Solar System Laboratory Fall 2006

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Solar System Laboratory Fall 2006

• CSI Astronomy 101
• Midterm Review
• Tuesday Sections 3310 3321 - A.V. Ketterer

Image Credit NASA JPL
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Star Finder
Which star are the other stars circling?
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The Star and Planet Locator (A two dimensional
view of the sky)
Overhead point, Is in the
middle of the sky.
Zenith,
South
A
Our horizon
Z
East
West
Brass tack, the North Star.
North
Date
9 pm mid-September
Note the star that all the stars are circling and
the direction, ccw, rising in the East.
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zenith
Overhead point,
(on the celestial meridian
South
midway between N and S)
A
Our horizon
Z
East
West
Brass tack, the North Star.
North
Date
9 pm mid-September
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Ecliptic
Annual path of the Sun
zenith
Celestial Meridian
Overhead point,
(on the celestial meridian
South
midway between N and S)
Celestial Equator
A
Our horizon
Z
East
West
Brass tack, the North Star.
North
Date
9 pm mid-September
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Dubhe
Merak
North
Looking north about 900 p.m. EDT September 9
Draw the pointer stars, Dubhe and Merak 6 hours
later, 300 a.m. September 10.
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Dubhe
Merak
North
Looking north about 300 a.m. EDT September
10 The stars have moved about 6/24 or 1/4 of the
way around the sky. This is due to the daily or
diurnal rotation of the Earth.
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Dubhe
Merak
North
Again, we looking north about 900 p.m. EDT
September 9
Draw the pointer stars, Dubhe and Merak 4
months, 1/3 of a year, later, at 900 p.m.
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Dubhe
Merak
North
Now we looking north about 4 months later at
'900 p.m.' on January 9th.
The stars have moved in our sky about 1 counter
clockwise/day due to Earth's revolution.
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Use your star finder to determine when Regulus in
Leo rises on July 15th. Along which line on
the star finder would we have to look find
Leo? Where must we place Regulus to determine
its rise time? What asterism is found in Leo?
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Math Lab
How many centimeters in a meter? How many
millimeters in a meter? How many meters in a
kilometer? How many centimeters in 8.7
meters? How many millimeters? How many kilometers?
100 cm/meter 1000 mm/meter 1000 m/km 870
cm 8700 mm .0087 km
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Scientific Notation
Powers of 10
1,000,000,000,000 1012 one trillion
tera 100,000,000,000 1011
10,000,000,000 1010 1,000,000,000
109 one billion giga
100,000,000 108 10,000,000
107 1,000,000 106
one million mega 100,000
105 10,000 104
1,000 103 one
thousand kilo 100
102 10 101 1 100
one 10-1 .1 deci 10-2
.01 centi 10-3
.001 milli 10-4 .0001 10-5
.00001 10-6
.000001 micro 10-7
.0000001 10-8 .00000001 10-9
.000000001 nano 10-10
.0000000001 10-11
.00000000001 pico 10-12
.000000000001
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Scientific Notation
In astronomy we deal with the very large and the
very small. To write these numbers with
excessive zeroes 5.2 Au x 150,000,000 km/AU
780,000,000 km We write the number as a number
between 1 and 10 x the
appropriate power of 10 780,000,000 km 7.8 x
108 km G the gravitational constant
.0000000000667 Nm2/kg2
6.67 x 10-11 Nm2/kg2
Move the decimal point of the original number
so that it is to the right of the first
non-zero digit. Rewrite the number with the
appropriate number of digits. Count the number
of places you moved the decimal point. This is
the exponent of 10. But - If you moved
the decimal point to the right, i.e. the number
was less than 1, then place a negative on
the exponent. - If you moved the decimal
point to the left, I.e. the number was greater
than 1 then use the exponent without a
sign. (A positive exponent is then implied.)
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Write 72,837.552 in Scientific Notation
Write the number as a number between 1 and 10
times the appropriate power of 10 1 - Place
a decimal point after the first non-zero number
7.2837552
2 - The decimal point has been moved 4 places to
the left. So the appropriate power of 10 is
4 or 104.
7.2837552 x 104 If we round to 2 places 7.28 x
104
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Write .0000493741 in Scientific Notation
Write the number as a number between 1 and 10
times the appropriate power of 10 1 - Place
a decimal point after the first non-zero number
4.93741
2 - The decimal point has been moved 5 places to
the right. So the appropriate power of 10
is -5 or 10-5.
4.93741x 10-5 If we round to 2 places 4.94 x
10-5
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Scale
Real World Value
Scale
Measured Value
Moons real world diameter is 2,160 miles In
this diagram the scale Scale
360 miles/cm or we say 1 cm 360 miles

2,160 miles
6 cm
6 cm
1.5 cm x scale 1.5 cm x 360 miles/cm 540 miles
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Earth, Sun and Moon

• Trippensee Planetarium

Vernal Equinox March 21
Summer Solstice June 21
Winter Solstice December 21
Autumnal Equinox September 22
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Earth's Basic Motions
Rotation, daily or diurnal motion
Revolution, yearly or annual motion
also Earth's tilt, obliquity, changes, as does
the shape of Earth's orbit
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The Earth Revolves Around the Sun with
its Axis Tilted
What do we notice about the tilt of Earth's
axis as the Earth travels around the Sun?
Vernal Equinox March 20
Summer Solstice June 21
Winter Solstice December 21
Autumnal Equinox September 22
And what do we notice about the tilt of Earth's
axis with respect to the Sun, as the Earth
travels around the Sun?
Our Seasons are a result of the tilt of Earths
axis!
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Winter in the Northern Hemisphere Winter
Solstice December 21
North Pole
The ecliptic
Earths equator
The Tropic of Capricorn is the is the most
southerly point where the Sun can appear
overhead. The Tropic of Capricorn is the
southern boundary of the tropics and the
Tropic of Cancer is the northern boundary.
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At the Equinoxes
If the northern axis is pointing toward us, it is
the autumnal equinox, if away then it is the
vernal equinox.
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Pisces
Aquarius
Aries
Capricorn
Sagittarius
September
October
August
November
Taurus
July
December
June
January
May
Scorpio
February
April
March
Gemini
Cancer
Libra
Leo
Virgo
What constellation is the SUN in at the end of
March, beginning of April?
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Pisces
Aquarius
Aries
Capricorn
Sagittarius
September
October
August
November
Taurus
July
December
June
January
May
Scorpio
February
April
March
Gemini
Cancer
Libra
Leo
Virgo
What constellation is the SUN in at the beginning
of our Summer, June 21st?
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Celestial Globe
North Celestial Pole
Summer Solstice June 21
Vernal Equinox
Celestial Equator
Autumnal Equinox
Ecliptic
Winter Solstice December 21
We measure north and south from the celestial
equator on the celestial globe - declination,
Dec, which is given in degrees We measure
eastward from the vernal equinox (where the
Sun Crosses the celestial equator going north)
along the celestial equator - right ascension, R
A, is given in hours, minutes and seconds.
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Celestial Globe
North Celestial Pole
Sun at mid-February The Sun's position
on the ecliptic sets the date. The
Sun's position in the sky sets the
time. We compare the Sun's position
with the horizon ring.
Vernal Equinox
Summer Solstice June 21
Celestial Equator
Autumnal Equinox
Winter Solstice December 21
Ecliptic
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• Altitude and Azimuth
• measured relative to our position on the Earth
• along the horizon ring on the celestial globe

Altitude, height of an object (the star in this
case) above the horizon. The zenith has an
altitude of 90.
Z
Altitude

W
N
S
E
Azimuth
Horizon Ring We measure Azimuth here.
Azimuth is measured in degrees along the
horizon from the north, eastward. North is 0
azimuth East is 90, South is 180 and West is
270
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Orbits of the Planets, Asteroids and Comets
Keplers 1st Law tells us that The orbits of the
planets are ellipses with the Sun at one focus.
Perihelion, P Closest point
Sun
Aphelion, A Farthest point
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Orbits of the Planets, Asteroids and Comets
Keplers 1st Law tells us that The orbits of the
planets are ellipses with the Sun at one focus.
Ellipse
eccentricity - e
foci


e
F
2
2a
major axis 2a a sem-major axis
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The closer the eccentricity is to 0 the closer
the ellipse is to a circle.
Pluto e ..2484
Sedna e .73
A circle has e 0
A straight line e 1 and is a degenerate
parabola
A parabola e1
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Note The sum of the distances from
the foci to the planet (anywhere on

the ellipse is 2a.
empty focus
F
F
2
1
Perihelion, P
Aphelion, A
Distance between the 2 foci
major axis
semimajor axis,
a
semimajor axis,
a
Also we can write
By definition
A - P 2ae
eccentricity, e

from the definition of eccentricity
2a
Adding the above equation to
Observe Dividing the 2
equations
A P 2a -gt
A a(1e) and if
and substituting
e, yields

A - P
we subract we obtain

P a(1-e)
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Although the Orbits of the Planets are
Ellipses, sometimes we can use a
circle to approximate the ellipse (draw a
circle with the center on the Sun, and so Sun
centered)
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Properities of Lenses and a Refracting Telesope
Determining the focal length of a lens
1 1 1 f
do di
The focal length, f, of a lens is given by the
formula


di
distance from lens to the object distance from
the lens to the image
do
di
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Properities of Lenses and a Refracting Telesope
Determining the focal length of a lens
1 1 1 f
do di
What happens when the object is very, very far
away?


or f di
di
This is what we will verify in the first part of
the Lab!
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Properities of Lenses and a Refracting Telesope
Magnification of a Lens
di
hi
ho
hi
Magnification
ho
We will also verify this magnification
equality. Magnification can be gt 1 or lt 1.
NOTE In our case the object is only the bulb,
itself!
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Properties of Lenses and a Refracting Telescope
Part 2 - Building a Telescope

• Building the telescope.
• Magnification of the telescope can be expressed
  as
• fobjective
• 
  f eyepiece