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White Dwarf Stars in Open Cluster NGC 6791
In studying the dimmest burned-out stars in globular star cluster NGC 6791, NASA's Hubble Space Telescope has uncovered a paradox: three different populations of stars exist in an object where all the stars should have formed at the same time out of an interstellar cloud of gas and dust.
[Left] – This is a ground-based telescopic view of NGC 6791, located 13,300 light-years away in the constellation Lyra. The green inset box shows the view with Hubble's Advanced Camera for Surveys.
[Top right] – The full Hubble Advanced Camera for Surveys field is full of stars estimated to be 8 billion years old. Two background galaxies can be seen at upper left.
[Bottom right] – A blow up of view of a small region of the Advanced Camera for Surveys field reveals very faint white dwarfs. The blue circles identify hotter dwarfs that are 4 billion years old. The red circles identify cooler dwarfs that are 6 billion years old.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.19h 20m 52.99s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.37° 46' 18.0"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Lyra
- DistanceDistanceThe physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs.13,300 light-years or 4 kiloparsecs
About the Data
- Data DescriptionData DescriptionProposal: A description of the observations, their scientific justification, and the links to the data available in the science archive.
Science Team: The astronomers who planned the observations and analyzed the data. "PI" refers to the Principal Investigator.HST Proposal: 9815 I. King (University of Washington), J. Anderson (STScI), G. Piotto (University of Padova), and L. Bedin (STScI); and 10471: I. King (University of Washington), J. Anderson (STScI), G. Piotto (University of Padova), L. Bedin (STScI), S. Cassisi (Collurania Astronomical Observatory, Italy), and M. Salaris (Liverpool John Moores University). - InstrumentInstrumentThe science instrument used to produce the data.DSS (left), HST>ACS/WFC (right)
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.July 2003, July 2005, Exposure Time: 6 hours (HST images, right)
- FiltersFiltersThe camera filters that were used in the science observations.HST: F606W (V) and F814W (I)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.NGC 6791 (DSS image, left) White Dwarf stars in NGC 6791 (bottom right)
- Object DescriptionObject DescriptionThe type of astronomical object.Open Cluster
- Release DateJuly 10, 2008
- Science ReleaseWhat’s My Age? Mystery Star Cluster Has 3 Different Birthdays
- Credit
The HST images (right) are a composite of several separate exposures made by the ACS instrument on the Hubble Space Telescope. Two filters were used to sample broad wavelength ranges in the visible and near infrafed. The color results from assigning different hues (colors) to each monochromatic image. In this case, the assigned colors are: Cyan: F606W (V) Orange: F814W (I)
Related Images & Videos
Zooming into an Open Star Cluster Yields Unexpected Results
This movie takes a closer loook at Hubble's image of NGC 6791, one of the oldest and largest open clusters known. The detection of white dwarfs that vary in age leads astronomers to rethink the theory that stars found in these clusters develop at the same time from large clouds...
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
