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Charting the Heavens
Day 2
Going to the Stars
Road at Logan Pass,
Glacier National Park.
This picture shows
our view of the Milky
Way in the night sky.
Constellations – the 88 semi-rectangular
regions that make up the sky
• Northern constellations have Latinized
Greek-mythology names:
– Orion, Cygnus, Leo, Ursa Major, Canis Major, Canis
Minor
• Southern constellations have Latin names:
– Telescopium, Sextans, Pyxsis
Use the Summer Triangle to find constellations
during summer evenings
Use the winter
triangle to find
constellations
during winter
evenings
Anyone recognize any shapes here?
Star Names
Betelgeuse
Aldebaran
Rigel
SIRIUS
Using Orion in to find other objects
Pleiades
Aldebaran
Great Orion Nebula
Sirius
Pleiades
Seven
Sisters
Subaru
Use the
Big
Dipper in
the
northern
sky as a
way to
find other
groups of
stars
Astrology: The belief that the
positions of the stars and planets as
seen from Earth impact human
events.
Turn to your
neighbor
and discuss
what
Astrological
sign you
have been
told you are.
Sun signs
• Are based on which constellation
the sun was on the day of your birth
• Moon sign: which constellation is
the moon in at the time of your
birth
• Most astrological signs are
incorrectly shown because they
are based on your birth where the
sun was during Greek times.
Your Birth Sign
ROUGHLY, it is the constellation that the Sun is
covering up during the day you are born if you
were born 2000 years ago.
Ophiucus
•
•
•
•
•
The thirteenth zodiac sign
Sun passes through Ophiucus’ foot
November 30-Dec. 18
He is the serpent bearer
also used as the medical symbol
Local co-ordinate systems
• Based on the objects above the plane of the
horizon
– Altitude is the angle above the horizon
star
altitude
horizon
NORTH STAR HAS AN ALTITUDE OF 0° IF YOU ARE ON THE EQUATOR
THE ALTITUDE OF THE NORTH STAR=YOUR LATITUDE ON EARTH!!!
Altitude
• NORTH STAR HAS AN ALTITUDE OF 0° IF YOU
ARE ON THE EQUATOR
• THE ALTITUDE OF THE NORTH STAR=YOUR
LATITUDE ON EARTH!!!
A ROUGH WAY TO ESTIMATE ALTITUDE
• PINKY =1°
• 3 FINGERS=3°
• FIST = 10°
Figure out the altitude of the American flag in
the room.
How about the globe in the back of the room?
Local Co-ordinate System
• Azimuth – starts with north a 0° and south is
180°
• Zenith is 90°
zenith
North Star
• Even though Polaris is currently the North star,
it doesn’t lie due North –and eventually will
move and Vega will be our North Star, Why do
you think this is happening? Discuss with your
elbow partner, write down your thoughts on
your white board, be ready to defend them.
The North Star
• Polaris, our current North Star is the 49th
brightest star in the night sky!!!!!
• To find it, locate the cup of the Big Dipper to
the handle of the Little dipper.
• It doesn’t appear to move in the night sky but
the other stars rotate around it
• North pole and Polaris are about 1° off from
one another
CIRCUMPOLAR STARS
• STARS THAT NEVER GO BELOW THE HORIZON
– CAN ALWAYS BE SEEN AT NIGHT
– http://upload.wikimedia.org/wikipedia/commons
/2/21/Zirkumpolar_ani.gif
Earth’s Orbital Motion: what causes the North
star to change?
Precession: rotation of Earth’s axis itself; makes one complete
circle in about 26,000 years
With your table group try
out the top, how does the
top model precession?
Precession
• Wobbles in a 26,000 year cycle
• Wobble is between Polaris, Vega and Thuban
• Changes the position of the Vernal Equinox
which will also change the co-ordinates of the
stars
Celestial Sphere
The celestial sphere:
Stars seem to be on the inner surface of a
sphere surrounding the Earth
They aren’t, but they can use two-dimensional
spherical coordinates (similar to latitude and
longitude) to locate sky objects
Celestial Coordinates
Right Ascension
• Like longitude
• Use units of time-hours
instead of degrees
• 0 hour is the vernal equinox
Declination
• Like latitude except use +/instead of north and south
Terms related to the Celestial Sphere
Terrestrial System
• South Pole
• North pole
• Equator
• Latitude
– 0° at the Equator
• Longitude
– 0° at the Prime Meridian
Celestial System
• South Celestial Pole
• North Celestial Pole
• Celestial Equator
• Declination
0° at celestial Equator
• Right Ascension
– 0 Hours at Vernal Equinox
Angular Measure: A way to describe the amount
of sky a celestial body takes up
• Full circle contains 360°
(degrees)
• Each degree contains 60′
(arc-minutes)
• Each arc-minute contains 60′′
(arc-seconds)
• Angular size of an object
depends on its actual size and
distance from viewer
What do you think?
• Do the stars stay in the same position in the
sky all day/night long?
• Do we see the same stars all year round
every night?
What do you think?
• What causes the stars move?
• Do the stars actually move in the way they
appear from Earth?
• Is the daily motion of the Sun different from
the stars?
Consider the dome of the sky over our heads….
mixing bowl
Consider the dome of the sky over our heads….
inverted mixing bowl ….
Imagining a
spinning
Celestial Sphere
surrounding
Earth aids in
thinking about
the position and
motion of the
sky
Imagining a spinning Celestial Sphere
surrounding Earth aids in thinking about
the position and motion of the sky
Animation!
Celestial Sphere Rotation
Celestial Sphere Rotation
Star B
Star B
2
2
Star A
Star A
North Star
1
2
1
2
Celestial Sphere
Celestial Sphere
3
3
1
1
4
4
3
3
Earth’s Equator
4
4
Celestial Sphere
Rotation
Celestial Sphere
Rotation
Figure 1
Figure 2
Horizon
Is the horizon shown a real
physical horizon, or an
imaginary plane that extends
from the observer and Earth
out to the stars?
Celestial Sphere Rotation
Star B
2
Star A
1
Can the observer shown see
an object located below the
horizon?
2
Celestial Sphere
Celestial Sphere
3
1
4
3
Is there a star that is in an
unobservable position?
When a star travels from
being below the observer’s
horizon to being above the
observer’s horizon, is that
star rising or setting?
4
Celestial Sphere
Rotation
Figure 2
Horizon
Tutorial: Position – p.1
• Work with a partner
• Read the instructions and questions carefully
• Talk to each other and discuss your answers with
each another
• Come to a consensus answer you both agree on
• If you get stuck or are not sure of your answer ask
another group
• If you get really stuck or don’t understand what the
Lecture Tutorial is asking as one of us for help
Did you get the Key Ideas from the Position
Lecture Tutorial?
Celestial Sphere Rotation
Star B
In what
direction is the
observer
facing?
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
4
1.
2.
3.
4.
toward the South
toward the North
toward the East
toward the West
Celestial Sphere
Rotation
Figure 2
Horizon
Imagine that from your current location you
observe a star rising directly in the east. When
this star reaches its highest position above the
horizon, where will it be?
A.
B.
C.
D.
high in the northern sky
high in the southern sky
high in the western sky
directly overhead
Celestial Sphere Rotation
Where would
the observer
look to see the
star indicated by
the arrow?
A.
B.
C.
D.
High in the Northeast
High in the Southeast
High in the Northwest
High in the Southwest
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
4
Celestial Sphere
Rotation
Figure 2
Horizon
Motion
Earth’s Orbital Motion
• Daily cycle, noon
to noon, is
diurnal—solar day and is based on
the sun’s position.
• Stars aren’t in quite the same
place 24 hours later, though, due to
Earth’s rotation around Sun; when
they are once again in the same
place, one sidereal day has passed
SEASONAL CHANGES IN OUR NIGHT
SKY
• Summer triangle: Vega, Denab, Altair
• Winter: Orion, Sirius (Dog Star)
• The change occurs about 1°/night
Earth’s Orbital Motion
Seasonal changes to night sky are due to Earth’s motion around Sun
Earth’s Orbital Motion
The Twelve constellations (some say thirteen) that the Sun moves through during the
year are called the zodiac; The view of the night sky changes as Earth moves in its orbit
about the Sun. As drawn here, the night side of Earth faces a different set of
constellations at different times of the year. The 12 constellations named here make up
the astrological zodiac.
Earth’s
rotation
causes the
Sun, Planets,
Moon and
stars to
appear to
move when
viewed from
Earth
Nightly Motion of the Stars
• Imagine looking toward the East as a star rises
above your horizon - what does it do after
that?
Nightly Motion of the Stars
Celestial Sphere Rotation
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
4
Celestial Sphere
Rotation
Figure 2
Horizon
Nightly Motion of the Stars
• For stars (the Moon and planets) that appear
in the southern sky: Stars first rise near the
eastern horizon, move upward and toward
the south, and then move down and set near
the western horizon.
What direction
is the observer
facing in this
picture?
Nightly Motion of the Stars
• Imagine looking toward the North.
What do stars appear to do over the
course of an evening?
Nightly Motion of the Stars
Celestial Sphere Rotation
Star B
2
Star A
1
2
Celestial Sphere
Celestial Sphere
3
1
4
3
4
Celestial Sphere
Rotation
Figure 2
Horizon
Nightly Motion of the Stars
• Looking North: Stars
appear to move counterclockwise around the
stationary North Star
(Polaris) – we call these
circumpolar stars.
Looking North: Circumpolar Stars
– Circumpolar stars seem to move counter-clockwise
around the stationary North Star.
– These constellations and stars are visible any night of
the year in the NORTHERN sky because they never rise
or set!
– Examples: Ursa Major, Ursa Minor, Draco, Cepheus, and
Cassiopeia
What happens over time in the Northern
Sky?
Tutorial: Motion – p. 3
• Work with a partner!
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one
another.
• Come to a consensus answer you both agree on.
• If you get stuck or are not sure of your answer, ask
another group.
• If you get really stuck or don’t understand what the
Lecture Tutorial is asking, ask one of us for help.