Though it may not look like much in images, appearing as just a glowing orange blob of light, Maisie's galaxy shows that when it comes to space, appearances can be deceptive.
As one of the first objects captured by the powerful James Webb Space Telescope in the summer of 2022, this simple splotch represents the dawn of a new age for astronomy because of how utterly ancient it appears to be.
And now, scientists have officially confirmed precisely how old the universe was during the point at which we see Maisie's galaxy, concluding that this realm is indeed one of the earliest ever discovered. The team's observations showed that Maisie's galaxy existed when the 13.8 billion-year-old universe was just around 390 million years old, which is incredibly young for our cosmic expanse.
This makes it one of the four earliest galaxies ever seen by human eyes.
"This galaxy exists at a time early enough in the universe that we really were not able to see it without JWST," Steven Finkelstein, an astronomer at the University of Texas at Austin and the principal investigator for the Cosmic Evolution Early Release Science Survey (CEERS), told Space.com. "This was the undiscovered frontier where we really didn't know how the galaxies formed or what they looked like until we went and looked for them with the JWST. And when the first data came in last summer, Maisie's galaxy was one of the first galaxies that such early times that were identified."
And an important galaxy deserves a special name.
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What did you get for your 9th birthday? Maisie has you beat
With other galaxies spotted by the JWST possessing rather dry and formal monikers, such as CEERS 1019, CEERS 2782, and CEERS 746, Maisie's galaxy clearly stands out a little.
The early galaxy actually takes its name from Finkelstein's daughter, who is ten this year. That means young Maisie joins a list of luminaries such as Swiss astronomer Fritz Zwicky, French astronomer Édouard Jean-Marie Stephan, and American astronomer Carl Keenan Seyfert, all of whom had galaxies named after them. None of these influential scientists managed such an auspicious achievement at the tender age of nine years old, however, unlike Maisie.
"We found the galaxy in JWST data on my daughter's ninth birthday. My daughter's name is Maisie, and she had been asking me to name a galaxy after her, and I told her we weren't really allowed to do that. But because we found it on her birthday, I just started calling it Maisie's galaxy," Finkelstein explained. "When it came time to write the paper, and we were debating about what to call the galaxy because we'd already been calling it that, folks suggested just putting 'Maisie's galaxy' in there and seeing what happened. We managed to get it through and published with that name."
And Maisie herself couldn't be more delighted to share a name with such an important galaxy, according to her father.
But while Finkelstein is hardly likely to get the age of his daughter wrong, galaxies in the early universe are somewhat trickier to place an age on. That means confirming how old the universe was at the time the JWST saw Maisie's very own galaxy took some careful investigation.
Seeing red: How astronomers confirmed the age of Maisie's galaxy
To determine how distant a galaxy is, how long its light has been traveling to us and thus what period the universe was in during the time we have witnessed it it, astronomers use a measure called "redshift."
Different wavelengths of light correspond to different colors; so in the visible spectrum, long-wavelength, low-frequency light is red while short-wavelength, high-frequency light is blue.
As light travels through the universe to us from a distant source, such as an early galaxy, the expansion of the cosmos causes that source to simultaneously move away from us. This, in turn, results in wavelengths of light the source is emanating to get stretched out, causing them to lose energy and change frequency. In other words, once blueish, high-frequency and short-wavelength light gradually turns to reddish, low-frequency and long-wavelength light.
Astronomers refer to this change as "redshift" because the light is essentially being "shifted" toward the red end of the electromagnetic spectrum. Eventually, that light can even tread into infrared waters. Infrared light is basically invisible to human eyes.
The longer cosmic light has been traveling, the more extreme that redshift is. In the case of early galaxies like Maisie's galaxy, light has been traveling for around 10 billion years before hitting the JWST's mirrors. As a result, light that may have left Maisie's galaxy as part of the electromagnetic spectrum's visible region has been shifted down to the infrared section before reaching the spaceborne observatory.
But this is exactly why the JWST is such a remarkable tool for hunting for objects in the early universe.
Launched on Christmas Day in 2021, the powerful space telescope is adept at seeing long-wavelength infrared light. In fact, Finkelstein is clear that discovering Maisie's galaxy wouldn't have been possible prior to the JWST's tenure.
"We really could not see it before the JWST," he explained. "The Hubble Space Telescope was neither big enough nor, most importantly, did it cover 'red enough' wavelengths to see such a distant, highly redshifted galaxy."
Initial estimations of the redshift, and thus age, of Maisie's galaxy were based on photometry, which works by analyzing brightness in images while using a small number of wide-frequency filters. These calculations suggested the galaxy had a redshift of 11.8. But Finkelstein and the CEERS team wanted a more accurate age estimation.
To do this, they made follow-up observations with the JWST's Near-Infrared Spectrograph (NIRSpec). This allowed Finkelstein and colleagues to look at spectral lines created in light data, dictated by the absorptions and emissions of chemical elements at specific wavelengths. From there, they could pinpoint the actual redshift of Maisie's galaxy. It appeared to be 11.4.
This means Maisie's galaxy is technically seen more recently in the universe than initially estimated, by a factor of tens of millions of years. Nonetheless, it is still considered immensely old. The JWST captured the galaxy as it was just 390 million years after the Big Bang.
What was the universe like when Maisie's galaxy is seen?
Finkelstein explained that Maisie's galaxy would be distinguishable from galaxies in the universe today, including the Milky Way, as it is much smaller. This size is because of the dense state the universe was in during that epoch of cosmic history.
"The universe was quite active when Maisie's galaxy was seen because it was a lot smaller than it was today. So everything was squished in a much smaller volume," Finkelstein said. "Also, galaxies were closer together then, and merging much more frequently. Because the universe was only around 400 million years old at that time, essentially, all the stars that are around are young, so there were a lot more brighter and bluer stars then than we see in galaxies today."
Maisie's galaxy is also distinct from most "modern" galaxies in that, at the point we're observing it, it appears to be rapidly birthing young, blue stars. It was captured during a period in a galaxy's existence that astronomers call "starburst."
Because its young stars are bright and blue, this means (somewhat ironically) that this highly redshifted galaxy is actually much "bluer" than astronomers expected.
"There are small galaxies around today, but Maisie's galaxy is performing star formation at a much greater rate. And it's much more compact," Finkelstein said. "It's really like a blue, compact ball of stars."
This blueness also tells the team Maisie's galaxy is low in heavy elements and has a primordial composition of mostly hydrogen and helium. Maisie's galaxy is also much brighter than astronomers expected for an early galaxy, a feature that's also being found with other early galaxies observed with the JWST.
"Maisie's Galaxy gave us the first hint that early galaxies are a little bit brighter than we had expected, which makes them easier to find," Finkelstein said. "Our idea about how stars form in the universe early epoch may need a bit of revision. It's possible that galaxies were forming stars more efficiently then than we thought. Maybe they're just cranking out stars at a higher rate, with that making galaxies brighter and easier to see."
Finkelstein will now continue to examine Maise's galaxy with the JWST's Mid-Infrared Instrument (MIRI), delving deeper into the realm's light spectrum in an attempt to discover how rich it is with heavy elements, and understand whether it hosts any interstellar dust grains.
"Maisie's galaxy certainly gives us a good example case of what a galaxy in the early universe is, and because it's quite bright, we can study it pretty easily, and we can measure lots of things about it like its stellar mass, its shape and the amount of heavy elements within it," Finkelstein concluded. "In the end, it is one of many galaxies that we can use to learn about the early universe."
A paper on this study was published on Aug. 14 in the journal Nature.
