Starbursts in dwarf galaxies played a bigger role than expected in the early Universe, according to new data from the Wide Field Camera 3 (WFC3), onboard NASA’s Hubble Space Telescope.

Although galaxies across the Universe are still forming new stars, the majority of the stars were formed between 6 and 2 billion years after the Big Bang.

Studying this early epoch is a key in order to fully understand how these stars formed, and how galaxies have grown and evolved since.

New Hubble data have allowed astronomers to take a step forward in understanding this crucial epoch by peering at a sample of starburst dwarf galaxies.

These galaxies form stars at a furiously fast rate, far above the ‘normal’ star formation rate expected of galaxies.

“We already suspected that dwarf starbursting galaxies would contribute to the early wave of star formation, but this is the first time we’ve been able to measure the effect they actually had. They appear to have had a surprisingly significant role to play during the epoch where the Universe formed most of its stars,” said Dr Hakim Atek, an astronomer with the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and the first author of a paper published in the Astrophysical Journal (arXiv.org pre-print).

“These galaxies are forming stars so quickly that they could actually double their entire mass of stars in only 150 million years – this sort of gain in stellar mass would take most normal galaxies 1-3 billion years,” said study co-author Dr Jean-Paul Kneib, also of EPFL.

This finding contributes to a decade-long investigation to understand the links between galaxies’ mass and their star-forming activity, and helps paint a consistent picture of events in the early Universe.

As well as adding new insight into how and where the stars in our Universe formed, this finding will certainly help to unravel the secrets of galactic evolution.

It is unusual to find a galaxy in a state of starburst, implying that they are the result of some strange incident, such as a merger, a tidal interaction with another galaxy, or the shockwave from a supernova.

By studying these galaxies more closely and understanding how they formed and behaved in their earliest years, astronomers hope to discover the cause of these violent bursts and learn more about galactic evolution throughout the Universe.

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Hakim Atek et al. Hubble Space Telescope Grism Spectroscopy of Extreme Starbursts across Cosmic Time: The Role of Dwarf Galaxies in the Star Formation History of the Universe. ApJ 789, 96; doi: 10.1088/0004-637X/789/2/96