Six Italian stars shed light on early Black Hole evolution

Scientists have found evidence that supermassive black holes in the early universe grew intermittently in the first billion years after the Big Bang. Credits: X-ray: NASA/CXC/Univ. of Rome/E.Pezzulli et al. Illustration: NASA/CXC/M.Weiss

Six female Italian scientists have recently accomplished stunning results in the framework of one of the most challenging topics in modern Astrophysics. Five of these outstanding scientists have no fixed, tenure-track contract; three have not yet turned 30.

Their study of black holes dating back to the primordial phases of the Universe was published in April in the Monthly Notices of the Royal Astronomical Society. The names of the six astrophysicists: Edwige Pezzulli (first author of the paper), Rosa Valiante, Maria Orofino, Raffaella Schneider, Simona Gallerani and Tullia Sbarrato.

The topic addressed by the all-female team is Supermassive Black Holes, which are found in the centers of almost all known galaxies and whose masses are hundreds of thousands, even billions, of times greater than the Sun. In order to reach such an awesome mass, those early-Universe black holes would need to “ingest” a great amount of material, and would also need the time to consume it all. That’s why astrophysicists have been trying hard to come up with an explanation of how the early universe, about one billion years after the Big Bang, already featured supermassive black holes.

As we all know, the Big Bang took place approximately 13.8 billion years ago, and according to data gathered by the Sloan Digital Sky Survey (SDSS), supermassive black holes with one billion solar masses existed as far back in time as 12.8 billion years ago. When they are ingesting and accreting matter, black holes produce a large amount of heat and electromagnetic radiation, including X-ray emissions which can be detected by the Chandra X-ray Observatory. The latter is a telescope that was launched in 1999 and was specially designed to detect X-ray emission from very hot regions of the Universe such as exploded stars, clusters of galaxies, and matter around black holes.

According to the all-female team’s recently published model, these black holes were “light” and only about 100 solar masses when they were born, and most likely represented the relics of the earliest massive stars. These early black holes experienced “sudden” bursts of intense feeding activity, which caused them to add bulk and grow millions of times in mass in a relatively short amount of time.

In order to know if they are ultimately correct, the six scientists will need to look at larger areas of the sky, by means of X-rays, to verify if they can spot the early, fast-accreting black holes that their models have predicted.

Federico Pasquaré Mariotto (Associate Professor of Science Communication, Insubria University, Varese, Italy)