How We Mapped the Stars

[Music] I've been playing around with a really amazing it's a map of the solar system recently I got really curious and I started to zoo me out well past the solar system and deep into the night sky and this kind of blew my mind we have mapped these stars that are so far away from us light-years away and yet here they are on this map somehow positioned in space this seems impossible to me how is it that we're able to from this little speck of dust look up and somehow gauge how far away things are like this one specific star how do we know that this is eight hundred and sixty four point three light-years away I mean that's like eight quadrillion kilometers it's insanely far the story of how we did this how we measured the distance to these incredibly faraway objects in the sky it's a story of people looking up and asking questions and in the process creating a map of the heavens in the old days people knew about the planets but they thought the stars were in some sort of vault of heaven just a bit further away than the planets so mapping the night sky this is a big topic let's start small first the stuff close to us how do we know how far Jupiter is and the moon and all of that from here the methods get trickier and trickier the further away you get but for now the solar system measuring the distance the planets is relatively easy because we see the planets move we see them spin around the Sun and we can observe their behavior over the course of decades and generations and record that after a lot of observation we realized that the planets go around the Sun and they go in this kind of elliptical shape they don't go like in a perfect circle you can then observe that the planets start moving quicker the closer they are to the Sun because of gravity gravity pulls it in and whips it around observing the planets and how they move around the Sun allowed one very smart german astronomer who apparently exclusively ate with chopsticks I'm kidding I know they're not chopsticks okay it's just a joke it's actually just like a compass hahaha anyway this guy Johannes Kepler used his chopsticks to measure all of this movement how the planets moved he plotted it and he came up with some really savvy equations and ratios and laws that gave us the average distance to each planet suddenly the night sky went from 2d to 3d for the first time which gave us a place a physical place relative to all these planets floating around the Sun okay but this is child's play when it comes to measuring distances in space these planets are like our next-door neighbors so now let's step into the big leagues and talk about how we started to map stars and their distance from Earth for the stuff that's not orbiting the Sun that's really far away we can use a concept called parallax wait a minute parallax parallax sounds strangely familiar when talking about physics and space it was alright and it was said that but he goes by the pseudonym parallax that's that great name ok no no not that parallax the pseudo scientist from the 1800s I'm talking about the scientific concept parallax is a concept that says that if you're observing something far away and you shift your position relative to that far away thing the far away thing will look slightly different relative to the background ok so let's say we're looking up at the night sky and we want to know how far away this star is remember that Earth is always floating around the Sun at any given time which is moving us in space so if we observe this star in May and then wait six months till November and observe that star again we've now gained a new perspective on the star and what it looks like relative to its background this gives us an angle that we can use to calculate this distance what we don't know is this value this is the distance this is what we're looking for but we do know a few things we know this distance because it's just the distance from Earth to the Sun which happens to be 149 million kilometers or one astronomical unit so this distance times two and then we also know this angle up here because we measured it from two different perspective thanks to the wizardry that is trigonometry we can use this distance and this angle to determine what this distance is this works really well and it's allowed us to measure the distance to a lot of stars but remember that a key ingredient to this whole parallax thing is the slight shift in perspective between the first angle and the second angle as you start to measure things that are further and further away this angle becomes slider and slider until eventually it becomes impossible to discern it's so minuscule the perspective shift that you can't actually detect it so there's a limit to how far parallax goes with our earth-based telescopes we've been able to perceive the angle enough to where we can see things that are about 300 light-years away I mean that is way bigger than like the things that are close to us in the solar system but it's still a tiny number compared to like the galaxy or the universe luckily we have fancier tools like this guy that have really good technology for detecting these slight angle differences from tooten perspectives of a star and that's allowed us to observe and measure the distance to stars that are up to 3,000 light years away way further out okay so here's where we're at with Kepler's fancy equations watching the planets move around the Sun we've been able to measure the distance to planets with parallax we've been able to measure the distance to stars that are really far away and get a 3d map of our galactic neighbors but we're still not really scratching the surface of the distances that exist in the universe so how do we do that [Music] this is where it starts to get kind of crazy and tricky and weird and I'm gonna do my best to explain this in a way that comes through so here we go one of the major methods for measuring the distance to super far away stars and galaxies was pioneered by a computer at Harvard in 1912 what a computer in 1912 yeah that's what I said a computer at Harvard in tanking but computers were invented no to the 1950s but computers in 1912 looked like this this is a group of women who worked in Harvard's Astronomy Department in the early 1900's their job title was literally computers meaning someone who executes predetermined logical calculations on large inputs of data Harvard astronomers were taking loads of photos of the night sky with their new fancy telescopes the images came out like this glass plates with photos of the night sky developed on them the computers were tasked with looking at each of these plates and naming and classifying the Stars by their brightness and their type they were basically creating a 2d map of the sky they didn't know how far away they were they just were classifying their position in the night sky relative to our perspective on earth at the time a lot of legit astronomers figured that what was in our galaxy was all there was to the universe we had no idea of knowing how far away some of these objects were so we just figured that maybe everything is somewhat close by in our galaxy one of these computers was named Henrietta she was assigned to focus on one big cluster of stars in the night sky and to look at and classify those stars she documented thousands of stars but was bothered by this one question if you look up at the night sky and you see a super bright star is it super bright because it's a big bright star or is it super bright because it's just close by by the same token if you see a really dim star does that mean it's just really really far away and it's actually a big star that's super bright or it's actually just a small dim star we really had no way of knowing because again they had no idea how far away these objects were that they were measuring she was looking at this one part of the night sky this one cloud of stars she didn't know how far away that cloud was but she figured all the stars were about the same distance from her and she noticed that some of these stars were pulsating they were getting brighter and dimmer brighter and dimmer and they were doing it at a strangely consistent rate if one of the stars took four days to get brighter and it took four days to get dimmer and four days to get brighter it would stick to that pattern that period over and over again very reliable very consistent you may be wondering what does this have to do with mapping the night sky we're getting there so Henrietta decides to make a graph to start to plot every one of these stars that are pulsating and determine if there's any sort of pattern on one axis she put how long it took for the Stars cycles to go from bright to dim maybe it was two days maybe it was five days maybe it was ten days remember that each of these stars were showing a very consistent pattern of sticking to their cycle on the other axis she plotted how bright they were at each of these phases at their dimmest and at their brightest point so you've got brightness on this side and you've got how long it takes for this pulsating to happen on this one so let's say she sees a star she sees that it takes two days for it to go from dim to bright and then two more days to go from right to dim and then at its dhimmis point it's brightness value is down here and at its brightest point it's more like up here so this is what an entry would look like for one of these stars that she's observing she did this for a bunch of stars night after night and she started to see a pattern what this graph tells us is that stars that have a really long cycle going from dim to bright let's say they take like ten or twenty days to do that those stars are overall really bright they're probably big they have more energy whereas the opposite is true stars that pulsate really quickly that maybe just take a day or a half a day to go from dim to bright dim to bright those stars are actually overall much dimmer potentially small not actually as bright and intense as these stars that take a really long time to do their cycle so now if you look at the night sky and you see a really dim star let's say you don't know if it's dim because that's just a really small star or it's dim because it's really really really far away and it's actually a super bright star but it's just super far away from our perspective so it looks dim but now with Henrietta's formula you could look at the pulsating of that star and if it's pulsating really slow taking ten days to go from dim to bright and bright to dim then you can be sure that that's actually a really big bright star that just looks dim to us because we're super far away from it this gave astronomers a yardstick that they just didn't have before to observe and understand the distance to stars that were way way outside of the previous tools that we had to measure distance it took another swath of the cosmos and took them from 2d to 3d [Music] soon after Henrietta Leavitt discovered this amazing relationship a man by the name of Edwin Hubble famous astronomer decided that he wanted to use this to settle the grand debate on whether or not the galaxy was all there was to the universe he had been looking up at the sky and been seeing this kind of fuzzy cluster of stars that he didn't really understand was it close was it far away Hubble was able to pick out one of the stars in this cluster and look at how it pulsated using Henrietta's formula it became very clear to Hubble that this little fuzzy dot in the sky was very far away way outside of our galaxy this settled the debate about whether or not our galaxy was the entire universe or not that little fuzzy spot in the sky that Hubble was looking at turned out to be the end dromeda galaxy it was a groundbreaking discovery all made possible because Henrietta Leavitt formula and at the time Hubble estimated that it was probably around 700 thousand light years away we've since honed that estimate - more like 2.5 million light years away and now using the telescope that bears Hubble's name we've been able to observe that there aren't just a few galaxies outside of our own but billions okay that's it that's the answer to my question that's how I'm able to zoom around the solar system and the galaxy using this computer program the methods I talked about here are kind of the main building blocks of measuring distance in space we're continuing to push the bounds on this there are now methods for measuring the distance to all sorts of types of galaxies all sorts of types of distances and we continue to build out a map of the night sky in 3d and I'm really grateful for that honestly I'm grateful for the pioneers who put their minds to giving us perspective because it allows me to see where I live in the cosmos and what kind of space I occupy in the night sky and for some reason that perspective knowing where the stars are knowing how far away they are just kind of has engrained itself into my mind and allowed me to keep perspective as I live my day to day life anyway that's that thanks for watching also I want to thank Squarespace for sponsoring this video Squarespace is really easy to use place where you can build a website or a portfolio or an online presence of any kind I am currently rebuilding my portfolio and website using Squarespace I'm learning a ton about these features and how useful they are there are really easy to use beautiful templates that allow you to get a website up in minutes but then in addition to just like hosting and websites Squarespace gives you integration with all sorts of things that make running an online business easier and better like email marketing campaigns and of course integration with social media platforms all of the tools you need to build out a beautiful-looking online presence and to do it without a ton of work Squarespace is giving a discount to anyone who goes to my unique URL squarespace.com slash Johnny Harris it's in the description as well make sure to use that URL as it supports this channel if you do and if you do you get a free trial you can get everything set up and you'll get 10% off any purchase of a domain name or hosting space if you go to that URL so definitely go check out Squarespace thanks to Squarespace for sponsoring this video and thank you all for watching and looking forward to reading comments and hearing your thoughts on this stuff and I'm excited to make a new video soon have a good day

Channel: Johnny Harris

Views: 285,834

Rating: 4.952179 out of 5

Keywords: Johnny Harris, Johnny Harris Vox, Vox Borders, Johnny Harris Vox Borders, Vox

Id: JWpJjsou99c

Length: 15min 49sec (949 seconds)

Published: Thu Apr 30 2020

Reddit Comments

[u/YoungAmsterdam]

So I was a little annoyed that you don't actually learn how to calculate the distance to stars, you only are shown vague descriptions of the methods that were used.

For example, the basic graph that Henrietta created is shown to relate a star's time to cycle through light intensity fluctuations on the x-axis with the actual brightness values on the y-axis. But how do they use that to determine distances from Earth? He references an equation that was made, but he doesn't show any equation and doesn't provide any way of logically linking brightness values or cycle times to distances from Earth.

[u/Cynestrith]

I.love.this.guy.

Only discovered him and his wife recently, but they are delightful to watch.

[u/wnvyujlx]

here's a playlist you might enjoy: https://www.youtube.com/playlist?list=PLpH1IDQEoE8QWWTnWG5cK4ePCqg9W2608

[u/SteveS33]

I wish he explained WHY the brightness cycles like that. So brighter stars have longer brightness cycles. Doesn't explain why they cycle, or how that relates to absolute size. Unless I missed something

[u/PriestieBeast]

Uh, the parallax method! A genius made a bunch of assumptions, which mathematically seems untrue, but it works irl.

[u/[deleted]]

Great video, thank you.

[u/ilikebugs24]

Someone can refute me but I felt like watching this video was like falling asleep in math class and suddenly a bunch of formulas are on the board I never seen before.

I feel out of the loop around 4:30 minute mark. How did we find out what 1 UA is? Rather than just freely given information how determine the value of 1 AU? I vaguely remember from Trig how to calculate distance with given information but HOW was AU determined in the first place.

[u/azthek]

What's that guy from Chainsmokers doing teaching about stars?

[u/1zeewarburton]

Well don’t sound so chuffed, miserable goat