ZAMS and globular clusters (1 Viewer)

[jang]

the syl says ' explain how the age of a globular cluster can be determined from itz ZAMS plot for a h-r diagram'

now what im thnkin is that ZAMS for a globular cluster would be the similar ZAMS for open cluster?? since ZAMS represent zero mass stars and at one stage surely globular clusters were also young and bright. then how can the age of globular clusters be dterming from its ZAMS?
i kno it can be determined from the turn-off point of its real-time/normal plot on a hr diagram...but the zams thing dont make ne sense

 

[helper]

ZAMS is zero age mass stars, not zero mass stars.
Your right an open cluster would have a zams plot, which is stars along the main sequence only. The open clusters are used to determine the zams plot.

By looking at the turn off point you are looking at the point the cluster is leaving the ZAMs plot.

 

[d_elmo]

ZAMS is zero age main sequence

 

[jang]

ZAMS is zero age main sequence

sorry guysh brain explosion.
thx helper, im guessin we dun hav to go into too much detail about ZAMS and its relation to age globular clusters then? rather, just talk about talk the turn off point of the stars on the HR diagram which can be referred to the zams yeh?

 

[Logix]

wat is this turn off point? i have read bout it, but dont understand it....as always, hehe

 

[jang]

turn-off point is where the main sequence suddenly bends towards the top right hand corner looking like

......./////
.....////
...///
\\\<-- turn off point
..\\\
.....\\\ <-- main sequence
......\\\

the lower the turnoff point on the HR diagram for a cluster, the older it is because faster burning stars, that is heavier and thus more luminous stars, are located in the top left, these leave the mainsequence first to become red/blue giant or watever althou all stars were born roughly at the same time hence we can deduce their ages

 

[Logix]

thats a nice diagram

so the clusters that turn off near the top r the younger clusters and the ones that turn off near the bottom right r older clusters?

 

[jang]

yupyup!!
.,,,, (i had to lengthen the msg coz it wont let me post yupyup)

 

[Logix]

do u know how black body spectrum is produced?

 

[jang]

an incandescent lamp should produce a theoretical black body spectrum (i think? i dnno y its theoretical.. and where do u get an incandescent lamp? damn, what is it!)

 

[Logix]

but how come it produces so many frequencies? like how is THAT particular spectrum produced? the textbooks have explanations for how emission and absorption spectrum r produced but they dont explain a continuous spectrum

 

[andysoul]

the incandescent lamp is something like a light globe, the element gets hot (incandescent), and makes a black body spectrum. the reason it's only theoretical, is that there is no perfect black body, even a light globe gives off larger spikes on certain frequencies because it is made of tungsten (you get small emmision spikes). and the way it emits a broad spectrum is because each of it's particles are acting like tiny radio transmitters. you know when a moving charge in a radio transmitter is alternated at say, 100 Hz, you get a radio frequency of 100 Hz being produced. the same is true for the atoms of the black body (as far as i understand anyway). each of the atoms is vibrating, and as it gets hotter (more kinetic energy in each particle), they vibrate faster and give off a higher frequency, and hence a shorter wavelength of light.
the reason for the ultraviolet catastrophe is related to this via planck's idea of quanta. the atoms like to give off a smaller amount of energy more often, than giving off high energy photons less often, hence the lack of U.V and gamma rays (which have high energy) in a black body spectrum

 

[Logix]

ahhhhhhh thats y as the black body gets hotter, the peak wavelength moves to the lower wavelengths and higher frequencies, coz it is given more kinetic energy finally understand a bit more.....but just say it is 100Hz, shouldn't there onli be an emission line at 100 Hz, because ALL the particles vibrate at 100Hz? From what i understand (which isnt very much), there shouldnt b any other frequencies coz they all vibrate at the same frequency, 100Hz.

and isnt the ultraviolet catastrophe proved to be wrong?

 

[tennille]

If the ultraviolet catastrophe was proved wrong, that means that energy would be created, which defies the law of conservation of energy. If it was proven to be wrong, that means that classical physics had supported the black body radiation and that, as frequency increased, the energy (intensity of radiation) would increase.

 

[helper]

Your now going into quantum mechanics and does God play dice?

 

[FcUk]

an incandescent lamp should produce a theoretical black body spectrum (i think? i dnno y its theoretical.. and where do u get an incandescent lamp? damn, what is it!)

i thought all lights were black bodies?

 

[helper]

Not flourescent lights that emit light due to excited electrons. The tube and gas remains cool.

Any light that works on being heated up is a black body.

 

[andysoul]

yeah, as long as its hot, it's incandescent.
the reason that it's a curve and not just a straight line is coz the kinetic energy changes from atom to atom, one might be vibrating faster than another, so it gives off a higher frequency photon, then it has less energy. It can get more energy again from the energy source (like electricity or fusion). you just gotta remember that the temperature is a measure of AVERAGE kinetic energy of each particle, there'll be some hotter, and some colder. thats why the peak of the black body curve corresponds directly to the temperature, and why there are the side curves asymptotically appraoching zero.
you might've noticed that a black body curve looks somewhat like a bell curve (slightly skewed of course) thats because of the energy range of the particles, and you get this probabalistic sort of effect in the shape of a bell cuve, just like students test scores