ASTRON 1F03 Study Guide - Midterm Guide: Right Ascension, Declination, Tropical Year
20 May 2018
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Get an iclicker !
avenue!
-announcements"
-registering clicker"
-enter first/last name ID"
-Student email"
-clicker ID"
15% is pass/fail (observing) go on avenue for it. Planetarium show to understand some of the
early aspects of the course. (Can sign up in slots) "
Lecture slides will be put on avenue. (Will be put up after class)"
In class labs will be on fridays. Will be 6,5,7 labs. "
Focus on the themes discussed.try and understand connections he’s making "
Chapter 0: Charting the heavens "
Why does the week have 7 days? "
Objects in the heavens are divided onto fixed stars and the seven wandering stars known as
antiquity. "
Moon, Mars, Mercury, Jupiter, Venus, Saturn, Sun"
What is the milky way?"
Cities generate so much light that you can’t really see the stars and galaxies at night.
(Sometimes can see venus) "
Astronomical influences in human culture"
Time (year, month, week, day)"
Constellations (star groupings):Myths, astrology (even if it is nonsense) "
Eclipses: 2024 will go through niagara peninsula "
Will generally follow the development of astronomy from small scales to the large and discuss
the corresponding enabling scientific advances. "
In the chapter:"
-scale of the universe (It’s big)"
-Earth’s orbital motion"
-Measure of the moon"
-Measurement of distance"
-Science and scientific method (won’t talk too much, but will be the most important)"
Scales of the universe: "
Earth is average, don’t occupy ant special place in the universe"
Universe: Totality of all space, time, matter, and energy."
Astronomy: Study of the universe"
Scales are very large, measured in light years, distance travelled in a year (~10 trillion km)
10^13Km "
See ‘power of Ten Charles and Ray Eames (youtube)"
Very hard to perceive depth in space"
Declination: Latitude, north and south."
Right ascension: Measured in hours, minutes, and seconds eastward from the vernal equinox "
Earth’s orbital motion:"
Daily cycle, noon to noon is diurnal motion-solar day."
Exam: why this is true"
Stars aren’t usually in the same place for 24 hours due to earth’s orbit around the sun, When
they were in the same place, gain, one side"
Earth has 1 degree ,in like 4 minutes "
Next time: Clicker questions"
Earth’s Orbital Motion "
Daily Cycle: noon to noon is diurnal motion-Solar Day"
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find more resources at oneclass.com
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-Stars aren’t in the same place for 24 hours, due to the earth’s mortal around the sun. When
they're in the same place again, one sidereal day again, one sidereal day has passed"
If the sun rotates on its axis in the opposite senses at the same rate, the siderealday remains
the same"
What causes seasons? The earth’s 21.5 degree rotation "
Tropical year is different from regular "
Moon takes 29 days to make a 360 around the earth. "
Sidereal month is 2 days shorter than synodic month "
* know difference between sidereal and synodic month "
Everyone on earth sees the same phase of the moon in 24 hours "
Lunar eclipse: When earth is between the earth and the sun. (Moon is red) "
Solar eclipse: when moon is between earth and the sun "
Sun is much bigger and further away from the moon. So the disk of the moon and disk of the
sun aligns. "
Corona: (Ring area around the sun)
Umbra: the!complete!or!perfect!shadow!of!an!opaquebody,!as!a!planet,!
where!the!direct!light!from the!source!of!illumination!is!completely!cut!off.
Penumbra: the!partial!or!imperfect!shadow!outside!the
complete!shadow!of!an!opaque!body,!as!a
planet,!where!the!light!from!the!source!ofillumination!is!only!partly!cut!off.
Rich variety of solar eclipses because moon and sun subtend nearly the same angle from
earth. In the far future, will only have annular eclipses because must conserve angular
momentum, moon moves away from earth every year, will never get a total eclipse"
Eclipses don’t occur every month because earth’s and moon’s orbits are not in the same plane
(~5 degree tilt) "
New vs Full moon
2024 April 8th: niagara peninsula solar eclipse"
*fat shadows on diagram: Projection of the map. The area is no bigger, but just the scaling of
the map. "
Measuring Distances:"
Triangulation: Measure baseline and angles, and you can calculate distance. (Physics sin/cos)"
Parallax: Similar to triangulation, but looking at apparent motion of object against distant
background from two vantage points. Earth to sun: 1 ASU (astronomical unit) "
Jan and July stars move because of the effective parallax. For nearest star, will not move too
far (effect not as effective) "
D(parsecs)=1/p(arseconds) [inverse relationship]"
Put finger close, each eye will jump a large amount relative to background"
Scientific theories:"
-must be testable"
-continually tested"
-simple (Occam’s razor)"
-Elegant"
Scientific theories can be proven wrong, but they can never be proven right with 100%
certainty "
Observation leads to theory explaining it"
Theory leads to predictions consistent with previous observations"
Predictions of new phenomena are observed, If the observations agree with theprediction,
more predictions can be made. If not, a new theory must be made."
Observation (experiment)>Theory>Prediction>Observation (experiment)"
Astronomy/Astrophysics cannot perform experiments in the normal way (Distances and
timescales too large) "
find more resources at oneclass.com
find more resources at oneclass.com
STUDY THIS SHIT ASAP
-Often must look at populations to understand evolution, etc. Frequently cannot see evolution
in individual objects"
Basic assumptions of unity of structure and behaviour throughout the universe-supported by
observation"
Observation: Measurement: what’s out there? Telescopes, data analysis, software tools"
Physical understanding; what’s going on inside? Theory, computer modelling, silumation,
interpretation "
Stars move around in the sky because earth is spinning on its’ axis "
Chapter 1: Copernican revolution
Motions of planets
Birth of Modern Astro
Laws of Planetary Motion
Newton’s Laws
Sun, moon, stars all have simple movements in the sky, consistent with earth centred system…"
Planets"
-move with respect to fixed stars"
-change in brightness"
-change in speed"
-have retrograde motion"
-difficult to describe"
-in earth centred system "
A basic geocentric model, showing an epicycle (Used to explain planetary motions "
The sun, moon. And planets follow the ecliptic path through the constellations "
Conditions for a solar eclipse are favourable every six months at new moon "
*learn phases of the moon*"
Lots of epicycles were needed to accurately tract planetary motions, especially retrograde
motions, this is Ptolemy’s model "
Motion of the planets:"
Aheliocentric (sun—centred) model of the solar system easily describes the observed motions
of the planets, without recourse to complications such epicycles "
Nicholas Copernicus 1473-1543: heliocentric model"
Galileo Galilei: many key, telescopic, astronomical observations"
Tycho Brahe: meticulous observations of planetary motion"
Johannes Kepler: discovered/developed the laws of planetary motion"
Birth of modern astronomy"
The phases of Venus are impossible to explain in the earth-cantered model of the solar system "
Kepler’s Law of planetary Motions: (midterm) "
1: Planetary orbits are ellipses (not circles), sun at one focus"
2: an imaginary line connection sun and planet sweeps out equal areas in equal times "
3, Square of period of planet’s orbital motions is proportional to cube of semi-major axis."
P^2 (years)=a^3(AU)"
Dimensions of the solar system "
-distance from earth to the sun is called an astronomical unit. Actual length may be measured
by bouncing a radar signal off Venus and measuring the transit time. "
*solar systems as a whole: will see orbits of the planets (almost completely circular) "
Isaac Newton 1642-1727"
Newton’s law of motion explain how objects interact with the world and with each other. "
First Law:"
An object at rest will "
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
15% is pass/fail (observing) go on avenue for it. Planetarium show to understand some of the early aspects of the course. (can sign up in slots) Lecture slides will be put on avenue. (will be put up after class) Focus on the themes discussed. try and understand connections he"s making. Objects in the heavens are divided onto xed stars and the seven wandering stars known as antiquity. Cities generate so much light that you can"t really see the stars and galaxies at night. (sometimes can see venus) Constellations (star groupings):myths, astrology (even if it is nonsense) Will generally follow the development of astronomy from small scales to the large and discuss the corresponding enabling scienti c advances. Science and scienti c method (won"t talk too much, but will be the most important) Earth is average, don"t occupy ant special place in the universe. Universe: totality of all space, time, matter, and energy.
