In August 2022, James Webb Space Telescope (JWST) discovered a distant smudge of light. It was named Maisie's galaxy after a lucky birthday girl. Now, after careful assessment and with the help of advanced instruments, astronomers were able to calculate the accurate age of Maisie's galaxy.
First Galaxy To Be Spectroscopically Confirmed
Astronomers confirmed that Maisie's galaxy was born 390 million million years after the Big Bang, making it about 13.4 billion years old. That means it is also approximately 70 years yonder than the current oldest-known galaxy, the JADES-GS-z13-0.
This remarkable timeframe was documented on a study, titled "Confirmation and refutation of very luminous galaxies in the early universe" published on August 14 in the journal Nature, putting Maisie's galaxy within the exclusive group of the four most ancient galaxies in the universe, whose ages have been validated through spectroscopy.
Spectroscopy, a technique that dissects light into its constituent frequencies to provide a clearer insight into its luminosity, warmth, and chemical structure, was employed for this confirmation.
Steven Finkelstein, an astronomy professor at the University of Texas at Austin, noted that adding to the fascination surrounding Maisie's galaxy is its inclusion among the earliest distant galaxies pinpointed by JWST. Of even greater significance is the fact that within this group, it holds the distinction of being the very first to undergo confirmation through spectroscopy.
The galaxy was detected during JWST's initial observation period, wherein it was initially thought to be extremely old due to its brightness and redshift, which suggests a greater distance in an expanding universe.
However, relying solely on light brightness for redshift assessment can be misleading, as different elements emit light at various frequencies, distorting an object's true age and distance. To overcome this, astronomers use spectroscopy to dissect starlight into its constituent frequencies, uncovering its composition.
How Did Astronomers Performed the Spectroscopic Confirmation?
The crucial spectroscopic confirmation was achieved through the application of JWST's Near InfraRed Spectrograph (NIRSpec), conducted as part of the Cosmic Evolution Early Release Science Survey (CEERS).
NIRSpec divides light into precise frequencies to determine chemical composition, thermal emission, luminosity, and motion. Redshift, caused by motion away from the observer and resulting in light shifting to longer wavelengths, crucially improved dating accuracy compared to initial photometry.
By assigning a redshift value of z=11.4 to Maisie's galaxy, the advanced techniques enabled the research team to establish a revised timeline of approximately 390 million years after the occurrence of the Big Bang.
The effective use of NIRSpec and redshift determination showcases advanced spectroscopy's potency in revealing celestial object properties, underscoring the value of blending leading-edge technology with careful analysis for insights into early universe stages and distant galaxies.
Moreover, the astronomers studied CEERS-93316, a galaxy initially thought to be 235 million years older than the Big Bang. However, further analysis revealed its redshift to be z=4.9, indicating an age of just one billion years after the Big Bang.
The earlier miscalculation stemmed from the galaxy emitting unusual light in narrow frequency bands linked to oxygen and hydrogen, which caused it to appear bluer than its actual nature.
Lead researcher Finkelstein attributed the mistake to an uncommon case, noting that among the many high redshift candidates observed spectroscopically, this was the sole instance of a significantly lower redshift than initially assumed.
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