Last year, Brazilian astronomer Denilso Camargo made headlines with his incredible discovery of five ancient globular star clusters nestled in the center of the Milky Way, as reported by the Inquisitr at the time.
Since then, the laborious scientist, who is affiliated with the Brazilian Ministry of Defense’s Military College in Porto Alegre, has gone back to work to unravel more of our galaxy’s secrets. His efforts have paid off in a grand way, as the astronomer has just published another paper announcing the discovery of yet another three globular clusters in the heart of our galaxy.
Globular star clusters are among the oldest stellar formations in the universe. These spherical bundles of stars are extremely dense, crammed with thousands of ancient stars, and date back to the early days of the universe — taking shape a few hundred million years after the Big Bang.
So far, less than 200 globular clusters have been discovered in the Milky Way galaxy — the brightest and largest of which is Omega Centauri (pictured above), which spans 150 light-years across and is made up of nearly 10 million stars, per a previous report from the Inquisitr. By comparison, giant elliptical galaxies boast several thousands.
The newfound globular clusters, named Camargo 1107, 1108, and 1109, join the previously discovered group — Camargo 1102 through 1106 — thereby expanding the known number of ancient globular clusters in the Milky Way galaxy. This remarkable find is detailed in a study featured on January 21 in the Monthly Notices of the Royal Astronomical Society — Letters.
The three globular clusters were spotted after Carmargo and his colleague Dante Minniti, an astronomer at the Millennium Institute of Astrophysics (MAS) in Chile and the Vatican Observatory in Italy, combed through data from four different astronomical surveys.
The two astronomers examined data gathered by NASA’s Wide-field Infrared Survey Explorer (WISE) satellite, as well as a heap of observations from the Two Micron All-Sky Survey (2MASS) — an infrared survey of the entire sky. In addition, the scientists scoured data from the European Southern Observatory’s (ESO) VISTA Variables in the Via Lactea extended survey (VVVX) and from the European Space Agency’s Gaia satellite — particularly the second data release, made available in April of 2018.
After carefully analyzing the data, Camargo together with Minniti, who is the head of the ESO-VVVX survey, stumbled upon the three new globular clusters toward the central region of the Milky Way — also known as the galactic bulge. The newfound star clusters are very old and were forged sometime between 12 billion years and 13.5 billion years.
Located in the bulge area close to the mid-plane of the Milky Way galaxy, these ancient stellar formations are also very poor in metal. The same phenomenon occurs in many of the universe’s oldest stars, which have a remarkably low metal content, as previously reported by the Inquisitr.
Camargo describes globular clusters as “fossils of the primordial universe” and highlights that studying these ancient star formations could reveal key details about how our galaxy evolved.
“As relics of star formation in the early universe, globular clusters may provide important clues on the Milky Way history. For instance, the bulge formation and evolution remain poorly understood and globular clusters are powerful tools in tracing its structure, kinematics, and stellar content.”
According to the astronomer, globular clusters could help scientists “reconstitute the chain of physical processes experienced by the Milky Way,” from its moment of origin and all the way to its present form. These ancient star clusters have populated the Milky Way ever since its inception and, as Camargo puts it, they have “basically witnessed the entire history of our galaxy.”
Based on their age and low metallicity, the newfound globular clusters seem to be associated with the Milky Way’s inner halo, the two astronomers note in their paper. This “suggest[s] that the Milky Way’s central region hosts a subpopulation of very old and metal-poor globular clusters, which is consistent with being an inner halo component,” says Camargo.
Another possibility is that the three globular clusters are “part of an old classical bulge,” born out of a violent event — such as a collision with another galaxy or the sinking of giant clumps of gas — in the Milky Way’s distant past.
“These clusters may be the remnants of a primordial class of globular clusters that were destroyed mainly by dynamical processes and are the source of the ancient field stars that inhabit the Milky Way bulge and the inner halo.”
This hypothesis is backed up by past studies, which hint at a consistent number of globular clusters igniting into existence just after the Big Bang, around the time when the universe went through the period of reionization. As the Inquisitr previously reported, that was the time when the larger and brighter galaxies began to form, their light reheating the hydrogen that cooled off 400,000 years after the Big Bang and turning the universe back to ionized plasma.
The two astronomers estimate that there could be at least a few more dozens of globular clusters waiting to be discovered in the Milky Way’s galactic bulge.
“It seems that many faint globular clusters such as the present discoveries remain undetected until now due to the high extinction and stellar crowding towards the bulge,” Camargo and Minniti wrote in their paper.