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Chapter 2 Notes – The Sky
Astronomy
Name:
Date:
I. Constellations
A. In ancient times, constellations only referred to _______________________ stars that
appeared to form groups
B.
They were believed to represent great _________________ and mythological figures. Their
position in the sky seemed to tell _________________ that were handed down from
generation to generation over thousands of years
C.
Today, constellations are well-defined ________________ on the sky, irrespective of the
presence of absence of bright ______________ in those regions
D. The stars of a constellation only __________________ to be close to one another. Usually this
is only a _______________________ effect. The stars of a constellation may be located at very
____________________ distances from us.
E.
Stars are named by a ______________ letter. (____, _____, _____) according to their relative
_________________within a given __________________ and the possessive form of the
_____________ of the constellation:
________________ = _____ Orionis
Rigel = __________ Orionis
II. The Magnitude Scale
A. First introduced by ___________________ (160 – 127 BC)
i. Brightest stars : _________ magnitude
ii. Faintest stars ( _____________ eye): _______ magnitude
iii. 1st mag stars appear ____________ times brighter than 6th mag stars
iv. larger magnitude => _________________ object!
B. The magnitude scale system can be extended toward ____________ numbers (________
bright) and numbers greater than _______ (faint objects)
Sirius (brightest star in the sky) m = ___________
Full moon: m = ___________
Sun: m = _______________
Naked eye limit: m = _____________
III. The Celestial Sphere
A.
Zenith = _______________ on the celestial sphere directly overhead
B. __________ = Point on the c.s. directly underneath (____________ visible!)
C. The distance between two stars on the celestial sphere can only be given as the difference
between the _____________________ in which we see the stars.
i. Therefore, distances on the celestial sphere are measured as ______________ (degrees,
arc minutes, arc _______________)
IV. Apparent Motion of the Celestial Sphere
A. Looking north, you will see stars apparently circling ________________________ around the
Celestial North Pole.
B. Some constellations around the Celestial North Pole never set. These are called __________
___________________
C. Looking east, you see stars rising and moving to the upper _________________ (south)
D. Looking south, you see stars moving to the __________________ (west)
V. The Sun and its Motions
A.
Earth’s ________________ is causing the day/night cycle
B. Due to Earth’s ___________________ around the sun, the sun appears to move through
_____________________ constellations.
C. The Sun’s apparent path on the sky is called the _______________.
VI. The Seasons
A.
Earth’s __________ of rotation is inclined by ________, which causes the seasons.
B. The seasons are caused only by a ________________ angle of incidence of the sun’s rays
C. We receive _________ energy from the sun when it is shining onto the Earth’s surface under a
___________________ angle of incidence
D. The seasons are ___________ related to Earth’s distance from the _____________. In fact, Earth
is slightly ________________ to the sun in ____________ than in summer (Northern
hemisphere)
E.
Earth’s distance from the sun has only a very _______________ influence on seasonal
____________________ variations.
VII. The Motion of the Planets
A. The planets are orbiting the sun almost exactly in the plane of the _______________.
B. The Moon is orbiting _______________ in almost the same plane (Ecliptic)
C. Mercury appears at most __________ from the sun. It can occasionally be seen shortly after
_______________ in the west or before sunrise in the ________________
D. Venus appears at most _____________ from the sun. It can occasionally be seen for at most a
few hours after ________________ in the west or before sunrise in the ______________
VIII. Astronomical Influences on Earth’s Climate
A. Factors affecting Earth’s climate:
i.
Eccentricity of Earth’s ____________ around the sun (varies over period of
______________ years)
ii.
Precession (period of _____________ years)
iii.
Inclination of Earth’s _______________
B. Milankovitch Hypothesis: Changes in all three of these aspects are responsible for long-term
____________________________ (ice ages)