Cosmic particle accelerators get things going

Nov 17, 2011
This composition shows a number of diverse astronomical sources where shocks have been detected. Shock waves arise when supersonic flows of plasma are faced with an obstacle, such as a planet or a star with a magnetic field, or when they encounter a slower moving flow. Depicted in the composition are: a bow shock around the very young star, LL Ori, in the Great Orion Nebula (upper row, left image); shock waves around the Red Spider Nebula, a warm planetary nebula (upper row, central image); very thin shocks on the edge of the expanding supernova remnant SN 1006 (central row, left image); artist's impressions of the bow shock created by the Solar System as it moves through the interstellar medium of the Milky Way (upper row, right image) and of Earth's bow shock, formed by the solar wind as it encounters our planet's magnetic field (central row, right image); shock-heated shells of hot gas on the edge of the lobes of the radio galaxy Cygnus A (lower row, left image); a bow shock in the hot gas in the merging galaxy cluster 1E 0657-56, also known as the 'Bullet Cluster'. The image of a galaxy (NGC 6744) in the centre of the composition serves to give a rough idea of the relative scales, sub- and super-galactic alike, of the shock waves present across the Universe. Credit: NASA/ESA and The Hubble Heritage Team STScI/AURA

(PhysOrg.com) -- ESA's Cluster satellites have discovered that cosmic particle accelerators are more efficient than previously thought. The discovery has revealed the initial stages of acceleration for the first time, a process that could apply across the Universe.

All particle accelerators need some way to begin the acceleration process. For example, the at CERN employs a series of small accelerators to get its particles up to speed before injecting them into the main 27 km-circumference ring for further acceleration.

In space, large magnetic fields guide particles known as across the Universe at almost the , but are notoriously bad at getting them moving in the first place.

Now ESA's has shown that something similar to the 'staging' process used at is happening above our heads in the natural of space.

On 9 January 2005, Cluster's four satellites passed through a magnetic shock high above Earth. The spinning craft were aligned almost perfectly with the magnetic field, allowing them to sample what was happening to on very short timescales of 250 milliseconds or less.

The measurements showed that the electrons rose sharply in temperature, which established conditions favourable to larger scale acceleration.

Cosmic particle accelerators get things going
Artist's impression of the four Cluster spacecraft flying through the thin layer of Earth's bow shock. The crossing, which took place on 9 January 2005, showed that the shock's width was only about 17 kilometres across. Credits: ESA/AOES Medialab

It had long been suspected that shocks could do this, but the size of the shock layers and the details of the process had proved difficult to pin down. Not any more.  

Steven J. Schwartz, Imperial College London, and colleagues used the Cluster data to estimate the thickness of the shock layer. This is important because the thinner a shock is, the more easily it can accelerate particles.

"With these observations, we found that the shock layer is about as thin as it can possibly be," says Dr Schwartz.

Thin in this case corresponds to about 17 km. Previous estimates had only been able to tie down the width of the shock layers above Earth at no more than 100 km.

This is the first time anyone has seen such details of the initial acceleration region.

The knowledge is important because shocks are everywhere in the Universe. They are created wherever a fast-flowing medium hits an obstacle or another flow.

For example, a supersonic aeroplane collides continuously with the atmosphere before the air has a chance to get out of the way, piling it up into a shock in front of the aircraft that we hear as a sonic boom.

In the Solar System, the Sun gives out a fast-moving, electrically charged wind. As it encounters the of Earth, a permanent shock wave is created in front of our planet.

Cluster has been instrumental in studying this phenomenon and the new results in this local environment may be applicable on large scales. Shocks are also found around exploding stars, young stars, black holes and whole galaxies. Space scientists suspect that these may be the origin of the high-energy cosmic rays that fill the Universe.

Cluster has shown that very narrow shocks may be vital to kick-starting the acceleration process in those locations. It may not be the only way of starting things off, but it is definitely one way of doing it.

"This new result reveals the size of the proverbial 'black box', constraining the possible mechanisms within it involved in accelerating ," says Matt Taylor, ESA Cluster project scientist.

"Yet again, Cluster has provided us with a clear insight into a physical process that occurs throughout the Universe."

Explore further: A star's early chemistry shapes life-friendly atmospheres

Related Stories

Shocking recipe for making killer electrons (w/ Video)

Mar 11, 2010

Take a bunch of fast-moving electrons, place them in orbit and then hit them with the shock waves from a solar storm. What do you get? Killer electrons. That's the shocking recipe revealed by ESA's Cluster ...

Cluster encounters a natural particle accelerator

Feb 01, 2011

(PhysOrg.com) -- ESA's Cluster satellites have flown through a natural particle accelerator just above Earth's atmosphere. The data they collected are unlocking how most of the dramatic displays of the northern ...

A Super-Efficient Particle Accelerator

Jul 01, 2009

This image of data from NASA's Chandra X-ray Observatory and the European Southern Observatory's Very Large Telescope shows a part of the roughly circular supernova remnant known as RCW 86.

Recommended for you

Professional and amateur astronomers join forces

3 hours ago

(Phys.org) —Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time. These amateur astronomers devote hours ...

A star's early chemistry shapes life-friendly atmospheres

Apr 23, 2014

Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless ...

Image: X-raying the cosmos

Apr 22, 2014

When we gaze up at the night sky, we are only seeing part of the story. Unfortunately, some of the most powerful and energetic events in the Universe are invisible to our eyes – and to even the best optical ...

Mysteries of nearby planetary system's dynamics solved

Apr 22, 2014

Mysteries of one of the most fascinating nearby planetary systems now have been solved, report authors of a scientific paper to be published by the journal Monthly Notices of the Royal Astronomical Society in its ...

User comments : 0

More news stories

Habitable exoplanets are bad news for humanity

Last week, scientists announced the discovery of Kepler-186f, a planet 492 light years away in the Cygnus constellation. Kepler-186f is special because it marks the first planet almost exactly the same size as Earth ...

Professional and amateur astronomers join forces

(Phys.org) —Long before the term "citizen science" was coined, the field of astronomy has benefited from countless men and women who study the sky in their spare time. These amateur astronomers devote hours ...

First-of-its-kind NASA space-weather project

A NASA scientist is launching a one-to-two-year pilot project this summer that takes advantage of U.S. high-voltage power transmission lines to measure a phenomenon that has caused widespread power outages ...

New breast cancer imaging method promising

The new PAMmography method for imaging breast cancer developed by the University of Twente's MIRA research institute and the Medisch Spectrum Twente hospital appears to be a promising new method that could ...

Research proves nanobubbles are superstable

The intense research interest in surface nanobubbles arises from their potential applications in microfluidics and the scientific challenge for controlling their fundamental physical properties. One of the ...

Using antineutrinos to monitor nuclear reactors

When monitoring nuclear reactors, the International Atomic Energy Agency has to rely on input given by the operators. In the future, antineutrino detectors may provide an additional option for monitoring. ...