P1.3 Flashcards
What does the solar system loom like?
can see some planets with naked eye- look like stars but different
planets orbit around stars and often have smaller moons close to them and orbiting around them
planets vary in size - mercury smallest and Jupiter biggest
Neptune furthest from sun
manned spacecraft can reach moon in 3days and potentially Mars in 9 months
Neptune would take at least 12 years
What is a galaxy?
sun in milky way galaxy
collection of billions of stars - distance between them is hundreds of times greater than distance between planets in solar system
billions of galaxies make up universe
distance between galaxies millions of times greater than distance between stars in a galaxy
What is SETI?
Search for Extra Terrestrial Intelligence
scientists looking for narrow bands of radio wavelengths coming to earth from space and looking for meaningful signals in ‘noise’ - signals could have come from a transmitter and noise from other things like giant stars
get help from public as takes a long time to analyse - can download screensaver that analyses radio waves
haven’t found anything in 50 years but now looking for possible laser signals in space
How can robots and probes collect data and samples?
spacecraft carrying probes sent to investigate planets and moons in solar system - probes carry instruments that continuously record data on conditions like temperature. data sent back to Earth on microwave or radio signals
robots can take photos and collect soil and rock samples to analyse
scientists still have to work out what data means
What are some examples of SETI work?
1976 Mars Viking landers - took soil samples with robotic arm and carried out experiments on soil to see if any
signs of life. data sent back to Earth using radio signals
also look at comets and asteroids as well as planets
2003 Hayabusa spacecraft sent to collect dust samples
How do scientists look for signs of life?
Earth based telescopes
other remote-sensing techniques
do these before spending money on sending robots/people closer
search for planets with suitable conditions for life
too expensive and impractical beyond solar system as distances too large
What are some of the problems with using telescopes?
if trying to detect light the Earth’s atmosphere gets in the way
light pollution makes it hard to pick out dim objects
air pollution can reflect and absorb light coming from space
What can be done to solve problems with using telescopes?
for best possible view telescopes should be put on top of a mountain and away from cities
to avoid atmosphere problem, put telescope in space - enables you to see objects a lot fainter than can be seen unaided from Earth
How are optical telescopes useful?
earliest telescopes
detect visible light though many objects not detectable this way
used to look at objects close by and in other galaxies
e.g cygnus A is a nearby galaxy - through optical telescope, seen as small blob surrounded by stars
How are Radio telescopes useful?
responsible for discovery of CMB radiation, helped scientists learn about origins of universe
e.g cygnus A seen as two radio jets moving away fro centre of galaxy in opposite directions - creates two massive ‘lobes’ of hot radiation
How are X-Ray telescopes useful?
good way of seeing violent. high temperature events in space e.g exploding stars
How have telescopes improved?
bigger telescopes - better resolution, gather more light - can see things we couldn’t before as they were too faint
improved magnification - can look further into space,more galaxies discovered
important as scientists can learn more about their life cycle
e.g pictures taken by Hubble Space Telescope show galaxies at life stages - used so scientists can learn more about how galaxies formed and evolved
Why are computers used alongside modern telescopes?
computers create clearer and sharper images, makes it easy to capture pictures for analysis
makes it possible to collect and store huge amounts of data 24/7 without relying on humans
make it quicker and easier to analyse data
What is a spectrometer and how is it used?
a tool used to analyse light given out by stars and galaxies
it works by a telescope directing a beam of light into it through a slit - this diffracts light and splits it up into a spectrum
What is an absorption spectra?
How can it be used?
light spectra from stars and galaxies contain dark lines caused by light at wavelengths being absorbed
e.g by elements in stars atmosphere
it can be used to work out what stars and galaxies are made of as each element has it’s own
some have bright lines (emission) - these are caused by extra light being emitted at wavelengths
spectra for galaxies further away appear more red than they should
How do you make a spectrometer using a CD?
make 1mm wide slit on one end of a box - where light comes through
make slit for CD at 45 degree angle on side of box
make a hole to look through by cutting a slot about 2cm by 6cm
put CD in box with underside (rainbow side) is facing where you’ll look through
hold up the box so it lets in light from the source through the slit
you should be able to see a visible spectra
different light sources will show different looking spectra
What might you see through a spectrometer?
continuous spectrum - no light absorbed so no dark lines
bright lines - show wavelengths of light emitted
dark lines - show wavelengths that weren’t emitted
What is the main life cycle of all stars?
initially form nebulas- clouds of dust and gas
force of gravity makes the dust and gas spiral together. gravitational energy converted to heat energy, temperature rises
when temp high enough, hydrogen nuclei undergo thermonuclear fusion to form helium nuclei. give out massive amounts of energy and star born
star enters long stable period where the heat created by nuclear fusion provides outward pressure - balances force of gravity, everything pulled inwards
eventually hydrogen in core begins to run out - star swells into red giant. becomes red as surface cools
What is the life cycle of a small star?
small star e.g sun becomes unstable, ejects outer layer of dust and gas as planetary nebula
leaves behind hot, dense,solid core called a white dwarf - cools and eventually dissapears
What is the life cycle of a large star?
glows brightly - undergoes more fusion and expands and contracts, forms heavier elements in nuclear reactions
eventually explodes in a SUPERNOVA
exploding supernova throws outer layer of dust and gas into space - leaves dense core called a Neutron Star
if the star is big enough,becomes a black hole
What is red shift?
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when look at light form other galaxies, frequencies appear lower than they should be - the galaxies are shifted towards the red end of the spectrum
measurements suggest all galaxies moving away from us more distant galaxies have a greater red shift as moving away faster
provides evidence for the big bang theory and steady state theory
What is CMB radiation?
low frequency EM radiation from all parts of universe bu mainly in microwave part of EM spectrum
evidence for big bang theory - as universe expands and cools , radiation ‘cools’ and drops in frequency
big bang only theory to explain CMB radiation so is currently most accepted model by scientists
What is the ‘Big Bang’ Theory
matter and energy in universe compressed into small space then exploded and started expanding
expansion still happening and we can use the current rate to estimate the universe’s age
estimated it happened about 14 million years ago
What is the steady state theory?
universe always existed as it is now and always will
based on the idea that the universe appears pretty much the sameeverywhere
explains apparent expansion and red shift by suggesting matter is created in spaces as the universe expands
