Seeing Hertford in a New Light

2 February 2023

Tutorial Fellow in Physics Pat Roche has been part of a college-wide survey looking at how we can best reduce our energy-based carbon footprint. Pat has been using a thermal imager to detect heat escape, and in the process created a very different view of the much-photographed Bridge of Sighs! Below, Pat outlines the process, and how his involvement with the carbon net zero project relates to the James Webb Space Telescope…

Pat Roche writes: “As part of our investigation into energy use and reduction within college, I have been using a thermal imager to search for areas of heat escape. This is a rarely seen view of the Hertford Bridge, imaged on the morning of January 17 at a wavelength of 10 microns, which picks up heat radiation. Warmer areas appear red or white, with cold areas appearing blue or black. This was a cold morning and the stonework is at a temperature of about -4 C with the single-glazed windows appearing warmer, but still below freezing. There is no heating in the bridge and so there is not much contrast between the windows and stonework there. At these wavelengths, a clear sky is quite transparent and so appears very cold with an effective temperature of about -40 C.”

“For my astronomical research, I have built and used instruments operating at the same wavelength on telescopes in Hawaii, Chile and Australia to investigate the properties of cosmic dust in many astronomical objects from comets and planets to the centres of galaxies including our own Milky Way. Now, the James Webb Space Telescope has dramatically enhanced the sensitivity and resolution of such measurements, producing beautiful images and spectra that are leading to new insights and discoveries. At Oxford Astrophysics, we are analysing some of these data, and have published some of the first results.”