks or milepost markers. These pulsating stars, called Cepheid variables, brighten and dim at rates that correspond to their intrinsic brightness. By comparing their intrinsic brightness with their apparent brightness as seen from Earth, scientists can calculate their distances.

Gaia further refined this yardstick by geometrically measuring the distance to 50 Cepheid variables in the Milky Way. These measurements were combined with precise measurements of their brightnesses from Hubble. This allowed the astronomers to more accurately calibrate the Cepheids and then use those seen outside the Milky Way as milepost markers.

“When you use Cepheids, you need both distance and brightness,” explained Riess. Hubble provided the information on brightness, and Gaia provided the parallax information needed to accurately determine the distances. Parallax is the apparent change in an object’s position due to a shift in the observer’s point of view. Ancient Greeks first used this technique to measure the distance from Earth to the Moon.

“Hubble is really amazing as a general-purpose observatory, but Gaia is the new gold standard for calibrating distance. It is purpose-built for measuring parallax—this is what it was designed to do,” Stefano Casertano of Space Telescope Science Institute and a member of the SHOES Team added. “Gaia brings a new ability to recalibrate all past distance measures, and it seems to confirm our previous work. We get the same answer for the Hubble constant if we replace all previous calibrations of the distance ladder with just the Gaia parallaxes. It’s a crosscheck between two very powerful and precise observatories.”

The goal of Riess’ team is to work with Gaia to cross the threshold of refining the Hubble constant to a value of only one percent by the early 2020s. Meanwhile, astrophysicists will likely continue to grapple with revisiting their ideas about the physics of the early universe.

The Riess team's latest results are published in the July 12 issue of the Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, in Washington, D.C.

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Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514

Adam Riess
Space Telescope Science Institute, Baltimore, Maryland

Thursday, July 12, 2018

Colourful Celestial Landscape

Celestial Art 

PR Image eso1823b
RCW 38 in the Constellation of Vela

PR Image eso1823c
Digitized Sky Survey image around the stellar cluster RCW 38


ESOcast 171 Light: Colourful Celestial Landscape (4K UHD)

ESOcast 171 Light: Colourful Celestial Landscape (4K UHD)

Zooming into RCW 38

Panning across RCW 38
Panning across RCW 38

New observations with ESO’s Very Large Telescope show the star cluster RCW 38 in all its glory. This image was taken during testing of the HAWK-I camera with the GRAAL adaptive optics system. It shows RCW 38 and its surrounding clouds of brightly glowing gas in exquisite detail, with dark tendrils of dust threading through the bright core of this young gathering of stars.

This image shows the star cluster RCW 38, as captured by the HAWK-I infrared imager mounted on ESO’s Very Large Telescope (VLT) in Chile. By gazing into infrared wavelengths, HAWK-I can examine dust-shrouded star clusters like RCW 38, providing an unparalleled view of the stars forming within. This cluster contains hundreds of young, hot, massive stars, and lies some 5500 light-years away in the constellation of Vela (The Sails).

The central area of RCW 38 is visible here as a bright, blue-tinted region, an area inhabited by numerous very young stars and protostars that are still in the process of forming. The intense radiation pouring out from these newly born stars causes the surrounding gas to glow brightly. This is in stark contrast to the streams of cooler cosmic dust winding through the region, which glow gently in dark shades of red and orange. The contrast creates this spectacular scene — a piece of celestial artwork.

Previous images of this region taken in optical wavelengths are strikingly different — optical images appear emptier of stars due to dust and gas blocking our view of the cluster. Observations in the infrared, however, allow us to peer through the dust that obscures the view in the optical and delve into the heart of this star cluster.

HAWK-I is installed on Unit Telescope 4 (Yepun) of the VLT, and operates at near-infrared wavelengths. It has many scientific roles, including obtaining images of nearby galaxies or large nebulae as well as individual stars and exoplanets. GRAAL is an adaptive optics module which helps HAWK-I to produce these spectacular images. It makes use of four laser beams projected into the night sky, which act as artificial reference stars, used to correct for the effects of atmospheric turbulence — providing a sharper image.

This image was captured as part of a series of test observations — a process known as science verification — for HAWK-I and GRAAL. These tests are an integral part of the commissioning of a new instrument on the VLT, and include a set of typical scientific observations that verify and demonstrate the capabilities of the new instrument.

More Information

The Principal Investigator of the observing proposal which led this spectacular image was Koraljka Muzic (CENTRA, University of Lisbon, Portugal). Her collaborators were Joana Ascenso (CENTRA, University of Porto, Portugal), Amelia Bayo (University of Valparaiso, Chile), Arjan Bik (Stockholm University, Sweden), Hervé Bouy (Laboratoire d’astrophysique de Bordeaux, France), Lucas Cieza (University Diego Portales, Chile), Vincent Geers (UKATC, UK), Ray Jayawardhana (York University, Canada), Karla Peña Ramírez (University of Antofagasta, Chile), Rainer Schoedel (Instituto de Astrofísica de Andalucía, Spain), and Aleks Scholz (University of St Andrews, UK).

The Science Verification of HAWK-I with the GRAAL adaptive optics module was presented in an article in ESO’s quarterly journal The Messenger entitled HAWK-I GRAAL Science Verification.

The science verification team was composed of Bruno Leibundgut, Pascale Hibon, Harald Kuntschner, Cyrielle Opitom, Jerome Paufique, Monika Petr-Gotzens, Ralf Siebenmorgen, Elena Valenti and Anita Zanella, all from ESO.

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 15 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a strategic partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.



Calum Turner
ESO Assistant Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6670

Source: ESO/News  

Wednesday, July 11, 2018

NASA's Webb Space Telescope to Inspect Atmospheres of Gas Giant Exoplanet

This is an artist's impression of the Jupiter-size extrasolar planet, HD 189733b, being eclipsed by its parent star. Astronomers using the Hubble Space Telescope have measured carbon dioxide and carbon monoxide in the planet's atmosphere. The planet is a "hot Jupiter," which is so close to its star that it completes an orbit in only 2.2 days. The planet is too hot for life as we know it. But under the right conditions, on a more Earth-like world, carbon dioxide can indicate the presence of extraterrestrial life. This observation demonstrates that chemical biotracers can be detected by space telescope observations. Credits: ESA, NASA, M. Kornmesser (ESA/Hubble), and STScI

In April 2018, NASA launched the Transiting Exoplanet Survey Satellite (TESS). Its main goal is to locate Earth-sized planets and larger “super-Earths” orbiting nearby stars for further study. One of the most powerful tools that will examine the atmospheres of some planets that TESS discovers will be NASA’s James Webb Space Telescope. Since observing small exoplanets with thin atmospheres like Earth will be challenging for Webb, astronomers will target easier, gas giant exoplanets first.

Some of Webb’s first observations of gas giant exoplanets will be conducted through the Director’s Discretionary Early Release Science program. The transiting exoplanet project team at Webb’s science operations center is planning to conduct three different types of observations that will provide both new scientific knowledge and a better understanding of the performance of Webb’s science instruments.

“We have two main goals. The first is to get transiting exoplanet datasets from Webb to the astronomical community as soon as possible. The second is to do some great science so that astronomers and the public can see how powerful this observatory is,” said Jacob Bean of the University of Chicago, a co-principal investigator on the transiting exoplanet project.

“Our team’s goal is to provide critical knowledge and insights to the astronomical community that will help to catalyze exoplanet research and make the best use of Webb in the limited time we have available,” added Natalie Batalha of NASA Ames Research Center, the project’s principal investigator.

Transit – An atmospheric spectrum

When a planet crosses in front of, or transits, its host star, the star’s light is filtered through the planet’s atmosphere. Molecules within the atmosphere absorb certain wavelengths, or colors, of light. By splitting the star’s light into a rainbow spectrum, astronomers can detect those sections of missing light and determine what molecules are in the planet’s atmosphere.

For these observations, the project team selected WASP-79b, a Jupiter-sized planet located about 780 light-years from Earth. The team expects to detect and measure the abundances of water, carbon monoxide, and carbon dioxide in WASP-79b. Webb also might detect new molecules not yet seen in exoplanet atmospheres.

Phase curve – A weather map

Planets that orbit very close to their stars tend to become tidally locked. One side of the planet permanently faces the star while the other side faces away, just as one side of the Moon always faces the Earth. When the planet is in front of the star, we see its cooler backside. But as it orbits the star, more and more of the hot day-side comes into view. By observing an entire orbit, astronomers can observe those variations (called a phase curve) and use the data to map the planet’s temperature, clouds, and chemistry as a function of longitude.

The team will observe a phase curve of the “hot Jupiter” known as WASP-43b, which orbits its star in less than 20 hours. By looking at different wavelengths of light, they can sample the atmosphere to different depths and obtain a more complete picture of its structure. “We have already seen dramatic and unexpected variations for this planet with Hubble and Spitzer. With Webb we will reveal these variations in significantly greater detail to understand the physical processes that are responsible,” said Bean.

Eclipse – A planet’s glow

The greatest challenge when observing an exoplanet is that the star’s light is much brighter, swamping the faint light of the planet. To get around this problem, one method is to observe a transiting planet when it disappears behind the star, not when it crosses in front of the star. By comparing the two measurements, one taken when both star and planet are visible, and the other when only the star is in view, astronomers can calculate how much light is coming from the planet alone.

This technique works best for very hot planets that glow brightly in infrared light. The team plans to study WASP-18b, a planet that is baked to a temperature of almost 4,800 degrees Fahrenheit (2,900 K). Among other questions, they hope to determine whether the planet’s stratosphere exists due to the presence of titanium oxide, vanadium oxide, or some other molecule.

Habitable planets

Ultimately, astronomers want to use Webb to study potentially habitable planets. In particular, Webb will target planets orbiting red dwarf stars since those stars are smaller and dimmer, making it easier to tease out the signal from an orbiting planet. Red dwarfs are also the most common stars in our galaxy.

“TESS should locate more than a dozen planets orbiting in the habitable zones of red dwarfs, a few of which might actually be habitable. We want to learn whether those planets have atmospheres and Webb will be the one to tell us,” said Kevin Stevenson of the Space Telescope Science Institute, a co-principal investigator on the project. “The results will go a long way towards answering the question of whether conditions favorable to life are common in our galaxy.”

The James Webb Space Telescope is the world’s premier infrared space observatory of the next decade. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, the European Space Agency (ESA) and the Canadian Space Agency (CSA).


Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

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Tuesday, July 10, 2018

Uranus Giant Impacts: Low Angular Momentum

Image credit: NASA/JPL/STScI

Scientists have always wondered how Uranus got tilted so much that it spins on its side, and now research on the planet’s early formation gives us new insight. Four billion years ago, scientists believe a young proto-planet of rock and ice collided with Uranus, causing its extreme tilt. Instead of rotating like a top spinning nearly upright, as Earth does, the planet “rolls” on its side as it circles the sun.

The research team, led by Durham University, UK, in collaboration with scientists at NASA's Ames Research Center in Silicon Valley, used advanced computing techniques to create the most detailed simulation to date of the suspected impact.
A simulation of the most likely Uranus-impact scenario that caused today’s tilted orbit, according to new, highly detailed simulations. Light gray represents ice materials from Uranus, while dark gray represents rock materials from Uranus. Purple represents ice materials from the impactor, while brown represents rock from the impactor. Light blue represents Uranus’ atmosphere. Credits: Jacob Kegerreis / Durham University

Through more than 50 simulations of impact scenarios using a supercomputer, this research group determined that an object at least twice the mass of Earth likely impacted the young planet with a grazing blow. The collision was so strong it reshaped the entire planet and pushed it onto its side. But, the collision was likely not strong enough to blast the planet’s atmosphere off into space or significantly change its orbit around the Sun. This research was the first of its type to take the planet’s atmosphere into account in its simulations of the impact. This helped the scientists better define what that event might have looked like.

The impact might have left molten ice and lopsided lumps of rock within the planet, perhaps explaining its tilted and off-center magnetic field, too. Rock and ice thrown into orbit would have then clumped together to form the rings and moons around Uranus, now in its newly established rotation.

But this discovery goes beyond explaining how Uranus became what it is today. It helps us on our search to understand other planets outside our solar system – exoplanets. Uranus is a medium-size, gaseous planet with a rocky and icy core. Based on findings from the Kepler space telescope, the more common type of exoplanet is very similar to Uranus. Learning about this impact helps us understand how similar collisions lead to the formation of other planets, and what this means for their ability to support life.

The findings, published in The Astrophysical Journal, paint a riveting picture of Uranus’ early tumultuous years, and gives us the tools to understand planets like it throughout the cosmos.

Author: Frank Tavares

Members of the news media interested in learning more about this research should refer to the NASA Ames Media Contacts page to get in touch.

Editor: Abigail Tabor

Source: NASA/Ames

Monday, July 09, 2018

Distant Quasar Providing Clues to Early-Universe Conditions

VLBA image of the quasar P352–15, at a distance of nearly 13 billion light-years from Earth. Three main components of the object are seen, with two of them showing further substructure. Credit: Momjian, et al.; B. Saxton (NRAO/AUI/NSF). Hi-res image

Artist's conception of distant quasar P352-15, with disk of material orbiting the black hole and jet of fast-moving particles ejected into space. Credit: Robin Dienel, courtesy of Carnegie Institution for Science. Hi-res image

Astronomers using the National Science Foundation’s Very Long Baseline Array (VLBA) have made an image revealing tantalizing details of a quasar nearly 13 billion light-years from Earth — an object that may provide important clues about the physical processes at work in the Universe’s first galaxies.

The scientists studied a quasar called PSO J352.4034-15.3373 (P352-15), an unusually bright emitter of radio waves for an object so distant. The extremely sharp radio “vision” of the VLBA showed the object split into three major components, two of which show further subdivision. The components are spread over a distance of only about 5,000 light-years.

Quasars are galaxies with supermassive black holes at their cores — black holes millions or billions of times more massive than the Sun. The powerful gravitational pull of such a black hole draws in nearby material, which forms a rotating disk around the massive object. The rapidly-spinning disk spews jets of particles moving outward at speeds approaching that of light. These energetic “engines” are bright emitters of light and radio waves.

“This is the most detailed image yet of such a bright galaxy at this great distance,” said Emmanuel Momjian, of the National Radio Astronomy Observatory (NRAO).

“There is a dearth of known strong radio emitters from the Universe’s youth and this is the brightest radio quasar at that epoch by a factor of 10,” said Eduardo Banados of the Carnegie Institution for Science in Pasadena, California.

“We are seeing P352-15 as it was when the Universe was less than a billion years old, or only about 7 percent of its current age,” said Chris Carilli, of NRAO. “This is near the end of a period when the first stars and galaxies were re-ionizing the neutral hydrogen atoms that pervaded intergalactic space. Further observations may allow us to use this quasar as a background ‘lamp’ to measure the amount of neutral hydrogen remaining at that time,” he added.

The astronomers said the three major components of P352-15 can be explained in one of two ways. One explanation is that they’re seeing the bright core of the quasar, corresponding to the location of the supermassive black hole itself, at one end, and the two other bright spots are parts of a one-sided jet. The other possibility is that their middle object is the core, and the other objects are jets ejected in opposite directions. Because one of the end objects is closest to the position of the quasar as seen with visible-light telescopes, they consider the one-sided jet to be the more likely explanation.

The one-sided jet explanation raises the exciting possibility that astronomers may be able to detect and measure the expansion of the jet by observing P352-15 over several years.

“This quasar may be the most distant object in which we could measure the speed of such a jet,” Momjian said.

If, instead, the middle object is the core, with two oppositely-moving jets, its small size suggests that it may be very young or be embedded in dense gas that is slowing the jets’ expansion.

Planned future observations will tell which scenario is accurate, the scientists said.

“This quasar’s brightness and its great distance make it a unique tool to study the conditions and processes that prevailed in the first galaxies in the Universe,” Carilli said. “We look forward to unraveling more of its mysteries,” he added.

Momjian, Banados, and Carilli worked with Fabian Walter of the Max Planck Institute for Astronomy in Heidelberg, Germany; and Bram Venemans, also of the Max Planck Institute. The astronomers are reporting their findings in the Astrophysical Journal.

The Long Baseline Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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in ApJ: Resolving the Powerful Radio-loud Quasar at z ~ 6:

In APJ Letters: A Powerful Radio-loud Quasar at the End of Cosmic Reionization: