Compared to a backyard view,
the Hubble Space Telescope observes
a minuscule portion of the sky.
In 2003,
astronomers selected one particular field
for intense study.
Hubble observed this relatively empty region
for over 11 days of combined exposure.
The Ultra Deep Field represents
the deepest visible light image of the universe.
Of the 10,000 objects in this image,
only a few hundred are stars
and the rest are galaxies.
The larger galaxies often have the familiar
spiral and elliptical shapes.
Smaller galaxies can have irregular
and distorted structures.
Some tiny galaxies are mere
distant dots of light.
A two-dimensional image can show the sizes,
shapes, and colors of galaxies.
Detailed analysis can also reveal
the distances to these galaxies.
Their distances stretch out into space
for more than 10 billion light-years.
This three dimensional data set
enables astronomers to examine galaxies
across the cosmos.
Galaxies are distributed across
billions of light-years of space.
Hence, their light has traveled
for billions of years to reach us.
We see these galaxies not as they are today,
but as they were billions of years ago.
Looking farther out into space
is also looking farther back in time.
This galaxy is one of the most
distant ever observed.
Seen as it was
more than 12 billion years ago,
only the core of this galaxy has formed.
Smaller galaxies often merge together
to build up larger galaxies.
When galactic disks form and settle,
spiral structure can begin to emerge.
A fully formed spiral galaxy
takes many billions of years to develop.
Deep fields allow astronomers to study
the development of galaxies over cosmic time.
The Ultra Deep Field examines
about 10,000 galaxies
within a tiny patch of sky.
There are more than 10 million patches
of this size across the entire sky.
As a result,
one can estimate that there are more than
100 billion galaxies in the universe.
A deep field samples galaxies
across space and time.
Deep fields are crucial for studying
the distribution, characteristics, and development of galaxies.