The Solar System

106

104

102

1

10 –2

10 –4

–5

0

5

10

L/L

M

v

Temperature (K)

30,00030,000 20,00020,000 10,00010,000 (^500050003000300020002000)
OBAFGKMOBAFGKM
Rigel A
Deneb
Polaris
Betelgeuse
Antares
Canopus
Spica B
Spica A
Adara
Alnilam
Rigel B
Vega
Sirius A
Sirius B
Altair
Procyon A
Procyon B
Van Maanen’s Star
Wolf 486
Wolf 1346
40 Eridani B
Aldebaran B
Barnard’s Star
α Centauri B
Pollux
Arcturus
Mira
Aldebaran A
Capella A
Capella B
0.001R
0.01R
0.1R
1R
10R
100R 1000R
Superg
iants
Gia
nts
Ma
ins
equ
enc
e
Whi
ted
warf
s
Note: Star sizes are not to scale.
Red
dwarfs
Sun
The H–R diagram is the key to understanding stars, their birth, their long lives, and their
eventual deaths. Luminosity (L/L) refers to the total amount of energy that a star emits
in terms of the sun’s luminosity, and the temperature refers to the temperature of its
surface. Together, the temperature and luminosity of a star locate it on the H–R diagram
and tell astronomers its radius, its family relationships with other stars, and a great
deal about its history and fate.