Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Winds a quarter the speed of light spotted leaving mysterious binary systems

29.04.2016

Two black holes in nearby galaxies have been observed devouring their companion stars at a rate exceeding classically understood limits, and in the process, kicking out matter into surrounding space at astonishing speeds of around a quarter the speed of light.

The researchers, from the University of Cambridge, used data from the European Space Agency's (ESA) XMM-Newton space observatory to reveal for the first time strong winds gusting at very high speeds from two mysterious sources of x-ray radiation. The discovery, published in the journal Nature, confirms that these sources conceal a compact object pulling in matter at extraordinarily high rates.


Artist's impression depicting a compact object -- either a black hole or a neutron star -- feeding on gas from a companion star in a binary system.

Credit: ESA - C. Carreau

When observing the Universe at x-ray wavelengths, the celestial sky is dominated by two types of astronomical objects: supermassive black holes, sitting at the centres of large galaxies and ferociously devouring the material around them, and binary systems, consisting of a stellar remnant - a white dwarf, neutron star or black hole - feeding on gas from a companion star.

In both cases, the gas forms a swirling disc around the compact and very dense central object. Friction in the disc causes the gas to heat up and emit light at different wavelengths, with a peak in x-rays.

But an intermediate class of objects was discovered in the 1980s and is still not well understood. Ten to a hundred times brighter than ordinary x-ray binaries, these sources are nevertheless too faint to be linked to supermassive black holes, and in any case, are usually found far from the centre of their host galaxy.

"We think these so-called 'ultra-luminous x-ray sources' are special binary systems, sucking up gas at a much higher rate than an ordinary x-ray binary," said Dr Ciro Pinto from Cambridge's Institute of Astronomy, the paper's lead author.

"Some of these sources host highly magnetised neutron stars, while others might conceal the long-sought-after intermediate-mass black holes, which have masses around one thousand times the mass of the Sun. But in the majority of cases, the reason for their extreme behaviour is still unclear."

Pinto and his colleagues collected several days' worth of observations of three ultra-luminous x-ray sources, all located in nearby galaxies located less than 22 million light-years from the Milky Way. The data was obtained over several years with the Reflection Grating Spectrometer on XMM-Newton, which allowed the researchers to identify subtle features in the spectrum of the x-rays from the sources.

In all three sources, the scientists were able to identify x-ray emission from gas in the outer portions of the disc surrounding the central compact object, slowly flowing towards it.

But two of the three sources - known as NGC 1313 X-1 and NGC 5408 X-1 - also show clear signs of x-rays being absorbed by gas that is streaming away from the central source at 70,000 kilometres per second - almost a quarter of the speed of light.

"This is the first time we've seen winds streaming away from ultra-luminous x-ray sources," said Pinto. "And the very high speed of these outflows is telling us something about the nature of the compact objects in these sources, which are frantically devouring matter."

While the hot gas is pulled inwards by the central object's gravity, it also shines brightly, and the pressure exerted by the radiation pushes it outwards. This is a balancing act: the greater the mass, the faster it draws the surrounding gas; but this also causes the gas to heat up faster, emitting more light and increasing the pressure that blows the gas away.

There is a theoretical limit to how much matter can be pulled in by an object of a given mass, known as the Eddington limit. The limit was first calculated for stars by astronomer Arthur Eddington, but it can also be applied to compact objects like black holes and neutron stars.

Eddington's calculation refers to an ideal case in which both the matter being accreted onto the central object and the radiation being emitted by it do so equally in all directions.

But the sources studied by Pinto and his collaborators are potentially being fed through a disc which has been puffed up due to internal pressures arising from the incredible rates of material passing through it. These thick discs can naturally exceed the Eddington limit and can even trap the radiation in a cone, making these sources appear brighter when we look straight at them. As the thick disc moves material further from the black hole's gravitational grasp it also gives rise to very high-speed winds like the ones observed by the Cambridge researchers.

"By observing x-ray sources that are radiating beyond the Eddington limit, it is possible to study their accretion process in great detail, investigating by how much the limit can be exceeded and what exactly triggers the outflow of such powerful winds," said Norbert Schartel, ESA XMM-Newton Project Scientist.

The nature of the compact objects hosted at the core of the two sources observed in this study is, however, still uncertain.

Based on the x-ray brightness, the scientists suspect that these mighty winds are driven from accretion flows onto either neutron stars or black holes, the latter with masses of several to a few dozen times that of the Sun.

To investigate further, the team is still scrutinising the data archive of XMM-Newton, searching for more sources of this type, and are also planning future observations, in x-rays as well as at optical and radio wavelengths.

"With a broader sample of sources and multi-wavelength observations, we hope to finally uncover the physical nature of these powerful, peculiar objects," said Pinto.

Media Contact

Sarah Collins
sarah.collins@admin.cam.ac.uk
44-012-237-65542

 @Cambridge_Uni

http://www.cam.ac.uk 

Sarah Collins | EurekAlert!

Further reports about: ESA Galaxies NGC XMM-Newton binary systems black holes neutron stars speed of light wavelengths

More articles from Physics and Astronomy:

nachricht Electrocatalysis can advance green transition
23.01.2017 | Technical University of Denmark

nachricht Quantum optical sensor for the first time tested in space – with a laser system from Berlin
23.01.2017 | Ferdinand-Braun-Institut Leibniz-Institut für Höchstfrequenztechnik

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Tracking movement of immune cells identifies key first steps in inflammatory arthritis

23.01.2017 | Health and Medicine

Electrocatalysis can advance green transition

23.01.2017 | Physics and Astronomy

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>