This illustration combines a view obtained at radio wavelengths of ionised gas at the centre of our Galaxy, the Milky Way (left panel), with a spectrum towards the very centre taken with ESA's Herschel at far-infrared wavelengths (right panel).
The spectrum shows the rich variety of molecules that have been detected in this region, which range from carbon monoxide and water vapour to hydrogen cyanide and many light molecules that play a critical role in the chemistry of the interstellar medium. Some of them have been detected for the first time with Herschel.
These data show that the molecular gas is surprisingly hot – the temperature estimated from the emission from carbon monoxide reaches up to 1000 ºC. The most likely source of heating of the hot molecular gas are shocks that develop as gas orbits around or flows towards Sagittarius A*, the region hosting the supermassive black hole that lies at the centre of the Milky Way.