Anemic Spiral NGC 4921
from Hubble
From NASA’s Astronomy
Picture of the Day
How far away is spiral
galaxy NGC 4921? Although presently estimated to be about 310 million light years distant, a more precise determination
could be coupled with its known recession speed to help humanity better calibrate
the expansion rate of the entire visible universe.
Toward this goal, several images were taken by the Hubble Space Telescope in order to help identify key stellar
distance markers known as Cepheid variable stars.
Since NGC 4921 is a member of the Coma Cluster of Galaxies, refining its distance would also allow a
better distance determination to one of the largest nearby clusters in
the local universe.
The magnificent
spiral NGC 4921 has been informally dubbed anemic because of its low rate of star formation and low surface brightness.
Visible in the image are, from the center, a bright nucleus, a bright central bar, a prominent ring of dark dust, blue clusters of recently formed stars, several smaller companion galaxies, unrelated galaxies in the far distant
universe, and unrelated stars in
our Milky Way Galaxy.
