A Blue Bridge of Stars between Cluster Galaxies
From NASA’s Astronomy Picture of the
Day
Why is there a blue
bridge of stars across the center of this galaxy cluster?
First and foremost the
cluster, designated SDSS
J1531+3414, contains many large yellow elliptical galaxies.
The cluster's center, as pictured
above by the Hubble Space Telescope, is surrounded by many unusual,
thin, and curving blue filaments that are actually galaxies far in the distance
whose images have become magnified and elongated by the gravitational
lens effect of the massive cluster.
More unusual, however,
is a squiggly blue
filament near the two large elliptical galaxies at
the cluster center. Close
inspection of the filament indicates that it is most likely a bridge
created by tidal effects between the two merging central elliptical galaxies rather
than a background galaxy with an image distorted by gravitational
lensing.
The knots in the bridge
are condensation
regions that glow blue from the light of massive young stars. The
central cluster region will likely undergo continued study as its uniqueness
makes it an interesting laboratory of star
formation.
Image Credit: NASA, ESA, G. Tremblay (ESO) et al.;
Acknowledgment: Hubble Heritage Team (STScI/AURA) - ESA/Hubble Collaboration
