Astro 1500 Final Exam Review Part 1 (exams 1 and 2)

The hypothesized planet nine would orbit around 500 AU from the sun, using Kepler's 3rd law, what would be it's period in years?

• 63 years

• 11,180 years

• 1,450 years

• 101,600 years

Answer explanation

P^2 = a^3, so we have a semi major axis of 500 AU, which is a. Here, (a^3)^0.5 = P = 11180 years, a very long time.

Tags

NGSS.HS-ESS1-4

Star 1 is 2 times hotter than Star 2, what is the ratio between the lengths of peak wavelength emitted? (λ_1 / λ_2)

• 1/2

• 2

• 1/4

• 4

Answer explanation

Star 1 is twice as hot, so it's peak wavelength will be half as much. (show in more detail on the board)

If you triple the diameter of a telescope, by how much the does resolving power increase?

• 3 times more powerful

• 3 times weaker

• 2 times more powerful

• 2 times weaker

Answer explanation

A 3 times increase in diameter will decrease theta min by 3 times, meaning that the telescope can see things that are three times smaller in the sky, making it 3 times more powerful.

Tags

NGSS.HS-PS4-3

Let’s say that you build your own radio interferometer consisting of two dishes. You keep the dishes the same size, but move them farther apart. In doing so, which of the following is true about resolving power and light gathering power?

• 
  The light gathering power remains the same, while the resolving power becomes better.

• 
  Both the resolving power and the light gathering power become better.

• The resolving power remains the same, while the light gathering power becomes better.

• Both the resolving power and the light gathering power stays the same.

Answer explanation

The distance is what affects the resolving power.

Tags

NGSS.HS-PS4-3

A wavelength of 0.001 m corresponds to a temperature of what? (Hint: Use Wien's law)

• 1. 1.2 K

• 2.9 K

• 12 K

• 29 K

Answer explanation

λ = 2.9*10^3/T, thus T = 2.9*10^3/lambda and T = 2.9*10^3/0.001 = 2.9. (Show on board)

You observe two stars. Star #1 looks blue, and Star #2 looks red. Which one has a lower temperature?

• Star 1

• Star 2

• We cannot know with this information

Answer explanation

Very hot stars will glow blue, so red is a lower temperature. This is due to wien's law again, a lower wavelength corresponds to a higher temperature, as is seen in the previous question.

Tags

NGSS.HS-PS4-3

What happens to an electron in an atom that produces an emission line?

• It goes to a lower energy orbit

• It goes to a higher energy orbit

• Nothing

• It leaves the atom

Answer explanation

When an electron jumps from a higher to a lower energy level, it emits some energy in the form of a photon (ie an emission line)

Tags

NGSS.HS-PS1-2

NGSS.HS-PS4-3

What did the Copernican revolution represent in terms of how humans think about the Universe?

• We learned to use intuition and divine revelation to answer questions

• We realized that gravity is both responsible for things falling to Earth and keeping planets in orbit.

• We found ways to observe the Universe and as such, astronomy was born

• We learned to use empirical evidence to answer questions

Answer explanation

Copernicus used actual data to justify his claims, not just trying to logic it out like the greeks and others did

Everything else remaining the same, if you triple a star's temperature, the luminosity increases by __ times.

• 3

• 9

• 27

• 81

Answer explanation

All else remaining the same, the only thing that matters is the temperature, so T^4 --> (3)^4 = 81 times more luminous.

Order the types of light from most to least energetic

• Gamma, X-ray, visible, UV, Radio, IR, Microwaves

• Microwaves, Radio, UV, Visible, X-Ray, IR, Gamma

• Radio, Microwaves, IR, Visible, UV, X-ray. Gamma

• Gamma, X-ray, UV, Visible, IR, Microwaves, Radio

Answer explanation

Gamma rays are the most energetic, the order follows: Gamma, X-ray, UV, Visible, IR, Microwaves, Radio

Tags

NGSS.HS-PS4-1