A near-infrared triplet of this ion's spectral lines is prominent in a class of supernovae named for being rich in this ion. For 10 points each:
[10h] Name this atomic ionization state responsible for a 393-nanometer spectral line whose width correlates strongly to a star’s absolute magnitude in the Wilson–Bappu effect.
ANSWER: calcium (II) (“calcium two”) [or calcium 1-plus or calcium plus-1 or singly-ionized calcium; prompt on calcium; reject “calcium 2-plus”]
[10m] The calcium (II) doublet forms the H and K lines in a series of spectral lines found by this scientist. This German inventor of the spectroscope names an equation used to model far-field diffraction.
ANSWER: Joseph von Fraunhofer [accept Fraunhofer lines or Fraunhofer diffraction equation]
[10e] Using the Wilson–Bappu effect, the H and K lines form one “rung” of a ladder used to calibrate this quantity. Type Ia (“one-A”) supernovae are used to measure values of this quantity around 100 megaparsecs.
ANSWER: distance [or length; accept more specific answers like distance from Earth]
<Jeremy Cummings, Other Science>