Stellar Classification Quiz

Study Notes

Stellar Classification

Stellar classification categorizes stars based on their spectral characteristics.
More than 90 percent of all stars are found on the main sequence, a prominent diagonal area on the H-R diagram.

Main Sequence Stars

O-class stars: Hot, massive stars with high luminosity (spectral type O, luminosity class V).
B-class stars: Hydrogen-burning stars of spectral type B (luminosity class V).
A-type stars: Exhibits strong hydrogen absorption lines.
F-type stars: Hydrogen-fusing stars of spectral type F (luminosity class V).
G-type stars: Often known as yellow dwarfs, these stars are spectral type G.
K-type stars: Known as K dwarfs or orange dwarfs, these are hydrogen-burning stars of spectral type K.
M-type stars: Known as red dwarfs, they are the smallest and coolest stars on the main sequence.

Advanced Stellar Types

Brown dwarfs: "Failed" stars lacking sufficient mass for nuclear fusion.
Wolf-Rayet stars: Identified over 220, very hot (25,000 to 100,000 K), rapidly losing mass (over 10^-5 solar masses/year), with extreme wind speeds (800 to 3000+ km/s).
OB stars: Hot, massive stars (spectral types O or early B) that form OB associations.

Subdwarf Classification

Subdwarf (sd): Stars with luminosity class VI, exhibiting lower luminosity than regular main-sequence stars.
Subdwarf O stars (sdO): Hot, low-mass stars.
Subdwarf B stars (sdB): A specific kind of subdwarf star with spectral type B.

Stellar Evolution Stages

Subgiants: Intermediate stars between main-sequence and giants with inert helium cores and hydrogen-fusing shells.
Giants: Large, bright stars with exhausted hydrogen in their cores.
Blue giants: Extremely hot, large, and bright stars.
Yellow giants: Luminous giant stars of low or intermediate mass in later evolutionary phases.
Red giants: Large, reddish stars at a late life stage.

Supergiants

Bright giants: Highly evolved massive stars, classified as Luminosity Class II.
Supergiants: Very large stars, brighter than giants, despite being relatively cool.
Blue supergiants: Largest and hottest stars located at the upper-left end of the main sequence.
Red supergiants: Massive stars during their expansion phase, becoming very bright.
Yellow supergiants: Stars, typically of spectral type F or G, classified as supergiants.

Hypergiants

Hypergiants: Extremely massive and luminous stars that lose mass rapidly due to their size.
Yellow hypergiants: Massive stars with extended atmospheres and significant mass loss, possessing spectral classes from A to K.

Unique Stellar Types

Carbon stars: Red giants with strong absorption lines of carbon.
S-type stars: Cool giants with equal amounts of carbon and oxygen in their atmospheres.
CN stars: Stars exhibiting unusually strong cyanogen bands in their spectra.

Description

Test your knowledge of stellar classification and the characteristics of various types of stars. This quiz covers everything from O-class to M-type stars, including the main sequence and advanced stellar types. Understand how stars are categorized based on their spectral characteristics.