Module 03 · 8 min · Intermediate
Reading a Spectrum
How to interpret spectral graphs
Real spectrum: Orion Nebula, one cube pixel
DR1 cubeExtracting spectrum from the science cube… 0.0s
Hover to read values. Bars along the bottom show NHITS.
01
Axes
Wavelength (µm) runs left to right; surface brightness in MJy/sr runs up. The shape — slopes, dips, bumps — carries the physics.
02
Continuum vs features
Look for the smooth continuum first, then deviations that span several adjacent channels: absorption dips (ices, molecules) or emission bumps (PAHs, recombination lines).
03
Check the quality columns
NHITS tells you how many input pixels contributed; FLAGS tells you if a channel is suspect. A feature in flagged channels is not a feature yet.