A team of British scientists has created the deepest image of the Universe in the far infrared range, combining 141 separate images in each of the three colour channels: blue, green and red. This has allowed them to discover a previously invisible new class of dim galaxies. If such “hidden” galaxies are widespread, this could explain a number of as yet unsolved mysteries of the Universe.
The dark patch of sky was found to be full of galaxies. Image Credit: Chris Pearson
All the information was taken from the archive of the Herschel space observatory, which the European Space Agency operated from 2009 to 2013. The deep image of the Universe was created based on calibration images from the observatory’s SPIRE camera. About once a month, the camera was directed at the same area of the sky, where it was believed there was almost nothing, to check its sensitivity. As a result, over the four years of the observatory’s operation, 141 images were taken in the blue (250 µm), green (350 µm) and red (500 µm) channels. It is impossible to repeat the experiment, so the main discoveries may still be ahead.
The combined image reveals 2,000 previously invisible distant galaxies and galaxy groups in this location. They are arranged in a virtually continuous carpet, merging with the background in the case of the faintest objects. The discovery of so many of this new class of faint galaxies is the key to a clearer understanding of the evolution of stars, galaxies, and the Universe. For example, astronomers today cannot explain the excess of infrared light in the Universe: much more energy is registered than luminous objects are observed. The presence of deeply hidden galaxies can explain this mystery.
To create a more complete picture of the universe, new observations are obviously needed, and in particular, a new generation of space telescopes for the far infrared range. One such project is being considered by NASA – this is the PRIMA observatory, costing about $ 1 billion with a mirror diameter of 1.8 m. However, the project has not yet been approved and may give way to some other, more popular program or instrument.