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Astronomy Demo

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