I think it is the Milky Way.
The frequency of the wave is 6800 Hz
<u>Explanation:</u>
Given:
Wave number, n = 20
Speed of light, v = 340 m/s
Frequency, f = ?
we know:
wave number = 

Therefore, the frequency of the wave is 6800 Hz
If the temperature increases, then pressure increases too. (T<span>he molecules in the gas move faster, exerting a greater force. This </span>increases t<span>he </span>pressure<span>.)</span>