Using images from NASA’s Wide-field Infrared Survey Explorer (WISE) satellite, Brazilian astronomer Denilso Camargo has found five new globular clusters in the bulge of our Milky Way galaxy.
Dubbed Camargo 1102, 1103, 1104, 1105, and 1106, these newfound, tightly-packed systems of hundreds of thousands of stars are almost as old as the universe itself, as just announced in a paper published in The Astrophysical Journal Letters. They lie in the so-called bulge of the galaxy, the central component of the Milky Way that extends out some 12,000 light years from the galactic center.
Camargo was able to glean additional information on the clusters by also using data from the 2MASS ground-based infrared survey and the European Space Agency’s (ESA) most recent data drop from its Gaia satellite.
“Globular clusters were the first stellar systems formed in the early universe and are often considered living fossils of galaxy formation,” Camargo, the paper’s lead author, and an astronomer at the Brazilian Ministry of Defense’s Military College in Porto Alegre, told me. Thus, he says, they have become a powerful tool in improving our understanding of the Milky Way’s formation and early evolution.
Such clusters of stars also provide a means for tracing the galaxy’s current dynamics.
As for what’s most significant about the discovery of these five globular clusters?
Arguably, their scarcity. Within the Milky Way, there are less than 200 known , says Camargo.
As for their location?
Of these newly discovered clusters, Camargo 1102 seems to be located on the far side of the Milky Way, some 3000 light years above the galactic plane. The other four, says Camargo, lie even closer to the mid-plane (or equator) of the Milky Way. But he says deeper observations using photometry — the measurement of these clusters’ intrinsic brightness and intensity — are needed to determine their structural properties.
If future observations are able to tease out more information on their structure, the hope is that these clusters can be used to at begin retracing the formation history of the galactic bulge. But that’s a big if.
How the galactic bulge formed and evolved remains one of astrophysics’ most important unsolved problems.
Thus, Camargo says they are essential for improving our knowledge of the inner Milky Way’s history as well as for characterizing the inner galaxy’s current stage of evolution.
Camargo expects that there are many more globular clusters in the Milky Way that simply haven’t yet been detected. But over the last decade or more advanced infrared telescopes are piercing through the dust and gas at the galactic center to reveal the densest innermost part of our Milky Way.
They are part of the bulge and, thus, this may suggest that the bulge was there in the earliest phases of the galaxy’s formation, says Camargo. But he notes that, alternatively, these clusters may have formed in a dwarf galaxy that the Milky Way simply cannibalized much earlier in its history.