Using images from NASA’s Wide-field Infrared Survey Explorer (WISE), Dr. Denilso Camargo of the Colégio Militar de Porto Alegre, Brazil, has discovered five new globular clusters in the Milky Way’s Galactic bulge.
Globular clusters are systems of very ancient stars, held together by their mutual gravitational attraction in a spherical shape a few hundred light-years across.
They contain hundreds of thousands or perhaps a million stars. The large mass in the rich stellar center of a cluster pulls the stars inward to form a ball of stars. The word globulus, from which these clusters take their name, is Latin for small sphere.
It is thought that every galaxy has a population of globular clusters. Some, like the Milky Way, have a few hundred, while elliptical galaxies can have several thousand.
“Globular clusters were the first stellar systems formed in the early Universe and are often considered to be living fossils of galaxy formation. Thus, they have become a powerful tool for improving our understanding of the Milky Way formation and early evolution,” Dr. Camargo said.
“They also provide a means for tracing the Galaxy’s properties at the present time, for example, the bulge structure and kinematics.”
The newly-discovered globular clusters — named Camargo 1102, 1103, 1104, 1105, and 1106 — are very old, with ages in the range of 12.5-13.5 billion years.
All these clusters lie within the Milky Way’s bulge of stars, a spherical structure roughly 10,000 light years across in the center of our Galaxy.
Camargo 1102 is located over the Milky Way’s bar on the far side of the Galaxy’s center at a distance from the Sun of 26,700 light-years, at 2,800 light-years from the center, and have a vertical distance of 2,700 light-years.
The other clusters are located in the near side of the Galaxy, with distances from the Sun in the range of 14,700-18,900 light-years and within 6,800-11,700 light-years from the Milky Way center, but closer to the Galactic plane.
“The Galactic bulge formation and evolution is one of the most important unsolved problems in the present epoch and, thus, remains the subject of intense debate,” Dr. Camargo said.
“Therefore, the discovery of new globular clusters in the bulge, as well as deriving accurate parameters for known ones, are essential for improving our knowledge of the inner Milky Way history as well as characterizing its current evolutionary stage.”
A paper reporting this discovery is published in the Astrophysical Journal Letters.
Denilso Camargo. 2018. Five New Globular Clusters Discovered in the Galactic Bulge. ApJL 860, L27; doi: 10.3847/2041-8213/aacc68