In the UK, for GCSE science, you need to know the life cycles of stars and understand the processes...
120
-
Upload
edith-hawkins -
Category
Documents
-
view
213 -
download
0
Transcript of In the UK, for GCSE science, you need to know the life cycles of stars and understand the processes...
In the UK, for GCSE science, you need to know the life cycles of stars and understand the processes behind them in terms of energy and forces.
You can find out more about the science you are going to study today, from the scientists that help find it out, at the Space@School website: www.neatherd.org/astronomy
Linked SOS website challenges and their scientists are highlighted in this resource
In the night sky there are thousands of stars
But one of them is 276,000 times closer than any of the others
Our Star, The Sun
Because it is so much closer than all of the other stars, we can find out a lot about stars by studying the Sun.
The following three images were taken by school
children in the UK using a specially filtered telescope.
They give an idea of the size and energy output of
our star.
The diameter of the Sun is 109 times greater than the
Earth
Events on the Sun dwarf the size of our planet.
How many Earths high is this solar prominence?
On the 8th June 2004 the orbit of Venus took the planet between the Earth and the Sun. Venus is far closer to us than the Sun. If the planet was at the same distance as our star it would look less than a quarter of its diameter here.
Find out about the sizes of Solar event with ESA scientist Danielle Bewsher
SOS website challenge
The following movies were taken using spacecraft solar observatories
Magnetic loops of glowing plasma arc into space above the Sun. You could fit a stack of ten Earths inside this arc.
ACE observatory in polar orbit
Find out about a magnetic mystery in the Sun with ESA scientist Jack Ireland
SOS website challenge
The Magnetic loops can eject vast quantities of material from the Sun
SOHO in solar orbit
SOHO in solar orbit
The Sun takes about a month to revolve on its axis. Sometimes it blasts huge quantities of its atmosphere into space. If this hits our planet it interacts with the Earth’s magnetic field which can have disastrous effects on power supplies and electronic equipment. The SOHO space observatory can give us an early warning of one of these magnetic storms.
Find out about using the SOHO space observatory to study explosions on the
Sun with NASA scientists Peter Gallagher, James McAteer & Ryan
Milligan
SOS website challenge
We need to find the answer to these questions
• Where does the Sun get all this energy from?
• What is the origin of the Sun and other stars?
• Will our star and other stars last for ever?
During the rest of this presentation you need to make
notes and diagrams that will enable you to make an illustrated flow diagram
showing the life cycle of stars
Many of the following images were taken by the European
Space Agency/NASA Hubble Space Telescope
Where do stars come from?
• The raw material that makes up stars comes from the interstellar medium
• Interstellar space is composed of a thin gas laced with microscopic dust particles.
• A place where the gas and dust clumps into clouds is called a nebula.
The nebulae are 70% hydrogen and 30% helium by mass. The amount of other elements is less than1%.
At the end of their life, giant stars die in enormous explosions than send out shockwaves into the interstellar clouds
A shockwave from an exploding star rips through the rarefied gas and dust of a nebula.
The shockwaves make the clouds collapse.
What force do you think makes them collapse?
GRAVITY!
Spiral galaxies like our own are filled with interstellar dust and gas. The pink glow is caused by hydrogen excited by the radiation from young stars.
Colliding galaxies also make interstellar clouds collapse and detonate star formation in their arms
Such is the distance between stars, that although each galaxy can contain hundreds of billions of star, a head on collision between galaxies will rarely result in a single collision of stars!
So how do the galaxies have an effect on each other?
GRAVITY!
Find out more about star life cycles in galaxies with ESA scientist Jesus Maiz
SOS website challenge
The Eagle Nebula: a
vast region of star
formation.
So, how big is it?
The white circle shows the relative size of our entire solar system
The glow is caused by young stars
Scientists believe that the pressure and temperature in the centre of the collapsing cloud forms a protostar.
How do they know this?
Let’s look at the evidence
The Orion nebula is a vast cloud of gas and dust 1500 light years from Earth. This image was taken through a small amateur telescope using a digital camera.
The following images were taken with the Hubble Space Telescope using filters that only let through wavelengths given out by the glowing atoms of particular elements.
Imaged in light given out by excited Hydrogen atoms
Imaged in light given out by excited Oxygen atoms
Imaged in light given out by excited Nitrogen atoms
Click to combine images
Click to combine images
Combined
Can you see where stars are forming?
These globules of dense nebula are called proplyds.
Could they be hiding protostars inside
them?
Hubble Space Telescope can sense a wavelength that is
given out by hot things and can
penetrate the gas and dust –
Infrared
Infrared
This reveals many more stars and hotspots hidden inside the dust and gas.
Are any of them inside proplyds?
Click to combine images
Click to combine images
H+O+N+IRWhat does each proplyd have at its centre.
H+O+N+IREach proplyd has a star or hot protostar at its centre.
H+O+N+IR
Find out more about star birth and make your own unique portrait of the Orion nebula with ESA scientist Massimo Robberto
SOS website challenge
From evidence like this, we know that forces build inside the protostar until they are great enough to fuse hydrogen atoms together into helium.
In this conversion a tiny amount of mass is turned into a large amount of energy.
For a star of the Sun’s size, 5 million tonnes start to be converted into energy every second. The protostar detonates into a star.
Luckily the Sun has a mass of 2 billion billion billion tonnes. So there is enough to last for a very long time. The Sun has been shining for about 5 billion years and in all that time it has only lost 1% of its mass.
• Our Sun serves as the primary evidence that stars are not permanent.– Nuclear Fuel in the Sun cannot last
forever.– Our Sun is similar to the stars we see
in the night sky.
Understanding how stars evolve requires both observation and
ideas from physics.
The new star erodes the surrounding proplyd with its radiation. Eventually the area clears, revealing the star and a surrounding disk that can form a planetary system.
Find out how we know about planet formation with ESA scientist Inga Kamp
SOS website challenge
Inside, a structure forms and the star settles down to fuse its hydrogen.
Find out how we know the internal structure of the Sun with ESA scientist Bernhard Fleck
SOS website challenge
The force of gravity crushing the star is balanced by the outward force created by fusion in its core.
The force of gravity crushing the star is balanced by the outward force of the radiant pressure created by fusion in its core.
Draw a copy of this diagram and label the forces
Draw a copy of this diagram and label the forces
Gravity GravityPressure of fusion
Pressure of fusion
Gra
vity
Gravity
Pressure
of fusion
Pre
ssur
e o
f fu
sion
How long do stars live for?
Bigger stars have more fuel, so they live longer?
What do you think?
Discuss this and take a vote
Solar Masses Surface Temp (0C)
Lifetime (million yrs)
25 35000 3
15 30000 15
3 11000 500
1.5 7000 3000
1 6000 10000
0.75 5000 15000
0.5 4000 200000
What is the pattern between mass and lifetime?
What explanation can you find for this in the table?
Solar Masses Surface Temp (0C)
Lifetime (million yrs)
25 35000 3
15 30000 15
3 11000 500
1.5 7000 3000
1 6000 10000
0.75 5000 15000
0.5 4000 200000
The bigger the star, the shorter its lifetime.
Reason - big stars are hotter, showing they are burning their fuel quicker. With more mass, comes more gravity, needing more radiant energy to balance the star. So the bigger a star, the faster it burns its fuel and hence the shorter its lifespan.
Map the temperature of the Sun with Cambridge University SOHO researcher Helen Mason.
SOS website challenge
For Stars up to 1.5 times the size of our Sun:
When the hydrogen is used up, the star’s core shrinks and starts to fuse
helium. The intense radiation released puffs up the outer layers,
which cool and glow red. The star is now a Red Giant
The Sun is half way through its hydrogen burning life. How long
until it runs out of hydrogen?
1 solar mass stars burn hydrogen for 10,000,000,000 years
So the Sun has 5,000,000,000 years of hydrogen burning left
Orbits of
Mars Earth
The Sun as a Red Giant in 5,000,000,000 years time
Red giant stars in Auriga
The core of the red giant now fuses helium into bigger atoms but it eventually completely runs out of fuel to fuse
Dormant hydrogen fusing shell
Carbon-oxygen core
Helium-fusing shell
300 million km
With no fusion energy to keep the core inflated, it collapses for one last time. The carbon is crushed into a diamond the size of the Earth.
The outer layers of the Red Giant are shed into space as giant gas and dust shells. They are illuminated by the remaining tiny White Dwarf star.
Astronomers thought these dim clouds looked a bit like planets so they called them planetary nebulae.
With modern telescopes like the Hubble Space Telescope, astronomers have shown planetary nebulae to be some of the most beautiful objects in the Universe.
What do you thinks these planetary nebulae are called?
Astronomers call this the Eskimo Nebula
Astronomers call this the Glowing Eye Nebula
Astronomers call this the Hour Glass Nebula
Astronomers call this the Cat’s Eye Nebula
Astronomers call this the Red Spider Nebula
Astronomers call this the Eye Nebula
Astronomers have not given this nebula a name yet
Find out how we know about the structure of planetary nebulae with NASA scientists Frank Summers and Lisa Fratarre
SOS website challenge
Fuel runs out and core shrinks into a White dwarf and out layers form a
planetary nebula
Hydrogen runs out and the core shrinks and
starts Helium burning. The star swells into a Red Giant.
The star burns Hydrogen.
The life of a star up to 1.5 solar
massesclick to start
The Protostar forms in a collapsingproplyd of a nebula
An ancient cluster of over a million stars reveals some remaining red giants and many white dwarfs
Stars of more than 1.5 Solar masses have a very different
fate
Betelgeuse
Bellatrix
MintakaAlnilam
Alnitak
RigelSaiph
They burn fiercely as Blue Giant stars and use their fuel up quickly
The blue giant star Bellatrix, in the constellation Orion, is coming to the end of its hydrogen fuel
Orion Nebula
When the star runs out of hydrogen and starts to burn
Helium, it swells into an enormous red star – a Red Super Giant
Betelgeuse in the constellation is a red super giant, here imaged by HST
Betelgeuse dwarfs all other stars
What sort of star do you think Sirius B is?
A white dwarf
When a Red Super Giant runs out of Helium fuel it has
enough heat and pressure in its core to fuse Oxygen and Carbon to make even bigger
atoms
The core of the red giant becomes an onion-like structure with an iron core.
Hydrogen
Carbon
Helium
700 million km
Oxygen
Neon
Silicon
Iron core
Eventually the star creates a core of iron
As the fuel runs out, the core shrinks and gets hot enough
to fuse iron.
You don’t want to be in that part of the Universe when a
Red Super Giant starts to fuse iron!
As the star fused hydrogen, helium, carbon and oxygen it got energy to keep itself supported
against the crushing force of gravity.
Unlike the fusion of smaller atoms, when iron fuses it sucks in energy. The giant star is millions of years
old but it now collapses in seconds.
Billions of tons of star hurtle into the core and then bounce back out
in the biggest explosion in the Universe.
The energy released outshines the entire galaxy the star is in – up to
300,000,000,000 stars!
One star in a galaxy of billions fades after it explodes as a supernova.
At the time of the explosion it would have been brighter than the entire galaxy.
One star in a galaxy of billions fades after it explodes as a supernova. At the time of the explosion it would have been brighter than the entire galaxy.
Find out about the work of supernova hunter and Arsenal supporter Stephen Smartt of Queens University Belfast
SOS website challenge
The Tycho supernova occurred in 1572 but is still a rapidly expanding, seething explosion wiping out a sizeable part of its local universe. The blue shell is the distance travelled by intense x rays at the speed of light, heating interstellar material to 20 million degrees Celsius. The explosion is at least 800 light years across.
You would only know it was coming when it hit you.
Nothing can travel faster than light but sometimes it appears to.
Find out about this mystery with ESA scientist Nino Panagea.
SOS website challenge
What remains from the explosion depends on the
size of the original star
• 1.5 – 3 solar masses form one giant, 12 mile diameter atomic nucleus composed only of neutrons (all of the protons and electrons have been squeezed together to form neutrons).
• This is a neutron star. The force of its tremendous gravity is balanced by the repulsion of the neutrons.
What remains from the explosion depends on the
size of the original star
• 3+ solar masses and there is no force greater than the star’s gravity.
• The star collapse never stops, it disappears leaving only it’s mass to create a gravity field.
• Nothing goes fast enough to escape, not even light. This is a black hole.
A rotating neutron star (pulsar) is at the heart of the crab nebula supernova corpse
The gravity near to a black hole is so strong that even light does not go fast enough to
get away
Black holes are made up of two features
A singularity – all their mass is squeezed into a point
An event horizon – the outer edge where the force of gravity is great enough to stop light escaping. The event horizon of the smallest black holes created by supernovae should be
about 12km across.
But black holes will eat anything, gas, dust, stars,
even the centre of galaxies.
As material spirals into a black hole, it heats up and
blasts radiation out into space before it disappears for
ever.
A simulated picture of a black hole with a disk of matter spiralling inwards
What would happen if you fell into a black hole?
The differences in gravity between your feet and your head would stretch you
out like spaghetti
Do you have a complete diagram showing the life
cycles of stars?• It should show what stars form
from• What triggers star formation• The different fates of different
mass stars• How some star material is recycled
This is what your diagram should look like
CreditsWritten by Michael Cripps, Neatherd High School Norfolk UK
Website by Michael Cripps and Graham Colman of Taverham High School, Norfolk UK
Images by Michael Cripps, Neatherd High School Students, ESA and NASA
Project sponsored by the UK Particle Physics and Astronomy Research Council, the European Space Agency and Norfolk Education Business Exchange
Technical assistance by the scientists, engineers and educationalists of the European Space Agency and NASA at the Space Telescope Science Institute, Goddard Space Flight Centre and other institutions in the UK.
Special thanks to Helen Mason at Cambridge University and Dennis Christopher at NASA, GSFC.
This resource and its content may be used freely for non commercial educational purposes.
