The Horse and the Dragon

Long caption: Scrutinising several hundred thousand galaxies observed at infrared and submillimetre wavelengths by ESA’s Herschel space observatory, astronomers have identified a very rare instance of a massive object in the very early Universe.

The Herschel survey is shown in the background, combining data collected at 350 micron (blue) and 500 micron (green).

The inset at the centre shows a zoom around the potentially interesting source, combining the Herschel view with follow-up observations performed at 870 micron with the Atacama Pathfinder Experiment (APEX; red).

Further observations obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) at higher resolution (right inset) revealed that the source consists not just of one ancient, massive galaxy, but of a pair of distinct massive galaxies about to merge.

These two galaxies, each roughly as massive as our Milky Way, were informally dubbed the ‘Horse’ and the ‘Dragon’.

Full story: Herschel discovers galaxy merger in the very early Universe