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Exam 3
Normal Galaxies and Large Scale Structure
51
Astronomy
05/02/2012

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Term
Why are star clusters ideal "laboratories" for stellar evolution
Definition
Their stars are all about the same AGE, COMPOSITION, AND DISTANCE from us.
Term
What are the characteristics of an open cluster of stars?
Definition
a few hundred, mostly main-sequence stars
Term
Which is characteristic of globular star clusters?
Definition
old age and hundreds of thousands of stars, only about 30 ly wide
Term
on an H-R diagram, a protostar would be
Definition
above and to the right of the main sequence.
Term
A newly formed protostar will radiate primarily at which wavelength
Definition
infrared
Term
Neutral hydrogen atoms are best studied from their energy given off as
Definition
21-cm waves in the radio
Term
The most common molecule in a molecular cloud is
Definition
molecular hydrogen, H2.
Term
A large gas cloud in the interstellar medium that contains several type O and B stars would appear to us as
Definition
an emission nebula.
Term
What two things are needed to create an emission nebulae?
Definition
hot stars and interstellar gas, particularly hydrogen
Term
Some regions along the plane of the Milky Way appear dark because
Definition
stars in that region are hidden by dark dust particles.
Term
A star has a parallax of 0.01 arc seconds. Its distance is
Definition
100 parsecs.
Term
If Vega is apparent magnitude zero, and Deneb first magnitude, then
Definition
Vega is 2.5× brighter than Deneb.
Term
What physical property of a star does the spectral type measure?
Definition
temperature
Term
Which of these stars would be the hottest?
Definition
B0
Term
What can be said with certainty about a red star and a blue star?
Definition
The blue star is hotter than the red star.
Term
The star's color index is a quick way of determining its
Definition
TEMPERATURE
Term
The H-R diagram can plot
Definition
temperature versus luminosity.
Term
On the H-R diagram, the bright blue stars that dominate the naked-eye sky lie
Definition
at the top left.
Term
On the H-R diagram, white dwarfs Sirius B and Procyon B lie
Definition
at the lower left.
Term
The temperature of the photosphere is about
Definition
5,800 K.
Term
Given that a large sunspot, about 100× smaller than the Sun, is about the same size as our planet, how many Earths could fit inside the Sun's vast volume?
Definition
one million
Term
The density of the Sun is most similar to which object?
Definition
Jupiter
Term
What two energy transport mechanisms, in order from outside the core to the surface, are found
Definition
radiative diffusion, convection
Term
How long does the sunspot cycle last, on average?
Definition
about 11 years
Term
Sunspots
Definition
come in pairs, representing the north and south magnetic fields.
Term
Sunspots are dark splotches on the Sun. Which statement is true?
Definition
They are extremely hot, but cooler than the surrounding areas of the Sun.
Term
The critical temperature to initiate the proton-proton cycle in the cores of stars is
Definition
10 million K.
Term
In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?
Definition
it is converted to energy
Term
what temperature is needed to fuse helium into carbon?
Definition
100 million K
Term
a star is on the horeizontal branch of the H-R diagram. Which statement is true?
Definition
It is burning both HYDROGEN and HELiUM
Term
During the hydrogen shell burning phase
Definition
the star grows MORE luminous
Term
Compared to our Sun, a typical white dwarf has
Definition
about the same mass and a million times higher density
Term
Of the elements in your body, the only one not formed in stars is
Definition
hydrogen
Term
An iron core cannot support a star because
Definition
iron cannot fuse with other nuclei to produce energy
Term
Type II supernovae occur when their cores start making
Definition
iron
Term
If it gains sufficient mass, a white dwarf can become a
Definition
Type I supernova
Term
A recurrent nova could eventually build up to a
Definition
Type I supernova.
Term
Noting the turnoff mass in a star cluster allows you to determine its
Definition
age
Term
The helium flash converts helium nuclei into
Definition
carbon
Term
A solar-mass star will evolve off the main sequence when
Definition
it builds up a core of inert helium
Term
Two important properties of young neutron stars are
Definition
extremely rapid rotation and a strong magnetic field.
Term
Who discovered the first four pulsars?
Definition
Martin Schwartzschild
Term
The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is
Definition
greater than Schwalimit of 3 solar masses.
Term
An observer on planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at
Definition
c
Term
The largest known black holes
Definition
lie in the cores of the most massive galaxies
Term
You would expect millisecond pulsars to be
Definition
part of a binary system
Term
A hypernova creates
Definition
a black hole
Term
What explanation does general relativity provide for gravity?
Definition
Gravity is the result of curved spacetime.
Term
If light from a distant star passes close to a massive body, the light beam will
Definition
bend towards the star due to gravity.
Term
A method for identifying a black hole is to
Definition
look for their effects on nearby companions
Term
Is the sun a star?
Definition
NO!!