A trip to a radio telescope

Over the East holidays last year, I took a trip up to Jodrell Bank observatory in Cheshire with a fellow physics enthusiast, who kindly organised the logistics and thought of the trip, for an astronomy themed adventure. Nestled in the countryside south of Manchester between farms and fields, it is not surprising this historic place is listed as a UNESCO World Heritage Site. We took a train to the nearby village of Goostrey and walked about 4 km from there to reach it, where we proceeded to spend a fun day learning about astronomy, engineering, history and the lives of people behind some great discoveries in astrophysics. 

Behind me in the first picture is the enormous Lovell Telescope, a steerable radio telescope measuring 76m across that is the third largest of its kind in the world, although when it was built back in 1957, it was the biggest. Its impressive size and technical complexity is a feat of engineering even by modern standards. World leading research on galaxies, black holes and exploded stars is carried out with it. The finished telescope differs somewhat from the original plan, owing to the discovery by American astronomers of the ‘21 cm Hydrogen line’ while it was being constructed. This is a radio signal of wavelength 21 cm produced by cold, interstellar hydrogen atoms when the universe was a fraction of its current age, the discovery of which kickstarted the area of radio astronomy. As a result, the finished telescope has a much smoother surface than the originally planned mesh construction to allow for more detailed observations at shorter wavelengths. The signal’s discovery allows us to map the gas structure both within our galaxy and far beyond.  

The Lovell telescope has played an important part in the study of quasars; supermassive black holes in the centre of galaxies surrounded by orbiting gas discs. Quasars are some of the brightest objects in our universe, as their extreme luminosity is caused by the friction of vast amounts of gas falling towards a central black hole, heating up to high temperatures and releasing light as radio waves. The telescope has also been used to observe pulsars; a type of neutron star that rotates rapidly and is made of a massive star’s collapsed core. These cores are unbelievably dense, the equivalent of cramming the entire mass of the Sun into a city sized sphere. In 2005 the Lovell telescope discovered a galaxy named VIRGOHI21 which made a big contribution to the study of dark matter. The exact constituents of dark matter are still a mystery today as it does not interact with light and is therefore difficult to detect. However, its presence has been inferred from observations of galaxies such as VIRGOHI21 which, if made of observable material alone, would not have enough mass to hold together while rotating at the speed it does without flinging itself apart. The conclusion is therefore that this galaxy has extra mass that we cannot see directly, such as dark matter, giving it enough gravity to hold itself together. 

Having learnt about the magnificent Lovell telescope, we headed inside for our pre-booked talk in the auditorium where some enthusiastic scientists at the observatory gave us an immersive lecture (with pretty pictures!) on a brief overview of astronomy, starting from Earth taking us all the way to other planets and the stars. It was highly enjoyable and educational without losing its fun, as could be seen by the queue of curious children afterwards lining up to ask the scientists questions. A series of displays and mini experiments in the adjacent room afterwards further brought the astrophysics to life. 

The site also hosts a small museum, handy on days when it is raining, where we spent the rest of the afternoon. I was captivated by the letters and sketches of the 18/19th century astronomer Caroline Herschel. While her famous brother William made many notable astronomical discoveries, her contributions have historically been overlooked or credited solely to him. Recently however, her work has been acknowledged by books and museums and she has made a name for herself in her own right. She was a trailblazing pioneer for women in science, becoming the first woman to earn a salary as a scientist in England; the first woman to be awarded a Gold Medal by the Royal Astronomical Society in 1828, and the first woman to publish scientific findings in the Royal Society journal. She lived to the impressive age of 97 and was noted for the discoveries of many comets in her lifetime, including 35P/Herschel-Rigollet, which is named in her honour. From reading her letters it is clear she was a thorough and skilled scientist who worked humbly and diligently. Had she been offered the same opportunities as men were 200 years ago, she may have made even more discoveries. As a young woman studying astronomy myself, it was moving to see just how far we have come from the days of Caroline Herschel, now that women can vote, own property, be educated, study science and even go to the moon! 

Overall it was a thoroughly enjoyable day out, including the part where we got lost hiking across some fields to reach the site and met a friendly farm dog in a cowshed! The trip was highly educational and I would recommend it to anyone interested in learning about astronomy.