Approximately 1.5 billion years ago, the universe must have lit up like a stroboscope. At least fifteen percent of the galaxies in those days were so-called starburst galaxies, galaxies that create stars at an enormous speed. That is much more than was previously assumed, Caputi and her team discovered. That also means that many more stars were formed that way, too. These days, starbursts like these barely happen anymore.
Astronomers used to think that galaxies produced stars slowly, bit by bit, with the larger galaxies making more stars than smaller ones. After all, they have more gas to form stars with. The existence of starburst galaxies was known before, but it seemed as though they were only a small part of the total numbers of galaxies.
But Caputi’s observations have changed this view completely. She used data provided by the Spitzer infrared telescope. For 1,800 hours, that telescope observed an area of the sky that contained hundreds of thousands of galaxies. Among them, there were about 6000 galaxies present when the Universe was only 1.5 billion years old, and these are the subject of Caputi’s study.
‘In this research we have taken a deep look into the Universe over a large sky area for the first time ever’, says Caputi. ‘That combination is what led to this discovery.’ This means that they could study a large number of galaxies of different stellar masses in the distant Universe.
It then took the astronomers two years to obtain and analyse the data, the results of which were published in the Astrophysical Journal on the 30th of October.
This means that the reference books will have to be rewritten. ‘It has changed the existing ideas completely’, Caputi says. ‘And it’s a major leap for new research into how stars are formed.’