Stars have different masses and colors, some live billions and billions of years, others are gone in a cosmic blink. No matter their differences they all start their lives in stellar nurseries, gigantic clouds of hydrogen and various other elements and molecules. But a new study reveals that not all molecular clouds are the same.
As reported in Nature Astronomy, molecular clouds in distant galaxies sport significant differences compared to what we have observed in galaxies in the local universe. A distant galaxy known as the “Cosmic Snake,” located around 8 billion light-years away, could potentially be a Milky Way progenitor and its stellar nurseries have a mass, density, and turbulence 10 to 100 times higher than those in the nearby non-interactive galaxy.
A typical molecular cloud in the Milky Way produces slightly more than 100 stars, but in star clusters in the younger universe, it appears that value is 100 times higher. Astronomers suspect this much higher number of stars produced has to do with the conditions in those galaxies. Far-off galaxies have more hostile extreme conditions, where only the denser clouds survive. They are also apparently more efficient, with 30 percent of the mass converted into stars, compared to just 5 percent in the local universe.
“Such values had only been measured in clouds hosted in nearby interacting galaxies, which have interstellar medium conditions resembling those of distant galaxies,” lead author Miroslava Dessauges, from the University of Geneva, said in a statement. “A molecular cloud typically found in a nearby galaxy would instantly collapse and be destroyed in the interstellar medium of distant galaxies, hence its enhanced density and turbulence guarantee its survival and equilibrium.”
“The characteristic mass of the molecular clouds in the Cosmic Snake appears to be in perfect agreement with the predictions of our scenario of fragmentation of turbulent galactic disks," added Lucio Mayer, a professor at the Centre for Physical and Cosmological Theory at the University of Zurich. "As a result, this scenario can be put forward as the mechanism of formation of massive molecular clouds in distant galaxies.”
The observations were possible thanks to the Atacama Large Millimeter/submillimeter Array (ALMA) and the use of a gravitational lens. The Cosmic Snake is a gravitationally lensed galaxy whose light is coming to us from 8 billion light-years away. Between us and that galaxy, there is the dense cluster MACSJ1206.2-0847, which has warped space-time to such a degree to magnify the galaxy.
“Gravitational lenses are a natural telescope that produces a magnifying-glass effect when a massive object is aligned between the observer and the distant object,” explained Dessauges. “With this effect, some parts of distant galaxies are stretched on the sky and can be studied at an unrivaled resolution of 90 light-years.”
The team is now planning further investigations of other distant galaxies to see how typical these values are and what has changed in the nearby molecular clouds (or galaxy in general) for the values to drop so much.