Fast Facts
Webb used the NIRCam instrument to study globular cluster NGC 6440 orbits within the bulge of the galaxy 28,000 light years away. Globular clusters include thousands to millions of older stars tightly bound together by gravity.
Main Sequence Bi-modality: Webb discovered a split in the main sequence of NGC 6440, suggesting the presence of two stellar populations with different helium and oxygen abundances.
Helium and Oxygen Variations:. In this globular cluster, some stars have more helium and less oxygen than others. These variations tell us about the history of the cluster and how its stars formed.
Implications for Astrophysics: This discovery opens up new questions for scientists. They want to understand why NGC 6440 has these two stellar populations. These findings also show how powerful JWST is in revealing detailed properties of star clusters, which were hard to study with older telescopes.
Paper: You can read the full study with this arxiv paper 2310.13056 (arxiv.org)
The Data: CMD
For those rusty or unsure what a CMD graph is: A Colour-Magnitude Diagram (CMD) is a graphical representation used in astronomy to plot the colour (temperature) of stars against their brightness (luminosity).
This wee diagram helps astronomers understand the properties and evolutionary stages of stars within a cluster.
It's similar to the Hertzsprung-Russell (H-R) diagram, which also plots stars' temperature against their luminosity but often uses spectral types or absolute magnitudes.
The left panel of the diagram
The long, snake-like shape of the data represents the stars in NGC 6440.
The y-axis shows the brightness (luminosity) of the stars. Brighter stars are lower on the y-axis, and dimmer stars are higher up.
The x-axis shows the colour (temperature) of the stars. Cooler stars, which appear redder, are on the right, while hotter stars, which appear bluer, are on the left.
Right panels of the diagram
Shows the motion of stars to separate those that belong to the cluster from unrelated stars in the background.
The red circles and dots mark the stars confirmed to be part of NGC 6440.
Thanks to these findings, JWST has advanced our understanding of globular clusters. By observing variations in helium and oxygen abundances based solely on photometric observations, we can explore the formation and evolution of multiple stellar populations in globular clusters in new ways. In particular, this study shows the JWST's ability to overcome observational challenges, such as severe extinction and crowding, that have hindered similar studies in the past.
Based on the successful identification of multiple populations within NGC 6440, similar studies can be carried out on other globular clusters, particularly those in the Galactic bulge, providing valuable information on the formation history of these clusters as well as the early Milky Way's environment.
Future research can build on these findings by:
Similar deep observations of other globular clusters are needed to map out multiple populations and their properties.
More detailed theoretical models are needed to understand the implications of variations in helium and oxygen abundance.
Exploring the relationship between cluster mass, age, and the extent of multiple populations to gain a more complete understanding of globular cluster formation and evolution. And so this study illustrates the significant effects of JWST on astrophysical research.
All of this wonderful information comes from a very detailed and extremely complex Arxiv paper (2310.13056) that took me quite some time to digest. I will write another post to feature the other data. The excitement of accessing all the raw data from Webb is overwhelming, and the eagerness for more space science discoveries from Webb is immense.
Recommended Resources
>> Webb Science
>> Gateway to Astronaut Photography of Earth
>> HiRISE (High Resolution Imaging Science Experiment Mars Reconnaissance Orbiter)