Mintaka (δ Orionis)
The faintest and the westernmost of the three stars which appear in a row and make up the → Orion's Belt. It is a blue star of magnitude 2.23 lying 915 light-years away. Mintaka is in fact an → eclipsing binary with a period of 5.7 days. The main star has a → spectral type of O9.5 and radiates near 90,000 times the → solar luminosity. Mintaka is remarkable as regards the discovery of the → interstellar medium. The ISM was discovered by the German astronomer Johannes Hartmann (1855-1936) through the study of δ Orionis. He remarked that the calcium line at 3934 Å did not share in the periodic displacements of the lines caused by the orbital motion of the star. This suggested that the calcium line was not from the stars but from an intervening interstellar absorbing cloud.
Mintaka, from al-Mintaqah "the belt," from al-Mintaqah al-Jauzâ'