Good point on the pressure. We identified this as a potential problem in the editing stage. The statement by Dr. Swift may reflect his research on massive O-type stars. Also, the process of radiative diffusion does affect the temperature of the gas, which in turn "does the work" of supporting the star, as you astutely note. It's refreshing to see such thoughtful comments on RUclips. Jorge has a way of bringing the best out of the internet :)
This channel is so unbelievably good. Thank you for promoting inquiry and making science a bit more accessible for those of us outside its academic fields.
These explaining people are awesome :o "It doesn't care what you are, you're a cake that you pull out of the oven", And the drawings makes it even more understable, and funnier too :D Thank you for that video, great audio content, great drawing style. GG.
In response to your deleted post, and for the edification of other readers: It is true for a relativistic gas (i.e. photons) the relation P=1/3 E holds (photon energy implies radiation pressure). It is also true that there is radiation pressure in all (more or less) stars. However, gas pressure overwhelmingly dominates the pressure support for all mid- to low-mass stars, which constitute the vast majority of all stars in the universe.
(Continued from above.) Thus, the fusion of iron in the core marks the end state for many stars. However, the formation of heavier elements can still occur in many environments even if it doesn't lead to the net release of energy - such as in supernovae or the outer atmospheres of certain stars.
Piled Higher and Deeper Comics you guys rule!!!!! These videos are so informative, with beautiful and amusing illustrations on one of the most important topics... in the universe!! I am bewildered that your videos do not have millions of views
what he means by oversimplifying ("photons bouncing off of the material in the star") is a "thermal" scattering process in which the photons lose energy to the plasma (e.g. by Compton scattering or whatever "inelastic" absorption/emission mechanism). However, he should have emphasized that on its long journey the photon loses almost all its energy, so noone would confuse it with radiation pressure (where the photon changes its direction but not its energy)...
In the Universe, stuff that is not hydrogen or helium is only 2% by mass (much less by number). Therefore, you can often lump these two percent and consider their effect "on average". So astronomers use "metals" as a blanket term to cover everything except H and He. I am not sure about the origin of the term, though. There are more details in Wikipedia if you search for "Metallicity" (=metals content of an object.)
Fusion of elements heavier than iron does not result in the net release of energy, as can be seen in the ubiquitous plot of nuclear binding energy per nucleon vs. atomic number. This means that as a star transitions to the fusion of heavier and heavier elements in its core, eventually the energy released by this fusion is unable to prevent the star from collapsing gravitationally and - depending on its mass - it may undergo supernova. (Continued below.)
No, net energy gain for each fusion is not needed if the environment has enough energy and the kinetics of the fusion are different than the kinetics of the destruction from collision. For example, if silver gets hit by a fast alpha, the silver nuclei could fuse, the alpha could knock off some bit and continue, or they could fuse and then re-emit some neutrons or protons. The energy for a collision to occur is determined by the coulomb barrier, the results by chance and the exact quarks.
I'm a bit worried your depiction of different wavelengths at 0:56 is misleading: On the abscissa (x-axis) you are showing waves with increasing intensity (ie amplitude) going towards the right, rather than longer wavelengths (i.e. waves with crests that are further apart). Also at 3:30 what they said MAY be interpreted that most stars are supported by radiation pressure, however most stars are supported by gas pressure - random (thermal) motions of atoms that get their energy from the photons.
The frequency shift caused by the Doppler shift is much too subtle to perceive (with our eyes) for stars moving within our galaxy or for distant galaxies. Observing these subtle shifts requires measuring the displacement of spectral lines with sensitive instruments.
planetquest jpl nasa gov has a science page on the methods. Doppler shift methods (where very tiny changes in the velocity of a star are detectable in the spectrum) and planets detected using the transit method can have their atmospheric composition determined sceptrographically
The statement "It's hard to conceive that these little atoms in our bodies were actually forged together by the intense pressures inside of stars..." is incorrect. The pressure is far too low to force nucleons together. It is actually the temperature, i.e., the thermal motion of nuclei, together with quantum mechanics allowing nuclear reactions to occur. More massive stars burn with lower central densities but create heavier elements. Due to the mistake I cannot use this for teaching nucleosynt.
This is a common misconception due to the way the Doppler effect is often depicted pictorially. But the color of stars is all about the narrow band of wavelengths that the human eye perceives, and the distribution of wavelengths emitted by stars of different temperatures. Stars do, in principle, change their color due to the Doppler effect, but the change is WAY too small to see with your eye. Red stars are cool, blue stars are hot.
First, a high |dT/dr| implies convection which is an energy transport process, and has not much to do with pressure support. In addition your first sentence is inaccurate: only high mass stars (i.e. O and B types) are supported by radiation pressure, and there is something like 1 O star to 1000 low mass stars. So actually, most stars in the universe are supported by gas pressure and not radiation pressure. Please see John Johnson's reply below (in which he agreed with me).
very cool! :) I am actually studying the formation of the universe, our solar system and earth right now, exams in August! :) (Earth Science in Zürich) This gets me so much more motivated to study and revise, and learn lots more!! Thanks :D
Maybe someone already said this, but it is important to stress that astronomers call everything that is not hydrogen or helium "metals". So a chemist will think that e.g., oxygen is not a metal, but to astronomer -- it is.
just a little nitpick - light does not take 50,000 years to get out of a star's center. ENERGY does. The photons and kinetic energy go through ~5e38 atoms, with a density of slightly MORE than water. needless to say, any given photon will have been absorbed well within a meter of creation. All we see is the Photosphere, where these photons can escape.
heehe! you may want to take that back d00d, the little black thing that appears to be a 2 is actually just pre-existing debris in the drawing we have a mono!
This is a very nice video. There is, however, a factual error: the time for a photon to random-walk out of the Sun is of the order of 10⁷ years, and not 5.10⁴ years.
Nope, it's 50,000 years. You can figure this out using the mean density of the Sun and the Thompson cross section. 10^7 is closer to the Kelvin-Helmholtz timescale.
lol chill out dude. it was just a joke cause oxygen is a nonmetal but in astronomy its considered metal... you'd think the spelling would make it clear I was joking
This guy is doing a great service for humanity with these comics.
Good point on the pressure. We identified this as a potential problem in the editing stage. The statement by Dr. Swift may reflect his research on massive O-type stars. Also, the process of radiative diffusion does affect the temperature of the gas, which in turn "does the work" of supporting the star, as you astutely note.
It's refreshing to see such thoughtful comments on RUclips. Jorge has a way of bringing the best out of the internet :)
This channel is so unbelievably good. Thank you for promoting inquiry and making science a bit more accessible for those of us outside its academic fields.
These explaining people are awesome :o
"It doesn't care what you are, you're a cake that you pull out of the oven",
And the drawings makes it even more understable, and funnier too :D
Thank you for that video, great audio content, great drawing style. GG.
I LOVE these videos. They're so informative and fun to watch!
Brilliant! Please make more of these!
This is wonderful! My 9-year-old wants to be an astronomer and he watched it with me and loved it too!
I would encourage everyone to look up at the stars and ask questions. thanks for the nice video!
great stuff. Thanks for explaining complex concepts in very simple language.
Awesome work guys, it was really easy for me to understand how we determine what starts are made of. Keep up the great work!
Beautiful. Absolutely beautiful.
In response to your deleted post, and for the edification of other readers: It is true for a relativistic gas (i.e. photons) the relation P=1/3 E holds (photon energy implies radiation pressure). It is also true that there is radiation pressure in all (more or less) stars. However, gas pressure overwhelmingly dominates the pressure support for all mid- to low-mass stars, which constitute the vast majority of all stars in the universe.
i absolutely love the comic book story with the info! so much fun for visual learners and very memorable.
These are always so great. And your animation has taken on a new depth and movement. May I ask what software you use to create your animations?
How does he achieve this wonderful animation? How to get this 3D effect with the background and the nice transitions around the image???
This was the most amazing thing I have ever seen. Just wow!! thank you for this.
(Continued from above.) Thus, the fusion of iron in the core marks the end state for many stars. However, the formation of heavier elements can still occur in many environments even if it doesn't lead to the net release of energy - such as in supernovae or the outer atmospheres of certain stars.
Piled Higher and Deeper Comics you guys rule!!!!! These videos are so informative, with beautiful and amusing illustrations on one of the most important topics... in the universe!! I am bewildered that your videos do not have millions of views
what he means by oversimplifying ("photons bouncing off of the material in the star") is a "thermal" scattering process in which the photons lose energy to the plasma (e.g. by Compton scattering or whatever "inelastic" absorption/emission mechanism).
However, he should have emphasized that on its long journey the photon loses almost all its energy, so noone would confuse it with radiation pressure (where the photon changes its direction but not its energy)...
Awesome change in style! Love it! Congratulations :)
Fantastic!
Besides the electromagnetic spectrum of a star, is there any other way to check its composition?
In the Universe, stuff that is not hydrogen or helium is only 2% by mass (much less by number). Therefore, you can often lump these two percent and consider their effect "on average". So astronomers use "metals" as a blanket term to cover everything except H and He. I am not sure about the origin of the term, though. There are more details in Wikipedia if you search for "Metallicity" (=metals content of an object.)
Fusion of elements heavier than iron does not result in the net release of energy, as can be seen in the ubiquitous plot of nuclear binding energy per nucleon vs. atomic number. This means that as a star transitions to the fusion of heavier and heavier elements in its core, eventually the energy released by this fusion is unable to prevent the star from collapsing gravitationally and - depending on its mass - it may undergo supernova. (Continued below.)
Thanks ! Any chance there's a web page somewhere that explains this is more detail ?
No, net energy gain for each fusion is not needed if the environment has enough energy and the kinetics of the fusion are different than the kinetics of the destruction from collision.
For example, if silver gets hit by a fast alpha, the silver nuclei could fuse, the alpha could knock off some bit and continue, or they could fuse and then re-emit some neutrons or protons. The energy for a collision to occur is determined by the coulomb barrier, the results by chance and the exact quarks.
I'm a bit worried your depiction of different wavelengths at 0:56 is misleading: On the abscissa (x-axis) you are showing waves with increasing intensity (ie amplitude) going towards the right, rather than longer wavelengths (i.e. waves with crests that are further apart).
Also at 3:30 what they said MAY be interpreted that most stars are supported by radiation pressure, however most stars are supported by gas pressure - random (thermal) motions of atoms that get their energy from the photons.
The frequency shift caused by the Doppler shift is much too subtle to perceive (with our eyes) for stars moving within our galaxy or for distant galaxies. Observing these subtle shifts requires measuring the displacement of spectral lines with sensitive instruments.
YAY I ACTUALLY UNDERSTAND SOME STUFF NOW I DIDN'T BEFORE, YOU MADE THAT SO SIMPLE :) TY!
planetquest jpl nasa gov has a science page on the methods. Doppler shift methods (where very tiny changes in the velocity of a star are detectable in the spectrum) and planets detected using the transit method can have their atmospheric composition determined sceptrographically
great video!
The statement "It's hard to conceive that these little atoms in our bodies were actually forged together by the intense pressures inside of stars..." is incorrect. The pressure is far too low to force nucleons together. It is actually the temperature, i.e., the thermal motion of nuclei, together with quantum mechanics allowing nuclear reactions to occur. More massive stars burn with lower central densities but create heavier elements. Due to the mistake I cannot use this for teaching nucleosynt.
this is awesome!
@5:25 She says that the light spectrum can revel if a star has planets. How does that work ?
i feel so smart having watched this and understanding even half of it. :D
This is a common misconception due to the way the Doppler effect is often depicted pictorially. But the color of stars is all about the narrow band of wavelengths that the human eye perceives, and the distribution of wavelengths emitted by stars of different temperatures. Stars do, in principle, change their color due to the Doppler effect, but the change is WAY too small to see with your eye. Red stars are cool, blue stars are hot.
I wish I could get some of the artwork from these videos and use them as desktop backgrounds.
First, a high |dT/dr| implies convection which is an energy transport process, and has not much to do with pressure support. In addition your first sentence is inaccurate: only high mass stars (i.e. O and B types) are supported by radiation pressure, and there is something like 1 O star to 1000 low mass stars. So actually, most stars in the universe are supported by gas pressure and not radiation pressure.
Please see John Johnson's reply below (in which he agreed with me).
How is this presentation made?
the planets actually temporarily block a tiny portion of the light, and so you can watch for periodic tiny fluctuations.
He wasn't asking that. He just asked a simple question and he is right.
Brilliant
very cool! :) I am actually studying the formation of the universe, our solar system and earth right now, exams in August! :) (Earth Science in Zürich) This gets me so much more motivated to study and revise, and learn lots more!! Thanks :D
Maybe someone already said this, but it is important to stress that astronomers call everything that is not hydrogen or helium "metals". So a chemist will think that e.g., oxygen is not a metal, but to astronomer -- it is.
Pretty awesome
just a little nitpick - light does not take 50,000 years to get out of a star's center. ENERGY does. The photons and kinetic energy go through ~5e38 atoms, with a density of slightly MORE than water. needless to say, any given photon will have been absorbed well within a meter of creation. All we see is the Photosphere, where these photons can escape.
heehe! you may want to take that back d00d, the little black thing that appears to be a 2 is actually just pre-existing debris in the drawing
we have a mono!
Please please please! Make these into posters and sell them in your online shop! :)
They have it correct at 0:56...the wavelengths are longer to the right.
that makes sense. thanks for the explanation :)
“The Lord knows each star by name” Isaiah 40:26 🌟
Au contraire, watch it in 1080p and you'll see a little subscript 2 shaking with "CO" -:)
Ok somewhat random but why is the kid in the last panel speaking in spanish? Kind of awesome.
Oh, you're right!
they ALSO change the spectrum, so there is evidence of atmosphere, whether the planet is a gas giant or has water, and so forth.
Right, but that doesn't really change the spectrum, right ? So planets can be detected just by looking at the brightness.
doesn't nuclear fusion in stars stop at iron? anything past that is a net loss of energy. how did tungsten come to be?
Username18981 supernova explosions
Yeah there is.
Wait, does this mean that if we lived in a solar system where our sun was way hotter, we could potenitally percieve it to be a blue sun?
This is a very nice video. There is, however, a factual error: the time for a photon to random-walk out of the Sun is of the order of 10⁷ years, and not 5.10⁴ years.
The sun is Electric.
Check out David Talbott and Wallace Thornhill's Thunderbolts of the Gods.
Iron is a star-killer, according to the curve of binding energy.
Nope, it's 50,000 years. You can figure this out using the mean density of the Sun and the Thompson cross section. 10^7 is closer to the Kelvin-Helmholtz timescale.
una estrella papi!
And I thought the color of the stars that we perceive was due to the Doppler effect...at least that's what I've been taught.
that explains a lot. but why do the astronomers do this?
Red stars are cool. 8D
Pricesly. But we couldn't live on Earth at same distance. =)
Men looking for Melodie Kao in 3, 2, 1...
Must see video,
ELECTRIC UNIVERSE: Invitation to Future Scientists
Check wikipedia before posting.
(My field of research is stellar and explosive nucleosynthesis and nuclear astrophysics.)
Fundamental unit of cosmos is Hydrogen.
There's no 2 there :-)
mike slackenary does not approve the length of this video
My bad...
Sure. But my main point is that there is a factual error in the video (and thus many viewers may learn something incorrect).
that is weird
Obviously mad
lol chill out dude. it was just a joke cause oxygen is a nonmetal but in astronomy its considered metal... you'd think the spelling would make it clear I was joking
Wtf
stoopid astronomers, oxygen is not metal
stop talking all together!!!!!!! It's annoying !!!
una estrella papi!