Download lifedeath - University of Glasgow

The Life and Death
of Stars
Dr Martin Hendry
University of Glasgow
How do stars and
planets form?
from
Nebulae
How do stars and
planets form?
from
Nebulae
The Orion Nebula
Forming stars
Forming stars
versus
Gas pressure trying
to expand the cloud
Forming stars
versus
Gravity trying to
collapse the cloud
Collapse often caused
by the shock wave
from a Supernova
Hydrogen fusion – fuelling a star’s nuclear furnace
H = Hydrogen
He = Helium
E = mc
2
Repulsive
Potential
Energy
Nuclear fusion only occurs at very
high temperatures, because atomic
nuclei tend to repel each other
Coulomb
Barrier
0
Distance
Starlight is electromagnetic radiation
The Electromagnetic
Spectrum
Stars of different
colours have different
temperatures
Temperature and colour of a star
are related by Wien’s Law
4000K
5000K
6000K
7000K
Surface temperature (K)
25000
10000
8000 6000
5000 4000 3000
106
-10
Supergiants
-5
102
0
Giants
1
+5
10-2
+10
10-4
+15
O5 B0
A0
F0
G0
Spectral Type
K0
M0
M8
Absolute Magnitude
Luminosity (Sun=1)
104
We can plot the
temperature and
luminosity of stars
on a diagram
Stars don’t appear
everywhere: they
group together,
and most are
found on the
Main Sequence
Surface temperature (K)
25000
10000
8000 6000
5000 4000 3000
106
-10
Supergiants
-5
102
0
Giants
1
+5
10-2
+10
10-4
+15
O5 B0
A0
F0
G0
Spectral Type
K0
M0
M8
Absolute Magnitude
Luminosity (Sun=1)
104
Stars found on the
Main Sequence
convert hydrogen
into helium.
Stars like the Sun
can do this for
many billions of
years, using the
P-P chain of
nuclear reactions
Surface temperature (K)
25000
106
10000
8000 6000
.
5000 4000 3000
. .
.
.
.. .
. .
. ..
.
. ..
..
.
...
.. . ....
..
. .. ..... ... .
. ..
.
... . . ... ........ .
.. .... .
.. .
. .....
......
......
.. ..
..... .
......
. .
...
. .
. ... ...
..
Deneb
-10
Rigel
Betelgeuse
Antares
Luminosity (Sun=1)
Arcturus
102
Aldebaran
Regulus
Vega
Procyon A
Altair
10-2
Pollux
Sun
Procyon B
O5 B0
+5
+10
Barnard’s
Star
Sirius B
10-4
0
Mira
Sirius A
1
-5
A0
F0
G0
Spectral Type
K0
M0
M8
+15
Absolute Magnitude
104
Stars found on the
Main Sequence
convert hydrogen
into helium.
Stars like the Sun
can do this for
many billions of
years, using the
P-P chain of
nuclear reactions
The P-P chain: converting hydrogen to helium
Surface temperature (K)
25000
106
10000
8000 6000
.
5000 4000 3000
. .
.
.
.. .
. .
. ..
.
. ..
..
.
...
.. . ....
..
. .. ..... ... .
. ..
.
... . . ... ........ .
.. .... .
.. .
. .....
......
......
.. ..
..... .
......
. .
...
. .
. ... ...
..
Deneb
-10
Rigel
Betelgeuse
Antares
Luminosity (Sun=1)
Arcturus
102
Aldebaran
Regulus
Vega
Procyon A
Altair
10-2
Pollux
Sun
Procyon B
O5 B0
+5
+10
Barnard’s
Star
Sirius B
10-4
0
Mira
Sirius A
1
-5
A0
F0
G0
Spectral Type
K0
M0
M8
+15
Absolute Magnitude
104
Stars found on the
Main Sequence
convert hydrogen
into helium.
Hotter stars burn
their hydrogen
much faster, via
the CNO Cycle
Interior of a solar-type star
Interior of a red giant star
When the fuel runs out: formation of a red giant
White dwarfs: earth-sized stellar relics
Surface temperature (K)
25000
106
10000
8000 6000
.
5000 4000 3000
. .
.
.
.. .
. .
. ..
.
. ..
..
.
...
.. . ....
..
. .. ..... ... .
. ..
.
... . . ... ........ .
.. .... .
.. .
. .....
......
......
.. ..
..... .
......
. .
...
. .
. ... ...
..
Deneb
-10
Rigel
Betelgeuse
Antares
Luminosity (Sun=1)
Arcturus
102
Aldebaran
Regulus
Vega
Procyon A
Altair
10-2
Pollux
Sun
Procyon B
O5 B0
+5
+10
Barnard’s
Star
Sirius B
10-4
0
Mira
Sirius A
1
-5
A0
F0
G0
Spectral Type
K0
M0
M8
+15
Absolute Magnitude
104
Stars on the
Main Sequence
turn hydrogen
into helium.
Blue stars are
much hotter
than the Sun,
and use up their
hydrogen in a
few million years
Interior of a very massive star
Crab Nebula: supernova of 1054
Supernova 1987A, in the
Large Magellanic Cloud
Supernovae
Putting the Iron in Irn Bru