Download Reach for the Stars – Div. B

Reach for the Stars – Div. B
Help session: March 6th, 2016
Properties and evolution of stars especially
star forming regions and supernova remnants
Resources for test
“Two 8.5 x 11 inch two sided sheet”
Test on March 19, 2016
Test will include questions about a series of
images projected onto the front of the room.
1
The room will be dimly lit (planetarium
program is part of test)
(red) flashlight strongly recommended.
2
3
4
Study points
• Download planetarium software, Stellarium
(http://www.stellarium.org/) is good and free!!!
• Practice recognizing pattern of stars of
constellations and stars listed on the rules sheet.
• Google the objects on the list and try to under
stand how they fit into the birth and death of stars.
• Try to understand what a stars magnitude,
luminosity and distance modulus means.
Understand the inverse square law..
Memorization and conceptual understanding is
required.
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Test is in 2 parts
• Part 1– planetarium program
– Identical show repeated 3 times every hour
– Timed power point presentation
– Circles put around objects, constellations
and stars  “name this”
– Planets and the moon are “off”
• Part 2 – Normal test, multiple choice, fill
in blanks. Pictures shown as part of a
timed power point presentation
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Constellation and object in it
Aquila
Altair (star), W49 region (Weterhout 49) HII region
Aquarius
NGC7293, Helix Nebula
Auriga
Capella (star)
Bootes
Arcturus (star)
Canis Major
Sirius (star)
Canis Minor
Procyon (star)
Carina*
NGC3603 (giant molecular cloud, HII region), NGC3372 (great nebulae)
Cassiopia
Cas A, Tycho’s SNR , NGC281, W3 Main
Dorado*
30 Doradus, LMC
Cygnus
Deneb (a bright star), Cygnus X-1
Gemini
Castor & Pollux (two stars in Gemini)
Hydrus*
NGC 602 (young open cluster of stars)
Leo
Regulus (star)
Lyra
Vega (star)
Monoceros
Rosette Nebula
Ophiuchus
Zeta Opiuchi, Keplar SNR
Orion
Betelgeuse, Rigel (stars) & M42 (Orion Nebula)
Perseus
Algol (variable star)
Sagittarius
Sgr A*– Sagittaris A – a radio source that is a massive black hole and center of our
Milky way Galaxy
M17, Omega or Swan or Horseshoe Nebulae or Lobster Nebulae
M8 Lagoon Nebulae
Scorpius
Antares (red giant star that is the body of the scorpian)
Taurus
Aldebaran (star), M1 (the crab Nebula)
Ursa Minor
Polaris (North Star)
Ursa Major
Mizar & Alcor (second star(s) in the handle – a binary)
Virgo
Spica (star)
What you may need to know
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• W49A is an active star forming region lying at a distance
of ~11 kiloparsecs from the Sun in the constellation of
Aquila. W49A is clearly very young, with observations
revealing several massive OB clusters lying within a
giant molecular cloud that is still at an early stage of
disruption. Large HII region.
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NGC7293
A mere seven hundred
light years from
Earth, in the
constellation
Aquarius, a sun-like
star is dying. Its
last few thousand
years have produced
the Helix Nebula (NGC
7293), a well studied
and nearby example of
a Planetary Nebula,
typical of this final
phase of stellar
evolution for a solar
mass star.
NGC 3603 is a starburst region: a cosmic factory where stars form frantically
from the nebula’s extended clouds of gas and dust. Located 22 000 light-years
away from the Sun, it is the closest region of this kind known in our galaxy,
providing astronomers with a local test bed for studying the intense star
formation processes, very common in other galaxies, but hard to observe in
detail because of their large distance. It is a large molecular cloud and HII
region.
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Carina Nebula (also known as the Great Nebula in Carina, the Eta
Carinae Nebula, NGC 3372, as well as the Grand Nebula) is a
large bright nebula that has within its boundaries several
related open clusters of stars. It contains the large OB
association, Carina OB1.
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NGC281
. NGC 281 is an H II
region in the
constellation of
Cassiopeia and part of the
Perseus Spiral Arm. It
includes the open cluster
, the multiple star , and
several Bok globules.
Colloquially, NGC 281 is
also known as the Pacman
Nebula for its resemblance
to the video game
character.
Bok globules are dense
dust and gas pockets
likely containing new
stars
Objects
• Tycho
Super Nova
Remnant
(Type 1a)
Cassiopeia
• Cas A
(Cassiopeia A)
Type II Super Nova
remnant
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"W3“ is a Giant Molecular Cloud which lies around 6200 light years away in
one of the spiral arms of our Galaxy. W3 Main is a region where many massive
stars are being born. But these observations discovered that many brown
dwarfs, small objects with too little mass to become stars, are also
forming. Large HII region and molecular cloud.
• Optical and
infrared
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, green and blue represent lower and higher-energy X-rays, respectively, while
red shows optical emission. Hundreds of X-ray sources are revealed in this
central region of W3 Main. These bright point-like objects are an extensive
population of several hundred young stars, many of which were not found in
earlier infrared studies. These Chandra data show that W3 Main is the
dominant star formation region of W3.
W3 REGION IN x RAYS
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Objects
• 30 Doradus
(Tarantula
Nebulae)
Has molecular clouds
and HII regions
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The Tarantula Nebula (also known as 30 Doradus, or NGC 2070) in the
Large Magellanic Cloud (LMC).
The Tarantula Nebula has an apparent magnitude of 8. Its distance is
about 49 kpc or 160,000 light years. Its absolute brightness is so
great that if it were as close to Earth as the Orion Nebula, the
Tarantula Nebula would cast shadows. It is the most active and
largest starburst region known in the Local Group of galaxies. It has
an estimated diameter of 200 pc or 650 light years. The nebula resides
in the Large Magellanic Cloud.
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Cygnus X-1
is a well-known black
hole and galactic Xray source in the
constellation Cygnus.
It was discovered in
1964 during a rocket
flight and is one of
the strongest X-ray
sources seen from
Earth, Cygnus X-1 was
the first X-ray source
widely accepted to be
a black hole and it
remains among the most
studied astronomical
objects in its class.
Cygnus X-1
Artist imagination
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NGC 602 is the designation for a particular young, bright open cluster of stars
located in the Small Magellanic Cloud, a satellite galaxy to our own Milky Way.
Radiation and shock waves from the star cluster has pushed away much of the
lighter surrounding gas and dust that compose the nebula known as N90, and
this in turn has triggered new star formation in the ridges (or "elephant trunks")
of the nebula.
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Rosette Nebula (also known as Caldwell 49) is a large, circular H II region
located near one end of a giant molecular cloud in the Monoceros region of
the Milky Way Galaxy. The open cluster NGC 2244 (Caldwell 50) is closely
associated with the nebulosity, the stars of the cluster having been formed
from the nebula's matter.
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Zeta Ophiuchi is an enormous star with more than 19 times the Sun's mass
and eight times its radius. The stellar classification of this star is O9.5 V, with
the luminosity class of V indicating that it is generating energy in its core by
the nuclear fusion of hydrogen. This energy is being emitted from the outer
envelope at an effective temperature of 34,000K, giving the star the blue hue
of an O-type star.
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Supernova 1604, also known as Kepler's Supernova, Kepler's Nova or Kepler's
Star, was a supernova of Type Ia that occurred in the Milky Way, in the constellation
Ophiuchus. Appearing in 1604, it is the most recent supernova to have been
unquestionably observed by the naked eye in our own galaxy, occurring no farther than
6 kiloparsecs or about 20,000 light-years from Earth.
Visible to the naked eye, Kepler's Star was brighter at its peak than any other star in
the night sky,
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M42 Orion Nebulae
star forming region
Large star forming
region in Orion
HII regions glow
from the radiation
from the new young
stars in the core of
the nebulae.
Objects
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M17 or NGC 6618
17th object in the
Messier catalogue.
Omega or Swan or
Horseshoe Nebulae or
Lobster Nebulae.
region of star
formation and shines
by excited emission,
caused by the higher
energy radiation of
young stars. these
stars are not obvious
in optical images, but
hidden in the nebula.
HII region. In
Sagittarius.
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•
Lagoon Nebula(catalogued as Messier 8 or M8, and as NGC 6523) is a
giant interstellar cloud in theconstellation Sagittarius. It is classified as
an emission nebula and as a H II region.
• The Lagoon Nebula was discovered by Giovanni Hodierna before 1654 and
is one of only two star-forming nebulae faintly visible to the naked eye from
mid-northern latitudes. Seen with binoculars, it appears as a
distinct oval cloudlike patch with a definite core. In the foreground is
the open cluster NGC 6530.
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M17 NGC6618
Omega Nebula
M8
Sgr A
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Objects
• Sgr A Sagittarius
A – X-ray source
(black hole) at
center of our
galaxy
• M1 Crab Nebulae
Type II Supernova
Remnant in Taurus
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Star Charts
~8:00 pm in the evening before the day of the
competition in Dover Delaware
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All sky
(South at
bottom)
M42
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All sky
(South at
bottom)
Constellations
now shown
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North
33
Mizar and
Alcor in the
Handle of the
big dipper
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North
35
East
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South
Rosette
Nebulae
M42
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Zoom in on West,
M42
M1
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Star Charts
~5:00 am in the morning of the day before
the competition in Dover Delaware
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North,
Tycho SNR
Cas A
NGC281
W3 main
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East,
Cygnus X-1
W49
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South,
Cygnus X-1
W49
Keplar SNR
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Zoom in on South
M17
M8
Sgr A
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Zoom in on West,
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Southern
Hemisphere
NGC3603
Large Magellenic
cloud (LMC) with
30 Doradus
Small Magellenic
cloud (LMC) with
NGC602
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solar system condensed out of
intersteller gas and dust
• Gigantic gas and dust clouds (left
over material spewed out by
supernovae) condensed b by self
gravity into globules.
• The globules spun up due to
conservation of angular
momentum. Became a spinning
disk.
• The gas reached a critical density
at the center and a star was
formed.
• Can’t see the new star because it
is “cloaked” in the gas and dust.
• Planets form as the surrounding
material coalescences,
Early solar system evolution
• Early in the sun’s life (as the planets were forming), the
sun had a very strong solar wind (from flares)
– Charged particles streaming out of the suns atmosphere
– This solar wind was produced as the nuclear reactions in the
core of the sun started.
– The sun produces a weaker solar wind today that fluctuates with
the sunspot activity of the sun – more sunspots, more solar wind.
• Solar wind “storms” cause the Northern Lights (auroras)
• This early strong solar wind “pushed” much of the
material that had not been formed into planets out to the
farther reaches of the solar system
Stellar Evolution
• Most stars are born in open clusters
– Pleiades (M45), NGC602 are examples
– W49A, M42 (Orion Nebula), M17, NGC3603, NGC3372, NGC281
W3, 30 Doradus are examples of a cluster in the making
– HII regions have many of molecular clouds that are forming new
stars as open clusters.
– Open clusters don’t stay as open clusters very long
• Stars that are less than ~2x the mass of our sun die as
planetary nebulae
– NGC7293 (Helix nebulae)
• High mass stars die as supernovas with remnants (Type II
supernovae remnants )
– M1 (Crab Nebula), Cas A,
Other special binary star systems
– Tycho’s SNR die as type 1a super novae remnants
– Type 1a are important measuring sticks of the universe
– Cygnus X-1 is a binary star system with one component as a black
hole (sucking material from its companion and making xrays)
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HII regions and molecular clouds
• The radiation from new hot stars embedded
in molecular gas and dust clouds will ionized
the gas – that is, an electron will be stripped
from the atom of the gas. Much of that gas
is hydrogen. The region of the gas cloud
where hydrogen becomes ionized is called a
HII region. This region is also called an
“emission nebulae”
• HII regions show very characteristic
emission lines in a spectroscope.
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Brightness of Stars
• Needed to understand the HertzsprungRussell diagrams (H-R diagrams)
• Brightness measured as luminosity or
magnitude
– Luminosity is the total energy output of a star
• Depends on size and surface temperature
– A star’s magnitude is the logarithm of its
luminosity
– Apparent magnitude (m) – four factors
•
•
•
•
Its temperature or color (wattage of a light bulb)
Its size
How far away it is
If it is obscured by dust
– Absolute magnitude (M)
• Magnitude of a star when viewed from a fixed distance
and without any dust in the way.
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Luminosity, L
• Total amount of energy emitted by the star,
• Depends on the surface temperature (same as
color)
–
–
–
–
Hot (Blue)
Yellow
Orange
Cool (red)
• Depends on the size
– The larger the star, the more surface area to emit the
energy and the brighter the star
• Measured relative to our sun (sun =1)
– L>1 for Stars emitting more energy than our sun
– L<1 for Stars emitting less energy than our sun
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A star’s magnitude as brightness
• Magnitude is more often used to describe an objects
brightness.
• The higher the magnitude the dimmer the object.
–
–
–
–
–
The apparent magnitude (lower case m) 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 sight +5.5
• The absolute magnitude (capitol M) is the magnitude
of the star / object if it was place a fixed distance away
(10 parsecs = 32.6 light years).
• Our sun’s absolute magnitude is 4.8
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Distance Modulus
• It is a way that astronomers measure large
distances
– it is simply the apparent magnitude less the
absolute magnitude or = m – M
– The higher the number the more distant the
object
– Our Sun’s distance modulus is
-26.7-4.8 = -31.5 this is a very low number
meaning that the sun is very close to us!!
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Inverse square law
• The brightness of an object (star)
decreases by the square of the distance
between the observer and the object.
– if a light bulb looks like a 100 watt bulb at 10
feet,
– then at 100 feet it will look like a 1 watt bulb.
Brightness (at distance b)
= brightness (at distance a) x (a/b)x(a/b)
Or = brightness (at distance a) x (a/b)2
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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 (bright lines against a
dark background) are given off by nebulae –
glowing gas clouds like the HII regions described
above.
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Dark (absorption) lines in emission spectra (of stars) or
bright lines in nebulea
• Electron transition from a lower energy state to a higher energy
state  adsorption line
• Electron transition from a higher energy state to a lower energy
state  emission line
• Below is the Balmer series of lines associated with electron
transition in the hydrogen atom to and from the second lowest
energy level
• H-α (“hydrogen alpha”) is an important line in both emission and
absorption spectra. It has a wavelength of 656.3 nm or 6563
Angstroms
HII regions show the 656.3 nm emission
Absorption line seen in stars
are used to classify them
Other elements  next slide
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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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Example of a star’s
spectra
• Strong
hydrogen
lines, B, A,
and F type
star
• No helium
lines not a B
star.
• ionized
calcium (the H
and K lines),
• This is an F
type star
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Hertzsprung-Russell Diagram
-- Each dot is a star
Y axis is always
brightness or
relative
luminosity
X axis is always
temperature,
color or spectral
class
A is main
sequence
B is horizontal
branch
C are
supergiants
•
http://outreach.atnf.csiro.au/education/senior/cosmicengine/stars_hrdiagram.html
D are white 59
dwarfs
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Low mass star like our sun
stops at carbon formation....
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And fluffs off its outer
layers to make a
planetary nebulae and a
white dwarf star. ....
NGC 7293,Helix nebulae
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But a high mass star,
have 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 and.....
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It goes boom!!!!... A
supernovae!!! (this is
the M1, the Crab
Nebulae)
A spinning neutron
star is inside this
nebulae – called a
pulsar.
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• Cas A
(Cassiopeia A)
Type II Super Nova
remnant
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The ultimate fate of a star is
dictated by one property: its
mass
Low mass stars fuse hydrogen
to helium very slowly and live for
a long time on the main
sequence.
High mass stars consume their
fuel very rapidly and are on the
main sequence for a short time
Low mass stars end up as white
dwarf,
High mass stars as neutron
stars or black holes after blowing
up as type II or 2 supernovae
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2
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Recap
1a. Stars are categorized by their spectral class
1b. Hertzsprung-Russell (H-R) diagram is a way to represent the evolution
of stars
2. The Main sequence is the location of stars on the H-R diagram where
stars spend most of their lives
3. Stars remain stable for long periods (on the main sequence) by
balancing the force of gravity with the energy generated by nuclear fusion
of hydrogen to helium in the star’s core.
4. Red giant stars are generally caused by nuclear fusion in the shell and
not the core. Elements heavier than helium are fused to carbon and then
iron in the core of these stars.
5. Mass is the single most important property of a star that dictates its
ultimate fate.
6. A more massive star has a shorter lifetime
7. Stars in a single cluster are all “born” at the same time
8. An old star cluster will show stars in many stages of life as a result of the
different masses of the stars formed in the cluster.
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