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.
Credits
Hubble images: NASA and H. Richer (University of British Columbia);Ground-based image: NOAO/AURA/NSF
| About The Object | |
|---|---|
| Object Name | M4, NGC 6121 |
| Object Description | Globular Cluster |
| R.A. Position | 16h 23m 35.41s |
| Dec. Position | -26° 31' 31.9" |
| Constellation | Scorpius |
| Distance | M4 is roughly 5,600 light-years from the Earth. |
| About The Data | |
| Data Description | 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) |
| Instrument | WIYN/KPNO>0.9m (top), HST>WFPC2 (bottom-left), and WFPC2 and HST>STIS/MULTIACCUM (bottom-right) |
| Exposure Dates | March 1995 (KPNO), February - March 1995 (WFPC2), and January - April 2001 (STIS) |
| Filters | F336W (B), F555W (V), F814W (I) |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The 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. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
