Download Astronomy – Studying the Stars & Space

Years of Classifying Stars
• Letters were
assigned to stars of
different spectrum.
• Stars were
classified by the
elements they were
made of
• Stars are now
classified by how
hot they are and
arranged by class
and temperature
blue
30,000
degrees +
helium
10
Lacerate
Blue &
white
7,500 –
30000
degrees
Hydrogen
and
helium
Vega,
Rigel,
Sirius
white
Yellow
6,000 – 7,
500 degrees
Hydrogen
and
heavier
elements
Procyon
Yellow
5,000-6,000
degrees
Calcium
and other
metals
The sun &
Capella
orange
3,500-5,000
degrees
Calcium
and other
molecules
Aldebaran
red
Less than 3,
500 degrees
molecules
Betelgeus
e
Types of Stars
• Stars are classified
by how hot they are
• Brightest stars in
the sky are called
1st magnitude
• Dimmest are called
6th magnitude
• Positive number
stars are dim stars,
and negative
numbers represent
brightest stars
Quasars
• A very bright
(luminous) star-like
object that generates
energy at a high rate.
• Thought to be the
most distant objects in
the universe
• Some are as massive as
10 billion of our Suns
• Most powerful energy
source in the universe
Blue Stars
• The hottest
stars are blue
stars such as
Rigel, =30,000
ºC
• Brightest star
in our night sky
is Sirius
Pulsar
• A rapidly spinning
neutron star that
emits rapid pulses
of radiation
• Develops at the
end of a stars life
as a last gasp
before it goes
“supernova”
Types of Brightness
• Absolute
Magnitude
– The actual
brightness of a
star
– The brightness
that a star would
have at a distance
of 32.6 light years
from Earth
– Sun’s magnitude is
+4.8
• Apparent
Magnitude
– The brightness of
a star as it is seen
from Earth
– Our sun is very
close to us so it
has an apparent
magnitude of 26.8 but only an
absolute
magnitude of +4.8
which makes it
“apparently small”
Main Sequence Stars
• Second and longest
stage of a star’s
life
• Energy is generated
in the core of the
star as hydrogen
fuses to helium
• Size of the star
remains constant as
long as the core is
full of hydrogen
Red Giant & Super giant
• A star that expands
and cools once all of
its hydrogen is gone
• Center of the star
shrinks and its
atmosphere grows
• Can be 10 times
bigger than our sun
as red giant or 100
times bigger as a
super giant
White Dwarf
• A small hot star
that is the
leftover center
of an older star
• Has no hydrogen
left
• Final stage of a
star’s life
• Can shine for
billions of years
before they cool
completely
When Stars Get Old . . .
Black hole
Supernova
• an object so massive
• massive blue stars
and dense that even
use their hydrogen
quickly and may
light cannot escape
explode in a huge
its gravity
bright flash
• Gas or dust that sink
• Can be brighter than
into black hole from a
an entire galaxy for
star
form
x-ray
light
several days
which may indicate a
• A collapsed star can
black
holes’
existence
become a pulsar
Hertzsprung-Russell Diagram
• A graph that shows
the relationship
between a star’s
surface
temperature and
absolute magnitude
• Shows how they are
classified by
brightness and
temperature and
how they change
cool red to the right, bright stars
over time
Hot blue stars are on the left
on top and dim stars on the bottom
Other Terms
• Spectrum – the band of color produced
when white light passes through a prism
• Parallax – an apparent shift in the
position of an object when viewed from
different locations
• Main sequence – the location on the H-R
diagram where most stars lie
• Neutron star – a star that has collapsed
under gravity to the point that the
electrons and protons have smashed
together to form neutrons