Awesome!! It was so easy to understand and it cleared a lot of doubts.... I want to please request you, if could make a more detailed video on this topic? Like how astronomers exactly do the calculations. And what are the research projects one can work on..
Nice tutorial on stellar spectroscopy! About helium, though: as you show around the 7:10 mark, we normally don't see helium (in absorption) in the photosphere of stars (except for the hottest stars), but sometimes in emission from coronae of stars. The helium resulting from fusion in stellar cores, do not normally make it to the surface. Some of it gets spread into the inter-stellar medium if the star explodes at the end of its life (many don't), but most of the helium in the Universe (and stars) is primordial, i.e., produced in the Big Bang - 24.71% by mass.
Hi Paul, I just want to let you know I accidentally disliked the video and this website had the gall to tell me that such information was shared with you. It was an accident and the video has now been liked by me. Hope you get boosted, this channel is amazing and you made stellar spectroscopy very easy to understand, thank you!!!
Supercool, did not know you could see red shifting on rotation, but I guess some things rotate fast and then our instruments as they get better can detect the slower rotating things, wow, as a physicist myself, didn't think this through.
Thanks for this. Going to watch your first video on Spectroscopy now, too.. While watching your illustration on Translational Motion and the resulting red or blue shift, I noticed that the examples assume a perpendicular motion with respect to the viewer. It made me think that there would likely be some angle to the movement in all three directions with respect to the viewer and I wondered if it would first be necessary to calculate the Resultant Vector from the x, y, and z components of the motion in order to do that? I realize this was just a quick illustration. But, it made me wonder how is the actual "travelling towards us" or "travelling away from us" speed calculated? This is fascinating stuff.. Thanks again!
Doppler shift formula. You would have a spectra "at rest" where the lines are falling at the specific wavelength. If the object travels towards us those spectral lines will be shifted towards blue side of the spectrum and if it travels away then towards red side of the spectrum
The singular of spectra is spectrum. You are frequently using spectra when it should be spectrum. Also, I think you mentioned photosphere once or twice where it should have been the sun's atmosphere, the chromosphere. The chromosphere absorbs light, giving you the dark lines, and the light itself comes from the photosphere. Nice explanation of temperature, density, rotation, and radial velocity, but you also mentioned the Wein law for temperature and didn't say how that relates to temperature as measured by the varying relative intensities of the lines.
Not entirely correct. Photosphere = sphere of light, is the layers where the photons we observe come from and is about 500km deep. Here the temperature decreases towards the observer, which is why the lines forming there are in absorption. Above that is the 1-2Mm deep chromosphere, where temperature increases slightly towards the observer, giving weak emission features - often as a central (emission) peak in strong photospheric absorption lines. Above that, and stretching out into the solar system, is the 1-2 million Kelvin corona (much hotter than the 5774 K photosphere) which gives rise to strong emission lines. And I guess ionization and excitation equilibria (your last comment) was outside the scope of this video - I think that was a reasonable call, given the target audience... But still a very interesting topic.
@@astroartie1872 I didn't want to give a full lecture. Anyway, I assume the discovery of helium was from emission lines from the chromosphere during an eclipse. Can you confirm or refute, please?
@@betaneptune I corrected your statement about absorption lines forming in the chromosphere - they form in the photosphere - no demand for full lectures. And you are correct about helium being discovered from observations of a solar eclipse, by Pierre Janssen in 1968, who saw previously uncategorized emission lines.
The 2 lines at D in the sun's absorption spectrum are sodium (D1 and D2), not helium. The photosphere is too cool to excite helium, hence no absorption. In contrast, solar prominences are hot enough to have a helium emission line (D3), but they have no sodium emission lines (D1 and D2) because sodium atoms are too heavy to be carried up in quantity.
Hi Paul -- thankyou for this video. One of my Year 12 students was asking (regarding density) why more collisions results in fuzzier bands and what are the collisions between ( I assume nuclei in the photosphere). Do you have any further explanation to this or could you point us in a direction to find more information?
I think it relates to the fact that when Collison happens between two atoms (or molecules) the electrons repel each other hence distorting their orbit around the nucleus. When this happens, their energy levels gets changed Slightly (as the energy levels are the function of distance from the nucleus due to the electromagnetic forces) so depending on the kinetic energy of the atoms in Collisions, their atomic spectra will differ too
I can see how the absorption lines present in the spectrum of the sun and that indicates the elements present in the atmosphere of the sun. Question, if none of those were present why would the naked spectrum not be the pure emission lines of Hydrogen and Helium? In other words, how can a gaseous light source emit a blackbody spectrum. Aren't laboratory blackbody light sources made out of graphite and such which are hexagonal carbon? How much carbon is in the sun? Thanks.
@@elewolfgt4685 lol… I knew I was probably a little late. You can use it for future reference though. If you become an astrophysicist just remember to keep up with your crayon inventory.
Excellent video sir.I have one particular question .The question is that the absorption lines are caused due to the presence of gases between the star and and the observer so how do they give us information about the interior of the star??
More about the outer layer of the star, or atmosphere. The energy released from the core is basically gamma. As those photons travel to the surface (takes millions of years) the EMR now includes other forms including visible. As this passes through the solar atmosphere absorption of certain wavelengths takes place.
That depends on the body . The body is a black body emitter but f the radiation passes through an atmosphere of sorts, and thats the case with stars, then some of the radiation gets absorbed. So for example the sun roughly is a blackbody emitter but it also has an absorption spectrum.
@@PhysicsHigh I understand the concept of the sun both being a blackbody emitter and (because of its atmosphere) also having spectral lines from your excellent video explaining that fact. I guess my real question is, is there some definitive point (density value?) where an object changes from producing spectral lines to becoming a blackbody emitter?
Hi, I have a question, aren't the lines D1-2 sodium, Helium should be D3 or d. But I am not really sure because I just see it from Wikipedia. Btw thank you so much for this informative video, I get a lot from it.
I've been reading my textbook for hours trying to grasp this, and you explained it perfectly in a matter of minutes. You're amazing! Thank you!
Qqqqqqqq
Paul you legend, helped me so much with this assignment I was doing last minute. True hero....
Thanks
I'm in the same exact situation right now. You're a life saver
I'm sure even Arnold Rimmer would have ACEd that question on his astronav exams if he had access you this video on TH-cam.
Most comprehensive spectroscopy video I could find. I thank you immensely for your efforts!
Awesome!! It was so easy to understand and it cleared a lot of doubts.... I want to please request you, if could make a more detailed video on this topic? Like how astronomers exactly do the calculations. And what are the research projects one can work on..
This cleared up so much for me. I was missing a few things in which you filled in the blanks. Thank you so much!
You're welcome!
This is the best video I've seen that explains how spectral lines work! Thank you so much! :)
Nice tutorial on stellar spectroscopy!
About helium, though: as you show around the 7:10 mark, we normally don't see helium (in absorption) in the photosphere of stars (except for the hottest stars), but sometimes in emission from coronae of stars.
The helium resulting from fusion in stellar cores, do not normally make it to the surface. Some of it gets spread into the inter-stellar medium if the star explodes at the end of its life (many don't), but most of the helium in the Universe (and stars) is primordial, i.e., produced in the Big Bang - 24.71% by mass.
Hi Paul, I just want to let you know I accidentally disliked the video and this website had the gall to tell me that such information was shared with you. It was an accident and the video has now been liked by me. Hope you get boosted, this channel is amazing and you made stellar spectroscopy very easy to understand, thank you!!!
Thanks 🤓
I studied this in university and I still found this a nice easy way of describing these concepts.
The best introduction to astronomical spectroscopy I have seen. Thank you for this.
Fantastic video. Such clear and simple explanations. I was struggling a lot with these concepts and now I feel they make total sense. Thank you Paul!
This video helped me so much for my class presentation. Thank you sir
You’re welcome
@@PhysicsHigh 😇😇😇thank you for replying on my comment
Supercool, did not know you could see red shifting on rotation, but I guess some things rotate fast and then our instruments as they get better can detect the slower rotating things, wow, as a physicist myself, didn't think this through.
Nice! I didn't realize you could learn so much just from light. I only knew about the the red shifting.
Fantastic video! I loved the comparison of the different spectrums!
Excellent video! Clear, concise and detailed. Thank you!
Thank you !
Insanely well explained !! Loved it.
Thankyou.
The content is just fantastic, that's the best and most didactic explanation I've seen!
Thanks
Incredible video, so concise and to the point, thank you so much
Thanks. Glad it helped
Brilliant video
You are a bloody legend
excellent; clears up my mind too about why spectral broadening occurs . Thank you
Truly amazing how much information about the universe a bunch of photons can carry.
your input is invaluable
Great explanation.
That was very well explained, thank you. :)
I am reading What Stars Are Made Of and this was very helpful to lay reader
Brilliant work, thanks Paul
8:48 G-star
Very clear and understandable. Thank you.
Excellent video, thank you.
Excellent video and really liked the visual examples that you used.
Thanks for this. Going to watch your first video on Spectroscopy now, too..
While watching your illustration on Translational Motion and the resulting red or blue shift, I noticed that the examples assume a perpendicular motion with respect to the viewer. It made me think that there would likely be some angle to the movement in all three directions with respect to the viewer and I wondered if it would first be necessary to calculate the Resultant Vector from the x, y, and z components of the motion in order to do that?
I realize this was just a quick illustration.
But, it made me wonder how is the actual "travelling towards us" or "travelling away from us" speed calculated?
This is fascinating stuff.. Thanks again!
Doppler shift formula. You would have a spectra "at rest" where the lines are falling at the specific wavelength. If the object travels towards us those spectral lines will be shifted towards blue side of the spectrum and if it travels away then towards red side of the spectrum
Wow. That was a lot if info! You explained it very well.
The singular of spectra is spectrum. You are frequently using spectra when it should be spectrum.
Also, I think you mentioned photosphere once or twice where it should have been the sun's atmosphere, the chromosphere. The chromosphere absorbs light, giving you the dark lines, and the light itself comes from the photosphere. Nice explanation of temperature, density, rotation, and radial velocity, but you also mentioned the Wein law for temperature and didn't say how that relates to temperature as measured by the varying relative intensities of the lines.
Not entirely correct. Photosphere = sphere of light, is the layers where the photons we observe come from and is about 500km deep. Here the temperature decreases towards the observer, which is why the lines forming there are in absorption.
Above that is the 1-2Mm deep chromosphere, where temperature increases slightly towards the observer, giving weak emission features - often as a central (emission) peak in strong photospheric absorption lines.
Above that, and stretching out into the solar system, is the 1-2 million Kelvin corona (much hotter than the 5774 K photosphere) which gives rise to strong emission lines.
And I guess ionization and excitation equilibria (your last comment) was outside the scope of this video - I think that was a reasonable call, given the target audience... But still a very interesting topic.
@@astroartie1872 I didn't want to give a full lecture. Anyway, I assume the discovery of helium was from emission lines from the chromosphere during an eclipse. Can you confirm or refute, please?
@@betaneptune I corrected your statement about absorption lines forming in the chromosphere - they form in the photosphere - no demand for full lectures.
And you are correct about helium being discovered from observations of a solar eclipse, by Pierre Janssen in 1968, who saw previously uncategorized emission lines.
The 2 lines at D in the sun's absorption spectrum are sodium (D1 and D2), not helium. The photosphere is too cool to excite helium, hence no absorption. In contrast, solar prominences are hot enough to have a helium emission line (D3), but they have no sodium emission lines (D1 and D2) because sodium atoms are too heavy to be carried up in quantity.
This video is really helpful.
Hi Paul -- thankyou for this video. One of my Year 12 students was asking (regarding density) why more collisions results in fuzzier bands and what are the collisions between ( I assume nuclei in the photosphere). Do you have any further explanation to this or could you point us in a direction to find more information?
I think it relates to the fact that when Collison happens between two atoms (or molecules) the electrons repel each other hence distorting their orbit around the nucleus. When this happens, their energy levels gets changed Slightly (as the energy levels are the function of distance from the nucleus due to the electromagnetic forces) so depending on the kinetic energy of the atoms in Collisions, their atomic spectra will differ too
Thank you! That was a brilliant explanation of a concept I've been struggling with.
I can see how the absorption lines present in the spectrum of the sun and that indicates the elements present in the atmosphere of the sun. Question, if none of those were present why would the naked spectrum not be the pure emission lines of Hydrogen and Helium? In other words, how can a gaseous light source emit a blackbody spectrum. Aren't laboratory blackbody light sources made out of graphite and such which are hexagonal carbon? How much carbon is in the sun? Thanks.
Great info. I learn a lot from this.
Does density refer to Atmospheric Density or the Mass/Volume for the star?
Outstanding!
Hi I have a question for my assignment!! Do scientists also use spectroscopy to decide how to color space images?
It also depends on the crayon selection available.
@@truth2power528 10 months too late man...lol i actually submitted my assignment last week finally. 9 weeks left until graduation letsss gooo 😍
@@elewolfgt4685 lol… I knew I was probably a little late. You can use it for future reference though. If you become an astrophysicist just remember to keep up with your crayon inventory.
Hi Paul, why is it that lots of collisions cause the lines to go fuzzy in a dense star?
this is great 10/10 thanks sir !!!
Nicely explained!
Excellent ! I'm sure even Arnold Rimmer would have ACEd that question on his astronav exams if he had access you this video on TH-cam !
Thanks!
You mean smack-head? ;-D
Great Video
This was SO helpful. Thank you!
Great job!
Thanks!
Thank you for crystal clear explanation.
Thankyou ! Gday from Sydney Australia
gday back - from Camden
This is sooo freaking easy to understand and soo helpful. Thank you so Much!!!!
This really helped me with my astronomy assignment, thank you so much!
Which element is in the space?
amazing video!!
Excellent!
Informative video
Can you tell the composition of a celestial body, by analyzing colors in a photograph taken by a digital camera?
amazing, thanks!
Why does hydrogen block those specific frequencies?
Thank you so much! College student struggling with elementary astronomy here :)
Thanks
Planning more astronomy videos in the next few months
I'm sure even Arnold Rimmer would have ACEd that question on his astronav exams if he had access you this video on TH-cam
Thanks lol I got a big quiz on this and I just started learning about it
No problem!
Super helpful!❤️
Excellent video sir.I have one particular question .The question is that the absorption lines are caused due to the presence of gases between the star and and the observer so how do they give us information about the interior of the star??
More about the outer layer of the star, or atmosphere. The energy released from the core is basically gamma. As those photons travel to the surface (takes millions of years) the EMR now includes other forms including visible. As this passes through the solar atmosphere absorption of certain wavelengths takes place.
Foundational graphics used well!
Thank you. My neighbor keeps asking me how we know the composition of stars and planets if they are so far away.
Amazing!
Thank you so much
Beautiful video ❤️
That was amazing
When does a body switch from being a spectral emitter to being a black body emitter?
That depends on the body . The body is a black body emitter but f the radiation passes through an atmosphere of sorts, and thats the case with stars, then some of the radiation gets absorbed. So for example the sun roughly is a blackbody emitter but it also has an absorption spectrum.
@@PhysicsHigh I understand the concept of the sun both being a blackbody emitter and (because of its atmosphere) also having spectral lines from your excellent video explaining that fact. I guess my real question is, is there some definitive point (density value?) where an object changes from producing spectral lines to becoming a blackbody emitter?
Thank you so much!
Hi, I have a question, aren't the lines D1-2 sodium, Helium should be D3 or d. But I am not really sure because I just see it from Wikipedia. Btw thank you so much for this informative video, I get a lot from it.
REALLY NICE!
in short everything is discussed make more on astronomy please
Not everything is discussed. 🤓. Have lots topics to cover but yes, lots of Astro is in the plan.
Excellent!!!
Preparing for International Astronomy Olympiad. Thank you 2020
You’re welcome. And good luck.
thank you!!!
You’re welcome
it clears up my mind so much!! thank you!!!
Glad it helped.
Thank you very much. :)
Amazing
this is so interesting
This is more than taught at the universities.
In order to be a Blackbody, the sun *must* be condensed matter. Not a gaseous plasma.
nice
Super
Who is here from Connect?
Moore William Hall Jeffrey Rodriguez George
over hee
talking way to fast
Slow the video speed down.
Mid
Haha. Knowledge is wasted on the young.
What makes u say that
@@WallOBrix Sorry, I forget. I'm old.
@@eqlzr2 I second the question by Wall O'Brix.
Inquiring minds want to know.
Thank you very much!