A variety of elemental violet lines occur in the star Sirius. These include calcium (Ca I & II), iron (Fe I), magnesium (Mg I & II), manganese (Mn I & II), nickel (Ni II), scandium (Sc II), silicon (Si II), strontium (Sr II), titanium (Ti II), vanadium (V II), yttrium (Y II), and zirconium (Zr II).
Around 150 AD, the Hellenistic astronomer Claudius Ptolemy described Sirius as reddish, along with five other stars, Betelgeuse, Antares, Aldebaran, Arcturus and Pollux, all of which are clearly of orange or red hue. The discrepancy was first noted by amateur astronomer Thomas Barker, ... who prepared a paper and spoke at a meeting of the Royal Society in London in 1760. The existence of other stars changing in brightness gave credence to the idea that some may change in colour too; Sir John Herschel noted this in 1839, possibly influenced by witnessing Eta Carinae two years earlier. Thomas Jefferson Jackson See resurrected discussion on red Sirius with the publication of several papers in 1892, and a final summary in 1926. He cited not only Ptolemy but also the poet Aratus, the orator Cicero, and general Germanicus as colouring the star red, though acknowledging that none of the latter three authors were astronomers, the last two merely translating Aratus' poem Phaenomena. Seneca, too, had described Sirius as being of a deeper red colour than Mars. However, not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius described it as "sea-blue", as did the 4th century Avienus. It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue.
In 1985, German astronomers Wolfhard Schlosser and Werner Bergmann published an account of an 8th century Lombardic manuscript, which contains De cursu stellarum ratio by St. Gregory of Tours. The Latin text taught readers how to determine the times of nighttime prayers from positions of the stars, and Sirius is described within as rubeola — "reddish". The authors proposed this was further evidence Sirius B had been a red giant at the time.
Both Al I absorption lines at 394.401±8.5 and 396.152±6.5 have been measured for Sirius.
The chemistry of vanadium includes four adjacent oxidation states 2-5. In aqueous solution the colours are lilac V2+(aq), green V3+(aq), blue VO2+(aq) and, at high pH, yellow VO42-.
Vanadium (V II) has an absorption band, 392.973-403.678 nm, with an excitation potential range of 1.07-1.81 eV.
Chromium has absorption lines that occur at 425.435-428.972 nm from Cr I and 400.333-428.421 nm, 3.09-6.46 eV from Cr II near Sirius.
Manganese (Mn I) has two absorption bands at 403.449±1.4 nm and 405.554±0.8 nm, where the second has an excitation potential of 2.13 eV.
Manganese (Mn II) has an absorption band at 420.638±0.8 nm with an excitation potential of 5.37 eV.
- Kozo Sadakane and Minoru Ueta (August 1989). "Abundance Analysis of Sirius in the Blue-Violet Region". Publications of the Astronomical Society of Japan 41 (2): 279-88.
- J.B. Holberg (2007). Sirius: Brightest Diamond in the Night Sky. Chichester, UK: Praxis Publishing. ISBN 0-387-48941-X.
- R. C. Ceragioli (1995). "The Debate Concerning 'Red' Sirius". Journal for the History of Astronomy 26 (3): 187–226.
- Whittet, D. C. B. (1999). "A physical interpretation of the 'red Sirius' anomaly". Monthly Notices of the Royal Astronomical Society 310 (2): 355–359. doi:10.1046/j.1365-8711.1999.02975.x.
- 江晓原 (1992). "中国古籍中天狼星颜色之记载" (in Chinese). Ť文学报 33 (4).
- Jiang, Xiao-Yuan (April 1993). "The colour of Sirius as recorded in ancient Chinese texts". Chinese Astronomy and Astrophysics 17 (2): 223–8. doi:10.1016/0275-1062(93)90073-X.
- Schlosser, W.; Bergmann, W. (November 1985). "An early-medieval account on the red colour of Sirius and its astrophysical implications". Nature 318 (318): 45–6. doi:10.1038/318045a0.