Key Ideas:

Daily motions Reflection that the Earth"s day-to-day Rotation Circumpolar StarsAnnual motions Reflection that the Earth"s Orbital motion Ecliptic: The path of the sun Zodiacal Constellations Solstices & Equinoxes

Daily Motions

Objects in the sky appear to increase in the east and collection in the West eachday. This evident daily motion is a enjoy of the Earth"s rotationabout the axis. Planet rotates once a job (24 hours) The feeling of rotation is Eastward facing North, rotation is towards the Right.

You are watching: Diurnal motion of objects in the sky is caused by the

Apparent Paths

The apparent Paths the objects space parallel come the CelestialEquator.Their orientation depends on your latitude: in ~ Equator: perpendicular to the horizon at Poles: parallel come the horizon Mid-Latitudes: Tilted by (90�–Latitude)
(Click top top the picture to watch it in color at fullresolution )In Columbus: we space at 40� N, for this reason the courses are tilted by 50 degreesfrom the horizon.

Circumpolar Stars

Any star closer 보다 your latitude to her visible celestial pole (northor south) will always be above
your local horizon.These room the Circumpolar Stars Ursa Major, Ursa Minor, & Draco are circumpolar constellations as viewed from Columbus
(Click top top the image to see it in shade at complete resolution )The the opposite pole"s circumpolar stars never ever rise over your horizon. Ursa significant never rises because that latitudes south of about 40° S

Summary of day-to-day Motions:

Daily activities of celestial objects reflect the Earth"sdaily rotation about its axis: Celestial objects to appear to increase in the east and set in the West. Noticeable daily courses are parallel come the Celestial Equator. The inclinations of these paths loved one to the horizon relies on the observer"s latitude. Circumpolar objects are those always over or below the regional horizon.

Annual movement of the Sun

Over the course of a year, the Sun shows up to relocate a little towards theEast each day together seen through respect to the background stars. This dailyeastward drift is This noticeable motion is a have fun of the Earth"s yearly orbitaround the Sun.

The Ecliptic

The Ecliptic is the apparent path that the Sun family member tothe stars. Good Circle projected ~ above the Celestial round Tilted by roughly 23.5° from the Celestial Equator
(Click top top the image to see it in color at full resolution )This tilt is referred to as the Obliquity the the EclipticThe Obliquity the the Ecliptic varies between 21.2 and also 24.5° witha approximately 41000 year period:Now (2007 Sept 26): the is 23° 26" 17.826"In 2000 it to be 23° 26" 21.448"

The Zodiac

As the sun moves follow me the Ecliptic as checked out from Earth, that passesthrough 12 ancient constellations recognized as the Zodiac. Plenty of date from Babylonian times. These are acquainted from astrological lore: Aries, Pisces, Aquarius, Capricorn, Sagittarius, Scorpius, Libra, Virgo, Leo, Cancer, Gemini, and Taurus.The Zodical Constellations deserve to be offered as a type of an astronomicalcalendar: watch which Zodiacal constellation is the highest possible (on your celestial meridian) in ~ midnight. The sun is in the opposite constellation.
(Click ~ above the picture to check out it in shade at fullresolution , inspired by a drawing by Nick Strobel)A Note around the Zodiac:The amount of time the sun spends in the an ar of a details Zodiacalconstellation does not, in fact, correspond to the calendar datesassociated with the twelve "Sun Signs" in the newspaper andmagazine astrology columns. This is no accident. Together we will see in great 7, the celestial equator slowlymoves ("precesses") roughly the sky when every 26,000 years. This meansthat the celestial location of the Sun throughout a offered month this day hasmoved substantially since the common astrological legacies werecodified by Ptolemy during the 2nd century AD. In fact, follow tothe constellation borders established through the IAU in 1888, at thepresent time the sun actually passes through 13 constellationsover the course of a year! In so late November the sunlight crosses over thenorthern component of Scorpius for around 5 days, after which it overcome intothe constellation that Ophiuchus till mid-December. Ophiuchus is, ofcourse, not one of the classic 12 constellations the the Zodiac. Theamount that time the sun spends in a constellation is also quite variable,and nowhere close to the uniform time intervals argued by traditionalastrology. When both and also astrology share usual roots in thedistant past, they be affected by each other no relation to each various other today. Astrology asnow practiced has actually strayed much from the reality clearly visible in thenight sky.


Solstices occur when the sun is at its preferably northern and also southerndeclination. Words Solstice is acquired from the Latin words"sol sistere" = "sun" and"stand still".Solstices happen twice a year in June and also December:Summer Solstice
: best northern declination that the sun (June).Winter Solstice: preferably southern declination the the sun (December).These names room ambiguous, as while in June that is Summer in the NorthernHemisphere, that is Winter in the southerly Hemisphere (and similarlyflipped during December). You may occasionally check out these referred to as the"June" and "December" Solstices, respectively, in an attempt to no havea "Northern" bias, but this alternative is not commonly used.


Equinoxes take place when the sunlight crosses the Celestial Equator. Derivesfrom the latin "equinoctis" = "equalnight".Equinoxes occurs double a year, during March and September.Vernal Equinox: sun crosses the Celestial Equator movingNorth (occurs in March)Autumnal Equinox: sunlight crosses the Celestial Equator movingSouth (occurs in September)Like with the Solstices, over there is a comparable North/South faint intheir connected seasons. In this case, however, the usage of the latinatenames (Vernal instead of Spring), signifies the we room using a strictastronomical an interpretation that is agreed top top worldwide.

Length of the Day

The length of the day depends on the place of the sunlight along theEcliptic.

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(Click top top the photo to see it in color at full resolution )Vernal & autumnal Equinoxes:Occur in March and September, respectively.The sunlight rises early East and sets due West. Day and also Night have equal lengths (12 hours each).Summer Solstice:Occurs in JuneThe sun rises in the Northeast, and also sets in the NorthwestDay is longer than Night in the north HemisphereDay is shorter 보다 Night in the southerly HemisphereWinter Solstice:Occurs in DecemberThe sun rises in the Southeast, and sets in the SouthwestDay is shorter 보다 Night in the north HemisphereDay is longer 보다 Night in the southern Hemisphere

Summary of yearly Motions: