Stephen Gillam presents at 29th General Assembly Of the International Astronomical Union

Stephen Gillam, assistant professor of physics, presented a poster session at the the 29th General Assembly Of the International Astronomical Union in Honolulu, Hawaii, on August 10-15 with a poster titled “The Spatial Distribution of the Red Giants in the Galactic Globular Cluster NGC2419.”

The poster presented the results of a study of the way giant stars are distributed in the distant Milky Way globular stars cluster NGC2419.  It is known that NGC2149 contains two separate groups of red giants. There is a large group of red giants that look like (that is to say they have the same colors and luminosities as) the old population of red giants in the outer reaches of the Milky Way. The second group shines with a slightly bluer light. These are clearly concentrated near the center of the cluster and the redder ones are more spread out. The common explanation for this is that the bluer group are a second generation of stars formed from gas polluted with the elements  (Carbon, Nitrogen, Oxygen, Neon, Sodium, Magnesium, Aluminum, Iron) made in supernova explosions in the first generation. The tell-tales of this process can be seen in the second generation stars in the light they emit at the blue and ultraviolet end of the visible spectrum. I separated the red giants into two groups using their colors and luminosities at the red end of the visible spectrum where there are no tell-tales of the supernova pollution process. The two generations should be indistinguishable there. I still saw the that the bluer giants were more centrally located than the redder giants. It appears that this cannot be due to the pollution process. This result indicates that the bluer stars are not a second generation of stars made from the debris of some first generation stars. A new explanation of the two groups is required for NGC2419.

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