1. Physics 101 - Astronomy Dr. Brian M. Davies
Office: 532 Currens Hall,
Office Hours are M W F 11-noon and Tues 10-11:30 a.m.
See the webpage for notes & syllabus

2. The required course textbook is “Astronomy”, by A. Fraknoi, D
The required course textbook is “Astronomy”, by A. Fraknoi, D. Morrison, and S.C. Wolff Available free online at openstax.org Suggested readings will be posted on my webpage at and on Western Online

3. Openstax Astronomy Week 1 readings: Study sections 1.1 - 1.5 pp. 11-18
Read sections pp
Study section pp
Study sections pp

4. Look at the syllabus and the dates.
Mark your calendars for exam dates.
Four exams and one final exam.
2 short papers will be based on movies.
Other activities, in-class worksheets…
Extra credit for evening events.
See policy statements on syllabus.

5. Additional policy for teacher education students from the Teacher and Professional Education Program
The Teacher and Professional Education Program (TPEP) at WIU has additional policy for the syllabus of general education courses. See
TPEP vision statement: “Our graduates will be empowered educational professionals deeply committed to continuous learning and the empowerment of all learners.”
TPEP mission statement: “The WIU Teacher and Professional Education Program empowers candidates to become educational practitioners who engage in informed action that is grounded in knowledge and reflection; who are deeply committed to the highest standards of professional practice; who are able to adapt to emerging social, economic, and cultural landscapes; who are skilled in the use of technological tools that promote teaching and learning; and who are committed to empowering all learners.”
“In accordance with Illinois State Board of Education certification rules, all candidates seeking teacher certification are required by Western Illinois University to obtain a grade of “C” or better in all directed general education courses, all core courses, and all courses in the option. Note: A “C- ” is below a “C”. “
Please see the extra handout or look at the online syllabus on my website at

6. FIGURE 1-2 The Scales of the Universe
This curve gives the sizes of objects in meters, ranging
from subatomic particles at the bottom to the entire
observable universe at the top. Every 0.5 cm up along the arc
represents a factor of 10 larger. (Top to bottom: R. Williams and
the Hubble Deep Field Team [STScI] and NASA; AAT; L. Golub, Naval
Observatory, IBM Research, NASA; Richard Bickel/Corbis; Scientific
American Books)

7. FIGURE 1-3 Inventory of the Universe
Pictured here are examples of the major categories of objects that have been
found throughout the universe. You will discover more about
each type in the chapters that follow. (a: NASA/Hubblesite;
b: NASA; c: Peter Stättmayer/European Southern Observatory; d: Big
Bear Observatory; e: NASA/Jeff Hester & Paul Scowen; f: Anglo-
Australian Observatory; g: NOAO; h: NASA; i: N. F. Comins & F. N.
Owen/NRAO)

8. What can we see in the visible sky?
Humans can see about 6000 stars in the night sky (with good vision and a very dark clear night).
Some of these form patterns called asterisms.
These have been grouped into constellations (88 in the current system). Most have old names from mythology; those in the southern hemisphere have Western names.

9. The Constellation Orion, as seen in the sky and as imagined.

10. Why constellations?
Why do people invent constellations in the night sky?
Before indoor lighting, many people spent their evenings under the stars, with plenty of time to talk and observe.

11. Constellations are invented for
Story-telling, mythology, ritual
Culture and religion
Navigation and timekeeping
Mapping the sky; modern astronomy uses the constellations to label areas that are delimited by boundaries.

12. Navigation
The pole star, Polaris, can be used to determine the direction toward north.
The star Hydra may have been used by Minoan sailors to get East-West directions (2400 BC).
Polynesian sailors used celestial navigation.
Until recently, sailors used celestial measurements for navigation of ships.

14. Mapping the sky: Constellations can be used
to divide up the sky into regions.

15. For example, Orion can be used two ways:
FIGURE 1-4 The Constellation Orion
(a) The pattern of stars
(asterism) called Orion is prominent in the winter sky. From the
northern hemisphere, it is easily seen high above the southern
horizon from December through March. You can see in this
photograph that the various stars have different colors, something
to watch for when you observe the night sky.
(b) Technically, constellations are entire regions of the sky. The
constellation called Orion and parts of other nearby constellations
are depicted in this photograph. All the stars inside the
boundary of Orion are members of that constellation. The
celestial sphere is covered by 88 constellations of differing
sizes and shapes. (© 2004 Jerry Lodriguss/
as an asterism.
as a region of the sky.

16. The Celestial Sphere
The distance to the stars is not evident to our eyes, and they appear to be at the same distance.
If we think of this distance as a radius, the stars appear to be on a sphere, with us (on the Earth) at the center.

17. The Constellation Orion is actually three dimensional, but appears to us as a group of points on the “celestial sphere” For more images, see this link, which will be given in the class notes for the day, available from my website. (link)

18. The Celestial Sphere appears to rotate around us at night
The Celestial Sphere appears to rotate around us at night. But you know that it is the Earth that is rotating. (link)

19. To observers who think the earth is stationary,
The celestial sphere appears to be rotating.

20. The Northern Sky, in a time exposure, shows the apparent motion of the northern part of the celestial sphere around the Pole star, Polaris.

21. Right Ascension and Declination are used to indicate positions on the celestial sphere. They correspond to latitude and longitude on the surface of the Earth.

24. The celestial sphere is oriented with respect to the earth, with poles and an equator.

25. On the celestial sphere we use Declination like we use Latitude on the Earth.

26. On the celestial sphere we use Right Ascension like we use Longitude on the Earth, but measured in hours, minutes, and seconds.

27. For an observer on the ground,
directions are defined in this figure.

30. The observer on the ground can also use angles
for altitude (Alt), the angle up from the horizon, and
azimuth (Azm), which is a heading (N, E, S, W etc.).

31. For more detail on Right Ascension and Declination, see this.

32. Stars are (almost) fixed on the celestial sphere and the Earth rotates inside this sphere. It only looks like the celestial sphere is rotating from our perspective if we are on the Earth.

33. Question ?
To us, which way does the celestial sphere appear to be rotating?
Hint, think about the motion of the moon and the sun during the day or night.
Now, if the celestial sphere is actually not moving, and the Earth is rotating, which way does the Earth rotate?

34. Apparent rotation of the celestial sphere is due to the rotation of the Earth.
The Earth is rotating around an axis that goes from pole to pole through a center.
Eventually, each day, the Sun sets in the west. If we suppose the Sun is the center of the solar system, it is fixed, so:
Each point on the surface of the Earth is going east all the time (except the poles).

35. to be continued. Things to do:
Get the online textbook. Decide which form is most convenient for you.
Read (skim) Ch. 1, pp
Look at the syllabus and the dates.
Mark your calendars for exam dates.
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