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Hungry black hole found to eat faster than thought possible

Oct. 8, 2014
Courtesy of the International Centre 
for Radio Astronomy Research
and World Science staff

As­tro­no­mers say they have found a black hole con­sum­ing a near­by star 10 times faster than pre­vi­ously thought pos­si­ble.

It’s swal­low­ing a weight equiv­a­lent to 100 bil­lion bil­lion hot dogs a min­ute, they claim.

A black hole is an ob­ject so compact that its gra­vity is over­whelm­ing, and pulls in an­y­thing that gets too near, in­clud­ing light. Al­though that ac­counts for the name “black,” gas­es that are fall­ing in­to a black hole can be­come very hot and bright, clearly il­lu­mi­nat­ing their loca­t­ion.

Artist's ren­der­ing of what black hole P13 would look like close up. Im­age cre­at­ed by Tom Rus­sell of ICRAR us­ing soft­ware cre­at­ed by Rob Hynes of Lou­i­si­ana State Uni­ver­si­ty.


Sci­en­tists first no­ticed the black hole, called P13, be­cause it was a lot brighter than oth­er black holes, said as­tron­o­mer Ro­ber­to So­ria of Cur­tin Uni­vers­ity in Aus­tral­ia, one of the re­search­ers. But as­tron­o­mers first as­sumed the ob­ject was just ex­tremely big, be­cause it was thought that size de­ter­mines the max­i­mum rate of a black hole’s feed­ing.

“It made sense to as­sume that P13 was big­ger than the or­di­nary,” said So­ria, who is al­so part of the In­terna­t­ional Cen­tre for Ra­di­o As­tron­o­my Re­search. But then, So­ria and col­leagues meas­ured its mass, or weight, and found it was ac­tu­ally on the small side, de­spite be­ing at least a mil­lion times brighter than the Sun. 

It was only then that they real­ized just how much ma­te­ri­al it was con­sum­ing, he ex­plained. The find­ing is pub­lished Oct. 8 in the jour­nal Na­ture.

“There’s not really a strict lim­it like we thought, black holes can ac­tu­ally con­sume more gas and pro­duce more light,” So­ria said.

The black hole lies on the out­skirts of the gal­axy NGC7793, about 12 mil­lion light years from Earth. A light year is the dis­tance light trav­els in a year.

An im­age of gal­axy NGC 7793, show­ing the lo­ca­tion of black hole P13. Gal­axy im­age is a com­bined optical/X-ray im­age. (Cred­its: X-ray (NA­SA/CX­C/U. of Stras­bourg/M. Pakull et al); Op­ti­cal (ES­O/VLT/U. of Stras­bourg/M. Pakull et al); H-alpha (NOAO/AU­RA/NS­F/C­ 1.5m))


P13 is suck­ing up gas from a do­nor star, So­ria ex­plained. Sci­en­tists no­ticed that one side of that star was al­ways brighter than the oth­er be­cause it was lit up by X-rays com­ing from near the black hole. So the star looked brighter or faint­er as it cir­cled P13.

“This al­lowed us to meas­ure the time it takes for the black hole and the do­nor star to ro­tate around each oth­er, which is 64 days,” he added. From that, they worked out that the black hole must “weigh” the equiv­a­lent of less than 15 of our Suns.

So­ria com­pared P13 to small Jap­a­nese eat­ing cham­pi­on Takeru Kobayashi. “As hotdog-eat­ing leg­end Takeru Kobayashi fa­mously showed us, size does not al­ways mat­ter in the world of com­pet­i­tive eat­ing and even small black holes can some­times eat gas at an ex­cep­tion­al rate,” he said.

P13 is a mem­ber of a special group of black holes known as ul­tra­lu­mi­nous X-ray sources, he added. “These are the cham­pi­ons of com­pet­i­tive gas eat­ing in the Uni­verse, ca­pa­ble of swal­low­ing their do­nor star in less than a mil­lion years, which is a very short time on cos­mic scales,” he said.


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Astronomers say they have found a black hole consuming a nearby star 10 times faster than previously thought possible. It’s swallowing a weight equivalent to 100 billion billion hot dogs a minute, they claim. A black hole is an object that is so dense that its gravity pulls in anything that gets too near, including light. Although that accounts for the name “black,” gases that are falling into a black hole can become very hot and bright, clearly illuminating their location. Scientists first noticed the black hole, called P13, because it was a lot brighter than other black holes, said astronomer Roberto Soria of Curtin University in Australia, one of the researchers. But astronomers first assumed the object was just extremely big, because it was thought that size determines the maximum rate of a black hole’s feeding. “It made sense to assume that P13 was bigger than the ordinary,” said Soria, who is also part of the International Centre for Radio Astronomy Research. But then, Soria and colleagues measured its mass, or weight, and found it was actually on the small side, despite being at least a million times brighter than the Sun. It was only then that they realized just how much material it was consuming, he explained. The finding was published Oct. 8 in the journal Nature. “There’s not really a strict limit like we thought, black holes can actually consume more gas and produce more light,” Soria said. The black hole lies on the outskirts of the galaxy NGC7793, about 12 million light years from Earth. A light year is the distance light travels in a year. P13 is sucking up gas from a donor star, Soria explained. Scientists noticed that one side of that star was always brighter than the other because it was lit up by X-rays coming from near the black hole. So the star looked brighter or fainter as it circled P13. “This allowed us to measure the time it takes for the black hole and the donor star to rotate around each other, which is 64 days,” he added. From that, they worked out that the black hole must “weigh” the equivalent of less than 15 of our Suns. Soria compared P13 to small Japanese eating champion Takeru Kobayashi. “As hotdog-eating legend Takeru Kobayashi famously showed us, size does not always matter in the world of competitive eating and even small black holes can sometimes eat gas at an exceptional rate,” he said. P13 is a member of a select group of black holes known as ultraluminous X-ray sources, he added. “These are the champions of competitive gas eating in the Universe, capable of swallowing their donor star in less than a million years, which is a very short time on cosmic scales,” he said.