ESA's 'Herschel Space Observatory' will find out the nature of the first galaxies.How much energy has been released throughout the history of the Universe? As surprising as it may seem, astronomers can deduce that value. Most of the energy is 'locked' in a faint 'glow' that fills the whole universe, and is the remnant of all the energy emitted in the remote past by the first galaxies. That glow, called the 'infrared background radiation', was first detected a few years ago. Now the big question for astronomers is: 'what' were the sources that created the glow? No telescope so far has been able to 'pinpoint' those primeval galaxies to say what they were. ESA's next infrared space telescope, FIRST, is the only instrument able to do the job, as concluded yesterday by astronomers gathered in Toledo (Spain).