Blue Stars?

Just from Wikipedia

http://en.wikipedia.org/wiki/Star

http://en.wikipedia.org/wiki/Main_sequence_star

http://en.wikipedia.org/wiki/Blue_straggler

And a specific blue star example

http://en.wikipedia.org/wiki/Zeta_Puppis

Not-to-knock wiki , here ... merely an observation :

following one of your links, I wound-up at wiki's Betelgeuse page ... wherein it states (within the same article/same page):

"...located approximately 640 light years from the Earth." [opening paragraph]

"...assumed to be 570 light years..." [under "Observed size"]

"...because of its 430 light year distance..." [under "Fate"]

No wonder kids become more and more confounded with each generation...!

There is no need to explain to *me* the discrepancies...

Simply expressing an additional aspect of my most ardent peeve.

(( At LEAST all the words on the page are spelled properly, and each sentence is grammatically correct...!))

Such uncertainties ought to be uniformly-expressed: e.g.; "400-700 light years" ... each statement hyperlinked to a page that explains "Light Year", "Parsec", and the difficulties in making accurate astronomical measurements...

vent-poof!-sigh...

without doing any research, I'm going to go out on a limb and say that blue stars are hydrogen/helium stars but at a much higher level of energy. They're much larger than yellow stars, burning much hotter. they have shorter lifespans.

yep, turns out I was right. most stars are "main line" stars--virtually all of them are fusing hydrogen into helium, even when they begin to move into the business of making carbon, oxygen, and so forth, there is still hydrogen-helium fusion going on deep down inside. These processes are so much cooler (literally) than hydrogen-helium fusion, though, that the stars move down the spectrum away from blue as they progress. Stars can be up to 150 times the size of the sun, and stars of that size are brilliant blue and unimaginably hot, but their lives are very brief because they exhaust their fuel so quickly.

I didn't understand what you mean by the following:

These processes are so much cooler (literally) than hydrogen-helium fusion, though, that the stars move down the spectrum away from blue as they progress.

Isn't the H to He the bottom rung of the required temperature (velocity of particles) for a fusion Rx, and as the temperature increases for more energetic processes to occur, such as He to C, etc? Why then would the fusion Rxs to produce higher nuclei than He be at a lower energy/temperature level than hydrogen to helium?

Perhaps paragraph 5 under "Requirements" at Nuclear Fusion answers this...(?)

(..."Helium-4 has an anomalously large binding energy..."...)

Too detailed for my current state-of-mind...!

My understanding is that 'blue stars' are main sequence as has been pointed out in an earlier post, and virtually all of the energy produced during their lifetime (as stars) is the hydrogen to helium fusion. The heavier elements are produced when these stars erupt into super novae at the end of their lives when most of the hydrogen has been consumed.

As I understand it, the core of the star does indeed get hotter & hotter as burning progresses from producing Helium to producing Carbon and Iron. However, the surface of the star gets puffed out away from the center, and it cools. That's why the star looks cooler - we can only see the cooler skin, not the white-hot heart.

Hi,

as long as considerable hydrogen is available the center of a star is more or less stable as the density is balanced by inside pulling gravitation to outside pushing radiation and pressure.

If the hydrogen supply is near its end, then the gravitation will contract the core considerably until the rising density will ignite the next element to fusion and a new (and shorter) cycle of burning with a new balanced situation starts.

This is iterating for any new burning cycle until the very last one has exhausted and the star is collapsing by the gravitational force. This collapse will give rise to the gigantic outward-traveling shockwave that we see as supernova. The inner core will vanish from our world and continue as black hole (if enough mass was existing).

"That's why the star looks cooler - we can only see the cooler skin, not the white-hot heart." Yes, I agree totally, and the diameter will change according to changed energy output.

These processes may bring an early end to us and our civilisation as the radiation may be very intense and roast us without much early warning.

RHABE

Heavy stars have high pressure in the center,

so the fusion probability is much higher then in light stars.

High fusion probability is equivalent to fusion rate and thus to energy per volume.

So the energy production in massive stars is many orders of magnitude higher than the mass relation!

High energy gives high surface temperature: the surface as a "black body" is emitting energy according to Plank's law of radiation with the peak wavelength being a function of temperature.

So massive stars produce a lot of blue and supermassive starts have their maximum in the UV.

All burn hydrogen to helium.

Near the end of life - most hydrogen burnt - is starting the burning to higher elements until iron and then the various ways of superexlosions as supernovas.

These are spewing the new elements into the surrounding space some of higher than iron atomic weight created by neutron capture.

Some maybe billion years later this star dust is re-compressed into a new star by the cosmic shock-waves and a new cycle may begin or the new star has not enough weight to end as a supernova.

Planets will accrete from the dust disc around the star.

Water will fall if one of the planets is inside the habitable region.

Life will begin? Nobody knows for sure.

Maybe a moon is necessary to stabilise the tilt of the planets axis.

Many attempts of the evolution are necessary to come up with intelligent species.

More attempts are necessary to come up with intelligent tool-users.

After a short time (some million years) they will have agriculture then cities then technology then ??? we do not know how fast the civilisations will destroy themselves.

RHABE

nice stuff for the most part Rhabe.... one clarification, one disagreement.

clarification...elements up to iron would be produced all along the stars lifespan, not mostly later....

disagreement. neutron capture either fast or thermal isn't really going to get very far up the chain. sure, occassionally you could get back to back beta decay and move up a little, but alpha decays knock it right back down.

elements above iron are going to result from the extreem pressure temperature in the supernovae explosion shock wave, binding multiple iron or less nuclei... pilsbury dough bisquit squeeze.

benbenben

The color of a star is determined by the temperature of its outer layers, regardless of the chemical content. Current theory says that all young stars burn Hydrogen to Helium, regardless of their masses. More massive stars have higher pressure at their cores, so reactions occur faster, generating more heat. If all young hydrogen-burning stars use the same mechanisms to move heat to the surface, smaller ones will be redder and larger ones will be bluer, even though they all burn the same stuff.

Later in their lives some stars start burning different stuff, and then it's a different story. From observations, it seems that the transition from hydrogen-burning to other elements involves puffing out the outer layers so that they cool.

Current theory says that big blue stars should all be young hydrogen-burners. Small blue stars would be the super-heated remnants of big stars that recently exploded, losing their outer layers. These remnants wouldn't be burning anything at all; they would be glowing with leftover heat from their younger days.

(My avatar is supposed to be a big blue star, but it wouldn't fit.)