1. The Solar System consists of the Sun and objects that orbit around it, including 8 planets. 2. The planets can be divided into inner terrestrial planets like Earth and outer gas giants like Jupiter. 3. The motions of objects in the Solar System, such as the Earth's rotation and revolution around the Sun, cause natural phenomena like day/night and seasons.

1. THE SOLAR SYSTEM by Prof. Liwayway
Memije-Cruz

2. CelestialCelestial
mechanics -
thebranch
of astronomy
which deals
with the
motions of
celestial
objects . .

3. Motionsof Heavenly Bodies

4. Celestial Sphere

5.  Constellationshavebeen an important part
of human society and folkloresincewe
humanslived in caves and even before.
Thefascinating scenariosthat weseein the
night sky areso largeand so beautiful that
wehavefelt avery strong urgeto attach
importanceto them. Peoplethuscreate
very interesting storiesand legendsin an
attempt to explain theselarge"pictures" in
thesky.

6. Zodiac: twelveconstellationsthat thesun
goesthrough

7. Ecliptic: thepath that thesun tracesout on
thesphere

8. TheEarth in theCelestial Sphere

10. Earth’sMotion
Rotation Revolution
 Rotation of theearth
describesthespinning
of theearth around its
axis, resulting in the24
hour phenomenon of
day and night over
theearth.
 Revolution on the
other hand describesthe
movement of theearth
around thesun over a
period of oneyear,
causing seasonsto
occur.

11. Timeand Clocks

12. A Sidereal Day
Theearth spins
onceon itsaxis
every 23 hours, 56
minutes(rounded to
thenearest
minute). Thetime
to completeone
completerotation is
known asa sidereal
day and isquite
different from the
traditional concept
of a"day

13. A Solar Day
For astronomers, theday actually
beginswhen thesun crossesthe
meridian. Wecan call this"high noon"
... an old cowboy phrasewhich means
that thesun isat itshighest point in the
day. You will soon seethat theclock
rarely reads12:00 at thistime The
rotation of theearth on itsaxis
eventually forcesthesun to set in the
west, riseagain in theeast, and move
back to themeridian (high noon). This
definesa solarday - high noon to
high noon. Thefirst thing you haveto
realizeisthat theearth spinsslightly
morethan onefull rotation during a
solar day.

14. 1. theplanetsin theSolar System orbit around theSun1. theplanetsin theSolar System orbit around theSun
2. orbitsarealmost perfect - circle: Sun isthecenter of the2. orbitsarealmost perfect - circle: Sun isthecenter of the
circlecircle
3. someorbitsareoval shaped or “stretched out” circles–3. someorbitsareoval shaped or “stretched out” circles–
ellipses: theSun isat the“focus” of theellipseellipses: theSun isat the“focus” of theellipse

15. Aphelion and PerihelionAphelion and Perihelion
•Perihelion - theplace
wheretheplanet isclosest to
theSun.
•Aphelion - when theplanet
isfurthest away from the
Sun.
•“Aphelion" and
"perihelion" comefrom the
Greek language: "helios"
mean sSun, "peri" means
near, and "apo" meansaway
from.

16. Theduration of asolar day variesthroughout theyear. That is,
if you wereto measurethetimefrom high noon to thenext
high noon, you would get adifferent valueevery day. Why?
Kepler'sSecond Law tells usthat thespeed of theearth's
revolution around thesun varies... moving fastest at perihelion
and slowest at aphelion. Therotation rateof theearth, remains
fixed
At aphelion: solar day is fast At perihelion solar day is longer

17. Seasons occur due to Earth’sSeasons occur due to Earth’s
revolutionrevolution

18. Motion of Stars
• Somestars risedirectly east heading to theright, then crossthehigh
southern sky, and eventually set directly west.
• Other starsrisein thesoutheast and follow shorter, lower arcsacrossthe
south beforesetting in thesouthwest.
• And in thenorth, therearemany starsthat never riseor set at all; these
“circumpolar stars” follow counter-clockwisecircles

19. Planetsin theSolar System
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune

21. Inner Planetsor Terrestrial Planets
characterized by their dense, rocky composition
 few or no moons, and lack of ring systems
composed largely of minerals
with high melting pointssuch assilicatesto form the
planets’ solid crustsand semi-liquid mantles, and
metallic dust grainssuch asiron, which formstheir
cores.
threeof thefour inner planetshaveatmosphere. All
haveimpact craters, and all but onepossesstectonic
surfacefeatures, such asrift valleysand volcanoes.

22. TheOuter Planetsor Jovian
Planets

23. TheOuter Planetsor Jovian Planets
• Collectively makeup 99 percent of themassknown to orbit theSun.
• Jupiter and Saturn aretruegiants, at 318 and 95 Earth masses,
respectively, and composed largely of hydrogen and helium
• Uranusand Neptuneareboth substantially smaller, being only 14 and 17
Earth masses, respectively.
• Their atmospherescontain asmaller percentageof hydrogen and helium,
and ahigher percentageof “ices”, such aswater, ammoniaand methane.
For thisreason someastronomerssuggested that they belong in their own
category, “Uranian planets” or “icegiants”.
• All four of gasgiantsexhibit orbital debrisrings, although only thering
system of Saturn iseasily observablefrom Earth. Theterm outer planet
should not beconfused with superiorplanet, which designatesthose
planetswhich lieoutsideEarth’sorbit (thusconsisting of theouter planets
plusMars.

24. Inferior planets: Morning and evening stars
Mercury and
Venusare
classified as
inferior planet
becausetheir
orbitalsarefound
insidetheorbit of
theearth and
seem closer to the
sun
Manifest both
progradeand
retrogrademotion

25. Superior Planets
 Mars. Jupiter,
Saturn, Uranus
and Neptune
 Exhibit their
own revolution
and motion from
west to east
(prograde
motion)
As they
catches up by the
Earth , they
move in opposite
direction which is
from east to west
(retrograde

26. Retrogradeand Prograde
 Retrogradeorbit:
thesatellite(red)
orbitsin the
direction opposite
to therotation of
itsprimary
(blue/black)

27. Aristotleand theEarth-Centered
Universe
Aristotle - one
of thefamous
Greek
philosophers
known for his
ideathat the
earth isthe
center of the
solar system.

28. Renaissanceand theHeliocentric Solar
System
• TheEarth revolves
around thesun as
proposed by Arstarchus
of Samos
•Copernican
Revolution: Nicolaus
Copernican proposed
themathematical model
of theheliocentric
system which was
supported by Johannes
Kepler and Galileo
Galilei

29. Motionsof theEarth and theMoon
o cause
theday
and night
o reason
for
seasons

30. SeasonsSeasons

31. • The Moon moves around the Earth in an
approximately circular orbit, going once
around us in approximately 27.3 days, or
one sidereal period of revolution.
• Each night, it moves about 13 degrees,
or about 26 diameters, to the east.

32. Phasesof theMoon

33. Let us just enjoy the magic of the night sky…Let us just enjoy the magic of the night sky…