Exam 2 Flashcards
The hottest zone in the sun is the
core
The most common element in the sun is
hydrogen
T OR F: The sun rotates at different rates at different latitudes on the sun
True
The innermost part of the sun is the
core
a region of the sun where energy is transported very slowly because the matter is densely packed; this is called the ___________.
radiative zone
a region of the sun where vast bubbles of hot material move upward and then sink down, much like bubbling oatmeal or miso soup, called the ______________.
convective zone
The layer where the Sun becomes opaque and we can not see further in is called its _________
photosphere
Further outward is a region of thinner, hot gas, called the __________
chromosphere
The Sun’s outermost layer, the _____, has very low density and extends for millions of miles
corona
During a solar maximum, what phenomena should you expect to see enhanced compared to the average levels?
number of solar flares
number of sunspots
aurora on Earth
Which of the following types of star is the coolest (has the lowest surface temperature)?
M
T OR F: The amount by which the spectral lines of a star is redshifted tells astronomers how fast the star is moving away from us
True
Astronomers use the term interstellar matter to refer to:
gas and dust that lies between stars
The red color we see on a lot of photographs of nebulae comes from which element?
hydrogen
A type of star cluster that contains mostly very old stars is
a globular star cluster
Why can a star with a mass like our Sun not fuse (produce) further elements beyond carbon and oxygen?
because such a star just cannot get hot enough for the fusion of heavier nuclei
When a single star with a mass equal to the Sun dies, it will become a
white dwarf
If you want to find stars that are just being born, where are the best places to search?
in giant molecular clouds
A star whose temperature is increasing but whose luminosity is roughly constant moves in what direction on the H-R diagram?
to the left
Astronomers identify the “birth” of a real star (as opposed to the activities of a protostar) with what activity in the star?
when nuclear fusion reactions begin inside its core
Everything we know about
stars comes from their light, and
they don’t all appear equally
bright, nor the same color; they
differ in:
Temperature
* Mass
* Energy emission
* Composition
* Etc.
total amount of energy at all wavelengths that a star emits per
second.
luminosity
the amount of a star’s energy that reaches a given area each second here on Earth
apparent brightness
For two stars of the same apparent brightness, the star closer to the Sun will generally have
a lower luminosity
formula for apparent brightness
luminosity / distance^2
brightest stars are what magnitude
1
faintest stars are what magnitude
6
Which of the following quantities do you need in order to calculate a star’s luminosity?
distance and apparent brightness
There are seven general categories of stellar spectra, corresponding to different temperatures. From hottest to coolest, those categories are
O B A F G K M
(Oh Be A Funny Goat, Kick Me)
The more massive stars are generally also the more
luminous
A binary star system:
A. Is composed by two stars
B. Is held together by gravity
C. Is useful to find the mass of the component stars
D. Is not always visually detectable
E. All of the above
E. All of the Above
where most stars are
the main sequence
What are the two most important intrinsic properties for classifying stars?
luminosity and surface temperature
Apparent motion of object against distant background from two vantage points.
parallax
A graph that shows how the brightness of a variable star changes with time is
called a
light curve
The interstellar medium consists of
gas and dust
region of space that is clearly distinguishable through a telescope
(dark or bright) , but is not sharply defined like a planet or a star
nebula
glowing cloud of hot interstellar medium
emission nebula
Study of the stars and galaxies through hydrogen signals
radio astronomy
The reddish color of emission nebulae indicates that:
hydrogen gas is present
If an interstellar cloud contracts to become a star, it is due to which force?
Gravitational
Objects more massive than the Sun form into stars
Much faster, over tens of thousands of years
spherical cluster of stars with the
absence of massive main-sequence stars, and the heavily
populated red giant region. Found away from the galactic
plane
globular cluster
What is a T-Tauri star?
A protostar about to become a star
Once a star has reached the main sequence stage of its life, it derives its
energy almost entirely from
the conversion of hydrogen to helium
Helium begins to fuse extremely rapidly; within hours the enormous energy output is over, and the star once again reaches equilibrium
helium flash
During formation, the Sun evolved toward the main sequence as shown in the
figure. The Sun will evolve away from the main sequence when
(a) Its core begins fusing iron.
(b) Its supply of hydrogen is used up.
(c) The carbon core detonates, and it explodes as a Type I
supernova.
(d) Helium builds up in the core, while the hydrogen-burning
shell expands.
(e) The core loses all of its neutrinos, so all fusion ceases.
(d) Helium builds up in the core, while the hydrogen-burning
shell expands.
What determines the outcome
(bang or whimper) is
the mass of the star when it is ready to die, not the mass it was born with.
do black dwarfs exist?
No
Stars like our Sun will end their lives as
white dwarfs
a one-time violent explosion – once it happens, there is little or nothing left of the progenitor star.
supernova
Star that flares up very suddenly and then returns slowly to its former luminosity
novae
A white dwarf can explode when
Its mass exceeds the Chandrasekhar limit.
star formation is
cyclical
