The
Whirlpool galaxy has been one of the most photogenic galaxies in amateur
and professional astronomy. This galaxy, also called M51 or NGC 5194, is
having a close encounter with a nearby companion galaxy, NGC 5195. The
companion's gravitational pull is triggering star formation in the main
galaxy, as seen in brilliant detail by numerous, luminous clusters of
young and energetic stars. The bright clusters are highlighted in red
by glowing hydrogen gas, which is associated with the most luminous
young stars in the spiral arms.. Along the spiral arms, dust
"spurs" are seen branching out almost perpendi- cular to the main
spiral arms. The regularity and large number of these features suggests to
astronomers that previous models of "two-arm" spiral galaxies
may need to be revisited. The new images also reveal a dust disk in the
nucleus, which may provide fuel for a nuclear black hole.
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Through
an extraordinary chance alignment, the Hubble telescope has captured a
view of a face-on spiral galaxy lying precisely in front of another larger
spiral. The unique pair is called NGC 3314. This line-up provides
astronomers with the rare chance to see the dark material within the
foreground galaxy, seen only because it is silhouetted against the light
from the object behind it. The bright blue stars forming a pinwheel shape
near the center of the front galaxy have formed recently from interstellar
gas and dust. However, in the fore- ground galaxy, NGC 3314a, there are
numerous additional dark dust lanes that are not associated with any
bright young stars. A small, red patch near the center of the image is the
bright nucleus of the background galaxy, NGC 3314b; its light is reddened
by passing through a space containing interstellar dust particles of the
front galaxy.
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