Peering through the Hubble Telescope to our distant past

Peering through the Hubble Telescope to our distant past

Artist's impression of the current oldest known galaxy, GN-z11 • Image by Pablo Carlos Budassi (CC BY-SA 4.0)

Originally published 3 May 1999

A few weeks ago [in 1999], astronomers using the Hub­ble Space Tele­scope said they dis­cov­ered the most dis­tant object yet observed in the uni­verse — a galaxy 13 bil­lion light-years from Earth.

Because the galaxy — dubbed “Sharon” after the sis­ter of one of its dis­cov­er­ers — is so far away, and because light takes time to trav­el the dis­tance between us, we see it as it exist­ed when the uni­verse was only 5 per­cent of its present age, not long after the first galax­ies and stars con­densed from the primeval gas.

Detec­tion of such galax­ies is a con­sid­er­able tech­ni­cal achieve­ment, not only because they are so faint and far away. Because dis­tant galax­ies share in the uni­verse’s expan­sion, their light is stretched into parts of the spec­trum that are absorbed by inter­stel­lar neb­u­lae that lie along our line of sight and by the Earth­’s atmos­phere. Only with a tele­scope above the atmos­phere is detec­tion pos­si­ble at all.

What do we learn from such far­away galaxies?

So far, not much. These galax­ies appear as mere dots of light, and lit­tle can be deduced about their struc­ture or composition.

But astronomers have the­o­ret­i­cal ideas about what these ear­ly galax­ies might be like.

For one thing, the­o­ries of the Big Bang sug­gest that only hydro­gen and heli­um atoms con­densed from the hot radi­a­tion of the Big Bang. No car­bon, no oxy­gen, no nitro­gen, no sil­i­con, no iron.

There­fore, the first galax­ies and stars were made of hydro­gen and heli­um exclu­sive­ly. The stars may have had plan­ets, but only big gassy plan­ets like Jupiter or Sat­urn. With­out heavy ele­ments there could have been no Earth-like plan­ets, no rocky moons, no asteroids.

And, of course, no car­bon based life.

In we could vis­it the Sharon Galaxy in the era in which we observe it, it would be a live­ly place, roil­ing with primeval ener­gy, explod­ing with the vio­lent deaths of hot mas­sive stars. But nowhere among the worlds of that galaxy would we find sperm, egg, wing, flower, feath­er. Not only were the ele­ments of life unavail­able, but not enough time had elapsed for com­plex life­forms to evolve.

The Sharon Galaxy pre­sum­ably still exists some­where in the uni­verse today, 13 bil­lion years old­er than it appears in the Hub­ble pho­to­graph. And what a dif­fer­ent sort of galaxy it must be now.

Count­less gen­er­a­tion of mas­sive stars have lived and died in the galaxy dur­ing the ensu­ing eons. As stars burn they fuse heavy ele­ments from hydro­gen and heli­um. When stars die explo­sive­ly they make still more heavy ele­ments and spew those atoms into the inter­stel­lar neb­u­lae out of which new gen­er­a­tions of stars will be born.

As time passed in the Sharon Galaxy, more and more heavy ele­ments enriched the primeval gas mix­ture, until the most recent stars pre­sum­ably con­tain a few per­cent of atoms like car­bon, oxy­gen, and iron, and shep­herd small plan­ets made of rock, met­al, water, and air.

Per­haps on one of those plan­ets intel­li­gent life has evolved and is look­ing our way. What would they see?

They would see our Milky Way Galaxy as a dot of light on the thresh­old of time, 13 bil­lion years in the past — a galaxy with­out Earth-like plan­ets, with­out life, with­out intel­li­gence. They would see our galaxy in its infan­cy, hot and live­ly, stew­ing up the atoms that will some­day com­pose the Sun, the Earth, the Hub­ble Space Tele­scope, and the bod­ies of the men and women who use the scope to explore cos­mic history.

In oth­er words, our galaxy would appear to Sha­ronites — if such exist — more or less as their galaxy appears to us.

Can we observe the Sharon Galaxy as it exists today?

Impos­si­ble. No con­ceiv­able infor­ma­tion can pass back and forth between us. We can see that oth­er galaxy in our space, but not in our time. We are sequestered in our present by the finite veloc­i­ty of light.

How­ev­er, we have rea­son to believe that the laws of nature are the same through­out the cos­mos. So, in a sense, that dot of light 13 bil­lion light-years away is “us” — or a galaxy very much like what our galaxy might have been like then.

The Hub­ble Space Tele­scope is humankind’s most effec­tive time machine, an instru­ment that lets us see into what Shake­speare’s Pros­pero calls “the dark back­ward and abyss of time.”

As a species we are infi­nite­ly curi­ous about our past, which is why we invest bil­lions of dol­lars in a mag­nif­i­cent instru­ment that orbits 350 miles above the Earth and peers deeply into time.

That dot of light observed by the Hub­ble at the begin­ning of mate­r­i­al cre­ation is a faint glimpse of the cos­mic forge in which our very atoms were created.


The cur­rent record hold­er for the old­est and most dis­tant­ly observed galaxy is GN-z11, dis­cov­ered in 2016. ‑Ed.

Share this Musing: