These three reasons are why there’s no getting around the fact that astronomy needs the James Webb Space Telescope.
Even the most powerful telescope in history, the Hubble Space Telescope, can’t do it all.
The most distant discovered galaxies are all Hubble’s, but it’s unlikely to go farther.
By observing dark, empty patches of sky, it reveals ancient galaxies without nearby interference.
When distant galaxy clusters are present, these massive gravitational clumps behave as natural magnifying lenses.
The most distant observed galaxies have their light bent, distorted, and amplified along the journey.
Hubble discovered the current cosmic record-holder, GN-z11, via lensing.
Its light arrives from 407 million years after the Big Bang: 3% of the Universe’s current age.
Three reasons combine to limit Hubble’s potential beyond this.
1.) Despite its reflective outsides, Hubble resides in low-Earth orbit, with no active cooling.
Its instruments are therefore warm; it cannot observe mid-infrared light.
2.) More distant galaxies have their light redshifted by cosmic expansion.
Hubble’s wavelength limit, 1700 nanometers, corresponds to 326 million years after the Big Bang.
3.) But the Universe is filled with light-blocking gas until it’s 550 million years old.
Finding GN-z11 was serendipitous; it resides along a very rare, clear line-of-sight.
Only James Webb, with its distant orbit — and cooled, optimized instruments — will take us farther.
Mostly Mute Monday tells the astronomical story of an object, image, or phenomenon in visuals and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.