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Super black hole a “headache” for astronomers

June 29, 2011
World Science staff

As­tro­no­mers have found a mam­moth ob­ject that they say smashes records for dis­tance and bright­ness and could shed light on a never-probed early stage of cos­mic his­tory. 

The ob­ject is al­so, to some ex­tent, un­want­ed.

Cur­rent phys­i­cal the­o­ries don’t ac­count for such huge ob­jects ap­pear­ing as early in the his­to­ry of the un­iverse as this one is. The time of its ap­pear­ance can be es­ti­mat­ed by its dis­tance.

The ob­ject dubbed ULAS J1120+0641 is not the bright­est spot in this im­age. It is the tiny red dot to the left of it, near the mid­dle—its faint­ness due on­ly to its in­cred­i­ble dis­tance. (Cred­it: ES­O/UKIDSS/S­DSS)


“This gives as­tro­no­mers a head­ache,” said Dan­iel Mort­lock of Im­pe­ri­al Col­lege Lon­don, one of the dis­cov­er­ers and lead au­thor of a pa­per re­port­ing the find in the June 30 is­sue of the re­search jour­nal Na­ture

“It’s dif­fi­cult to un­der­stand,” he ex­plained, how some­thing “a bil­lion times more mas­sive than the Sun can have grown so early in the his­to­ry of the un­iverse. It’s like roll­ing a snow­ball down the hill and sud­denly you find that it’s 20 feet across.”

This is­n’t the first time that prob­lem has come up; as­tro­no­mers have been work­ing on the­o­ries to ad­dress it. But the new ob­ject, the bright­est known by far so early in the his­tory of the uni­verse,  is per­haps the most dra­mat­ic ex­am­ple of the prob­lem.

The thing in ques­tion is be­lieved to be the most dis­tant known su­per­mas­sive black hole, a type of ob­ject so com­pact and heavy that its gra­vity over­whelms and drags in an­y­thing that strays too close, even light rays. Black holes aren’t di­rectly vis­i­ble, but can be seen when in­falling ob­jects heat up and be­come bright. In this case, riv­ers of gas are plung­ing in­to the black hole, re­search­ers say.

The dis­cov­ery came to light thanks to an on­go­ing sky sur­vey be­ing con­ducted at the U.K. In­fra­red Tel­e­scope and fol­low-up ob­serva­t­ions with the Gem­i­ni North tel­e­scope, both on Mauna Kea in Ha­waii. The black hole is al­so re­ferred to as a qua­sar, a type of black hole that sits and the cen­ter of a gal­axy guz­zling ma­te­ri­al, light­ing up the whole re­gion. To be pre­cise, “qua­sar” ac­tu­ally refers to the en­tire gal­axy, not just the black hole.

The light from this qua­sar started head­ing to­ward us when the un­iverse was only 6 per­cent of its pre­s­ent age, 770 mil­lion years af­ter the un­iverse was born, sci­en­tists say. The next most-dis­tant known qua­sar is seen as it was 870 mil­lion years af­ter that event. Be­cause of the dis­tance of these ob­jects, they ap­pear to us some­what as they would have back in their time.

“This qua­sar is a vi­tal probe of the early uni­verse. It is a very rare ob­ject that will help us to un­der­stand how su­per­mas­sive black holes grew,” said Ste­phen War­ren, the stu­dy’s team lead­er. Quasars are in ef­fect very bright, dis­tant ga­lax­ies thought to be pow­ered by “supermas­sive” black holes. Their bril­liance makes them pow­er­ful bea­cons that may help to probe the era when the first stars and ga­lax­ies were form­ing.

The new­found qua­sar, es­ti­mat­ed to weigh the equiv­a­lent of two bil­lion Suns, is so dis­tant that its light is be­lieved to probe the last part of an age called the reion­iz­a­tion era.

Some 300,000 years af­ter the Big Bang, an explosion-like event that sci­en­tists say cre­at­ed our uni­verse, the uni­verse had cooled down enough to al­low charged par­t­i­cles called elec­trons and pro­tons to com­bine in­to atoms of hy­dro­gen, a gas with no elec­tric charge. This cool dark gas would have per­me­at­ed the uni­verse un­til the first stars started form­ing about 100 to 150 mil­lion years lat­er. In­tense radia­t­ion from these stars slowly split the hy­dro­gen atoms back in­to pro­tons and elec­trons, a pro­cess called reion­iz­a­tion, mak­ing the uni­verse more trans­par­ent to ul­tra­vi­o­let light. It is be­lieve that this pro­cess, a mile­stone in cos­mic his­to­ry, oc­curred be­tween about 150 mil­lion to 800 mil­lion years af­ter the Big Bang.

An artist’s im­pres­sion shows how ULAS J1120+0641 may have looked from clos­er up. (ES­O/M. Ko­rn­messer).


Cos­mol­o­gists are keen to meas­ure the state of gas in the early un­iverse, and to un­der­stand how stars and ga­lax­ies formed. Most of the gas in the un­iverse is hy­dro­gen, and most of it is ion­ized to­day, mean­ing the elec­trons and pro­tons are sep­a­rat­ed.

The qua­sar is an op­por­tun­ity as well as a head­ache, be­cause it lets sci­en­tists meas­ure the con­di­tions in the gas that the qua­sar’s light passes through on its way to us, Mort­lock said. “What is par­tic­u­larly im­por­tant… is how bright it is,” he ex­plained. “It’s hun­dreds of times brighter than an­y­thing else yet dis­cov­ered at such a great dis­tance. This means that we can use it to tell us for the first time what con­di­tions were like in the early uni­verse.”

“It took us five years to find this ob­ject,” added Bram Ven­e­mans of the Eu­ro­pe­an South­ern Ob­serv­a­to­ry in Garch­ing, Ger­ma­ny, one of the au­thors of the stu­dy.

As one looks fur­ther away and thus fur­ther back in time, sci­en­tists rea­son that we should eventually reach the time when the hy­dro­gen was neu­tral, with the elec­trons and pro­tons com­bined as atoms. The light from the new qua­sar dis­plays the char­ac­ter­is­tic sig­na­ture of neu­tral gas, the in­ves­ti­ga­tors said. This sig­na­ture, show­ing the qua­sar pre­cedes the ep­och of reion­iz­a­tion, was pre­dicted in 1998 but has nev­er been ob­served be­fore.

“Be­ing able to an­a­lyze mat­ter at this crit­i­cal junc­ture in the his­to­ry of the uni­verse is some­thing we’ve been long striv­ing for but nev­er quite achieved. Now it looks like we have crossed the bar­ri­er,” said Steve War­ren of Im­pe­ri­al Col­lege, lead­er of the qua­sar team. “It’s like dis­cov­er­ing a new con­ti­nent which we can now ex­plore.” The qua­sar, named ULAS J1120+0641, was dis­cov­ered in the UKIRT In­fra­red Deep Sky Sur­vey, a new map of the sky as it ap­pears in in­fra­red light.


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Astronomers have found a mammoth object that newly breaks records for its distance and brightness, but their excitement is tinged with confusion. Current physical theories don’t account for such huge objects appearing as early in the history of the universe as this one is. The time of its appearance can be estimated by its distance. “This gives astronomers a headache,” said Daniel Mortlock of Imperial College London, one of the discoverers and lead author of a paper reporting the find in the June 30 issue of the research journal Nature. “It’s difficult to understand how a black hole a billion times more massive than the Sun can have grown so early in the history of the universe. It’s like rolling a snowball down the hill and suddenly you find that it’s 20 feet across.” While this isn’t the first time that problem has come up—astronomers have been working on theories to address it—the new object is one of the most dramatic examples. The thing in question is believed to be the most distant known supermassive black hole, a type of object so compact and heavy that its gravity overwhelms and drags in anything that strays too close, even light rays. Black holes aren’t directly visible, but can be seen when infalling objects heat up and become bright. In this case, rivers of gas are plunging into the black hole, researchers say. The discovery came to light thanks to an ongoing sky survey being conducted at the U.K. Infrared Telescope and follow-up observations with the Gemini North telescope, both on Mauna Kea in Hawaii. The black hole is also referred to as a quasar, a type of black hole that sits and the center of a galaxy guzzling material, lighting up the whole region. To be precise, “quasar” actually refers to the entire galaxy, not just the black hole. The light from this quasar started heading toward us when the universe was only 6% of its present age, 770 million years after the universe was born, scientists say. The next most-distant quasar is seen as it was 870 million years after that event. Because of the distance of these objects, they appear to us as somewhat as they would have back in their time. “This quasar is a vital probe of the early Universe. It is a very rare object that will help us to understand how supermassive black holes grew a few hundred million years after the Big Bang,” said Stephen Warren, the study’s team leader. Quasars are in effect very bright, distant galaxies that are believed to be powered by “supermassive” black holes. Their brilliance makes them powerful beacons that may help to probe the era when the first stars and galaxies were forming. The newfound quasar, estimated to weigh the equivalent of two billion Suns, is so far that its light is believed to probe the last part of an age called the reionization era. Some 300,000 years after the Big Bang, an explosion-like event that scientists say created our universe, the universe had cooled down enough to allow charged particles called electrons and protons to combine into atoms of hydrogen, a gas with no electric charge. This cool dark gas would have permeated the Universe until the first stars started forming about 100 to 150 million years later. Intense radiation from these stars slowly split the hydrogen atoms back into protons and electrons, a process called reionization, making the Universe more transparent to ultraviolet light. It is believe that this process, a milestone in cosmic history, occurred between about 150 million to 800 million years after the Big Bang. Cosmologists are keen to measure the state of gas in the early universe, to understand the process of how stars and galaxies formed. Most of the gas in the universe is hydrogen, and most of it is ionized today, meaning the electrons and protons are separated. The quasar as an opportunity as well as a headache, because it lets scientists measure the conditions in the gas that the quasar’s light passes through on its way to us, Mortlock said. “What is particularly important… is how bright it is,” he explained. “It’s hundreds of times brighter than anything else yet discovered at such a great distance. This means that we can use it to tell us for the first time what conditions were like in the early universe.” “It took us five years to find this object,” added Bram Venemans of the European Southern Observatory in Garching, Germany, one of the authors of the study. As one looks further away and thus further back in time, scientists reason that we should eventually reach the time when the hydrogen was neutral, with the electrons and protons combined as atoms. The light from the new quasar displays the characteristic signature of neutral gas, the investigators said. This signature, showing the quasar is beyond the epoch of reionization, was predicted in 1998 but has never been observed before. “Being able to analyze matter at this critical juncture in the history of the universe is something we’ve been long striving for but never quite achieved. Now it looks like we have crossed the barrier,” said Steve Warren of Imperial College, leader of the quasar team. “It’s like discovering a new continent which we can now explore.” The quasar, named ULAS J1120+0641, was discovered in the UKIRT Infrared Deep Sky Survey, a new map of the sky as it appears in infrared light.