A Look at NGC 3370 in Detail
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The center of NGC 3370
shows well delineated dust lanes and an uncommonly
ill-defined nucleus. 65kB 55kB Two regions
on the edge of the galaxy show bright blue
clusters of young, massive stars as well as
distant, red background galaxies shining through.
48kB An unusual concentration in the upper
corner shows a complex region of tidal interaction
between a bright galaxy and its companion.
Superimposed are a foreground star in the
Milky Way and a background galaxy. 45kB A
Sombrero-galaxy-look-alike is seen edge on
with a small warp in the middle right. 48kB
In the lower middle right, a distant filament
of merging blue galaxies can be seen.
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Click on Images for
Larger View
Credit:
NASA and A. Riess (STScI)
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To Catch a (Rising and) Falling
Star!
Supernova in NGC 3370
SN 1994ae was discovered by S. Van
Dyk and the Leuschner Observatory Supernova Search
(IAU Circular 6105) using an automated 0.76-meter
telescope. The discovery image was taken on Nov.
14, 1994. The supernova was located about 30".3
west and 6".1 north of the galaxy's nucleus. The
image on the left is from the 1.2-meter telescope
at the Fred Lawrence Whipple Observatory (courtesy
R. Schild/CfA) and was obtained in good conditions
a few weeks after maximum light. The supernova peaked
at ~13th magnitude in the visual.
Credit: NASA and A. Riess
(STScI) |
Extensive monitoring of the light
curve in 5 colors was obtained beginning 2 weeks
before maximum and provides one of the most complete
photometric records of a supernova light curve (Riess
et al. 1999). The image on the right is from HST
9 years later, by which time the supernova can no
longer be detected. Many interesting features of
the host as well as other background galaxies are
blurred beyond recognition by the atmosphere in
the ground-based image. HST, which sits above the
distorting atmosphere, captures great detail at
exquisite resolution.
Cepheid Variables in NGC 3370
 Supernovae,
such as SN 1994ae, can be used to calibrate
distance measurements in the universe,
because other, fainter stars of known
brightness can be observed in the same
galaxy. These stellar "standard candles"
are the Cepheid variable stars, which
vary regularly in brightness with periods
that are directly related to their intrinsic
brightness, and thus allow the distance
to the galaxy--and the supernova--to
be determined directly. However, only
the Hubble Space Telescope, equipped
with its new Advanced Camera for Surveys,
has the capability to resolve these
individual Cepheids in NGC 3370.
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Above we see a "movie" of 12 consecutive
epochs of a long period (~50 days) Cepheid
variable. The Cepheid is in the center
of a crowded region of stars. The resolution
of HST is required to pick out the variable
star from its neighbors. The star was
caught initially fading before suddenly
doubling in brightness, then declining
again to its faintest point over 4-5
weeks. By plotting the change in brightness
(magnitude) over time (days) we can
see how the cepheid intensity rises
and falls. At right is a "light
curve" of the brightness over time
for one of the cepheid variables in
NGC 3370. Peak-to-trough variation,
or from its faintest to its brightest,
represents a doubling in brightness.
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Click on Images
for Larger View
Credit:
NASA and A. Riess (STScI)
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