Download 2017 Div. C (High School) Astronomy Help Session

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2017 Div. C (High School) Astronomy Help Session
Sunday, Feb. 19th, 2017
Stellar Evolution and Type 1a supernovae
Scott Jackson Mt. Cuba Astronomical Observatory
• SO competition on March 4th
.
• Resources
– two computers or two 3 ring binder or one laptop plus
one 3 ring binder
– Programmable calculator
– Connection to the internet is not allowed!
– Help session before competition at Mt. Cuba Astronomical
Observatory
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Study aid -1
• Google each object,
– Know what they look like in different
parts of the spectrum. For example, the
IR, optical, UV and Xray
– Understand what each part of the
spectrum means
– Have a good qualitative feel for what the
object is doing or has done within the
astrophysical concepts that the student is
being asked to know.
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Study aid - 2
• Know the algebra behind the physics
– Just because you think you have the
right “equation” to use does not mean
you know how to use it!!!
– Hint for math problems: Solve
equations symbolically BEFORE you
put in numbers. Things tend to cancel
out including parameters you do not
need to have values for.
– Know how to use scientific notation.
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The test – 2 parts
• Part 1 – multiple choice and a couple fill
in the blanks
• Part 2 – word problems for astrophysics
there will be some algebra
Solve the equations symbolically first
then put in numbers!!!!
Hint: most problems will not need a
calculator if done this way
Topics - 1
Stellar evolution, including
- stellar classification,
- spectral features and chemical composition,
- H-R diagram transitions,
- Accretion disks
- Main sequence stars
- red giants,
- white dwarfs (oxygen & helium),
- neutron stars, planetary nebulas
Luminosity,
blackbody radiation,
color index,
Spectral class of stars
•
•
•
•
•
•
•
•
•
O
B
A
F
G
K
M
L Red Dwarfs (failed stars)
T Brown Dwarfs (failed stars)
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Categorizing stars by their spectra
1. Spectra can tell you
the stars approximate
temperature
(blackbody radiation)
2. Absorption (dark)
lines in a star’s spectra
give a finger print of
elements that are seen
in that spectral class of
stars
BUT emission spectra spectra (bright lines against
a dark background) are given off by nebulae –
glowing gas clouds
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Spectral class of stars
He+ lines
H Balmer lines (B,A & F stars)
Ca+ lines (F & G stars)
Fe and neural metals K & M stars)
TiO2 lines
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Spectral classification & Temperature of main sequence stars
Star
Spectral
Class
Proportion of Stars
Surface
Temperature
(°F)
Star Mass
(Sun = 1.0)
Star
Luminosity
(Sun = 1.0)
Lifespan
(Billions
of Years)
Example Star
A0
1% A0 - A9
20,000
2.8
60
0.5
Vega
A1
---
18,400
2.35
22
1.0
Sirius
A5
---
15,000
2.2
20
1.0
---
F0
3% F0 - F9
13,000
1.7
6
2.0
---
F5
---
12,000
1.25
3
4.0
Procyon A
G0
9% G0 - G9
11,000
1.06
1.3
10
---
G2
---
10,600
1.00
1.0
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Sun
Alpha Centauri A
G5
---
10,000
0.92
0.8
15
---
K0
14% K0 - K9
9,000
0.80
0.4
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Alpha Centauri B
K2
---
8,700
0.76
0.3
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Epsilon Eridani
K5
---
8,000
0.69
0.1
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61 Cygni A
M0
73% M0 - M9
7,000
0.48
0.02
75
---
M5
---
5,000
0.20
0.001
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Proxima Centauri 10
(Alpha Centauri C)
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More on stars spectral class
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Hertzsprung-Russell Diagram
Y axis is always
brightness or
relative luinosity
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X axis is always
temperature, color
or spectral class
Each dot is a star
A is the location of
our sun on the main
sequence
B are red giant stars
that are fusing
helium in their core
L
http://outreach.atnf.csiro.au/education/senior/cosmicengine/stars_hrdiagram.html
D are white dwarfs (super hot carbon stars)
T
C are red
supergiants with
Helium and
Hydrogen buring in
shells and carbon in
its core
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Instability gaps on
an H-R diagram for
the pulsating class
of variable stars
Period of pulses
scale with absolute
brightness of the
star
“Period-luminosity
relationship”
•
http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_pulsating.html
Accretion disks
• Circumstellar disks
• Many accretion disks seen in binary star systems when one
star hass filled its “Roche” limit and is having material
“sucked” away from it to a companion start (e.g., white
dwarf)
Disk in Orion
nebulea
http://planetquest.jpl.nasa.gov/documents/RdMp272.pdf
Birth of a solar mass star
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The birth of a 1 solar mass star going onto
the main sequence.
Before point 4, contraction of intersteller
gas cloud. The cloud heats up as it
contracts, causing its luminosity to
increase -- we don’t see it because the
protostar is hidden in dust.
From point 4 to 6, -- The cloud contracts
more and its luminosity drops.
Point 6, hydrogen starts to fuse to helium
in the stars core. The heat generated from
fusion balances gravity. The star’s
surface heats up slightly.
This is the location of T Tauri stars
Point 7. The star has reached a long lived
equilibrium where the heat from fusing
hydrogen to helium balances gravity. The
star resides on the main sequence for
most of its life (~10 billion years for a 1
solar mass star).
Formation of white dwarfs
Death of main sequence stars
Red Giant for lower mass stars
Low mass star like our sun
stops at carbon formation in
its core...
And fluffs off its
outer layers to
make a
planetary
nebulae and a
white dwarf star.
Red Giant for higher mass stars
But a high mass star,
like those in the early
universe had enough
mass to fuse nuclear
material all the way
to iron. However,
once iron
accumulates in its
core no net energy
generation can be
done by fusion of
iron, gravity takes
over and core
collapse occurs
and.....
Electrons are pushed into
protons making neutrons
and a flood of neutrinos….
It goes boom!!!!... A
supernovae!!! (this is the
Crab Nebulae) …
Which make lots of heavy
elements needed to make
terrestrial (earth like)
planets. This is NOT a type
1a supernovae. It is a type II
supernovae.
.. And it spreads
heavy elements
throughout space to
be picked up by a
new generation of
stars,.....
.. The shock
wave either from
the supernovae
or from the
initial star
formation stage
can initiate new
star
formation,.....
Stars and planets approximate black body radiators
The wavelength at maximum
radiation changes with
temperature
λmax = 550 nm  5300 K
temperature for our sun.
“G” type star (subclass “2”) or
G2
λmax x Temperature = constant
= 2.9x106 nm-°K
Or = 2.9x107 A-°K = 2.9x103 μm-K
Nm[=] nanometers for wavelength
Or A [=] Angstrom units for wavelength
Or μm [=] microns units for wavelength
°K [=] degrees Kelvin
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Another way to look at black body radiation
Plot log λ (x axis) vs log of spectral intensity at that λ
Example calculation for a star’s temperature
So the shorter the wavelength the
hotter or colder the star????
λmax ~ 0.9 μm
What it the star’s temperature?
T ~ 2.9x103 μm-K / 0.9 μm
= 3200 K (M type star)
λmax x Temperature = constant
= 2.9x106 nm-°K
Or = 2.9x107 A-°K = 2.9x103 μm-K
Nm[=] nanometers for wavelength
Or A [=] Angstrom units
Or μm [=] microns units
°K [=] degrees Kelvin
If λmax ~ 10 μm
What it the star’s temperature?
T ~ 2.9x103 μm-K / 10 μm
= 290 K (black dwarf)
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Color Index or color – color diagrams
• A way to compare the apparent magnitude of stars at different
wavelengths (using photometry instead of spectrometry).
• Observe at narrow bands of wavelengths ( a color) and note the
difference in the intensity of these different bands.
• Spectrometry (measuring the entire spectrum) is more difficult than
photometry (observations at a single color).
• But what is U, B and V??
https://en.wikipedia.org/wiki/Color_index
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UBV, UBVRI and JHK systems for Color-color diagrams
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Color Index or color – color diagrams
• Where is our sun on the U-B vs B-V diagram?
https://en.wikipedia.org/wiki/Color_index
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White dwarfs (oxygen & helium) -1
• White dwarfs are the end point for moderate mass stars like
our sun: Mass ~0.5 to ~4+x mass of sun (Msun)  the
progenitor stars are not massive enough to generate neutron
stars or black holes when they die.
• White dwarfs do not generate any energy – they are just
cooling off and will follow a well defined “cooling” curve on
the H-R diagram.
• Maximum mass of a white dwarf is dictated by electron
degeneracy pressure ~ 1.4 x Msun– the pressure below which
the electrons are not pushed into the nucleus. This is called
the Chandrasekhar limit
• White dwarfs will take a long time to cool off but as they do,
they will become red dwarfs and then brown dwarfs as their
(black body) spectra shifts to longer wavelengths of light
• .
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White dwarfs (oxygen & helium) - 2
• The more massive the white dwarf – the smaller it is(!)
• Many red dwarfs or brown dwarfs were not white dwarfs to
start with – they may just be failed stars that did not have
enough mass to initiate fusion in their cores.
• Progenitor stars of lower mass will not be able to fuse helium
in their shells. When they die as white dwarfs, they will
appear as helium white dwarfs.
• Progenitor stars of higher mass will be able to fuse helium
in their shells to carbon and oxygen and these will appear as
oxygen white dwarfs.
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Neutron stars
• When higher mass stars “die” gravity takes over and the
core of the star collapses. Electron degeneracy pressure is
overcome and electrons are pushed into the protons to form
neutrons (and a flood of neutrinos – that give rise to a
supernovae).
• Initial angular momentum will be distributed between the
supernovae remnant and the resulting neutron “star”.
• The angular momentum of the neutron star can cause it to
spin very quickly – creating a pulsar.
• Strong magnetic fields can focus a beam of radiation like a
light house
• Pulsars can have an accretion disk (from the blown off
remnant of the star) that generates x-rays as matter is
accelerated to near the speed of light as it falls into the
neutron star.
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Planetary nebulas
• Old definition: Any small, relatively round object that when
first observed by early astronomers looked like a planet (but
did not move like a planet in our solar system).
• New definition: specifically refers to the gas and dust that is
“fluffed off” a low mass dyeing star that will ultimately lead
to white dwarf.
• Some of the most beautiful and intricate objects in the
universe.
• Our sun will generate a planetary nebulae when it dies to
become a white dwarf.
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Mass of the main
sequence star is reduced
as it evolves and dies.
Material is shed either
during the formation of
a planetary nebulea
(white dwarf) or during
a supernovae.
The supernovae in this
diagram are meant to be
Type II and not Type Ia.
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Type Ia supernovas,
dwarf novas,
AM CVn systems,
Mira variable Stars,
globular clusters.
Topics - 2
Use Kepler’s laws of rotation and circular motion to answer
questions relating to the orbital motions of binary systems;
use parallax, spectroscopic parallax, the distance modulus and
Hubble’s law to calculate distances to Type Ia supernovas.
Type 1a supernovae
A type Ia supernova occurs in binary stellar
system (two stars orbiting one another) in which one of the stars is
a white dwarf. The other star can be anything from a giant star to
another white dwarf.
Material is drawn off the other star (filling its “Roche” limit) onto the
white dwarf until the white dwarf reaches the Chandrasekhar limit.
Then electron degeneracy pressure is unable to prevent catastrophic
collapse. If a white dwarf gradually accretes mass from a binary companion,
its core will reach the ignition temperature for carbon fusion as it
approaches the limit. If the white dwarf merges with another white dwarf, it
will momentarily exceed the limit and begin to collapse, again raising its
temperature past the nuclear fusion ignition point. Within a few seconds of
initiation of nuclear fusion, a runaway reaction will occur and thus causing
the supernovae
 Bottom line: Type 1a SN produce a consistent peak in absolute
luminosity because of the uniform mass of white dwarfs that explode via the
accretion mechanism. Absolute magnitude is M ~ -19.5 (negative)
One
explanation
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•  Bottom line: Type 1a SN produces a consistent
peak in absolute luminosity because of the uniform
mass of white dwarfs that explode via the accretion
mechanism. Absolute magnitude is M ~ -19.5
(negative)
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Dwarf Novae
• Cataclysmic variable star
• Close binary system where one companion is a white
dwarf that is sucking material from its companion into
an accretion disk
• The material accumulating in the disk can get hot and
we see it as a burst in the luminosity of the system
(although it is just the disk that is shining brighter).
• This matter accumulation in the disk will stop
(companion star has stopped feeding the disk) and the
disk cools off and drops in luminosity.
• This process repeats itself from days to years – not
necessarily in a regular pattern.
•
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• An AM CVn star, or AM Canum Venaticorum star, is a
rare type of cataclysmic variable star named after their type
star, AM Canum Venaticorum. In these hot blue binary
variables, a white dwarf accretes hydrogen-poor matter
from a compact companion star.
These binaries have extremely short orbital periods (shorter
than about one hour) and have unusual spectra dominated by
helium with hydrogen absent or extremely weak. They are
predicted to be strong sources of gravitational radiation,
strong enough to be detected with the Laser Interferometer
Space Antenna.
AM CVn systems consist of an accretor white dwarf star,
a donor star consisting mostly of helium, and usually
an accretion disk.
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Globular Clusters
•
•
•
•
•
•
•
•
•
•
•
A gravitational bound “close” association of stars
0.4 stars per cubic parsec on average
100 to 1000 stars per cubic parsec in its core
The cluster has a spherical shape.
Very old objects ~10 billion years old – perhaps as old as
our galaxy
Very old stars
Contains hundreds of thousands of stars
Some may have massive black holes in their cores.
These clusters form a “halo” around the center of our
galaxy  not necessarily found in the spiral arms
Origin of globular cluster is still being debated
Completely different from “open cluster” of stars
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Mira Variable
stars
Instability gaps on
an H-R diagram for
the pulsating class
of variable stars
Period of pulses
scale with absolute
brightness of the
star
“Period-luminosity
relationship”
•
http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_pulsating.html
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Mira Variables
•
•
•
•
•
They are red giants
– very late stages of stellar evolution for low mass stars,
on the asymptotic giant branch,
– will expel their outer envelopes as planetary
nebulae and become white dwarfs within a few million
years.
Massive enough that they have undergone helium fusion in
their cores but are less than two solar masses,
Have already lost about half their initial mass (fluffing off
their planetary nebulae.
Thousands of times more luminous than the Sun due to
their very large distended envelopes.
They are pulsating due to the entire star expanding and
contracting over long time periods (~100+ days)
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Kepler’s laws – gold standard for “weighing” stars
1. Orbits are ellipses with sun at one focus
2. Equal areas swept out in equal time
3. Harmonic law: Square of the period (P) is proportional to the
cube of the semimajor axis (a). -- Gold standard for
determining masses in the universe – exoplanets and binary
stars.
Kepler’s law
P2 = a3 / (m1 + m2)
P = orbital period (years)
a = Distance between the two bodies (expressed in astronmical
units [AU] – distance from earth to sun)
1 AU = 107.5 sun diameters or 215 sun’s radius
m1, m2 = mass of the two bodies orbiting each other (solar masses)
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Measuring Distances…
First: Lets talk about time (JD or Julian
Date)
Then brightness of stars…
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JD or Julian Date
• The Julian Day Number (JDN) is the integer assigned
to a whole solar day in the Julian day count starting
from noon Universal time, with Julian day number 0
assigned to the day starting at noon on January 1,
4713 BC, proleptic Julian calendar
• For example, the Julian Date for 00:30:00.0 UT
January 1, 2013, is 2,456,293.520833.
• Universal time is the time in Greenwich England
(prime meridian)
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Brightness of Stars
• Brightness measured as luminosity or magnitude
– Luminosity is the total energy output of a star
• Depends on size and surface temperature
• Usually measure relative to our sun, e.g., 4 times our sun.
– A star’s magnitude is the logarithm of its luminosity
– Apparent magnitude (m) [what we see] – is determined by four
factors
• Its temperature or color (wattage of a light bulb)
• Its size
• How far away it is
• If it is obscured by dust (extinction)
– Absolute magnitude (M)
• Magnitude of a star when viewed from a fixed distance
• Most abs magnitudes will be a negative number (bright) 48
Brightness of a star: A star’s magnitude
• Magnitude is more often used to describe an objects
brightness.
• The higher the magnitude the dimmer the object.
– The apparent magnitude of our sun is -26.7
– The apparent magnitude of a full moon is -12.6
– The apparent magnitude of the Sirius is ~ -1
– Dimmest star you see (in Wilmington) ~+3.5
– Dimmest star you see in a dark sky location ~+5.5
• The absolute magnitude is the magnitude of the star / object if
it was place a fixed distance away (10 parsecs -- later).
• The absolute magnitude of our sun is ~ +4.8
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Distances
• Astronomical unit. Average distance between the earth and
our sun. (AU = 1.496x1011 meters or 97 million miles or
about 8.3 light minutes) This is a small unit of measure.
– Used for interplanetary measures and for distances
between stars in binary star systems (Kepler’s Laws)
• Light years. The distance light travels in a year
– LY = 9.46x1015 meters, 6.33x104 AU
• Parsec [pc]. The distance to an object that has a parallax of 1
arc second (next slide)  preferred unit by astronomers
pc = 3.26 LY = 2.06x105 AU = 3.086x1016 meters
• Kiloparsecs (Kpc)  1000 parsecs (103 parsecs)
• Megaparsecs (Mpc)  1 million parsecs (106 parsecs)
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• Geometric parallax  Gold standard for distances
– 1 Parsec = 3.09 × 1016 meters
• parsec - (pc): distance at which an object would have a parallax of
one arc second. Equals approximately 3.26 light years or about
206,265 astronomical units
Star appears to move
with season
Don’t move
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Spectroscopic Parallax
1. Measure the spectrum of a star. Lines in the spectra will
indicate if it is a main sequence star . The star needs to be
bright enough to provide a measurable spectrum, which is
about 10 000 parsecs.
2. Using the star spectra or using the UVB index, make
certain that it is on the main sequence, deduce its spectral
type (O, B, A, F, G, K, M, L)
3. From the spectral type deduce its absolute magnitude [M]
(H-R diagram or table)
4. Measure the apparent magnitude (m). Knowing the
apparent magnitude (m) and absolute magnitude (M) of
the star, one can calculate the distance modulus (m-M)
and the actual distance in parsecs – next slide.
Good for stars that are <~ 10,000 parsecs from us (or 32,600
light years) – most of the stars in our galaxy.
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 Distance modulus is
m-M if there is no interstellar dust (or extinction)
 If there is interstellar dust then distance modulus is
((m-E)-M) where E is the extinction magnitude
The larger the distance modulus the further away the object is.
Little m is usually >+10
Capital M is usually small – many times negative,
E can be as much a 1 or 2 (magnitudes of extinction due to dust in
our galaxy)
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Relationships between distance
modulus, luminosity, distances in
parsecs and absolute magnitude
Msun = 4.8 (absolute magnitude or our sun)
Astronomical unit [AU] = average earth- sun distance
1 AU = 1.496 x 108 km
Diameter of our sun = 1.391 x106 km
1AU = 107.5 sun diameters
What is distance modulus for our sun?
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Instability gaps on
an H-R diagram for
the pulsating class
of variable stars
Period of pulses
scale with absolute
brightness of the
star
“Period-luminosity
relationship”
•
http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_pulsating.html
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Period-Luminosity Relationship
equation for type 1 Cepheid
For Type I, Type II
Cepheids and RR Lyrae
Cepheids named after the
first star discovered in the
constellation Cepheus (up
north)
Note this is luminosity –
these stars are much
brighter than our sun.
•
M = -2.81* log(P)-1.43
P is period in days
http://outreach.atnf.csiro.au/education/senior/astrophysics/variable_cepheids.html
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Light curve for Delta Cephei
• Saw tooth curve
for Type 1
Cepheid variable
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RR Lyrae and Cepheid stars as standard candles
 Find the period.
 This gives the luminosity or its absolute magnitude
 Measure the apparent magnitude.
 Determine the distance from the apparent and absolute
magnitude (distance modulus) (and an estimate of the
extinction [E])
The same applies to RR Lyrae variable stars. Once you know that a
star is an RR Lyrae variable (eg. from the shape of its light curve),
then you know its luminosity
M = -2.81* log(P)-1.43
Type 1. P is period in days
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Type Ia supernovae is
where a white dwarf
collapses because it
has pulled too much
material from a
nearby companion
star onto itself.
Because the type 1a “blows
up” at the same mass limit
(see earlier discussion)
(Chandrasekhar limit ~1.4x
mass of our sun) they have
about the same absolute
magnitude at its peak
brightness  Standard candle
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Using Type Ia supernovae as a standard
candle
• Because a type Ia “explodes” at the Chandrasekhar
limit, all type Ia SN are about the same brightness
– Type 1a have an absolute magnitude of
about M~ -19.5 (that is a negative sign)
• Observed in distant galaxies.
• Observe a supernovae as it occurs,
• Construct its light curve
• From the light curve determine if it is a type 1a and
estimate is maximum apparent magnitude (m)
• Distance modulus is then (m+19.5) for Type Ia
supernovae (m is apparent magnitude)
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Red shifting a star’s spectrum
Wavelength of light (nanometers, nm)
1 nm = 1x10-9 meters
Increasing red shift
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Hubble’s law (measurement to very distant
galaxies)
Fundamental parameter  measure of the expansion of our universe
Hubble’s Law:
d = Vr
or for small distances d = z * c (z < 0.5)
Ho
Ho
d = distance in megaparsecs (millions of parsecs)
Vr is recessional velocity (km/sec)
Measure using red shift of the light spectrum of a galaxy
Ho is Hubble’s constant, ~75 km/sec / megaparsecs
z is the red shift = wavelength of the observed light
wavelength of the emitted light
-1
C is the speed of light (3x 105 km/sec)
Problem: if wavelength of the observed light is 440 nm and
the wavelength of the emitted light is 400 nm
What is Z?
What is recessional velocity?
What is the distance using Hubble’s law? In mpc? In light years?
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Answer to problem
z = 440 -1 = 1.1 -1 = 0.1
400
Vr = 0.1 x 3x 105 (km/sec) = 3x 104 (km/sec)
What is the distance using Hubble’s law?
D = 3x 104 km/sec / (75 km/sec/mpc [kilometers/second/megaparces])
= 3/7.5 x 103 megaparces (mpc) = 0.4 x 103 mpc = 400 mpc
= 3.26 light year / pc x 106 pc/mpc x 400 mpc = 1304 x 106 light years
or = 1.3 x 109 ly
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• If the apparent magnitude of a star is +7 and it has a
parallex of 0.01 arc seconds, what is its luminosity relative
to our sun?
• What is the mass of the star in number of suns?
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More info…
An star’s is named using its constellation and letter of
multiple letter designation. So…
RY Sagittarii is in the constellation Sagittarius
(summer sky) and counting up using the alphabet (a, b,
c, d, e… z, AA, AB,…. ) it is star RY in this
constellation.
A class of stars (like the Cepheid variables or RR Lyrae
variables) are named after the first star discovered in
that class of stars. So the first Cepheid variable was
discovered in the constellation of Cepheus. The RR
Lyrae variables are named after the RR Lyrae (in the
constellation of Lyra [string instrument]). The T Tauri
stars were named after T Tauri (a star in Taurus).
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J075141/J174140, - Binary white dwarfs that will evolve to AM CVn type objects
NGC 2392 – Eskimo nebulae – planetary nebulae in Gemini, m=10.1
SNR 0509-67.5 – type 1a SNR in the Large Magellanic Cloud in Dorado
constellation
Omicron Ceti Mira variable: the first in a class of very long period variable stars
SN 2011fe a type 1a supernovae in M101 (pinwheel galaxy) in Ursa Major
SNR G1.9+0.3, the most recent supernovae in the Milky Way galaxy.
NGC 2440, – planetary nebulae in Puppis, ~ 4000 ly from earth
Henize 2-248, - planetary nebulae in Aquila with binary double white dwarf
system.
Henize 3-1357 (Stingray Nebula), youngest planetary nebulae known.
Tycho’s SNR, (B Cas) Type 1a supernovae observed by Tycho Brahe in 1572
SS Cygni, Cataclysmic variable or “dwarf novae” -- a close binary star system
M15, a globular cluster in Pegasus ~12 billion years old
HM Cancri two dense white dwarf stars orbiting each other, generating x-rays
Sirius A & B, brightest star in the sky is a binary star system. The B component
is a white dwarf
NGC 1846 A globular cluster of stars (like M15) in the Large Magellanic Cloud
that appears to contain a green planetary nebulae(!)
J075141 & J174140, -Two binary white dwarf systems - known by their
shortened names of J0751 and J1741 – that are predicted to evolve into AM
CVn type of objects
- Observed in X-rays by NASA's Chandra X-ray Telescope and ESA's
XMM-Newton telescope. Neither Chandra nor XMM-Newton detected
any X-rays from these systems.
- Predicted to give off gravitational waves causing the orbits to decay and
eventually pulling material from the less massive white dwarf to the
more massive (and smaller) white dwarf.
- Once mass accumulates, thermonuclear explosion will occur causing a
type 1a supernova or a type .1a outburst - .1a is more likely given the low
combined mass of these systems.
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NGC 2392 also known as NGC2392 or Eskimo nebulae or
Clownface nebulae or Caldwell 39. It is a bipolar (two lobes)
with a double shell, planetary nebulae.
2,870 light years away in the constellation of Gemini with an
apparent magnitude of 10.1
Represents the death of a near
solar mass star.
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SNR 0509-67.5 – type 1a supernovae remnant in the LMC in
the constellation of Dorado (southern hemisphere).
160,000 light years away
Light echo off of interstellar dust allowed astronomers to
confirm that it was a type 1a SN
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Omicron Ceti a giant red star in the constellation of Cetus.
Binary system with a long term variable red giant (Mira A) as
the primary and white dwarf as the secondary. Mira A is on
the asymptotic giant branch (AGB) of the
H-R diagram -- thermally pulsating
Mira A (red giant)
UV light showing tail
optical
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SN 2011fe a type 1a supernovae in M101 (pinwheel galaxy) in
the constellation of Ursa Major (big dipper). Relatively close
type 1a SN allowing astronomers to better calibrate the use of
type 1a SN as “standard candles” to measure distances in the
universe.
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What is the distance modulus to SN 2011fe (use visual
magnitude)
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SNR G1.9+0.3, the most recent supernovae to have occurred in
the Milky Way galaxy. In the constellation of Sagittarius.
Type 1a SN that would have been visible in 1868 had it not
been obscured by dust in the plane of our galaxy.
NGC 2440 – planetary nebulae in Puppis, ~ 4000 ly from earth
Central star (HD62166) is one of the hottest known (200,000K)
m=17.5
Luminosity = 1100 suns
Nebulae glows as a result of intense UV radiation from the
dying star.
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Henize 2-248 - planetary nebulae in Aquila with binary double
white dwarf system. The pair are expected to merge and
explode in a Type Ia supernova. The inspiralling of the stars is
caused by the emission of gravitational waves, resulting in the
loss of orbital energy. The explosion is due to the combined
mass of the merged star exceeding the Chandrasekhar limit of
1.4 solar masses. This is the first candidate for binary double
white dwarf star merger.
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Henize 3-1357 (Stingray Nebula), youngest planetary nebulae
known.
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Tycho’s SNR, (B Cas) Type 1a supernovae observed by Tycho
Brahe in 1572 in Cassiopeia
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SS Cygni Variable star in Cygnus, one of the most observed
variable stars in the sky. Cataclysmic variable or “dwarf
novae” consisting of a close binary star system. One is a red
dwarf (of failed sun, ~0.4 Msun) the other is a compact white dwarf (~0.6
Msun) separated by ~100,000 miles (very small distance). Period of orbit
~6.5 hours. The system is about 372 ly away. Changes in the rate of flow of
material into the disk can cause it to suddenly burn much hotter and
brighter. Not only does the disk radiate more light, but it can heat the
surface of the companion star, causing it to glow more brightly, too.
Flow of
material to
white dwarf
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M15, Messier 15, a globular cluster in Pegasus ~12 billion years
old, the first planetary nebulae in a globular cluster, Pease 1, is
in M15. 35,000 ly away.
~100,000 gravitational bound stars
Possible black hole in its core.
Contains a Double neutron star system
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HM Cancri, two dense white dwarf stars orbiting each other,
generating x-rays. Also known as RX J0806.3+1527. Period is
321.5 seconds. 50,000 miles apart (very close),
The white dwarfs will eventually merge as a result of the loss of
orbital energy by the generation gravity waves. Mass of each
white dwarf is estimated to be ~0.5 suns.
Artist’s depiction
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Sirius A & B - brightest star in the sky is a binary star system.
The B component is a white dwarf. 8.6 ly away, m= -1.46
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NGC 1846. A globular cluster of stars (like
M15) in the Large Magellanic Cloud that
appears to contain a green planetary nebulae(!)
Unusual since globular clusters are VERY old and
planetary nebulae are relatively young.
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