Review Seven
Astronomy I
V. J. Motto
Modus Operandi
• Review of Chapters 13 & 14
• Short Break
• Chapter 15 & 16
• Short Break
• The Sky Tonight
• Laboratories and Experiments
– Comments
– Work in Groups
• A Look at the heavens (weather permitting)
Our Galaxy
• What is the name for
out galaxy?
• Where are we located
in the galaxy?
• Where do you look to
see our galaxy in the
winter? In the
summer?
Basic Structure of Our Galaxy
• What are Population I
stars?
• Where do you find
Population II stars?
• How is self-sustaining star
formation accomplished?
• What do some
astronomers believe is at
the center of the Milky
Way Galaxy?
Classification of Galaxies
Distance Techniques
• Hubble’s Law
• Standard Candles or
Tully-Fisher
• Variable Stars
• Spectroscopic
Parallax
• Stellar parallax
• Radar
Hubble’s Law
• The Hubble Law
– Edwin Hubble
– 1929
– Velocity Recession V = Hd
– The Hubble constant, H, is between 70 to 80
km/sec/Mpc.
Mass Method
• Tully
– a correlation between
the rotational velocity
and the total
luminosity.
– Distance
– Mass
• Rotating Galaxies
Dark Matter
The rotation of galaxies are strong
evidence for dark matter, but
astronomers have even more
evidence that most of the mass of
the universe is invisible.
For example, the velocities of galaxies
are so high that they would fly apart
if they contain only the mass we see.
Coma cluster; visible & X-ray.
The Local Group
Galaxies After the 1950s
Radio telescopes can map a
galaxy and produce a
false-color image as if we
could see radio waves.
In this radio image of 3C388,
atypical double-lobe radio
galaxy, the galaxy lies at
the center flanked by
bright radio energy.
Seyfert Galaxy
• Karl Seyfert --- 1943
• Properties lie between
those of normal
galaxies and the most
violent actives known.
• Spectral lines show a
substantial red shift.
• NGC1566 has a small
and very luminous
nucleus
BL Lac Objets
• Also known as
blazars.
• Elliptical galaxies
– Lacerta
– no absorption lines
– no emission lines
• M87 is show at the
left.
• Hubble Telescope
reveals a jets from a
rapidly spinning disk.
Quasars
• Discovered in 1960s
by radio
interferometry.
• Faint points of light
with peculiar emission
spectra.
• Quasi-stellar objects
(QSOs)
• Very powerful cores
of active galaxies.
Activity Evolution
A possible evolutionary sequence
for galaxy activity, beginning
with the highly luminous
quasars, decreasing in violence
through the radio and Seyfert
galaxies, and ending with
normal spirals and elliptical.
The central black hole that
powered the early activity are
still there at later times; they
simply run out of fuel as time
goes on.
Assignment Update
• Laboratories • Drawings
– Lab1: Star Hunting (Done) – Moon
– Lab2: Sun, Moon, & Planets – Planet
(done) – Sun
– Lab3: Free Falling (done) – Circumpolar
– Lab4: More Free Falling (done) – Constellations
– Lab5: Circular Motion & • Term Paper
Acceleration (done)
– Topic Chosen
– Lab6: Solar System (done)
– Begin Research
– Lab7: Solar System Revisited (in
progress) – Turn in References
• Experiments – Work on Outline
– Exp1: (done) – Turn in outline
– Exp2: (done) – Write, and Rewrite
– Exp3: (done) – Proofing and re-writing
– Exp4: (in progress)