Spectrum of the helium hydride ion
Spectrum of the helium hydride ion
Spectrum of the helium hydride ion (HeH+), detected using the GREAT instrument on board the SOFIA airborne observatory, observing in the direction of the planetary nebula NGC 7027. The background image of NGC 7027 was generated using data acquired by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) installed on board the Hubble Space Telescope. The obvious area of transition between the hot ionised gas (yellowish-white) and the cooler shell (red) is clearly visible. It is in this transition zone that HeH+ is formed (marked with molecule symbols in the artist’s impression). The area of the sky captured by the GREAT measurements has a diameter of 14.3 arc seconds and includes most of the radiation from the planetary nebula. The width of the HeH+ spectral line is the result of the propagation velocity of the expanding shell.
