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The Birth of Stars

QuestionAnswer
Hydrostatic Equilibrium- a balance of gravity pulling in and.... pressure from heat pushing out
Luminosity is the... total energy radiated by a star
Nuclear Fusion- joining of two nuclei to form a different one
Nuclear Fusion requires high temp and density to... overcome electrical repulsion of protons
a star becomes stable when the outward forces of expansion from the energy released in nuclear fusion reactions.... balance the inward forces of gravity
very massive stars are: rare
low mass stars are: common
we are "star stuff" because the elements necessary for life were... made in the stars
individual stars form in fragments of much larger clouds as gravity draws.... gas together
forming stars are surrounded by spinning disks and often emit jets of ____ out of their ____ and _____ poles forming stars are surrounded by spinning disks and often emit jets of GAS out of their NORTH and SOUTH poles
when massive stars die they.... explode and scatter their content such as newly produced heavy elements
stars shine with energy produced from... nuclear fusion in their cores
how far does the sun sit from the center, to the edge of the disk? 2/3 of the way, about 25000 ly
the sun revolves around the galaxy about once every... 250 million yrs
nebulae are... cold interstellar clouds of dust and hydrogen gas, the birth place of stars
the gas between the stars is called the? interstellar medium
large clouds of gas are illuminated by the... hot and bright new stars
interstellar medium is made out of 2 components: gas (75% hydrogen, 25% helium) a little of other gases, and dust
any interstellar cloud of gas and dust is called a? nebula
evidence of nebulae consist of... spectral lines and reddening of stars
an emission nebula is a... nebula with a characteristic emission line spectrum of a hot, thin gas
the vast amounts of UV Radiation emitted by the close of hot, type ___ or type ___ stars are absorbed by... the vast amounts of UV Radiation emitted by the close of hot, type O or type B stars are absorbed by the hydrogen atoms in the nebulae
emission nebulae are referred to as.. H II Regions
a dark nebula is a nebula so opaque that it... blocks visible light from the stars behind the nebula
a dark nebula region consists of the following: higher concentration of dust grains, and they look like dark patches
a reflection nebula does not produce its own light but it... scatters star light
a reflection nebula region consists of the following: it scatters light due to dust grains, lower concentration of dust grains compared to a dark nebula, the scattering gives off a blue colour
Interstellar extinction: the intensity of star light is reduced as... light passes through the interstellar medium
interstellar reddening: when light from a star passes through the interstellar medium, dust particles absorb or.... scatter blue light allowing red light to pass through, like a sunset on earth. the star looks red
interstellar reddening: long wavelength infrared light passes through a cloud more easily than... visible light
interstellar reddening: observations of infrared light reveal... stars on the other side of the cloud
giant molecular clouds: in certain cold regions of interstellar space atoms... combine to form molecules
stars are born in molecule clouds consisting mostly of... hydrogen molecules
stars form in places where gravity can... overcome thermal pressure in a cloud
the interstellar medium: infrared observations can directly detect... dust in the interstellar medium
the interstellar medium: some molecules in the cold gas emit in the infrared... infrared observations can detect very cold clouds of gas
birth of stars: the birth and life of a star can be described as a battle between two forces: gravity vs internal pressure
birth of stars: gravity always wants to... collapse the star, internal pressure holds up the star
birth of stars: the amount of gravitational force depends on the... mass
birth of stars: gravitational potential energy is turned into... heat as a star collapses
formation of stars from the interstellar medium: in the densest clouds hydrogen can exist as molecules rather than as atoms, these clouds are called... molecular clouds
an interstellar molecular cloud: star formation begins when part of the interstellar molecular cloud contracts under its own... gravitational attraction
an interstellar molecular cloud: denser regions in the clouds are favorable for... star formation
an interstellar molecular cloud: the gravitational collapse overwhelms the... pressure, colder regions are more favorable since they are low pressure regions
an interstellar molecular cloud: these cold dense regions of clouds collapse under its own weight to form... clumps, future clouds
contracting cloud: star formation is is triggered when a sufficiently massive pocket of gas is... squeezed by some external event
contacting cloud: Material flowing out of protostars cause shock waves that... trigger regions nearby to collapse
contracting cloud: A supernova explosion of a dying star can compress the surrounding gas triggering a... collapse
A star-forming cloud colliding with a shock wave can be... compressed and break into fragments
Some of these fragments (star forming cloud colliding with a shock wave) can become dense enough to collapse under gravity and... form stars.
fragmentation of a cloud: Gravity within a contracting gas cloud becomes.... stronger as the gas becomes denser
fragmentation of a cloud: Gravity can therefore overcome pressure in smaller pieces of the cloud, causing it to break apart into... multiple fragments, each of which may go on to form a star
fragmentation of a cloud: Each lump of the cloud in which gravity can overcome pressure can go on to become... a star
fragmentation of a cloud: A large cloud can make a whole... cluster of stars
the dense opaque region at the center is called a ______- an embryonic object at the dawn of star birth PROTOSTAR
observing newborn stars: Observing the infrared light from a cloud can reveal the... newborn star embedded inside it
The rotation speed of the cloud from which a star forms increases... as the cloud contracts
Rotation of a contracting cloud ____ for the same reason a skater _____ as she pulls in her arms speeds up
Collisions between particles in the cloud cause it to... flatten into a disk
formation of jets: Jets are observed coming from... the centers of disks around protostars
Protostar looks starlike after the surrounding gas is blown away, but its thermal energy comes from... gravitational contraction, not fusion
Contraction must continue until the core becomes... hot enough for nuclear fusion 107 K (10 000 000 K)
Contraction stops when the energy released by core fusion balances energy radiated from the surface... the star is now a main-sequence star
When thermonuclear reactions start at the center of a protostar, we say... a new star is born.
summary of star birth: 1. Gravity causes gas cloud to... shrink and fragment
summary of star birth: 2. Core of shrinking cloud... heats up
summary of star birth: 3. When core gets hot enough, fusion begins and... stops the shrinking
summary of star birth: 4. New star achieves long- lasting state of... balance
evidence of star birth: we have observed... – bipolar flow from young stars. – star forming regions (e.g. Orion Nebula). – Young Star clusters
Stages of Star Formation on the H-R Diagram: Life track illustrates star’s surface temperature and.... luminosity at different moments in time
a star remains on the main sequence as long as it can... fuse hydrogen into helium at its core
the mass of a main sequence star determines its... core, pressure and temperature
stars of higher mass have higher core temperature and rapid fusion, making those stars... both more luminous and short lived
stars of lower mass have cooler cores and slower fusion rates giving them... smaller luminosities and longer life times
high mass stars: red giant, supernova, black hole, neutron star
mid mass stars: red giant, planetary nebula, white dwarf
low mass stars: red giant, white dwarf, cold lump of carbon
_______ _______ ______ occur in the core, releasing gamma and X-ray radiation. This radiation moves through the radiation zone from particle to particle, eventually heating gases at the bottom of the convection zone Hydrogen fusion reactions
Convection cells carry energy to the surface, where it is emitted to space as... visible light, ultraviolet radiation, and infrared radiation
What happens when a star can no longer fuse hydrogen to helium in its core? Core shrinks and heats up
What happens as a star’s inert helium core starts to shrink Hydrogen fuses in shell around core
life history of a sunlike star: As the star contracts, H begins fusing very rapidly to... He in a shell around the core
life history of a sunlike star: Luminosity increases because the fusion rate is... higher
life history of a sunlike star: Size increases: red giant phase
life history of a sunlike star: Helium fusion requires higher temperatures than... hydrogen fusion
life history of a sunlike star: Helium fusion combines three He nuclei to make... carbon
life history of a sunlike star: The expansion of a star to giant or supergiant size _____ the star’s outer layers cools
life history of a sunlike star: The stars move toward the ___ ___ in the H-R diagram upper right
As a star evolves, its ____ and ____ change luminosity and temperature
HR Diagram: the top left area represents... hot, bright stars
HR Diagram: the top right area represents... cool, bright stars
HR Diagram: the bottom left area represents... hot, dim stars
HR Diagram: the bottom right area represents... cool, dim stars
Evolution from a gas cloud onto the Main Sequence: star shrinks from a large cloud to a.... spinning ball of gas, protostar heats up slightly
main sequence stage: Star burns hydrogen in its core • Star settles down onto the Main Sequence • Slight increase in temperature and luminosity
red giant stage: the hydrogen in the stars core starts to run out the star leaves the MS and swells to become a red giant temperature drops luminosity increases because the star is bigger
white dwarf stage: the core of the star is left no more burning in the core the star is a white dwarf star cools until it no can no longer be seen
the star ends fusion: • C and O from core helium burning • thin layer of He (the product of shell hydrogen burning
the star ends fusion: typical mass less than half, a solar mass to more than... one solar mass
the star ends fusion: size of... earth
the star ends fusion: In final stages of the formation of a planetary nebula nuclear burning in the central star... ceases
what happens when a white dwarf cools down? it forms a huge crystal, a generate diamond
white dwarfs with the same mass as the sun are about the same size as... earth
higher mass white dwarfs are... smaller
for some time, the surface several hundred thousand degrees few hundred million years -- the star cools and becomes a... white dwarf
burned-out stellar cinders are... hot and dim
after some billions of years, white dwarfs become... virtually undetectable
planetary nebulae are gaseous shells surrounding the... remnant carbon cores
a planetary nebulae is called so because... the greenish blue resembled uranus or neptune
a planetary nebulae is composed of ionized gases expelled by a... dying star
planetary nebulae: the fuel in the star's core becomes... totally depleted
planetary nebulae: the star begins to swell and shrink, throwing off its... outer layers
planetary nebulae: gas is puffed out into space and surrounds the star in a shell, forming a... planetary nebula
planetary nebula: luminosity... stays the same
planetary nebula: the very hot core becomes more visible as more and more layers are... shed
planetary nebula: the temperature of the star... increases dramatically
A star like our sun dies by puffing off its outer layers, creating a... planetary nebula
white dwarf limit: Chandrasekhar calculated the.... radius dependence in white dwarfs
white dwarf limit: mass increases so... the radius decreases
accretion disks: Mass falling toward a white dwarf from its close binary companion has... some angular momentum
accretion disks: The matter therefore orbits the white dwarf in an... accretion disk
nova: The temperature of accreted matter eventually becomes hot enough for... hydrogen fusion
nova: Fusion begins suddenly and explosively, causing a... nova
The nova star system temporarily appears much... brighter
nova: The explosion drives accreted matter out into... space
the white dwarf becomes more massive than... the sun
the white dwarf consists primarily of... carbon and oxygen
the white dwarf accretes matter from its companion relatively.. rapidly
the white dwarf becomes: nova outbursts relatively weak and eject only... little matter
Consequently, the white dwarf grows in... mass
thermonuclear supernova: accretion has raised the white dwarf's mass to the critical mass of about... 1.4 solar masses
thermonuclear supernova: the density and temperature in the star's center become so severe that... carbon starts burning explosively
thermonuclear supernova: within roughly one second, the burning front moves all the way to the surface, making the entire white dwarf one huge... nuclear fireball
thermonuclear supernova: the entire star explodes and... destroys itself
thermonuclear supernova: there is no stellar remnant
supernovae consist entirely of... heavier elements, there is almost no hydrogen
characteristics of supernovae: very bright, can determine their distances, can tell how fast they are going due to wavelength
big bang made 75% ____ and 25% ____ Hydrogen and Helium
helium fusion can make ____ in low mass stars carbon
high core temperatures allow helium to ____ with heavier elements fuse
core temperatures in stars with >8Msun allow fusion with heavy elements ending with... iron
advanced reactions make... heavier elements
iron is a dead end for fusion because nuclear reactions involving iron do not... release energy
When helium is depleted, fusion of heavier elements begins. This process is called... nucleosynthesis
Advanced nuclear burning occurs in... multiple shells
High-mass stars become supergiants after... core H runs out
Luminosity doesn’t change much but radius gets... far larger
iron builds up in the core until degeneracy pressure can no longer... resist gravity
after the degeneracy pressure cannot resist gravity, the core collapses, creating a... supernova explosion
fusion stops with iron (Fe) and a star with an iron core is... out of fuel.
Iron atoms cannot... fuse and release energy.
he core collapses due to reduced pressure converting the iron core into mostly neutrons. The electrons get pushed into the.... nuclei, with protons they form neutrons
On February 24, 1987, Canadian astronomer (Winnipeg) ____ ______ discovered at Las Campanas Observatory, Chile, the first supernova visible to the naked eye since Tycho’s supernova in 1604 Ian Shelton
Thanks to its early detection, this supernova designated SN 1987 A is the most... well-observed supernova in history
Detections of neutrinos coming from the supernova (SN) helped... confirm models of iron core collapse
energy and neutrinos released in a supernova explosion enable elements heavier than iron to form, including... gold and uranium
99% of sn energy is emitted to... neutrinos
1% of sn energy is converted into.... kinetic and heat energy of the ejecta
neutron stars typically have masses up to 3 solar masses and a diameter of aprox.... 10 km
neutron stars are similar to... giant atomic nuclei the size of a city
Gravity overwhelms pressure in the star's iron core when the core's mass grows to about... 1.4 solar masses
The Formation of a Neutron Star: when the cores mass grows to 1.4 solar masses, the core collapses which causes a.... release of an enormous amount of energy
The Formation of a Neutron Star: electrons and protons in the remnant are squeezed together to form... neutrons and neutrinos
white dwarf: electrons run out of room to move around. electrons prevent further collapse. protons and neutrons are still... free to move around
neutron star: electrons and protons combine to form neutrons. neutrons move out of room to move around. neutrons prevent... further collapse
black hole: gravity wins, nothing can... prevent collapse
using a radio telescope in 1967, ____ _____ noticed very regular pulses of radio emission coming from a single part in the sky Jocelyn Bell
Physics predicts that neutron stars should: Spin rapidly, perhaps... 100 to 1000 rotations per second
Physics predicts that neutron stars should: Be hot, with surface temperatures of... millions of degrees K
Physics predicts that neutron stars should: Have strong magnetic fields, up to a trillion times stronger than... the Sun’s or Earth’s magnetic fields
Physics predicts that neutron stars should: Despite their high temperature, neutron stars should be... difficult to detect, due to their small size
magnetic and rotational axii of a pulsar are... misaligned
like a ship in the ocean that sees only regular flashes of light, we see pulsars turn on and off as the... beam sweeps over the Earth
If the mass of the remaining core after the supernova has a mass of 3 solar masses or more the star may collapse to the point where all forces are overcome, this is called a.... black hole
Main Sequence: _ fuses to __ in core H, He
Red Giant: _ fuses to __ in shell around __ core H, He
Helium Core Burning: __ fuses to _ in core while _ fuses to __ in shell He, C, H, He
Double Shell Burning: _ and __ both fuse in shells H, He
Planetary Nebula leaves ____ ____ behind white dwarf
Reasons for Life Stages: Core shrinks and heats until it’s... hot enough for fusion
Reasons for Life Stages: Nuclei with larger charge require... higher temperature for fusion
Reasons for Life Stages: Core thermostat is broken while core is not hot enough for.... fusion (shell burning)
Reasons for Life Stages: Core fusion can’t happen if.... degeneracy pressure keeps core from shrinking
Multiple Shell Burning: Many elements... fuse in shells
Supernova leaves ____ ____ behind neutron star
______ believed all objects fall at the same speed unless air resistance or some other force acts upon them Galileo
If a person falls freely he will not feel his... own weight
gravity can be cancelled out by... acceleration
a property of the space in the presence of an object with mass is called the... the gravitational field
gravity is equivalent to... acceleration
The greater the mass, the... greater the distortion of spacetime.
"matter tells space how to curve. space tells matter how to move." is a quote by... John Archibald Wheeler
Einstein’s theory of General Relativity says that... space-time is curved by the presence of a mass
a mass in space causes a curvature in space fabric. the curvature then... explains the the movement of the matter
an object will travel on as.... straight a path as possible through space time
The curvature of the spacetime continuum is produced by... the presence of mass
Massive object ____ spacetime continuum more distorts
Newton’s law predicted that the... orbit of Mercury should change
The more spacetime curves, the stronger the... gravity
light will always travel at a.... constant velocity.
Created by: user-2009548
 

 



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