ASTRO EXAM 2
What is the upper limit to the mass of a white dwarf?
1.4 solar masses
How many globular clusters are known to orbit the Milky Way galaxy?
150
Einstein suggested that the regular change (advance) in the perihelion of the planet Mercury could be explained by:
A distortion in spacetime caused by the gravity of the Sun
What happens to the core of a high-mass star after it runs out of hydrogen?
Carbon fusion begins right away
Which of the following is closest in size to a white dwarf?
Earth
Black holes, by definition, cannot be observed directly. What observational evidence do scientists have of their existence?
Gravitational interaction with other objects.
Hubble space telescope has been particularly useful for the study of globular clusters because
Its resolution allows to observe the stars in the cores of these clusters
Which kinds of stars are most common in a newly formed star cluster?
M stars
Why does the rotation of a protostar slow down over time?
Magnetic fields can transfer angular momentum to the protostellar disk and protostellar winds can carry angular momentum away.
A 100-solar-mass main-sequence star will produce which of the following remnants?
Neutron star
Which of these elements can't be made by nuclear fusion in the core of a star?
Uranium
Which of the following stars will certainly end its life in a supernova?
a 10-solar-mass star
Which of these stars has the shortest life expectancy?
a 100 solar mass star
Which of the following is closest in size (radius) to a neutron star?
a city
The distortion of spacetime will be bigger for a star of what type?
a neutron star
Astronomers call a ball of matter that is contracting to become a star
a protostar
The first, indirect detection of gravitational waves in the 1970s involved
a pulsar that was in the same star system with a neutron star
what is a pulsar?
a rapidly rotating neutron star
Why is it so difficult for astronomers to see new stars in the process of birth?
all of the above
When Einstein proposed his General Theory of Relativity, he suggested some pretty strange ideas about space, time, and gravity. How did scientists in 1919 show that Einstein's theory described the behavior of the real world and wasn't just a crazy hypothesis?
by observing starlight coming close to the Sun during an eclipse
According to the general theory of relativity, the presence of mass
causes a curvature (or warping) of spacetime
Compared to the star it evolved from, a red giant is
cooler and brighter.
After a massive-star supernova, what is left behind?
either a neutron star or a black hole
What kind of pressure supports a white dwarf?
electron degeneracy pressure
If you are in a freely falling elevator near the top of a tall building, as the elevator falls, your weight would be:
equal to zero - you would be weightless
What is a key reason that gravitational waves are so much harder to detect than electro-magnetic waves?
gravitational waves are much weaker than electromagnetic waves, and therefore require very, very precise equipment to detect
If you want to find stars that are just being formed, where are the best places to search?
in giant molecular clouds
When a star settles down to a stable existence as a main-sequence star, what characteristics determines where on the main sequence in an H-R diagram the star will fall?
its mass
Astronomers believe that disks of material will form around protostars that are spinning. Which of the following observed phenomena is a good indication of the presence of a disk around a protostar?
jets
The normal stars that are left in a globular cluster are mostly
low mass red stars
What kind of elements are found in the old stars found in globular clusters?
mostly lighter elements
Loosely bound collections of dozens or thousands of stars, usually in an irregular shape, are called
open clusters
The surface of a protostar radiates energy while its core
shrinks and heats.
Which of the following is not something typically used to identify exotic binaries in globular clusters?
spectra
When we see X rays from an accretion disk in a binary system, we can't immediately tell whether the accretion disk surrounds a neutron star or a black hole. Suppose we then observe each of the following phenomena in this system. Which one would force us to immediately rule out the possibility of a black hole?
sudden, intense X-ray bursts
Which of the following is closest in mass to a white dwarf?
the Sun
The principle of equivalence says that
the effects of gravity are equivalent to the effects of acceleration
What is a planetary nebula?
the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star
n the first direct detection of gravitational waves by LIGO in 2015, the waves came from
the merger of two black holes
Which of the following statements about the way the mass of a white dwarf affects spacetime is correct?
the white dwarf mass will curve spacetime; light has to follow that curvature
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
