The presence of disks of gas and dust around protostars is a theoretical concept
ID: 298240 • Letter: T
Question
The presence of disks of gas and dust around protostars is
a theoretical concept which has not been confirmed by observations
a theoretical concept which has been confirmed by observations
an observational result which cannot be explained by current theories of star formation
a phenomenon which is not supported by either theory or observation
The shell of a planetary nebula is measured by the Doppler shift of emission lines to be expanding outward at a speed of 8 km/s and its diameter is measured to be 1 light year (which is about 9.46 1012 km). How long has the shell been expanding?
19,000 years
8 million years
19 million years
8,000 years
If the Sun were suddenly transported to the nuclear bulge of the Galaxy, the number of nearby stars would be
about the same as what we see from our present position in the Galaxy
far fewer than what we currently see
about twice what we currently see
much greater than what we currently see
Which is a correct statement about dark matter?
Dark matter is composed of normal matter that is too cold to emit light
Dark matter is composed of normal stars which are blocked by dust
We believe that it is there by its gravitational effects, but we don’t know what it is
We don’t really know if it’s there, but it helps explain quasars if it is
According to Olbers’ paradox, the night sky should be bright, not dark, because
in a finite universe, our line of sight will eventually intersect a star
in an infinite universe randomly scattered with stars, every line of sight should eventually intersect a star
the space between the stars is filled with dust, which also emits light
the Earth’s atmosphere should refract sunlight around to the night side of the Earth
A.a theoretical concept which has not been confirmed by observations
B.a theoretical concept which has been confirmed by observations
C.an observational result which cannot be explained by current theories of star formation
D.a phenomenon which is not supported by either theory or observation
Explanation / Answer
1. The presence of disks of gas and dust around protostars is
Answer is B.
A theoretical concept which has been confirmed by observations
Explanation : A region, based on observations of continuous emission from the dust and line emission from the molecular gas.
A theoretical concept which has been confirmed by observations
Explanation : A region, based on observations of continuous emission from the dust and line emission from the molecular gas.
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