Explanation:
Similar in size and grand design to our
own
Milky Way, spiral galaxy NGC 3370 lies about 100 million
light-years away toward the constellation Leo.
Recorded
here
in exquisite detail by the Hubble Space Telescope's
Advanced Camera for Surveys,
the big, beautiful face-on spiral does steal the show,
but the sharp image also reveals an impressive array of
background galaxies in the field, strewn across
the more distant Universe.
Looking within NGC 3370,
the
image data has proved sharp enough
to study individual pulsating stars known as
Cepheids which
can be used to accurately determine this galaxy's distance.
NGC 3370 was chosen for this study because in 1994
the spiral galaxy was also home to a well studied stellar
explosion -- a type Ia supernova.
Combining the known distance to this
standard candle supernova,
based on the Cepheid measurements, with observations
of supernovae at even greater distances,
can reveal the size and expansion rate of the
Universe
itself.
