1. Starry Monday at Otterbein
Welcome to
Starry Monday at Otterbein
Astronomy Lecture Series
-every first Monday of the month-
October 6, 2008
Dr. Uwe Trittmann

2. Today’s Topics Practical Astronomy –Star maps and such
The Night Sky in October

3. Feedback!
Please write down suggestions/your interests on the note pads provided
If you would like to hear from us, please leave your / address
To learn more about astronomy and physics at Otterbein, please visit
(Obs.)
(Physics Dept.)

4. What’s up in the night sky?
The Celestial Sphere
An imaginary sphere surrounding the earth, on which we picture the stars attached
Axis through earth’s north and south pole goes through celestial north and south pole
Earth’s equator
Celestial equator
Relative positions of stars do not change -> attached to sphere
In ancient times was often literally thought of as a physical sphere rotating about the earth

5. What’s up for you? Observer Coordinates
Horizon – the plane you stand on
Zenith – the point right above you
Meridian – the line from North to Zenith to south

6. …depends where you are! Your local sky –
your view depends on your location on earth

7. Look North in Westerville

8. Look North on Hawai’i

9. SkyGazer
A computer program that simulates the vision of the sky during day and night
Things to observe:
Position on Earth: observe how the view of sky changes as you move E,W, N,S
Note the distribution of sunlight on Earth!
Rotation is around Polaris which is not in zenith

10. Star Maps … are a 2D rendering of a 3D situation
 They can’t be perfect!
You are looking at the inside of a sphere
East and West are reversed

11. On the Web

12. Star Maps
40º
90º
Celestial North Pole – everything turns around this point
Zenith – the point right above you & the middle of the map

13. Daily Rising and Setting
Due to the rotation of the Earth around its axis
Period of rotation: siderial day= 23h56m4.1s
1 solar day (Noon to Noon) =24h
Stars rotate around the North Star – Polaris
Circumpolar – never rise or set

14. That’s what you’d actually see!
Confusing?

15. Experts’ view Learn to identify crucial constellations
Find your way around the night sky

16. Hands On! Dial in the night sky as we will see it NOW! Advance time
Advance date

17. How bright are Stars? -The Magnitude Scale
The magnitude is a measure of the apparent brightness
Logarithmic scale
Notation: 1m.4 (smaller brighter)
Originally six groupings
1st magnitude the brightest
6th magnitude the dimmest
The absolute magnitude is the apparent magnitude a star would have at a distance of 33 ly: 2M.8
Note higher magnitude means a dimmer star!
Abs magnitude is effectively the luminosity; apparent magnitude involves the luminosity and distance
It is a property of the eye that a fixed difference in perceived brightness corresponds to a multiplicative factor in energy: thus if one star is one order of magnitude brighter than another, it gives off about 2.5 times as much light; 2 orders of magnitude, 2.5H2.5=6.25 times as much light; etc. 5 orders of magnitude=100 times.

18. When can I see a star/constellation?
When the Sun is not in the constellation!
As Earth moves around the Sun, the Sun seems to move around the ecliptic: from Aries to Taurus, Gemini, etc.
As the Earth rotates, stars rise in the East
Wait a while and “your” star will rise
Bummer: if you have to wait too long, the Sun will rise, too, and outshine your star.

19. Sun’s Apparent Path
Slow drift across background of fixed stars caused by rotation of earth about sun
Period = 1 year (365 ¼ days)
As Earth moves around the Sun, the Sun appears “in front” of the constellations of the ecliptic (Zodiac)

20. 3D view
Vernal equinox: Ecliptic intersects with celestial equator

21. When can I see the Moon?
Depends on its position relative to Sun, i.e. its phase
New Moon: same as Sun
Full Moon: opposite of Sun

22. When can I see the Planets?
The move slowly around the ecliptic
Look up in which constellation they appear
Identify them as “the extra star”

23. Motion of Sun, Moon and other Planets
All major bodies in the Solar System move around ecliptic
Slow drift (from W to E) against the background of stars
Skyglobe demo
7 visible “planets” incl. the sun and moon
Planet = “wanderer”
Days of the week named after the planets

24. Night Sky of the Season
As a crude way of finding visible constellations, one divides them into Summer, Autumn, Winter and Spring constellations
Some constellations are ALWAYS visible – the circumpolar ones that are close enough to the celestial pole

25. The Night Sky in October
The sun is past autumn equinox -> longer nights!
Autumn constellations are coming up: Cassiopeia, Pegasus, Perseus, Andromeda, Pisces  lots of open star clusters!
Jupiter is visible all night

26. Moon Phases Today (Waning Gibbous, 70%) 10 / 7 (First Quarter Moon)
10/ 14 (Full Moon)
10 / 21 (Last Quarter Moon)
10 / 28 (New Moon)

27. Today at Noon
Sun at meridian, i.e. exactly south

28. 10 PM Typical observing hour, early October Moon Jupiter Uranus
Neptune
Moon
Jupiter

29. South-West
High in the sky:
The summer triangle

30. Due North
Big Dipper points to the north pole

31. High up – the Autumn Constellations
W of Cassiopeia
Big Square of Pegasus
Andromeda Galaxy

32. Andromeda Galaxy
“PR” Foto
Actual look

33. with Plejades and the Double Cluster
East
Perseus and
Auriga
with Plejades and the Double Cluster

34. Greek Mytho- logy in the Sky

35. South -2006
Planets
Uranus
Neptune
Zodiac:
Capricorn
Aquarius

36. South –2007
Planets
Uranus
Neptune
Zodiac:
Capricorn
Aquarius

37. South –2008
Planets
Uranus
Neptune
Zodiac:
Capricorn
Aquarius

38. Mark your Calendars! Next Starry Monday: November 3, 2008, 7 pm
(this is a Monday )
Observing at Prairie Oaks Metro Park:
Friday, October 3, 7:45 pm
Friday, January 30, 7:00 pm
Web pages:
(Obs.)
(Physics Dept.)

39. Mark your Calendars II Physics Coffee is every Wednesday, 3:30 pm
Open to the public, everyone welcome!
Location: across the hall, Science 256
Free coffee, cookies, etc.

40. Solar vs Siderial Day Earth rotates in 23h56m also rotates around sun
 needs 4 min. to “catch up”
Consequence: stars rise 4 minutes earlier each night
after 1/2 year completely different sky at night!