Hubble Sees Anemic Spiral NGC 4921
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 above 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.
Image Credit: Hubble Legacy Archive, ESA,
NASA
Guillermo Gonzalo Sánchez Achutegui
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