Light that traveled over 13.4 billion years to reach our neighborhood in space has been confirmed to have come from the oldest and most distant galaxy ever detected.
This places the furthest of these four very young objects at the very dawn of the Universe, shortly after the Big Bang – a time when the Universe was still hazy and murky and the first rays of light were penetrating the darkness.
So detailed are the JWSTThrough long spectroscopic observations, researchers can not only measure the distance traveled by light from these galaxies, but also infer some of the properties of the galaxies.
“For the first time, we discovered galaxies only 350 million years after the Big Bang, and we can be absolutely sure of their fantastic distances”, says astronomer Brant Robertson from the University of California at Santa Cruz.
“Finding these first galaxies in images of such breathtaking beauty is a special experience.”
Being able to peer into the Universe earlier than ever before was one of the greatest hopes placed in the JWST. Our understanding of the first billion years after the Big Bang is extremely limited, and the discovery of increasingly older objects can help shed light on this crucial formative period.
We have models that describe how events unfolded. We believe that before the birth of the first stars, the Universe was filled with opaque matter; any light scattered by free electrons and could not flow freely.
These particles gradually combined to form neutral hydrogen; when the stars began to form, they ionized the hydrogen and the light shone. This process was completed about 1 billion years after the birth of the Universe.
The light from these objects is very weak, having traveled very far. And, due to the expansion of the Universe, it has been significantly stretched into the longer, redder end of the spectrum, a phenomenon known as redshift.
The JWST is the most powerful telescope ever launched into space, and it specializes in infrared and near-infrared light – designed to detect this red-shifted light, to the best of our ability.
To obtain a reliable redshift, light must be broken down into its constituent wavelengths, a technique known as spectroscopy. A team of researchers has broken down the light from JWST’s NIRCam into nine wavelength ranges, focusing on four galaxies with high redshifts, two of which were first identified by Hubble.
The new JWST data confirms that these two galaxies are indeed among the most distant ever detected – and the other two are even further away.
“It was crucial to prove that these galaxies indeed inhabit the early Universe. It is very possible that closer galaxies are masquerading as very distant galaxies,” he added. says astronomer Emma Curtis-Lake from the University of Hertfordshire in the UK.
“To see the spectrum revealed as we had hoped, confirming that these galaxies are at the edge of our field of view, some farther away than Hubble could see! This is an extremely exciting achievement for the mission.”
The two Hubble galaxies have redshifts of 10.38 and 11.58. The new JWST finds have redshifts of 12.63 and 13.20 – the latter being about 13.5 billion light-years away.
Other candidates for higher redshifts are currently under investigation, but have yet to be confirmed. Considering that JWST hasn’t even been operational for six months yet, it probably won’t be long before the record is broken.
But there is plenty to do in the meantime. The observations that gave us these distant galaxies as part of the JWST Advanced Deep Extragalactic Survey (JADES) collected a total of 28 hours of data from a region of space in and around the famous Hubble Ultra Deep Field.
This light will be able to tell us a lot about the conditions of the early Universe and about the formation of the first stars and galaxies.
“With these measurements, we can know the intrinsic luminosity of galaxies and determine how many stars they have,” Robertson says.
“Now we can start to really distinguish how galaxies are assembled over time.”
Researchers will present their findings at STScI First scientific results of the JWST conference. Both pre-printed documents can be read here and here.