A Forest of Emission Lines Observed by Sunrise III/SUSI above the Solar Limb

We present off-limb spectroscopy using low-stray-light data from the Sunrise Spectropolarimeter and Imager (SUSI) on board the S unrise iii stratospheric solar observatory. A spatial scan with SUSI’s slit almost parallel to the local limb reached from within the solar disk to 6.5 Mm off-limb. The wavelength range spanned from 407.6 to 410.25 nm. We detected a total of 174 spectral lines in emission off-limb, a 2.5-fold increase over previous reports. Surprisingly, 122 of these lines begin to appear in emission already on the disk, although close to the limb. In addition, one-fifth of relatively prominent emission lines are due to rare-earth and heavy elements and molecules, where the absorption lines of these transitions are typically weak on-disc.