Would the aberration of starlight be greater or less on Pluto than on Earth? Why?......?

Question

Assue there are beings living on Pluto who are interested in Astronomy. Their Astronomers are able to measure the apparent positions of stars( i.e. angles between stars) with the same accuracy as we can here on Earth. The distance from Pluto to the Sun is about 40A.U.
1)Would the aberration of starlight be greater or less on Pluto than on Earth? Why?
2)How much dimmer does the Sun appear from Pluto than from the Earth?

Answer 1

1) the further out an object orbits, the slower it moves. The aberration of starlight is a funtion of orbital speed relative to the speed of light, so it will be less on Pluto.

2) Light intensity falls off as 1/r^2, or 5log (D/d) in magnitudes.

Answer 2

If you are referring to atmospheric aberration, it would be very slight, as Pluto has hardly any atmosphere at all. And the sun is 1/1600th as bright from Pluto than it is from earth.

The good news is that you'd be able to estimate distances to stars much better using heliocentric parallax because your orbit is so large. The bad news is that it would be decades between the two measurements for one star. But the good news again is that there are lots of stars!

What, pblc box??? What kind of aberration are you talking about? And no, the brightness of the sun would be the inverse square law, or 40^2, or 1600 times fainter.

As for the sun looking like a bright star, I have heard people say that. But boy, what a bright star! If it is 1/1600 as bright as we see it, that is 8 magnitudes less. For us the sun is -26. On Pluto, then, it would be -18. Our full moon is -12. So this "bright star" would be 250 times brighter than our full moon. Yeah, that's pretty bright. I think you could look right at it, though.

Answer 3

Wow - a two-part question!!!

Okay, let's tackle the first part of your question, shall we? Since, technically speaking, the aberration of a star's light is caused by a planet's orbit, it would be necessary to find out just how fast Pluto is traveling in relation to Earth. So here are the facts (roughly speaking): Pluto is 40 AU from Sol. Earth is 1AU from Sol. Pluto takes 248 years to complete one orbit, while Earth takes 1 year. Since the circumference of a circle can be calculated using c=2*pi*radius (2*3.14159*40AU -Pluto or 2*3.14159*1 - Earth) and since velocity is distance traveled over time, it turns out that the Earth is moving about 6 times faster than Pluto, even with the shorter orbital distance. That said, the aberration of starlight will be far less (about 6 times) on Pluto.

Secondly, the sun is 40AU away from Pluto, therefore it will be about 40 times less bright - in other words, it will be a moderately bright star, but without the disc-shape we commonly associate with our Sun.