[GlentoranMark (OP)]

Or did it glow in infrared first and get brighter and brighter?

[lightarrow]

Or did it glow in infrared first and get brighter and brighter?

The second you wrote.

[GlentoranMark (OP)]

Not sure I understand and whether your reply is tongue in cheek  []

Did it start off in infra-red then suddenly sparked into life when nuclear synthesis took place or did it gradually get warmer and warmer?

[Geezer]

I think it's correct to say that eveything takes time, so the Sun did not "switch on" instantaneously. I wonder how long it took to produce the somewhat stable radiation we observe today.

[JP]

There would also be two phases to the sun's birth.  It formed out of a massive cloud of gas that slowly attracted itself to form a star.  As the cloud got smaller and smaller it also got hotter and hotter and would end up emitting mostly infra-red.  If it doesn't have enough mass to start undergoing nuclear fusion, it would stay just a hot massive ball of gas (a brown dwarf).  If it has enough mass, though, it will eventually get hot enough to undergo nuclear fusion and then it will start to brighten and emit visible light.  I don't know how fast it is from the start of fusion until it glows like a start, but if I had to guess, I would guess it's fairly quick, since fusion will tend to make it hotter, which will make it easier for fusion to occur...

[GlentoranMark (OP)]

Thanks for the replies.

When nuclear fusion "kicks in", would the sun suddenly turn on? ie. would there be a massive increase in output of power?

Maybe I'm going around in circles but I can't get my head around it.

[lightarrow]

Thanks for the replies.

When nuclear fusion "kicks in", would the sun suddenly turn on? ie. would there be a massive increase in output of power?

Maybe I'm going around in circles but I can't get my head around it.

1. The hydrogen gas collapse under the gravitational force and begins to heat up, the temperature is maximum in the core.
2. When the core's temperature and density become enough, nuclear reactions starts in the core only, so you still see, from Earth, the IR emission of the outer gas.
3. The energy generated by the nuclear reactions create a force opposing the gravitational collapse, which stops.
4. Now you have a core at millions of kelvin, but you don't see it because of the outer gas. The heat from the core takes time to reach the outer layers, which are swept away because their density is low.
5. When the outer, low density layer is swept away, you start seeing the light from the star's core, but this after some time. If I'll discover how much time, I'll write it here.

[Geezer]

Thanks for the replies.

When nuclear fusion "kicks in", would the sun suddenly turn on? ie. would there be a massive increase in output of power?

Maybe I'm going around in circles but I can't get my head around it.

1. The hydrogen gas collapse under the gravitational force and begins to heat up, the temperature is maximum in the core.
2. When the core's temperature and density become enough, nuclear reactions starts in the core only, so you still see, from Earth, the IR emission of the outer gas.
3. The energy generated by the nuclear reactions create a force opposing the gravitational collapse, which stops.
4. Now you have a core at millions of kelvin, but you don't see it because of the outer gas. The heat from the core takes time to reach the outer layers, which are swept away because their density is low.
5. When the outer, low density layer is swept away, you start seeing the light from the star's core, but this after some time. If I'll discover how much time, I'll write it here.

There you go! I read somewhere recently that it takes a very long time (millions of years?) between fusion and the time when the Sun emits photons. I probably got that wrong, but it was something along those lines.

[lightarrow]

5. When the outer, low density layer is swept away, you start seeing the light from the star's core, but this after some time. If I'll discover how much time, I'll write it here.

They say many thousands of years.

[tommya300]

Or did it glow in infrared first and get brighter and brighter?

An old theory, looking at it in a different way, made me think of a fantasy concept…
Could this have been done to the Sum of the Sun?
Let’s look at the big bang. After the initial ignition caused by the collapsed singularity reaching its critical mass where fusion and fission overcomes its gravity. This event spellerts out matter with great energy in a spherical direction, where this slashing has smaller Gallatic size droplets of instantaneous hot matter that come out in a very hot stream, very close to the speed of light.
 Hence giving it no time to cool to a solid mass and the trailing edge not leaving the hysteresis of the gravity well, the leading point slows enough to arch back (parabolic drift), into this hysteresis gravity well. The gravity well can not diminish at the speed of light nor before it’s total lose of matter. Although, now during all this, the hysteresis gravity well is decaying logarithmically and the stream is still in motion heading for the arch of this, decaying parabolic curve which is at the moment directly influenced by the decaying HGW, (Not H.G Wells - The Man).
After the crest of the arch the head point is now descending back to the faded HGW.  A sudden change in path of this Head is now influence by the lagging edge of the stream making the head fold into its tail. Now a new center core is being born just below the speed of light and it contains the hot gasses already established and we can say this spiral affect is the same as a snowball going down a snowy path gathering its own debris and increasing that gravity relationship to that point to sustain that nuclear chain reaction creating that yen and yang.
I say fantasy where I shouldn't because this concept has been published somewhere as science fact, which particially discribes a binary system.

 [ Invalid Attachment ]  
 [ Invalid Attachment ]

[Ophiolite]

The sun likely began as a T-Tauri type star. These are pre-main sequence stars powered, as noted above, primarily by gravitationl collapse energy. These stars have several characteristics: extremely variable in luminosity; powerful X-ray and radio transmitters; generators of very powerful stellar winds; accompanied by protoplanetary discs.
Their move to the main sequence, where stable hydrogen fusion begins takes up to 100 million years, depending upon their mass.