A hundred thousand supernovae

Click image for full size version. Image: ESO/Francisco Nogueras Lara et al.

Countless stars fill the scene in this revealing infrared view of the central region of our Galaxy, the Milky Way. It’s been imaged by the HAWK-I infrared camera on the Very Large Telescope in Chile. Infrared light permeates through the obscuring dust that fills the galaxy, allowing HAWK-I a clear insight into the interior. The bright region in the centre is home to the four-million-solar-mass black hole Sagittarius A*, but that’s not what makes this image so special. It’s part of a study of the history of the stars in the galactic centre.

Astronomers led by Rainer Schödel, of the Institute of Astrophysics of Andalusia, in Granada, in Spain, have found that 80 per cent of the stars now in the galactic centre were born between 8 and 13.5 billion years ago. Then, for a period starting eight billion years ago and lasting until just a billion years ago, very few stars at all were born in the galactic centre. Then, something dramatic must have happened, because Schödel’s team have found evidence for a starburst so intense that more than a hundred stars were being born every year, for a period lasting about 100 million years. These stars would have led to 100,000 supernovae in that period, rivalling the most extreme star-forming regions in the known Universe. It’s not known what caused this acceleration in star formation – perhaps it resulted from a minor collision with a huge gas cloud or dwarf galaxy, or something else entirely.