Feeds

Big or small, black holes are all the same

When it comes to matter, anyway

Internet Security Threat Report 2014

Blackholes all gobble up matter in the same way, whatever their size, new research has found. UK astronomers say that the same processes are at work inside all black holes: the only difference is that of scale.

The researchers, led by Professor Ian McHardy, from the University of Southampton, began by looking for similarities between ordinary, stellar-sized Galactic black hole systems, and the supermassive black holes in Active Galactic Nuclei (AGN).

Their idea was that if certain similarities could be established, then the shorter-lived and faster acting "small" blackholes could give them clues about how the supermassive black holes would behave on cosmic timescales.

Artist's impression of a black hole

Professor McHardy comments, "By studying the way in which the X-ray emission from black hole systems varies, we found that the accretion or 'feeding' process - where the black hole is pulling in material from its surroundings - is the same in black holes of all sizes and that AGN are just scaled-up Galactic black holes.

"We also found that the way in which the X-ray emission varies is strongly correlated with the width of optical emission lines from black hole systems."

McHardy explained that the observations have important implications for the overall understanding of the different types of active galactic nuclei, which are classified by the width of their emission lines.

For example, Seyfert galaxies, which have very narrow emission lines, are often regarded as unusual. Now that the correlation between emission line width and X-ray emission has been identified, astronomers can see that Seyfert galaxies are not so different from other active galactic nuclei: "they just have a smaller ratio of mass to accretion rate".

McHardy and his colleagues have shown that the so-called characteristic timescale - that is the period over which the mass accretion rate will change appreciably - varies linearly with the mass of the black hole, but inversely with accretion rate. That is to say, the more massive a black hole, the more matter it can consume, but the longer it takes for the rate of accretion to increase noticeably.

This means that the mass of a black hole can be determined simply by measuring its accretion rate and characteristic timescale. Very useful when you are dealing with an obscured supermassive black hole at the centre of a dusty galaxy, for instance.

As a black hole accretes matter, it emits X-rays in a distinctive way, known as an X-ray light curve.

Professor McHardy concludes: "It has been known for over two decades that characteristic timescales can be seen in the X-ray lightcurves of Galactic black hole systems. The timescales are short (< second) and so can be found in short observations. However to find the equivalent timescales in AGN is much harder as we must observe for months or years."

The research is published in the current (December 7) edition of Nature. ®

Top 5 reasons to deploy VMware with Tegile

More from The Register

next story
Bond villains lament as Wicked Lasers withdraw death ray
Want to arm that shark? Better get in there quick
Renewable energy 'simply WON'T WORK': Top Google engineers
Windmills, solar, tidal - all a 'false hope', say Stanford PhDs
SEX BEAST SEALS may be egging each other on to ATTACK PENGUINS
Boffin: 'I think the behaviour is increasing in frequency'
Reuse the Force, Luke: SpaceX's Elon Musk reveals X-WING designs
And a floating carrier for recyclable rockets
The next big thing in medical science: POO TRANSPLANTS
Your brother's gonna die, kid, unless we can give him your, well ...
NASA launches new climate model at SC14
75 days of supercomputing later ...
Britain's HUMAN DNA-strewing Moon mission rakes in £200k
3 days, and Kickstarter moves lander 37% nearer takeoff
Antarctic ice THICKER than first feared – penguin-bot boffins
Robo-sub scans freezing waters, rocks warming models
Your PHONE is slowly KILLING YOU
Doctors find new Digitillnesses - 'text neck' and 'telepressure'
prev story

Whitepapers

Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
10 threats to successful enterprise endpoint backup
10 threats to a successful backup including issues with BYOD, slow backups and ineffective security.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
The hidden costs of self-signed SSL certificates
Exploring the true TCO for self-signed SSL certificates, including a side-by-side comparison of a self-signed architecture versus working with a third-party SSL vendor.