Eoin Gorman
Staff Writer
Dr. Graham Harper, an astrophysicist working at Trinity College, took part in an expedition aboard SOFIA, jointly operated by NASA and DLR – the German Space Agency – earlier this month. The purpose of the expedition was to observe the star Betelgeuse.
Betelgeuse, a red supergiant star in the Orion constellation – one of the largest stars ever recorded – has been shedding it outer layers for over half a century. Scientists are uncertain as to why this is occurring. SOFIA, which stands for Stratospheric Observatory For Infrared Astronomy, began life as a Boeing 747-SP, but it is no ordinary aeroplane. It is equipped with a reflecting telescope which is 2.5 metres across and point through an aperture in the side of the aircraft.
SOFIA was used to investigate the phenomenon as it flies at up to 45,000 feet, at which point it is above all but 0.2% of the water vapour in the Earth’s atmosphere. This affords astronomers the opportunity to see things which are not visible from observatories on the surface of the earth. Atmospheric water vapour blocks observation of the wavelength of the spectral line observed on the flight from the ground.
Dr. Harper, who arrived at TCD in September 2009, was accompanied by three physicists from institutions in the United States of America, Dr. Matthew Richter of the University of California Davis, Dr. Alexander Brown of the University of Colorado at Boulder and Dr. Joanna Brown of the Harvard-Smithsonian Center for Astrophysics. He studied lines of carbon monoxide molecules in the gases leaving the star, which is also known as Alpha Orionis. He used GREAT (the German Receiver for Astronomy at Terahertz Frequencies), an infrared heterodyne spectrometer, to do so. The spectrometer was created by a team led by Rolf Güsten from the Max-Plack-Institute for Radio Astronomy.
The flight departed from Palmdale, California and lasted nearly ten hours. After initial data was gathered, significant difficulties with the telescope computer software aboard SOFIA arose. However, through cooperation between the scientists and the pilots, the problem was bypassed and spectra of carbon monoxide in the vicinity of Betelgeuse were successfully gathered.
The data from the SOFIA flight will now be analysed by Dr. Harper’s research group at Trinity, which includes the PhD students Sarah Kennelly and Eamon O’Gorman and Neal O’Riain. It will be collated with data obtained by the Hubble Space Telescope, millimetre radio inferometry and ground-observatory based infrared spectra. This data will be supplied by Dr. T.R, Ayres of the University of Colorado and Dr. Kenneth Carpenter (GSFC), Dr. Joanna Brown and Eamon O’Gorman and Dr. Nils Ryde, who works at Lund University in Sweden.
Initial analysis, however, has indicated that the carbon monoxide emissions are coming from an outflow which travels at speeds as fast as 9 kilometres per second away from Betelgeuse and which is roughly symmetrical around the star.
