Radio Astronomers Remove the Blindfold

UK radio astronomers at the Jodrell Bank Observatory, working with colleagues from Europe and the USA, have demonstrated a new technique that will revolutionise the way they observe. To create the very best quality images of the sky, they routinely combine data from multiple 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 telescopes to a special computer, to combine the observations in real-time (e-VLBI).

In conventional interferometry, far from the traditional image of an astronomer peering through an eyepiece, radio astronomers have to wait weeks or even months to see the results of their work as data tapes are shipped around the world to be combined at a central processing facility.

Prof Phil Diamond, of Jodrell Bank Observatory explains “Previously, we’ve 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 new 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 new observations give an exciting glimpse of the future of radio astronomy. Using research networks, not only will radio astronomers be able to see deeper into the distant Universe, they’ll be able to capture unpredictable, transient events as they happen, reliably and quickly.

The star chosen for this remarkable demonstration, 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 toward a cataclysmic explosion known as a ’supernova’.

Although the scientific goals of the experiment were modest, these e-VLBI observations of IRC+10420 open up the possibility of watching the structures of astrophysical objects as they change. IRC+10420 is a supergiant star in the constellation of Aquila. It has a mass about 10 times that of our own Sun and lies about 15,000 light years from Earth.

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 by means of strong ’maser’ emission. Essentially, the astronomers see clumps of gas where radio emission 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. As Prof. Phil Diamond explained, “The material we’re seeing in this image left the surface of the star at around the time of the Norman Conquest of England”.

It is believed IRC+10420 is rapidly evolving toward the end of its life. At some point, maybe thousands of years from now, maybe tomorrow, the star is expected to blow itself apart in one of the most energetic phenomena known in the Universe – a ’supernova’. The resulting cloud of material will eventually form a new generation of stars and planetary systems. Radio astronomers are now poised, with the incredible power of e-VLBI, to catch the details as they happen and study the physical processes that are so important to the structure of our Galaxy and to life itself.