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Astronomy Demo
| Question | Answer |
|---|---|
| How is brightness of a star measured? | Luminosity, apparent magnitude + absolute magnitude |
| Luminosity | Total amount of energy produced by a star per second |
| Luminosity of Sun | 1 |
| Luminosity of Sirius | 22 |
| Why does Sun appear brighter than Sirius? | bc Sun is much closer to Earth than Sirius |
| Apparent magnitude | Brightness of star as seen by observer from Earth |
| Who developed Apparent Brightness Scale? | Hipparchus (190 BCE- 120 BCE) |
| Lower magnitude | More apparent brightness |
| Sun's apparent magnitude value | -27 |
| Dimmest star seen unaided's apparent magnitude | 6 |
| Absolute magnitude | Apparent magnitude of star viewed from 33 ly away |
| Is Sun closer or further than 33 ly from Earth? | Closer |
| Would Sun appear brighter or dimmer if it was 33 ly away? | Dimmer |
| Would apparent magnitude increase or decrease if Sun was 33 ly away? | Increase |
| Higher magnitude value | Less apparent brightness |
| Sun's absolute magnitude | 4.8 |
| Polaris' absolute magnitude | -3.63 |
| If Sun and Polaris were side by side, which would appear brighter? | Polaris bc its magnitude value is lower |
| Colour of star indicates? | Temperature of star's surface |
| Colours of star in increasing order of temperature | Red, orange, yellow, white, blue |
| What colour is the Sun? | Yellow |
| How is star composition determined? | Materials release light when "excited", different materials release different colours, spectrographs determine which colours are present, each element causes different colours to appear on spectrum |
| Mass of Sun in kg? | 2 x 10 to the power of 30 kg |
| Smallest star mass? | 0.1 solar masses |
| Mass of Sun in solar masses? | 1 solar mass |
| Largest star mass? | 120 solar masses |
| Constellation | Large region of stars that form pattern officially recognized by International Astronomical Union when seen from Earth |
| How many constellations are there? | 88 |
| Brightest constellation? | Southern Cross (Crux) |
| Largest constellation? | Hydra |
| Asterism | Smaller unofficial star patterns within a constellation |
| How can you find Polaris? | Extend line through two end stars of Big Dipper cup to first star in handle of Little Dipper |
| Ecliptic | Apparent path followed by Sun (as seen from Earth) |
| Zodiac constellation | Constellation containing ecliptic |
| Star finder | Tool for determining which constellations are visible in night sky for particular date and time or how stars are oriented |
| Why are some stars always visible during the night? | Bc they are close to the poles |
| Star or constellation always visible in night sky? | Circumpolar |
| How many celestial objects can you see in daytime? | Sun, sometimes Moon and others |
| How many celestial objects can you see in nighttime? | As many as 2000 |
| Luminous | Celestial object that generate own light (stars) |
| Non-luminous | Do not generate own light (sometimes reflective) (moons, planets) |
| Direction of Sun's apparent motion throughout day? | East to west |
| Cause of Sun's apparent motion? | Counterclockwise rotation of Earth (Earth spins East) |
| Direction of Sun's apparent motion throughout year? | West to east |
| Retrograde motion | When planets appear to slow to a stop, reverse direction and loop across sky |
| Cause of retrograde motion? | Planets moving slower than Earth appear as if they are travelling backward when Earth is faster |
| Why do planets further from Sun move slower than closer planets? | Force of Sun's gravity is weaker farther away, and bc further planets have longer orbits |
| Whose retrograde motion can we see from Earth? | Mars, Jupiter and Saturn |
| When does planet look biggest and brightest from Earth? | When orbits cross |
| 1 Mars year | 2 Earth years |
| How often do Earth and Mars' orbits cross? | Every two years |
Created by:
lovinglifexoxo
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