ASTR 101 Midterm #2 SDSU - Leonard

Electron

Negatively charged particle found OUTSIDE the nucleus.

(slide 131)

Proton

Positively charged particle found INSIDE the nucleus.

(slide 131)

Neutron

Neutral particle found INSIDE the nucleus.

(slide 131)

massive

The neutron is slightly more ____ than the proton, and both are much more ____ than the electron.

(slide 131)

Element

A kind of atom, characterized by the number of protons in the nucleus.

(slide 133)

Atom

The smallest particle of an element that retains the properties that characterize that element.

(slide 133)

Periodic Table of Elements

A system of organization for the elements. Elements are placed based on their atomic number and type. The number of PROTONS determines the type of element an atom is.

(slide 134)

Atomic Notation

a way of representing a element by showing it's mass number and atomic number.

Mass number (top number): number of protons + neutrons

Atomic number (bottom number): number of protons

(**see slide 136)

Ion

An atom that has lost (or gained) one or more ELECTRONS

(slide 134)

Isotope

Any of two or more forms of the same element whose atoms all have the same number of protons but different numbers of neutrons.

(slide 134)

Apparent Brightness

How bright an object appears in the sky. A measure of the observed light received from a star or other object at the Earth.

(slide 137)

Depends on the luminosity and distance of an object

(slide 191)

Luminosity

The total amount of light emitted by an object each second (unit: Watts).

(slide 137)

Depends on the temperature and size (i.e. surface area) of an object.

(slide 191)

Inverse Square Law of Light Propagation

2x distance = 1/4 amount of light

(slide 137)

Standard Candle (bulb)

an object of known luminosity. By measuring apparent brightness of a ____________ you can determine its distance

(slide 137)

Speed of Light

300,000 km/s or about 186,000 miles/s

(slide 138)

Reflection

The return of light after striking a surface.

(slide 138)

Refraction

The bending of light when it passes from one transparent medium to another. Different colors of light ____ by different amounts.

(slide 138)

Dispersion

The act of separating the different colors of light through being refracted by different amounts.

(slide 140)

Spectrum

The array of colors obtained when light is dispersed

(slide 140)

Spectroscopy

The study of spectra

(slide 140)

Continuous Spectrum

A spectrum of light composed of radiation of a continuous range of wavelengths or colors rather than only certain discrete wavelengths.

Discovered in 1666 by Newton. Produced by heating a solid object (coal) or very dense gas until it glows.

(slide 141 - 143)

ROYGBIV

An acronym for the spectrum of light: Red, Orange, Yellow, Green, Blue, Indigo, Violet

Bright Line Spectrum (aka emission-line spectrum)

A pattern of ____ lines produced by a rarified (low density) gas whose atoms have been "excited." Discovered in 1855 by Kirchoff; produced by passing an electrical current, or otherwise 'excite' a rarified gas (gas discharge tubes)

(slide 143 -144)

Rarified

Having low density

(slide 144)

Dark Line Spectrum (aka absorption-line spectrum)

A pattern of ____ lines superposed on an otherwise continuous spectrum. Produced by passing a continuous spectrum through a very rarified (not dense) gas (Sunlight)

(slide 143 and 145)

Kirchoff's 3 laws of spectral analysis

1) a luminous solid, liquid, or hot, dense gas emits light of all colors producing a continuous spectrum

2) a rarified (low density) luminous gas emits light of certain colors only, producing an emission-line spectrum

3) If a continuous spectrum is passed through a rarified gas, the gas will absorb certain, specific, colors, so that those colors will then be missing (or diminished) in the otherwise continuous spectrum. This produce an absorption-line spectrum

(slide 147)

Particles

energy localized in a packet

(slide 152)

Wave

energy spread out being transported through a medium

(slide 152-153)

Medium

The substance through which a wave is traveling.

(slide 153)

Frequency

Number of complete wave cycles that pass a point each second. Measured in waves (or cycles) per second. Unit: Hertz (Hz)

(slide 154)

Wavelength

Distance between two identical points on successive waves. Different ____ refer to different colors.

(slide 154)

Electromagnetic radiation

Radiation consisting of waves propagated through regularly varying electric and magnetic fields.

(slide 156)

Electromagnetic Spectrum

The whole range of electromagnetic waves, from gamma rays (short wavelengths) to radio waves (long wavelength).

Gamma, X, ultraviolet (UV), visible, infrared (IR), radio

(slide 156)

Electromagnetic Waves

A form of energy that can move through the vacuum of space.

H-alpha line

The most prominent spectral feature due to hydrogen at visible wavelengths (wavelength = 6563 angstroms)

(slide 161-162)

Doppler effect

a change in wavelength/frequency due to relative motion of wave source and/or detector. Observer sees decreased wavelength (higher frequency) for approaching source, and increased wavelength (lower frequency) for receding source.

(slide 166)

Blueshift

A shift to shorter wavelengths (source is approaching)

(slide 166)

Redshift

A shift to longer wavelengths (source is receding)

(slide 166)

Radial velocity

Motion towards or away from an observer.

The greater blue- (red-) shift, the greater radial velocity of the object.

(slide 168)

Extrasolar planet ("exoplanet")

A planet orbiting a star other than the sun. Over 400 have been found and nearly all of these were discovered by observing the Doppler shifts

(slide 170)

Proper motion

Motion of a celestial object across the sky.

(slide 172)

Photon

An individual particle of light, a packet of energy. Amount of energy contained in a ____ is determined by its color, which is set by its frequency or wavelength.

(slide 174-175)

Quantum mechanics

The branch of physics that deals with the structure of atoms and their interactions with light.

(slide 178)

Quantize

to limit the possible values of

(slide 179)

Emit

According to quantum mechanics, for an electron to jump from a higher orbit to a lower one, it must ____ a photon.

(slide 179)

Absorb

According to quantum mechanics, for an electron to jump from a lower orbit to a higher one, it must ____ a photon.

(slide 179)

Ionization energy

The minimum amount of energy required to remove an electron from an atom in its ground state.

(slide 183)

Color

The ____ of a star tells us its surface temperature. The absorption lines tell us which elements are in its outer atmosphere.

(slide 189)

Sunspot

A region of the Sun's surface that is cooler, and thus darker, than the surrounding regions.

(slide 190)

Photosphere

The visible "surface" of a star (e.g., the Sun) The region in a star's atmosphere from which visible light escapes into space.

(slide 190)

Blackbody radiation

The spectrum radiated by a "perfect" absorber and emitter of radiation.

Color of a _____ depends ONLY on temperature; it does not depend on the object's size or distance.

(slide 191)

Conservation of Energy

Energy can not be created or destroyed, it can only be transformed from one type to another

(slide 198)

E=mc^2

Einstein's equation proposing that energy has mass; E is energy, m is mass, and c is the speed of light

(slide 200)

Strong force

A very short-range but powerful force that binds nucleons (protons and neutrons) together

(slide 201)

Thermonuclear reaction

a nuclear reaction that results from encounters between particles that are given high velocities by heating them

(slide 201)

Fundamental Forces of Nature

The basic forces that are known to exist in Nature

-gravity

-electricity

-magnetism

-strong nuclear force

(slide 202)

Antimatter

A type of matter in which each particle is opposite in charge, and certain other properties, to a corresponding particle of the same mass.

(slide 206)

Neutrino (v)

undercharged elementary particles with very little mass that rarely interact with other particles

(slide 207)

Neutrino oscillations

the transformation of one neutrino type into another

(slide 210)

Gas pressure

the pressure resulting from the thermal motions of gas particles

(slide 213)

Radiation pressure

The pressure resulting from the impact of photons on a surface of gas

(slide 213)

Hydrostatic equilibrium

A state of equilibrium in which the inward pull of gravity in a star is just balanced by the outward forces of gas and radiation pressure.

(slide 214)

Nucleosynthesis

The building up of heavier elements from lighter ones by nuclear fusion

(slide 215)

Nuclear fusion

The building up of heavier atomic nuclei from lighter ones

Elements "lighter" than Fe release energy through _________

(slide 216)

Nuclear fission

The break up of heavier atomic nuclei into two or more lighter ones

Elements "heavier" than Fe release energy through _________

(slide 216)

Interstellar Matter

Gas and dust between the stars

(slide 220)

Interstellar gas

consists primarily of hydrogen; presence is inferred by light it EMITS (emission-line spectrum)

(slide 220-221)

Interstellar dust

consists of tiny solid grains in interstellar space. presence inferred (mainly) by light it ABSORBS. Dust blocks light coming from behind it.

(slide 220-221)

Main-sequence star

a MAJORITY of a star's life is spent as a ______________: A star that is fusing hydrogen (H) into helium (He) in its core

(slide 222)

Stellar evolution

The changes in a star's properties as it ages

(slide 222)

Red giant star

a large, cool star of a high luminosity in its late stages of life.

(slide 225)

Low mass star

Those stars that are born with less than 8 times the mass of the sun. The core temperature is not high enough to fuse heavier elements

(slide 227-228)

High mass star

Those stars that are born with greater than 8 times the mass of the sun. Iron (26 protons in nucleus) is produced. Fusion of heavier elements requires energy - it does not release energy

(slide 227-228)

Mass loss

The loss of material during the life of a star

(slide 230)

Planetary nebula

A shell of gas ejected by and expanding away from an extremely hot low-mass star that is nearing the end of its life

(slide 231)

Binary star

Two stars that orbit each other, bound together by gravity

(slide 236)

Center of mass

For binary star system: the point between the two stars about which they both orbit

(slide 237)

White dwarf

The final stage of evolution for a low-mass star, in which it is collapsed to a very small size

(slide 240)

Fate of low-mass star

(slide 250)

Electron degeneracy pressure

A force arising from the laws of quantum mechanics through which closely packed electrons strongly resist further compression

(slide 241)

Chandrasekhar limit

the theoretical upper limit to the mass that a which dwarf can have, of 1.4 mass of sun

(slide 241)

Neutron star

A star of extremely high density composed almost entirely of neutrons.

(slide 245)

Supernova

The explosion of a star, with the resulting release of a tremendous amount of light

(slide 246)

Fate of high-mass star

(slide 250)

SN 1987A

the closest supernova (only 160,000 LY away) of the last 400 years

Confirmed that our basic understanding of the core-collapsed supernova phenomenon is correct

(slide 256)

Core-collapse (type II) supernova

Results from the core collapse and subsequent envelope ejection of massive stars, produces a tremendous optical display

Producing a luminosity of up to 10 billion times the luminosity of the Sun

Leaves behind a very compact objects, the dense corpse of the core of the once-massive star. This object is thought to be either a neutron star or a black hole.

(slide 251)

Neutron degeneracy pressure

a force arising from the laws of quantum mechanics through which closely packed neutrons very strongly resist further compression.

(slide 252)

Black hole

a completely gravitationally collapsed object; a region of space from which neither matter nor light can escape. Thought to be produced by stars with initial mass > Msun

(slide 252)

Neutron bombardment

____ ____ of iron (and other) nuclei at early times in the expanding "ejecta" (ejected stellar material) of supernovae.

(slide 258)

Pulsar

A rotating neutron star emitting pulses of radio waves

(slide 261)

Mass transfer

The transfer of material from one object to another

(slide 267)

Accretion disk

disk of matter spiraling in toward the compact object

(slide 267)

Thermonuclear (Type Ia) supernova

complete destruction of white dwarf due to a thermonuclear runaway initiated at the center of the star

(slide 273)

Nova

A star that experiences a sudden outburst of radiant energy, temporarily increasing its luminosity by hundreds to thousands of times.

(slide 273)