Image released by Nasa today  was  taken by  Hubble space telescope covering a portion of the southern field of the Great Observatories Origins Deep Survey. Among other data, scientists used the galaxies visible in the survey  to recalculate the total number of galaxies in the observable universe. Photograph: Nasa/EPA

How many galaxies are there in the night sky? A lot more than we realised - 20 times more in fact, leading astronomers to predict there are about 2 tr(...)