Hubble identifies White Dwarf Population in Globular Cluster M4

[Left] –

A view of globular cluster M4. The nearest globular cluster to

Earth (7,000 light-years away), and containing more than 100,000 stars,

M4 was the target of a Hubble Space Telescope search for white dwarf

stars. Ancient red giant stars are predominant in this view from a

ground-based telescope. The field is 47 light-years across. The box

(right of center) shows the small area that Hubble telescope probed.

Credit:

Kitt Peak National Observatory 0.9-meter telescope, National

Optical Astronomy Observatories; courtesy M. Bolte (University of

California, Santa Cruz)

[Right] –

A HST color image of a small portion of

the cluster only 0.63 light-years across reveals 8 white dwarf

stars (inside blue circles) among the cluster’s much brighter

population of yellow sun-like stars and cooler red dwarf stars. Hubble

reveals a total of 75 white dwarfs in one small area within M4, out of

the total of about 40,000 white dwarfs that the cluster is predicted to

contain. The Hubble results will allow astronomers to refine

theoretical predictions of the rate at which white dwarfs cool — an

important prerequisite for making reliable estimates for the age of the

universe and of our Milky Way galaxy, based on white dwarf

temperatures. The image was taken with the Wide Field and Planetary

Camera 2.

Credit: Harvey Richer (University of British Columbia,

Vancouver, Canada) and NASA

Last Modification: 9 May 1998, 17:30 MET