The galaxies were identified using redshift – the change in colour observed from a given point as an astronomical object moves away. The further away something is, the redder its observed light becomes.
The redshift observed for these two galaxies indicated that the light had been emitted by them a very long time ago. In fact, BoRG 0116+1425 630 was estimated to be the oldest bright young galaxy ever detected.
Astrophysicists Rachael Livermore and Michele Trenti and their colleagues from the BoRG team tested these findings by using follow-up imaging and measurements using Hubble Space Telescope with a filter that helps discriminate between low- and high- photometric redshift solutions for these galaxies.
Their results confirmed that BoRG 0116+1425 747 as a highly probable distant bright galaxy. However, they discovered that BoRG 0116+1425 630 is likely to be an “interloper”, relatively nearby and much younger than previously thought.
Livermore, who led the research says “Now that we have a better measurement of the colours, it looks as though the brightest galaxy is actually relatively nearby – we see it only nine billion years back in time, whereas it was previously thought to be 13 billion.”
The researchers say this discovery has profound implications for models of how galaxies formed when the Universe was in its infancy and that ultra-bright galaxies in the early Universe may be less common than scientists initially thought.