(Phys.org) —Physicists analysing observations from the Herschel Space Observatory have shown that galaxies in the early Universe were cooler than those we see around us today.

The galaxy Messier 82, the closest example of a “starburst galaxy”, seen by NASA’s Spitzer satellite. Credit: NASA/JPL-Caltech

The study draws on the star survey work of the HerMES project led by Professor Seb Oliver at the University of Sussex and indicates that early galaxies were more bloated, contained more dust and were distributed over larger regions than previously thought.

Around a thousand galaxies were studied, chosen because they are very distant and forming stars at very high rates. Because they are so distant, the galaxies are seen as they were when the Universe was much younger, with those studied here spanning a range of cosmic times between one and ten 10 billion years ago – a significant portion of the Universe's fourteen billion-year history.

Most of these galaxies are seen when the Universe was about half its current age, a period during which galaxies tended to be much more "active" than those we see around us today, with some forming stars hundreds or even thousands of times faster than our Milky Way.

Although rare, such "starburst galaxies" have produced as much energy over the course of cosmic history as all the other galaxies combined. This makes them crucial for studying the history of star formation in the Universe.

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