Astro3

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Bok Gobules

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dark nebulae with well defined reigons

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Corona

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*layer above the Chromosphere
*observed during solar eclipses
*radiates strongest in x-rays

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Protostars

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collapsing cloud of gas and dust which will eventually become a star

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Chromosphere

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*layer above the photosphere
*radiates in Hydrogen Balmer lines (emmision spectrum)

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HH Objects

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*formed when the gas and dust in a protostar forms a disk, jets of energy are emitted, and these jets excite ISM
*evidence that stars are forming

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Solar Wind

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*gas that follows magnetic filed lines
*when the magnetic field lines break apart,the gas streams out in a solar wind
*coronal holes are the source

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Interstellar Reddening

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the process in which dust scatters blue light out of starlight and makes stars look redder

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Photosphere

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*layer closest to the sun
*low density
*where sunspots are observed

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Brown Dawrf

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star whose mass is too low to ignite nuclear fusion and is heated by contraction

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Roche Lobe

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volume within a Roche surface which is gravatationally associated with one of hte stars

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T-Tauri Stars

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not yet main sequence stars, located near birthline

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Event Horizon

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the boundary of a black hole from which no radiation may escape

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Emission Nebulae

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ionized by nearby hot stars and emit an emission spectrum

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Mass Transfer

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when the mass from one star in a binary system transfers its mass to the other star

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Apparent Visual Magnitude

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the visual magnitude of a star as it appears from Earth

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Accretion Disks

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whirling disk of gas that forms around a compact object such as a white dawrf, neurton star, or black hole as matter is drawn in

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Nuclear Fusion

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lighter nuceli combine to create heavier nuceli, releasing energy in the process

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Novae

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material blown off by a star that is the companion of a white dawrf

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Zeeman Effect

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*splitting of emission lines of sunspots due to presence of a magnetic field
*magnetic field prohibits rising gas from delivering heat to the surface

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X-Ray Bursters

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an object that produces repeated bursts of xrays

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Differential Rotation

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when different parts of a body have different periods of rotation

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Triple Alpha Process

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3 He nuceli=1 Carbon nucleus

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Proton-Proton Chain

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set of three reactions which convert 4 Hydrogen nuceli into one He nucleus

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Pulsars

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beams of light given off

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Absolute Visual Magnitude

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*brightness of a star if it is 10pc or closer
*if we know the distance to a star and the apparent magnitude, the actual magnitude can be determined
*STAYS THE SAME NO MATTER WHAT DISTANCE

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Roche surface

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defines a reigon in which matter will be gravatationally bound to one star or hte other

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Stellar Masses

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center of mass and orbital period velocity tell us the mass

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Degenerate Matter

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*gas so dense electrons aren't free to change their energy
*matter almost solid but wont compress like a solid

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Spectral Line Broadening

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*main sequence stars because they are smaller than other stars, cause a broadening of spectral lines
**THE SMALLER THE OBJECT THE BROADER THE LINES

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Planetary Nebulae

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expanded shell of gas ejected from a star during hte latter stages of its evolution

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Visual Binary Systems

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*two stars whose orbits can be mapped out
*line between the stars always passes the same center of mass

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Schwartschild Radius

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the distances that defines the event horizon

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Solar Flares

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*when the magnetic filed lines become too twisted, they cancel each other out and reconnect
*stored energy is released as photons and charged particles

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Supernova Reminants

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shall moves outward and interacts with ISM

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Apparent Brightness

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*measures the lumonsity of a star
*how bright a star looks as seen by the human eye
*changes with distance

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Giant Star Evolution

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Star expands, temperature decreases, lumonsity increases

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Reflection Nebulae

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clouds that scatter light from nearby cooler stars

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Radiation

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absorbtion and reemission of photons

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Cause of Sunspots

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magnetic filed are dragged around the sun and where they tangle, sunspots occur

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Supernova Explosions

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*iron forms in the core and reactions stop
*core collapeses
*core increases in temp
*all layers collape

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Stellar Radii

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can be found if we know lumonsity and temperature of a star

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Hydrogen Shell Fusion

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H2 in the core heats up, fusion takes place, uses up H2
(EXPANDS SHELL OF CORE)

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Distance Modulus

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*the difference between the apparent and absolute magnitude of a star
*a measure of how far it is away

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CNO Cycle

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series of reactions involving C2, N2, O2, and 4H2 nuceli comebind to create one He nucleus

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Hydrogen Fusion

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*at high enough temperature and pressure, 4 Hydrogen protons can fuse into a He nucleus and mass converts to energy

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Red Dwarf

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*little gravity, dont need many nuclear reactions to balance it
*never evolve into a giant becuase temperature wont get high enough

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Spectroscopic Parallax

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the meathod of determing a stars distance by comparing its apparent magnitude with its absolute magnitude as estimated from its spectrum

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Black Dawrf

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*Carbon and Oxygen
*what is left after heat is radiated away

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Prominences

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hot ionized gas trapped in magnetic field lines

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Helium Flash

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explosive ignition of He fusion in the core of Giant Stars

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Inverse Square Law of Light

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if one light is twice as far away as the other, it will appear 1/4th as bright

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Neutron Stars

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*supernova protons combine with electons and create neutrons
*gravity is halted by neutron pressure

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Granulation

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*the rising of hot fluid and sinking of cool fluids (convection)

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Helium Core Fusion

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core continues to shrink, core heats up so He can fuse

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Sunspots

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*cooler, dark reigons on the Sun
*can last up to 2 months
*dark spot-umbra
*lighter spot surrounding-penumbra
*position and number change over time
*22 yrs=full cycle, polarity flips every 11 yrs

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White Dawrf

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*hot, small objects
*dense
*what is left after outter layers blow off
*no more fusion can occur

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Dark Nebulae

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clouds that block background light

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Intrinsic Brightness

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measure of the total amound of light a star emits

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Absolute Lumonsity

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*the amound of energy a star gives off in every direction
*if we know the apparent brightness of a star and the distance, we can determine the lumonsity

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Parallax

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*measures distance of a star
*only the parallax of the closest stars can be measured

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Spectroscopic Binary Systems

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*as the stars circle their orbits, the spectral lines move together
*spectral lines shift and then merge

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Flux

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a measure of the flow of energy out of a surface