| GHZ2 | |
|---|---|
 Close-up view of GLASS-z12 from theJames Webb Space Telescope | |
| Observation data (J2000epoch) | |
| Constellation | Sculptor |
| Right ascension | 00h 13m 59.76s[1] |
| Declination | −30° 19′ 29.1″[1] |
| Redshift | 12.117±0.012 (spectroscopic)[2] 12.4+0.1 −0.3[1] 12.42+0.27 −0.14[3] 12.28+0.08 −0.07[4] |
| Distance |
|
| Apparent magnitude (V) | 27.0AB (F200W)[1] |
| Characteristics | |
| Mass | ≈1.0×109 M☉ |
| Size | ~3000 ly (1 kpc) |
| Half-light radius (physical) | 500pc |
| Other designations | |
| GHZ2[6][7] · GLASS-17487[3] | |
References:[1] | |
GHZ2, also namedGLASS-z12 (formerly known asGLASS-z13) is aLyman-break galaxy discovered by the Grism Lens-Amplified Survey from Space (GLASS) observing program using theJames Webb Space Telescope'sNIRCam in July 2022.[8][9]
It has aspectroscopic redshift of 12.34, making it one of the most distant galaxies and astronomical objects ever discovered. According to current theory, this redshift corresponds to a time about 13.44 billion years ago, approximately 355 million years after theBig Bang, or about 2.57% of itscurrent age.[10]
GLASS-z12/GHZ2, was initially discovered as a robust z ≈ 12.0–12.5 candidate by Castellano et al. and Naidu et al. in the GLASS-JWST Early Release Science NIRCam field. The two discovery papers appeared onarXiv the same day. Hence these two names for this galaxy of GLASS-z12 (Naidu et al. 2022) and GHZ2 (Castellano et al. 2022a).[11]
GLASS-z12 derives its name from the GLASS survey that discovered it and its estimatedphotometric redshift of approximately z =12.4+0.1
−0.3.[1] GLASS-z12 was initially announced asGLASS-z13 because it was thought to have a higher redshift of z = 13.1.[7][2] This redshift value was later revised down to z = 12.4 in October 2022, resulting in the renaming of this galaxy.[1]
It was discovered alongside another galaxy, GLASS-z10, comparable toGN-z11, also one of the oldest galaxies discovered.[12]
Spectroscopic observations of GLASS-z12 by theAtacama Large Millimeter Array (ALMA) in August 2022 confirmed that the galaxy has aspectroscopic redshift of12.117±0.012, making it one of the earliest and most distant galaxies ever discovered, dating back to 360 million years after theBig Bang,13.44 billion years ago.[12][5] ALMA observations detected an emission line associated withdoubly ionized oxygen (O III) at 258.7 GHz with a significance of 5σ, suggesting that there is very low dust content in GLASS-z12, if not theearly universe as well.[2] Also based on oxygen-related measurements, the age of the galaxy is confirmed.[13][14]
GLASS-z12 has a light-travel distance (lookback time) of 13.4 billion years.[5] However, due to theexpansion of the universe, itspresent proper distance is 32.718 billion light-years.[5]
This galaxy was observed again in October 2023 by theJames Webb Space Telescope with theNIRSpec andMIRI spectrographs, making it the most distant redshift galaxy of z = 12.34 with full spectroscopic coverage from ultraviolet (UV) to optical.[11][15]
According to currentΛCDM parameters (H0 = 67.4, Ωm = 0.315, ΩΛ = 0.685), this redshift of 12.34 corresponds to a light-travel distance (lookback time) of 13.44 billion years. However, due to theexpansion of the universe, itscomoving distance is 32.837 Gly.[16]
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