Located some 13 million light-years from Earth, NGC 4214 is currently
forming clusters of new stars from its interstellar gas and dust. In
this Hubble image, we can see a sequence of steps in the formation and
evolution of stars and star clusters. The picture was created from
exposures taken in several color filters with Hubble's Wide Field
Planetary Camera 2. NGC 4214 contains a multitude of faint stars
covering most of the frame, but the picture is dominated by filigreed
clouds of glowing gas surrounding bright stellar clusters. The youngest
of these star clusters are located at the lower right of the picture,
where they appear as about half a dozen bright clumps of glowing gas.
Young, hot stars have a whitish to bluish color in the Hubble image,
because of their high surface temperatures, ranging from 10,000 up to
about 50,000 degrees Celsius. The radiation and wind forces from the
young stars literally blow bubbles in the gas. Over millions of years,
the bubbles increase in size as the stars inside them grow older. Moving
to the lower left from the youngest clusters, we find an older star
cluster, around which a gas bubble has inflated to the point that there
is an obvious cavity around the central cluster. The most spectacular
feature in the Hubble picture lies near the center of NGC 4214. This
object is a cluster of hundreds of massive blue stars, each of them more
than 10,000 times brighter than our own Sun. A vast heart-shaped bubble,
inflated by the combined stellar winds and radiation pressure, surrounds
the cluster. The expansion of the bubble is augmented as the most
massive stars in the center reach the ends of their lives and explode as
supernovae. The principal astronomers are: John MacKenty, Jesus
Maiz-Apellaniz (Space Telescope Science Institute), Colin Norman (Johns
Hopkins University), Nolan Walborn (Space Telescope Science Institute),
Richard Burg (Johns Hopkins University), Richard Griffiths (Carnegie
Mellon University), and Rosemary Wyse (Johns Hopkins University).
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