Classis spectralis

Classis spectralis, in astronomia, est divisio stellarum in classes secundum temperaturam vel magnitudinem. Sunt plures classificationes quae inter se differunt.

Classificatio Harvardiana

Classificatio Harvardiana

Classificatione Harvardiana, stellae dividuntur in classes O—B—A—F—G—K—M—C—S. Plerumque communes sunt stellae classium O—B—A—F—G—K—M, quae appellantur "stellae normales," sed stellae classium C—S (olim R, N) sunt "stellae peculiares," hoc est stellae quae spectrum "peculiare" habent.

Tabula classium

Classis	Temperatura	Color verus	Coror visibilis[1][2]	Massa (in massis Solis)	Radius (in radiis Solis)	Luminsoitas	Lineae Hydrogenii	% e stellis seriei capitalis
O	30,000–60,000 K	caeruleus	caeruleus	60 M☉	15 R☉	1,400,000 L☉	debiles	~0.00003%
B	10,000–30,000 K	albus-caeruleus	albus caeruleus albusque	18 M☉	7 R☉	20,000 L☉	medii	0.13%
A	7,500–10,000 K	albus	albus	3.1 M☉	2.1 R☉	80 L☉	lucidi	0.6%
F	6,000–7,500 K	ochroleucus	albus	1.7 M☉	1.3 R☉	6 L☉	medii	3%
G	5,000–6,000 K	flavus	ochroleucus	1.1 M☉	1.1 R☉	1.2 L☉	debiles	8%
K	3,500–5,000 K	aurantius	rutilus	0.8 M☉	0.9 R☉	0.4 L☉	admodum debiles	13%
M	2,000–3,500 K	ruber	flammeus	0.3 M☉	0.4 R☉	0.04 L☉	admodum debiles	>78%

Classificatio Yerkes

Factor supplementaruis afficiens in characterem spectri est densitas stratorum exteriorum stellae, dependens a massa et densitate stellae, hoc est a luminositate. Admodum a lumnositate SrII, BaII, FeII, TiII dependunt, propterea est differentia spectrorum stellarum gigantum et pumilionum aequalibus classibus Harvardianis.

Ha clssificatione stella habet classem luminocitatis:

• I Supergigantes
  • Ia-0 hypergigantes vel lucidissimi supergigantes
  • Ia lucidi supergigantes, e.g. Deneb (spectrum A2Ia)
  • Iab Supergigantes mediocriter lucidi
  • Ib minus lucidi gigantes, e.g. Betelgeuse (spectrum M2Ib)
• II Lucidi gigantes
  • IIa, e.g.: β Scuti (HD 173764) (spectrum G4 IIa)
  • IIab, e.g.: HR 8752 (spectrum G0Iab:)
  • IIb, e.g.: HR 6902 (spectrum G9 IIb)
• III e.g.: gigantes
  • IIIa, e.g.: ρ Persei (spectrum M4 IIIa)
  • IIIab, e.g.: δ Reticuli (spectrum M2 IIIab)
  • IIIb, e.g.: Pollux (spectrum K2 IIIb)
• IV subgigantes
  • IVa, e.g.: ε Reticuli (spectrum K1-2 IVa-III)
  • IVb, e.g.: HR 672 A (spectrum G0.5 IVb)
• V series principalis
  • Va, e.g.: AD Leonis (spectrum M4Ve)
  • Vb, e.g.: 85 Pegasi A (spectrum G5 Vb)
• VI suppumiliones (rare, obsoletum)
• VII pumilio alba (rare, obsoletum)

Classificatio Harvardiana definit Abscissam diagrammatis Hertzsprung—Russell, sed Yerkes classificatio — positionem stellae in diagrammate. Supplementaria autem praestantia huius classificationis est possibilitas definendi luminocitatem sellae (spectro cognoto), et propterea possibilitas aestimandi distantionem ad stellam.

Sol, pumilio flava, habet classem spectralem G2V.

Exemplaria spectrorum stellarum variarum

Spectrum stellae classis O5V

Spectrum stellae classis B2II

Spectrum stellae classis A2I

Spectrum stellae classis F2III

Spectrum stellae classis G5III

Spectrum stellae classis K4III

Spectrum stellae classis M0III

Spectrum stellae classis M6V

Notae

1. The Guinness book of astronomy facts & feats, Patrick Moore, 1992, 0-900424-76-1
2. "The Colour of Stars". Australia Telescope Outreach and Education. December 21 2004  — Explains the reason for the difference in color perception.

Bibliographia

• Hearnshaw, J. B. The Analysis of Starlight: Two Centuries of Astronomical Spectroscopy. Novi Eboraci: Cambridge University Press, 2014.
• Kaler, James B. Stars and their Spectra: An Introduction to the Spectral Sequence. Cantabridgiae: Cambridge University Press, 2011.