Radio astronomers boost their vision

Thursday, 11 August, 2005



Radio astronomers at Britain's Jodrell Bank Observatory, working with colleagues from Europe and the US, have demonstrated a technique they say will revolutionise the way they observe.

To create images of the sky that are as detailed as possible, they routinely combine data from a number of radio telescopes from around the world - a technique called very long baseline interferometry (VLBI).

They have now combined this with the power of dedicated internet resources to send data from all the instruments to a special computer, to combine the observations in real time in a system called e-VLBI.

In conventional interferometry, radio astronomers have to wait weeks or even months to see the results of their work after data tapes are shipped across the globe to be combined at a central processing facility.

Jodrell Bank's Prof Phil Diamond said "Previously, we have been working in the dark, collecting data that we can't see in its entirety until painfully long weeks later.

"Now, using e-VLBI, we have removed that blindfold; we can process the observations taken at a number of locations around the world at once, in real time.

"In future, this technique will allow us to take much better images than previously possible, revealing in much greater detail the universe around us."

e-VLBI uses dedicated internet infrastructures (called research networks) in the participating countries, so that data from all the telescopes can be relayed rapidly to a centre in the Netherlands where the data are combined and sent back to the astronomers who then produce the images.

These observations give an exciting glimpse into the future or radio astronomy.

Using research networks, not only will radio astronomers be able to see deeper into the distant universe, they will be able to capture unpredictable, transient events as they happen, reliably and quickly.

The star chosen to demonstrate the system, called IRC+10420, is one of the most unusual in the sky.

Surrounded by clouds of dusty gas and emitting strongly in radio waves, the object is poised at the end of its life, heading towards a cataclysmic explosion known as a 'supernova'.

One of the brightest infrared sources in the sky, it is surrounded by a thick shell of dust and gas thrown out from the surface of the star at a rate of about 200 times the mass of the earth every year.

Radio astronomers are able to image the dust and gas surrounding IRC+10420 because one of the component molecules, hydroxyl (OH), reveals itself through strong maser (microwave amplification by stimulated emission of radiation) signals.

Essentially, the astronomers see clumps of gas where radio emission in the microwave band is strongly amplified by special conditions.

With the 'zoom lens' provided by e-VLBI, astronomers can make images with great detail and watch the clumps of gas move, watch masers being born and die on timescales of weeks to months and study the changing magnetic fields that permeate the shell.

The results show that the gas is moving at about 40 km/s and was ejected from the star about 900 years ago.

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