© Sierra College Astronomy Department1 Clickers! Grab the Clicker which corresponds to your Astro 2...

© Sierra College Astronomy Departmen© Sierra College Astronomy Departmentt

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Clickers!Clickers!

• Grab the Clicker which corresponds to your Astro 2 ID number (EX: If your Astro 2 ID number is 3460 grab the clicker which has “60” on it)


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AnnouncementsAnnouncements• Remember to attend third hour!

– Which Third Hour you are assigned are posted online – IMPORTANT NOTE: 3RD HOUR DOES NOT FULFILL A LAB

REQUIREMENT: IT IS SIMPLY THE 3RD HOUR OF THE LECTURE• Astro labs: Astro 11 and Astro 14

– Bring the 3rd hour sheets (found in the Astro 10 Handbook)!• Homework – Assignment 01 is due on next Friday by Noon!

– Homework assignments from MasteringAstronomy at http://www.masteringastronomy.com

– Do Assignment 00 to get used to the style of online homework• Remember your 4-digit Astro 10 ID number

– That was the number printed on the yellow cards– Put this on 3rd hour assignments and any else you turn in

• We’ll be practicing the use of the “clickers”

Fall Semester

http://astronomy.sierracollege.edu/

http://www.masteringastronomy.com/

http://www.masteringastronomy.com/

33© Sierra College Astronomy Departmen© Sierra College Astronomy Departmentt

The SkyThe SkyAn Earth-Centered PerspectiveAn Earth-Centered Perspective


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• Representing position with coordinates:–Flat surface: 2 dimensions

• coordinate system of this room• coordinate system of Rocklin

–Surface of a sphere: 2 dimensions• coordinate system of Earth• coordinate system of the Sky

Lecture 2: Patterns in the SkyLecture 2: Patterns in the Sky

Describing positionsDescribing positions


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• Describe with the Terrestrial Coordinate system: longitude-latitude–Points of reference: North pole, equator

–Two angular coordinates: latitude, longitude

–Zero point of longitude: prime meridian


Position on the EarthPosition on the EarthE-1


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AnglesAngles

Measuring the Positions of Objects on Spheres• A minute of arc (arcmin or ´) is one-sixtieth (1/60) of

a degree of arc.• A second of arc (arcsec or ´´) is one-sixtieth (1/60)

of a minute of arc.• A fist held at arm’s length yields an angle of about

10°.• A little finger held at arm’s length yields an angle of

about 1°.• Angular separation, measured from the observer, is

the angle between two objects in the sky.

Angular sep.

Fist & Finger

Arcminarcsec


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Position in the Sky - IPosition in the Sky - I

• Describe with the horizon system–Two angular coordinates: altitude, azimuth

–Points of reference: zenith, horizon

–Zero point: north• meridian stretches from north to zenith to south

–But this won’t work as a permanent designation!!!! Why?

Horizon system

Horizon system2


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• Positions: Use the Equatorial Coordinate System on the Celestial SphereCelestial sphere is the sphere of heavenly objects

that seems to center on the observer.Celestial pole is the point on the celestial sphere

directly above a pole of the Earth. In the Northern Hemisphere one can see the north celestial pole directly above the North Pole. In the Southern Hemisphere the south celestial pole sits above the South Pole.


Position in the Sky - IIPosition in the Sky - II

01-03

CS

Fig 1-19

CS Hor

CS ship


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• Two angular coordinates: declination, right ascension–Points of reference: north celestial pole,

celestial equator–Zero point: vernal equinox

• The Altitude of the celestial pole above the horizon is equal to your Latitude


Position in the Sky - IIIPosition in the Sky - III

01-03

Dec

RA

Fig 1-19

CE


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• Stellar motion: “Stars are fixed on the celestial sphere, which rotates from east to west (on a minute-by-minute basis) completing one full turn each sidereal day.”– This is called diurnal motion

• The circular region around the north celestial pole in which stars never set is referred to as the North Circumpolar Region.


Position in the Sky - IVPosition in the Sky - IV

01-03

CS

CS ship

Fig 1-19

trails

CS CosmEss


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• East: stars rise, altitude increases, azimuth increases

• South: stars rise and set, altitude increases and decreases, azimuth increases

• West: stars set, altitude decreases, azimuth increases

• North: stars neither rise nor set, but rotate around a pole (circumpolar motion); altitude and azimuth both alternately increase and decrease


Motions of the Stars in CaliforniaMotions of the Stars in California

California paths


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Differences in LatitudeDifferences in Latitude

• Consider a star on eastern point of horizon

• Equator: straight up (altitude increases, azimuth unchanged)

• California: up at an angle (altitude and azimuth increase)

• North pole: horizontal motion (altitude unchanged, azimuth increases)

Pole

Equator

40 NLatitude


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Vega

AltairDeneb

Summer Triangle

Look up into the sky Looking High Southeast, 9:30PM, early September

Northern Cross

LYRA

CYGNUS

DELPHINUS

SAGGITA

AQUILA

Albireo


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The Celestial SphereThe Celestial SphereConstellationsConstellation (from the Latin, meaning “stars

together”) is an area of the sky containing a pattern of stars named for a particular object, animal or person.

The earliest constellations were defined by the Sumerians as early as 2000 B.C.

The 88 constellations used today were established by international agreement.

Asterisms are unofficial arrangements of stars. (Ex: Big Dipper, Pleiades, Northern Cross)

SummerWinter


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The Sun’s Motion: How Long Is A Year?The Sun’s Motion: How Long Is A Year?

• The Sun appears to move constantly eastward among the stars (on a day-to-day basis).

• The time the Sun takes to return to the same place among the stars is about 365.24 days.

• Consequently, the stars rise about 4 minutes earlier each day.

01-10C

Ecliptic

SC001

Sun’s path


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The Sun’s Motion: How Long Is A Year?The Sun’s Motion: How Long Is A Year?

The Ecliptic• The celestial equator is a line on the celestial

sphere directly above the Earth’s equator.• The ecliptic is the apparent path of the Sun on

the celestial sphere.• The zodiac is the band that lies 9° on either side

of the ecliptic on the celestial sphere and contains the constellations through which the Sun passes.

02-05CC

Ecliptic on CS

Sun’s path

CE

Ecliptic on Map


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Solstices and EquinoxesSolstices and Equinoxes

• As the Sun marches on the ecliptic it encounters 4 special points

• Equinoxes: The 2 intersections of ecliptic and celestial equator– Vernal (March 20)– Autumnal (Sept 22)

• Solstices: The 2 extremes in declination of ecliptic– Summer (June 21)– Winter (Dec 21)

Seasons

Ecliptic on CS

Ecliptic


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The Length of a DayThe Length of a Day

• Sidereal Day – The length of the day with respect to the stars. It is 3 min. 56 sec. SHORTER than the solar day.

• Solar Day – The length of the day measured with respect to the sun. It varies from day to day and is about 24 hours.

• All clocks measure the day as a 24 hour period. This is called the mean solar day.

07_08CSKIP?

Solarsiderealground

SolarSiderealspace

Solar DayVs.

Sidereal Day


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Lecture 2: The MoonLecture 2: The Moon

The Moon’s PhasesThe Moon’s Phases• Elongation is the angle of the Moon (or planet) from

the Sun in the sky.• Phases of the Moon - The changing appearance of

the Moon during its cycle are caused by the relative positions of the Earth, Moon, and Sun (different elongations).

• The phases follow the sequence of new Moon, waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third (or last) quarter, waning crescent, back to new Moon.

• Web tool: http://www.calvin.edu/~lmolnar/moon

06-11C

phases

phasePicture

phases2


2020

Waxing Phases

FQ


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Full Moon, Waning Phases and New MoonFM

TQ

NM


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Lecture 2: The Moon Lecture 2: The Moon

Rotation and RevolutionRotation and Revolution

• The rotation and revolution period of the Moon are exactly equal and can be explained by the law of universal gravitation.

• Rotation is the spinning of an object about an axis that passes through it.

• Revolution is the orbiting of one object around another.

06-09C

Scale andRotation

RevolutionRotation


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• The Moon is bright enough to be seen easily in the daytime

• When and where the moon is in the sky is completely determined by the elongation angle (i.e. phase)– EX: a first quarter moon should be crossing the

meridian at sunset• There are certain phase combinations that

cannot be seen at certain times– EX: a waxing crescent high in the sky cannot be

seen at 1 AM– EX: A full moon cannot be seen at noon


When and where can you see the Moon?When and where can you see the Moon?phases2


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The Moon’s PhasesThe Moon’s Phases

• Phase age is the number of days past new (1st Quarter ≈ 7.5 days etc.).

• A sidereal period is the amount of time required for one revolution (or rotation) of a celestial object with respect to the distant stars.

• A sidereal revolution of the Moon takes about 27 1/3 days.

SynodicAndSidereal

phases


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The Moon’s PhasesThe Moon’s Phases

• A synodic period is the time interval between successive similar alignments of a celestial object with respect to the Sun.

• A synodic revolution of the Moon takes about 29 1/2 days

• Lunar month is the Moon’s synodic period, or the time between successive phases (e.g. new moon to new moon): 29d12h44m2s.

SynodicAndSidereal


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EclipsesEclipses

• Eclipses occur when the shadow of one celestial object falls on the surface of another celestial object (solar and lunar eclipses).

• Umbra is the portion of a shadow that receives no direct light from the light source.

• Penumbra is the portion of a shadow that receives direct light from only part of the light source.

EclipseTypes

Anatomyof aneclipse


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Lunar EclipsesLunar Eclipses

Types of Lunar Eclipses• Penumbral lunar eclipse is an eclipse of

the Moon in which the Moon passes through the Earth’s penumbra but not through its umbra.

• Partial lunar eclipse is an eclipse of the Moon in which only part of the Moon passes through the umbra of the Earth’s shadow.

LunarTypes

Geom


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Lunar EclipsesLunar Eclipses

• Total lunar eclipse is an eclipse of the Moon in which the Moon is completely in the umbra of the Earth’s shadow.

• A total eclipse of the Moon is never totally dark because some light is refracted toward the Moon by the Earth’s atmosphere. Most of this refracted light reaching the Moon is red; the blue portion has been scattered out.

Red

Total Lunar

Red

LunarTypes


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Solar EclipsesSolar Eclipses

• Solar eclipse is an eclipse of the Sun in which light from the Sun is blocked by the Moon.

• Total solar eclipse is an eclipse in which light from the normally visible portion of the Sun (the photosphere) is completely blocked by the Moon.

• The corona - the outer atmosphere of the Sun - is visible during a total solar eclipse.

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UmbralWidth

Total

Path

TotalSolar Pic

Types


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Solar EclipsesSolar Eclipses

The Partial Solar Eclipse• Partial solar eclipse: only part of the Sun’s

disk is covered by the Moon.

The Annular Eclipse• Annular Eclipse is an eclipse in which the

Moon is too far from Earth for its disk to cover that of the Sun completely, so the outer edge of the Sun is seen as a ring or annulus.

Annular

AnnularSolar Pic


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Solar and Lunar EclipsesSolar and Lunar Eclipses

• Eclipses does not occur at each full and new Moon because the Moon’s orbital plane is tilted 5° to the Earth’s orbital plane.

• An eclipse season is a time of the year during which a solar and lunar eclipses are possible.

• Only during the two (or three) eclipse seasons that occur each year are the Earth and Moon positioned so that the Moon or the Earth will falls on the other to create an eclipse.

• 1 or 2 solar and 1 or (2 or 0) lunar eclipses occur each eclipse season (maximum of 3 of both types)

• Viewing of eclipses is dependent on observer location (more so for solar than lunar)

NODES

Earth-moon

nodes


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• Upcoming Lunar Eclipses• Total: 2007 Mar 03 (~15:20 PST)• Total: 2007 Aug 28 (~3:40 PDT)• Total: 2008 Feb 21 (~19:30 PST)• Partial: 2008 Aug 16 (~14:10 PDT)

• Upcoming Solar Eclipses• Partial: 2007 March 19 (E. Asia, Alaska)• Partial: 2007 Sept 11 (Southern S. America,

Antarctica)• Annular: 2008 Feb 08 (Antarctica, e Australia, N.

Zealand)• Total: 2008 Aug 01 (ne N. America, Europe, Asia)

Lecture 7: The Earth-Moon SystemLecture 7: The Earth-Moon System

Solar and Lunar EclipsesSolar and Lunar Eclipses

Total Solar

AnnularSolar


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3434


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The Equation of TimeThe Equation of Time

• The correction to get true solar time is done with the equation of time. This is the amount of time added to (or subtracted from) the sun’s time (due to elliptical orbit of Earth).– See Sky Gazer’s Almanac

• The analemma is a graphical representation of this as well.

D-36SKIP

NEXT


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The Length of the DayThe Length of the Day

• The world is divided up into (more than) 24 time zones.

• In most countries Daylight Savings Time (or Summer Time) is used to allow for more daylight hours when most people are active.

• The International Date Line is defined as the position on the earth where the current day ends and the next day begins (add a day traveling west).

Time zones


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• To indicate time internationally (and astronomically), we use one specified (Standard) time zone

• The time zone along the prime meridian is used and the time there is called Greenwich Mean Time (GMT) or Universal Time (UT) or Zulu (Z)

• In the Pacific Standard Time Zone (PST) we are eight hours behind UT PST + 8 = UT– Pacific Daylight Time (PDT): PDT + 7 = UT

• Astronomers use a 24-hour clock (like military time; e.g. 20:00 = 8 pm)


International and Astronomical TimeInternational and Astronomical Time


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The Length of the YearThe Length of the Year

• Many types of years may be defined

• Calendar, Sidereal, Anomalistic, Tropical

How many dayson the calendar?

How long doesit take for the Sun to appear togo around the celestialSphere?

How long is itBetween successiveVernal equinoxes?

How long between successive perihelion passages?


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Observation: The PlanetsObservation: The Planets

• Five planets are visible to the naked eye: Mercury, Venus, Mars, Jupiter, Saturn.

• Planets lack the simple, uniform motion of the Sun and Moon.

• These planets always stay near the ecliptic.

• Mercury and Venus never appear very far from the position of the Sun in the sky. Thus their elongation is small.

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dome


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• The early observers noted several planetary configurations– Opposition: when a planet and Sun appear in the

opposite part of the sky (Elongation = 180°)• Only happens for Mars, Jupiter, Saturn

– Conjunction: when the planet and Sun appear together in the sky (Elongation = 0°)

– Greatest Elongation: when Mercury or Venus reaches a maximum elongation angle during a particular apparition

• The time it took a planet to return to a particular configuration (e.g. conjunction, opposition) was called the synodic period.

InferiorConfigs

SuperiorConfigs


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• Planets sometimes stop their eastward (direct or prograde) motion and move westward against the background of stars. This is called retrograde motion.– Mars, Jupiter, Saturn do this near opposition– Mercury and Venus do this near every other

conjunction– The would be the most difficult motion to

account for when modeling the solar system

D-7

Retrograde

01-20CRetrograde

01-22Ptolemy, Mars

01-23CPtolemy, Mercury and Venus

PtolemaicModel

Looking up into the

sky

CANIS MAJOR

CANIS MINOR

ORION

Procyon

Sirius

Betelguese

Rigel

Winter Triangle Belt

Looking South, 9PM, early February

© Sierra College Astronomy Department1 Clickers! Grab the Clicker which corresponds to your Astro 2...

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Transcript of © Sierra College Astronomy Department1 Clickers! Grab the Clicker which corresponds to your Astro 2...