They’re so far that
the light arriving on Earth today set out from the galaxies billions
of years ago. We see the galaxies not as they are today, but as
they looked long before there was life on Earth.
Some galaxies are so far away that they
appear as tiny smudges, even through the largest telescopes.
It’s tough to determine
how large or bright these fuzzy distant galaxies are. But astronomers
can figure out the distance to these galaxies, by watching for
incredibly bright exploding stars called supernovae.
Some types of supernovae have a known brightness
- or “wattage” - so
we can figure out how far they are, and therefore the distance
to their home galaxy.
1986. Astronomers begin to use supernovae to find the distance
to the furthest galaxies we can see.
ABOVE: The deeper we see into space, the more galaxies we discover.
Only a few points of light in this image come from stars in our
own Milky Way; everything else is a distant galaxy.