Charting the Heavens Day 2 Going to the Stars Road at Logan Pass, Glacier National Park. This...

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

SIRIUS

BetelgeuseAldebaran

Rigel

Using Orion in to find other objects

Sirius

Aldebaran

Pleiades

Great Orion Nebula

Pleiades

SevenSisters

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 SignROUGHLY, 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

horizon

star

altitude

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

http://upload.wikimedia.org/wikipedia/commons/2/21/Zirkumpolar_ani.gif

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

inverted mixing bowl ….

Consider the dome of the sky over our heads….

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


North Star

Star A

Star B

1

1

3

3

2

2

4

4

Earth’s Equator

Figure 1

Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

Figure 2

Horizon

Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

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?

Can the observer shown see an object located below the horizon?

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?

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?

In what direction is the

observer facing?

1. toward the South2. toward the North3. toward the East4. toward the West

Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

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. high in the northern skyB. high in the southern skyC. high in the western skyD. directly overhead

Where would the observer

look to see the star indicated by

the arrow?

A. High in the NortheastB. High in the SoutheastC. High in the Northwest D. High in the Southwest

Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

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 MotionThe 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?


Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

Figure 2

Horizon


• 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?


• Imagine looking toward the North. What do stars appear to do over the course of an evening?


Celestial Sphere



Celestial Sphere

Star A

Star B

1

1

3

2

2

4

4

3

Figure 2

Horizon


• Looking North: Stars appear to move counter-clockwise 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.

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