measure of an object's luminosity/

the apparent magnitude the object would have if it were located 10 parsecs away

fast rotating disk of material that gradually falls inward as it orbits a star like object

(such as a white dwarf, neutron star, or black hole)

amount of light reaching us per unit area from a luminous object 

measured in watts/meters squared

when all He is used up in the core of a star, it contracts again, leading to heating up & causing He fusion to occur in a shell above the core

also known as He Core Exhaustion

bottomless pit in spacetime

nothing can escape from within

it is impossible to detect or observe an object that falls into one 

object too small to become an ordinary star

because electron degeneracy pressure stops its gravitational collapse before fusion becomes self-sustaining 

layer of the Sun's atmosphere below corona

most of the Sun's ultraviolet light is emitted from this region- temperature about 10,000 K

outer layer of the Sun/ region of a star in which energy is transported outward by convection

(where the energy is transported by cells of hot rising gas)

convective energy transport

convective contraction on a life track?

protostar's surface temperature about 3000K

convection remains the dominant mechanism for energy transport & gravitational contraction decreases the protostar's luminosity because radius gets smaller as temperature stays constant- protostars life track drops down

Fe nuclei break into protons, neutrons, electrons

neutrons are formed and neutrinos are released

thermal pressure drops and core collapses until stopped by neutron degeneracy pressure

then becomes a neutron star, this only takes seconds, upper layers rebound then fly into space

tenuous uppermost layer of the Sun's atmosphere

most of the Sun's X Rays are emitted from this region where temperature is about 1 mil K

form of hydrogen where nucleus contains a proton and neutron- rather than only 1 proton

binary star system in which two stars orbit the plane of our line of sight 

each star periodically eclipses the other

boundary that marks the "point of no return" between a black hole and the outside universe

events that occur within the event horizon can have no influence on our observable universe

sudden burst of gamma rays from deep space

coming from distant galaxies, but their precise mechanism is unknown

spherically shaped cluster of up to 1 mil stars, found primarily in the halos of galaxies

and contain only very old stars

graph plotting individual stars as points

stellar luminosity on the vertical axis and

spectral type (surface temp) on the horizontal

(in a high mass star) 

CNO Cycle?

states that an object's apparent brightness depends on its actual luminosity and the inverse square of its distance from the observer

apparent brightness= 

luminosity over

4π X (distance)²

total power output of an object, usually measured in watts or L_Sun (units of solar luminosities)

L_Sun= 3.8 X 10²⁶ watts

category describing a region of the H-R diagram in which a star falls

I represents supergiants, III represents giants and V represents main sequence stars

II and IV are intermediate to the others

point on a star's H-R diagram where its stars turn off from the main sequence, 

the age of the cluster is equal to the main sequence lifetime of stars at the main sequence turnoff point

fundamental particle that has extremely low mass and responds only to weak force

leptons that come in three types:

electron neutrinos, mu neutrinos, tau neutrinos

degeneracy pressure exerted by neutrons

as in neutron stars

dramatic heightening of a star lasting for a few weeks & then subsiding

occurs when a burst of hydrogen fusion ignites in a shell on the surface of an accreting white dwarf in a binary system

up to several thousand stars 

found only in the disks of galaxies and often contain young stars

(pc) the distance to an object with a parallax angle of 1 arcsecond

approx equal to 3.26 light years

Roche lobe 

(binary system)

short lived phenomena on the Sun

including the emergence and disappearance of individual sunspots, prominences, and flares

sometimes called Solar weather

way of classifying a star by the lines appearing on its spectrum- related to surface temperature

basic spectral types designated by OBAFGKM

O for the hottest stars and M for the coolest

all letters are subdivided by numbers 0 to 9