An international team of astronomers (composed also of some Polish scientists) running the VIPERS (VIMOS Public Extragalactic Redshift Survey) project has just presented the largest 3D map of the Universe as it was 7 billion years ago, and made available the data, on which the map was based.

VIPERS is the largest in history survey of galaxies at least 5 billion light years away of us. VIMOS multi-spectrograph mounted on one of the four 8.2-metres Very Large Telescopes operated in Chile by European South Observatory (ESO) was acquiring data for nearly 8 years. Operating one of the largest telescopes on Earth for almost 500 hours, astronomers have determined distances to more than 90,000 galaxies and have learned their properties. The acquired data helped to chart the first so detailed 3D map of that region of our Universe, which is from 5 to 9 billion light years away us. To day we are looking at objects as they were when the Universe was twice younger than now.

ESO telescopes were never involved in a galaxy survey bigger than VIPERS. The acquired information has helped scientists to understand how different type galaxies and their star populations were and are evolving. Information on distribution of galaxies helps to sheds some light on the large-scale Universe framework composed of the dark matter, and on nature of the dark energy which makes the Universe to expand at ever growing velocity.

According to the standard cosmological model, our Universe was born some 13.7 billion years ago and initially expanded at ever decreasing velocity. The tendency reversed about 7 billion years ago – explains Professor Agnieszka Pollo (Jagiellonian University and Head of NCBJ Astrophysics Division) – Currently the Universe is expanding ever faster. It is speculated that the so-called dark energy is responsible for the acceleration. Nature of the dark energy is still unknown. The largest in history of astronomy survey of galaxies from that distant epoch may facilitate solving one of the key mysteries of the contemporary physics, even if the question of the dark energy will remain unresolved in spite of very detailed analysis of the acquired data.

Scientists from Poland involved in the project included Professor Agnieszka Pollo (Jagiellonian University in Cracow and NCBJ), Dr.Katarzyna Małek and Dr.Aleksandra Solarz (NCBJ), Dr.Janusz Krywult (the Jan Kochanowski University in Kielce), MSc Małgorzata Siudek (Polish Academy of Sciences Theoretical Physic Centre). Some students/PhD students from Jagiellonian University also participated. Polish team members have in particular studied spectral lines in light emitted by the surveyed galaxies. The results have proved that the distinction between the two main types of galaxies observed to-day (spiral galaxies, in which new stars are still created, and inactive elliptical galaxies composed of old stars) was existing already when the Universe was twice younger than now. Besides, they adopted some self learning algorithms to sort out the observed galaxies into various types – a very useful tool during large scale surveys of the skies.

The VIPERS-produced map of the Universe shows compact large structures with collections of red (i.e. old) galaxies. Blue (active) galaxies dominate in some less crowded regions, just like in the to-day Universe almost 14 billion years old. It looks like all basic galaxy types were shaped already in much younger Universe. Scientists hope that further analyses of the VIPERS-acquired data will bring other breakthrough results.