Our Milky Way Galaxy may be as much as two billion years older than currently thought, the principal investigator of a unique multi-year project to simulate the galaxy’s origin and evolution, told me here in Santiago. In fact, our own 10-billion-year-old Milky Way may contain ancient stars that predate the galaxy and that are as old as the cosmos itself.
A collaboration between Argentina, Chile and Spain called CIELO: Chemo-dynamical Properties of Galaxies and the Cosmic Web (“cielo” is “sky” in Spanish), the team’s research predates the covid pandemic and will continue for at least another five years.
Without doubt Chile is the world’s capital for optical astronomy —- with international telescopes and observatories throughout the country’s arid northern tier. But despite Chile’s bounty of telescopes, its reputation as a center for theoretical astrophysics still lags.
Yet two Argentine-born mathematicians turned astrophysicists —- Patricia Tissera and Susana Pedrosa —- are trying to change all that in an international partnership that uses numerical simulations to create a virtual universe composed of binary code; literally zeros and ones.
CIELO is a project that aims to create a virtual universe to study how galaxies form, and particularly how our Milky Way formed, Patricia Tissera, the CIELO principal investigator, and an astrophysicist at the Pontificia Universidad Catolica de Chile, told me during a sit-down interview in Santiago.
Each simulation’s millions of particles are numbers that represent a volume of mass.
The results of these numerical experiments are then compared with observations, Susana Pedrosa, a CIELO team member, and research astrophysicist at CONICET-UBA, told me at her office in Buenos Aires.
This enables us to refine our models, identify and incorporate missing physical processes, and make predictions that can be tested against observations, she says.
How Does It Work?
We take the velocities, the mass distribution, the temperature, the chemical elements in the stars, and in the gas surrounding the stars and compare those with observations, says Tissera. From this comparison, we learn if we have assumed the correct hypotheses or if they need to be modified, she says.
This is a game that never ends, says Tissera.
During the galaxy’s beginnings, gas and dust from the early cosmos streamed into our Milky Way’s dark matter halo, a hypothetical gravitationally bound region surrounding the galaxy. This halo, in turn, attracted enough gas and dust to begin forming our Milky Way’s earliest molecular clumps which eventually turned into stars.
It’s All About Cosmic Feedback
When supernova explosions occur, a significant amount of energy and chemical elements is released back into the interstellar medium, altering its chemical and thermodynamic properties, says pedrosa. This is crucial for regulating star formation, she says.
How Unique Is Our Milky Way?
It is a common galaxy, but it’s rare in the sense that it didn’t have a massive merger in the last in the last several billion years, says Tissera.
Three billion years after the big bang, the morphology of our Milky Way was pretty well fixed.
Neither Tissera nor Pedrosa think that our Milky Way is a major outlier in the realm of spiral galaxies. But its chemical develop is such that it’s obvious that we have benefited from billions of years of chemical enrichment. Our earth contains a plethora of iron and rare earth metals that were created through stellar nucleosynthesis during billions of years of supernovae enrichment.
It all gives pause to wonder if there is an astrobiological vector in our cosmic evolution. It’s hard to believe that we are the only intelligent species to have benefited from such chemical enrichment over cosmic time. In the end, it’s likely that sheer physics, chemistry and ultimately, biology would win out.
We are lucky to live on a planet that has all the chemical elements needed for life as we know it, says Tissera. This is a very distinctive place in our galaxy, so we should take care of this planet, she says.
