Press Release
Cl0939+47 (Abell 851)
January 28, 1999
Row Res. (160 KB) High Res. (1.5MB) |
Object Name: Cl0939+47 (Abell 851)
Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO (J, K'), Suprime-Cam (R) Filter: R (red), J (1.25 micron), K' (2.15 micron) Color: Blue (R), Green (J), Red (K') Date: UT 1999 Jan 13 (R), Jan 14 (J), Jan 12 (K') Exposure: 3600 sec (R), 2400 sec (J), 2400 sec (K') Field of View: 120 arcsec by 145 arcsec Orientation: North up, east left Position: RA (J2000.0)=09h43m, DEC (J2000.0)=+46d59m |
Explanation:
Galaxies are not evenly distributed throughout the Universe,
but tend to reside in structures ranging from groups of
a few galaxies to massive clusters containing thousands
of galaxies. This image of the distant cluster Abell 851,
located five billion light years away from us, is about
two million light years across. While the nearest sizable
galaxy to our own, M 31 in Andromeda, is about two million
light years away with mostly empty space in between, the
same volume of space in Abell 851 is filled with many galaxies
with a wide range of colors and sizes. Almost every object
in this image is a galaxy, with there being only a few stars
from our own Milky Way. All galaxy clusters contain bright,
red elliptical galaxies, but distant clusters such as this
also possess fainter blue galaxies, which are not seen in
nearby ones. Both types are clearly visible in this color
image, formed from optical and infrared images taken with
Subaru' s Suprime-Cam and CISCO cameras. The depth and excellent
quality of this image reveal a wealth of information never
before seen from the ground.
By studying clusters of galaxies, astronomers hope to understand how individual galaxies form and evolve, as well as the history of the clusters themselves. Theoretical models predict that if the Universe contains enough material to stop its present expansion, then most clusters should have formed very recently. On the other hand, large numbers of distant, old clusters would imply that gravity is insufficient to overcome this expansion.