Class Notes (808,754)
Canada (493,378)
Astronomy (233)
AS101 (233)

Module 1 Notes.docx

4 Pages
Unlock Document

Wilfrid Laurier University
Shohini Ghose

Module 1 Notes 8 1 Astronomical Unit = 1 AU = 1.5 x 10 km = 150M km = average distance from Sun to the Earth Light-year (ly) = the distance light travels in one year, approx. 63,000 AU It has been approximately 13.7B years since the Big Bang The Moon’s distance from Earth is about 30x the Earth’s diameter = 384,000km The precession of the Earth’s rotational axis points to the North Star but this will change over time - The Earth rotates from west to east in front of the Sun, giving both day and night - the Sun rises in the east and sets in the west - What you see in the sky depends on where you are; Canadians see constellations and stars that Australians never see - Astronomers measure distances across the sky as angles in units of degrees, arc minutes and arc seconds Zenith – point in the sky directly overhead Nadir – point directly below your feet Celestial Equator – an extension of the Earth’s equator onto the celestial sphere Meridian – the line going from due north, through your zenith and finishing due south Arc Minutes – angular degrees are subdivided into arc minutes (60’ in one degree); is further divided into 60 arc seconds Circumpolar Stars – stars that trace out complete circles The Earth moves along the ecliptic path its rotational axis, on which it makes one revolution each day, is tipped to the ecliptic plane at a constant angle of 23.5° resulting in seasons on Earth. Tropic of Cancer – circle of latitude on the Earth that marks the most northerly position at which the Sun may appear directly overhead at its zenith; occurs once per year at the time of June Solstice Tropic of Capricorn – southern hemisphere counterpart, marking the most southerly position at which the Sun may appear directly overhead The moon takes about a month to circle the Earth; as it circles the Earth it goes through phases of reflected sunlight Orbital Period – from one full moon to the next – approximately 29.5 days Sidereal Period – the time for one revolution relatives to the stars – approximately 27 days Solar Eclipse – Moon blocks out the sunlight at high noon for a period of time Lunar Eclipse – Earth blocks out the Sun’s light at midnight for a period of time Only when the moon crosses through the ecliptic plane, at points called nodes, is an eclipse possible. Also, only when the Sun, Earth and Moon are all lined up is an eclipse possible; phase of the moon must be either new or full. Lunar Eclipse Types – Earth is between the Sun and Moon a) Penumbral - most common, Moon passes through only the penumbra (sunlight is only partially blocked). Result is that the Moon darkens only slightly. b) Partial - part of Moon passes through the umbra while the rest passes through the penumbra. Result is the part of the Moon is darkened completely but rest only slightly darkened with no clear demarcation between the areas c) Total - Moon passes entirely through the umbra. Result is that the Moon is completely dark during the eclipse Solar Eclipse Types – Moon is between the Earth and the Sun a) Total – Moon is relatively close to the Earth in its orbit and the Moon’s umbra touches a small area of the Earth’s surface; anyone within this area sees the sun totally blocked out b) Partial – surrounding the small area of totality lies a larger area falling inside the Moon’s penumbral shadow; anyone within this area sees the moon partially blocked out c) Annular – Moon is relatively far from Earth and the Moon’s umbra may not reach the Earth surface at all; anyone within the small area behind the umbra will see all of the Sun blocked out except a ring of sunlight surrounding the Moon’s disk Five planets closest to the Earth are visible to the naked eye: a) Mercury – at sunrise/sunset b) Venus – closer to the horizon and bright c) Mars – reddish colour d) Jupiter – at night and comparatively bright e) Saturn – slightly more difficult to spot In 2002, all five planets were lined up in the Western sky. This will occur once again in 2040. The planets generally follow the motions of the Sun and Moon in that they move eastward relative to the stars. Occasionally, all planets appear to change direction and move westward relative to the stars, which is a motion referred to as retrograde motion. This is because as the inner planets move faster in orbit and catch up to the outer, slower-moving planets, the outer planets appear to move backwards. Stellar Parallax – occurs when we look at a nearby star from two vantage points; first when the Earth is at one extreme of its orbit around the Sun, and second when the Earth is at the opposite extreme six months later - the nearby star appears to shift laterally against the background of stars behind it Stellar parallax allows
More Less

Related notes for AS101

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.