This blog is an extended version of the script made for the first ever use of the inflatable planetarium ...oooh exciting :)
This first show is based loosely on the Life Cycle of Stars...aimed at students studying GCSE Physics and GCSE Astronomy. If the kids are younger than GCSE or below, nicer to start with Planets and Ecliptic and star signs stuff, detailed in Optional Start, leaving out more complex stuff on Neutron Stars and Black Holes.
Stellarium commands are in blue
Red notes are optional facts to add, and depend on age of audience and time.
The talk should take 20-30 mins depending on how much science/mythology you elaborate on. Suggest that it is nice to do this show condensed into 20 mins at the end of We are Astronomers… to give a 40-45minute show.
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| Me with the dome :) |
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From blue young stars to black hole death
Optional easing-in start
Do this if audience have no real
knowledge of the stars and planets - best starting point for younger kids, if
GCSE probably not needed can jump straight in at Finding North, but check!
In stellarium start with sky as it is
with sun (a for atmosphere) and ground, g. and at current time 8 .
Ask ‘Can we see any stars in the
night sky?’
Expect responses such as ‘Only the Sun, no
because it’s too bright’-
Ask ‘so why can’t we see the other stars in the
day?’ -
Get response cos our star the sun,
too bright, light bounces off atmosphere, stops us seeing the other stars.
Mention the light pollution in cities bouncing off the inner atmosphere
stopping us seeing stars even at Night!
Speed up time and see sun
moving across the sky, ask why the sun is moving?
Explain that sun is not actually
moving it’s us that is moving about on our axis and this makes the sun appear
to rise in the East and set in the West. Normal time rate Get to some
time tonight , about 9pm by speeding up, then switch to Normal time.
Turn the sun off (a) and the planets and
ecliptic on < , >.
Explain what the ecliptic is (all the
planets in our solar system are in the same plane so as we look out at them
they all seem to follow the same path on the sky, (red curved
line in stellarium) Point out the planets they should be able to see tonight.
Turn on the constellation pictures of
all the stars signs (c – constellations v – names r - art ). Explain that a constellation is a
grouping of stars made by the ancient greeks they used them to navigate and
made up stories about different constellations. You will notice that all the zodiac
constellations, ie. Star signs lie along this line called the ecliptic. These
star signs divide the ecliptic up into 12 equal zones, which is why they are 12
of them. (Leave constellations on but pictures
off! r)
From here can either start explaining
how to find North and follow show from there , or (Cut out north and Cass and Andromeda
)
Go straight into Orion and start
talking about life cycle of stars just within Orion.
Finding North
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Big Dipper to Cassiopeia
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Starting with Big dipper, which is an
asterism, part of the constellation ursa major, which means the Great Bear. And Ursa Minor, which means small bear. The lowest
too stars in the saucepan point to North Star.
It looks like a saucepan, with a
handle and a place to put your beans, counting from the 2 stars at the end of
the pan, count in a straight line about 5/6 steps (at a step distance of the
gap between those 2 stars). There you will find Polaris aka the North
star. Many people think North Star is
the brightest in the sky! It isn’t! it is only important because it is directly
above the North Pole, and stays above the north pole as the earth spins on its
axis causing all the other stars to spin around! Think about spinning top (from
Christmas cracker) the top part, which you spin around with your fingers,
doesn’t appear to move while the sides of the top are whizzing around. The
middle of the top represents the North Pole with the North Star is right above
it. Make sure they realise none of the stars actually move, and it’s us that
are moving?
(speed up time L in Stellarium so they
can see stars going around in arcs)
Mentioned Axis
of Earth ( if time mention Southern Hemisphere doesn’t have a star above south
pole :( They use Southern Cross and point to an area which is above/below the
South Pole)
Circumpolar stars -Cassopeia to Andromeda
Make sure can see both Cass and big
dipper
Ask ‘what is a constellation? ‘ Explain these are 48 constellations in
total.
Turn on constellation art press ‘r’ key
Patterns of stars in sky, imagine the ancient
Greeks without TVs very bored so used to join the stars together like a dot to
dot, Mention
that the Saucepan/Big
Dipper is an Asterism not constellation, as it is part of the great bear. Turn off
constellation art r
Circumpolar
stars
Explain that the constellations of
Cassiopeia and Andromeda and Ursa Major etc are Circumpolar constellations and
never set.
Cassiopeia
Cass looks like a W or an M for McDonalds,
find her from the Big Dipper by drawing a line through North Star. Cass is a queen
married to King Cepheus (he is in sky near by looks like a house drawn by a
child). Andromeda
is Cass’s daughter.
Andromeda
Locate Andromeda.. go along same line
from Polaris, to Cass, and thru to Andromeda.. (Search Fn-F3 for M31, and zoom
in using / in stellarium)
When in Andromeda constellation, say
it is our nearest spiral galaxy Andromeda (in local group.) Andromeda looks a
lot like our own galaxy and you can imagine if you were flying in space outside
our Milky Way it would like very similar to Andromeda.
Mention that Andromeda is actually
alot bigger than the Milky Way, has many more stars!, make sure they know the
Milky Way is our galaxy! Say that the light from Andromeda is actually blue
shifted! Ask if they know what this mean? So MW and Andromeda are actually
moving toward each other in space, attracted to each other by gravitational
forces due to their large masses, in 4.5 billion years they will collide making
a much larger galaxy.
Milky Way
(MW)
Make sure they know MW is our galaxy,
talk about the reason for the name, i.e. the ancient Greeks thought it looked
like someone had spilt milk across the sky. Spiral arms are dust and gas that
is orbiting a supermassive black hole which exists at the centre of all
galaxies. We are in Orion arm of our galaxy. (Leads into
talking about Orion, then can miss out Andromeda and Cass story if not much
time)
Can mention other satellite galaxies, LMC and SMC.
Andromeda-Cassiopeia story
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| Cassiopeia |
(only do this
story if have time!, best for Year 8 and below.)
If you have seen the recent film
Clash of the Titans you will know this story already, but you might not know
how it relates to the stars…
Put on constellation art r , Make sure
all people in story are in sky and point to them with laser
Cass Queen and Mother and daughter Andromeda
were both very beautiful but Cassiopeia committed a 'sin' in the eyes of the
Greek gods, by saying that herself and her daughter were even more beautiful
than the sea nymphs. This made Poseidon, god of the sea really mad so he struck
the water with his Trident and flooded the lands, calling up the sea monster,
Cetus, to destroy the kingdom. Cepheus her husband the King, was scared for his
kingdom so he asked an oracle how he could save the kingdom and she said
"you will you have to sacrifice your daughter to the sea monster to save
it"...
So he decided he would sacrifice his
daughter, so Andromeda was chained to a rock with the sea monster sent on her. Luckily
Perseus who was very strong and handsome decided he would save Andromeda so he
flew to her on Pegasus and said, "Hey I'll kill the monster if become my
wife" so of course she did, since he was handsome, and there was the fact
she was just about to face certain death. However, the story doesn’t end here
though, because the people of the kingdom were not happy that Perseus and
Andromeda were together, one person with a problem with this was a former lover
of Andromeda, he set 200 hundred warriors to attack the couple (and her mother
was involved in organising this, also, you can see from this story that
Andromeda parents weren’t really very nice, her mother especially evil).
Luckily Perseus had the head of the Medusa which he used to wear on his belt
(handy!) and anytime you look into the eyes of Medusa she will turn you all to
stone, so he was able to turn them all to stone by angling her head at the 200
warriors. The Gods flung Cassopeia into heavens as punishment for causing all
this to happen for being so vain. She sits on her throne the W in the
sky and as we learned earlier she is circumpolar goes from M to W she
is being banged on her head (with her skirts flying up over her with each
revolution)...And Perseus and Andromeda lived happily ever after! Turn off
constellation art r
Milky Way to Orion
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| Orion the hunter |
From Cass
through Perseus to Auriga then Orion, or Search for Orion Fn-F3 M43,
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| Orion |
The constellations we see
depend on the time of year. Because the aswell as the earth is spinning around
on its axis , which gives us day and night, the earth is moving along its orbit
around the Sun, this gives us seasons and also means we are looking into
different parts of the sky during the course of the year. The constellation
Orion is a Winter Constellation, and is very famous because of the 3 stars
which make up orions belt.
Point out 3 stars and then turn on
constellation art, explain about him being a hunter, shape of his body then
turn off.
Orions
belt
3 stars these are young blue stars, baby stars if you will. Introduce
Betelgeuse on the shoulder. Ask which stars are hottest type of stars or
coldest?
Zoom in / Search Fn-F3 M43 Orion Nebula,
Talk about stars being born out of dust and gas. In Orions sword. Star
forming region nursery. Like Orion is pregnant. Tell them about the different
colours recap, blue, young star, yellow, teenage star, red giant star dieing...
then finally death brings...large explosion...BOOM! Our Sun, is considered to be a low mass gently throw
outerlayers out in a planetary nebula, burned out core that remains is a White
Dwarf.
High mass stars like Betelgeuse which
I will talk about in a moment, end their lives by , powerful supernovae
explosions which can be as lumionous as an entire galaxy of stars! These
Supernovae throw out particles called neutrinos, and leave behind a Neutron
Star or a Black Hole. (If kids old enough mention that if
Star was
bigger than 1.4 times the Mass of sun NS if bigger than 3 times the size of sun
BH.)
Heavy elements formed inside star are
now enriching space, recycling,
new stars are born from this. We are all
made from the elements formed in stars :)*****
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This Image shows the full cycle of the stars life.
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For example the process of Fusion
combines H to He then to Oxygen then to Carbon, and us Humans are known as
Carbon based life forms.
Betelgeuse –arabic
for armpit of the central one.
This super giant star has been in
news recently because astronomers think it might blow up or go supernovae very
soon (in fact it may have already blown up). This is red star, which is cooling
down because it is coming to the end of its life. Our star the Sun is in the
stable phase of its life. If we think of the new born stars (protostars) as mainly
made of H where the process of Fusion hasn’t started. The sun has been Fusing
it H into He steadily for 4.5Billion years, this steady phase is called the
main sequence, and it will be another 4.5 billion years before it runs out of
all its H and swells up into Red giant star. When the sun ends its life it is
not big enough to cause a supernova explosion it will just leave a small star
called a white dwarf.
Betelgeuse is a supergiant red star
about 500 light years away - that means it would take the light from Betelgeuse
500 years to reach us on earth. So when astronomers are looking at B they are
actually seeing the star in the past, as it was 500 years ago. This is why it
is difficult to tell if has blown up.
Now nothing can travel as fast as light, for example the Sun is 8 light
minutes away from us. This means light from the sun takes 8 mins to reach us.
So even if for some reason the sun suddenly stopped emitting light to us, it
would be 8 minutes before we would know about it.
B is so big if you placed it into our
solar system in the place of the sun it would extend out past Mars and the
asteroid belt and into the orbit of Jupiter. The reason why it is so big that
it has run out of H and can’t fuse atoms together. This means the forces on the
star are no longer balanced which is why the outer layers start to swell
outwards and eventually it will go boom! When it does go ‘boom’ even though it
is over 500 light years away it will be very bright, we may even be able to see
it for several weeks in the daytime. However, do not fear if it does go
supernovae within our lifetime (could go bang tomorrow could be the next
million years) it won’t affect us, apart from the firework show.
For kids older than Year 9 can say
astronomers call the young blue stars, O stars these are 33,000 K, hottest, and
the coldest, M stars, red 3,700K (say degrees), compare this with the
temperature of the sun 6,000K.
Can also
explain light year, 6trillion miles! (6 with12 zeros which is
a distance equivalent to 240 million times the circumference of Earth.
Sun
When our sun becomes a red giant star
in about 8 billion years from now it will actually swell up so big it will
knock us out of orbit.
Crab
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| The Crab, and the Neutron Star at the centre |
Try not to repeat stuff, which is talked
about for Betelgeuse with the Crab Go to Taurus, NW of Orion, Search for Fn
F3 M1 / zoom in then back out\, on one of horns of the Bull, Taurus.
Link with
B if talked about it, explain that this is the Crab nebula, star that went
supernovae in 1054 and the Chinese saw it first. Now even though it is 6,500
lyrs away (about a 100 times further than B), it was brightest thing in the sky
except for moon, so this just shows you how bright these explosions are when
massive stars die! It got its name, the Crab, because it
has these extended filaments make it look like a crab? see if you
agree in photo later...if doing photos.
The Crab Nebula, has exploded and
left a very dense type of star at its centre, called a Neutron star. These
stars are extremely dense, Ask if they know what dense means?
Give example that a NS the mass of
our sun would be the size of a city like Southampton.
Or another way of thinking of it, one
tablespoon of material from a NS would have the same weight as Everest. Neutron
star held up by neutrons only, everything else has been squashed out by the
strong gravitational forces acting on the star, which act due to its great
mass. In order to escape from the surface of a NS you would have to travel at
1/2 the speed of light, which is equivalent to about 300Million miles an hour! Pulsars are an
example of a spinning neutron star, which is spinning due to the conservation
of the angular momentum of the original star.
Make sure zoomed out \ and can see all
of Taurus….
Pleiades are the
most famous star cluster in the night of sky and the Greeks said this cluster
was like the ‘fleas on the back of Taurus’
These are bright white/blue stars
called then seven sisters; you may have seen these on the badge of the Car,
Subaru. The native Indians used these as an ancient eye test. If you could see
maybe 6-9 by the naked eye you could become a hunter, but if you can only se
about 3 or 4 you had to be a farmer. This doesn’t apply if you are looking from
Soton because of light pollution from the city you will be lucky to see Taurus,
never mind the Pleiades. This cluster actually has hundreds of stars, which are
gravitationally bound to each other. Zoom in to see Pleiades / by searching
for it. FnF3
Can zoom back out and speed up time L,
to see Orion chasing Taurus across sky he is a hunter after all.
Sirius
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| Orion's belt - follow to Sirius |
Line drawn from Orion’s belt to Sirius
, point out with laser , Talking about different stars, leads on to asking if ‘Anyone know what the brightest star in the sky is?’
Sirius, which is Greek for ‘glowing or scorching’ is an example of a massive young white star and also that this is the brightest star in the sky and is on the eye
Zoom in to /collar of Orion’s dog.
Ask ‘why is it so bright?’-
Hopefully they will say because it’s close by, yes it is only 8.7 light years away which when you compare it with Betelgeuse its very close, another reason why it is so bright is because it is actually 2 stars in what astronomers call a binary system, the one star is size of sun, and other is twice size of sun.
Black hole M87
Navigate from Crab in Taurus to Virgo
or, Search Fn-F3 M87 (back to ursa major/big dipper, thru Bootes, and then
Virgo is there) Zoom / see elliptical galaxy
M87 is an example of a black hole.
Black holes are either formed at the end of the life of a star and these small
black holes can exist within our galaxy, the MW and have masses about 10 times
that of the sun, other supermassive black holes like M87 are 1000, million
times that of the sun!! These are thought to be formed in the beginning of the
Universe when large galaxies were merging together (M87 is at the
centre of an elliptical galaxy Jet goes out 5,000 light years, which is
astounding when you think that about as far as we are from the Crab Nebula.). For a collapsed or dead
star with a mass of about 8 suns where there is
such extreme gravity between the remaining mass, that even the neutrons can
hold up the star, and these neutrons get squashed out, making a hole in space
time. Ask ‘What speed do you need to travel to
escape from a black hole?’- Hopefully answer is speed of light, which is
equivalent to a speed of 600 million miles an hour! Go onto explain this is why
we can’t see black holes. Astronomers (as shown in We are astronomers) use the EM
Spectrum to look at the light from stars, be it the gamma rays, X-rays or
visible light that we can detect with our eyes. Black
holes suck in all those different types of light, so the only way astronomers
know they are these is by measuring the speed of objects which are orbiting
them, or looking for high energy X-rays being given off by material falling
into the black hole.
Compare with our Sun as a BH.
If you replaced our own Sun with a
black hole of the same mass, the planets etc would all still orbit around in
the same way, we wouldn’t get sucked in, the only time you get sucked in is
when you get too close.
Now it might shock you to know that our
Solar System is orbiting in our galaxy around a
Supermassive
black hole
These supermassive BH were predicted
by Einstein’s theory of general relativity. They exist at the centre of all
galaxies, a million times that of sun. The BH in our MW is actually 4
million times mass of sun! Ask ‘how do you think astronomers know
the mass? Cos they can’t just weigh it with a scales?’ Using Keplers Third Law,
equation which relates the speed of orbits stars to the mass of the thing they
are orbiting, exactly how we measure the mass of the Sun.
Astronomer measured high speeds of
stars orbiting around an object known as Sagittarius A* which is at the centre
of our galaxy the MW. Can zoom / into Sagittarius A*/ search for
Sagittarius using Fn-F3. Can’t see much there, turn off the constellations , c
and search fnF3 for M25 this is a near by cluster of stars explain that at the centre of our galaxy astronomers measure the speeds
and orbits of stars just like that’s how they know there is a supermassive
black hole there!
Ending thought
about black holes.
Most people think of black holes as
monsters but Astronomers now think they play a large part in the early
formation of galaxies. As we learn more about how galaxies were formed in early
universe it seems that the BH at the centre plays a large part in forming
galaxies, remember that the jet from the centre of the galaxy can reach into
other galaxies, these jets of particles might start star formation to occur in
galaxies where it might otherwise not have occurred. This means that without
our blackholes the universe might of not formed galaxies. And without galaxies
there wouldn’t be stars, without the stars, no solar systems of planets and
with out planets, no humans, so black holes may not something to be afraid of.
Pictures to show at end of show
First explain Messier looking for his fuzzy blobs.....why alot of items we talked about have M numbers, i.e. M1 and M87.
Andromeda & Milky Way- spiral galaxy, milky way from earth see LMC and SMC
Planetary Nebula - what will happen to Earth.
Supernovae! Crab with NS at centre, nice chandra Xray image
video by nasa at http://en.wikipedia.org/wiki/Crab_Nebula
can we warp this and show them at the end?
Red giant (Betelgeuse ?)
M87, cool pics http://en.wikipedia.org/wiki/Messier_87
Pleides
White dwarf
Orion - different coloured stars.
