Question

The amount of helium in the MilkyWay compared to hydrogen is about:

1. 1% by mass
2. 10% by mass
3. 40% by mass
4. 80% by mass
5. 99% by mass

[9] Microlensing has been used to place constraints on:

1. How many MACHOs there are in the Milky Way
2. How many WIMPS there are in the Milky Way
3. How many nebulae there are in the Milky Way
4. How many baryons there are in the Milky Way
5. How many dark molecular clouds exist in the Milky Way

[10] Two stars, A and B, have the same luminosity. A has a parallax of 0.5 arcseconds and B has a parallax angle of 0.25 arcseconds. Which of the following is true?

1. A appears twice as bright as B
2. A appears four times as bright as B
3. B appears twice as bright as A
4. B is four times as luminous as A
5. None of the above

[11] Why do we call dark matter “dark?”

1. It absorbs light
2. It does NOT interact with electromagnetic waves NOR the strong nuclear force
3. It does not interact with electromagnetic waves but DOES interact with the strong force    D) It does NOT interact with gravity

   E) None of the above

[12]: What are MACHOs ?

1.    A candidate type of dark matter consisting of objects with masses between asteroids and stars.    B)   Stellar mass black holes

3. Supermassive black holes
4. Neutron stars or white dwarf stars
5. Strong objects

Answer 1

1)

The amount of helium in the MilkyWay compared to hydrogen is about:

40%by mass

2)Microlensing has been used to place constraints on:

How many MACHOs there are in the Milky Way

3)parallax is inversaly proportional to the distance. So starA must be half as far as starB to have twice parallax. Brightness varies with distance according to inverse square law, so starA is four times brighter than starB with both having same luminosity.

A appears four times as bright as B

4)dark matter is called dark because

It does NOT interact with electromagnetic waves NOR the strong nuclear force

5)MACHO's are

Neutron stars or white dwarf stars