Hundreds of thousands of previously unknown galaxies have been revealed in a new map of the night sky published on Tuesday. /VCG Photo

A total of 200 astronomers from 18 countries are part of the international team behind the work. They found 300,000 previously unknown light sources by using radio astronomy to look at part of the sky over the northern hemisphere. /VCG Photo

Scientists said the discovery could help understand black holes and how clusters of galaxies evolve. /VCG Photo

Low-Frequency Array telescope, known as LOFAR which consists of an array of stations in the Netherlands and several other countries in Europe, was adopted to catch traces of radiation produced when galaxies merge. /VCG Photo

The map created by the LOFAR observations contains data equal to 10 million DVDs but only covers two percent of the sky. The team hopes to chart the whole northern sky and reveal 15 million undetected radio sources. /VCG Photo