LOFAR-UK at the UK National Astronomy Meeting

Anyone who follows LOFAR (or me) on Twitter probably knows that LOFAR has been well represented at the UK National Astronomy Meeting (NAM) taking place in Llandudno, Wales this week. LOFAR-UK decided to run an exhibit stand to try to educate the UK astronomical community about LOFAR in general and the UK involvement in LOFAR specifically.

Below is the picture of the stand we put up, with 3 large LOFAR-UK banner posters and LOFAR-UK bookmarks (made by SEPnet, who also provided some pencils, postcards and post-it notes to give out), a computer playng a DVD of some of the different LOFAR-UK videos we have on YouTube, brochures describing LOFAR in general (kindly provided by ASTRON), a leaflet about the Chilbolton observatory (provided by STFC), LOFAR-UK pens and post-it notes designed by yours truly, plus printouts of two of the recent press releases (First Light Including Chilbolton Station, and the First Peer Reviewed Science Result from LOFAR) and some other pictures.

Here's a picture of all the give-aways. The pens were a definite hit (described as the best freebie at NAM), and we have just a handful left to giveaway tomorrow (the last day of the meeting).

We also took along a demo low band antenna (LBA) which I'm holding in the below picture. We have used this to illustrate the technique behind putting up the antenna several times at coffee and lunch breaks, and also to the team from the Astronomy Now YouTube Channel. 

 There has been some definite interest, and I have given interviews about LOFAR (and LOFAR-UK) for the Jodcast, The Naked Scientist, the Sky at Night vodcast and Astronomy Now YouTube channel. So stay tuned for those.

 Other LOFAR related events at NAM included a talk by Christian Vocks on observing the Sun with LOFAR (with some interesting information on the Potsdam LOFAR station), plus a plenary lecture on EISCAT-3D (a project using some similar technology to LOFAR).

All in all I think it's gone very well, and I want to say thanks to all the members of the LOFAR-UK community who have helped me to "man the stand" this week. They have included Emma Rigby, Melanie Gendre, Lyndsay Fletcher, Rob Beswick, Somak Raychaudhury, Paul O'Brien and Paul Alexander.

First peer reviewed science from LOFAR

The below press release appears today at ASTRON and Jodrell Bank Observatory in Manchester, describing the first peer reviewed scientific results from the LOFAR telescope, from a team led by LOFAR-UK member Dr. Ben Stappers of the University of Manchester. 

LOFAR takes the pulse of the radio sky

The powerful new International LOFAR telescope, designed and built by ASTRON, is allowing an international team of scientists to have their “best-ever look” at pulsars: rapidly rotating neutron stars, created when massive stars die. In the first refereed scientific results from the new European telescope LOFAR (Low Frequency Array) soon to appear in Astronomy & Astrophysics, the scientists present the most sensitive low-frequency observations of pulsars ever made.

Because of its unique design, LOFAR can observe in many different directions simultaneously. For this image, five pulsars, spread over the entire sky, were observed simultaneously.  

LOFAR is the first in a new generation of massive radio telescopes designed to study the sky at the lowest radio frequencies accessible from the surface of the Earth with unprecedented resolution. Deep observations of pulsars are one of its key science goals.

Lead author on the paper Dr. Ben Stappers, from University of Manchester (UK), said: "We are returning to the frequencies where pulsars were first discovered, but now with a telescope of a sophistication that could not have been imagined back in the 1960s.”

The chance detection of the first pulsar in 1967 is considered one of the great discoveries in astronomy. Astronomers got their first glimpse of pulsars by using a radio telescope sensitive to frequencies of 81MHz (roughly the same frequency as a commercial FM radio station). 

With LOFAR, astronomers have gone back to some of the same techniques used in the first pulsar observations, but have used modern computing and optical fibre connections to increase many times over the power of their telescope. This will allow LOFAR to analyse regular pulses of radio emission and probe such things as the physics of gravity and the properties of the material that pervades our Galaxy.

Dr. Stappers: “Even though these are just the first test results they are already showing spectacular promise.”

LOFAR works by connecting thousands of small antennas spread right across Europe using high speed internet and a massive supercomputer near its central core at ASTRON in the Netherlands.

The LOFAR telescope has no moving parts, instead relying on adding digital time delays to "point" the telescope in a particular direction. This approach offers a much-greater level of flexibility in the way astronomers can analyse the data. For instance, unlike a conventional radio telescope, it is possible to point in multiple directions simultaneously simply by having the computer crunch more data. For astronomers who want to search for new pulsars, this means they can scan the sky much more quickly. 

 Dr. Jason Hessels from ASTRON said: “A traditional radio telescope is limited to viewing a very small fraction of the sky at any one time. LOFAR casts a much broader net, which is going to help us discover new pulsars and detect explosions that were too rare to catch with past in a new approach to understanding these exotic objects.”

The team's next step is to harness LOFAR's capabilities to address some of the long-standing mysteries about how pulsars shine and also to discover nearby pulsars that were missed by past telescopes. "LOFAR has the potential to find all the undiscovered pulsars in the neighbourhood of the Sun and to reveal rare explosions in our Galaxy and beyond. We're very excited to see what's out there." says Dr. Joeri van Leeuwen from ASTRON.

LOFAR is capable of detecting radio waves over a very large range of frequencies, all the way from 10MHz to 240MHz. As well as searching for pulsars, LOFAR will be used for making deep images, cosmology, to monitor the Sun’s activity and study planets. LOFAR will also contribute preparations for the planned global next generation radio telescope, the Square Kilometre Array (SKA).

The full article with the new results can be found here: http://arxiv.org/abs/1104.1577

More information about ASTRON: www.astron.nl

More information about LOFAR:

The International LOFAR telescope is a European collaboration, led by ASTRON Netherlands Institute for Radio Astronomy. By combining thousands of simple antennas with a powerful supercomputer, LOFAR can observe large parts of the sky very fast in different directions simultaneously on relatively unknown low frequencies. This opens up a new window to the universe for astronomers. See also: http://www.astron.nl/lofar-telescope/lofar-telescope.

Aerial photographs of LOFAR-UK Chilbolton

Some dramatic photographs have just been posted on the Press and Media Image Library of the UK's Science and Technology Facilities Council (STFC). These show the LOFAR station at Chilbolton, Hampshire, UK, as seen from the air. Although there are plenty of photographs of various LOFAR stations from the ground, and plenty of diagrams showing the layout of the sites, this is a good opportunity to get a bird's-eye view of what a station looks like.

The credit for all these images goes to Guy Gratton, who took the photographs during the afternoon of Friday 8th April 2011, and who graciously gave permission for their use by the STFC/LOFAR community. The images were taken from an aeroplane flying at an altitude of approximately 300 metres (1000 ft) over the site, through an open door on the aircraft to avoid any window reflections.

Banking away from the LOFAR field, you can see the Chilbolton 25m dish
(Photo: Guy Gratton (c) 2011, hosted by STFC.)

Looking specifically at the LOFAR-UK station (LOFAR-ID = UK608). The HBA is on the left and the LBA is on the right. If you look carefully, you can just make out the RF-container in the space between where the two fields meet and the access road. (Photo: Guy Gratton (c) 2011, hosted by STFC.)

When you start to move further back, more the surrounding facilities become apparent. Apart from the main 25m dish, there is a small 4.5m dish on the right-hand side, just below the LOFAR compound. (Don't forget you can click on images for a slightly enlarged view.)

Looking at the site from even further away, the scale of the Chilbolton Observatory becomes clear. (Photo: Guy Gratton (c) 2011, hosted by STFC.)

The LOFAR-UK site, as seen from the air. 
(Photo: Guy Gratton (c) 2011, hosted by STFC.)

The above photograph is a great way to appreciate the scale of an international LOFAR station. The dish near the top of the photograph is the 25m parabola of the Chilbolton Observatory.

Check the STFC's Press and Media Image Library for all high-quality photographs of the LOFAR-UK station. You can also find full-resolution versions of some of the above photographs, suitable for use in printed media. Thanks goes to the Chilbolton Observatory and UK608 project teams, the RAL-Space outreach team and, of course, Guy Gratton for the great photographs.

How does LOFAR Work Parts 8 and 9 (from the KAIRA blog)

Parts 8 and 9 of the series from the KAIRA blog on how LOFAR works, covering how the array is pointed as specific places on the sky:

8: Steering a Phased Array
9: Digital Beam Steering. 

How does LOFAR Work Part 7 (from the KAIRA blog)

Part 7 of the series from the KAIRA blog on how LOFAR works:

Phased Arrays.

What might LOFAR see of the first stars?

One of the main science drivers for LOFAR is the detection of the point in the history of the Universe when the first stars turned on.

We know that the Universe formed in a Big Bang, after which it was filled a hot soup (plasma) of elementary particles (like electrons, protons, neutrons and photons as well as much more exotic things). When the Universe cooled sufficiently, the electrons combined with the protons to make hydrogen atoms. At that point the photons which had previously been stuck bumping around between the particles could finally stream across the universe - and we see from that time the first light in the Universe - now cooled to microwave radiation (what we call the cosmic microwave background, or CMB).

After the CMB not much happened for a long time. There still wasn't a lot of structure in the Universe - no stars or galaxies. There was nothing to create any light - so we call this period the "dark ages". During this time the material in the Universe ever so slowly collects together under its gravity. Eventually parts of the Universe start getting more and more dense, and the first stars turn on in the densest parts. Suddenly there is light in the Universe once more, and all these new photons hit the hydrogen atoms and strip them of their electrons (ionizing them, but since they started before the CMB as separate protons and electrons, we like to call it "reionization").

As I described in a previous blog post "LOFAR in Sky and Telescope", and you can read about in the May 2011 issue of Sky and Telescope, neutral hydrogen emits a characteristic spectral line at 21cm (1.4 GHz), due to hyperfine splitting of it's ground state. The neutral hydrogen that was around in the Universe just before the first stars turned on was emitting this line, which is now redshifted to much lower frequencies (which we think should be in the range that LOFAR can detect). Suddenly at the redshift which the first stars turned on, the amount of this 21cm emission will drop dramatically. It is this phase change in the Universe which LOFAR hopes to detect.

A slice through a simulation of the reionization of the Universe. Credit Illian Illiev, SEPnet/Sussex

Exactly when and how the first stars turn on in the Universe is an important measurement to further our understanding of cosmology. Researchers involved in LOFAR (and LOFAR-UK) are working on models of what LOFAR and other telescopes like it might see. One such researcher is SEPnet Fellow Dr. Illian Illiev at the University of Sussex. It was his images and animations of what reionization might look like which were used to illustrate the Sky and Telescope article.

Reionization Animation.

Here's a description of the image and animation provided by Illian:

This is what a giant radio telescope like LOFAR is expected to see as it looks deeper into the past (going right) - a sea of neutral hydrogen atoms (yellow) gently excited into emission by the cosmic microwave background photons.

As the very first stars and galaxies form in the universe, some of their radiation is energetic enough to kick out the electron out of the hydrogen atom (a process called ionization), which leads to the gas 'disappearing' from point of view of the radion telescope, illustrated by the blue regions above, growing with time (going left) as more stars form over time.

The variation in the intensity of the yellow across the image indicates regions with different density, the higher the density, the more intensive the colour (since there is higher concentration of emitting atoms there). This is a manifestation of the 'Cosmic Web' of structures - a honeycomb-like structure which forms due to gravity.

How does LOFAR Work Part 6 (from the KAIRA blog)

And they've been busy over at KAIRA, here's also Part 6 in the series in how LOFAR works. Seems this is the end of the preamble, the real details will start soon.

Squinted Vision (about the need to steer radio dishes).