NGC 6791 Mystery Star Cluster has 3 different birthdays

NGC 6791 Mystery Star Cluster has 3 different birthdays
NGC 6791 Mystery Star Cluster has 3 different birthdays annotated
Object Type: 
Description: 

NGC 6791 Star Cluster stack about 3,5hrs (L 6x600" and 10x300" each RGB) calibrated and stacked and processed in Pixinsight and CS5. 

Full-Res Image

NGC 6791, NASA Astronomy Picture of the Day - 12 Jan 2000

Image Calibration 

Center (RA, Dec): (290.226, 37.769)
Center (RA, hms): 19h 20m 54.273s
Center (Dec, dms): +37° 46' 09.545"
Size: 26.6 x 24.7 arcmin
Radius: 0.302 deg
Pixel scale: 0.947 arcsec/pixel
Orientation: Up is -179 degrees E of N

 

NGC 6791

Distance ~13,300 ly (4078 pc)
Visual Brightness +9.5
Apparent Dimension 16'

 

NGC 6791 is an open star cluster in the Lyra constellation.It was discovered by Friedrich August Theodor Winnecke in 1853. At roughly 8 billion years old, and with an Iron to Hydrogen abundance ratio that is more than twice that of the Sun, it is one of the oldest and most metal-rich clusters in the Milky Way. This is contrary to the typical rule-of-thumb where older means more metal-poor. Compounded with the fact that it has an unusually high population of stars, NGC 6791 is among the most studied clusters in the sky.

Among the dimmest stars in the cluster are groups of white dwarfs that are 6 billion years old and another group that appear to be 4 billion years old. The ages are out of sync with those of the cluster's normal stars, which are 8 billion years old. This seeming contradiction in age for this cluster has been studied and a solution proposed with age of about 8 billion years.(source wikiwand)

..."Using NASA's Hubble Space Telescope to study the dimmest stars in the cluster, astronomers uncovered three different age groups. Two of the populations are burned-out stars called white dwarfs. One group of these low-wattage stellar remnants appears to be 6 billion years old, another appears to be 4 billion years old. The ages are out of sync with those of the cluster's normal stars, which are 8 billion years old."...  (credits NASA - click to read the complete article) 

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