Which of these is a correct inference that can be draw from the observation of the two spectrums? A. The spectrum of a motionless star is difficult to be viewed separately using ordinary telescopes. B. The spectrum of a motionless star is identical to the spectrum of a star which moves towards Earth. C. The spectrum of a star shifts towards the red region when the start moves toward Earth. D. The spectrum of a star shifts towards the blue region when the star moves towards Earth

Question

anonymous · Answer

attachment

theeric · Answer

Hi! Do you have any guesses?

anonymous · Answer

I was thinking B

theeric · Answer

Alright, why do you say that?

anonymous · Answer

because when you look at the lines on the graph you can see them go all the way through on both sides

anonymous · Answer

Oh wait wouldnt it be C?

theeric · Answer

Sorry I left for a little bit! One moment!

theeric · Answer

And you're right in that it is not B, because you can see that they are not the same, and that the wavelengths of light that are observed (and not observed) are different.

theeric · Answer

Now, if you look at the picture, you see that you have the same visual spectrum, but there are black bars in different spots.

theeric · Answer

The black lines are wavelengths that are blocked because of the star's atmosphere absorbing them, I think. That's why they are black - there is no color there.

Now, these lines are shifted because the color of fast moving objects is distorted (it's the nature of light). Which direction did they shift? Towards the red, or the blue?

theeric · Answer

The arrows in the picture show how we observed the moving star to be.

You are studying the red shift and blue shift. That means the spectrum shifts to the red side (larger wavelength) or blue side (smaller wavelength).

This picture isn't how it works at all... but you can imagine you and the star beeing connected by a slinky (to be like a light wave).
Pull the slinky out and keep it still. This is when you're at the same speed as the star.
Now put them closer together.

theeric · Answer

The draw feature isn't working for me right now, sorry...

Anyway....
So you see that the spectrum is shifted to the left in the picture, towards the blue.

This is a blue shift and it makes sense for if the star is moving towards us.

The wavelength gets shorter, just like the distance between the slinky spirals when things are moved closer together.

For the slinky, closer together means that the star is coming at you faster. Farther apart means the star is traveling away from you. Feel free to let me know if you have any questions.

anonymous · Answer

answer is c