M6 - Butterfly Cluster - Deep Sky Videos 

check our M67 video --- ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ZW1NP_Cb0Go.html

DeepSkyVideos Many thanks. I will do.

Alpha Centauri

Amazing whisky!

The term "red/blue shift" can be misleading. When astronomers discuss red or blue shift, they are not exactly referencing the color of the stars themselves. Rather, they are looking at the spectra of specific elements in the star, such as hydrogen. When you look at a hydrogen spectrum you will see distinctive gaps in the spectrum where light of that wavelength is being absorbed. There will be several gaps for each specific element, and each element leaves a unique "fingerprint" of its spectrum. The location of the dropouts should always be at the same locations (wavelength or frequency) of the spectrum regardless of what cloud of hydrogen you look at. When an object is moving toward or away from the observer these absorption "markers" will move slightly up and down the spectrum; they will "shift" to the red or the blue end of the spectrum. Yes the color itself may shift ever so slightly, but it is not the actual color change that the astronomers are measuring. It is the shift in the spectra of the marker elements.

Thank you, this makes sense now.

Look up Newtons prism experiment, that is where all of this started.

The wavelength, or the color, of a star is directly linked to its surface temperature (that's roughly explained by the black body radiation model : en.wikipedia.org/wiki/Black-body_radiation). When stuff gets hotter, it goes from infrared to red to white, and then starts emitting UV, X-rays and so on. Why is it so ? That's quantum physics and it is a bit more complicated to explain, here are some bits to get the core concept : en.wikipedia.org/wiki/Emission_spectrum (I did not find anything simpler). We still need to figure out why younger stars are hotter. I've tried to type it here clearly but I can't find a simple way to put it. Very, very roughly : hotter stars burn their fuel faster thus die faster, so statistically hotter stars are younger. More detail : en.wikipedia.org/wiki/Main_sequence Finally little stars can be red, like red dwarfs. There is no such thing as a stupid question. Please forgive my bad English.

Shriranga Wirth Actually in a complete young stellar population there are both blue (massive) stars and red (low mass) stars, but the blue ones are much brighter so they dominate the total light. As the population ages, the massive stars blow up, leaving behind just the low-mass red stars. Red stars can either be giant stars at the late stages of their lives, when even massive blue stars turn red, or low mass, low luminosity dwarf stars in the main part of their lives.

+cameron1004 Color diagramm and a magnitude diagramm doesn't have to has the same kind of units or rather they don't have to correspond concerning the numbering ( I can't remmber the exact correct word now, sry), remember he's NOT showing something like a Hertzsprung/Russel (which is a Color/magnitude diagramm COBINED, so it may even correspond with that, because the two lines of a pure color color diagramm are reduced into a single line, but at the same time you have another for magnitude, which uses the system you were wondering abou)diagramm there

yes

Wouldn't that be a moon tan?

Skeletor Jopko Well, technically moon light are sun light bounced off the moon's surface.. :P

You'd have to be able to count the stars for that.

You know, that means you are FIRST!

#youtube is "optimizing" sub feed, apparently, so if you do not watch every single video from a channel it will skip some of new ones and won't show them in the feed, so now views can grow slower overall, on all channels.

I looked in to this and for what initially seems like a simple question it gets difficult fast. It of course has to do with the amount of gas in the region and the state of the stars development as it moves from Proto-star to Pre-Main Sequence to Main sequence, but ultimately we dont actually know all the details. Depending on the amount of gas contracting, temperature of the core, opacity of the clouds, etc, the star will blow off the gas or continue to accumulate mass to varying degrees before fusion and an equilibrium forms for the main sequence. The details of this turbulent period are tricky though, they can not tell exactly what will happen, and small differences in the clouds may lead to dramatic changes in the star formation. It was helpful to me to remember that the core is at extreme temperatures of millions of kelvin long before fusion, (Caused by the kinetic in fall and pressures of the staggering amounts of mass involved.) and those temperatures radiate huge amounts of energy that can achieve varying balances within the star without allowing it to finally produce enough pressure and heat to trigger fusion at the same time in every case. It would be nice to see a deep sky video on it though, clarify the details and make sure Ive not gotten the wrong ideas.

Bob Spitfire Very good answer. The important takeaway is that the physics of star formation are very complex and not fully understood at this time. If it was as simple as A + B = C, then every star in the universe would be pretty much identical.

Because the whole point is you can't resolve the individual stars, so you can't count them to get a median value

Before I'm found in a ditch by physics-motivated murder, to me, loving physics was a prerequisite to becoming an amateur astronomer. I don't know if that's true for everyone but it most definitely was for me.

I thought I recognized M6 from somewhere. It's the sixth brightest Messier object visible from where I am. I've set out to photograph it before but alas, no result. Maybe this video will motivate me to go out and actually find it. If I do I promise I'll be back here with my images. If anyone here uses stargazers lounge, or is anywhere near S/W London and is into this sort of thing.. Hit me up :)

Philip Johansson think I kept changing my mind on the wording (between the effect and the light being affected by dust, etc) - and changed it one too many times. Oh well... Such is life.

Thought I was the only one who noticed! It's fine Brady, we'll let you away with it this time

No. The color is most influenced by the star's temperature. The temperature is influenced by the rate of fusion taking place in the star's core, its mass, and its diameter. For typical stars (excluding white or brown dwarfs, where the physics is substantially different), hotter stars will be blue, cooler stars red, with a continuum of color between the extremes. As stated in an earlier comment, an object needs to be moving toward or away from you at a fairly good fraction of the speed of light before a color difference due to the doppler effect would be measurable (such as making a red supergiant appear blue).

Well its still there, just it doesn't look the same from different angles so they would call it something else.

Measuring the doppler shift is key to knowing that they are physically clustered. Stars closer or further would show a different doppler shift that the stars in this cluster. I'm afraid I do not know enough to answer your second question with any accuracy. :)

Astronomers can correct the diffraction caused by telescopes. I believe it's to do with knowing that stars are point sources of light, and so because of that, distortion via diffraction, turbulence or even anomalies in the atmosphere can be corrected.

Could you not measure from the center of the source of light of each star? The problem I don't understand is how would you measure distance between stars when we only see them from one angle? Star A and B may look to be half a light year away from each other from earths perspective; all we see is a 2D plane, we can only measure the distance of x and y. But we don't see the distance of z, so how can we say how far stars are apart?

Mrhollerr While I am no astronomer, and I am sure other methods are used; both Parallax and Doppler shift could be used to calculate distance from us. (The Z axis in your example.)

ShonkyLegs​ I should familiarize myself with these methods.