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December 05, 2011

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Two record-sized black holes identified

Dec. 5, 2011
Courtesy of Nature
and World Science staff

Two black holes al­most as hefty as 10 bil­lion or more Suns have been iden­ti­fied, break­ing records for black hole size, as­tro­no­mers are re­port­ing.

The find­ings, which may prompt a re-evalua­t­ion of how some black holes are formed, are re­ported in the re­search jour­nal Na­ture this week.

A black hole is an ob­ject so com­pact and heavy that its gra­vity over­pow­ers an­y­thing that comes near it, even par­t­i­cles or waves of light. The pre­vi­ously heaviest-known black hole weighs the equiv­a­lent of 6.3 bil­lion suns, and lies in the gi­ant el­lip­ti­cal gal­axy Mess­i­er 87, said the re­search­ers, Chung-Pei Ma of the Uni­vers­ity of Cal­i­for­nia, Berke­ley, and col­leagues.

One con­se­quence of the new dis­cov­ery, they added, is that sci­en­tists may have to con­sid­er wheth­er black holes in the larg­est ga­lax­ies are formed dif­fer­ently from those in smaller ga­lax­ies.

The larg­est black holes are called su­per­mas­sive black holes and typ­ic­ally lurk at the cen­ters of ga­lax­ies, an­chor­ing their stars to­geth­er with their mighty gravita­t­ional field. 

In gen­er­al, ga­lax­ies and their cen­tral black holes are be­lieved to have formed from re­gions of the pri­mor­di­al ma­te­ri­al that made up the newly formed uni­verse that hap­pened to be more com­pact than oth­er re­gions. These dens­er ar­eas are thought to have grad­u­ally be­come even more com­pact as a re­sult of their own gra­vity. The de­tails of the pro­cess aren’t fully un­der­stood, though. Many as­tro­no­mers be­lieve that the big­gest black holes are formed through merg­ers of smaller ones and their re­spec­tive host ga­lax­ies.

The new­found, record-break­ing black holes are much big­ger than the char­ac­ter­is­tics of their host ga­lax­ies would pre­dict, ac­cord­ing to Ma and col­leagues. They meas­ured da­ta from two near­by ga­lax­ies, NGC 3842 and NGC 4889, and found that NGC 3842 has a cen­tral black hole with a mass of 9.7 bil­lion suns, and NGC 4889 has a black hole of com­pa­ra­ble or larg­er mass.

All mas­sive ga­lax­ies with a “spheroidal” or ball-like com­po­nent are thought to har­bor su­per­mas­sive black holes.

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Two black holes almost as hefty as 10 billion or more suns have been identified, breaking records for black hole size, astronomers are reporting. The findings, which may prompt a re-evaluation of how some black holes are formed, are reported in the research journal Nature this week. A black hole is an object so compact and heavy that its gravity overpowers anything that comes near it, even particles or waves of light. The previously heaviest-known black hole weighs the equivalent of 6.3 billion suns, and lies in the giant elliptical galaxy Messier 87, said the researchers, Chung-Pei Ma of the University of California, Berkeley, and colleagues. One consequence of the new discovery, they added, is that scientists may have to consider whether black holes in the largest galaxies are formed differently from those in smaller galaxies. The largest black holes are called supermassive black holes and typically lurk at the centers of galaxies, anchoring their stars together with their mighty gravitational field. In general, galaxies and their central black holes are believed to have formed from regions of the primordial material that made up the newly formed universe that happened to be more compact than other regions. These denser areas are thought to have gradually become even more compact as a result of their own gravity. The details of the process aren’t fully understood, though. Many astronomers believe that the biggest black holes are formed through mergers of smaller ones and their respective host galaxies. The newfound, record-breaking black holes are much bigger than the characteristics of their host galaxies would predict, according to Ma and colleagues. They measured data from two nearby galaxies, NGC 3842 and NGC 4889, and found that NGC 3842 has a central black hole with a mass of 9.7 billion solar masses, and NGC 4889 has a black hole of comparable or larger mass. All massive galaxies with a “spheroidal” or ball-like component are thought to harbor supermassive black holes.