Brightest galaxy and first-generation stars

Astronomers using the Very Large Telescope of the European Southern Observatory (ESO) have discovered by far the brightest galaxy yet found in the early universe. They also say they have strong evidence that this galaxy contains some of the first generation of stars. Astronomers have been seeking these stars, which would have been massive, brilliant and the creators of the first heavy elements in history — the elements necessary to forge the stars around us today, the planets that orbit them, our human bodies and all the material things we see around us.

ESO said in a statement on June 16, 2015:

Astronomers have long theorised the existence of a first generation of stars — known as Population III stars — that were born out of the primordial material from the Big Bang. All the heavier chemical elements — such as oxygen, nitrogen, carbon and iron, which are essential to life — were forged in the bellies of stars. This means that the first stars must have formed out of the only elements to exist prior to stars: hydrogen, helium and trace amounts of lithium.

These Population III stars would have been enormous — several hundred or even a thousand times more massive than the Sun — blazing hot, and transient — exploding as supernovae after only about two million years. But until now the search for physical proof of their existence had been inconclusive.

A team led by David Sobral, from the Institute of Astrophysics and Space Sciences, the Faculty of Sciences of the University of Lisbon in Portugal, and Leiden Observatory in the Netherlands, has now used ESO’s Very Large Telescope (VLT) to peer back into the ancient Universe, to a period known as reionisation, approximately 800 million years after the Big Bang. Instead of conducting a narrow and deep study of a small area of the sky, they broadened their scope to produce the widest survey of very distant galaxies ever attempted.

Their expansive study was made using the VLT with help from the W. M. Keck Observatory and the Subaru Telescope as well as the NASA/ESA Hubble Space Telescope. The team discovered — and confirmed — a number of surprisingly bright very young galaxies. One of these, labelled CR7, was an exceptionally rare object, by far the brightest galaxy ever observed at this stage in the universe. With the discovery of CR7 and other bright galaxies, the study was already a success, but further inspection provided additional exciting news.

The X-shooter and SINFONI instruments on the VLT found strong ionised helium emission in CR7 but — crucially and surprisingly — no sign of any heavier elements in a bright pocket in the galaxy. This meant the team had discovered the first good evidence for clusters of Population III stars that had ionised gas within a galaxy in the early universe.

Read more about this study from ESO

Some additional cool facts about this galaxy and its stars, from ESO:

– The galaxy’s name CR7 stands for COSMOS Redshift 7 and indicates its place in terms of cosmic time. The higher the redshift, the more distant the galaxy and the further back in the history of the universe it is seen. CR7 is located in the COSMOS field, an intensely studied patch of sky in the constellation of Sextans (The Sextant). The nickname was inspired by the great Portuguese footballer, Cristiano Ronaldo, who is known as CR7.

– The name Population III arose because astronomers had already classed the stars of the Milky Way as Population I (stars like the sun, rich in heavier elements and forming the disc) and Population II (older stars, with a low heavy-element content, and found in the Milky Way bulge and halo, and globular star clusters).

– CR7 is three times brighter than the previous titleholder, Himiko, which was thought to be one of a kind at this very early time. Dusty galaxies, at much later stages in the history of the Universe, may radiate more total energy than CR7 in the form of infrared radiation from warm dust. The energy coming from CR7 is mostly ultraviolet/visible light.

Bottom line: Astronomers have announced a newly discovered galaxy, labelled CR7. It’s the most distant galaxy known yet and may contain some of the first stars.

Via ESO

Enjoying EarthSky so far? Sign up for our free daily newsletter today!