ARC-funded researchers using the Hubble Space Telescope have discovered that nearby reddish galaxies have been ‘pretending’ to be much more distant than they really are, and were distorting astronomical calculations of galaxy populations in the early universe.

Ultra-bright galaxies in the early universe are now likely to be less common than initially thought, the team at The University of Melbourne node of the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions has found.

The researchers used Hubble to observe two galaxies thought to be so distant that we see them more than 13 billion years back in time when the universe was young. The new observations showed that the brightest known galaxy candidate in the early universe turned out to be much closer to us after all—with profound implications for models of how galaxies formed when the universe was in its infancy.

The good news is that these observations strengthened the evidence that the other bright galaxy in the same image is truly an object in the infancy of the universe. This implies that while not quite as common as previously thought, galaxies containing billions of stars were already present at such early times. These sources will be characterized in greater detail by next-generation telescopes that Australian astronomers will use, such as the James Webb Space Telescope and the Giant Magellan Telescope.

Random patches of sky viewed through Hubble’s Wide Field Camera more than 100 times built a rich dataset that covers unrelated parts of the universe.

Image: Galaxies located in the Pisces constellation, which covers an area about 170 times smaller than that of the full moon.
Credit: R Livermore (The University of Melbourne), M Trenti (The University of Melbourne), and the BoRG team. Based on data taken with the NASA/ESA Hubble Space Telescope.