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ASTR 102 Exam Questions With All Correct Answers Current Update

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ASTR 102

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ASTR 102 Exam Questions With All
Correct Answers Current Update
We have learned that the centre of the milky way contains a very massive black hole.
We developed this understanding by: - Answer -Monitoring the orbital motions of many
individual stars in the very central parts of the Milky Way

If the sun were to be squashed down small enough to become a black hole, then: -
Answer -The planets in the solar system would orbit the Sun in unchanged fashion (but
would receive no light from it)

The first stellar mass black hole identified, Cygnus X-1, was found in 1973. The name is
a clue to what led to the discovery, namely: - Answer -a source of X-rays was found in
Cygnus. In a binary system one star is losing material into the potential well of a dense
object? a black hole

In studying interstellar material, we:
a) use vacuum chambers on earth to simulate the conditions between the planets (but
cannot simulate the conditions in true interstellar space)
b) use vacuum chambers on earth to simulate the conditions between the stars
c) send out space probes to bring back samples from the low-density near-vacuum
regions
d) have to rely on observations since we cannot come close to simulating those
conditions here on Earth. - Answer -d) have to rely on observations since we cannot
come close to simulating those conditions here on Earth.

Will the Sun end its life in a nova? - Answer -it cannot, because the sun is not in a
binary star system with a close companion star

The interstellar medium contains dust, and we have to worry about what effect it will
have on our observations. Careful analysis tells us that - Answer -the remote stars look
fainter and redder than they should, but the spectra reveal the true nature of the stars
under scrutiny

What happens when a more massive star transfers some material to a close companion
of lower mass - Answer -the companion experiences a shorter life because of the extra
mass compresses the star, making it hotter and increasing the nuclear reactions.

We first learned about the existence of rather complex multi-molecules in interstellar
space by - Answer -using radio telescopes to detect characteristic emission given off
when the molecules abruptly change their rates of rotation or vibration

,Astronomers were surprised to find multi complex multi-atom molecules in interstellar
space because - Answer -Such molecules would very likely be disrupted completely by
the energetic photons streaming through interstellar space

Einsteins general relativity has real consequences in day-to-day life, namely: - Answer -
in the system of GPS satellites, high up in the Earth's gravitational potential well, clocks
run at different rates than here at ground level

When new stars are forming, they appear first as: - Answer -bright infrared sources
because they are in the form of very large distended warm gas clouds

When a very massive cloud of gas (say 1000 times the mass of the sun) condenses
under gravity, it ____ - Answer -will fragment into smaller pieces to form a cluster of
stars

A good way of finding a compact binary star system is to look for - Answer -X-rays that
are formed when atoms in the mass-transfer stream collide with the swirling disk of
material and heat it up.

When we look at large clusters of galaxies, we sometimes see rings, or parts of rings of
light surrounding them. this is caused by what? - Answer -caused by the gravitational
lensing of remote background objects, the light of which passes the massive cluster of
galaxies on its way to us.

The black hole at the centre of the M.W has a mass of: - Answer -mass of several
million times the mass of the sun

Large numbers of Mini Black holes, with the mass of an asteroid, could have been
created in the early universe. If so, we might detect them by: - Answer -detecting
present day bursts of gamma radiation as they evaporate by Hawking Radiation

Van de Hulst was the first to predict something important about neutral hydrogen in the
interstellar medium. He realized that it should: - Answer -it should emit a photon from a
spin-flip transition within the atom.

More than 2 centuries ago, Laplace hypothesized that very massive stars might exist
and yet be invisible. He speculated that the light would: - Answer -light emitted y such a
star would start moving outward but be slowed by gravity, come to a halt, and fall back
down.

When we detect the presence of a black hole in the MACHO project, we then: - Answer
-there is nothing more to be done: as the black hole continues its motion, its
gravitational effect on the stars light never returns.

Giant Molecular Clouds (GMCs) in the M.W may contain as much as ____ solar masses
of material: mostly ______ and ______, but including many ________. - Answer -

, 100,000 solar masses; mostly hydrogen and helium, but including many complex
molecules

The trajectory of light is determined by - Answer -determined by distortions in space that
are caused only by the rare very massive objects

The famous 21 cm emission from neutral hydrogen gas was predicted in 1944. it is
particularly important because - Answer -this long-wavelength radiation is of relatively
high energy, which explains why the gas clouds in the M.W are glowing: it is because of
fluorescence

Black holes of small mass (like the mass of an asteroid) could have been created: -
Answer -could have been created in large numbers in the early universe and so could
be all around us in the universe

A "MACHO" strategy for searching for black holes has been used in recent years and
involves: - Answer -looking at crowded star fields to see if any stars temporarily brighten
up as a black hole passes between us and them. gravitationally focussing the light.

When mass is transferred in a binary star system it forms a - Answer -forms a whirlpool
like disk around the receiving star because of the mutual orbital motion of the stars

Interstellar dust grains absorb light, which is a form of energy. as a result, the dust: -
Answer -the dust grains glow at infrared wavelengths

In a close binary star system, matter will certainly flow from - Answer -the more massive
star to the low mass star because the more massive star expands as it evolves

Supernovae can occur when very massive stars run out of fuel at their centres. A
different kind of supernovae, also very bright arises when: - Answer -a white dwarf in a
close binary pair is close to the Chandrasekhar limit. Mass exchange from its
companion can take it past that critical mass

In a star's spectrum, the absorption lines caused by Interstellar gas can be distinguished
because: - Answer -The absorption lines are much narrower than those in the spectrum
of the star itself.

Oblers paradox cannot be explained by a dusty interstellar medium (ISM) that blocks
our view of remote galaxies because: - Answer -the material in the ISM would absorb
radiation and given infinite time, begin to glow as brightly as the stars

Some of the nearest galaxies do not share in the expansion of the universe? the
Andromeda spiral, for one. This is because: - Answer -It is part of the Local Group,
within which local gravitational effects can dominate over the expansion

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