What is 'Deep'? – The Universe Looks Different at Different Depths
Comparing distant galaxies in the Hubble Deep Fields with nearby galaxies can help scientists understand how galaxies formed and how their properties have changed over time. Small elliptical-shaped galaxies appear to be the most common type of galaxy in the present-day universe. The presence of many irregularly shaped objects in the Hubble Deep Fields may indicate that collisions between galaxies and episodes of rapid star formation, or "starbursts," were more common in the past.