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We present JWST/NIRSpec prism spectroscopy of MACS0647-JD, the triply-lensed$z \sim 11$ candidate discovered in HST imaging and spatially resolved by JWSTimaging into two components A and B. Spectroscopy of component A yields aspectroscopic redshift $z=10.17$ based on 7 detected emission lines: CIII]$\lambda\lambda$1907,1909, [OII] $\lambda$3727, [NeIII] $\lambda$3869, [NeIII]$\lambda$3968, H$\delta$ $\lambda$4101, H$\gamma$ $\lambda$4340, and [OIII]$\lambda$4363. These are the second-most distant detections of these emissionlines to date, in a galaxy observed just 460 million years after the Big Bang.Based on observed and extrapolated line flux ratios we derive a gas-phasemetallicity $Z =$ log(O/H) = $7.5 - 8.0$, or $(0.06 - 0.2)$ $Z_\odot$,ionization parameter log($U$) $\sim -1.9\pm0.2$, and an ionizing photonproduction efficiency ${\rm log}(\xi_{\rm ion})=25.2\pm0.2\,$erg$^{-1}$ Hz. Thespectrum has a softened Lyman-$\alpha$ break, evidence for a strong Ly$\alpha$damping wing, suggesting that MACS0647-JD was unable to ionize its surroundingsbeyond its immediate vicinity ($R_{\text{HII}} \ll 1$ pMpc). The Ly$\alpha$damping wing also suppresses the F150W photometry, explaining the slightlyoverestimated photometric redshift $z = 10.6 \pm 0.3$. MACS0647-JD has astellar mass log($M/M_\odot$) = $8.1 \pm 0.3$, including $\sim$ 6$\times 10^7M_\odot$ in component A, most of which formed recently (within $\sim$ 20 Myr)with a star formation rate $2\pm1 M_\odot$ / yr, all within an effective radius$70\pm24\,$pc. The smaller component B ($r \sim 20$) pc is likely older($\sim$100 Myr) with more dust ($A_V \sim 0.1$ mag), as found previously.Spectroscopy of a fainter companion galaxy C separated by a distance of \about\3$\,$kpc reveals a Lyman break consistent with $z = 10.17$. MACS0647-JD islikely the most distant galaxy merger known.

JWST NIRSpec spectroscopy of the triply-lensed $z = 10.17$ galaxy MACS0647$-$JD