Download TMSP Stellar Evolution & Life

STELLAR EVOLUTION
AND LIFE!
Linda Khandro, MAT
www.lindakhandro.com
Edmonds College Creative Retirement Institute
Everett Astronomical Society
Shoreline College Summer College
Table Mtn. Star Party
2009-2010
PART THE FIRST:
STELLAR
EVOLUTION…
“BIRTH, LIFE, AND
DEATHS” OF
STARS
PART THE SECOND:
…AND LIFE.
WHAT DO STARS
HAVE TO DO
WITH LIFE
PART THE FIRST:
STELLAR
EVOLUTION…
“BIRTH, LIFE, AND
DEATHS” OF
STARS
Our Galaxy, the Milky Way:
where new stars
are being born
and old stars are
dying
in the
spiral arms.
The Andromeda Galaxy:
our nearest galactic
neighbour;
stars birthing
stars dying
~2.5 million
light years away.
Rosette Nebula:
where new stars
are being born,
in the constellation
Monoceros.
Betelgeuse:
a dying, red giant
star,
in the constellation
Orion
Eta Carinae:
remnants of
a dying star
in the
constellation
Carinae.
Crab Nebula:
remnant of
supernova
1054 AD,
in the
constellation
Taurus.
INTRODUCTION TO STARS
important terms & definitions
•BIRTH : Not from a “parent”, but from the
gravitational collapse of a nebula.
•NEBULA: cloud of gas and dust, itself a product
of stellar deaths, including supernovae.
•SUPERNOVAE: several types, either from dying
binary stars, or deaths of single, massive stars at
least 8x sun’s mass (these are the supernovae of
interest to us here).
INTRODUCTION TO STARS (2)
•LIFE SPAN: longevity of a star depends entirely on its mass
•Mass like our Sun = few billion years (Sun is 5 b.y. now, we
expect 5 b.y. more)
•Mass greater than Sun = less time than Sun to reach Red Giant
stage
•RED GIANT STAGE: star has consumed its core fuel, expands &
contracts at the same time (!), grows larger, brighter, and cooler as
outer layers expand outward to form Planetary Nebula, and core
contracts to form a White Dwarf.
•PLANETARY NEBULA: outer part of the end stage of sun-like
star, outer regions continuing to cool and expand.
•WHITE DWARF: core of sun-like star collapses, no fusion, no heat
production, ultimately cools to “black dwarf”.
INTRODUCTION TO STARS (3)
•BRIGHTNESS: how bright a star appears to our eyes and
instruments, function of distance as well as intrinsic
brightness or luminosity.
•LUMINOSITY: how much energy the star is actually
generating is a function of its mass (or size) and
temperature (the big vs small bonfire analogy).
•TEMPERATURE: stars vary in temperature; more
massive stars take a shorter time to burn core fuel and are
hotter while doing do; less massive stars have less fuel,
take longer, are cooler. Colour reflects temperature.
INTRODUCTION TO STARS (4)
•COLOUR: blue-white-yellow-orange and reddish
coloured stars indicate temperatures from the
hottest to the coolest. Colours, temperatures, and
masses of stars are all plotted on an H&R diagram.
Most stars we see are plotted on a graph on the
H&R called the Main Sequence. Red Giants and
White Dwarfs are no longer Main Sequence stars!
•MAIN SEQUENCE STAGE: longest, most stable
time of a stars ‘life’, when Hydrogen (H) fuses to
form Helium (He) in the star’s core.
STELLAR CLASSIFICATION
SCHEME (general version)
OBAFGK M
Left to Right:
Temperatures: hottest to coolest
General Colours:
blue,white,yellow,orange,red
Oh Be A Fine Girl/Guy Kiss Me!
MESSIER OBJECTS
http://apod.nasa.gov/apod/messier.html
MORE STARS FORM AS BINARIES
OR TRINARIES THAN AS SINGLE
STARS, LIKE OUR SUN
AS FAR AS WE KNOW, OUR SUN HAS
NO COMPANION STAR
http://apod.nasa.gov/apod/ap050830.html
COMPARING SIZES OF THE SUN
AND PLANETS IN OUR SOLAR
SYSTEM
STELLAR
BIRTH
OUR SUN AND SOLAR SYSTEM
FORMATION VIDEO
http://www.youtube.com/watch?v=q5lc
KLUvLzQ&feature=related
COMPARING OUR SUN TO STARS OF
DIFFERENT TYPES, AGES, AND SIZES
SIRIUS (Canis Major):
Younger than Sun, >2x mass, binary, brightest in
sky, >8 LY, 25x luminosity, A class
http://en.wikipedia.org/wiki/Sirius
POLLUX (Gemini):
Younger than sun, <2x mass, >34 LY, 32x
luminosity, K class
http://en.wikipedia.org/wiki/Pollux_%28star%29
ARCTURUS (Bootes):
Age of sun, 3.5x mass, 37 LY, 210x luminosity, K
class
http://en.wikipedia.org/wiki/Arcturus
BETELGUESE (Orion):
Younger than Sun (few my), >18x mass, >640 LY, 105,000x
luminosity, M class
http://en.wikipedia.org/wiki/Betelgeuse
RIGEL (Orion):
Younger than Sun (8 my), trinary system, 17x mass, 800 LY,
40,000x luminosity, B class
http://en.wikipedia.org/wiki/Rigel
ALDEBARAN (Taurus):
Binary, <2x mass, 65 LY, 150x luminosity, K class
http://en.wikipedia.org/wiki/Aldebaran
ANTARES (Scorpio):
Binary, 15-18x mass, 600 LY, 10,000x luminosity, M class
http://en.wikipedia.org/wiki/Antares
STAR BIRTH REGIONS FROM
ASTRONOMY PICTURE OF THE DAY
http://apod.nasa.gov/apod/lib/aptree.html:
THE PLEIDES OPEN STAR CLUSTER
http://apod.nasa.gov/apod/ap060109.html
M46 AND M47 (IN PUPPIS)
http://apod.nasa.gov/apod/ap050804.html
EAGLE NEBULA (M16 IN SAGITTARIUS)
http://apod.nasa.gov/apod/ap050424.html
ORION NEBULA (M42 IN ORION)
http://apod.nasa.gov/apod/ap040713.html
STAR FORMATION VIDEO:
12 BILLION YEARS IN 6
MINUTES!
http://www.youtube.com/watch?v=mZ
L7VBmeFxY&NR=1&feature=fvwp
LIFE CYCLE OF OUR STAR
http://en.wikipedia.org/wiki/Stellar_evolution
http://www.astronomytoday.com/cosmology/evol.html
STELLAR
LIVES
How hot, large, and
long-lived will a star be
once it enters its main
sequence stage?
That all depends on its
mass…
•Stars range in mass from about 0.08 to
100 solar masses, but most are similar to
or less than that of the Sun and masses
greater than 10 solar masses are rare.
•However, the range of densities is very
great. Red Giants, such as Betelgeuse, are
less dense than the air we breathe,
whereas a sugar- lump size of white
dwarf material would, on Earth, weigh
in excess of 1 ton.
Avg. Mass
Spectral class Avg. Lum
Avg. Diameter
MS lifetime
40 x Sol
O5
500 000 x Sol
18 x Sol
1 million years
17 x Sol
B0
20 000 x Sol
7.6 x Sol
10 million years
7 x Sol
B5
800 x Sol
4.0 x Sol
100 million years
3.6 x Sol
A0
80 x Sol
2.6 x Sol
500 million years
2.2 x Sol
A5
20 x Sol
1.8 x Sol
1000 million years
1.0 x Sol
G2 (sun)
1.0 x Sol
1.00 x Sol
12 000 million years
0.5 x Sol
M0
0.03 x Sol
0.63 x Sol
75 000 million years
0.2 x Sol
M5
0.008 x Sol
0.32 x Sol
200 000 million years
Simplified illustration of the evolution of a star with the mass of the Sun
•The star forms from a collapsing nebula, or cloud of gas (1)
•then undergoes a contraction period as a protostar (2)
•before joining the main sequence (3).
•Once the Hydrogen at the core is consumed it expands into a red giant (4)
•then sheds its envelope into a planetary nebula and degenerates into a white dwarf
(5).
•90% of stars fall plot on the Main Sequence
of the H&R diagram (note that this is not an
evolutionary sequence! A typical evolutionary
sequence is shown by the red curve).
•Hotter, massive Blue Giant stars are plotted
in the upper left of the H&R (not MS).
•Cooler more massive Red Giant stars are in
upper right.
•Hot but smaller-size White Dwarfs are in
lower left.
Main sequence/hydrogen to helium burning
stage: the longest and most stable time in a
star’s “life”.
RED GIANT STAGE FORMATION
(about 10% of MS lifetime):
1.H to Helium fusion slows as H is depleted, thus
2.Fusion pressure is reduced, thus
3.Gravity collapses core, but
4.Gravity causes heat increase to the point where
5.Renewed H fusion can occur around core, which
produces
6.Renewed fusion pressure, which expands
7.Outer envelope which cools with distance from
hot core
8.Star is more luminous (brighter) and larger
(cooler and reddish)
Post Main
Sequence
Star (Red
Giant):
G=gravity
P=fusion
pressure
L=luminosity
STELLAR
DEATHS
DEATH OF STARS ABOUT ONE SOLAR
MASS
FROM RED GIANT TO…
WHITE DWARF AND PLANETARY
NEBULA
http://apod.nasa.gov/apod/ap030614.html
http://apod.nasa.gov/apod/ap050612.html
DEATH OF STARS
GREATER THAN ABOUT 25 ORIGINAL
SOLAR MASSES
These massive stars may implode then
explode as Supernovae (Type II)
http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernovae.html
http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html
SUPERNOVA FORMATION
The Red Giant-forming sequence of one element
fusing to form another element, at successively
higher temperatures and shorter times can result in
a supernova as this process can repeat over and
over again as:
1.Collapse and increased core temperature causes
He to fuse to form Carbon…
2.C fuses to form next element in a…
3.Series of element formations ending in…
4.Silicon fusing to form Fe…end of the road…Fe
will not fuse…
The
onion-like
layers of a
massive,
evolved
star just
before
core
collapse.
(Not to
scale.)
Eta Carinae…
a dying star
Eta Carinae
http://apod.
nasa.gov/ap
od/ap980816
.html
Crab Nebula…
remnant of
supernova
1054 AD
PART THE SECOND:
…AND LIFE.
WHAT DO STARS
HAVE TO DO
WITH LIFE
First of all, how do we
know what we know about
stars???
SPECTROSCOPY
The study of light (spectra)
“Spectroscopy pertains to the dispersion
of an object's light into its component
colors (i.e. energies). By performing this
dissection and analysis of an object's
light, astronomers can infer the physical
properties of that object (such as
temperature, mass, luminosity and
composition)”.
http://loke.as.arizona.edu/~ckulesa/camp/spectroscopy_intro.html
That’s the short
version!
And what we are
trying to do here is see
how the composition of
stars relates to the
composition of life…
So we’ll begin here…
http://en.wikipedia.org/wiki/File:Light_dispersion_conceptual_waves.gif
…to show what happens when white
light is shone through a prism
(later a spectroscope)
Put on the glasses you have in front of
you and look at various light sources in
the room!
Now we’ll look at a chart
of the entire spectrum of
electromagnetic radiation
of which visible light is just
one narrow band…
…the wall chart please!
There are different sources of light
(or electromagnetic radiation) and
different ways to look at those
sources through a spectroscope (more
complex but similar to a prism).
We’ll keep it simple and just deal
with visible light.
(in each case, a unique type of
spectrum is created)
1. Sources of light:
a. Hot solid (i.e. light bulb)
or hot, dense gas (i.e.
surface of a star)
b. Cooler or less dense gas
(i.e. atmosphere of a star)
2. Ways to look at a light source through a
spectroscope (and the spectrum produced):
a. Hot solid or hot, dense gas:
i. looking directly at the light source
(produces a continuous spectrum, like a
rainbow)
ii. looking at the source through an
intervening cloud of cooler or less dense gas
(produces a dark line against a continuous
spectrum; this is called an absorption
spectrum)
b. Cooler or less dense gas
i. looking directly at the light source
(produces a bright coloured line against a black
background; this is called an emission
spectrum)
How does this happen?
•Each of the absorption and emission spectra are
produced by specific energies (wavelengths) of light
interacting with the atoms that make up the
elements of matter in the cool or less dense gas.
•The gas can be any element heated to a gaseous
state.
•The end result is that each element of matter has
its own unique spectrum that can be seen as either
a bright (emission) or dark (absorption) line,
depending on how it is viewed.
•And since this can be done (and has been done) in
laboratories with elements heated to gaseous states,
we now have a catalog of elemental spectra.
•Using this catalog, we now look at stars through a
spectroscope and see what they’re made of…
…the very same elements of which we are made!
And since they came before we did in the history of
the universe, we are made of star stuff!
How did that star stuff turn into life?
Go back to the beginning to see how stars
form…from collapsing nebular clouds, which in
turn, are produced by the expanding outer layers of
sun-size stars, and the exploded remnants of
supernovae!
The grandest recycling program in the Universe!
The elements of life, oxygen, hydrogen,
carbon, nitrogen and more:
http://www.seafriends.org.nz/oceano/abund.htm
http://www.daviddarling.info/encyclopedia/E/elbio.html
http://www.lpi.usra.edu/meetings/abscicon2010/pdf/5547.pdf
And take a look again at the onion-like
layers of a massive star about to “go”
supernova…
The
onion-like
layers of a
massive,
evolved
star just
before
core
collapse.
(Not to
scale.)
With one important
intermediate step
yet to be discussed…
…from stars to solar
systems to planets to life…
OUR SUN AND SOLAR
SYSTEM FORMATION VIDEO
http://www.youtube.com/watch?v
=q5lcKLUvLzQ&feature=related