# Astronomy college course/Solar system (wikipedia)/questions
## Questions

* What happens to the heliosphere at a sufficient distance from the Sun?
* Google this permalink to Planetary mass and list three methods by which the mass of a planet can be measured. (They are mentioned in the introduction at the top of the article.)
* Google the current version of Planetary mass and see if this section has changed.
* What is unusual about calculations of the mass of Pluto made in the early part of the 20th century?

### Introduction

* The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of ___ and ___.
* All planets lie within a nearly flat disc called the ____ ____.
* The frost line is about 5 AU. This number will be given on a test. But you are responsible for answering the following to questions:
   * What is the frost line? (Google or follow link)
   * What does AU mean? (Google or follow link)

### Structure and composition

* Within the context of solar system chemistry, what are volatiles?

### Distances and scales

* Roughly how much bigger (in diameter) is a gas planet than a terrestrial planet?
* Roughly how much bigger (in diameter) is the Sun than a gas planet?
* Estimate the age of the solar system to within a factor of 3
* Estimate the age of the universe to within a factor of 3
* What is thermonuclear fusion and what role did it play in the formation of the solar system?
* Estimate to within a factor of 3 how many years from now will the Sun begin to die?
* What does refractory mean?

### asteroid belt

* The total mass of the asteroid belt is unlikely to be more than a _______ of that of the Earth

### Inner planets

* What is this called, and what is it in geological terms?
* Describe a rift valley on the surface of the earth. What causes a rift valley?
* Mercury's almost negligible atmosphere consists of _________
* The density of Mercury carefully measured when an artificial satellite (from Earth) coasted past the planet, which permitted a measurement of Mercury's gravity. The only plausible explanation is that Mercury has a dense core. One possible explanation for this dense core is _______. (You are only responsible for knowing one hypothesis)
* If the lack of magnetic field seems to predict a depletion of the atmosphere of Venus, what mechanism does Wikipedia propose to replenish this atmosphere. (Note the similarity Oort's cloud and comets: If comets are short lived, some mechanism must act to create new ones.)
* What causes the red color of Mars?
* All planets have almost circular orbits that lie within a nearly flat disc called the ____ ____.
* The frost line is about 5 AU. This number will be given on a test. But you are responsible for answering the following to questions:
   * What is the frost line? (Google or follow link)
   * What does AU mean? (Google or follow link)

### More practice

Name three properties possessed by many or most large objects orbiting the Sun. Briefly describe two of them.
      * Most have reasonably circular orbits.
      * Most lie near the ecliptic.
      * Most orbit the Sun in the same direction that the Sun is rotating
Oort's Cloud is the source of _______ that have _______ term orbits.
Oort's Cloud is the source of comets that have long term orbits.
The solar wind consists mostly of which two elementary particles?
electrons and protons
The solar wind extends out to something called the heliosphere. At that point it is so weak that ______ (finish sentence)
it is weaker than the intersteller gas
The core of the dead sun will be called a ________ and the outer layers will become a ___________ .
The core of the dead sun will be called a white dwarf and the outer layers will become a planetary nebula
The dying sun will contribute ____________ to the Milky Way.
The dying sun will contribute heavy elements to the Milky Way.
What is the solar wind and what role did it play in the formation of the solar system?
      * particles (mostly protons and electrons) escaping from the sun.
      * Most neutral hydrogen is one proton and one electron.
      * The solar wind blew away the dust left over from the formation of the solar system.
Astronomy college course