Proto globular cluster
Thanks to the powerful radio telescope ALMA, astronomers observed what could be the first proto globular cluster ever discovered. A giant molecular cloud extremely dense and massive, scrambled by the collision of galaxies Antennas, but that has not turned any star.
Credit: K. Johnson, U.Va.; ALMA (NRAO/ESO/NAOJ)
Globular clusters – groups spheroidal twinkling of stars, including up to one million participants who form attractive – are among the oldest objects in the universe. Although they are in abundance in and around many galaxies, scientists still do not know how effectively these gatherings are called gravity, or what are the conditions necessary for the creation of new globular clusters.
A team of astronomers using the telescope Atacama Large Millimeter / submillimeter Array (ALMA) in Chile has now discovered what may be the first known example of a globular cluster about to develop: a cloud of molecular gas incredibly heavy, extremely dense, but completely devoid of stars.
Credit: NASA/ESA Hubble
“We may be witnessing one of the oldest and extreme modes of star formation in the universe,” said Kelsey Johnson, an astronomer at the University of Virginia and lead author of a study being published in the Astrophysical Journal. “This remarkable object seems to come directly from the universe as primordial discover something that has all the characteristics of a globular cluster, but has not yet begun to form stars, is like finding a dinosaur egg that is about to unfold.”
This object, which astronomers call jokingly Firecracker (the “firecracker”), is located about 50 million light-years away from Earth, huddled between a famous pair of interacting galaxies known as the Antennae. Tidal forces, generated by the fusion process going on between these galaxies, triggering star formation at full blast; formation that occurs largely within dense clusters.
Credit: NASA, The Hubble Heritage Team, STScI, AURA
What makes the Firecracker unique, it is its extraordinary ground, the relatively small size and the apparent lack of stars. All other globular clusters similar that astronomers have observed to date are already populated with stars. The heat and the radiation emanating from these stars have significantly altered the environment, making it difficult to rebuild it as it should appear in his cooler and quiet early. With ALMA, astronomers were able to study in detail and find a pristine example of such a stellar incubator, making it an idea of the conditions that may have led to the formation of many, if not all, of the globular clusters.
“Until now, these potential clouds were seen only in their adolescence, when the proliferation star had already begun. To understand how it forms a globular cluster, however, it is necessary to be able to see his children, “summed up Johnson.
Most globular clusters were formed during a real “baby boom” occurred about 12 billion years ago. It was the era when galaxies were forming, packing up thickly up to a million stars of “second generation”, i.e. those stars with extremely low concentrations of heavy metals, indicating their early inclusion in the cosmic stage.
In the Milky Way are at least 150 known globular clusters, although there may be many more. Throughout the universe they are still being formed star clusters of various sizes. According to scientists, it is possible, although more and more unlikely, that larger and denser than they become in time of globular clusters.
“For a strong cluster of young stars, the probability of remaining intact is very low: about one percent. Various external and internal forces tend to break these objects, both forming open clusters like the Pleiades, which disintegrate completely in order to become part of the galactic halo, “explained Johnson.
The authors of the new study believe, however, that the object observed with ALMA, containing 50 million times the mass of the Sun in molecular gas is sufficiently dense to have a good chance of becoming one of the lucky ones.
Credit: EFE / Ariel Marinkovic
Globular clusters are evolving very quickly from their embryonic stage without stars, in less than a million years. This means that the object discovered by ALMA is going through a very particular of his life, giving astronomers a unique opportunity to study an important component of the early universe.
In exploring the Antennae galaxies, Johnson and his colleagues observed weak emission due to the molecules of carbon monoxide, which has allowed them to see and determine the characteristics of individual clouds of dust and gas. The total lack of heat emission – the signal detector gas heated by nearby stars – confirms that this newly discovered object is still in its original state.
The data of ALMA also indicate that the cloud Firecracker is subjected to extreme pressure, about 10,000 times greater than the typical pressures interstellar. This evidence provides support to previous theories that the formation of globular clusters requires high pressures.
According to the researchers, further studies with ALMA can reveal examples of proto-super star clusters in the Antennae galaxies and other interacting galaxies, shedding light on the origins of these ancient objects and their role in galactic evolution.