Unit 12 Homework (10)
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Polk State College *
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Course
1002
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
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2
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1.
What four properties do all newly-formed neutron stars have?
Neutron stars have a large mass and a small size, solid objects that are incredibly dense. Composed of
neutrons packed together in a tight ball. A typical neutron star is not much bigger than a small asteroid.
They rotate extremely fast, direct result of the law of conservation of angular momentum. And the
fourth property is having very strong magnetic fields.
2.
Describe how a pulsar works and why it produces regular pulses of radio emission.
Pulsars are the most extreme example of a neutron star. A pulsar is a rotating neutron star that emits a
beam of electromagnetic radiation that sweeps around the sky like a lighthouse. This beam of radiation
is so powerful that it can be seen from Earth even when the pulsar is billions of miles away. Pulsars emit
cones of bright radio emission from their magnetic poles as they rotate rapidly. Because these stellar
remnants can spin so quickly, their outermost magnetic field lines cannot move fast enough and do not
reconnect.
3.
Do all supernovae create neutron stars? Is every neutron star a pulsar?
Definitely yes. A neutron star can be classified as a pulstar
4.
What two effects are caused by neutron stars in binary systems? How do they work?
Neutron stars in binary systems can have two effects: the formation of binary pulsars and the potential
creation of X-ray binaries. In a binary pulsar, a neutron star orbits a main sequence star and powerful
beams of radiation are emitted from the neutron star's magnetic poles. In an X-ray binary, mass transfer
from the secondary star to the neutron star forms an accretion disk that emits X-rays. When mass
transfer stops, the secondary star may become a white dwarf, or the system can become a neutron star-
neutron star binary.
5.
How are gamma ray bursts distributed across the sky? How are they distributed in
distance from Earth?
Gamma ray bursts are distributed uniformly across the sky, rather then being confined to the relatively
narrow band of the Milky Way. Measuring the distance to a gamma ray is not easy and observations do
not provide enough information to tell us how far away the burst is, so astronomers associated the burst
with other objects in the sky call burst counterpart.
6.
Describe the two models which are thought to explain gamma ray bursts.
The first one is the "true" end point of a binary star system. As the system continues to evolve,
gravitational radiation is released, and the two ultra-dense stars spiral in toward each other. One within a
few kilometers of one another, coalescence is inevitable. Such a merger will likely produce a explosion
and energetic enough to explain the flashes of gamma rays we observe. The second model Is called
hypernova, a failed supernova. A massive star collapses, but instead of forming a neutron star, the core
collapses in on itself, forming a black hole. Instead of being blown to pieces, the star implodes onto the
black hole, forming an accretion disk and again generating a relativistic jet. The jet punches its way out of
the star, producing a gamma ray burst as it slams into the surrounding shells of gas expelled from the
star during final stages of its nuclear-burning lifetime.
7.
Why are black holes called "black"? How does general relativity explain this?
Black holes are called black holes because when the core of a star shrinks, the gravitational pull in its
vicinity eventually becomes so great that nothing-not even light can escape. The resultant object
therefore emits no light, no other form of radiation, no information whatsoever. If earth could be
compressed to less than the size of a grape, the escape speed would exceed the speed of light. Because
nothing can exceed that speed, the conclusion would be that nothing could escape from the surface of
such a compressed body. The planet would be invisible, and no signal of any sort could be sent to the
universe. The origin of a black hole would become clear.
8.
Describe two ways that black holes in binary systems are used to prove the existence of
black holes.
One piece of evidence is from observations of the centers of many galaxies, where astronomers have
found that stars and gas are moving extremely rapidly, orbiting some very massive, unseen object. These
objects are thought to be black holes. Another way it used to prove existence is to look for their effects
on other astronomical objects. The motion of a star and properties of an x-ray source called Cygnus X-1
could be a black hole.
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