In sociology and biology it is now accepted that the environmental conditions affect the behaviour, development, and evolution of organisms. A research published online in the Wednesday 21st January 2026 issue of the prestigious journal Nature Communications demonstrates that the same holds also for stars. A group of scientists led by Prof. Ferraro of the Physics and Astronomy Depariment "Augusto Righi" of the Bologna University (Italy) discovered that the environment sets which stars can survive and evolve, therefore solving a 70-year long debateabout the origin of a mistrious class of stars named blue straggler stars.
The environment changes lives:
this is true for stars too!
The study presents one of the clearest and most direct pieces of evidence of how the environment can modify the evolution of stars, consisting in a great example of what we may call “stellar ecology”.
The result has been obtained from the study of a peculiar and mysterious class of stars that are called “Blue Stragglers”. They have been discovered in 1953 as anomalously massive stars that shine brighter than their sisters in their host stellar clusters, as if they were much younger. Their origin has been the subject of intense debate: direct collisions between stars, or evolution of binary systems?
Scientists involved in the research:
University of Bologna: Francesco R. Ferraro, Barbara Lanzoni, Cristina Pallanca, Mario Cadelano,
INAF-OAS: Emanuele Dalessandro
INAF-PD: Domenico Nardiello, Mattia Libralato
Indiana University (USA): Enrico Vesperini
European Souhern Observatory (Germania): Giacomo Beccari
University of Padova: Giampaolo Piotto
Illustration of the two formation processes for blue straggler stars: stellar collisions and evolution of binary systems.
Credit: ESA/Hubble, M. Kornmesser
Images of the two globular clusters at the extremes of the density range covered by the analyzed sample: NGC 5466, the least dense, on the left, NGC 6681, lthe densest cluster, on the right.
Credit: ESA/Hubble
The emerging picture is clear: the environment sets which stars can survive and evolve, and Blue Stragglers are witnesses of this process.
This work finally puts an end to a decades-long controversy on the origin these enigmatic stars. Moreover, it strengthens a more general and deeper concept: the same phenomena that regulate life on Earth —adaptation, interaction, environment —are at work also in the faraway world of stars. A further demonstration that the Universe, although vast and remote, is not that different from us.
Illustration of how the fraction of Blue Stragglers (top) and that of binaries (bottom) measured in the 48 analyzed globular clusters decrease for increasing central density of the system.
The findings astonished the researchers themselves. At odds with any prediction, the fraction of Blue Stragglers does not increase with environmental density — as expected if they were generated by collisions — but it gets smaller. Blue Stragglers are more numerous in less crowded environments, were stellar crashes are more unlikely, indicating that these are the ideal habitat for the formation and survival of these stars.
Even more important is the evidence that the same trend is observed for the fraction of binary systems. This indicates that the environment controls the survival of binaries: gravitational interactions in high-density clusters tend to destroy binaries, while they can survive and evolve peacefully in less crowded conditions. Blue Stragglers therefore appear as the natural outcome of the ev olution of binary systems that are able to survive long enough.
For any additional information please contact
Francesco Ferraro
email: francesco.ferraro3@unibo.it
tel: +390512095774
mobile: +393666357560
