Math, Math, Math!
a) What does AU stand for?
b) How many kilometres are in one AU?
-astronomical unit
-150 million
Explain the main difference between the geocentric and heliocentric models and name the astronomer who coined each term.
geocentric- earth at the centre of universe (Ptolemy)
heliocentric- sun at the centre of the universe (Copernicus)
What are the two types of telescopes and what do they each use?
Refracting- uses lenses to focus light
Reflecting- uses mirrors to focus light
Briefly explain what the Hertzsprung-Russell Diagram shows and patterns within the chart.
top left- hot, bright
top right- cool, bright
bottom left- hot, dim
bottom right- cool, dim
Name the 3 types of galaxies AND briefly explain the shape of each (include sub category explanations)
Elliptical (round, football shaped, scale of 0-7, 0 being round, 7 being flattened)
Irregular (characteristics do not fall under elliptical or spiral)
Spiral (subcategories- spiral or barred-spiral, a-b-c, a being arms tightly wound to centre/bar, c being arms loosely wound)
Orbital velocity is shown with the formula:
2πR/T
What does the R stand for in this formula?
R- average radius of the orbit
Differentiate between aphelion and perihelion.
Aphelion- farthest from the sun
Perihelion- closest to the sun
What are the 3 powers of a telescope?
-light gathering power
-resolving power
-magnifying power
Differentiate between an asterism and a constellation. Give one example of each.
asterism- a named group of stars (Big dipper, great square of pegasus)
constellation- an area of the sky that contains groups of stars (ursa major, sagitarius, pegasus, taurus)
Explain the difference between a globular cluster and an open cluster. Give 3 differences.
Globular- 10,000-1 million stars, spherical area, 75 light years across, older stars
Open- 100-1000 stars, younger stars, located in disk of galaxy
Differentiate between Azimuth and Altitude. How would you calculate each? What two instruments are necessary to measure both?
Azimuth- measure from true north to object (horizontal) (0-360)
Altitude- measure from horizon to object (0-90)
You would need a compass and astrolabe to accurately measure both altitude and azimuth.
Kepler came up with 3 laws of motion. What did his second law (equal area law) explain?
As a planet moves around its orbit, it sweeps out equal areas in equal times.
What is interferometry and what can it achieve (what is the advantage?)
-connecting multiple telescopes together to work as if they were a single telescope
-can achieve higher resolution
differentiate between apparent visual magnitude and absolute magnitude. Explain the number system for apparent visual magnitude and what it means.
apparent- how bright an object looks from Earth
-higher number= dimmer
-lower number= brighter
-absolute- how bright an object actually is
a) what is a variable star?
b)What are the 2 types of variable stars and differentiate between the pulsation periods of each
-RR Lyrae (1.5 hours and a day) & Cepheid variable stars (1 and 100 days)
If Star A has a magnitude of 4.0, and star B has a magnitude of 10.32, what is the intensity ratio? Which is the brighter star?
(mB – mA) = (10.32 – 4.0) = 6.32
2.512 6.32 = 337
Thus Star A is 337 times brighter than Star B
Which astronomer saw sunspots, phases of Venus and developed the concept of inertia?
Galileo
What is the magnification of a microscope whose primary mirror has a focal length of 80 cm if it is used with an eyepiece whose focal length is 0.5 cm?
M = Fp/Fe
= 80/0.5
= 160 times
Explain Right Ascension and Declination.
RA- analagous to longitude (vertical), measured from 0-24 hours from east or west of the vernal equinox
Dec-analagous to latitude on earth, measured from 0-90 degrees north or south of the celestial equator
Differentiate between population I and II stars and where they are found within the galaxy
II- old main sequence stars, elliptical and spiral halos, found in bulge and halo
Mars and Earth are 55.8 million km apart.
The angular diameter of Mars is observed to be 25.1 arc seconds.
Find the diameter of the red planet.
θ = 25.1”
D =55.8 x 106 km or 5.58 x 107 km
d = ?
θD / 206 265" = d
25.1” x 5.58 x 107 km = 6,790 km
206,265”
Thus the diameter of Mars is ~ 6,790 km
State Sir Isaac Newton's 3 Laws of Motion.
-an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
-the relationship between an object's mass, its acceleration, and the applied force is F=ma
-For every action, there is an equal and opposite reaction.
Compare a 4 cm telescope with a 24 cm telescope. How much more light will the larger telescope gather?
LGPA/LGPB= (24/4)2
=62
H-based on what an observer sees in the sky, altitude and azimuth, fixed to earth not the stars, same object will have different coordinate numbers depending on observation point and time.
E- object has a fixed position on celestial sphere, always same coordinate numbers, apparent positions change over time as earth rotates, not all stars visible to observer.
List AND describe the 3 theories of the future of the universe
Open- keep expanding
Flat- expand to a point and then stop
Closed- expand to a point and then contract