Characteristics of Stars
Constellations – imaginary patterns
of stars
Circumpolar – five constellations in
the Northern Hemisphere that
circle the pole star (Polaris)
Classification of Stars
Stars are classified by their color,
temperature, size, brightness, and
composition
Composition is determined by a spectrograph – a device
that breaks light into colors and produces an image of
the resulting spectrum
Brightness depends on size and temperature and
there are two types
• Apparent – brightness as seen from Earth
• Absolute – brightness the star would have if it were at a
standard distance from Earth
Measuring Distance
Astronomers use light years – the
distance that light travels in one
year, about 9.5 million million
kilometers
Astronomers use parallax – the
apparent change in position of an
object when you look at it from
different places
• Hertzsprung-Russell
(HR) Diagram
– graph used to determine
a stars classification
– it helps identify stars by
color, size, temperature
and brightness.
– about 90% of stars fall
on the main sequence.
– the other 10% of stars
were once main
sequence stars.
– can help determine
where a star is in its
lifecycle