Has JWST “Captured” the Oldest Galaxy in the Universe?

By Allen Isaac

July 24, 2022
glass z13 distant view
The galaxy Glass z13. Credits: JWST (source)

We’re pretty sure that everyone must have heard about the James Webb Space Telescope by now.

It is, after all, NASA’s most ambitious telescope venture by far and also could be pinned as the most anticipated one yet. 

The scientific community is elated by the fact that the James Webb Space Telescope has not let us down, and is very unlikely to do the same in the future.

Just within a month of being operational, it has already provided us with crucial astronomical data including some of the most (if not the most) mesmerizing and groundbreaking images across the far reaches of the cosmos.

Feel free to refer to the Deepest Images of the Universe Captured by JWST to know (in detail) about the first set of images shot by JWST.

Just days following the arrival of the first images captured by the telescope, JWST has much more in its lot for us already.

The James Webb Space Telescope may have just observed the oldest and most distant galaxy in the universe ever known as GLASS-z13, which existed just about 300 million years after the Big Bang.

Yes, we’re aware that the statement might sound a little ambiguous, but you need not worry.

Stick with us and you shall have your questions answered.

How Do We Observe Distant Galaxies & Other Celestial Bodies – Observational Astronomy

So, how can this be?

How could we have possibly traced a galaxy so far back in time? 

Well, it all works on the fact that light, which travels astonishingly fast, still has a finite speed of 299,792,458 meters per second

So, following Einstein’s Theory of General Relativity, that is the speed limit on the highway of the cosmos that no entity is allowed to trespass.


For instance, the light from our sun, traveling at the speed mentioned above, takes about 8 minutes to reach the earth. 

So if one day, the sun were to disappear into thin air, the pitch darkness that is to follow would be experienced by us only 8 minutes later.

We would also not feel the consequent gravitational effects on earth till 8 minutes, because not just light but everything (from information to gravitational waves) travels at the same speed as light; nothing travels faster.

The same can be applied to objects far away like the closest star to us.

It’s called Proxima Centauri, and it is 4.2 light years away from us, implying that it takes light 4.22 years to reach us once it has left the star. 

So when we observe the star, we’re seeing it as it was 4.2 years ago. 

The same rule applies to all other celestial bodies; this is how observational astronomy works.

Starlight is often too weak to be detected when such a large scale of distances is involved, so we turn to the gigantic galaxies.

Capturing the Farthest Galaxies in the Universe

With some of the most advanced machinery in our arsenal of space telescopes, we have been able to observe stars & galaxies at breathtaking distances. 


Let’s learn a bit about them before moving back to what the JWST did. 

Galaxy GN-z11

The current record holder of the highest redshift galaxy spectroscopically confirmed is GN-z11 at z ∼ 11 measured with detections of the Lyman break and rest-frame ultraviolet (UV) metal lines. Credits: By NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz) (link), Public Domain

All limits were shattered when the Hubble Space Telescope observed a galaxy called GN-z11, in March 2016 (read the original research paper here).

It was, then, the most distant galaxy to have ever been observed at a redshift of 10.95, seen as it was just 400 million years after the Big Bang.

The redshift gives us an idea of the age of our subject of observation.

What is Redshift?

Redshift is a phenomenon where a light wave (or even a sound wave) shifts to the red end of the spectrum as it stretches while moving ahead through space and time.

Fact: The ‘z’ in the names of galaxies like GN-z11 or GLASS-z13 is indicative of the redshift that the light from these galaxies has undergone before being captured by JWST. 

GN-z11 was observed to be 25 times more massive, and forming stars at a rate about 20 times greater, than our Milkyway Galaxy. 

From the data (of GN-z11) captured by Hubble, the emission lines (which are studied to estimate the redshift of the galaxy) could not be resolved by Hubble.

The emission lines were then studied and resolved using the Multi-Object Spectrograph for Infrared Exploration (MOSFIRE) – a spectrograph, at the Keck Observatory, that is used to study emission lines.

The data that came out of it was enough to propose that it was the most distant galaxy ever observed and in 2020, GN-z11 was announced as the official record holder.

Galaxy HD-1

Three-color image of HD1 – potential candidate for the most distant galaxy to date (13.5 billion light years), created using data from the VISTA telescope. The red object in the center of the zoom-in image is HD-1. Credits: Harikane et al., CC BY 4.0

Exceeding all expectations, GN-z11 was claimed to be dethroned quite recently when NASA observed a galaxy in April 2022, at a distance of about 13.5 billion light-years, called HD-1.

It was observed collectively by the Subaru Telescope, VISTA Telescope, UK Infrared Telescope, and Spitzer Space Telescope.

HD-1 is a super-bright galaxy, having a mass equivalent to as many as 10 billion suns.

There had been numerous interpretations regarding the nature of HD-1, such as the galaxy being home to Population III stars

Population III stars are extremely luminous and massive hypothetical stars composed entirely of primordial gases (like hydrogen and helium) and no metals.

Though, population III stars have not been directly observed as they were too old (and distant) and died shortly after. 

The theory of population III stars could account for the ultraviolet luminosity of HD-1.

Referring to the galaxy as “a giant baby in the delivery room of the early universe”, physicist Avi Loeb said, “It breaks the highest quasar redshift on record by almost a factor of two, a remarkable feat.”

However, the data on HD-1 is limited, as it is no piece of cake to form pinpoint conclusions when it comes to observational astronomy at such humongous distances; there is often room for uncertainty.

This ambiguity, which essentially was just our technological limitations, is what leads some people (including scientists) to say that even HD-1 is no crown holder when it comes to the most distant galaxy in the observable universe.

“Observational information on HD-1 is limited and other physical properties remain a mystery including its shape, total mass and metallicity. The difficulty is that this is almost the limit of the capabilities of current telescopes (Subaru, Vista, Spitzer, etc.) in terms of both sensitivity and wavelength.”

Yuichi Harikane, astrophysicist at University of Tokyo

GLASS-z13 and GLASS-z11 Observed by JWST

Zoomed image of the galaxy GLASS-z13. Credits: JWST

In a research paper published on 20th July 2022, a group of scientists claims that the James Webb Space Telescope has captured a galaxy named GLASS-z13, which existed when the universe was just about 300 to 330 million years old

Mind you, the universe is currently believed to be 13.77 billion years old.

It’s, thus, quite a groundbreaking discovery that we have peered so far into a cosmos so vast.


The galaxy was captured using JWST’s Near-Infrared Camera (NIRCam) and is estimated to be just about 1,600 lightyears across – much smaller than the Milkyway, which is about 100,000 light-years across.

Nonetheless, the galaxy despite its small size is estimated to be about a billion times more massive than our sun.

Alongside GLASS-z13, JWST also observed another distant galaxy in the neighborhood, called GLASS-z11

GLASS-z11, which is not as old, is about the same age as HD-1 and is 2,300 light-years across.

Both of these newly observed galaxies are a remarkable feat.

GLASS-z13 is NOT the Most Distant Galaxy in the Universe Yet – Here’s Why 

Ultimately, GLASS-z13 is only a “potential” candidate for the title of the oldest galaxy.

Yes, you heard it right; the record has not been broken, at least yet.

That is because the data, although groundbreaking, is not conclusive (similar to when we observed HD-1), and here’s why:

To observe any distant galaxy, we form a spectrum out of the data collected by the telescope to estimate the redshift of the galaxy, which in turn estimates the age of the galaxy.

However, in the case of GLASS-z11, the infrared light captured by JWST has been passed through several filters, which only allow certain frequencies to pass through, and a spectrum out of the filtered light has been approximated to estimate how the actual spectrum would look like.

The photons that leave those distant galaxies to reach us are red-shifted along the way (meaning their wavelength increases, or frequency decreases). 

These altered photons that go beyond a threshold wavelength (due to the redshift) are absorbed by neutral hydrogen atoms amidst their journey before they could reach us.

Hence, a spectrum of the galaxy is approximated using data that couldn’t reach our eyes.

Although the data looks super promising, we’re basically dealing with approximations and estimations, which is exactly why we cannot conclude that GLASS-z11 is the oldest galaxy in the universe.

We have to wait until JWST captures more data, which would refine the existing data into an adamant discovery.


Putting the awe-inspiring part of the discovery aside, the scientific implications are extensive as well.

“We searched all the early data for galaxies with this very striking signature, and these were the two systems that had by far the most compelling signature. Right now, our guess for the distance is based on what we don’t see – it would be great to have an answer for what we do see,”

Rohan Naidu, Harvard Center for Astrophysics

Maisie’s Galaxy – Distant Galaxy Observed at a Redshift of 14.4

The capabilities and limits of the James Webb Space Telescope seem insurmountable already, but there’s way more to it.

Just days after the discovery of GLASS-z13, astronomers have revealed another (very) distant galaxy, and this time, they didn’t see this coming!

On 25th July 2022, a team of astronomers led by astrophysicist Steven Finkelstein found another distant galaxy, way more distant than GLASS-z13 itself, and named it Maisie’s Galaxy (after Steven’s daughter of the same name).

The image on the left portrays the high redshift (14.4) of Maisie’s Galaxy, while the image on the right shows the galaxy in its true color. Credits: PBS

Maisie’s Galaxy is reported to have a photometric redshift of 14.4 and was observed to be within just 290 million years (or could even be within as early as 250 myr) after the big bang.

Graphical interpretation of the data obtained for Maisie’s Galaxy. The image on the left shows the spectral energy distribution of flux versus wavelength, whereas the image on the right shows the redshift probability distributions. Credits: PBS

The scientific community has been flooded by a number of research papers lately.

All such papers mention the extensive study of distant redshifted galaxies, one of which talked about Maisie’s Galaxy (read the research paper here).

Though, we must not forget that all data is photometric and not spectroscopic.

Photometry VS Spectroscopy

In simple terms, photometry is based on the study and measurement of light and its intensity (or brightness) as it is perceived by the human eyes.

Photometry uses a compensatory function of wavelength called the luminosity function that models light and its wavelengths the way they would be perceived by rods and cones present in our eyes.

On the other hand, spectroscopy is a much more detailed analysis and measurement of light and its properties.

In spectroscopy, a light spectrum is obtained by splitting the light into its constituent wavelengths (as it interacts with matter) and the wavelengths (and their characteristics) are then studied meticulously.

It has a broad range of applications in astronomy and astrophysics as it is the spectroscopic analysis of light coming from an object that reveals the true nature of the object that is being studied (like a galaxy).

In a separate study, astronomers claimed to have found two more distant galaxies with an approximating and whopping redshift of 16, while observing and analyzing Webb’s First Deep Field (refer to the link for more details).

A redshift of 16 makes the galaxy fall within 250 million years after the big bang.

All the data and research (including this one and that of Maisie’s Galaxy) have been submitted for peer review.

Only time will tell how solid these findings are on the grounds of physics.

If the spectroscopic data confirm the redshift that these galaxies (including the ones discussed previously in this article) are claimed to have, it would be a magnanimous achievement to have found these stellar abodes tracing back to the beginning of spacetime itself.

Do We Have a Winner?

So, ultimately, you might ask: Which galaxy is the most distant one ever observed? What is the one-word answer to the question, after all the ambiguity?

Well, there is a very honest three-word answer at least: we don’t know (to some extent)!


It could be Maisie’s Galaxy (as per the data) but what if a detailed study in the near future goes against it (although it’s unlikely, we never know)?

With so many galaxies fighting for the crown, scientists can not put out a final conclusion in favor of any one of them as all data is not perfectly conclusive and thus needs detailed study.

However, if you could hold us at gunpoint and compulsorily ask for an answer, we would say it’s the GN-z11 and that’s only because GN-z11 is the only galaxy with a confirmed spectroscopic analysis (while the others lack the same).

Though it is highly probable that the record held by GN-z11 could be shattered to pieces by the mighty contenders currently in the race.

We’re hoping that JWST collects more information so as to solidify the discovery and end the prevailing debate, once and for all.

Even the confirmation of the facts related to previously observed galaxies like HD-1 requires more in-depth research, especially now, when we have a powerful telescope like JWST, which itself holds enough power to spectroscopically analyze the light it captures.

With such advanced scientific equipment, we can finally accumulate enough data and study them to rectify the pre-existing assumptions in observational astronomy, which often make the foundation of the study ambiguous.

Despite all uncertainties or probable confusion, the recent discoveries of GLASS-z13 and Maisie’s Galaxy are definitely one (or maybe two, or more; our findings are anything but less) thing that you should be very fascinated about because no matter what, they’re eventually groundbreaking observations.

JWST is also expected to trace galaxies existing just about 200 million years after the big bang; that would be something!

With breathtaking discoveries at such frequencies, anything seems very much possible right now provided it’s in the hands of the mightiest telescope to date and the most brilliant minds on the planet.

Scientists would be able to peer deep through the cosmos all the way up to the earliest point in time – to the birth of primordial stars, galaxies, black holes, or even the birth of the universe.  

Considering how much more powerful JWST is, compared to Hubble, the observations and images that will follow are certainly going to dazzle us.