The greatest advances in science often come when we first probe new frontiers.
When we peered into the abyss of space more deeply than ever, we revealed thousands of distant galaxies.
To view them, three obstacles must be overcome: their faintness, their apparent redness, and the intervening neutral matter.
The most distant galaxies appear very red, because their emitted light’s wavelength gets stretched by expanding space.
We overcome this by looking at longer, infrared wavelengths of light.
The great distances leave them faint, so we must rely on Einstein’s natural magnifying glass to expose them.
Foreground galaxies, and large galaxy clusters, act as a gravitational lens, revealing these most distant galaxies.
Finally, beyond a certain distance, the Universe hasn’t formed enough stars to reionize space and make it 100% transparent.
We only perceive galaxies in a few serendipitous directions, where copious star-formation occurred.
In 2016, we fortuitously discovered GN-z11 at a redshift of 11.1: from 13.4 billion years ago.
But recent, indirect evidence suggests stars formed at even greater redshifts and earlier times.
We must go farther into the infrared than Hubble’s capabilities allow.
That requires the James Webb Space Telescope.
First galaxies, prepare yourselves. We’ll see you in 2020.