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Constellations come,
and climb the heavens, and go,
And thou dost see them rise,
Star of the Pole!
and thou dost see them set,
Alone, in thy cold skies,
Thou keep'st thy old unmoving station yet.
Astronomy Picture of the Day
The Constellation Orion
Labeling
Constellation
Bayer System
• Systematic method to name all the stars
that we see.
• Names the brighter stars by assigning :
• 1. constellation (using the Latin
possessive of the name)
• 2. Greek letter (Alpha, Beta, Gamma,
Delta, Epsilon, . . .)
• Labeled in an approximate order of
decreasing brightness for stars in the
constellation.
Bayer System
• Example Orion Constellation
Bayer System
• Example Orion Constellation
• Betelgeuse is also called Alpha-Orionis
• Rigel is called Beta Orionis
Circumpolar Constellations
• Constellations that appear year long in
the sky
• Big dipper
• Little dipper
• Draco
• Camelopardalis
• Cepheus
• Cassiopeia
The Zodiac
• The constellations that fall
on the ecliptic.
Star Charts
and Coordinate Systems
Astronomy Picture of the Day
A Star Cluster in the Rosette Nebula
Astronomy Picture of the Day
This striking pair of galaxies is far, far away ...
about 350 million light-years from Earth.
Astronomy Picture of the Day
The Constellation Orion
The changing stars
• The stars we see change with time of
night and season of year
• The sky is a sphere with Earth at the
center.
• Observer can see only sky above the
horizon
• horizon……..an imaginary plane
tangent to Earth at the observer
Earth and Sky Terms
• Latitude….LINES PARALLEL TO
THE EQUATOR
• Longitude……LINES THAT RUN
FROM POLE TO POLE
• Prime Meridian…RUNS FROM
POLE TO POLE THROUGH…....
• ……….Greenwich England
How do you use latitude and longitude?
1. They are both measured in degrees.
2. Latitude can be no more than 90 degrees and
longitude can be no more than 180 degrees.
3. You always say latitude before longitude (ex.
North West, South East)
4. When talking about only latitude or only
longitude, include the word after the
measurement (ex. 44 degrees latitude, 132
degrees longitude)
Celestial sphere Terms
• North Celestial Pole….same as North
pole
• South Celestial Pole….same as South
pole
• Celestial Equator……….Projection of
earth’s equator out to the sky
• altitude - the angle of a star above the horizon
• The North Star, Polaris, is not the brightest star
in the sky but remains in a fixed position in the
sky.
• The angle of Polaris above your horizon is the
same as your latitude in degrees.
Right Ascension
R.A.
• Distance measured eastward along
the celestial equator from zero
point, called the vernal equinox
• measured in hours and minutes
……. 15hr 10 min, 23 hr, 5 min
Declination
Dec
• Angular distance above or
below the celestial equator
• measured in degrees…. 0o,
15o, 30o
Create own
Celestial Sphere
SC002 Star Chart
• The North Star
• The Big Dipper
• The Little Dipper
• Cassiopeia.
SC001 Star Chart
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Little dipper
Cepheus
Draco
Orion
Gemini
Find the coordinates of Betelgeuse.
Earth and Sky Terms
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Right Ascension
Declination
Ecliptic
Vernal Equinox
Autumnal Equinox
Summer Solstice
Winter Solstice
Motions of the Sun and Stars
• Daily Motion
• Annual Motion.
Motions of the Sun and Stars
• Daily Motion
–The rising and setting of the
stars is caused by the Earth’s
rotation about its axis.
Horizon Calendar
June
(Summer Solstice)
March & September
(Equinoxes)
December
(Winter Solstice)
Stonehenge
Astronomy Picture of the Day
Cosmic wreckage from the detonation of a massive
star is the subject of this official first image from
NASA's Chandra X-ray Observatory.
August 27, 1999
Motions of the Sun and Stars
• Annual Motion
–The Earth’s orbit around the Sun
causes different stars and
constellations to be visible at
different times during the year.
The Ecliptic
• The Sun’s apparent yearly path
among the stars.
• Tip the equatorial circle by 23.5°
around a line passing through the
Earth
Diurnal Motion
rotation of Earth from west to east
causes objects on celestial sphere to
appear to rise in east and set in west
daily
Solar Day
• The time it take for the earth to
make one complete rotation
• Takes 24 hours
Sidereal Day
• One rotation of the earth measured by
the position of the stars
• It takes 23hours 56 minutes
Seasons
• What causes seasons on Earth?
• Answer: The tilt of the Earth's
rotational axis.
• Ecliptic: The path of our Sun
across the celestial sphere is
called the.
• It is inclined 23½° with respect
to the celestial equator.
Earth and Sky Terms
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Right Ascension
Declination
Ecliptic
Vernal Equinox
Autumnal Equinox
Summer Solstice
Winter Solstice
Inclined Pole causes Seasons