In the first moments after the Big Bang, the universe was extremely hot and dense. As the universe cooled, conditions became just right to give rise to the building blocks of matter – the quarks and electrons of which we are all made. Present observations also suggest that the first stars formed from clouds of gas around 150–200 million years after the Big Bang and that heavier atoms such as carbon, oxygen and iron, have since been continuously produced in the hearts of stars and strewn throughout the universe in spectacular stellar explosions called supernovae.

Intriguing questions arise. Do we have the means to detect baby galaxies as far back as 200 million years after the Big Bang? How do these baby galaxies look like? Are they brightly lit by stars, or have the stars burned out by supernovae and what’s left is essentially dark matter, the mysterious stuff that makes up about 26% of the universe, and which does not emit light or electromagnetic radiation of any kind?

Science is not ready to provide answers to galaxies as early as that, but we are edging closer. In a series of images captured by the powerful James Webb Space Telescope (JWST) just last year, a faint smudge of a galaxy was spotted which got scientists the world over palpably excited. This galaxy, nicknamed JADES-GS-z14-0 is at present, the earliest galaxy known to science. According to calculations, it lies at the record redshift of z = 14.3, which translates to a formation date of about 290 million years after the Big Bang. As the universe is about 13.8 billion years old, JADES-GS-z14-0 is indeed a “young” galaxy, the earliest mankind has ever seen. Hence the excitement.

Here are two images (one zoomed in) of this remarkably young galaxy

Measuring Redshifts

How did scientists arrive at the formation date of 290 million years for JADES-GS-z14-0? The answer lies in redshifts, a measure of how the wavelength of light gets stretched towards the red part of the spectrum. More precisely, the more distant an object is from the Earth, the more it will be redshifted. As light travels great distances and is redshifted, its wavelength may be shifted by a factor of 10. GS-z14-0 was discovered to have a redshift of 14.3, besting the 2022 record of a galaxy found with a redshift of 13.2 that corresponded to a formation age of about 325 million years after the Big Bang. The story may not end with GS-z14-0 as science continues to push the limits of cosmological time.  

Surprises, Surprises

Meanwhile, scientists are amazed by the size and luminosity of JADES-GS-z14-0. This baby galaxy spans some 1600 light-years across and is pouring out huge amounts of starlight (see chart below).

It is known that many of the most luminous galaxies generate their light mostly via gas falling into a supermassive black hole. But this is not the case for JADES-GS-z14-0. Instead, researchers believe that light in this galaxy is being produced by an abundance of young stars. This abundance in turn implies that JADES-GS-z14-0 is several hundreds of millions of times the mass of the Sun (!) which raises a puzzling question: how did nature make such a bright, massive galaxy in less than 300 million years?