Most distant quasarA team of European astronomers, including UK astronomers, have
discovered a bright quasar that has been beaming light since the
Universe was a mere 770 million years old.
The brilliant beacon, named ULAS J1120+0641, is powered by a black hole with a mass two billion times that of the Sun. Located at a redshift – a term relating to astronomical distances – of 7.1, its light has taken 12.9 billion years to reach us. The next most distant quasar is seen at 870 million years after the big bang, or a redshift of 6.4, although gamma ray bursts have been detected at greater distances of 8.6 and 8.2 redshifts.
“We think there are only about 100 bright quasars with redshift higher than 7 over the whole sky,” says Daniel Mortlock of Imperial College London, and lead author of the paper that appears in the 30 June edition of the journal Nature. “Finding this object required a painstaking search, but it was worth the effort to be able to unravel some of the mysteries of the early Universe.”
The quasar was initially spotted using WFCAM, an infrared camera on the UK Infrared Telescope in Hawaii, and confirmed by observations made with the Liverpool Telescope, Gemini North telescope and the European Southern Observatory’s Very Large Telescope. Over 10 million sources were analysed before the quasar was discovered, but finding such a high mass black hole is difficult to explain so early in the Universe.
"The simplest models of black hole formation just can't create a two billion solar mass black hole so soon after the big bang, so its existence is something of a problem for theoretical physicists," Mortlock tells Astronomy Now, who adds that explanations for its existence require the first stars to be extremely massive or require black holes merging much more often than generally believed. "Given how hard it was to find even one bright quasar this early in the Universe's history, there are no immediate prospects for making the sort of "population census" that might reveal more about their formation mechanisms, so I think this will remain an unanswered question for some time."
The key insight the quasar has provided so far is into conditions in the early Universe, specifically to a time period known as the reionization epoch which persisted from around 150 to 800 million years after the big bang, when intense ultraviolet radiation from the first stars began breaking apart the neutral hydrogen gas that permeated the early Universe.
"The way the light from the quasar is absorbed by the hydrogen gas immediately in front of it implies that it was maybe 10 or 50 percent neutral at that time – whereas even "just" 100 million years later it was only 0.1 percent neutral," explains Mortlock. "These inferences will become more coherent as we find more such objects, but the key thing about this quasar is that it is the first bright source we've found that we're seeing in a fairly un-ionized (i.e. neutral) Universe."
Powered by a black hole of 2 billion solar masses, the quasar appears as it did 12.9 billion years ago, when the universe as humans know it was just beginning to emerge from the Big Bang.The supermassive black hole is pulling enormous clumps of matter into its gravitational clutches. As a result, the quasar emits 60 trillion times as much light as the sun, an international team reports in the June 30 Nature.
The team identified the object from the U.K. Infrared Telescope’s Infrared Deep Sky Survey, which probes 5 percent of the sky in infrared wavelengths. Daniel Mortlock of Imperial College London, an author of the study, likens the process to panning for gold. “You see many shiny things in the infrared, but not all of them are nuggets,” he says. “We got a big nugget this time.”
Already, the uncharismatically named ULAS J1120+0641 is presenting both clues and puzzles about the early universe.
“The surprising thing is that this object is right at the farthest possible distance we could see,” Mortlock says. The object is so distant that because of the time it took the quasar’s light to reach Earth, astronomers are seeing it as it was just 770 million years after the Big Bang. While theorists had predicted quasars could form that soon after the Big Bang, none had anticipated seeing one so large in the embryonic universe.
“It is like finding a 6-foot-tall child in kindergarten,” says astrophysicist Marta Volonteri, at the University of Michigan in Ann Arbor.
Prevailing theories suggest that black holes form either from the tiny, dense objects left behind after the deaths of early stars, or they form from the direct collapse of cosmic gases. For the first theory to be correct, Volonteri says, ULAS J1120+0641 would have needed to begin growing before the beginning of time, suggesting that the direct collapse theory is better supported by the quasar’s discovery.
Scientists think there are maybe 100 distant, bright objects like the newly discovered quasar sprinkled throughout the entire sky, and astrophysicist Avi Loeb, at Harvard University, says he hopes sky surveys will find more of them. These quasars, if they exist, could act as beacons of light that help astronomers study the early universe. ULAS J1120+0641 has a luminosity of 6.3 × 1013L⊙,i.e.around 10^40 watts and hosts a black hole with a mass of 2 × 109M⊙ (where L⊙ and M⊙ are the luminosity and mass of the Sun).
The Most Powerful Quasar in Local UNiverse
Material has been discovered moving at nearly 10% the speed of light away from the centre of the nearby quasar PDS456 - the most powerful object in the local universe. PDS 456 is a nearby (z = 0.184), luminous (Lbol ~ 1047 erg s–1) type I quasar. Like all quasars, PDS456 is thought to be powered by matter converting into energy when material is swallowed by a supermassive black hole. New observations show that its energy output is so large that it is "choking on its food" and radiation is literally blowing the top off the inner region of the disc of in-falling material that surrounds the black hole. The discovery is being announced on Wednesday 9th April at the UK/Ireland National Astronomy Meeting in Dublin on behalf of a team from the University of Leicester and the NASA Goddard Space Flight Center.
The brilliant beacon, named ULAS J1120+0641, is powered by a black hole with a mass two billion times that of the Sun. Located at a redshift – a term relating to astronomical distances – of 7.1, its light has taken 12.9 billion years to reach us. The next most distant quasar is seen at 870 million years after the big bang, or a redshift of 6.4, although gamma ray bursts have been detected at greater distances of 8.6 and 8.2 redshifts.
“We think there are only about 100 bright quasars with redshift higher than 7 over the whole sky,” says Daniel Mortlock of Imperial College London, and lead author of the paper that appears in the 30 June edition of the journal Nature. “Finding this object required a painstaking search, but it was worth the effort to be able to unravel some of the mysteries of the early Universe.”
The quasar was initially spotted using WFCAM, an infrared camera on the UK Infrared Telescope in Hawaii, and confirmed by observations made with the Liverpool Telescope, Gemini North telescope and the European Southern Observatory’s Very Large Telescope. Over 10 million sources were analysed before the quasar was discovered, but finding such a high mass black hole is difficult to explain so early in the Universe.
"The simplest models of black hole formation just can't create a two billion solar mass black hole so soon after the big bang, so its existence is something of a problem for theoretical physicists," Mortlock tells Astronomy Now, who adds that explanations for its existence require the first stars to be extremely massive or require black holes merging much more often than generally believed. "Given how hard it was to find even one bright quasar this early in the Universe's history, there are no immediate prospects for making the sort of "population census" that might reveal more about their formation mechanisms, so I think this will remain an unanswered question for some time."
The key insight the quasar has provided so far is into conditions in the early Universe, specifically to a time period known as the reionization epoch which persisted from around 150 to 800 million years after the big bang, when intense ultraviolet radiation from the first stars began breaking apart the neutral hydrogen gas that permeated the early Universe.
"The way the light from the quasar is absorbed by the hydrogen gas immediately in front of it implies that it was maybe 10 or 50 percent neutral at that time – whereas even "just" 100 million years later it was only 0.1 percent neutral," explains Mortlock. "These inferences will become more coherent as we find more such objects, but the key thing about this quasar is that it is the first bright source we've found that we're seeing in a fairly un-ionized (i.e. neutral) Universe."
Powered by a black hole of 2 billion solar masses, the quasar appears as it did 12.9 billion years ago, when the universe as humans know it was just beginning to emerge from the Big Bang.The supermassive black hole is pulling enormous clumps of matter into its gravitational clutches. As a result, the quasar emits 60 trillion times as much light as the sun, an international team reports in the June 30 Nature.
The team identified the object from the U.K. Infrared Telescope’s Infrared Deep Sky Survey, which probes 5 percent of the sky in infrared wavelengths. Daniel Mortlock of Imperial College London, an author of the study, likens the process to panning for gold. “You see many shiny things in the infrared, but not all of them are nuggets,” he says. “We got a big nugget this time.”
Already, the uncharismatically named ULAS J1120+0641 is presenting both clues and puzzles about the early universe.
“The surprising thing is that this object is right at the farthest possible distance we could see,” Mortlock says. The object is so distant that because of the time it took the quasar’s light to reach Earth, astronomers are seeing it as it was just 770 million years after the Big Bang. While theorists had predicted quasars could form that soon after the Big Bang, none had anticipated seeing one so large in the embryonic universe.
“It is like finding a 6-foot-tall child in kindergarten,” says astrophysicist Marta Volonteri, at the University of Michigan in Ann Arbor.
Prevailing theories suggest that black holes form either from the tiny, dense objects left behind after the deaths of early stars, or they form from the direct collapse of cosmic gases. For the first theory to be correct, Volonteri says, ULAS J1120+0641 would have needed to begin growing before the beginning of time, suggesting that the direct collapse theory is better supported by the quasar’s discovery.
Scientists think there are maybe 100 distant, bright objects like the newly discovered quasar sprinkled throughout the entire sky, and astrophysicist Avi Loeb, at Harvard University, says he hopes sky surveys will find more of them. These quasars, if they exist, could act as beacons of light that help astronomers study the early universe. ULAS J1120+0641 has a luminosity of 6.3 × 1013L⊙,i.e.around 10^40 watts and hosts a black hole with a mass of 2 × 109M⊙ (where L⊙ and M⊙ are the luminosity and mass of the Sun).
The Most Powerful Quasar in Local UNiverse
Material has been discovered moving at nearly 10% the speed of light away from the centre of the nearby quasar PDS456 - the most powerful object in the local universe. PDS 456 is a nearby (z = 0.184), luminous (Lbol ~ 1047 erg s–1) type I quasar. Like all quasars, PDS456 is thought to be powered by matter converting into energy when material is swallowed by a supermassive black hole. New observations show that its energy output is so large that it is "choking on its food" and radiation is literally blowing the top off the inner region of the disc of in-falling material that surrounds the black hole. The discovery is being announced on Wednesday 9th April at the UK/Ireland National Astronomy Meeting in Dublin on behalf of a team from the University of Leicester and the NASA Goddard Space Flight Center.
PDS456 was discovered in 1997 and lies at a redshift of only 0.184 (a mere
800 million light-years away - our backyard by quasar standards).Its energy
output is equivalent to that of 25,000 billion Suns requiring a black hole
of roughly a billion solar masses. Such objects are relatively common with
high redshifts in the distant universe, but nearby ones are scarce.
"Fortunately, PDS456 is sufficiently close that we can study it in great
detail and thereby learn about the structure of these extraordinary
objects," says Dr Paul O'Brien of the University of Leicester, who will
present the findings.
Members of the research team have been studying PDS456 for several years.
Their previous work has measured the large power output and other basic
properties of PDS456, but now, using X-ray data from the XMM-Newton X-ray
satellite and ultraviolet data from the Hubble Space Telescope, they have
discovered the new and unexpected twist. The team had suspected that PDS456
is accumulating matter at almost the maximum rate allowed for feeding a
black hole. Theory suggests that a black hole may "choke" under these
circumstances, expelling matter outward.
Before being sucked into the black hole, accreting material generally forms
a flattened, rotating disc which allows matter to move inwards while
radiating energy away. However, the energy output of PDS456 is so large that
even the enormous gravitational pull of the black hole cannot capture it
all. Instead the radiation blows the top off the inner disc. The material
travels at close to the speed of light because this process happens very
close to the black hole - within a region about the same size as the solar
system. "It appears that PDS 456 is expelling matter at the rate of many
times the mass of our sun every year" comments Dr James Reeves. "This
massive outflow may tip the balance of power in this quasar, implying that a
large fraction of its total energy output is involved in driving the flow.
Such high mass, high velocity flows pose a real problem for current models
of quasars."
In one respect, PDS456 is similar to 3C273, the very first quasar discovered
back in 1962. "Our observations show that PDS456 looks remarkably similar to
3C273, though brighter, right across the spectrum from the ultraviolet
through to the infrared," comments Paul O'Brien. "But 3C273 is a harder
object to study in X-rays because it has a powerful jet pointing almost
directly at us. The jet beams radiation, including X-rays, at us,
contaminating our view of the centre. It is like trying to see a light bulb
next to the glare of a searchlight. In the case of PDS456, any jet is
pointing away from our line of sight so we get a much clearer view of its
disc."
The clear view to the centre of PDS456 means the researchers can use it as a
template object to determine what all powerful quasars are like,
particularly those accreting matter at a high rate. In the early universe,
when galaxies were young, their central black holes were growing rapidly and
may have been accreting matter at a high rate. Today only a few, like PDS
456, continue to do so.
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