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Hubble Pinpoints White Dwarfs in Globular Cluster
Peering deep inside a cluster of several hundred thousand stars, NASA's Hubble Space Telescope uncovered the oldest burned-out stars in our Milky Way Galaxy. Located in the globular cluster M4, these small, dying stars - called white dwarfs - are giving astronomers a fresh reading on one of the biggest questions in astronomy: How old is the universe? The ancient white dwarfs in M4 are about 12 to 13 billion years old. After accounting for the time it took the cluster to form after the big bang, astronomers found that the age of the white dwarfs agrees with previous estimates for the universe's age.
In the top panel, a ground-based observatory snapped a panoramic view of the entire cluster, which contains several hundred thousand stars within a volume of 10 to 30 light-years across. The Kitt Peak National Observatory's 0.9-meter telescope took this picture in March 1995. The box at left indicates the region observed by the Hubble telescope.
The Hubble telescope studied a small region of the cluster. A section of that region is seen in the picture at bottom left.
A sampling of an even smaller region is shown at bottom right. This region is only about one light-year across. In this smaller region, Hubble pinpointed a number of faint white dwarfs. The blue circles pinpoint the dwarfs. It took nearly eight days of exposure time over a 67-day period to find these extremely faint stars.
Globular clusters are among the oldest clusters of stars in the universe. The faintest and coolest white dwarfs within globular clusters can yield a globular cluster's age. Earlier Hubble observations showed that the first stars formed less than 1 billion years after the universe's birth in the big bang. So, finding the oldest stars puts astronomers within arm's reach of the universe's age.
M4 is 5,600 light-years away in the constellation Scorpius.
Hubble's Wide Field and Planetary Camera 2 made the observations from January through April 2001. These optical observations were combined to create the above images. Spectral data were also taken.
About the Object
- R.A. PositionR.A. PositionRight ascension – analogous to longitude – is one component of an object's position.16h 23m 35.41s
- Dec. PositionDec. PositionDeclination – analogous to latitude – is one component of an object's position.-26° 31' 31.9"
- ConstellationConstellationOne of 88 recognized regions of the celestial sphere in which the object appears.Scorpius
- 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.M4 is roughly 5,600 light-years from the Earth.
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.WFPC2 data Principal Astronomers: H. Richer (UBC), D. Vandenberg (U.Victoria), P. Stetson (DAO), M. Bolte (UCSC/Lick Obs.), C. Pryor (Rutgers U.), R. Mcclure (DAO), J. Hesser (DAO), G. Fahlman (CFHT), H. Bond (STScI), R. Bell (U. Maryland) STIS data Principal Astronomers: H. Richer (U. British Columbia), G. Fahlman (CFHT), B. Gibson (U. Colorado), B. Hansen (Princeton U.), R. Ibata (ESO), M. Limongi (Osservatorio Astronomico di Roma), M. Rich (UCLA), M. Shara (AMNH), P. Stetson (DAO) - InstrumentInstrumentThe science instrument used to produce the data.WIYN/KPNO>0.9m (top), HST>WFPC2 (bottom-left), and WFPC2 and HST>STIS/MULTIACCUM (bottom-right)
- Exposure DatesExposure DatesThe date(s) that the telescope made its observations and the total exposure time.March 1995 (KPNO), February - March 1995 (WFPC2), and January - April 2001 (STIS)
- FiltersFiltersThe camera filters that were used in the science observations.F336W (B), F555W (V), F814W (I)
- Object NameObject NameA name or catalog number that astronomers use to identify an astronomical object.M4, NGC 6121
- Object DescriptionObject DescriptionThe type of astronomical object.Globular Cluster
- Release DateApril 24, 2002
- Science ReleaseHubble Uncovers Oldest “Clocks” in Space to Read Age of Universe
- Credits
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Claire Andreoli
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
claire.andreoli@nasa.gov
