Astronomers have characterised hundreds of previously unseen starburst galaxies, showing extraordinary high star-formation rates across the history of the Universe.
Starburst galaxies give birth to hundreds of solar masses’ worth of stars each year in short-lived but intense events.
By comparison, our own Milky Way Galaxy on average produces the equivalent of only one Sun-like star per year.
Starburst galaxies generate so much starlight that they should outshine our Galaxy hundreds to thousands of times over, but the enormous quantities of gas fuelling them also contain vast amounts of dust as a result of the frantic star formation.
The dust absorbs much of the visible light, meaning that many of them look quite insignificant in that part of the spectrum, the European Space Agency (ESA) said.
However, the dust is warmed by the surrounding hot stars and re-emits the energy at far-infrared wavelengths.
Using ESA’s infrared Herschel space observatory, astronomers measured the temperature and brightness of thousands of dusty galaxies. From these, their star-formation rate could be then calculated.
“Starburst galaxies are the brightest galaxies in the Universe and contribute significantly to cosmic star formation, so it’s important to study them in detail and understand their properties,” says Dr Caitlin Casey of the University of Hawaii, lead author of the study published in Astrophysical Journal.
“Some of the galaxies found in this new survey have star-formation rates equivalent to the birth of several thousand solar-mass stars per year, constituting some of the brightest infrared galaxies yet discovered.”
To provide context to the observations and understand how star formation has changed over the Universe’s 13.7 billion year history, the distances to the galaxies were also needed.
Dr Casey’s team used spectrometers on the twin 10-metre WM Keck telescopes on Mauna Kea, Hawaii, and obtained the redshifts of 767 of the star-burst galaxies.
For most of the galaxies it was found that the light has been travelling towards us for 10 billion years or less.
About 5 per cent of the galaxies are at even greater redshifts: their light was emitted when the Universe was only 1-3 billion years old.