Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

’Spitting’ star imitates black hole

15.01.2004


Scientists using CSIRO’s Australia Telescope Compact Array, a radio synthesis telescope in New South Wales, Australia, have seen a neutron star spitting out a jet of matter at very close to the speed of light. This is the first time such a fast jet has been seen from anything other than a black hole.


Artist’s impression of an X-ray binary system like Circinus X-1
Credit: NASA.



The discovery, reported in this week’s issue of ’Nature’, challenges the idea that only black holes can create the conditions needed to accelerate jets of particles to extreme speeds.

"Making jets is a fundamental cosmic process, but one that is still not well understood even after decades of work," says team leader Dr. Rob Fender of the University of Amsterdam.


"What we’ve seen should help us understand how much larger objects, such as massive black holes, can produce jets that we can see half-way across the Universe."

The scientists, from The Netherlands, the UK and Australia, studied Circinus X-1, a bright and variable source of cosmic X-rays, over a three-year period.

Circinus X-1 lies inside our Galaxy, about 20 000 light-years from Earth, in the constellation Circinus near the Southern Cross.

It consists of two stars: a ‘regular’ star, probably about 3 to 5 times the mass of our Sun, and a small compact companion.

"We know that the companion’s a neutron star from the kind of X-ray bursts it’s been seen to give off," says team member Dr. Helen Johnston of the University of Sydney.

"Those X-ray bursts are a sign of a star that has a surface. A black hole doesn’t have a surface. So the companion must be a neutron star."

A neutron star is a compressed, very dense ball of matter formed when a giant star explodes after its nuclear fuel runs out. In the hierarchy of extreme objects in the Universe, it is just one step away from a black hole.

The two stars in Circinus X-1 interact, with the neutron star’s gravity pulling matter off the larger star onto the neutron star’s surface.

This ‘accretion’ process generates X-rays. The strength of the X-ray emission varies with time, showing that the two stars of Circinus X-1 travel around each other in a very elongated orbit with a 17 day period.

"At their point of closest approach, the two stars are almost touching," says Dr. Johnston.

Since the 1970s astronomers have known that Circinus X-1 produces radio waves as well as X-rays. A large ‘nebula’ of radio emission lies around the X-ray source. Within the nebula lies the new-found jet of radio-emitting material.

Jets are believed to emerge, not from black holes themselves, but from their ‘accretion disk’ – the belt of dismembered stars and gas that a black hole drags in towards it.

In Circinus X-1 it’s likely that the accretion disk varies with the 17-day cycle, being at its most intense when the stars are at their closest point in the orbit.

The jet from Circinus X-1 is travelling at 99.8% of the speed of light. This is the fastest outflow seen from any object in our Galaxy, and matches that of the fastest jets being shot out of other complete galaxies. In those galaxies, the jets come from supermassive black holes, millions or billions of times the mass of the Sun, that lie at the centres of the galaxies.

Whatever process accelerates jets to near the speed of light, it does not rely on the special properties of a black hole.

"The key process must be one common to both black holes and neutron stars, such as accretion flow," says Dr. Kinwah Wu of Unversity College London, UK.

TEAM MEMBERS
Rob Fender (University of Amsterdam, NL)
Kinwah Wu (University College London, UK)
Helen Johnston (University of Sydney, Australia)
Tasso Tzioumis (Australia Telescope National Facility, Australia)
Peter Jonker (University of Cambridge, UK)
Ralph Spencer (Jodrell Bank / University of Manchester, UK)
Michiel van der Klis (University of Amsterdam, NL)

Helen Sim | alfa
Further information:
http://www.atnf.csiro.au/
http://www.aao.gov.au

More articles from Physics and Astronomy:

nachricht Immortal quantum particles: the cycle of decay and rebirth
14.06.2019 | Technische Universität München

nachricht Small currents for big gains in spintronics
13.06.2019 | University of Tokyo

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: The hidden structure of the periodic system

The well-known representation of chemical elements is just one example of how objects can be arranged and classified

The periodic table of elements that most chemistry books depict is only one special case. This tabular overview of the chemical elements, which goes back to...

Im Focus: MPSD team discovers light-induced ferroelectricity in strontium titanate

Light can be used not only to measure materials’ properties, but also to change them. Especially interesting are those cases in which the function of a material can be modified, such as its ability to conduct electricity or to store information in its magnetic state. A team led by Andrea Cavalleri from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg used terahertz frequency light pulses to transform a non-ferroelectric material into a ferroelectric one.

Ferroelectricity is a state in which the constituent lattice “looks” in one specific direction, forming a macroscopic electrical polarisation. The ability to...

Im Focus: Determining the Earth’s gravity field more accurately than ever before

Researchers at TU Graz calculate the most accurate gravity field determination of the Earth using 1.16 billion satellite measurements. This yields valuable knowledge for climate research.

The Earth’s gravity fluctuates from place to place. Geodesists use this phenomenon to observe geodynamic and climatological processes. Using...

Im Focus: Tube anemone has the largest animal mitochondrial genome ever sequenced

Discovery by Brazilian and US researchers could change the classification of two species, which appear more akin to jellyfish than was thought.

The tube anemone Isarachnanthus nocturnus is only 15 cm long but has the largest mitochondrial genome of any animal sequenced to date, with 80,923 base pairs....

Im Focus: Tiny light box opens new doors into the nanoworld

Researchers at Chalmers University of Technology, Sweden, have discovered a completely new way of capturing, amplifying and linking light to matter at the nanolevel. Using a tiny box, built from stacked atomically thin material, they have succeeded in creating a type of feedback loop in which light and matter become one. The discovery, which was recently published in Nature Nanotechnology, opens up new possibilities in the world of nanophotonics.

Photonics is concerned with various means of using light. Fibre-optic communication is an example of photonics, as is the technology behind photodetectors and...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Novel communications architecture for future ultra-high speed wireless networks

17.06.2019 | Information Technology

Climate Change in West Africa

17.06.2019 | Earth Sciences

Robotic fish to replace animal testing

17.06.2019 | Ecology, The Environment and Conservation

VideoLinks
Science & Research
Overview of more VideoLinks >>>