Old-looking galaxy in a young universe: Astronomers find dust in the early universe

This spectacular view from the NASA/ESA Hubble Space Telescope shows the rich galaxy cluster Abell 1689. The huge concentration of mass bends light coming from more distant objects and can increase their total apparent brightness and make them visible. One such object, A1689-zD1, is located in the box -- although it is still so faint that it is barely seen in this picture. New observations with ALMA and ESO's VLT have revealed that this object is a dusty galaxy seen when the Universe was just 700 million years old.  Credit: NASA; ESA; L. Bradley (Johns Hopkins University); R. Bouwens (University of California, Santa Cruz); H. Ford (Johns Hopkins University); and G. Illingworth (University of California, Santa Cruz)

Dust plays an extremely important role in the universe -- both in the formation of planets and new stars. But dust was not there from the beginning and the earliest galaxies had no dust, only gas. Now an international team of astronomers, led by researchers from the Niels Bohr Institute, has discovered a dust-filled galaxy from the very early universe. The discovery demonstrates that galaxies were very quickly enriched with dust particles containing elements such as carbon and oxygen, which could form planets. The results are published in the scientific journal, Nature.

Cosmic dust are smoke-like particles made up of either carbon (fine soot) or silicates (fine sand). The dust is comprised primarily of elements such as carbon, silicon, magnesium, iron and oxygen. The elements are synthesised by the nuclear combustion process in stars and driven out into space when the star dies and explodes. In space, they gather in clouds of dust and gas, which form new stars, and for each generation of new stars, more elements are formed. This is a slow process and in the very earliest galaxies in the history of the universe, dust had not yet formed.

But now a team of researchers have discovered a very distant galaxy that contains a large amount of dust, changing astronomers' previous calculations of how quickly the dust was formed.

"It is the first time dust has been discovered in one of the most distant galaxies ever observed -- only 700 million years after the Big Bang. It is a galaxy of modest size and yet it is already full of dust. This is very surprising and it tells us that ordinary galaxies were enriched with heavier elements far faster than expected," explains Darach Watson, an astrophysicist with the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Darach Watson led the project, with Lise Christensen from the Dark Cosmology Centre and researchers from Sweden, Scotland, France and Italy.

Lucky location

Because the galaxy is very distant and therefore incredibly faint, it would not usually be detectable from Earth. But a fortunate circumstance means the light from it has been amplified. This is because a large cluster of galaxies called Abell 1689, lies between the galaxy and Earth. The light is refracted by the gravity of the galaxy cluster, thus amplifying the distant galaxy. The phenomenon is called gravitational lensing and it works like a magnifying glass.

"We looked for the most distant galaxies in the universe. Based on the colours of the light observed with the Hubble Space Telescope we can see which galaxies could be very distant. Using observations from the very sensitive instrument, the X-shooter spectrograph on the Large Telescope, VLT in Chile, we measured the galaxy's spectrum and from that calculated its redshift, i.e. the change in the light's wavelength as the object recedes from us. From the redshift we can calculate the galaxy's distance from us and it turned out to be, as we suspected, one of the most distant galaxies we know of to date," explains Lise Christensen, an astrophysicist at the Dark Cosmology Centre at the Niels Bohr Institute.

Early planet formation

Darach Watson explains that they then studied the galaxy with the ALMA telescopes, which can observe far-infrared wavelengths and then it became really interesting, because now they could see that the galaxy was full of dust. He explains that young stars in early galaxies emit hot ultraviolet light. The hot ultraviolet radiation heats the surrounding ice-cold dust, which then emits light in the far-infrared.

"It is this far-infrared light, which tells us that there is dust in the galaxy. It is very surprising and it is the first time that dust has been found in such an early galaxy. The process of star formation must therefore have started very early in the history of the universe and be associated with the formation of dust. The detection of large amounts of solid material shows that the galaxy was enriched very early with solids which are a prerequisite for the formation of complex molecules and planets," explains Darach Watson.

Now the researchers hope that future observations of a large number of distant galaxies using the ALMA telescopes could help unravel how frequently such evolved galaxies occur in this very early epoch of the history of the universe.

Source: University of Copenhagen - Niels Bohr Institute

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Space Hubble's Little Sombrero

         European Space Agency Credit: ESA/Hubble & NASA

Galaxies can take many shapes and be oriented any way relative to us in the sky. This can make it hard to figure out their actual morphology, as a galaxy can look very different from different viewpoints. A special case is when we are lucky enough to observe a spiral galaxy directly from its edge, providing us with a spectacular view like the one seen in this picture of the week.

This is NGC 7814, also known as the “Little Sombrero.” Its larger namesake, the Sombrero Galaxy, is another stunning example of an edge-on galaxy — in fact, the “Little Sombrero” is about the same size as its bright namesake at about 60,000 light-years across, but as it lies farther away, and so appears smaller in the sky.

NGC 7814 has a bright central bulge and a bright halo of glowing gas extending outwards into space. The dusty spiral arms appear as dark streaks. They consist of dusty material that absorbs and blocks light from the galactic center behind it. The field of view of this NASA/ESA Hubble Space Telescope image would be very impressive even without NGC 7814 in front; nearly all the objects seen in this image are galaxies as well. 

Source: Nasa

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NASA Observatories Take an Unprecedented Look into Superstar Eta Carinae

In this supercomputer simulation, the stars of Eta Carinae are shown as black dots. Lighter colors indicate greater densities in the stellar winds produced by each star. At closest approach, the fast wind of the smaller star carves a tunnel in the thicker wind of the larger star. Image Credit: NASA's Goddard Space Flight Center/T. Madura

Eta Carinae, the most luminous and massive stellar system within 10,000 light-years of Earth, is known for its surprising behavior, erupting twice in the 19th century for reasons scientists still don't understand. A long-term study led by astronomers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, used NASA satellites, ground-based telescopes and theoretical modeling to produce the most comprehensive picture of Eta Carinae to date. New findings include Hubble Space Telescope images that show decade-old shells of ionized gas racing away from the largest star at a million miles an hour, and new 3-D models that reveal never-before-seen features of the stars' interactions.

"We are coming to understand the present state and complex environment of this remarkable object, but we have a long way to go to explain Eta Carinae's past eruptions or to predict its future behavior," said Goddard astrophysicist Ted Gull, who coordinates a research group that has monitored the star for more than a decade.

Located about 7,500 light-years away in the southern constellation of Carina, Eta Carinae comprises two massive stars whose eccentric orbits bring them unusually close every 5.5 years. Both produce powerful gaseous outflows called stellar winds, which enshroud the stars and stymy efforts to directly measure their properties. Astronomers have established that the brighter, cooler primary star has about 90 times the mass of the sun and outshines it by 5 million times. While the properties of its smaller, hotter companion are more contested, Gull and his colleagues think the star has about 30 solar masses and emits a million times the sun's light.

Seen in blue light emitted by doubly ionized iron atoms (4,659 angstroms), these images of Eta Carinae were captured by Hubble's STIS instrument between 2010 and 2014. Gas shells created during the binary's 2003 close approach race outward at about 1 million mph (1.6 million km/h). Image Credit: NASA's Goddard Space Flight Center/T. Gull et al.

Speaking at a press conference at the American Astronomical Society meeting in Seattle on Wednesday, the Goddard researchers discussed recent observations of Eta Carinae and how they fit with the group's current understanding of the system.

At closest approach, or periastron, the stars are 140 million miles (225 million kilometers) apart, or about the average distance between Mars and the sun. Astronomers observe dramatic changes in the system during the months before and after periastron. These include X-ray flares, followed by a sudden decline and eventual recovery of X-ray emission; the disappearance and re-emergence of structures near the stars detected at specific wavelengths of visible light; and even a play of light and shadow as the smaller star swings around the primary.

During the past 11 years, spanning three periastron passages, the Goddard group has developed a model based on routine observations of the stars using ground-based telescopes and multiple NASA satellites. "We used past observations to construct a computer simulation, which helped us predict what we would see during the next cycle, and then we feed new observations back into the model to further refine it," said Thomas Madura, a NASA Postdoctoral Program Fellow at Goddard and a theorist on the Eta Carinae team.

According to this model, the interaction of the two stellar winds accounts for many of the periodic changes observed in the system. The winds from each star have markedly different properties: thick and slow for the primary, lean and fast for the hotter companion. The primary's wind blows at nearly 1 million mph and is especially dense, carrying away the equivalent mass of our sun every thousand years. By contrast, the companion's wind carries off about 100 times less material than the primary's, but it races outward as much as six times faster.

Madura's simulations, which were performed on the Pleiades supercomputer at NASA's Ames Research Center in Moffett Field, California, reveal the complexity of the wind interaction. When the companion star rapidly swings around the primary, its faster wind carves out a spiral cavity in the dense outflow of the larger star. To better visualize this interaction, Madura converted the computer simulations to 3-D digital models and made solid versions using a consumer-grade 3-D printer. This process revealed lengthy spine-like protrusions in the gas flow along the edges of the cavity, features that hadn't been noticed before.    

"We think these structures are real and that they form as a result of instabilities in the flow in the months around closest approach," Madura said. "I wanted to make 3-D prints of the simulations to better visualize them, which turned out to be far more successful than I ever imagined." A paper detailing this research has been submitted to the journal Monthly Notices of the Royal Astronomical Society.

The team detailed a few key observations that expose some of the system's inner workings. For the past three periastron passages, ground-based telescopes in Brazil, Chile, Australia and New Zealand have monitored a single wavelength of blue light emitted by helium atoms that have lost a single electron. According to the model, the helium emission tracks conditions in the primary star's wind. 

The Space Telescope Imaging Spectrograph (STIS) aboard Hubble captures a different wavelength of blue light emitted by iron atoms that have lost two electrons, which uniquely reveals where gas from the primary star is set aglow by the intense ultraviolet light of its companion. Lastly, X-rays from the system carry information directly from the wind collision zone, where the opposing winds create shock waves that heat the gas to hundreds of millions of degrees.

"Changes in the X-rays are a direct probe of the collision zone and reflect changes in how these stars lose mass," said Michael Corcoran, an astrophysicist with the Universities Space Research Association headquartered in Columbia, Maryland. He and his colleagues compared periastron emission measured over the past 20 years by NASA's Rossi X-ray Timing Explorer, which ceased operation in 2012, and the X-ray Telescope aboard NASA's Swift satellite. In July 2014, as the stars rushed toward each other, Swift observed a series of flares culminating in the brightest X-ray emission yet seen from Eta Carinae. This implies a change in mass loss by one of the stars, but X-rays alone cannot determine which one.

Goddard's Mairan Teodoro led the ground-based campaign tracking the helium emission. "The 2014 emission is nearly identical to what we saw at the previous periastron in 2009, which suggests the primary wind has been constant and that the companion's wind is responsible for the X-ray flares," he explained.

After NASA astronauts repaired the Hubble Space Telescope's STIS instrument in 2009, Gull and his collaborators requested to use it to observe Eta Carinae. By separating the stars' light into a rainbow-like spectrum, STIS reveals the chemical make-up of their environment. But the spectrum also showed wispy structures near the stars that suggested the instrument could be used to map a region close to the binary system in never-before-seen detail.

STIS views its targets through a single narrow slit to limit contamination from other sources. Since December 2010, Gull's team has regularly mapped a region centered on the binary by capturing spectra at 41 different locations, an effort similar to building up a panoramic picture from a series of snapshots. The view spans about 430 billion miles (670 billion km), or about 4,600 times the average Earth-sun distance.

The resulting images, revealed for the first time on Wednesday, show that the doubly ionized iron emission comes from a complex gaseous structure nearly a tenth of a light-year across, which Gull likens to Maryland blue crab. By stepping through the STIS images, vast shells of gas representing the crab's "claws" can be seen racing away from the stars with measured speeds of about 1 million mph (1.6 million km/h). With each close approach, a spiral cavity forms in the larger star's wind and then expands outward along with it, creating the moving shells.
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"These gas shells persist over thousands of times the distance between Earth and the sun," Gull explained. "Backtracking them, we find the shells began moving away from the primary star about 11 years or three periastron passages ago, providing us with an additional way to glimpse what occurred in the recent past."

When the stars approach, the companion becomes immersed in the thickest part of the primary's wind, which absorbs its UV light and prevents the radiation from reaching the distant gas shells. Without this energy to excite it, the doubly ionized iron stops emitting light and the crab structure disappears at this wavelength. Once the companion swings around the primary and clears the densest wind, its UV light escapes, re-energizes iron atoms in the shells, and the crab returns. 

Eta Carinae's great eruption in the 1840s created the billowing Homunculus Nebula, imaged here by Hubble. Now about a light-year long, the expanding cloud contains enough material to make at least 10 copies of our sun. Astronomers cannot yet explain what caused this eruption. Image Credit: NASA, ESA, and the Hubble SM4 ERO Team

Both of the massive stars of Eta Carinae may one day end their lives in supernova explosions. For stars, mass is destiny, and what will determine their ultimate fate is how much matter they can lose -- through stellar winds or as-yet-inexplicable eruptions -- before they run out of fuel and collapse under their own weight.

For now, the researchers say, there is no evidence to suggest an imminent demise of either star. They are exploring the rich dataset from the 2014 periastron passage to make new predictions, which will be tested when the stars again race together in February 2020.

NASA is exploring our solar system and beyond to understand the universe and our place in it. We seek to unravel the secrets of our universe, its origins and evolution, and search for life among the stars.

Source: Nasa

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The state of astronomy before Hubble and the difficulties of observing from the ground that drove the need for a space telescope' Videos

This video looks at the state of astronomy before Hubble and the difficulties of observing from the ground that drove the need for a space telescope. Image Credit: Space Telescope Science Institute

Dr. Nancy Grace Roman, first chief astronomer at NASA’s then Office of Space Science and the one who set up NASA’s astronomy program in the 1960s, speaks about the importance of building and launching a space telescope instead of building duplicates of the Earth-based Palomar 200-inch telescope.

"Astronomers have wanted for generations actually to get a telescope above the atmosphere,” Roman said. “I like to describe the atmosphere being something like looking through an old stained glass window… The glass has defects in it and that sort of keeps you from getting a sharp picture and the atmosphere also has defects." 

"The very sharp images it would produce would allow you to see things that were much fainter than would ever be possible from the ground," said C. Robert O'Dell, of Vanderbilt University in Nashville, Tennessee. O'Dell leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of the iconic Ring Nebula.
The video addresses several challenges at the time of Hubble's creation, including digital imaging at a time when the industry was in its infancy. The video also speaks on how the telescope has far exceeded its initial life-span.

The 4 minute and 23 second video was produced by STScI. The "Hubble 25th Anniversary" video series is available in HQ, large and small Quicktime formats, HD, large and small WMV formats, and HD, large and small Xvid formats.

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Source: Nasa Hubble

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Record-breaking black hole outburst detected

An image of a simulation of the gas cloud’s encounter with Sgr A*. The blue lines mark the orbits of the so-called “S” stars that are in close orbits around the supermassive black hole.
Credit: Image by ESO/MPE/Marc Schartmann

Last September, after years of watching, a team of scientists led by Amherst College astronomy professor Daryl Haggard observed and recorded the largest-ever flare in X-rays from a supermassive black hole at the center of the Milky Way. The astronomical event, which was detected by NASA's Chandra X-ray Observatory, puts the scientific community one step closer to understanding the nature and behavior of supermassive black holes.

Haggard and her colleagues discussed the flare today during this year's meeting of the American Astronomical Society in Seattle.

Supermassive black holes are the largest of black holes, and all large galaxies have one. The one at the center of our galaxy, the Milky Way, is called Sagittarius A* (or, Sgr A*, as it is called), and scientists estimate that it contains about four and a half million times the mass of our Sun.

Scientists working with Chandra have observed Sgr A* repeatedly since the telescope was launched into space in 1999. Haggard and fellow astronomers were originally using Chandra to see if Sgr A* would consume parts of a cloud of gas, known as G2.

"Unfortunately, the G2 gas cloud didn't produce the fireworks we were hoping for when it got close to Sgr A*," she said. "However, nature often surprises us and we saw something else that was really exciting."

Haggard and her team detected an X-ray outburst last September that was 400 times brighter than the usual X-ray output from Sgr A*. This "megaflare" was nearly three times brighter than the previous record holder that was seen in early 2012. A second enormous X-ray flare, 200 times brighter than Sgr A* in its quiet state, was observed with Chandra on October 20, 2014.

Haggard and her team have two main ideas about what could be causing Sgr A* to erupt in this extreme way. One hypothesis is that the gravity of the supermassive black hole has torn apart a couple of asteroids that wandered too close. The debris from such a "tidal disruption" would become very hot and produce X-rays before disappearing forever across the black hole's point of no return (called the "event horizon").

"If an asteroid was torn apart, it would go around the black hole for a couple of hours -- like water circling an open drain -- before falling in," said colleague and co-principal investigator Fred Baganoff of the Massachusetts Institute of Technology in Cambridge, MA. "That's just how long we saw the brightest X-ray flare last, so that is an intriguing clue for us to consider."

If that theory holds up, it means astronomers have found evidence for the largest asteroid ever to be torn apart by the Milky Way's black hole.

Another, different idea is that the magnetic field lines within the material flowing towards Sgr A* are packed incredibly tightly. If this were the case, these field lines would occasionally interconnect and reconfigure themselves. When this happens, their magnetic energy is converted into the energy of motion, heat and the acceleration of particles -- which could produce a bright X-ray flare. Such magnetic flares are seen on the Sun, and the Sgr A* flares have a similar pattern of brightness levels to the solar events.

"At the moment, we can't distinguish between these two very different ideas," said Haggard. "It's exciting to identify tensions between models and to have a chance to resolve them with present and future observations."

In addition to the giant flares, Haggard and her team also collected more data on a magnetar -- a neutron star with a strong magnetic field -- located close to Sgr A*. This magnetar is undergoing a long X-ray outburst, and the Chandra data are allowing astronomers to better understand this unusual object.

As for the G2: Astronomers estimate that the gas cloud made its closest approach -- still about 15 billion miles away from the edge of the black hole -- in the spring of 2014. The researchers estimate the record breaking X-ray flares were produced about a hundred times closer to the black hole, making it very unlikely that the Chandra flares were associated with G2.

Source: Amherst College

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Hubble goes high def to revisit the iconic ‘Pillars of Creation'

NASA's Hubble Space Telescope has revisited the famous Pillars of Creation, revealing a sharper and wider view of the structures in this visible-light image. Astronomers combined several Hubble exposures to assemble the wider view. The towering pillars are about 5 light-years tall. The dark, finger-like feature at bottom right may be a smaller version of the giant pillars. The new image was taken with Hubble's versatile and sharp-eyed Wide Field Camera 3. The pillars are bathed in the blistering ultraviolet light from a grouping of young, massive stars located off the top of the image. Streamers of gas can be seen bleeding off the pillars as the intense radiation heats and evaporates it into space. Denser regions of the pillars are shadowing material beneath them from the powerful radiation. Stars are being born deep inside the pillars, which are made of cold hydrogen gas laced with dust. The pillars are part of a small region of the Eagle Nebula, a vast star-forming region 6,500 light-years from Earth. The colors in the image highlight emission from several chemical elements. Oxygen emission is blue, sulfur is orange, and hydrogen and nitrogen are green. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Although NASA's Hubble Space Telescope has taken many breathtaking images of the universe, one snapshot stands out from the rest: the iconic view of the so-called "Pillars of Creation." The jaw-dropping photo, taken in 1995, revealed never-before-seen details of three giant columns of cold gas bathed in the scorching ultraviolet light from a cluster of young, massive stars in a small region of the Eagle Nebula, or M16.

Though such butte-like features are common in star-forming regions, the M16 structures are by far the most photogenic and evocative. The Hubble image is so popular that it has appeared in movies and television shows, on tee-shirts and pillows, and even on a postage stamp.

And now, in celebration of its 25th anniversary, Hubble has revisited the famous pillars, providing astronomers with a sharper and wider view. As a bonus, the pillars have been photographed in near-infrared light, as well as visible light. The infrared view transforms the pillars into eerie, wispy silhouettes seen against a background of myriad stars. That's because the infrared light penetrates much of the gas and dust, except for the densest regions of the pillars. Newborn stars can be seen hidden away inside the pillars. The new images are being unveiled at the American Astronomical Society meeting in Seattle, Washington.

Although the original image was dubbed the Pillars of Creation, the new image hints that they are also pillars of destruction. "I'm impressed by how transitory these structures are. They are actively being ablated away before our very eyes. The ghostly bluish haze around the dense edges of the pillars is material getting heated up and evaporating away into space. We have caught these pillars at a very unique and short-lived moment in their evolution," explained Paul Scowen of Arizona State University in Tempe, who, with astronomer Jeff Hester, formerly of Arizona State University, led the original Hubble observations of the Eagle Nebula.

The infrared image shows that the very ends of the pillars are dense knots of gas and dust, and they shadow the gas below them, creating the long, column-like structures. The gas in between the pillars has long since been blown away by the ionizing winds from the central star cluster located above the pillars.

At the top edge of the left-hand pillar, a gaseous fragment has been heated up and is flying away from the structure, underscoring the violent nature of star-forming regions. "These pillars represent a very dynamic, active process," Scowen said. "The gas is not being passively heated up and gently wafting away into space. The gaseous pillars are actually getting ionized (a process by which electrons are stripped off of atoms) and heated up by radiation from the massive stars. And then they are being eroded by the stars' strong winds (barrage of charged particles), which are sandblasting away the tops of these pillars."

When Scowen and Hester used Hubble to make the initial observations of the Eagle Nebula in 1995, astronomers had seen the pillar-like structures in ground-based images, but not in detail. They knew that the physical processes are not unique to the Eagle Nebula because star birth takes place across the universe. But at a distance of just 6,500 light-years, M16 is the most dramatic nearby example, as the team soon realized.

As Scowen was piecing together the Hubble exposures of the Eagle, he was amazed at what he saw. "I called Jeff Hester on his phone and said, 'You need to get here now,'" Scowen recalled. "We laid the pictures out on the table, and we were just gushing because of all the incredible detail that we were seeing for the very first time."

The first features that jumped out at the team in 1995 were the streamers of gas seemingly floating away from the columns. Astronomers had previously debated what effect nearby massive stars would have on the surrounding gas in stellar nurseries. "There is only one thing that can light up a neighborhood like this: massive stars kicking out enough horsepower in ultraviolet light to ionize the gas clouds and make them glow," Scowen said. 

"Nebulous star-forming regions like M16 are the interstellar neon signs that say, 'We just made a bunch of massive stars here.' This was the first time we had directly seen observational evidence that the erosionary process, not only the radiation but the mechanical stripping away of the gas from the columns, was actually being seen."

By comparing the 1995 and 2014 pictures, astronomers also noticed a lengthening of a narrow jet-like feature that may have been ejected from a newly forming star. The jet looks like a stream of water from a garden hose. Over the intervening 19 years, this jet has stretched farther into space, across an additional 60 billion miles, at an estimated speed of about 450,000 miles per hour.

Our Sun probably formed in a similar turbulent star-forming region. There is evidence that the forming solar system was seasoned with radioactive shrapnel from a nearby supernova. That means that our Sun was formed as part of a cluster that included stars massive enough to produce powerful ionizing radiation, such as is seen in the Eagle Nebula. "That's the only way the nebula from which the Sun was born could have been exposed to a supernova that quickly, in the short period of time that represents, because supernovae only come from massive stars, and those stars only live a few tens of millions of years," Scowen explained. 

"What that means is when you look at the environment of the Eagle Nebula or other star-forming regions, you're looking at exactly the kind of nascent environment that our Sun formed in."

Source: Space Telescope Science Institute (STScI)

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