SPIRE spectrum of the Orion Bar
This is one of the early spectra obtained with the SPIRE fourier transform spectrometer on Herschel. The spectrum is of one position on the Orion Bar, a region in the massive star-forming Orion Nebula. At this position the gas on the edge of the nebula is partly ionised by the intense radiation from nearby hot young stars.
A forest of carbon monoxide (CO) features, appearing as the dominating narrow lines, is seen here for the first time together in a single spectrum. They will be used to estimate the temperature and density of interstellar gas in a manner completely unprecedented in the history of molecular line astronomy.
The spectrum also contains the first detection of the emission feature at 835 GHz from the molecular ion methylidynium (CH+). This is a key building block for larger carbon-bearing molecules. The exact frequency of this feature has only been recently precisely measured in the laboratory. The study of this feature in a number of regions will shed light on the formation processes and on the existence of CH+.
The inset shows a near infrared picture of the region from NASA’s Spitzer Space Telescope.
This SPIRE FTS observation was carried out as part of the performance verification of the observatory. The scientific rights of this observation are owned by the Evolution of Interstellar Dust Key Programme consortium led by A. Abergel.