Introductory Astronomy: Parallax, the Parsec, and Distances

Video lecture that discusses the concept of parallax, the unit of the parsec, and how astronomers can determine the distances to the most nearby stars.
Since many of you come here because "parsec" is mentioned in Star Wars, I highly recommend you get this book: amzn.to/2R72QoU
Disclosure: some of the links in this video description are affiliate links, meaning at no additional cost to you, I may receive a commission if you click through and make a purchase.

[@Sargentleman]

This didn't really explain how the parallax angle is found. How from the images in January and July do you convert that perceived motion to a parallax angle?

[@amenalyasiry1848]

Very informative video, I would definitely recommend this to anyone that is interested in astronomy, pretty cool.

[@spirit-teacher]

Absolutely the best explanation of parsec on KZbin.

[@charli246]

But how do you measure the angle if it just looks like the star is moving side to side?

[@luisdiniz3211]

Great video! The concepts are explained in a very clear way, such details as the variable used to the inner angle or the unit of distance do not interfere to comprehend the main idea! Good job!

[@ShogunDude]

Awesome video, you just tought me what four books and two videos couldn't!

[@vedanshpaliwal2755]

how do they measure the angle and why "pi" is used as the symbol for unknown angle?????

[@Jenterke]

wouldn't the background stars also move due to parallax? How then to measure the angle of parallax of the star if there is no static background to measure against?

[@juliabudd2150]

This actually helped me a lot thank you so much!! :)

[@weejim48]

Mind officially blown. 👍

[@perobinson]

Thanks!

[@harryzefaa]

Excuse me but i can see that the apparent motion of a star is going to be an ellipse, but i don't understand how from that ellipse you can measure the parallax angle.

[@sabinefrank1061]

Vielen Dank. Nun habe ich das mal so richtig verstanden. Super

[@abhishekbhattacharya8022]

what if the star,sun and earth do not for a right angled triangle?.....

[@MartinPoulter]

+abhishek bhattacharya If you choose the right time in the year to make an observation from Earth, you will always be able to get a right angled triangle.

[@jaredronning3020]

You wait until the time of year at which they do.

[@makmanman]

abhishek bhattacharya You simply adjust your measurement points (i.e. times of the year in earth’s orbit around the sun at which you make your measurements) such that you create a right angle.

[@Jenterke]

Do you after four years know the answer? I'd like to know as well! I suppose that they wait to measure until the earth moves in a position so that it does form a right angle.

[@aspie38]

Very helpful! :)) There's one thing I want to know more about.. For example, If I know a star's parallax angle, how can I relate it to a star's RA/Dec change? at 7:51 he says that the interior angle is the size of the entire shift… so does it mean that, change in RA and parallax angle are directly connected to each other?

[@30hotmale]

Very illustrative and helpful video..Thanks a Lot..BUT: Although, it doesn't make a difference here, it's better if SI units are used in science illustrations and not miles, feet, ounce etc. I think it's a catastrophe to use the symbol "pi" for an unknown angle for obvious reasons.

[@yellowhue30]

What if you mimicked this on a microscopic level, under a microscope? Would it be possible to extrapolate to greater distance through considering a equation related to measurement scaling?

[@rappodschess6211]

this a truely a great video

[@pencils1951]

What he failed to tell you was that a parsec is 3.26 light years, meaning that Proxima Centauri is 3.912 light years distant.

[@alexsh4517]

He said 1.2 parsec

[@pencils1951]

www.universetoday.com/32872/parsec/Alex SH

[@jaredronning3020]

Your point?

[@blazensaddle4721]

Well why don’t you make your own video smarty?

[@mendri789]

@@alexsh4517 1.2×3.26=3.912 light years quick maths

[@aadityaabraham4808]

Thank you. That video really simplified the concept. :)

[@miroslawskovsky-skolyszews6384]

How do you measure that angle?

[@perobinson]

The parallax angle is measured by looking at the apparent position of the same nearby star at least 6 months apart. The angular separation between those positions is measured in arcseconds. Half of that separation is the parallax angle used in the distance calculations.

[@abhijeetsingh3722]

how do we know the distance between the star and the sun

[@amandaarrudamelo]

This video is awesome. Thanks for helping me.

[@joneslu1377]

I think I have got it. Thank you!

[@phongluunguyen1144]

May I ask, what if 3 triangle tops (Earth in January, Earth in July and the nearby star) didn't form an isosceles triangle, how could we measure the distance then???

[@sparhopper]

Just for fun. . . Han was wrong! One cannot make the Kessel Run 'in' 12 parsecs (as a parsec is a unit of distance, not time). It should be: "That's the starship that made the Kessel Run 'of' 12 parsecs, 'in' x amount of time". No?

[@sadjupiter502]

True, unless the objective of the Kessel Run was to go from star A to star B to star C ~12 parsecs usually and he took a shortcut. Traveling slightly slower than light it would take more than 39.1 years, ok for someone like Yoda who is centuries old, major investment for humans. Han could have bought the ship from a very old guy that did it. Lots of variables and very few details. Great video, very concise.Well done.

[@Georg360s]

In a warp of 12 parsecs ;p

[@jaisonat]

Tell this to Crash Course too ( if it is that channel you meant)

[@yiva2037]

I think he uses a wormhole so that's why he made the distance smaller, watch the new movie

[@GoSlash27]

Yeah, but the important part to remember is that he shot first.

[@lexmatthewtheurbanavenger7801]

exquisite as a scientific technician

[@alexcastillonetwork2468]

Even the speed of light has a incredible speed of 300,000km /sec it would be still slow to see it's speed if it will travel across our milky way galaxy which takes 100,000 light years accross..

[@kattimanis623]

Good explanation sir

[@simplysweet3037]

explanations are very useful. thank u .

[@Shardesangz]

Wonderful Thanks! I will definitely share this with my class.

[@hubble2111]

very good explaination ，thx

[@Kimmycrossen]

This is very helpful thank you! ♡

[@deepaklodhirajput292]

Kimberly Crossen you can also watch in crashcourse

[@nothinghamnot1587]

Good vid very nice!!!

[@Gilinator]

thank you!

[@omarjones1460]

How is it that the Millennium Falcon can make the Kessel run in less than 12 Parsecs, when a parsec is a unit of distance and not time?

[@rghos20001]

not bad😃😃😃😃😃😃

[@zizzinosky]

Nice try but... Use "miles" in a scientific video? Use "pi" for unknown angle?

[@perobinson]

Zed Leganerd Most non-scientists in US and UK are familiar with miles, so I see nothing wrong with providing the context occasionally. A working scientist in this field who is familiar with the peculiar units probably has no need of this video. The entire greek alphabet is routinely used for variables in physical sciences for a large variety of specific situations. Such is the case here. Astronomers denote parallax angle using the greek letter pi.

[@EricDunbar97]

+P.E. Robinson I do have to agree with Zed The Bot. Miles? Your target audience almost certainly is capable of understanding kilometers (who on Earth uses miles still?). Brits are completely immersed in the metric system, and, I really hope that Americans are not so poorly educated that they don't understand the metric system either.

[@EricDunbar97]

+P.E. Robinson Please don't get the wrong impression. I do thank you for putting this very nice video on-line!

[@54quesada]

I do.

[@EricDunbar97]

For short distances miles may be acceptable in the UK and the US but for longer distances there's no point to talking about miles for distances an order of magnitude greater than a few thousand units. For someone to conceptually understand the difference between 1000 and 1 000 000 a person must understand the metric system so why bother confusing the issue by using an archaic measurement system? Other than maybe nationalism?

[@martinsalko1]

You haven't used tau, how dare you. *Shouts in Victorian English*

[@ganja_guy8089]

We never see the stars change