Caption: Cartoon of a Hertzsprung-Russell (HR) diagram with stars (NOT quantitatively accurate) (FK-428).
On an HR diagram, temperature increases to the left: just an old convention of astronomy---that no one's had the guts to change.
From stellar modeling, we know that main sequence stars have hydrogen burning in the core.
The core hydrogen burning phase is the longest phase of the nuclear burning and this explains why most stars undergoing nuclear burning are on the main sequence.
However, stars above the main sequence can be very luminous, and so are conspicuous out of proportion to their abundance.
There is an absolutely positively important rule to remenber in discussing main-sequence stars:
EOF
Caption Credit/Permission: ©
David Jeffery,
2004 / Own work.
Image link: Itself.
Local file: local link: star_hr_named_stars_cartoon.html.
File: Star file:
star_hr_named_stars_cartoon.html.
