Reflections on Dublin as a City of Astronomy

Lorraine Hanlon
Sunset is typically a sign that another working day is over. City lights are slowly switched on as people return home eager to enjoy the evening and a good night’s sleep. However, this does not apply to astronomers working at an observatory such as ESO’s Paranal Observatory in Chile. Observing starts as soon as the Sun has disappeared below the horizon. Everything needs to be ready before dusk. This panoramic photograph captures the ESO Very Large Telescope (VLT) against a beautiful twilight on Cerro Paranal. The enclosures of the VLT stand out in the picture as the telescopes in them are readied for a night of studying the Universe. The VLT is the world’s most powerful advanced optical telescope, consisting of four Unit Telescopes with primary mirrors 8.2 metres in diameter and four movable 1.8-metre Auxiliary Telescopes (ATs), which can be seen in the left corner of the image. The telescopes can also work together as a single giant telescope, the ESO Very Large Telescope Interferometer (VLTI), which allows astronomers to observe the finest possible detail. This configuration is only used for a limited number of nights per year. Most of the time, the 8.2-metre Unit Telescopes are used individually. Over the past 13 years, the VLT has had a huge impact on observational astronomy. With the advent of the VLT, the European astronomical community has experienced a new age of discoveries, most notably, the tracking of the stars orbiting the Milky Way’s central black hole and the first image of an extrasolar planet, which are two of the top three of ESO’s Top 10 Astronomical Discoveries. The VLT’s four Unit Telescopes are named after celestial objects in Mapuche, which is an ancient native language of the indigenous people of Chile and Argentina. From left to right, we have Antu (UT1; the Sun), Kueyen (UT2; the Moon), Melipal (UT3; the Southern Cross) and Yepun (UT4; Venus). This photograph was taken by ESO Photo Ambassador, Babak Tafreshi. This image is avail
Our city and the stars

Lorraine Hanlon is professor of astronomy at UCD and is getting to an age where she finds the history of science quite interesting, but still not as interesting as its future. Her research interests are (mainly) in discovering catastrophic stellar explosions with robotic telescopes and with gamma-ray instruments in space.

Dubliners were treated to spectacular projected images of the Sun from space during City of Physics.

Dublin’s tradition in astronomy, and related technology development, is a distinguished one. During the last decades of the nineteenth century, the most important telescope manufacturers in the world were based in Rathmines, having outgrown their original premises near Charlemont Bridge. The Grubb ‘Optical and Mechanical Works’, constructed in the 1870’s by Thomas, and his son Howard, employed 35-40 people at its peak.

Their technological advances, beyond those of Fraunhofer in Munich, included vital improvements to the positional stability of telescope axes and new mirror polishing techniques. One of Grubb’s earliest commissions, to provide a mounting for the Sheepshanks refractor for the Royal Observatory in Greenwich, was deemed a success by the distinguished Astronomer Royal, George Airy, and was used to observe comet Encke in the late 1830’s.

The first Grubb telescope to use a mirror (rather than a lens) was built in Armagh Observatory and it has considerable historical importance as the first reflector of good size on a mount that could track  the rotation of the sky. There are still many examples of Grubb telescopes around the world. On a recent visit to the University of Barcelona, I was delighted to walk into the lobby of the Physics Department and see their ‘Dublin telescope’ on proud display. Local stargazers can enjoy the spectacle of a Grubb telescope by visiting Dunsink Observatory near Castleknock.

Thomas Grubb did not just dedicate his business to telescope making. The company’s optical interests extended beyond telescopes to include microscopes and later, periscopes, for which many patents were held. By becoming `Engineer to the Bank of Ireland’ in the 1840’s Thomas developed intricate machinery for the engraving, printing and numbering of banknotes, thus realising the dream of many astronomers to have a license to print money.

Cities like Dublin are not ideal places from which to do optical astronomy – too much light pollution and too many cloudy nights. These days, telescopes are built at high altitudes and in the driest places on earth. A prime example is the world’s most advanced visible-light astronomical observatory, the ‘Very Large Telescope’ (VLT) of the European Southern Observatory (ESO), located at 2.6 km altitude in Cerro Paranal, Chile. Such machines need international teams of hundreds of scientists and engineers to provide the budget, expertise and the manpower to turn inspired vision into magnificent reality.

The innovative spirit and technological prowess that drove the Grubbs and led to their amazing accomplishments is recognisable in modern telescope-builders and astronomers. It is identifiable in the imaginations of our children and in the hopes of our talented students who study science because they dream of unravelling the mysteries of the stars or exploring space.

It is time for our leaders and policy makers to move beyond simply acknowledging our astronomical heritage and past accomplishments. Instead, we must support the 21st century Grubbs (and Grubbettes) currently sitting in classrooms and lecture theatres to realise their own potential, for the benefit of us all. It is time for Ireland to join ESO.