Some astro physics questions that need to be answered and explained...?

Question

Explain in detail:

Why can radio astronomers observe at any time during the day, whereas optical astronomers are mostly limited to observing at night?

Why must astronomers use satellites and Earth-orbiting observations to study the heavens at X-ray wavelengths?

Why do astronomers believe that solar nebula was rotating?

What is the minimum core temperature needed for any star begin hydrogen core fusion to helium?

When is any star considered to be fully activated, and when is any star considered to be “middle age”?

Compare the differences between a large and small star, concerning the “elemental fusion” cycles they would produce.

Concerning stars that die (the end of their fusion days), what is usually the difference between the outcome of a small star and the possible outcomes of a large star (ignore binary star considerations).

What is the difference between “electron degeneracy” and “neutron degeneracy”? What type of stellar objects would be an example of each?

Answer 1

Radio astronomers can observe during the day because the atmosphere doesn't scatter radio frequencies like it does visible light frequencies.  That means radio noise from the Sun doesn't completely cloud all other observations.

X-rays are blocked by the atmosphere.  You must get above it to see them. It's true for UV and gamma too. It's mostly true for IR, but you can do that from an airplane or mountain top (with limitations).

Angular momentum is conserved. If planets orbit now, the original nebula must have rotated.

Core temp for fusion: 120 million kelvins. This isn't the whole story.

A star is activated when it starts fusing.  A star is middle age when it settles into a sort of steady state of fusing - not wildly pulsing.

Small stars have convection from the core to the surface. Large stars do not.  So small stars can use all their nuclear fuel. Large stars fuse faster, so live longer.  Large stars can fuse heavier elements, the smallest stars can only fuse hydrogen.

Small stars don't explode, and leave a white dwarf behind.  Big ones can produce supernova. They also can leave neutron star, quark star or black hole behind.

Degeneracy is anything denser than a gas, like water. A star's core may be dense enough that the Pauli Exclusion principal can't keep stuff apart.  You get a white dwarf.  For neutron degeneracy, it's even worse, and you get a neutron star.

Answer 2

Summer sessions are coming to a close.  This looks like a take-home exam.  I'm guessing you have all this information in a book.

This is cheating, pure and simple.  It is grounds for failure, dismissal from a department or expulsion from the school.  I can't help but wonder what you are doing while other people are making an effort to do your work.

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