Questacon in Canberra has a pretty cool section on space and astronomy. Check out the pictures I took in the gallery below.

A few of the highlights from this exhibition.

**NASA WMAP**

- WMAP is the Wilkinson Microwave Anisotropy Probe
- It launched on June 30, 2001
- Has mapped fluctuations in the cosmic microwave background (CMB) radiation (the oldest light in the universe) and has produced a full map view of the microwave sky
- Has determined the universe to be 13.77 billion years old
- Determined the curvature of space to within 0.4% of flat Euclidean
- Found that the universe is 24% dark matter
- Found that dark energy makes 71.4% of the universe, causing the expansion rate of the universe to speed up

**Morgan Keenan System (MKK)**

- Classification of stars based on temperature
- Categories divided into Roman numerals, with sub-categories and classes
- To completely describe a star the MK luminosity class is appended to the original Harvard classification for the star
- The Harvard Spectral Classification assigns each star a spectral type with is further divided into 10 sub-classes depending on the absorption features present in the spectrum. E,g, our Sun has a temperature of 5,700 Kelvin and is classified as a G2 star
- Our Sun is a main sequence star G2 and the full classification is G2V

**Types of orbit**

- The Moon does not orbit the Earth, the Moon and Earth orbit each other around their common centre of mass. The common centre of mass is inside the Earth
- Kepler showed the orbits of the planets were ellipses with the Sun at one foci
- Newton showed there were other types of orbit
- Elliptical and circular orbits are both bound orbits
- Parabolic and hyperbolic are unbound orbits
- Comets and asteroids typically have hyperbolic or parabolic orbits, they zip around the Sun once and they go off never to be seen again because they do not have gravitationally bound orbits

- Look at the circular cone above, how you slice the cone determines what kind of geometric cross-section you get – horizontal makes a circle, an angle creates an ellipse, increase the angle and get to the bottom of the cone you get a parabolic and cut the cone vertically you get a hyperbola
- So 4 different types of orbits

Additional…

- Newton’s laws of gravity showed that Kepler’s first 2 laws, ellipses and equal area in equal time are a consequence of the conservation of angular momentum (Mass x speed x distance = constant)
- At perihelion the distance to the Sun is smaller so to keep the mass times the speed times the distance the same the conservation of angular momentum the plane must move faster
- At aphelion, further away from the Sun, conversely the speed must decrease
- P squared is a cubed (P^2 = a^3)
- P is the period the time it takes to go around and the semi-major axis of a of the ellipse, a is the average orbital distance

Thank you F.X. Times at Arizona State University for some of the information included.

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