Astronomy Part 2 Flashcards
What is the altitude of a star?
The angle above the horizon
What is the azimuth of a star?
The compass bearing clockwise from North
What is the zenith of a star?
The point directly overhead, 90 degrees above the horizon
What are circumpolar stars?
Stars located near celestial poles that can be seen all year round
What is the ecliptic?
An imaginary line along which the sun and planets appear to move
What causes the seasons of the Earth?
The tilt of the Earth’s axis
What is the star located at the North Celestial Pole?
Polaris
What is the order of stars, according to the Bayer Naming System?
Alpha, Beta, Gamma, Delta
What is so unique about the star Beta Orionis?
The brightest star in this constellation is named Beta instead of Alpha
What is our solar system?
A flat disc shape with all planets rotating about the sun in the same direction
What is the distance of a star in light years?
9.47 X 10 to the power of 12 KM
For observers in the Southern Hemisphere, what are circumpolar constellations?
Southern Cross and Pointers
What is the significance of Polaris in the Northern Hemisphere?
Polaris is only visible in the Northern Hemisphere and all the stars in the Northern Hemisphere rotate about it
What is luminosity synonymous with?
The absolute magnitude of a star
What is the difference between absolute and apparent magnitude?
Apparent magnitude is how bright a star is when viewed from Earth, whereas absolute magnitude is how bright the star is from 33 light years away
When viewed from Earth, what does the colour of a star tell us about?
Surface temperature
What does the spectral analysis of a star tell us about?
Chemical composition
What is the greater measure of magnitude?
A negative reading
What percentage of stars run our galaxy are multiples?
More than 50%
What is the classification of our sun?
1, G
What do the x-axis and y-axis of the HR diagram stand for?
X-Axis= Temperature (kelvin), Y-axis= Luminosity
On the HR diagram, where are stars grouped according to their life span?
Larger stars which are shorter lived due to quicker burning of fuel are found at the top and smaller stars which are longer lived at the bottom
What are white dwarfs?
The remnants of stars similar to our own, which no longer burn fusion but radiate heat, becoming dimmer whilst maintaining higher temperatures
Which coloured stars are the hottest and which are the coolest?
Blue stars are the hottest, red stars are the coolest
What are red giants?
Very luminous and low in density allowing them to have similar mass to our sun but considerably larger radius
What are blue super giants?
Very large stars which burn fuel rapidly, are short lived and culminate in supernova
What does the main sequence contain?
The vast majority of stars, which follow the red of temperature directly relating to luminosity
What is a red dwarf?
The most common star, smaller than our sun, slowly burn fuel and are hard to spot
What is a white dwarf?
Hot, small and very dense, nuclear reactions are finished
How did Hubble use the Doppler effect?
To observe light spectrum coming from distant galaxies, which contained the information about the motion of the galaxy to determine the distance and speed of galaxies
