Using the Hubble in conjunction with Keck Observatory in Hawaii, astronomers were able to study the galaxies as they existed 11 billion years ago, when the Universe was less than 3 billion years old.
“Seeing the compact sizes of these galaxies is a puzzle", said Pieter G. van Dokkum of Yale University in New Haven, Connecticut, USA, who led the study. "No massive galaxy at this distance has ever been observed to be so compact. These galaxies would have to change a lot over 11 billion years, growing five times bigger. They could get larger by colliding with other galaxies, but such collisions may not be the complete answer. It is not yet clear how they would build themselves up to become the large galaxies we see today.”
To determine the sizes of the galaxies, the team used the Near Infrared Camera and Multi-Object Spectrometer on Hubble. For the Keck observations, a powerful laser was used to correct for image blurring caused by the Earth's atmosphere. Only Hubble, Keck and ESO’s Very Large Telescope are really able to measure the sizes of these galaxies as they are very small and far away.