Download Galaxy Zoo: Pre and post‐workshop information

Key Stage 4: The Expanding Universe
Pre- and Post‐Workshop Information
Pre‐Workshop:
The following information is designed to prepare students for the workshop and
is linked to the curriculum (below). It is not essential reading however teachers
may find it useful to discuss these concepts beforehand with the class.
Post‐Workshop:
Summary questions are provided for the students to answer in class or for
homework as a way of cementing the material covered in the workshop.
Extension activities to the workshop are available to carry out as part of a lesson
or to be given out as a mini‐project. These can be found here:
http://www.nmm.ac.uk/schools/ks4-programmes-at-the-royal-observatory
Glossary
Acceleration
Dark matter
Electromagnetic
spectrum
Emission
Frequency
Galaxy
Nebula
Radiation
Stellar
Universe
Gradient
Red shift
Vacuum
Gravity
Speed
Velocity
Wavelength
Waves
Curriculum Links
KS4: AQA Physics: 10.4–7, P1b 11.7; Edexcel Physics: P1b 12.8, P1b 12.16, P1b
12.18, P1b 12.20; Edexcel Astronomy: 4.14–16, 4.18–20, 4.41–44; OCR 21st
Century Science: P1.3 2, P1.3 6‐7, P1.3 10‐14, P6.3 1‐4, P7.4 1‐4; OCR Gateway
Science: P2 h
Pre‐Workshop Information for Teachers
In 1923 Edwin Hubble looked at galaxies (which he thought were nebulae or
clouds of bright gas) through a 100” reflector (telescope with a mirror) on Mt
Wilson in the US. He took a photo of Andromeda (which can be seen on a clear
night with the naked eye). Hubble grouped these galaxies according to similar
characteristics. The Galaxy Zoo project (www.galaxyzoo.org) is an example of
citizen science whereby the public have an opportunity to contribute to scientific
research. The project involves classifying millions of galaxies. Knowing the
morphology of a galaxy tells us something about its evolution and gives us an
insight into the structure and history of the Universe
Hubble analysed the light from very distant galaxies and found that their spectra
were all redshifted. This Doppler effect whereby wavelengths of spectral lines are
affected by the motion of the light source indicates all distant galaxies are
receding from us. This was a huge discovery as previously scientists thought the
Universe was static. Hubble’s results of an expanding Universe then led to the Big
Bang theory for the origin of the Universe.
Hubble showed there was a positive linear relationship between the velocity and
distance of distant galaxies i.e. more distant galaxies are receding faster. The
gradient of this graph is called H0 (Hubble’s constant), this gives the time since
the Big Bang i.e. the age of the universe.
The most accurate value for the Hubble constant has been determined using a
different technique to Hubble. A satellite called the Wilkinson Microwave
Anisotropy Probe (WMAP) has been measuring temperature fluctuations as small
as 0.0002 K in the left‐over radiation from the Big Bang (called the cosmic
microwave background, CMB) since 2001. This is radiation that has cooled and
expanded with space thus entering the microwave (long wavelength) region of the
electromagnetic spectrum. Ripples in the CMB indicate the initial conditions for
the formation of galaxies and reveal the shape and fate of the Universe. WMAP
has measured the age of the Universe to be 13.7 billion years.
The European successor to WMAP, a satellite called Planck is currently mapping
the sky using radio receivers operating at very low temperatures. They will reveal
anisotropies (temperature differences) in the CMB to a resolution of 1 microkelvin
and will determine a more precise value for H0.
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Post‐Workshop Questions
1) What is the difference between velocity and speed?
2) On a distance‐time graph what does the slope (gradient) represent? What can
you say about the object’s motion if the slope gets steeper?
3) If an object moves a distance of 2 km in 3 minutes, what speed is it moving at?
4) Calculate the distance in km that light travels in one year (speed of light, c = 3 x
108 m/s).
5) Calculate the amount of energy transferred from a 60 W light bulb that is
switched on for 5 minutes. Use the formula: energy (Joules) = power (Watts) x
time (seconds).
6) What factors interfere with observations of the night sky?
7) A star is 15 parsecs away. What is its distance in light‐years?
(1 parsec = 3.0857 X 1013 km)
8) What is the Universe made of?
9) Outline the supporting evidence for the Big Bang
10) Write down Hubble’s law. What are the units of Hubble’s constant (H0)?
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Post‐Workshop Questions: Answers
1) Velocity is speed (distance travelled over time) with direction.
2) The gradient represents the speed (distance ÷ time). A steeper slope shows the
object has a greater speed.
3) Speed = distance ÷ time. Speed of object = 2000 m ÷ 180 sec = 11.1 m/s
4) Distance = speed x time. Distance = (3 x 105 km/s) x (60 x 60 x 24 x 365.25
seconds) = 9.47 x 1012 km
5) Energy = 60 x 300 sec = 18 000 J
6) The atmosphere distorts light reaching us from space, light pollution reduces
our ability to observe faint objects, weather (clouds) affects our view of the night
sky.
7) From question 4, 1 light‐year (ly) = 9.47 x 1012 km. Star is 15 x 3.09 x 1013 =
4.64 x 1014 km. Distance in ly = 4.64 x 1014 km ÷ 9.47 x 1012 km = 49 ly.
8) Energy, luminous matter (in the form of stars, rock, dust and gas), dark matter
and dark energy.
9) Hubble found distant galaxies were moving away from us indicating the
Universe is expanding and must have originated from a single point. Other
evidence comes from the discovery of relic radiation from the Big Bang, the
cosmic microwave background, which has a low energy (2.7 K) and an
overabundance of helium that must have been produced in the early hot
Universe.
10) v = H0r, where v is the velocity of the receding galaxy, r is the distance from
Earth and H0 is the Hubble constant, units km/s/Mpc.
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