Introduction to Astronomy 2019-2020 STISTK-10 Rijksuniversititet Groningen / Kapteyn Astronomical Institute. Lecture 2b (What is in the Universe)

2. LETS GO WITH KAHOOT!
• Download the App or go to Kahoot.it
• Get ready to join!!
• Top 3 = Chandra Pen

3. REVIEW – LT: KEPLERS LAWS

4. QUESTIONS FROM
THE LAST
CLASSES?

6. … MOSTLY WE
DON’T KNOW
• 5% We are OK with!
• 26% Dark Matter – has a
gravitational effect
• 69% Dark Energy – more like the
elasticity of Space Time
• We will worry about the 5% mostly
– as that’s what allows us to infer
the rest!

8. MOST OF THE MATTER
IS HYDROGEN…
• X = Mass fraction of Hydrogen
• Y = Mass fraction of Helium
• Z = Mass fraction of Everything Else
• X + Y + Z = 1.00
• Z is called the Metallicity
Surface of the Sun:
• X = 0.7381
• Y = 0.2485
• Z = 0.0134
Abundance Ratios:
𝐹𝑒
𝐻
= log10
𝑁 𝐹𝑒
𝑁 𝐻 
− log10
𝑁 𝐹𝑒
𝑁 𝐻 
• Youngest stars (Population I) – Higher Metallicity
• Middle aged stars (Population II) – Like the Sun
• Primoridal Stars (Population III) – [Fe/H] < -6

9. Spectra are Chemical Fingerprints

10. REFERRING TO ELEMENTS IN ASTRONOMY
(MAYBE JUST TO IRRITATE CHEMISTS…)
Hydrogen… most simple!
Chemistry Astronomy Notes
H2 Molecular
Hydrogen
Hard to
observe (Traced
by CO2)
H HI (H-one) Observed at
21cm (Spin flip
transition)
H+ HII (H-two) Emission lines
observed
Nomenclature…
• Molecular
• Neutral or I (Roman Numeral 1)
• Then add one for each ionization state
• e.g. O3+ ions = OIV
• Some emission can be from “forbidden” transitions as gas can be so
low density, but such large volume, that very long transitions occur
• Those are marked like [OIII] in spectra
• “Nebulium” coming from star forming nebulae at 500.7nm turned out to
be an [OIII] line
• Helium first discovered from spectral lines in the Sun
(Helios = Sun)

11. ORIGINS OF THE ELEMENTS

15. THINK – PAIR – SHARE
• If the Sun was the size of a basketball / football in the Zernike Campus…
the next closest star, would be a similar size ball, at the distance of:
A. The Academiegebow
B. Amsterdam
C. Barcelona
D. The North Pole

16. EVEN INSIDE A
GALAXY…
SPACE IS
HUGE!

17. The Scale of the
Universe:
Powers of Ten

18. KAHOOT! – WHAT IS THIS GAME
• Download the App or go to Kahoot.it
• Prizes: Top 3 get a University of Groningen Notebook

20. Aphoheles: Entirely within Earth’s Orbit
Only 18 are known.
Main Belt Asteroids:
(Split into 3 with gaps between)
Inner Belt (Largest is Vesta)
Intermediate Belt (Ceres)
Outer Belt (Hygiea)
Hildas: 3:2 Resonant with Jupiter
Trojans: Lead and Follow Jupiter on its orbit
(at Lagrange points 4 and 5)
Earth Orbit Crossing:
(Risky business!)
Atens: On average slightly inside
Earth’s orbit
Apollos: On average slightly outside
Earths’ orbit
Amors: Near Earth, but orbit
entirely outside Earth’s orbit
Alindas: 23 known held in unstable highly elliptical
orbits by Jupiter and Earth… they will eventually crash
Into Jupiter, Mars or Earth.
Mars and Earth Trojans: Follow
orbits of Earth and Mars in the
same way… but we only know
4 Mars Trojans, and 1 Earth Trojan
(Likewise 1 Uranus Trojan, and 17
Neptune Trojans are known)
Damocloids and Centaurs:
Lie beyond Jupiter, and often
have highly eccentric orbits.
Probably captured comets or
Trans-Neptunian Objects
Trans-Neptunian Object:
Far out in the Solar System including
Kupier Belt Objects like Plutions,
Scattered Disk Objects like
Sednoids, and the far out Oort Cloud
Objects
(Map: Minor Planet Center 2002)
HITCHHIKERS GUIDE TO THE ASTER

21. COMETS IN THE MIX
Dust Tail
Ion Tail
NucleusComa

23. STRUCTURE OF
THE SUN

25. STARS!
Classifying
Stars

26. Planets we know around other stars

27. VARIABLE STARS

32. Classifying
Galaxies

33. A
B
C
D

34. ACTIVE
GALAXIES
Radio Galaxy /
BL Lac (Blazar)
Normal Elliptical
Quasar
Seyfert
Normal Spiral

36. GALAXY CLUSTERS

39. EXPLORE IN
WORLD WIDE
TELESCOPE

40. CONCEPT BANK
Matter – Dark
Matter – Dark
Energy
Particles Atoms Periodic Table Metallicity
States of
Matter
Spectral Lines
Origin of
Atoms
Scale of the
Universe
Solar System Planets Moons Asteroids Comets
The Sun
Classification
of Stars
Exoplanets Variable Stars
Open &
Globular
Clusters
Cluster
Evolution
Components
of a Galaxy
Galaxy
Classification
Active
Galaxies
Galaxy
Clusters

41. MORE DEPTH IN THE BOOK
• Chapter 1 (Especially 1.3 Objects of Research)
• Section 3.2 Optical Telescopes
• Sections 6.3, 6.4, 6.5 Orbits and Kepler’s Laws
• Chapter 7 (The Solar System – Especially 7.3;
6.4; 7.5)
• Section 9.5 The H-R Diagram
• Section 12.8 Origin of the Elements
• Section 19.1 Classification of Galaxies
• MUCH more depth for your own interests
• Chapter 8 – Objects of the Solar System
• Chapter 13 – The Sun
• Chapter 14 – Variable Stars
• Chapter 17 – Star Clusters and Associations
• Chapter 18 – The Milky Way
• Chapter 19 – Galaxies