Proper Motion and Parallax

[@JasonKendallAstronomer]

Please see the remastered version here: kzbin.info/aero/PLyu4Fovbph6cytm2oy4ctBOLMpNlakQp3&si=eRj5PGxrwgP7ccCs

[@YUVRAJSINGH-le7eg]

Absolutely amazing sir, I never thought I'd understand it in such a simple and interesting manner .absolutely nailed it

[@nubairanira]

This is an excellent one. Want a video on Lagrange points.

[@pat8988]

I love these series of astronomy videos. I used to prefer PBS "Nova" type videos but they seem like kindergarten programs after watching these. :)

[@MrKracx]

at @25:51, why do you not take 4.74 tan(mu) * d? Why did the tan disapear in your equation?

[@JasonKendallAstronomer]

Good question! the TAN function assumes we are measuring in "radians" or "degrees", but really, it's always "radians". However, what we measure in the wild are arc-seconds. So the "angle across the sky", is very small. Thus the approximation.

[@Mike_Toreno]

So what it basically means is that if the celestial sphere was a X-Y axis plane and the Z axis is the axis perpendicular to the plane, proper motion is the velocity along the X-Y plane and radial velocity is the velocity along the Z axis right?

[@JasonKendallAstronomer]

Well, yes, but that analogy breaks down fast when you think about it.

[@yumastaubli6338]

I am currently working on a school project and have two questions: To measure the radial velocity correctly, what formula should be used? (I can't find any good explanations on what formula to use when working with electromagnetic waves) Is the redshift caused by the expansion of spacetime negligible? If not, how much adjustment is needed? Thank you for taking the time to make these videos, they are incredibly interesting and informative, Best wishes from switzerland :)

[@JasonKendallAstronomer]

Watch my series on Light, starting here: kzbin.info/www/bejne/j6OuhZ1qeLBqo68 Redshift only matters in size scales of Megaparsecs. all the best!

[@dhikshithbalaji1714]

Hello sir, Your video was extremely helpful. I am actually doing my Maths IA (if you are aware of IB diploma) on measuring star distances using the parallax method. I am trying to analyse this topic in-depth to achieve a good grade as just describing the parallax method won't be enough. You did mention proper motion and true motion of stars but I can't quite understand how true motion can help with calculating star distances. Can you please suggest me if there are any other concepts that I can take into account for achieving a good analysis of the topic?

[@JasonKendallAstronomer]

Look up how we get the distances to the Hyades and Pleiades using not just parallax but also proper motion studies.

[@JasonKendallAstronomer]

Also watch my video on the cosmic distance ladder.