ICRAR: Hungry black hole consumes material faster than thought possible

A rendering of what Black Hole P13 would look like close up. 

Credit: by Tom Russell (ICRAR) using software created by Rob Hynes (Louisiana State University).

Astronomers have discovered a black hole that is consuming gas from a nearby star 10 times faster than previously thought possible.

The black hole, known as P13, lies on the outskirts of the galaxy NGC7793 about 12 million light years from Earth and is ingesting a weight equivalent to 100 billion billion hot dogs every minute.

The discovery was published today in the journal Nature.

International Centre for Radio Astronomy Research (ICRAR) astronomer Dr Roberto Soria, who is based at ICRAR's Curtin University node, said that as gas falls towards a black hole it gets very hot and bright.

He said scientists first noticed P13 because it was a lot more luminous than other black holes, but it was initially assumed that it was simply bigger.

"It was generally believed the maximum speed at which a black hole could swallow gas and produce light was tightly determined by its size," Dr Soria said.

"So it made sense to assume that P13 was bigger than the ordinary, less bright black holes we see in our own galaxy, the Milky Way."

When Dr Soria and his colleagues from the University of Strasbourg measured the mass of P13 they 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 realised just how much material it was consuming.

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

Dr Soria said P13 rotates around a supergiant 'donor' star 20 times heavier than our own Sun.

He said the scientists saw that one side of the donor star was always brighter than the other because it was illuminated by X-rays coming from near the black hole, so the star appeared brighter or fainter as it went around P13.

Primary Image: This is a combined optical /X-ray image of NGC 7793. 

Inset image: This is a rendering of what P13 would look like close up. 

Credit: X-ray (NASA /CXC /Univ of Strasbourg /M. Pakull et al); Optical (ESO /VLT /Univ of Strasbourg /M. Pakull et al); H-alpha (NOAO /AURA /NSF /CTIO 1.5m). 

Insert Image: created by Tom Russell (ICRAR) using software created by Rob Hynes (Louisiana State University).

"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, and to model the velocity of the two objects and the shape of the orbit," Dr Soria said.

"From this, we worked out that the black hole must be less than 15 times the mass of our Sun."

Dr Soria said P13 is a member of a select group of black holes known as ultraluminous X-ray sources.

"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.

More information: 'A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source' was published in Nature, 9 October 2014. C. Motch, M. W. Pakull, R. Soria, F. Grise, G. Pietrzynski. DOI: 10.1038/nature13730

Carbon monoxide predicts 'red and dead' future of gas guzzler galaxy

This image shows radio waves emitted from ALESS65 as observed by the Australia Telescope Compact Array (ATCA). 

Credit: Huynh et al.

Astronomers have studied the carbon monoxide in a galaxy over 12 billion light years from Earth and discovered that it's running out of gas, quite literally, and headed for a 'red and dead' future.

The galaxy, known as ALESS65, was observed by the Atacama Large Millimeter Array (ALMA) in 2011 and is one of less than 20 known distant galaxies to contain carbon monoxide.

Dr Minh Huynh from The University of Western Australia node of the International Centre for Radio Astronomy Research (ICRAR) led the team on their search for galactic carbon monoxide in work published today in the Monthly Notices of the Royal Astronomical Society.

"We're familiar with carbon monoxide here on Earth as the deadly gas that can cause suffocation, but in galaxies it plays an important role in the lifecycle of stars," said Huynh.

"Out of the galaxies that we know contain carbon monoxide, less than 20 are as far away from Earth as ALESS65. Out of the billions of galaxies out there, the detections are very rare!"

Huynh, who grew up in Perth, said that at first astronomers didn't think there could be massive 'red and dead' galaxies in the distant Universe, so studying galaxies heading towards that fate is important to solve the puzzle of their existence.

This is NGC5044, a "red and dead" galaxy like ALESS65 will become in about 25 million years. 

NB:The X-Rays are shown in blue and the visible light is shown in yellow. 

Credit: X-ray: NASA /CXC /Stanford Univ /N.Werner et al; Optical: DSS

Using the Australia Telescope Compact Array (ATCA) radio telescope in NSW, Australia, Huynh and the team worked out how much carbon monoxide they could see in ALESS65 and extrapolated that out into how much fuel the galaxy has left, how much gas it has.

"All galaxies have a certain amount of fuel to make new stars," said Huynh.

"Our galaxy, the Milky Way, has about five billion years before it runs out of fuel and becomes 'red and dead', but ALESS65 is a gas guzzler and only has 10s of millions of years left, very fast in astronomical terms."

The Atacama Compact Array (ACA) forming part of the ALMA observatory. 

Credit: ALMA, ESO

The team also combined their observations of the galaxy with the original data from ALMA to work out how similar ALESS65 is to galaxies nearer to Earth.

Arp220, a nearby ‘Ultraluminous Infrared Galaxy’ similar to what ALESS65 would look like if it were closer to Earth. 

Credit: NASA, ESA, and the Hubble Team

"We were able to work out the strength of the UV radiation in ALESS65; it's similar to some 'starbursting' galaxies in the local universe, but the stars in ALESS65 are forming in much larger areas when compared to local galaxies," said Huynh.

The team will now turn their attentions to the search for carbon monoxide in another galaxy near to ALESS65, named ALESS61.

"Finding and studying carbon monoxide in more galaxies will tell us even more about how stars formed in the early days of the Universe and help solve the mystery of far away 'red and dead' galaxies" said Huynh.

More information: "Detection of molecular gas in an ALMA [CII]-identified Submillimetre Galaxy at z=4.44" Huynh et al. Monthly Notices of the Royal Astronomical Society, Published 9th of July 2014. mnrasl.oxfordjournals.org/look… 0.1093/mnrasl/slu077 . On Arxiv: arxiv.org/abs/1407.0463

Gamma-ray bursts (GRB): Afterglow discovery surprises scientists

Measurements of polarized light in the afterglow of GRB 120308A by the Liverpool Telescope and its RINGO2 instrument indicate the presence of a large-scale stable magnetic field linked with a young black hole, as shown in this illustration. 

Credit: NASA's Goddard Space Flight Center /S. Wiessinger

Research from an international team of scientists led by the University of Leicester has discovered for the first time that one of the most powerful events in our universe, Gamma-Ray Bursts (GRB), behave differently than previously thought.

The study, published in the prestigious scientific journal Nature, uses evidence from observation of a GRB to rule out most of the existing theoretical predictions concerning the afterglow of the explosions.

Klaas Wiersema

For Dr Klaas Wiersema, of the University of Leicester's Department of Physics and Astronomy, it was handy that he was up in the middle of the night tending to his three-year-old son which is when he got the alert that a GRB had occurred.

He said: "When a suitable GRB is detected by a satellite, I get a text message on my phone, and then I have to very quickly tell the observatory in Chile exactly which observations I want them to take, and how.

"This is usually a rather stressed and frantic few hours of working, as fast as possible, on my laptop throughout our night-time, and I remember very well that my son, who was three at the time, was up a lot that night too, so I kept on running back and forth between my laptop, my phone to call the observatory in Chile, and my son's cot!"

The effort was worth it- and has led to scientific findings that will change theoretical understandings of the afterglows of GRBs.

Dr Wiersema explains: "About once per day, a short, very bright flash of gamma-rays (the most energetic form of light) is detected by satellites. These flashes are called gamma-ray bursts (GRBs), and take place in galaxies far away, when a massive star collapses at the end of its life.

"These GRBs are followed by a so-called "afterglow", slowly fading emission that can be seen at all wavelengths (including visible light), for a few days to weeks."

"We know that the afterglow emission is formed by a shockwave, moving at very high velocities, in which electrons are being accelerated to tremendous energies."

"These fast moving electrons then produce the afterglow light that we detect.

When a massive star dies it explodes as a supernova. 

The core of the star collapses into a black hole, and in care cases a jet is formed along the rotation axis of the newly formed black hole. 

Processes in this jet emits gamma radiation, which we observe as a so-called gamma-ray burst. 

Typically gamma-ray bursts last a few minutes. 

When the jet hits material surrounding the dying star an afterglow is formed. 

New observations of the degree of polarisation of the afterglow light has shown that the afterglow behaves differently than expected 

Credit: NASA

"However, how this acceleration process actually works is very hard to study on Earth in laboratories, or using computer simulations."

"What we do, is study the polarised light of the afterglow using large optical telescopes, and special filters, that work much like the filters in Polaroid sunglasses."

Gamma-ray burst 121024A, as seen on the day of burst by ESO's Very Large Telescope (VLT) in Chile. Only a week later the source had faded completely. 

Credit: Dr Klaas Wiersema, University of Leicester, UK and Dr Peter Curran, ICRAR.

Dr Wiersema says it is important to remember that light is a wave, when light is linearly polarised, it means that the wave vibrations lie in a plane; and when light is circularly polarised, it means that that this plane rotates on the sky.

He added: "Different theories for electron acceleration and light emission within the afterglow all predict different levels of linear polarisation, but theories all agreed that there should be no circular polarisation in visible light."

Peter Curran, ICRAR

"This is where we come in: we decided to test this by carefully measuring both the linear and circular polarisation of one afterglow, of GRB 121024A, detected by the Swift satellite."

"Using the ESO Very Large Telescope (VLT) in Chile, we measured both the linear and circular polarisation of an afterglow with high accuracy."

"Much to our surprise we clearly detected circular polarisation, while theories predicted we should not see any at all."

"We believe that the most likely explanation is that the exact way in which electrons are accelerated within the afterglow shockwave is different from what we always thought."

"It is a very nice example of observations ruling out most of the existing theoretical predictions – exactly why observers like me are in this game!

More information: Paper: Circular polarisation in the optical afterglow of GRB 121024A, Nature, DOI: 10.1038/nature13237

Hubble Study in spiral Galaxy M83 reveals new super-powered small black hole, MQ1

Nearby spiral galaxy M83 and the MQ1 system with jets, as seen by the Hubble Space Telescope. 

The blue circle marks the position of the MQ1 system in the galaxy (shown inset). 

Image courtesy M83 - NASA, ESA and the Hubble Heritage Team (WFC3/UVIS, STScI-PRC14-04a).MQ1 inset - W. P. Blair (Johns Hopkins University) and R. Soria (ICRAR-Curtin).

A team of Australian and American astronomers have been studying nearby galaxy M83 and have found a new superpowered small black hole, named MQ1, the first object of its kind to be studied in this much detail.

Astronomers have found a few compact objects that are as powerful as MQ1, but have not been able to work out the size of the black hole contained within them until now.

The team observed the MQ1 system with multiple telescopes and discovered that it is a standard-sized small black hole, rather than a slightly bigger version that was theorised to account for all its power.

Curtin University senior research fellow Dr Roberto Soria, who is part of the International Centre for Radio Astronomy Research (ICRAR) and led the team investigating MQ1, said it was important to understand how stars were formed, how they evolved and how they died, within a spiral shaped galaxy like M83.

"MQ1 is classed as a microquasar - a black hole surrounded by a bubble of hot gas, which is heated by two jets just outside the black hole, powerfully shooting out energy in opposite directions, acting like cosmic sandblasters pushing out on the surrounding gas," Dr Soria said.

"The significance of the huge jet power measured for MQ1 goes beyond this particular galaxy: it helps astronomers understand and quantify the strong effect that black hole jets have on the surrounding gas, which gets heated and swept away.

"This must have been a significant factor in the early stages of galaxy evolution, 12 billion years ago, because we have evidence that powerful black holes like MQ1, which are rare today, were much more common at the time."

"By studying microquasars such as MQ1, we get a glimpse of how the early universe evolved, how fast quasars grew and how much energy black holes provided to their environment."

As a comparison, the most powerful microquasar in our galaxy, known as SS433, is about 10 times less powerful than MQ1.

Although the black hole in MQ1 is only about 100 kilometres wide, the MQ1 structure, as identified by the Hubble Space Telescope, is much bigger than our Solar System, as the jets around it extend about 20 light years from either side of the black hole.

Black holes vary in size and are classed as either stellar mass (less than about 70 times the mass of our Sun) or supermassive (millions of times the mass of our Sun, like the giant black hole that is located in the middle of the Milky Way).

MQ1 is a stellar mass black hole and was likely formed when a star died, collapsing to leave behind a compact mass.