Cluster ’ s Advanced Age is in Razor-sharp Focus
Researchers using the Gemini Multi-conjugate adaptive optics System ( GeMS ), combined with the Gemini South Adaptive Optics Imager ( GSAOI ), probed the depths of the highly compact globular cluster 6624 ( Figure 3 ). These data reveal pinpoint star images with a uniformity across the crowded field , allowing the team to perform precise photometry deep into the cluster ’ s crowded core .
The team also detected a clear “ main-sequence knee ” ( Figure 3 , inset ); this distinctive bend in the evolutionary track of low mass main-sequence stars is extremely difficult to detect without ultra-precise photometry . Indeed , this is the first time the feature has been identified in this globular cluster , and it allowed the team to determine the cluster ’ s age with extremely high precision : about 11.5- 12.5 billion years .
January 2017
According to first author Sara Saracino of the University of Bologna , this is the most accurate , and deepest , near-infrared color-magnitude diagram ever produced of NGC 6624 and perhaps the best ever made for any bulge cluster . The results of this research are accepted for publication in The Astrophysical Journal , and a preprint is available here .
Monitoring Io ’ s Volcanoes with Adaptive Optics
The longest frequent , high-resolution imaging of Io ’ s thermal emission is providing insights on the Jovian moon ’ s volcanoes , thanks to a joint program between the Gemini North telescope ( with the Near InfraRed Imager and spectrometer [+ Altair adaptive optics instrument pairing ) and the W . M . Keck Observatory . Gemini ’ s queue scheduling provided the additional flexibility necessary to assure adequate coverage in the time domain .
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Figure 3 . Gemini Observatory GeMS image of globular cluster NGC 6624 revealing individual stars clear to its core . The inset shows the color-magnitude diagram with the mainsequence knee visible . The extreme sharpness of this adaptive optics image allows researchers to perform very precise photometry on individual stars — a task requiring exquisite imaging across the entire field , which would be a challenge for most adaptive optics systems . Composite color image by Travis Rector , University of Alaska Anchorage . Image credit : Gemini Observatory / AURA