Credit/Permission: For text, © David Jeffery. For figures etc., as specified with the figure etc. / Only for reading and use by the instructors and students of the UNLV astronomy laboratory course.
This is a lab exercise with observations. The observations can be dropped if necessary since the lab exercise can be made sufficiently challinging without them. For the observations, see Sky map: Las Vegas: current time and weather.
Sections
The main focus is on planets as astronomical objects in the old-fashioned sense: i.e., astronomical objects as seen on the sky and their orbits. We are NOT much concerned with their internal structure (e.g., with planetary geology and planetary atmospheres).
We touch on the following topics:
Some of the
Tasks can be completed ahead of the lab period.
Doing some of them ahead of lab period would be helpful.
However, you can print a copy ahead of time if you like especially if
want to do some parts ahead of time.
You might have to compensate for updates in this case.
The Lab Exercise itself is NOT printed in the lab ever.
That would be killing forests
and the Lab Exercise is designed to be an active web document.
General remarks about quiz prep are given at
Quiz Preparation: General Instructions.
For DavidJ's lab sections, the quiz prep is doing all the items listed here and self-testing with the
Prep Quizzes and Prep Quiz Keys
if they exist.
Review the parts of the
Celestron C8 telescope
in the figure below
(local link /
general link: telescope_c8_diagram.html).
You should also review the
Observation Safety Rules.
However to complement and/or supplement the reading, you should at least
read the intro of a sample of the articles
linked
to the following keywords etc.
so that you can define and/or understand some keywords etc. at the level of our class.
A further list of keywords which you are NOT required to look at---but it would be useful to do so---is:
The sky alignment
on the telescopes
may NOT needed if the students are only going to make quick sketches.
However, if you are going to larger
telescope magnification than
provided by the 40-mm eyepieces,
sky alignment is probably a good idea.
So section Exoplanets (Optional at the discretion of the instructor)
php require("/home/jeffery/public_html/astro/mars/mars_full_2.html");?>
Do the preparation required by your lab
instructor.
php require("/home/jeffery/public_html/astro/ancient_astronomy/euclid.html");?>
php require("/home/jeffery/public_html/astro/telescope/telescope_c8_diagram.html");?>
Keywords:
Celestron C8 telescopes,
conjunction
(inferior conjunction and
superior conjunction),
elongation
(greatest eastern elongation and
greatest western elongation),
exoplanet,
Kepler's 3 laws of planetary motion,
naked-eye astronomy,
opposition,
planets
(Mercury,
Venus,
Earth,
Mars,
Jupiter,
Saturn,
Uranus,
Neptune,
ex-planet Pluto,
inner planets,
outer planets,
inferior planet,
superior planet),
planetary configuration,
planetary system,
quadrature,
Solar System,
synodic period,
syzygy,
TheSky
(TheSky6,
TheSkyX,
List of Tricks for TheSky,
TheSky Orientation),
transit method.
Hm.
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EOF
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End of Task
However, there were still special APPARENT arrangements that were obviously important in determining those arrangements and motions of the planets. Wrong models were used in determining the arrangements and motions, and those arrangements and motions were determined, NOT surprisely, wrongly.
The special apparent arrangements are the planetary configurations. They and related items are part of ancient astronomy lore that everyone should know.
Since the advent of the heliocentric solar system, the correct 3-dimensional space arrangements that create the planetary configurations have also been known.
In this section, we consider the planetary configurations themselves and related items.
In the 2 sections below (i.e., Determination of Orbital Periods (Optional at the discretion of the instructor) and Determination of the Mean Orbital Radii), we consider how planetary configurations are used to determine orbital periods and mean orbital radii for the planets in the Solar System.
Apparent retrograde motion occurs at the time of the planetary configuration inferior conjunction for inferior planets and at the time of the planetary configuration opposition for superior planets.
Apparent retrograde motion is explained and illustrated in the figure below (local link / general link: apparent_retrograde_motion.html).
Planetary configurations
are defined
and the most important ones
are displayed in the figure below
(local link /
general link: planetary_configurations.html).
Complete the following short
definitions
in complete sentences in your own words.
Read the definition or explanation from some source,
think about what it means, and then formulate your own version.
Sub Tasks:
Complete this task using the
planetary configuration simulator
shown in the applet figure below
(local link /
general link: naap_planetary_configurations.html).
in the group must do this
task for themselves.
Sub Tasks:
php require("/home/jeffery/public_html/astro/celestial_sphere/apparent_retrograde_motion.html");?>
php require("/home/jeffery/public_html/astro/celestial_sphere/planetary_configurations.html");?>
php require("/home/jeffery/public_html/astro/applet/naap_planetary_configurations.html");?>
Sub Tasks:
Then check out the
List of Tricks for TheSky:
Solar System Tricks (i.e., item 18)
which tells you how to do some of the things we have to do tonight.
Usually, the 3D Solar System Model will just come up in this orientation.
If NOT, use the
Tricks (item 18)
to find out how to get it.
If some inner Solar System
planets are turned off,
you must turn them on using the
button menu with Display Explorer.
See
List of Tricks for TheSky:
Solar System Tricks (i.e., item 18.1).
If you don't want to print after seeing the Preview, go
Toolbar/Close.
Sub Tasks:
By nearest
"planetary configuration",
we mean the
planetary configuration
nearest to today's
elongation just approximately.
You'll need to know that the
greatest elongations
for Mercury and
Venus are, respectively, 18--28°
and 45--47°
(see Wikipedia: Elongation).
There is a range of greatest elongations
since the orbits are NOT exact circles.
EOF
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_______________________________________________________________________________________
Table: Elongations and Nearest Planetary Configurations:
For today, right now.
_______________________________________________________________________________________
Planet Elongations Nearest Planetary Configuration
(degrees,E/W) (e.g., opposition, quadrature, etc.)
_______________________________________________________________________________________
Mercury
Venus
Mars
Jupiter
Saturn
_______________________________________________________________________________________
Complete this task using the Ptolemaic System Simulator shown in the applet figure below (local link / general link: naap_ptolemaic_system_simulator.html.html) after this task.
in the group must do the task for themselves.
Sub Tasks:
The Ptolemaic system
was NOT the uniquely good geocentric
epicycle system---many roughly equally good
geocentric epicycle systems were developed in the
centuries
after Ptolemy (c.100--c.170 CE).
After reading the caption with
Ptolemaic System Simulator
(which is given above), discuss
whether or NOT Ptolemy should
have been aware of the non-uniqueness problem of
geocentric
epicycle systems
and what might a modern scientist
conclude about the geocentric
epicycle theory
from the non-uniqueness problem.
Remember that the Ptolemaic system
was worked out in great detail by Ptolemy,
and so he spent a lot of time devising its particular
epicycle orbits.
The full Ptolemaic system
is displayed in the cartoon below.
Was the fact that
the inferior planets
exhibit an apparent oscillation around the Sun's position on the
sky (see the figure above
(local link /
general link: ptolemy_system.html)
and
the Ptolemaic System Simulator
in the applet figure below
(local link /
general link: naap_ptolemaic_system_simulator.html.html)
a clue to
good old Ptolemy? Discuss.
HINT: You might consider what happens in the
Tychonic system
and the Copernican system.
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php require("/home/jeffery/public_html/astro/ptolemy/ptolemy_system.html");?>
The Copernican Revolution was started by its eponym, Copernicus.
Nicolaus Copernicus (1473--1543) was the first person to put into recorded history the heliocentric solar system as a well supported hypothesis. The qualification is "well supported hypothesis" is necessary and important.
Sub Tasks:
Sub Tasks:
Have you read it?     Y / N
   
Unfortunately, Copernicus never makes that
completely explicit it seems.
He certainly thought of it as a major argument.
Retrospectively, it clearly is the main argument.
Now Copernicus could NOT
measure absolute distances beyond the
Moon.
No one could until the 17th century
(see Wikipedia: Astronomical unit: History).
So how could Copernicus
get the correct order and correct relative orbital radii of
planets or as he put it
"form of the universe".
HINT: The short answer is expected.
From the heliocentric solar system model,
Nicolaus Copernicus (1473--1543) was able to
predict the mean orbital radii
of the planets in their
orbits around the
Sun.
On the other hand,
from the (geocentric)
Ptolemaic system,
Ptolemy (c.100--c.170 CE)
was NOT able to predict the locations of the
planets in
space, NOT even their
order going outward from the Earth.
He was able to make such predictions with
extra hypothetical as detailed in his
Planetary Hypotheses---but let's
NOT consider those predictions and hypothetical
since they go beyond the basic
Ptolemaic system.
Discuss which scientific theory is better---the
heliocentric solar system model or
the Ptolemaic system---from
the point of view of modern science,
but without knowing which is right.
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... the chief thing, that is the form of the universe and the clear
symmetry of its parts.
This quote suggests that Copernicus
thought that the deduced structure of the Solar System
(which he thought of as being the whole
universe or
whole cosmos)
was the main argument for heliocentrism.
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The 3 laws are now understood as consequences of Newton's laws of motion and Newton's law of universal gravitation.
Kepler's 3 laws of planetary motion are illustrated in the 2 figures below (local link / general link: kepler_all_3_laws.html; local link / general link: kepler_2nd_law.html).
Complete this task using the
planetary orbit simulator
in the applet figure below
(local link /
general link: naap_planetary_orbit_simulator.html)
after this task.
in the group must do the task for themselves.
Sub Tasks:
Have you read it? Y / N
The Kepler's 3rd Law
is somewhat explicated in the figure below
(local link /
general link: kepler_3rd_law.html).
Kepler's 3rd law
is an example of
power law---a function relationship in which one
variable varies as a power another variable.
Power law are quite common and are often displayed
on log-log plot, where they form lines.
Say we have power law y = a*x**p, where p is a general
power.
If we take the logarithm
of both sides we get log(y) = log(a) + p*log(x)
which is a linear relation for log(y) and log(x).
The slope is power p
and the y-intercept is log(a).
On a log-log plot, the axes are scaled
to take the logarithm automatically.
The tick marks are separated by powers of 10 and NOT fixed amounts.
So one often just says "power laws
are linear on log-log plots.
See the examplein the figure below
(local link /
general link: log_log_plot_wik.html)
of an
power-law
function
plotted on a log-log plot.
Note that plots where only one axis is logarithmic
are called semi-log plots.
Semi-log plots cause
exponential functions
to be displayed as linear.
Collectively, log-log plots
and semi-log plots
are called logarithmic plots or
log plots.
Besides their use in
displaying and identifying
power-law
functions
and
exponential functions,
logarithmic plots
have a more general use.
The explanation of this general use is given in the figure below
(local link /
general link: log_log_plot_dj.html).
Note that log plots
turn up all the time in
astronomy
We see some examples in section
Exoplanets (Optional at the discretion of the instructor)
Sub Tasks:
Have you read them?
    Y / N
   
What is the slope of the
curve on the plot?     _________________
   
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php require("/home/jeffery/public_html/astro/applet/naap_planetary_orbit_simulator.html");?>
php require("/home/jeffery/public_html/astro/orbit/kepler_3rd_law.html");?>
php require("/home/jeffery/public_html/astro/mathematics/log_log__plot_wik.html");?>
php require("/home/jeffery/public_html/astro/mathematics/log_log_plot_dj.html");?>
However, before 1995, there were NO confirmed exoplanets around ordinary stars (see Wikipedia: Exoplanets: Confirmed discoveries).
This was just due to observational limitations as people had long believed.
Now thousands of exoplanets are known---see The Extrasolar Planets Encyclopaedia for current statistics.
Exoplanets are now known to be as common as stars to order-of-magnitude.
There are many methods of discovering exoplanets.
The 2 main methods Doppler spectroscopy and the transit method.
In this section, we learn a bit about discovering exoplanets with the 2 main methods and a bit about the current statistics of exoplanets.
The Doppler effect/shift is the change in frequency of a wave phenomenon depending on the motion of source and receiver.
It's a common phenomenon in everyday life for sound. For example, the pitch (which is the psychophysical response to frequency) of sirens depends on whether they are coming or going.
In fact, the Doppler effect is rather different between mechanical waves for which a medium is needed and electromagnetic radiation (EMR) which require NO medium.
We will NOT elaborate on mechanical waves here.
For EMR in vacuum, only the line-of-sight relative velocity between source and receiver determines the Doppler shift.
Note redshift/blueshift is astro-jargon for decreased/increased frequency which is also increased/decreased wavelength.
In this lab, we do NOT want to expand much on the
Doppler effect/shift, but
a little explication is needed to understand it for our purposes.
Sub Tasks:
Have you read it?
    Y / N
   
Have you watched them?
    Y / N
   
Using Doppler spectroscopy,
one measures the time varying
Doppler shift
of spectral lines
in stellar spectra.
They redshift,
then they blueshift,
then they redshift,
then they blueshift ...
The Doppler shift varies because the
stars have small
orbits about the
centers of mass
(i.e., barycenters)
of their planetary systems.
From the behavior of the
Doppler shift, the
orbital parameters
of the stars can be determined to some degree.
And from the orbital parameters
of the stars, details about the
planetary systems can be extracted,
and, in particular, exoplanets can be discovered.
Doppler spectroscopy
had been in use for decades before the first
exoplanet was discovered by it.
It was used to study
binary systems of stars
where the Doppler shifts,
due to mutually orbiting
stars,
are much larger than for a single
star
its planetary system.
Making Doppler spectroscopy
work in practice (for planetary systems)
required the ability to detect
Doppler shifts
corresponding to velocities
of order of magnitude 1 meter per second or less.
This ability only developed since circa 1990.
Complete this task using the
NAAP: Exoplanet Radial Velocity Simulator
shown in the figue below
(local link /
general link: naap_radial_velocity_simulator.html).
in the group must do the task for themselves.
Sub Tasks:
Have you read it? Y / N
In the
transit method for
the discovery of exoplanets,
one just observes the light curve of
a star.
Dips in the light curve of the right kind
show that planets are
transiting the
star and partially
eclipsing it.
Only stars with
inclination near 90°
will exhibit planet
transits.
EVERYONE in the group must do this task for themselves.
Sub Tasks:
Sub Tasks:
Sub Tasks:
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EOF
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php require("/home/jeffery/public_html/astro/applet/naap_exoplanet_transit_simulator.html");?>
P=[2π/(GM)**(1/2)]*R**(3/2) ,
where P is orbital period,
M is the parent star
mass (assumed much larger than the
planet
mass),
gravitational constant G = 6.67430(15)*10**(-11) (MKS units),
and
R is the mean orbital radius
(AKA the semi-major axis).
On the log-log plot, one gets
the linear relationship between logarithmic period and logarithmic radius
log(P)=(3/2)*log(R) + constant .
What is the slope of the line
on a log-log plot of
the dynamical Kepler's 3rd law?
HINT:
Reread subsection
Power Laws and Logarithmic Plots
above
(local link /
general link: Power Laws and Logarithmic Plots).
    ______________________________
   
If there are any planets in good position and weather permitting, we will observe one or more planets.
Sub Tasks:
Answer:
Answer:
Have you read them? Y / N
Here is the rundown on the planets
we can observe:
Observations for our lab are only possible for
Mercury
near greatest eastern elongation
if the class goes out as soon or maybe earlier than the class start time 7:30 pm.
Yours truly doesn't know if we
can see the phases of Mercury
with our Celestron C8 telescopes
even with our highest magnification
eyepiece.
Observations for our lab are only possible for
Mercury
near greatest eastern elongation
if the class goes out as soon or maybe earlier than the class start time 7:30 pm.
The phases of Venus can be observed
with our C8 telescopes,
but you probably require a higher magnification
than obtainable with our standard 40-mm eyepieces.
Superior planets
do NOT show full planetary phases since from the
Earth, since we always see at least part of the
day side.
In fact, the Earth is so close to the
Sun relative to
Jupiter and further out
planets will appear virtually full
all the time except to super precise measurements.
Mars can appear
gibbous at times
(see Wikipedia: Planetary phases).
With ideal seeing
and Mars in
opposition
(when it is closest to the
Earth), it may be possible to marginally
see surface features on Mars
with our C8 telescopes.
But maybe light pollution
rules that out.
In any case, ideal seeing
and opposition are
relatively rare events.
The Martian moons are probably
to small to be seen with our setup under any conditions.
Maybe long-exposure imaging
could pick them out.
Jupiter is always full because of its remoteness
from the Sun.
The
Jovian band structure
and Great Red Spot
(if it is on the day side of Jupiter)
should be readily observable.
The four Galilean moons
should also be readily seen as bright star-like objects.
They will be on a line which is rougly aligned with
the Jovian band structure.
One or more might be invisible if they are being eclipsed
by Jupiter.
One or more might be hard to see if they are transiting
Jupiter.
Saturn is always full because of its remoteness
from the Sun.
The Saturnian band structure
may be somewhat observable.
The rings of Saturn should be obvious.
Saturn
biggest moon
Titan
is probably observable.
It orbits in the equatorial plane (where the
Saturn's rings are too), but
it might be hard to identify from background stars.
Finding Uranus is tricky.
The sky alignment on the
C8 telescopes
may NOT good enough to put Uranus in the
field of view (FOV)
finderscope.
And even if it does, you still have to hunt among several possible
astronomical objects.
It's NOT impossible. It's been done.
Uranus should appear as a bluish star
Under high magnification
it should look a little disky.
The 9-mm eyepieces have
FOV approximately 10' = 600''
and Uranus'
angular diameter is 3.3--4.1'' ≅ 0.05'.
Finding Neptune is tricky.
The sky alignment on the
C8 telescopes
may NOT
good enough to put Uranus in the
field of view (FOV)
finderscope.
And even if it does, you still have to hunt among several possible
astronomical objects.
It's NOT impossible. It's been done.
Neptune should appear as a bluish star
Under high magnification
it should look a little disky.
The 9-mm eyepieces have
FOV approximately 10' = 600''
and Neptune
angular diameter is 2.2-2.4'' ≅ 0.03'.
The main thrill in seeing Neptune
is just the finding of it.
Maybe long-exposure imaging
with the C8 telescopes
could pick out
Pluto.
But you would have to put the C8 telescope
right on it---which is hard to do if it CANNOT be
identified by visual astronomy
with the C8 telescope.
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which in html
can be fudge-up as ↑☉)
is a superior planet,
and so can have any elongation
from the Sun.
Thus, if Uranus is in the
night sky and does NOT set too early or rise too late,
it should be available for observations.
Uranus is marginally a
naked-eye
astronomical object under ideal conditions---which
means never in Las Vegas.
Recall
arcminutes
are symbolized by the prime '
and
arcseconds
are symbolized by the double prime ''.
The main thrill in seeing Uranus
is just the finding of it.
A schematic diagram of the Celestron C8 telescope is in the figure below (local link / general link: telescope_c8_diagram.html). You should be able to name the parts.
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You will also need some specifications for
the telescope magnification
and FOV for
Celestron C8 telescopes.
See the table below
(local link /
general link: telescope_c8_mag_fov_table.html).
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Also in observing the planets,
it is useful to have an idea of their
angular diameters which can
be compared to the FOVs specified
in the table above
(local link /
general link: telescope_c8_mag_fov_table.html).
The range of angular diameters in arcseconds (symbolized by the double prime '') for the planets are:
Sub Tasks:
Have you read it? Y / N
Your truly suggests using the standard 40-mm eyepiece
for one diagram and a 18-mm
eyepiece for the second diagram.
Consult
Table: C8 Telescope Specifications for Available Eyepieces
as needed.
Remember the
C8 telescopes
does a point inversion
and the star diagonal
does an plane reflection
through the line perpendicular to its symmetry plane.
So you can approximately figure out
north,
south,
east,
and
west.
Yours truly suggests 2 diagrams per group both to be appended to the
favorite report form.
The circle on the diagram is the
FOV area.
Yours truly suggests
you observe the best observable planet---which is usually
the most interesting to look at---which if they are in the sky
are Jupiter or
Saturn.
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Post mortem comments that may often apply specifically to
Lab 5: Planets:
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