Physics exam #3

color of spectral class

(O)blue, (B)blue-white, (A)white, (F)white, (G)yellow-white, (k) yellow-orange, (M) Orange Red

Roughly, what is the range of diameters (in multiples of our Sun's diameter) of stars?

.6 to 20

Roughly, what is the range of mass values (in solar masses) of stars?

1/12 to 100

arc second

1/60th of an arc minute 1/3600 of an arc degree

B0 to b9 ( sub classes)

B0 being hotter and B9 being cooler

Modified Kepler's 3rd Law

d^3/p^2 equals sum of the mass of a star( proves mass of star)

relative velocity

describes the velocity of an object with respect to a frame of reference

what is the main reason that the spectra of all stars are not identical

different surface temperatures

what two factors determine how bright a star appears in the sky

distance and luminosity

how to measure diameter of star

eclipsing binary stars and on the hr diagram (luminosity, temperture)

giants

has a large extended photo sphere that has atoms spread out creating a greater volume which means that the density is low.

binary star systems

have two stars

white dwarfs

high temp blueish white star with low luminosity( cant see with naked eye)

doppler effect can also measure

how fast a star rotates

metals are considered anything heavier than.... on a star

hydrogen(3/4 of sun) and helium(24.8 of sun) which are the main elements of the sun

2 AU

is the distance from one end of the orbit around the sun to the opposite end

if a star is moving towards you

its a blue shift

If a star is moving away from you...

its a red shift

aurora

light radiated by atoms and ions in the ionosphere excited by charged particles from the Sun, mostly seen in the magnetic polar regions

Roughly, what is the range of star luminosities (in multiples of our Sun's luminosity)?

10-4 to 106

The most recently discovered system close to Earth is a pair of brown dwarfs known as Luhman 16. It has a distance of 6.5 light-years. How many parsecs (pc) is this?

2 pc

Roughly, what is the range of star surface temperatures (in kelvins)?

3000 to 40,000 (M(cooler) to O(hottest))

The Sun converts 4x109 kg of mass to energy every second. How many years would it take the Sun to convert a mass equal to the mass of Earth [= 5.974x1024 kg] to energy?

47 million years

3.26 light/ 1 parsec

= 1 light year/ .31 parsec

sunspot

A dark area of gas on the sun's surface that is cooler than surrounding gases.

nuclear fission

A nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy

radiation zone

A region of very tightly packed gas in the sun's interior where energy is transferred mainly in the form of light. Endlessly reflecting light

Cepheid variable

A star whose brightness varies periodically because it expands and contracts; a type of pulsating star that is useful to astronomers for measuring distances in the universe

spectral class

A star's label in the temperature classification system based on the appearance of the star's spectrum

solar wind

A stream of electrically charged particles produced by the sun's corona

Parsec

A unit of distance that is equal to 3.26 light years

pulsating variable star

A variable star that goes through periods of swelling and brightening, then shrinking and dimming and experiences a change in magnitude during that cycle. when star gets bigger gas gets cool and when it contracts again the gases heat up

red dwarf

A very small star with low temperature, reddish in color.

Parallax

An apparent shift in the position of an object when viewed from different locations

parsec equation

D=1/p

Binary star equation

D^3=(m1+m2)p^2

Our Sun is a star of spectral type _________.

G2( average main sequence)

H-R diagram

Hertzsprung-Russell diagram, a graph that shows the relationship between a star's surface temperature and absolute magnitude

mnemonic for OBAFGKM (spectral class sequence)

Oh Be A Fine girl, Kill me( hot to cool)

Color Index

Simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. The smaller the color index, the more blue (or hotter) the object is.

What are the luminosity class and spectral type of a star with an effective temperature of 5000 K and a luminosity of 100 LSun?

Spectral type G, luminosity class III

variable stars

Stars whose brightness appears to fluctuate

Doppler effect

The change in frequency of a wave as its source moves in relation to an observer. Great for measuring velocity of stars.

absolute velocity

compares plate movement to a fixed position

inverse square law

The formula relating brightness, luminosity, and distance is called

suns core

The inner most layer of the Sun where nuclear fusion, converting Hydrogen into Helium, takes place.

OBAFGKM sequence

The sequence of stellar spectral classifications from hottest to coolest stars.

Spectroscopy

The study of the properties of light that depend on wavelength.

baseline

The two observation stations distance from each other.

brown dwarf

Too small to have nuclear fusion and be called a star, yet considered too big to be called a planet. very difficult to observe because they are extremely faint and cool and they put out most of their light in the infrared. They do not partake in the hydrogen fusion.

main sequence

a diagonal area on an H-R diagram that includes more than 90 percent of all stars. Its on a graph that is between temperature and luminosity

how do we measure the velocity of stars

a doppler shift (away=red shift)(towards= blue shift)( cannot measure via sideways shift)

proton-proton chain

a fusion process in which protons build together to form helium

light curve

a graph that shows how the brightness of a variable star changes

nuclear fusion

a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy.

positron

a particle with the mass of an electron but a positive charge. aka an anti electron

Cepheid variable stars

a particularly luminous type of pulsating variable star that follows a period-luminosity relation and hence is very useful for measuring cosmic distances

center of mass

a point representing the mean position of the matter in a body or system.

coronal hole

a region in the Sun's outer atmosphere that appears darker because there is less hot gas there

neutrino

an elementary particle with zero charge and zero mass that moved at with the speed of light

magnitude system

ancient scale that measures stars brightness from 1(brightest) to 6( demist)

What would be the advantage of making parallax measurements from Pluto rather than from Earth?

bigger baseline

Of the following star properties, which one requires knowing the distance in order to be directly determined?

luminosity

power rating of energy and can be measured in watts.

luminosity

Which of the following stars would be least luminous based on the spectral data?

m main sequece

stars on main sequence vary with

mass

more mass in stars means

more luminous

radial velocity

motion toward or away from the observer; the component of relative velocity that lies in the line of sight

what is the ultimate source of energy that makes the sun shine

nuclear fusion

eclipsing binary

one star periodically blocks the light from the other.

Perihelion

orbital point nearest the sun

Suppose you have discovered a new cepheid variable star. To determine its distance, you will need to measure its apparent brightness and its

period of pulsation

order of cooler to hotter structure of sun

photosphere, chromosphere, transition region, corona

Aphelion

point in a planet's orbit that is farthest from the sun

wiens laws

proves temperature of the star(T = (3 x 10^6 K nm) / lmax)

parallax

shows the distance to the star (1/parallax angle)

Star A and Star B have different apparent brightnesses but identical luminosities. If Star A is 20 light-years away from Earth and Star B is 40 light-years away from Earth, which star appears brighter and by what factor?

star (A) times brighter

on right side of main sequence

stars are larger and cooler than the sun

on left side of main sequence

stars are smaller and hotter than the sun

white dwarfs and red dwarfs emit so little light

that they can not be seen with the naked eye

stellar parallax

the apparent shift in the position of a nearby star (relative to distant objects) that occurs as we view the star from different positions in Earth's orbit of the Sun each year

magnitude

the brightness of a star

apparent brightness

the brightness of a star as seen from Earth

the brightest stars are not necessarily

the closest

space velocity

the combo of a stars proper motion and radial velocity

corona

the hottest region of the sun's atmosphere

super giants

the most luminous, most massive stars, with diameters greater than 100 times the diameter of the sun.

mass-luminosity relation

the observed relation between the masses and luminosities of many (90% of all) stars

chromosphere

the region in the Sun's atmosphere located between the photosphere and the corona

transition region

the region in the Sun's atmosphere where the temperature rises very rapidly from the relatively low temperatures that characterize the chromosphere to the high temperatures of the corona

proper motion

the transverse of radial motion. Its the relative change in positions of the stars on the celestial sphere.

photosphere

the visible surface of the sun. The inner layer of the sun

luminosity

total amount of energy at all wavelengths that it emits per second.

hydro elastic equilibrium

when it is at rest, or when the flow velocity at each point is constant over time. This occurs when external forces such as gravity are balanced by a pressure-gradient force.

fusion

when light nuclei are merged to become heavier nuclei

fission

when nuclei of heavy elements explosively break apart

convection zone

where hot gas moves up toward the surface and cooler gas moves deeper into the interior. outer most layer of the sun

A star has a temperature of 10,000 K and a luminosity of 10-2 LSun, what kind of star is it?

white dwarf

To know space velocity

you must know radial velocity, proper motion, and distance

RR Lyrae variables

• Low-mass stars on the horizontal branch. • Less luminous than Cepheid variables.