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GLASS-z12: Lyman-break galaxy

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GLASS-z12, also named GHZ2 (formerly known as GLASS-z13) is a Lyman-break galaxy discovered by the Grism Lens-Amplified Survey from Space (GLASS) observing program using the James Webb Space Telescope's NIRCam in July 2022.

It has a spectroscopic 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 the Big Bang, or about 2,57% of its current age.

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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 on arXiv the same day. Hence these two names for this galaxy of GLASS-z12 (Naidu et al. 2022) and GHZ2 (Castellano et al. 2022a).

GLASS-z12 derives its name from the GLASS survey that discovered it and its estimated photometric redshift of approximately z = 12.4+0.1
−0.3. GLASS-z12 was initially announced as GLASS-z13 because it was thought to have a higher redshift of z = 13.1. This redshift value was later revised down to z = 12.4 in October 2022, resulting in the renaming of this galaxy.

It was discovered alongside another galaxy, GLASS-z10, comparable to GN-z11, also one of the oldest galaxies discovered.