Can someone explain abberation of starlight?

[Pharaoness]

Hello everyone,
I was wondering if anyone can explain how the abberation of starlight works in general terms, as well as what exactly it is. I am a first year astronomy student and this is for my astronomy/physics class, and would like a general explanation of what it is. This is all my professor would require for the upcoming midterm, so if anyone can help that would be great. Thanks!

 

[Simon Bridge]

Welcome to PF;
The best use of these forums is to give your ideas of what it is and that will help us pinpoint the source of your confusion. Have a go reading through:
http://en.wikipedia.org/wiki/Aberration_of_light
... and telling us where you get lost.

 

[Pharaoness]

Thank you for responding Simon! I guess I should have elaborated on what I understand and what I would like to know. So I know that this is not like parallax in that it depends on velocity, so while parallax increases the further out you go in the solar system, aberration of starlight increases the closer to the Sun a planet is (because the closer to the Sun a planet is, the faster its orbital velocity). Hence, from Mercury the aberration ellipse is greater than aberration ellipses on Earth.
I guess what I'd like to know is how exactly aberration works? My professor was explaining it to be almost like walking, or running in the rain, if the rain is falling straight down (ie, perpendicular to the floor) but you are running, because of your velocity, it is like they are falling on an angle, so you would need to tilt your umbrella to shield the rain. So does the latitude of a person have an effect on the amount a telescope needs to be tilted? And what exactly does an aberration ellipse look like? Does that make sense? Thanks!

 

[Pharaoness]

Additionally, what I read about aberration online is that what you expect to see is tan (theta) = v/c, but what you actually find is that sin (theta) = v/c. Why is this, and what does it mean? On Wikipedia it says the same thing. I'll read it in its entirety, but if you can help with that that would be great. Thanks! :)

 

[pmacias]

Sure, I'd be happy to explain the concept of abberation of starlight. Abberation of starlight is a phenomenon that occurs due to the relative motion between Earth and a star. As Earth orbits around the Sun, it is constantly changing its position in space. This means that the direction of Earth's velocity is also constantly changing.

Now, imagine a beam of light coming from a distant star towards Earth. Because of the changing direction of Earth's velocity, the light from the star appears to be coming from a slightly different direction than it actually is. This is known as abberation of starlight.

To understand this better, think of it like standing in the rain and holding an umbrella. If you are standing still, the raindrops will fall straight down onto the top of your umbrella. But if you start walking, the raindrops will appear to be coming from a different angle because of your motion.

In the same way, the light from a star appears to be coming from a different direction due to the motion of Earth. This effect is very small, and can only be observed for objects that are very far away, such as stars.

Abberation of starlight was first discovered by the astronomer James Bradley in the early 18th century. It is an important concept in astronomy as it allows us to measure the speed of light and also to study the motion of stars and other celestial objects.

I hope this explanation helps. If you have any further questions, please don't hesitate to ask. Good luck on your midterm!