The Cosmic Companion
May 8 · 3 min read

Galaxies in the early Universe were far brighter than astronomers predicted, new findings from the Spitzer Space Telescope reveal. Ancient galaxies are seen glowing in infrared light which left their source during the earliest age of galaxies and stars. Astronomers believe this finding could help answer an intriguing mystery from the earliest era of our Cosmos.

Following the Big Bang, the universe was filled with energy, but matter had not yet come into being. The first matter which came into being was in the form of ionized hydrogen and helium, and light began to fill the Cosmos. However, roughly 300,000 years after the Big Bang, this ionized gas became electrically neutral, and the Universe entered a era cosmologists refer to as “The Dark Ages.”

An artist’s conception of what an early galaxy may have looked like. Active star formation, combined with frequent star deaths would have illuminated the gas between stars, making the galaxy largely opaque, and leaving these bodies with little structure. Image credit: James Josephides (Swinburne Astronomy Productions)

In the Beginning…

The Epoch of Reionization began 500 million years after the Big Bang, at a time when quasars first began to take shape, and galaxies began to develop. Slowly, over another 500 million years, this reionization lit up the Universe, turning the Cosmos from a dark expanse to the brilliant place we know today. How reionization occurred, however, remains a mystery.

“It’s one of the biggest open questions in observational cosmology. We know it happened, but what caused it? These new findings could be a big clue,” said Stephane De Barros of the University of Geneva in Switzerland.

A composite image of a field of galaxies, taken by the Hubble and Spitzer space telescopes. The oldest, dimmest galaxies are circled. The inset image at the bottom right shows a closeup, long exposure image of one of these ancient families of stars. Image credit: NASA/JPL-Caltech/ESA/Spitzer/P. Oesch/S. De Barros/I.Labbe

The Spitzer Space Telescope was used to look back at the earliest galaxies in the Cosmos, 13 billion light years away from Earth. Examination of 135 galaxies found these ancient bodies, populated by young, massive stars,were surprisingly energetic in two frequencies of infrared light. These wavelengths were consistent with light produced by ionizing radiation interacting with hydrogen and oxygen within galaxies.

“We did not expect that Spitzer, with a mirror no larger than a Hula-Hoop, would be capable of seeing galaxies so close to the dawn of time. But nature is full of surprises,” said Michael Werner, Spitzer project scientist at NASA’s Jet Propulsion Laboratory.

A graphical representation of the history of the Universe. Image credit: S.G. Djorgovski et al./Digital Media Center, Caltech

To Lighten Up the Story…

Following the formation of matter, the only electromagnetic (em) radiation that could permeate the Universe were radio waves and visible light, while em radiation with shorter wavelengths — ultraviolet light, for example — was captured by hydrogen atoms. In the process, these atoms were stripped of their electrons, creating ions.

Evidence of this epoch of reionization is seen when astronomers look back to the earliest days of the Cosmos, while the source of the massive amount of energy required to power this change over the entire Universe remains unknown. Stars or galaxies may have been responsible, but the energy output of these bodies would have required these bodies to be much more powerful than they are today. One theory suggests quasars — galaxies with incredibly powerful supermassive black holes — may have produced the energy needed to ionize the matter of the Cosmos.

“The story so far:
In the beginning the Universe was created.
This has made a lot of people very angry and been widely regarded as a bad move.”

― Douglas Adams, The Restaurant at the End of the Universe

I Can See Clearly Now

A look at the James Webb Telescope, which may answer some of the deepest questions about the earliest eras of the Universe. Credit: NASA Goddard

“These results by Spitzer are certainly another step in solving the mystery of cosmic reionization. We now know that the physical conditions in these early galaxies were very different than in typical galaxies today. It will be the job of the James Webb Space Telescope to work out the detailed reasons why,” said Pascal Oesch of the University of Geneva.

The James Webb Space Telescope, which could answer many of the questions which remain of the earliest era of matter in the Universe, is scheduled to launch in 2021.

The Cosmic Companion

Written by

James Maynard is the author of two books, and thousands of articles about space and science. E-mail:

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