M72 - Variable Stars - Deep Sky Videos
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- Опубликовано: 11 окт 2024
- Professor Mike Merrifield discusses variable stars in Messier 72 - also known as NGC 6981.
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Video by Brady Haran and James Hennessy
I could listen to Prof. Merrifield for hours
We have!
Fantastic description of variability; it's suddenly so clear - thank you so very much! What a great resource. Cheers.
and all it took was just a fresh new video on this channel for me to start rewatching a couple from the past...
RUclips randomly recommended this to me, and I dig it.
You’ve got some catching up to do. :)
@@DeepSkyVideos Its like having a whole back catalog to explore :)
Like the remark about the myths! 😁👍
7:05 great outro sentence: myths come first, physics comes later! ... some people are in the first stage, some are in the later one. sometimes it does not feel like humanity as a whole is moving toward the latter
Yessss. Just went on a bender last night and watched all the Messier catalog LOL 🤣
Would someone please make the executive decision to expand the Messier catalog? I'd hate for this series to end.
I want DSV to continue with the ARP-catalogue of Peculiar Galaxies.
They did in the 90s, its called the Caldwell catalogue.
hey, DeepSkyVideos
can you please make a video on angular sizes?
JWST was declared a "70 milli arc seconds" resolution, but there's pretty much nothing to compare that number to...
Can you show different (astronomical) objects with their angular sizes, maybe showing how much detail what resolution gives?
Imagine a circle around the sky. That circle has 360 degrees in it. Each of those degrees has 60 arcminutes, and each of those arcminutes has 60 arcseconds. The Moon is about 31 arcminutes across. So 70 milliarcseconds is about 1/2660 of the width of the Moon.
@@michaelsommers2356 thanks, now please find some object the size of 10 arcminutes, 1 arcminute, 10 arcseconds, 1 arcsecond, 100 milliarcseconds, 10 milliarcseconds
and maybe notable nebulae, galaxies, notable objects within those (i.e. there's no info on size of Pillars of Creation, only on the nebula it's in), planets, biggest stars
and don't forget helping compare telescopes too! what's the resolution of Galileo's telescope (if it could do exposures)? of the one that found the Uranus, the one confirmed Neptune? the one Hubble the scientist used to detect expansion of the universe? biggest telescopes of today? Very Large Telescope of the future?
I want the whole list, not just 1 example
@@michaelsommers2356 also you missed by order of magnitude, it's 1/26k
Comparing scopes is difficult with any image, the resolution depends on what wavelengths you're looking at. For example James Webbs at 77 is worse angular resolution than hubble had at 40 but that is is only for higher wavelengths the jwst is also capable of seeing when its looking at the lower 5-600 nm range closer to what hubble did it reaches down into the 20s. You also need to account for distances and zoom when comparing size by images it's better to just stick to numbers and use the scale next to the picture for relating size.
The size comparison you suggest would make for a nice video, I think.
Myths perhaps would say that the Sun is a heart of a giant, beating in rhythm, and this giant needs feeding or sacrifices to remain calm
This is so nice. I love it. Mike is such a nice guy
Omg...day made.
Where do the electrons go when they're thrown off the helium? And why do the compressed nuclei of the helium become opaque? What is the relative distance difference between nuclei of helium and the two ions of it in variable stars?
How come the region of doubly ionized atoms doesn’t reach an equilibrium? Why does it keep “overshooting”?
Because it's at a depth where the two forces can vary considerably without too much feedback. Layers at other depths are dampened as the strength of feedback decreases the disruption. A deeper layer is dominated by pressure, little expansion can occur, causing little reversal and the 'overshoot' is suppressed to nothing. Shallower layers are dominated by expansion and compress only slowly, allowing time for equilibrium to be reached.
Only at the right depth are both processes so balanced as to allow significant under\overshoot before the balancing force is appreciable.
The density change of particles is too fast and large for gravity to keep the star on the equilibrium. He2+ vs. He1+ that is. The extra electron separates the nuclei by ... I don't know how much, but it's a lot.
Thank you.
Michael it's been awhile...guess Covid really impacted you all as l've seen a few of Meghan's posts. Yes you all were missed. Stay safe and plan to try n keep this series going as already shared .
Oh really enjoyed the video...you've done one or two others. I luv GCs..one of the 1st DSO l.looked at when l started out using a Japanese 60mm....that's way back in 1960
Does the helium change opacity as it changes ionization state? How is energy flowing through it? Is it radiative?
Changing the ionization state of things is one of the most effective ways to change their opacity. Free electrons scatter EM radiation.
Energy transport in stars is usually a combination of radiation, convection and conduction. Which of these dominate depends on the conditions. As material gets more opaque, the radiative process becomes less effective.
that last line though :)
Prof. Merrifield is my txt message tone !
Thank you for bringing up the origin of myths. If more people knew or were capable of seeing from that perspective, well, we’d probably already be on Mars.
How many are left now?
Three (M88, M107 and M108). I think some of the early videos are worth a remake (like what they do for the elements on Periodic Videos, or the second video they did on Messier 40).
M88 and M108 are galaxies (and beautiful ones, too). M107 is a very loose globular cluster, very similar to M72. In fact, the only interesting thing I can find about M107 are its variable stars...
Thanks!
@DroppedPasta,
Yes, correct.
But I've got the impression that he's trying to get the bus,,,gee man..slow down...not all viewers are native speakers.
Bedt regards from Holland🇳🇱
Yes, I corrected that flaw by using Settings -> playback speed -> 0.5
Jochem Mijjer is also a Hollander, of Nederlander eigenlijk...
best regards from Gelderland.
The myth comes first. The physics comes later.
What comes after the physics?
The RUclips video
@@DeepSkyVideos hahaha
Love these videos! Watched all of them but the algorithm throws one at me every time I refresh and they're always an insta-click! 😄
Nice
No views?
arnt the research now 10 years old but this video not ?