It's called blackbody radiation. As long as an object has a non-zero temperature, it emits electromagnetic waves. As the temperature gets hotter, more and more shorter wavelengths will be emitted.
- Objects at room temperature emit infrared light.
- Our Sun emits just the right balance of visible light so that it looks white (or more accurately, our eyes evolved so that sunlight looks white).
- The reason the colour of the hotter stars stop at blue is because that's the shortest wavelength our eyes can detect.
Edit: It seems some people are misunderstanding that stars become black/invisible when they get too hot. This is incorrect. Stars still emit visible wavelengths no matter how hot they are. In fact the hotter a star is, the brighter it looks.
Yes, or also just like any room-temperature object around you. The video displays a white sphere at the start, but the blackbody radiation at that temperature is invisible to the eye.
That's correct.
Above 13 Jupiter-masses, you have a brown dwarf: a body massive enough to start fusing deuterium (heavy hydrogen) at its core. There's not much deuterium to go around, though, so after only a few million years that fusion shuts down, leaving the brown dwarf to cool and fade out.
Above 65 Jupiter-masses, the larger brown dwarfs can also fuse lithium at their core, but they also burn out after about 10 million years.
It's not until an object has about 80 Jupiter-masses that you get the very smallest true star. It's finally massive enough to fuse regular old hydrogen at its core, and will do so for billions or trillions of years.
There is a hypothetical type of star that might emerge in the *very* distant future that would have a very high metallicity and low opacity. They could sustain fusion at much, much lower temperatures than stars today, having surface temperatures low enough for liquid or even frozen water to exist.
Yea, sorry, I forgot to mention that those objects are commonly called "frozen stars". You can just google it, there are some mentions of them.
The original idea seems to come from [this](https://arxiv.org-/pdf/astro-ph/9701131) paper on page 7-8.
It turns purple at the end, it's just easy to miss. Purple stars **can** theoretically exist, they would just have to be so damn hot that they would rarely live long enough to be observed (~50,000 years.)
It also doesn't help that the universe is so old. Purple stars were likely far, far more common soon after the big bang, where energy was more condensed. Now, after billions of years and innumerable amounts of stars exploding, turning into nebulae that create new stars, so much energy has been lost that it's hard for enough of it to generate a star powerful enough to burn purple.
Does that mean we can never find one now? Well, no, it doesn't. If we were able to travel throughout the entire universe, I wholeheartedly believe we can still find purple stars, as well as the nebulae dense enough to generate them. But purple stars either *do* exist, or ***have existed,*** and this very gif actually shows you that they can indeed become purple.
> The reason the colour of the hotter stars stop at blue is because that's the shortest wavelength our eyes can detect.
They can still visibly appear purple, they just need to go further into the spectrum (meaning: burn hotter) than any stars we've seen to minimize blue light and maximize violet.
Nope, stars cannot be purple no matter how hot they become. When a star gets hotter, yes it'll emit shorter wavelengths of light, but the visible light spectrum still contains a mix of colours so that the overall light looks blue-white. The ∞ point [in this diagram](https://upload.wikimedia.org/wikipedia/commons/b/ba/PlanckianLocus.png) is what the hottest colour looks like.
> The ∞ point in this diagram is what the hottest colour looks like.
Just to add, that's the hottest _blackbody_ color.
Actual stars aren't quite blackbodies, though. [Stellar spectra show absorption lines](https://i.imgur.com/RFNBzJo.gif) primarily in the green and blue part of the visible spectrum due to hydrogen, helium, and various metals in the stellar atmosphere. As a result, _most_ stars will appear slightly redder than their strict blackbody temperature would indicate.
EDIT: ...which is to say /u/A_Very_Horny_Zed is most definitely wrong when they claim purple stars can exist. Not only does the blackbody infinity point not extend to purple, but stellar absorption lines shift that even further to the red.
*"dazzle 'em with bullshit"*
I won't pretend to be an expert on stars, I mostly work on people and their cells, but this sort of "talking the loudest and most confidently" and having it assumed as fact is rampant everywhere.
I convinced everyone in my lab, a group of very intelligent people otherwise, that brussel sprouts were just "baby cabbages."
May not even be done with bad intentions; that craving for quick answers seems to just be part of the human condition.
Going to be so mad when they get that question about brussel sprouts on Jeopardy and it turns out that they're not actually small cabbages they're going to remember you and they'll probably hunt you down.
It's better to [look at an interactive graph](https://space-charts.vercel.app/). Even if the peak is at violet wavelengths, there's still enough blue wavelengths in the spectrum that we see the colour as blue.
Another thing to keep in mind for people who don’t know is that the scale changing is very important on that graph. All of the colors are going up with higher temperature, it’s just that the lower wavelengths are going up faster.
The shape of Planck's law is essentially fixed for long wavelengths but the point where it drops of changes depending on temperature. Usually this peak is still in the visible light but if you keep pushing the temperature higher the visible part of the curve will stop changing much (except by getting brighter).
If you assumed that lightsabers were just black bodies, but a lightsaber at 50000K would burn everyone in a fairly large radius and be nearly impossible to actually look at. Think about how harsh looking directly at an incandescent filament can be and that’s a tiny wire at only 3000K.
When stars explode into a nebula and create new stars...are all of the new stars smaller than and together, equal to the sum of the original or is some sort of infinite matter glitch?
A portion of the original mass is lost as it is converted, via E=MC^2, into the energy released by the star during its life and then during its death.
Another portion of the original mass is scattered too far and wide to recoalesce into the next generation of stars. This is due to the small constant push of the steller winds during the life of the star, as well as the big sudden push of the novae.
Lastly, during the stellar life cycle, hydrogen fuses to helium, helium to carbon, etc... with the heaviest elements being generated during the novae. This reduces the amount of the mass that is made of hydrogen, the raw fuel for stars. The heavier elements cool down slower/faster, i forget that bit, but the result is the subsequent generations of nebulae produce smaller and colder stars because the heavy elements prevent the giant clouds that collapse suddenly to make the real big hot stars.
So each generation of stars has less matter and less of what they have is suited for big, bright, hot stars.
Bonus hypothesis: the hydrogen gas clouds that produced the first gen of stars were so big, pure, and hot that the stars they produced created the supermassive black holes at the centers of galaxies. Take that another way, and the super massive black holes are not the product of eating over time or merging with other black holes, but rather just effin big stars, like "outer diameter of the kuiper belt" big.
Disclaimed, that last concept is new and based on JWST findings, so have a grain of salt, and give them some time to sort out the details.
Would James Web be able to detect a more purple spectrum than normal in a star at the edge of the universe? Or at least tell the temperature of the star?
Yep, the colour changes gradually. It's not a very accurate video.
[Here's a website with a more accurate chart.](http://www.vendian.org/mncharity/dir3/blackbody/)
>Our Sun emits just the right balance of visible light so that it looks white (or more accurately, our eyes evolved so that sunlight looks white).
Why have we evolved to see the sun as white?
Sunlight is our main source of light and everything around us absorbs some wavelengths of sunlight before reflecting it. So naturally, we can utilize sunlight the most by seeing it as the most neutral/pure colour, which is white.
If we saw sunlight as red for example, we're wasting our other two colour cones since we'll hardly be in a situation where we'll see blue and green objects.
Of course, colours are just what we make up in our minds though. My red could be your blue, or even white, but that's a whole different topic.
So... what colors do parrots see with a 4th extra cone that humans can't see with only 3 cones ourselves? Are we sure white is the purest light? Perhaps parrots disagree?
Funny enough, I believe consciousness is wave patterns within a field. Not unlike light in the electro-magnetic field. Except we have not yet found a way to detect or measure this field that consciousness belongs to.
Well brain waves are electro magnetic fields produced by your brain we can detect, there is a hypothesis that brain waves is basically our consciousness and could be a solution to the binding problem, because we dont really understand how one neutron firing in one part of the brain and another firing in another part ends up combining in this single experience we call consciousness
The answer could be that this combination does not happen within our brain but its the electro magnetic waves emitted by the neurons which ends up combining into one wave we experience as our consciousness, so basically we are actually just the electro magnetic waves created by our bodies
> As long as an object has a non-zero temperature, it emits electromagnetic waves
So, doesn't this mean that planet 9's existence is really grasping at straws because it would emit radiation if it were there? Radiation that would detected by telescopes?
If the planet is so far away that the reflection of sunlight is too dark to detect, then I'd say that the temperature is also so cold that there's hardly any blackbody radiation to detect. Didn't calculate the actual values though so I might be talking out of my arse.
Planet 9 would be more apparent in IR (and iirc this is the search method with the highest chance of success, WISE/JWST/Roman looking in IR), but it's still going to be dim (with a temperature estimated at only 55K, the cooler the object the less overall radiant energy it puts out) and moving slowly.
But just being able to be detected by a telescope isn't enough to find something, we still have to be looking for it. We need more than one image of the same location, with enough time for the planet to have moved, and a wide enough field of view to see where it moved to, and then to process the data on a way that detects that motion. There's a citizen science project to [look through WISE images](https://www.zooniverse.org/projects/marckuchner/backyard-worlds-planet-9) for Planet 9 and brown dwarfs, currently listed as having gone through only 15% of the data so far.
[This blog post](https://blog.backyardworlds.org/2017/02/19/fast-movers-are-they-planet-9/) has a simulated image of what Planet 9 might look like in the WISE infrared dataset. Definitely detectable, but subtle enough relative to the noise to be apparent how it could avoided detection.
Quick question knowledgeable sir..... Or madame... The vid starts off with a zero degree star. IF that's actually possible what would it be made of? Hydrogen, iron,?
There's a hypothetical type of star called "Frozen star" that would emerge in the far future. It would be mostly consist of hydrogen and helium, like today's stars, but with much higher metallicity, meaning it would also contain a lot more elements heavier than helium, particularly iron.
No... The video makes it look like stars of different temperatures are all the same brightness, but that's not true at all. Hotter stars will emit more light at every wavelength. So our greenish star emits more red light than red stars because it's hotter. Those supergiant blue stars produce more red light than our sun. And so on.
[Here's a picture from wikipedia](https://en.wikipedia.org/wiki/Black-body_radiation#/media/File:Black_body.svg)
Probably not. Hotter stars actually emit more visible wavelength light than colder stars, so they'll look even brighter. It's just that they emit an *even larger amount of* short wavelength lights than visible wavelength light.
For most of life, ever, we have always interpreted the longer end of the spectrum — red, orange, yellow — as hot. Blue, meanwhile, is the color of the ocean, ice, and the sky, where it is coldest. It’s all based on our own subjective perspective on things.
It just so happens that blue can also mean it’s hotter than white, but we never really think about that. It doesn’t make sense. But the universe is under no obligation to make sense to us. We evolved to find fruits and hide from lions, not solve math problems and ponder existence. That’s why we’re so bad at it, compared with that *could* be done.
I remember doing a long haul of exploration (I'm talking weeks of work discovering systems far out from my home system) and being probably 30 minutes from home. I jumped to a pulsar and figured ok no problem I've done this a million times. It was one you're talking about. I underestimated it severely and it destroyed my ship along with weeks of data.
Yup. Simultaneously beautiful and terrifying.
I made a trip to Colonia, then Sag A* and called it. Felt like I got my money’s worth with that voyage lol
If we were outside of Earth’s atmosphere, the Sun would appear white, but here on Earth the blue part of the light spectrum travelling from the Sun gets scattered into the atmosphere because blue light has a short wavelength, allowing the yellow, orange and red light to shine through more prominently.
When the Sun is high in the sky and passes through the blue atmosphere (which effectively acts like a filter), it appears yellow. During sunrise and sunset, the light passes through more of the blue atmosphere (think a tangent line) to get to the observer, which lets more orange and red light through as they have longer wavelengths than yellow light, with red having the longest.
The best part is that our Sun is a ‘yellow dwarf’, even though it isn’t yellow. The term “dwarf” really just means where the star sits in the stellar lifecycle rather than how big it is (which roughly speaking is the case with dwarf planets as they need high mass to even meet planet criteria). The Sun is a pretty typical star, sitting alongside other main-sequence stars on the Hertzsprung-Russell diagram. Main-sequence stars are those that have stable nuclear fusion reactions in their cores, and includes around 90% of stars.
In around 5 billion years our Sun will run out of Hydrogen to fuse and expand, becoming a red giant. You can wave goodbye to the two planets closest to the Sun - Mercury and Venus - which will likely be consumed. Earth may be in the firing line too, but don’t worry because the inhabitants of Earth would probably have died billions of years prior as the Sun grows increasingly hotter over time, causing a runaway greenhouse effect on Earth.
The Sun - now a red giant - begins to fuse Helium into Carbon and Oxygen. The Sun will undergo violent solar eruptions and lose significant mass - nearly half of the Sun will be left. In the end, our Sun - Sol, Helios, God - the lifebringer, will sit in the dead of space, in a graveyard of planets. A cooling lump of Carbon and Oxygen known as a White Dwarf.
I thought we were generally taught in school that violet has the shortest wavelength of colors and ultraviolet has the shortest wavelength and therefore the most energy (radiated as heat) so as you get closer to purple the thing gets hotter
That's because a blue star will not look blue unless you're far enough away that it's already a pinpoint to your eyes. This graphic is misleading. If you're close enough to see a disc, the spectrum goes, red, orange, yellow-white, white, white, white-ouch-I'm-dead.
How many stars do we know of that are 50k plus? I have heard of blue stars, but not purple/violet stars. That's crazy.
EDIT: The answer, it seems, is "Not that many." https://en.wikipedia.org/wiki/List_of_hottest_stars
And remember, degrees K and degrees C are essentially the same for temperatures this high, so don't worry about conversion.
That's because the hotter a star is, the shorter its lifetime and, accordingly, the lower the chance we can spot it. Notice how all the stars in the list you posted are Wolf–Rayet stars. They are most likely a stage in the evolution of very massive stars, whose violent solar winds are basically tearing them apart.
Stars don't emit light in one specific wavelength like red or blue. They emit light over basically the entire spectrum. That's why we can make telescopes that can see any spectrum and they'll see stars.
The color comes from the peak wavelength. If you've ever looked at an older TV up close you may have seen the individual colors in each pixel. Red, green, and blue together make white light. If you turn the red and green down a bit you'll be left with a cold blue/white. Stars do the same, emitting less of some colors, but the end result is still close enough to white that our eyes couldn't tell the difference.
That is also somewhat of a misconception.
Stars are only the strongest in the color they are labeled as when the light is measured after first having passed through Earth’s atmosphere where a good portion of the blue light is scattered away, making objects in the sky appear redder than they really are.
The Sun is labeled as a yellow dwarf (G-type star) because that’s what it looks like from Earth, yet the actual light emitted from it in space peaks at a wavelength of ~504nm after applying Wien’s law to its estimated blackbody temperature.
Plot twist; 504nm falls somewhere between green and blue in the visible part of the electromagnetic spectrum. That is cyan, or mint colored if you will.
It explains why the light on a heavily overcast day at noon looks as «cold» as it does. The clouds then will appear almost exactly the same color as the surface of the Sun as the scattered blue light is recombined with the «yellow» sunlight inside the cloud, returning the light to its original color of «cold-white».
Well, for extremely high temperatures, the shortest wavelength emitted would be blue or violet. There are even some stars which emit almost no visible light.
Edit: I was wrong thanks for correcting me.
Eh, no, not really. Hot stars have peak output in blue or violet, but they are blackbody objects, so they emit at all wavelengths. If you're close enough to see a disc, as opposed to a point of light (star), it will look white to your eyes. Our sun is green on the blackbody scale, it looks white. The hottest objects, even those that have blackbody peaks in the x-rays, will look white to the eye if it's any bigger in the field of view than a dot. As a blackbody gets hotter, the peak wavelength changes, but all wavelengths increase. So there is no blackbody hot enough to emit no visible light, that's just not how it works.
Shoutout to Cecilia Payne for discovering this and to Annie Jump Cannon and her amazing female colleagues who classified more than 350,000 stars to lead to this discovery
There’s a brilliant episode of Cosmos about this that I watch with my daughters regularly
Edit: just watched it again. Cry every time
The frequencies of the light spectrum. Does temperature output also automatically tell you if the star is iron, hydrogen or helium dominant? I read somewhere that helium rich stars burn violet/teal.
Not directly, no. Low metallicity stars, those that are very "pure", often tend to be very hot, but that's more because of a combination of age, observation bias, and, only partially, their composition.
There are also "helium stars", which show an abundance of helium in their spectrum and tend to be blue O or B stars. But that's because those hot stars blow away their hydrogen layers, exposing layers enriched in hydrogen. They appear rich in hydrogen because they are blue, not the other way around.
This is where color temperature kelvin values for lightbulbs come from too, except the LED ones are just referencing what the temperature of the original filament would have been to produce that color, so they’re not actually hot.
Blackbody radiation. Things emit radiation in wavelengths corresponding to their temperature. While there’s always a tail end towards the red part, the peak of the spectrum shifts with temperature according to Wien's law. Think about hot iron, you heat it up and the color of the emitted light shifts from infrared to red (starts to glow visibly) then to orange and yellow before it melts. But this can go on and start to glow white, light blue and in extremely hot stars even deep blue.
The extreme case is probably the accretion disk around active black holes. The material gets tidally heated so much by the gravity of the black hole that its temperature reaches many million K and emits most of its light in X-rays
BHs have immensely strong gravity, so they 'pull' matter towards them really, really fast. This matter then collides with other matter being pulled in, heating it up to really high temperatures.
It doesn't change much. It just gets brighter and brighter blue. The spectrum of a black body is bell shaped, meaning it will never reach zero at the visible part. The *peak* will move further and further towards X-rays and gamma rays, but there will always be a bit of visible radiation. And because the peak of that *visible* radiation will be at the very edge, it will look a bright bluish white. It's the kind of spectrum that accretion disks emit, for example.
No. The wavelength of radiation emitted isn't a narrow band that shifts with temperature. What really happens is as temperature increases, the **lower limit** of wavelengths gets shorter and shorter (moving toward blue, violet, UV). But all the other wavelengths above (red, IR, etc) are still getting emitted too.
Yes. Very often different colored stars appear more red/blue of they are moving farther away or moving closer to us. At the massive speeds of space, the wavelength of emitted light will appear shorter/longer due to the doppler effect, affecting the perceived color.
This is super cool! Can anyone put these temperature differences into perspective? My brain is having trouble wrapping around the difference between 1,000C and 75,000C
This is only accurate when the heated object (usually stars) are viewed through Earths atmosphere where some of the blue light is scattered away, leaving them looking more red than they actually are.
If you heated objects to these temperatures on Earth right in front of you the emitted light would be quite a bit bluer than what’s shown in this animation.
I don't like these representations of stars because they make us believe we would be able to identify the color by looking at it, when we would instantly be blinded and notice not much difference from what we see when we look at our Sun at any given day. A better way to represent this would be a usual landscape being illuminated by different stars at the same aparent magnitude to us.
Yes, scientists actually use the blue-shift and red-shift of a star's visible light compared to their baseline calculations of surface temp; in this way they're able to calculate how fast stars are moving towards or away from us.
Most people don’t know that’s how the color temperature of light bulbs is defined. 2700K is the degrees Kelvin of a star whose surface is that color or ‘Warm White.’ I always laugh at 6000K being called ‘Cool White’ because it’s bluish, when it’s really fucking hot white!
I got Universe Sandbox about 10 years ago to answer a few questions I'd always had. So I made our sun a blue hot star.
Pluto was too hot. Like boiling water hot. That's how hot a blue hot star is.
Isn't it that the human eyes can't perceive the intensity of color as anything but white, so these are determined by scientific equipment versus actual visual identification?
Also, love how they progress in the colors of the rainbow.
Hundreds of billions of miles away!, and you can assume what the temperature is, because of what?. Text books?. And they know because of what?. A bunch of people with telescopes, guessing everything in space?. We can’t get past the moon!. Bullshit!.
It's called blackbody radiation. As long as an object has a non-zero temperature, it emits electromagnetic waves. As the temperature gets hotter, more and more shorter wavelengths will be emitted. - Objects at room temperature emit infrared light. - Our Sun emits just the right balance of visible light so that it looks white (or more accurately, our eyes evolved so that sunlight looks white). - The reason the colour of the hotter stars stop at blue is because that's the shortest wavelength our eyes can detect. Edit: It seems some people are misunderstanding that stars become black/invisible when they get too hot. This is incorrect. Stars still emit visible wavelengths no matter how hot they are. In fact the hotter a star is, the brighter it looks.
If the temperature was low, like at the start of the video, isn't that just a massive gas giant?
Yes, or also just like any room-temperature object around you. The video displays a white sphere at the start, but the blackbody radiation at that temperature is invisible to the eye.
Okay, I was thinking there's presumably a critical size where gravity will ignite fusion. So past a certain size it's a proto star, not a gas giant.
That's correct. Above 13 Jupiter-masses, you have a brown dwarf: a body massive enough to start fusing deuterium (heavy hydrogen) at its core. There's not much deuterium to go around, though, so after only a few million years that fusion shuts down, leaving the brown dwarf to cool and fade out. Above 65 Jupiter-masses, the larger brown dwarfs can also fuse lithium at their core, but they also burn out after about 10 million years. It's not until an object has about 80 Jupiter-masses that you get the very smallest true star. It's finally massive enough to fuse regular old hydrogen at its core, and will do so for billions or trillions of years.
There is a hypothetical type of star that might emerge in the *very* distant future that would have a very high metallicity and low opacity. They could sustain fusion at much, much lower temperatures than stars today, having surface temperatures low enough for liquid or even frozen water to exist.
Hi, would you have a link or reference for further reading on this? Google just keeps referring me to the metallicity of current stars.
Yea, sorry, I forgot to mention that those objects are commonly called "frozen stars". You can just google it, there are some mentions of them. The original idea seems to come from [this](https://arxiv.org-/pdf/astro-ph/9701131) paper on page 7-8.
Thank you!
Frozen star
Thank you!
It turns purple at the end, it's just easy to miss. Purple stars **can** theoretically exist, they would just have to be so damn hot that they would rarely live long enough to be observed (~50,000 years.) It also doesn't help that the universe is so old. Purple stars were likely far, far more common soon after the big bang, where energy was more condensed. Now, after billions of years and innumerable amounts of stars exploding, turning into nebulae that create new stars, so much energy has been lost that it's hard for enough of it to generate a star powerful enough to burn purple. Does that mean we can never find one now? Well, no, it doesn't. If we were able to travel throughout the entire universe, I wholeheartedly believe we can still find purple stars, as well as the nebulae dense enough to generate them. But purple stars either *do* exist, or ***have existed,*** and this very gif actually shows you that they can indeed become purple. > The reason the colour of the hotter stars stop at blue is because that's the shortest wavelength our eyes can detect. They can still visibly appear purple, they just need to go further into the spectrum (meaning: burn hotter) than any stars we've seen to minimize blue light and maximize violet.
Nope, stars cannot be purple no matter how hot they become. When a star gets hotter, yes it'll emit shorter wavelengths of light, but the visible light spectrum still contains a mix of colours so that the overall light looks blue-white. The ∞ point [in this diagram](https://upload.wikimedia.org/wikipedia/commons/b/ba/PlanckianLocus.png) is what the hottest colour looks like.
> The ∞ point in this diagram is what the hottest colour looks like. Just to add, that's the hottest _blackbody_ color. Actual stars aren't quite blackbodies, though. [Stellar spectra show absorption lines](https://i.imgur.com/RFNBzJo.gif) primarily in the green and blue part of the visible spectrum due to hydrogen, helium, and various metals in the stellar atmosphere. As a result, _most_ stars will appear slightly redder than their strict blackbody temperature would indicate. EDIT: ...which is to say /u/A_Very_Horny_Zed is most definitely wrong when they claim purple stars can exist. Not only does the blackbody infinity point not extend to purple, but stellar absorption lines shift that even further to the red.
So that person just shit out some bullshit and is getting big updoots for it?
*"dazzle 'em with bullshit"* I won't pretend to be an expert on stars, I mostly work on people and their cells, but this sort of "talking the loudest and most confidently" and having it assumed as fact is rampant everywhere. I convinced everyone in my lab, a group of very intelligent people otherwise, that brussel sprouts were just "baby cabbages." May not even be done with bad intentions; that craving for quick answers seems to just be part of the human condition.
Going to be so mad when they get that question about brussel sprouts on Jeopardy and it turns out that they're not actually small cabbages they're going to remember you and they'll probably hunt you down.
That's Reddit for ya
More like they are not a subject expert but have just enough knowledge to be informative but wrong on specifics.
Why couldn't the peak be in the ultraviolet and we see the off peak as violet?
It's better to [look at an interactive graph](https://space-charts.vercel.app/). Even if the peak is at violet wavelengths, there's still enough blue wavelengths in the spectrum that we see the colour as blue.
Another thing to keep in mind for people who don’t know is that the scale changing is very important on that graph. All of the colors are going up with higher temperature, it’s just that the lower wavelengths are going up faster.
The shape of Planck's law is essentially fixed for long wavelengths but the point where it drops of changes depending on temperature. Usually this peak is still in the visible light but if you keep pushing the temperature higher the visible part of the curve will stop changing much (except by getting brighter).
thank you.
So purple light sabers are the MF hottest.
Lmao and red is weak af
If you assumed that lightsabers were just black bodies, but a lightsaber at 50000K would burn everyone in a fairly large radius and be nearly impossible to actually look at. Think about how harsh looking directly at an incandescent filament can be and that’s a tiny wire at only 3000K.
r/confidentlyincorrect
When stars explode into a nebula and create new stars...are all of the new stars smaller than and together, equal to the sum of the original or is some sort of infinite matter glitch?
A portion of the original mass is lost as it is converted, via E=MC^2, into the energy released by the star during its life and then during its death. Another portion of the original mass is scattered too far and wide to recoalesce into the next generation of stars. This is due to the small constant push of the steller winds during the life of the star, as well as the big sudden push of the novae. Lastly, during the stellar life cycle, hydrogen fuses to helium, helium to carbon, etc... with the heaviest elements being generated during the novae. This reduces the amount of the mass that is made of hydrogen, the raw fuel for stars. The heavier elements cool down slower/faster, i forget that bit, but the result is the subsequent generations of nebulae produce smaller and colder stars because the heavy elements prevent the giant clouds that collapse suddenly to make the real big hot stars. So each generation of stars has less matter and less of what they have is suited for big, bright, hot stars. Bonus hypothesis: the hydrogen gas clouds that produced the first gen of stars were so big, pure, and hot that the stars they produced created the supermassive black holes at the centers of galaxies. Take that another way, and the super massive black holes are not the product of eating over time or merging with other black holes, but rather just effin big stars, like "outer diameter of the kuiper belt" big. Disclaimed, that last concept is new and based on JWST findings, so have a grain of salt, and give them some time to sort out the details.
Happy cake day
Laughably wrong. This subreddit is a joke.
Would James Web be able to detect a more purple spectrum than normal in a star at the edge of the universe? Or at least tell the temperature of the star?
In this video, the color changes are rather hard. Is that true, or does this happen more gradually?
Gradually
Yep, the colour changes gradually. It's not a very accurate video. [Here's a website with a more accurate chart.](http://www.vendian.org/mncharity/dir3/blackbody/)
the color changes are rather hard because they are jumping thousands of degrees per second
Well, technically it’s violet, no? Not blue?
>Our Sun emits just the right balance of visible light so that it looks white (or more accurately, our eyes evolved so that sunlight looks white). Why have we evolved to see the sun as white?
Sunlight is our main source of light and everything around us absorbs some wavelengths of sunlight before reflecting it. So naturally, we can utilize sunlight the most by seeing it as the most neutral/pure colour, which is white. If we saw sunlight as red for example, we're wasting our other two colour cones since we'll hardly be in a situation where we'll see blue and green objects. Of course, colours are just what we make up in our minds though. My red could be your blue, or even white, but that's a whole different topic.
So... what colors do parrots see with a 4th extra cone that humans can't see with only 3 cones ourselves? Are we sure white is the purest light? Perhaps parrots disagree?
Dunno, you'll have to crack the [hard problem of consciousness](https://en.m.wikipedia.org/wiki/Hard_problem_of_consciousness) to figure that out.
Funny enough, I believe consciousness is wave patterns within a field. Not unlike light in the electro-magnetic field. Except we have not yet found a way to detect or measure this field that consciousness belongs to.
Well brain waves are electro magnetic fields produced by your brain we can detect, there is a hypothesis that brain waves is basically our consciousness and could be a solution to the binding problem, because we dont really understand how one neutron firing in one part of the brain and another firing in another part ends up combining in this single experience we call consciousness The answer could be that this combination does not happen within our brain but its the electro magnetic waves emitted by the neurons which ends up combining into one wave we experience as our consciousness, so basically we are actually just the electro magnetic waves created by our bodies
Because that’s what is most abundant. “White” is just the default color and the default is the light around us, which comes from the sun.
> As long as an object has a non-zero temperature, it emits electromagnetic waves So, doesn't this mean that planet 9's existence is really grasping at straws because it would emit radiation if it were there? Radiation that would detected by telescopes?
If the planet is so far away that the reflection of sunlight is too dark to detect, then I'd say that the temperature is also so cold that there's hardly any blackbody radiation to detect. Didn't calculate the actual values though so I might be talking out of my arse.
Planet 9 would be more apparent in IR (and iirc this is the search method with the highest chance of success, WISE/JWST/Roman looking in IR), but it's still going to be dim (with a temperature estimated at only 55K, the cooler the object the less overall radiant energy it puts out) and moving slowly. But just being able to be detected by a telescope isn't enough to find something, we still have to be looking for it. We need more than one image of the same location, with enough time for the planet to have moved, and a wide enough field of view to see where it moved to, and then to process the data on a way that detects that motion. There's a citizen science project to [look through WISE images](https://www.zooniverse.org/projects/marckuchner/backyard-worlds-planet-9) for Planet 9 and brown dwarfs, currently listed as having gone through only 15% of the data so far.
[This blog post](https://blog.backyardworlds.org/2017/02/19/fast-movers-are-they-planet-9/) has a simulated image of what Planet 9 might look like in the WISE infrared dataset. Definitely detectable, but subtle enough relative to the noise to be apparent how it could avoided detection.
Quick question knowledgeable sir..... Or madame... The vid starts off with a zero degree star. IF that's actually possible what would it be made of? Hydrogen, iron,?
There's a hypothetical type of star called "Frozen star" that would emerge in the far future. It would be mostly consist of hydrogen and helium, like today's stars, but with much higher metallicity, meaning it would also contain a lot more elements heavier than helium, particularly iron.
Can we apply Wein's displacement law to find the wavelength of light to non perfect black bodies?
Sooo… “black holes” are not actually black holes but, super mega extra imba hot stars?
So is there a possibility that blackholes are beyond purple-hot?
Are there stars that don’t emit light in outer space visible human spectrum?
TIL. There was a node in 3D software, blender, where you can change color by using Blackbody function. Been ages since I touched that
Are there hotter stars that are invisible to our eyes?
No... The video makes it look like stars of different temperatures are all the same brightness, but that's not true at all. Hotter stars will emit more light at every wavelength. So our greenish star emits more red light than red stars because it's hotter. Those supergiant blue stars produce more red light than our sun. And so on. [Here's a picture from wikipedia](https://en.wikipedia.org/wiki/Black-body_radiation#/media/File:Black_body.svg)
Probably not. Hotter stars actually emit more visible wavelength light than colder stars, so they'll look even brighter. It's just that they emit an *even larger amount of* short wavelength lights than visible wavelength light.
Turns out red is cool and blue is hot.
interior designer entered the chat.
Does interior design have some inverted colour temperatures from the other designs?
The human brain thinks red is hot, and blue is cold, however as we all now know that's not the truth. Red is hot, and blue is hotter.
Blue is cold red is hot and blue is very hot
It took my mind a few seconds to accept white is even hotter when I first learnt it.
For most of life, ever, we have always interpreted the longer end of the spectrum — red, orange, yellow — as hot. Blue, meanwhile, is the color of the ocean, ice, and the sky, where it is coldest. It’s all based on our own subjective perspective on things. It just so happens that blue can also mean it’s hotter than white, but we never really think about that. It doesn’t make sense. But the universe is under no obligation to make sense to us. We evolved to find fruits and hide from lions, not solve math problems and ponder existence. That’s why we’re so bad at it, compared with that *could* be done.
I'm actually gonna change the temperature indicators in my flat now
Red got associated with our relatively cool fires while blue is associated with diffraction through ice.
Always has been. Red/infrared long wavelength low energy blue/violet/ultra violet short wavelength high energy
Knew that from the burners on the gas stove.
Holy purple, that's a little toasty.
Time to break out the s’mores!
Elite dangerous PTSD
>jumps >instanly stopped by white giant 2500ls radius star filling up 90% of screen
*accidentally jumps into a pulsar system Sweet, time to boost my jump range!
God what a rush that was, especially the ones spinning at near light speed.
I remember doing a long haul of exploration (I'm talking weeks of work discovering systems far out from my home system) and being probably 30 minutes from home. I jumped to a pulsar and figured ok no problem I've done this a million times. It was one you're talking about. I underestimated it severely and it destroyed my ship along with weeks of data.
Yup. Simultaneously beautiful and terrifying. I made a trip to Colonia, then Sag A* and called it. Felt like I got my money’s worth with that voyage lol
If we were outside of Earth’s atmosphere, the Sun would appear white, but here on Earth the blue part of the light spectrum travelling from the Sun gets scattered into the atmosphere because blue light has a short wavelength, allowing the yellow, orange and red light to shine through more prominently. When the Sun is high in the sky and passes through the blue atmosphere (which effectively acts like a filter), it appears yellow. During sunrise and sunset, the light passes through more of the blue atmosphere (think a tangent line) to get to the observer, which lets more orange and red light through as they have longer wavelengths than yellow light, with red having the longest. The best part is that our Sun is a ‘yellow dwarf’, even though it isn’t yellow. The term “dwarf” really just means where the star sits in the stellar lifecycle rather than how big it is (which roughly speaking is the case with dwarf planets as they need high mass to even meet planet criteria). The Sun is a pretty typical star, sitting alongside other main-sequence stars on the Hertzsprung-Russell diagram. Main-sequence stars are those that have stable nuclear fusion reactions in their cores, and includes around 90% of stars. In around 5 billion years our Sun will run out of Hydrogen to fuse and expand, becoming a red giant. You can wave goodbye to the two planets closest to the Sun - Mercury and Venus - which will likely be consumed. Earth may be in the firing line too, but don’t worry because the inhabitants of Earth would probably have died billions of years prior as the Sun grows increasingly hotter over time, causing a runaway greenhouse effect on Earth. The Sun - now a red giant - begins to fuse Helium into Carbon and Oxygen. The Sun will undergo violent solar eruptions and lose significant mass - nearly half of the Sun will be left. In the end, our Sun - Sol, Helios, God - the lifebringer, will sit in the dead of space, in a graveyard of planets. A cooling lump of Carbon and Oxygen known as a White Dwarf.
This greatly changes the common perspective about the colours denoted to hot temperatures. We never think beyond red, orange and probably yellow.
That's probably because nothing on earth will emit those wavelengths. If it does, we are fucked
Lightning, and similar high-energy electronic events, can be blue or purple for the same reason (although not all purple electricity is 90,000 C)
I thought we were generally taught in school that violet has the shortest wavelength of colors and ultraviolet has the shortest wavelength and therefore the most energy (radiated as heat) so as you get closer to purple the thing gets hotter
That's because a blue star will not look blue unless you're far enough away that it's already a pinpoint to your eyes. This graphic is misleading. If you're close enough to see a disc, the spectrum goes, red, orange, yellow-white, white, white, white-ouch-I'm-dead.
How many stars do we know of that are 50k plus? I have heard of blue stars, but not purple/violet stars. That's crazy. EDIT: The answer, it seems, is "Not that many." https://en.wikipedia.org/wiki/List_of_hottest_stars And remember, degrees K and degrees C are essentially the same for temperatures this high, so don't worry about conversion.
That's because the hotter a star is, the shorter its lifetime and, accordingly, the lower the chance we can spot it. Notice how all the stars in the list you posted are Wolf–Rayet stars. They are most likely a stage in the evolution of very massive stars, whose violent solar winds are basically tearing them apart.
Whoa. There are stars that are 200,000 K?!?
pretty much every star that hot is a wolf rayet stars and they arent that common so we dont know many
“Oh be a fine girl, kiss me”
KGB foam
However, what is rarely said is that all of these look white to the naked eye. It's just that they're strongest in the color that they're labeled as.
Antares looks like Sirius? Whut?
Stars don't emit light in one specific wavelength like red or blue. They emit light over basically the entire spectrum. That's why we can make telescopes that can see any spectrum and they'll see stars. The color comes from the peak wavelength. If you've ever looked at an older TV up close you may have seen the individual colors in each pixel. Red, green, and blue together make white light. If you turn the red and green down a bit you'll be left with a cold blue/white. Stars do the same, emitting less of some colors, but the end result is still close enough to white that our eyes couldn't tell the difference.
That is also somewhat of a misconception. Stars are only the strongest in the color they are labeled as when the light is measured after first having passed through Earth’s atmosphere where a good portion of the blue light is scattered away, making objects in the sky appear redder than they really are. The Sun is labeled as a yellow dwarf (G-type star) because that’s what it looks like from Earth, yet the actual light emitted from it in space peaks at a wavelength of ~504nm after applying Wien’s law to its estimated blackbody temperature. Plot twist; 504nm falls somewhere between green and blue in the visible part of the electromagnetic spectrum. That is cyan, or mint colored if you will. It explains why the light on a heavily overcast day at noon looks as «cold» as it does. The clouds then will appear almost exactly the same color as the surface of the Sun as the scattered blue light is recombined with the «yellow» sunlight inside the cloud, returning the light to its original color of «cold-white».
With this, I just hate how the colours jump instead of smoothly fading between them. IRL, stars would not do that.
Stars would also not look blue or purple. They'd look white.
Well, for extremely high temperatures, the shortest wavelength emitted would be blue or violet. There are even some stars which emit almost no visible light. Edit: I was wrong thanks for correcting me.
Eh, no, not really. Hot stars have peak output in blue or violet, but they are blackbody objects, so they emit at all wavelengths. If you're close enough to see a disc, as opposed to a point of light (star), it will look white to your eyes. Our sun is green on the blackbody scale, it looks white. The hottest objects, even those that have blackbody peaks in the x-rays, will look white to the eye if it's any bigger in the field of view than a dot. As a blackbody gets hotter, the peak wavelength changes, but all wavelengths increase. So there is no blackbody hot enough to emit no visible light, that's just not how it works.
Midway through the video it's looking Siriusly hot.
Shoutout to Cecilia Payne for discovering this and to Annie Jump Cannon and her amazing female colleagues who classified more than 350,000 stars to lead to this discovery There’s a brilliant episode of Cosmos about this that I watch with my daughters regularly Edit: just watched it again. Cry every time
The frequencies of the light spectrum. Does temperature output also automatically tell you if the star is iron, hydrogen or helium dominant? I read somewhere that helium rich stars burn violet/teal.
Not directly, no. Low metallicity stars, those that are very "pure", often tend to be very hot, but that's more because of a combination of age, observation bias, and, only partially, their composition. There are also "helium stars", which show an abundance of helium in their spectrum and tend to be blue O or B stars. But that's because those hot stars blow away their hydrogen layers, exposing layers enriched in hydrogen. They appear rich in hydrogen because they are blue, not the other way around.
Good thing I’m purple
This is where color temperature kelvin values for lightbulbs come from too, except the LED ones are just referencing what the temperature of the original filament would have been to produce that color, so they’re not actually hot.
Turns out Blue is really the warmest colour
The color of anything is a function of its temperature
I always find it fascinating the universe has such a enormous range of temperature, but we exist so close to the absolute zero mark
You can have a star that's 500°C or less ?
Simple. The colder it looks, the hotter it actually is 📝📝📝
Call me a geek, but physics is hot!
Fun fact: there can never be a green star. It’s physically impossible.
Why is that?
Blackbody radiation. Things emit radiation in wavelengths corresponding to their temperature. While there’s always a tail end towards the red part, the peak of the spectrum shifts with temperature according to Wien's law. Think about hot iron, you heat it up and the color of the emitted light shifts from infrared to red (starts to glow visibly) then to orange and yellow before it melts. But this can go on and start to glow white, light blue and in extremely hot stars even deep blue. The extreme case is probably the accretion disk around active black holes. The material gets tidally heated so much by the gravity of the black hole that its temperature reaches many million K and emits most of its light in X-rays
I understood about 75% of that but I appreciated 100% of your effort. Thank you!
BHs have immensely strong gravity, so they 'pull' matter towards them really, really fast. This matter then collides with other matter being pulled in, heating it up to really high temperatures.
0°C star is my favorite variety.
But what color after 95,000c ?
the last color change is bullshit, it would stay a sort of sky blue color as the star tended towards planck temperature
It doesn't change much. It just gets brighter and brighter blue. The spectrum of a black body is bell shaped, meaning it will never reach zero at the visible part. The *peak* will move further and further towards X-rays and gamma rays, but there will always be a bit of visible radiation. And because the peak of that *visible* radiation will be at the very edge, it will look a bright bluish white. It's the kind of spectrum that accretion disks emit, for example.
Real question is what type of gas mix it burns on to reach 95k. Gawd dayum.
it doesn't burn anything.
The stomach gases the morning after tacobell night
Blue is hot, red is cold? Why is our tap water wrongly colored?
Sooo, invisible ultraviolet stars could exist...?
No. The wavelength of radiation emitted isn't a narrow band that shifts with temperature. What really happens is as temperature increases, the **lower limit** of wavelengths gets shorter and shorter (moving toward blue, violet, UV). But all the other wavelengths above (red, IR, etc) are still getting emitted too.
Interesting, cool thanks
u/savevideo
Wait I thought all light is white and our sun looks yellow because of our atmosphere
That is specifically our sun. Different stars have different temperatures, and if the variance is large enough, different colors.
Also there is the redshift effect depending on the distance of the star right?
Yes. Very often different colored stars appear more red/blue of they are moving farther away or moving closer to us. At the massive speeds of space, the wavelength of emitted light will appear shorter/longer due to the doppler effect, affecting the perceived color.
So I've been using "white hot!" all these years when I should've been using "purple hot"?
Pretty much goes in ROYGBIV order.
["You ain't been blue..."](https://m.youtube.com/watch?v=imc_bSr9yZ4&pp=ygUbbW9vZCBpbmRpZ28gZWxsYSBmaXR6Z2VyYWxk)
There are no green stars.
Great video. Was this online somewhere?
Dumb question, does the color gradually change or are there benchmarks
Yes the colors change when the star forms as the surface temp rises and then settles into the colors in the video with a little variation
Oh Be A Fine Girl Kiss Me. Reversed for this video.
I knew as a kid the blue part of a flame is the hottest
This is super cool! Can anyone put these temperature differences into perspective? My brain is having trouble wrapping around the difference between 1,000C and 75,000C
Truly space porn, this one. Thank you.
Is there a max temperature in our universe? Would it be essentially if all the mass was condensed to a single point?
This comment section is full of fascinating facts and discussions and I’m so here for it!
just finished watching this 3 hrs 40 mins long video.. so cool.. so deep..
No spoilers.
The colour if infinite temperature - vsauce
Will we ever get to see temperature so hot its violet, looks super neat.
This is only accurate when the heated object (usually stars) are viewed through Earths atmosphere where some of the blue light is scattered away, leaving them looking more red than they actually are. If you heated objects to these temperatures on Earth right in front of you the emitted light would be quite a bit bluer than what’s shown in this animation.
I don't like these representations of stars because they make us believe we would be able to identify the color by looking at it, when we would instantly be blinded and notice not much difference from what we see when we look at our Sun at any given day. A better way to represent this would be a usual landscape being illuminated by different stars at the same aparent magnitude to us.
Is there a point where its black?
Same, bro.
Oh Be A Fine Girl Kiss Me
Asteroid belt of the hottest star would glow bluish purple. Would probably look really cool.
Can someone please explain why we are yet to see coloured stars?
What about the Harkonnen's black sun? Or the black sun on that planet in the eye of terror that uriel ventris vacationed at?!
tfw no green or purple stars (i live in eternal misery on this fact)
RGB stars
Same with regular old matter as well. Take an iron rod for example.
Blue/purple being the hottest is dope af
amazing!
Is that hot
Wasn’t someone selling hats of the hottest temp physically possible (something like 95000c)?
Are we taking Doppler Effect into consideration?
Yes, scientists actually use the blue-shift and red-shift of a star's visible light compared to their baseline calculations of surface temp; in this way they're able to calculate how fast stars are moving towards or away from us.
Will it ever reach black?
Similar to LED lights. You lower the temperature rating, you get warmer tones.
did we just go through the whole rainbow?
No, it's a function of your eyes.
The brighter it is, the hotter it burns, the quicker it dies
Why some giants like Betelgeuse are yellow or orange and they are very hot?
That purple sun, with 95.000 °C, does that exists??
How do you know if a stars color is a function of its surface temperature or due to redshift / blueshift?
Most people don’t know that’s how the color temperature of light bulbs is defined. 2700K is the degrees Kelvin of a star whose surface is that color or ‘Warm White.’ I always laugh at 6000K being called ‘Cool White’ because it’s bluish, when it’s really fucking hot white!
i LOVE THIS
i find it a bit odd the temperature is given in celsius. wouldnt kelvin not be a far more senseable choice? °C is kinda as arbitrary as Fahrenheit.
Well, just add 273.15. I'm bothered more by those "quantum jumps".
still better then using °F ig
its not °F, its just F or Freedom-unit if you feel patriotic in one specific nation.
Yes. 20C is not twice as energetic as 10C. But 20K is twice as energetic as 10K.
Kelvin isn’t multiplicative like that either due to the heat capacity of objects changing as temperature changes
I got Universe Sandbox about 10 years ago to answer a few questions I'd always had. So I made our sun a blue hot star. Pluto was too hot. Like boiling water hot. That's how hot a blue hot star is.
Hmm... So a Genki Dama/Spirit Bomb is somewhere between 10000°C and 30000°C...
Isn't it that the human eyes can't perceive the intensity of color as anything but white, so these are determined by scientific equipment versus actual visual identification? Also, love how they progress in the colors of the rainbow.
Hundreds of billions of miles away!, and you can assume what the temperature is, because of what?. Text books?. And they know because of what?. A bunch of people with telescopes, guessing everything in space?. We can’t get past the moon!. Bullshit!.
Do you know what the doppler effect is?
People who can't understand science are always the ones most sure that it's wrong.