Introduction to Astronomy 2019-2020 STISTK-10 Rijksuniversititet Groningen / Kapteyn Astronomical Institute. Lecture 2a (Getting to what we know today)

3. NOTE ON
TUTORIAL
GRADING…
• Based on this Rubric
• You can reflect on each week and
compare to your TA
• Also moderated by other TAs & me
• At the end of the day, the top score in
each TA or moderated grade counts
• The remaining 10% is for participation in
the tutorials, with a maximum if you do 6
(incase you need to miss)
• Note that missing lowers your chances of
demonstrating all the portfolio items –
not all occur every time!

5. LECTURE TUTORIALS – POSITION AND MOTION
See Pdf!

6. DON’T LET THIS
HAPPEN TO YOU!
HOLD UP YOUR SIGN!

7. FIELD TRIP TO NESTOR…
• Check out everything that is available to you!

8. SOME BASICS:
PHASES OF THE
MOON
• Why is a month a month?
• Why is there a Monday every week?
• Is there a dark side of the Moon?
• What is the source, object, collector,
detector?

9. KINESTHETIC ASTRONOMY – TRY IT WITH YOUR
FRIENDS!

10. THINK – PAIR – SHARE
What phase must the Moon be in
for a Solar Eclipse?
A. Full
B. New
C. No particular phase
D. Not enough information
You observe the Full Moon rising
in the East… What will it be like in
6 hours?
A. Basically still Full
B. Last Quarter
C. Depends on your location
D. Not enough information

11. Every star that we can see at
night is in this circle …
Amazing we know anything!

12. IMAGING CHAIN IN ASTRONOMY
SOURCE OBJECT (SOMETIMES
= SOURCE)
<<INTERVENING
MEDIA>>
COLLECTOR DETECTOR STORAGE ANALYSIS

13. What if we lived on a constantly cloudy, overcast, planet?

14. Ancient Astronomy: Still Works
(Stonehenge, UK)
Sunrise on the equinox… always due East

15. Ancient Astronomy: We can tell what they did
(Giza Pyramids, Egypt)
Earliest pyramids North
aligned, later gets worse as
they didn’t change how to
measure North over time!

17. WHAT’S THE EQUINOX!?
• B1950 – “Besselian Epoch 1950.0” – B uses years of 365.242198781 days keeping the Sun at
280 degrees longnitude each year
• J2000 – “Julian Epoch 2000.0”– J Uses the Julian date, based on years 365.25 days long
• Historically used Besselian equinoxes include B1875.0, B1900.0, B1925.0 and B1950.0
• The official constellation boundaries were defined in 1930 bizarrely (typical for astronomy)
using using B1875.0.
• ICRS (International Celestial Reference System) sets the RA and Dec at ~J2000 based on a
set of Quasars, so new epochs likely won’t be used – though you do still have to take
precession into account every day.

19. ASTROLABE, ORRERY,
SEXTANT, PLANISPHERE

20. Not always easy to
interpret observations
Ptolemy’s
Problems…

21. VERY BIASED ASTRONOMICAL HISTORY
(… SEE TUTORIAL THURSDAY)
Knew about
motion of Earth,
seasons and
length of year.
Then, Ptolemy
broke it to try to
prove one god not
many..
Inherited maths
from the
Egyptians, and
realised useful
things like
months, and 360
degree circles,
and stuff
Broke even more
what the
Egyptians knew
based on
monotheism and
really bad
numerical
system…. So cant
do maths
Really good at
navigating using
the stars. Even
did things like
“discover”
America.
Undervalued
though
Along with the
Mayans… great
at time, & astro
events. System
was too hard
though
Great at
understanding
most of the
movement of the
sky etc… but was
considered
property of the
Emperor … until
1800s

22. THEN COMES THE RENAISSANCE…
… OF WHITE EUROPEAN DUDES… (SORRY)

23. Developing new ideas could
be tough
Copernicus was only brave
enough to publish on his
deathbed
(Copernican Universe,
Poland)

24. INVENTION OF THE
TELESCOPE
• First described by Hans Lippershey in Middelburg in
Zeeland (South West Netherlands)
• Wasn’t granted a patent as others came up with the
same thing at about the same time
• Sent one to France which was then seen by someone
who told Galileo about it
• Galileo used his own version (made by never seeing
one) to observe things in space

25. Convincing evidence that the Copernican model
was good – moons going around Jupiter.
(Galileo Telescope, Italy)

26. Kepler refined laws describing
planetary motion based on accurate
observations by (stolen from) Tycho
Brahe

27. KEPLER’S LAWS
1. Planets orbit on ellipses with the parent star at one
focus
2. Planets sweep out an equal area in an equal time
3. The square of the orbital period is proportional to the
cube of the semi-major axis of the orbit
P2  a3

28. ECCENTRIC ORBITS?
a
b
Terms:
a – Semi-major axis
b – Semi-minor axis
e – eccentricity
0 < e < 1  elliptical
e = 1  parabolic
e > 1  hyperbolic
𝑏 = 𝑎 1 − 𝑒2
Mercury
e = 0.2056
Venus
e = 0.0068
Earth
e = 0.0167
Mars
e = 0.0934
Halley’s Comet
e = 0.9671
Comet 2I/Borisov
e = 3.35
Not from our
solar system!!

29. THINK – PAIR – SHARE
• If the Earth’s Orbit became perfectly circular, what would
happen to the seasons?
A. Be much less noticeable than they are now
B. Be about the same
C. Be much more noticeable than they are now

30. ORBITAL
ELEMENTS
• Periapsis = closest to object
• Perihelion if orbiting the Sun
• Perigee id orbiting the Earth
• Reference Direction (and up
down) Depends on System
•  is the “first point in Aries”
• = Spring Exuinox
• = 0h Right Ascension
• = where ecliptic & equator
cross (not in Aries!)

31. INTRODUCING: WORLD WIDE TELESCOPE
• Use online at http://www.worldwidetelescope.org/webclient/
• Download for Windows at http://www.worldwidetelescope.org/Download/

32. MAKING BETTER TELESCOPES
(START WITH LENSES… MOVE TO MIRRORS)

33. MOVE TO MIRRORS

34. KITT PEAK 4-M
TELESCOPE

35. AND GO TO SPACE…

36. THINK – PAIR – SHARE
JOHN GRUNSFELD SAYS…
• Space Telescopes are more sensitive because:
A. They are bigger than ground based telescopes
B. They are closer to the objects being observed
C. They do not have to look through the atmosphere
D. More than one of those reasons

37. LBT
(LARGE
BINOCULAR
TELESCOPE)

38. HET
(HOBBY-EBERLY
TELESCOPE)

39. GMT
(GIANT
MAGELLAN
TELESCOPE)

40. ELT
(EXTREMELY
LARGE
TELESCOPE)

41. ALL THE BIG
ONES…
Our Gratama Telescope (Blaauw
Observatory) on the same scale

42. MAYBE WE HAVE
THE THIRD
LARGEST OPTICAL
TELESCOPE IN THE
NETHERLANDS…
Don’t Forget –
Telescope Invented Here!

43. HOW TELESCOPES EXPANDED THE UNIVERSE

44. CONCEPT BANK
Moon Phases
Scale of what
we can see
Imaging Chain
in Astronomy
Ancient
Astronomy
Ptolemy and
Epicycles
Copernican
Model
Precession of
the Equinoxes
Kepler’s Laws
Orbital
Elements
Eccentricity of
Orbits
Invention of
the Telecope
Improving
Telescopes
Expanding
horizons in the
Universe

45. Q’S
Why are there no big optical
telescopes in the Netherlands?
Why are there no new refracting
telescopes?
Why does powerpoint think
refracting is like a caterpillar?
Why is astronomy so hard?

46. Q&A