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Stars

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Granulation is the most direct evidence of solar convection.
True
The solar corona is much cooler than the sun's photosphere, hence we must wait for a total solar eclipse to glimpse it.
False
Sunspots usually come in pairs, each with a magnetic pole.
True
The solar wind is constantly removing mass from the Sun.
True
A type B star is bluer than a type G star.
True
The Sun is part of a binary system.
False
The Solar Neutrino Problem is that we observe more neutrinos than predicted.
False
A +6.0 magnitude star is brighter than a +3.0 magnitude star.
False
Our Sun will eventually become a nova.
False
A massive star will fuse heavy elements only up to iron before collapsing.
True
The outward pressure of hot gas in the Sun is
balanced by the inward gravitational pressure
Sunspots are dark splotches on the Sun
That are extremely hot, but cooler than the surrounding areas of the Sun.
What information can be gained from the light curves of eclipsing binaries?
Their masses.
A solar mass star will evolve off the main sequence when
it builds up a core of inert helium.
Of the elements in your body, the only one not formed in stars is
Hydrogen
A white dwarf has the mass of the Sun and the volume of
Earth
An iron core cannot support a giant star because
iron cannot fuse with other elements and produce additional energy in fusion.
The heaviest nuclei of all are formed
during nova explosions.
In a neutron star, the core is
made of compressed neutrons in contact with each other.
What is always true of two stars that have the same absolute magnitude
They have the same luminosity.
Stars in different stages of their evolution may generate energy using different nuclear reactions. These reactions can occur in the core or in a layer around the core. At the present, the energy of the Sun is generated
in its central core by fusion of hydrogen nuclei.
The energy produced in the central core of the Sun is transported to the surface
by radiation in the layers just outside the central core and by convection in the outer layers.
What can be said with certainty about a red star and a blue star?
The blue star is hotter than the red star.
The 11 year solar cycle refers to
the rate of occupance of magnetic storms on the surface of the sun
Two important characteristics of sunspots are
low temperature, intense magnetic fields.
Which region of the sun has the highest temperature?
corona.
The luminosity of a star is
the total energy emitted at all wavelengths into all space, from its whole surface
The most abundant element on the sun is
Hydrogen
If the sun were twice as far away as it is now, we would receive
one-fourth as much flux
If two stars have the same size but different temperatures, then the hotter star will be
bluer and brighter
Which of the following observed quantities depends upon the distance to the object
apparent brightness
Which of the following represents the approximate range of stellar masses?
0.05 to 50 solar masses
The region of the H-R diagram occupied by most stars is the
main sequence region
To construct an H-R diagram, astronomers plot random stars by their
actual brightness and spectral type
We know that giant stars are larger in diameter than the sun because
they are cooler but have the same luminosity.
Main sequence stars are the most common type of star because
stars spend most of their lives there
Which of the stars has the coolest surface temperature
a red giant
A star ten times the mass of the sun will have a main sequence lifetime, compared to the sun's, that is
shorter
Which of the following quantities
do you need in order to calculate a
star's luminosity?
apparent brightness (flux), and distance to the star
The absolute magnitude of a star is its brightness as seen from a distance of
ten parsecs
A star's apparent magnitude is a
number used to describe how our
eyes measure its
brightness.
In the stellar magnitude system invented by Hipparchus, a smaller magnitude
indicates a _____ star.
brighter
How bright is a star with a magnitude of +4.0 compared to
a star with magnitude +5.0?
2.5 times brighter
The process of measuring the apparent brightnesses
of objects is called
Photometry
Two ways to express apparent brightness:
Stellar Magnitudes, and Absolute Fluxes
Apparent Brightness:
Measures how bright the star appears to be as seen from a distance.
Intrinsic Luminosity:
Measures the Total Energy Output by the star in Watts
A star's proper motion is its
annual apparent motion across the sky.
Parallax measurements are best made using a telescope in orbit. This is because
an observatory in space is unhampered by the Earth's atmosphere.
The angle of stellar parallax for a star gets larger as the
length of the baseline increases.
Stellar parallax is used to measure the
distances of stars.
The Sun will evolve away from the main sequence when
helium builds up in the core, while the hydrogen-burning shell expands.
What is the Helium Flash?
Explosive onset of Helium fusing to make Carbon
In a white dwarf, the mass of the Sun is packed into the
volume of
a planet the size of Earth.
A nova involves
mass transfer onto a white dwarf in a binary star system.
Stars like our Sun will end their lives as
white dwarfs.
The elements heavier than Hydrogen and Helium were created
by nucleosynthesis in massive stars.
The "helium flash" occurs
in the red giant stage.
Stars gradually lose mass as they become white dwarfs during the
planetary nebula stage.
The source of pressure that makes a white dwarf stable is
electron degeneracy.
In a white dwarf, the mass of the Sun is packed into the volume of
a planet the size of Earth.
In a young star cluster, when more massive stars are evolving into red giants, the least massive stars are
barely starting to fuse Hydrogen.
A star will spend most of its "shining" lifetime
as a main-sequence star.
A nova involves
mass transfer onto a white dwarf in a binary star system.
What type of atomic nuclei heavier than helium are most common, and why?
even-numbered nuclei, built with helium fusion
A white dwarf can explode when
its mass exceeds the Chandrasekhar limit.
A Type II supernova occurs when
Iron in the core starts to fuse.
As stars evolve during their main-sequence lifetime
they don't change their spectral type.
More massive white dwarfs are ______ compared with less massive white dwarfs.
smaller