ASTR 102 exam| Questions with 100% Solutions| A Rated
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Course
ASTR 102
Institution
ASTR 102
he 'size' of a black hole is given by the Schwarzchild radius. For the earth this is about 1 cm. This means
that: - if the earth were somehow to be shrunk to this size, gravity would win and there would be
an inevitable collapse to a 'singularity' at the center
In addition to supernovae formed f...
ASTR 102 exam| Questions with 100%
Solutions| A Rated
The 'size' of a black hole is given by the Schwarzchild radius. For the earth this is about 1 cm. This means
that: - ✔✔if the earth were somehow to be shrunk to this size, gravity would win and there would be
an inevitable collapse to a 'singularity' at the center
In addition to supernovae formed from the collapse of massive stars as they run out of fuel, supernovae
of another kind are produced when: - ✔✔a white dwarf near the 'Chandrasekhar limit' has extra
matter dumped onto it from a companion in a binary star
The first stellar mass black hole, Cygnus X-1 was found in 1973. The name is a clue that led to the
discovery, namely - ✔✔the constellation Cygnus is like a cross in the sky, with the wings, head and
tail of a big swan. The black hole is near the center of this giant X
The dust grains in interstellar space have the consequence that: - ✔✔the interstellar medium is
much 'smoggier' than the air in a typical big city
An HII region (a cloud of ionized hydrogen) like the Orion Nebula glows because - ✔✔it is fluorescing,
having absorbed energetic ultraviolet photons from hot O and B stars
Astronomers were surprised to find complex multi-atom molecules in interstellar space because -
✔✔
Interstellar dust grains are elongated. We know this because - ✔✔light from the stars
becomes polarized as it passes through the interstellar dust
Some of the nearest galaxies do not share in the expansion of the universe- the andromeda spiral for
one. this is because - ✔✔it is part of the 'Local group' within which local gravitational effects can
dominate over the expansion
The 'plane of avoidance' refers to the fact that - ✔✔stars in the center of our galaxy are not
visible because of obscuring interstellar dust
, The rotation of our galaxy can be demonstrated because - ✔✔stars on one side of us appear to
overtake us as they 'pass on the inside track'; stars on the other side appear to be falling behind as
we pass them
The Leavitt Law sates that - ✔✔the cepheid stars with long periods are brighter than those with
short periods
Van Maanen concluded that the spiral nebulae must be intrinsically small and relatively nearby. This
conclusion was based on: - ✔✔his finding that the nebulae appeared to rotate on photographs
taken decades apart.
The material in the centre of the Sun obeys the relativity simple "perfect gas law" because -
✔✔even though the density in there is much greater than that of lead, all of the material is
completely ionized because of the very high temperature
The stars in our 'Solar neighbourhood' have individual velocities of about 30 km/sec, so they travel
about 1 light year through space every 10,000 years. We have deduced that - ✔✔stars almost
never closely encounter one another, because they are moving in random directions in the vastness of
space
The first parallax measurements of the nearest stars were made in 1837. Using specialized instruments
on orbiting satellites, we have now directly measured parallaxes for: - ✔✔several thousand stars, out
to a distance of a few hundred light years from the sun
The magnitude scale is such that a star of magnitude zero: - ✔✔is quite bright, but there is
otherwise no particular significance to the number
A redshift means the star is moving .... - ✔✔moving away from us
The elements in the universe are distributed in an odd-even abundance pattern. We now understand
that this is because - ✔✔the progressively heavier elements are produced when helium nuclei (and
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