Presentations text content in Measuring the Stars (Part III)
Slide1
Measuring the Stars
(Part III)
Slide2Slide3The “
Cosmic Distance Ladder
”
Slide4Slide5Slide6Visual
“
Parallax
”
Slide7“
Binocular
Vision”…
Let’s us “see” 3D images
(depth)
…but, how to do this to get
Astronomical Distances
?
Slide8“
Stellar Parallax”
…
Using
Earth’s Orbit
as a “Baseline”!
Slide9Slide10Slide11Slide12“
Standard Candles
”
as
Distance Indicators
... :
(Measured)
(
Known
,
“Standard Candle”!)
(
C
an now be
Calculated
!)
Slide13Slide14Main Sequence
Stars as
Standard Candles
!
Slide15(Both
K
-type
!)
But how to
tell apart
Main Sequence stars
from non-Main-Seq. stars,
for Spectroscopic Parallax…?
Small,
Dense
(Main Seq.) stars have
broader
Spectral Lines
than
“puffy”
Giant stars… :
Slide16Slide17Slide18Turning
“Variable Stars”
into
Standard Candles
for finding distances... :
Cepheid “
Period-Luminosity Relationship
”
Slide19Slide20If
(
) now
known
This Rotating Galaxy is a
Standard Candle
!
Faster
Rotation
More
Gravity
More
Mass
More
Light
(…we
assume
…!)
Slide21Slide22White Dwarfs (w/companions) always
blow up
(“
Type
Ia
Supernova
”) at the
Chandrasekhar Mass
(
M
= 1.4 x
M
Sun):
…Standard Explosion
Standard Luminosity Standard Candle
!
Slide23Know
Distance to
a
Supernova
Know Distance
to its
Host Galaxy
Can
“Map”
the
Cosmic
Large-Scale
(Galactic)
Structure!
Slide24Brighter
Supernovae
glow longer
than
dimmer
Supernovae…
Since
1995,
Type
Ia
Su
pernovae
now have
very well known
Luminosities…
Even better
Standard Candles
!
Slide251998
: Type
Ia
Supernova Standard Candle data proved that
the
Expansion Rate of the Universe is
Accelerating
!
Slide262011
Slide27Slide28“
Hubble’s Law
”:
V = H
0
x D
(Velocity =
Hubble’s Constant
x
Distance
)
Other Galaxies all
Doppler
Redshifted
…
Expanding Universe
makes them
recede
from us!
Slide29Slide30Cosmic Distance
Mapping the
Universe??
Ladder
Slide31Cosmic Distance Ladder
Mapping the Universe
!
Measuring the Stars (Part III)
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