the explorers journal - The Explorers Club

would inevitably see not what is, but what once had
been. He may as well have been describing the reality
of the space-time continuum.
If this sounds confusing it might help to consider
the following dialectic. When we contemplate the
sprinkle of tiny orange and red glints spread liberally
across the Hubble Ultra Deep Field image
on page 46—an 11-day exposure constituting the
deepest look into space-time ever achieved in
visible light—we’re looking at the earliest known
galaxies. But while to us they may seem incomparably
ancient, in fact they’re about as young as
galaxies ever got. What we’re seeing is a real-time
transmission from time’s edge. It’s a live feed, not
a faded photograph. And their photons continue
to shower in from all sides, impossibly faint: the
light of other days, uncut after its multibillion-year
passage through the slow glass of the universe.
Why are the youngest, most distant galaxies
orange or red Because as their steady streams of
photons pipe across space-time, their wavelengths
shift due to the acceleration accompanying their
great extension. Galaxies visible at time’s horizon,
awash in the brilliant blue light of the giant, shortlived
stars accompanying their birth, appear to
change color with increasing distance—a phenomenon
known as red shift. Their light goes from blue
to white, white to yellow, yellow to orange, orange
to red, and finally from red to infrared. The most distant
can only be discerned in infrared wavelengths—
one reason why the upcoming James Webb Space
Telescope, a successor to the Hubble, will operate
exclusively in such frequencies. When even these
wavelengths go dark, it doesn’t necessarily mean
that no galaxies are there, only that they’re so far
away—and traveling so rapidly further due to the
inexorable expansion of the universe—that it’s no
longer possible to perceive them. Their piping has
descended in register, finally merging with the surrounding
rumble of space and time. They’re lost in
the craquelure of a very big picture.
H o r s e h e a d N e b u l a
The spectacular dark Horsehead Nebula, some 1,500 lightyears
away, is actually a projection of the dense Orion
Molecular Cloud. The gas and dust behind it is both illuminated
and ionized, blazing from the five-star system known as Sigma
Orionis, which causes the Horsehead to cast a shadow.Image
taken by the Canada-France-Hawaii Telescope (CFHT).
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