Astronomers observe huge bubbles of hot gas, some over a thousand ...

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Astronomers observe huge bubbles of hot gas, some over a thousand light years across, in the Milky Way. What is their cause?
 
  What will be an ideal response?

Question 2

What evidence led astronomers to conclude that the Oort cloud is a spherical distribution of comets?
 
  A) the observation that comets enter the solar system from random directions
  B) direct observation of comets orbiting the sun in the Oort cloud
  C) Astronomers did not draw that conclusion; the Oort cloud is shaped like a flat ring in the same plane as the planets.

[underwood14]

Answer to Question 1

These huge bubbles, called superbubbles, arise from many supernovae occurring close together in both space and time. The supernovae occur close together like this because stars tend to form in clusters and massive stars live for a relatively short time. When the massive stars in a cluster go supernova, they are still relatively close together and explode within a few hundred thousand years of each other (which is a short time compared to other galactic timescales).

Answer to Question 2

A

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TY

[underwood14]

You're welcome