E-Merlin array starts to work its magic

UK astronomers have quietly completed a £25 million upgrade to a network of radio telescopes based at Jodrell Bank that has turned them into a supercharged listening station tuned into the heavens.

The Lovell Dish at Jodrell Bank is part of e-Merlin. Credit: Paul Sutherland
The Lovell Dish at Jodrell Bank is part of e-Merlin. Credit: Paul Sutherland

While the world was focusing on the new ALMA dishes in Chile and the battle to site the Square Kilometre Array in South Africa or Australia, ten years of work back home came to an end.

Seven radio dishes across England that previously operated as Merlin have been linked by superfast fibre-optic cables to form a new single giant telescope called e-Merlin. It is observing the Universe in the same resolution, or detail, as NASA’s iconic Hubble Space Telescope but is collecting data at at a phenomenal rate.

The individual dishes spanning 217 km (135 miles) of countryside have been fitted with advanced new electronic receivers and connected with 690 km (430 miles) of fibre-optic cables so that they work together as one instrument. It means the array of telescopes, which together act like a zoom lens on the Universe, can now gather as much observational data in a single day as took them a year before.

The combined telescope will take detailed pictures out towards the edge of the Universe. It promises to answer questions such as how stars and galaxies are born and evolve, and what causes explosive jets from black holes. Massive lenses have been fitted to three of the instruments so that the combined telescope can be switched rapidly to examine different areas of the hidden part of the spectrum that exists beyond visible light.

As well as laying 90 km (56 miles) of new dedicated lines, e-Merlin is also leasing fibres on commercial cables that carry high-speed broadband. Previously Merlin leased ordinary phone lines. Now the information is pouring in from each telescope at the rate of 30 gigabits a second – equivalent to downloading a 10 MB file every third of a second.

The seven dishes include Jodrell Bank’s iconic Lovell Telescope near Manchester, the Mark II telescope on the same site and others at Cambridge, Defford, Knockin, Darnhall and Pickmere. They were first linked as Merlin, short for the Multi-Element Radio Linked Interferometer Network, in 1980.

This spring, final construction work was completed on the Cambridge dish and at Jodrell Bank to complete e-Merlin. Fine-tuning is continuing but the first observation was made of a star-forming region within our own Milky Way galaxy, in the constellation of Cygnus.

Data streaming in from e-Merlin is collected by a powerful computer called a correlator that was designed and built in Canada. The digital and optical transmission equipment was designed in collaboration with the National Radio Astronomy Observatory in the US and is similar to that working at ALMA, the world’s highest observatory, in Chile’s Atacama Desert.

Jodrell Bank’s Director Albert Zijlstra told me: “Compared to the old Merlin, the telescope’s power has improved by a factor of 20 to 30. We are still optimising and improving it but this is a completely new ball game.”

The astronomers are collecting half a terabyte of data every day – as much as can be stored on more than 100 DVDs. But that has produced a headache for astronomers who are suddenly awash with more information than they can handle.

Professor Zijlstra said: “There is so much data that we deal with it with great difficulty. It is not just astronomy that has this problem. The Large Hadron Collider has a similar problem in producing so much information to deal with.

“With e-Merlin, the signals from the telescopes go into the correlator, an impressive computer at Jodrell Bank, where they are combined and reduced to a rate that we can handle. It then all goes into an archive where it is stored.

“Typically you only look at a fraction of the data that is received. It is very hard to image a whole field of view in one go because it is so big. So we select an area that we think is interesting and see what is there.”

A black hole recorded during e-Merlin's testing phase.
A black hole recorded during e-Merlin’s testing phase. Credit: University of Manchester

He added: “It is very easy to miss things. They can be hidden in the data in places you weren’t looking. But in the future people can examine the data and researchers will be able to make new discoveries in the archive. Also computers are getting smarter and we try to tell the computers the kind of things we are looking for and get them to examine the data.”

Asked if e-Merlin was like Hubble on steroids, Prof Zijlstra said: “I prefer to call it Hubble on the cheap! The space telescope has cost around £4 billion. Compared to that, e-Merlin has been a bargain.”

One of the test radio images taken during commissioning of e-Merlin could reveal a double black hole. Jodrell Bank’s associate director Dr Tim O’Brien said: “It shows quasar, a distant galaxy with a super-massive black hole at its heart, in the constellation of Coma Berenices.

“But it’s a long way away.The light travel time from this object is about 4.5 billion years, which means we are seeing at about the same time as the Earth was being formed. The region around the black hole is the brightest spot right in the middle of the image.”

Dr O’Brien added: “A jet is being shot out from this region almost directly towards us seen heading out to the left and probably more than half a million light years long. The jet appears to be corkscrewing, possibly because the black hole is being orbited by a companion black hole. If so, this binary black hole would have arisen from the merger of two galaxies, each hosting a black hole.”

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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