Cepheid variables 1 | Stars, black holes and galaxies | Cosmology & Astronomy | Khan Academy
HTML-код
- Опубликовано: 25 авг 2024
- Courses on Khan Academy are always 100% free. Start practicing-and saving your progress-now: www.khanacadem...
Cepheid Variables 1. Created by Sal Khan.
Watch the next lesson: www.khanacadem...
Missed the previous lesson? www.khanacadem...
Cosmology & Astronomy on Khan Academy: The Earth is huge, but it is tiny compared to the Sun (which is super huge). But the Sun is tiny compared to the solar system which is tiny compared to the distance to the next star. Oh, did we mention that there are over 100 billion stars in our galaxy (which is about 100,000 light years in diameter) which is one of hundreds of billions of galaxies in just the observable universe (which might be infinite for all we know). Don't feel small. We find it liberating. Your everyday human stresses are nothing compared to this enormity that we are a part of. Enjoy the fact that we get to be part of this vastness!
About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.
For free. For everyone. Forever. #YouCanLearnAnything
Subscribe to Khan Academy’s Cosmology & Astronomy channel: / channel
Subscribe to Khan Academy: www.youtube.co...
It is the best explanation of how she figured it out, I have learned more in this video than all my books pn Astronomy,
Thank you.
So basically, she found a cepheid variable with a given luminosity in our galaxy and used parallax to work out the distance, she then had a standard candle. Once you can match the period on other stars in the universe you will know its brightness to which you can use the standard candle to work out the distance.
Truly a great explanation, was very interesting
Bravo!
The basic yet difficult idea that is the basis of all further laws of astronomy that how can some one measure the absolute luminosity of a star.
Great video, thank you for making it. I don't understand how the assumption at 4:00 can be made. Anywhere you look in the sky, any astronomical object you see is potentially at almost any distance away. Just because you are looking in the direction of a cloud, that doesn't mean the object under observation is in the cloud. The only explanation of why this assumption would work I guess is that if you noticed many variable stars and saw a pattern, you could assume MOST of them were together in the cloud...
such an intuitive mind she had, truly a remarkable scientist that pushed mankind’s understanding exponentially
I have a GCSE physics exam, and although i have 100 percent in all the modulars, the last one has this topic and it is has baffled me until now, Thank you so much for this Really Helpful :)
Leavitt was brilliant. I love it when some "nobody" revolutionizes science.
Sal, is there anything you don't know? LOL
I just love listening to you man, how can some teachers make something this interesting seem boring I will never understand. You enthusiasm is contagious!
Fantastic explanation. Enjoyed watching this, I love Learning about Stars!
your a genius...! It's really cool that you have videos on all the sciences like Bio, chemistry,astronomy, and other stuff ...
soooooooo sick !!!!
wow amazing video
Great video. Thanks!
I was reading a book the other day called Galaxies: A Very Short Introduction. The explanation of Cepheid variables in there made sense mostly but I didn't connect all the dots. Watching this video has made me understand it properly now. Thanks!!
that was awesome
Great explanation and video , thanks.
when they are small and hot, they are intense, but their brightness to the earth is lower since they are smaller, it eventually reaches a point where the brightness declines again during expansion (at point where coolness is affecting brightness more than size--heat decreasing faster than size is increasing-etc)
Using this video to study for exam.
Luminosity varies due to the makeup of the stars. If a star is massive and made up of mostly hydrogen, it will burn fast and hot. Other stars, like our sun, will live for billions of years but are much smaller. Still other stars are relatively tiny! Look around Wikipedia and other places to read about Main Sequence Stars.
This is kinda interesting but idk why i wanna sleep after listening to his voice tho😭
Astronomy 👀♥️
the stars themselves are contracting and expanding, as they heat their light peaks as they are hot and expanding (somewhat large)--before cooling--and is lowest when they are around the same volume but cool and contracting
Exactly backwards from what you said. It's counter intuitive, but when cepheids are at their smallest, they are at their hottest, but they are also at their dimmest. When they expand to their maximum size, they are at their coolest, but also at their brightest. The theory is that cepheids are dimmest at their smallest-size and hottest point due to the way helium in the star's atmosphere absorbs light when helium is at higher temperatures. Conversely, helium allows more light to pass when the helium is cooler (e.g., after it has expanded to its maximum size due to thermally driven expansion).
First rate explanation.
always a pleasure
thumbs up just because I now know i'm not the only one who struggles with that word - Magellanic
Mr. Khan, this'll sound a bit off-topic, but it is vital to comprehend the study material at the present moment, so please do bear with me and do correct me if I get this incorrect, as well as telling me if I do get it correct. Based on your Log scale, a "log" is the exact inverse of powers/exponents. It is the attempt to figure out the exponent for a specific number, am I right or have I got it completely backward?
I'd really appreciate knowing, as I never reached logs in even high school, and barely understood them in college.
What makes their luminosity vary?
I love learning about women in science. It’s like a well kept secret 😂
It's always the little things.
In this case, what does the period mean, and how does the period relate to the sun's luminosity?
How in the world do we even isolate a specific star in a distant galaxy, Mr. Khan?
👍
Mr. Khan, why would stars be bouncing in brightness and increasing in an incline? The bounce may be due to planets orbiting nearby muting some of the brightness of said star, but the steady incline is part of what is currently baffling me and I lack the ability to investigate either of these ideas, so I am escellating them to the next level; that being yourself as the instructor in this case.
Didn't they actually look at the negative plates?
@LAnonHubbard Lol... that book wasn't Dianetics was it?
31166...
8064...
Sorry but this didn't give me enough insight as to how the distance is known.
I think is with the distance module, but I'm nat that fresh on the subject.
m-M=5log(d)-5
M-absolute magnitude
m-apparent magnitude
d-distance
Pooooooooooooopppppaaaaaaa kekekekkekkekekeke
wut