Your task is to estimate how many galaxies
there are in the universe.
Introduction
The Hubble Ultra Deep Field is called a
"pencil beam" survey because the observations encompass a narrow, yet
"deep" piece of sky. Astronomers compare the Ultra Deep Field view to
looking through an eight-foot-long soda straw.
The images below left shows where in the
sky the Ultra Deep Field is. This patch
was chosen as it is largely empty and unobscured by nearby stars.
The image above right shows the area that
makes up the Ultra Deep Field, being the area outlined in red & blue. The area that would be the size of the moon,
viewed from Earth, is also shown. As you
can see from this image, the Ultra Deep Field's patch of sky is so tiny it
would fit inside the largest impact basin that makes up the face on the Moon.
Astronomers would need about 50 Ultra Deep Fields to cover the entire Moon.
They would need 12.7million Ultra Deep
Fields to cover the entire sky.
Why does the Ultra Deep Field look back
in time? Find out
here.