Protostar to Star

[weeman]

I was watching a show tonight about our Sun. They were talking about our solar system's early formation, and when the Sun went from protostar to a full fledged star. They said that the process happens within just a few seconds, giving off an instant flash of incredibly bright light and cataclysmic energy.<br /><br />Is this true? When the star reaches the point where nuclear fusion finally ignites, is it a very fast process like this? <br /><br />Almost as if the star reaches the exact temperature needed for nuclear fusion, then BOOOOOOM!! It becomes a fully operational star! <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[docm]

That about covers it. <br /><br />Sure would be cool to watch, at a "safe" distance of course. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

Also, IIRC, it takes a long time (thousands of years) for the fusion energy to make it's way to the surface where it can be radiated away is space. Stars are very dense, or they wouldn't be stars <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[yevaud]

Exactly correct. A T-Tauri star goes through, well, the T-Tauri phase. It's not an event, it's an evolution.<br /><br />Some interesting relevant articles on T-Tauri stars:<br /><br />T-Tauri stars and evidence for Planetary formation<br /><br />On Disc Braking of T-Tauri rotation<br /><br />I think a simple read of the two abstracts speaks of a wealth of observational data available today on Protostar evolution. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[weeman]

<font color="yellow"> Also, IIRC, it takes a long time (thousands of years) for the fusion energy to make it's way to the surface where it can be radiated away is space. </font><br /><br />That is also what I had in mind, Wayne. I know that the energy released from the Sun's core can take a long time to reach the surface. The journey from the Sun's core to the photosphere can take hundreds of thousands of years. <br /><br />Most of the energy released is in the forms of photons. Although photons travel at the speed of light, they can't make a straight shot out of the Sun's core; their path zig zags all over the place as they bounce off of electrons in the Sun's dense plasma.<br /><br />So, I figure that even when nuclear fusion begins in the Sun, it must take thousands to hundreds of thousands of years to actually see the results. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[docm]

Let's not forget the brown dwarf/star cutoff which is about 0.080 Sol mass. <br /><br />Below this point no thermonuclear ignition and you get a brown dwarf, but above it you get a proper star; in most cases a small star which ignites rapidly through its thin layers and small radius. Poof. Fast, and small stars like this make up the vast majority of stars; red dwarfs etc. <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

umm, I believe Red Dwarves are the longest lasting stars in the Universe, since they burn their fuel so slowly <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[docm]

Exactly. From billions to trillions of years depending on the mass; the lower the mass the longer its lifespan. The tiny ones will probably be the last lights to go out when the party's over. <div class="Discussion_UserSignature"> </div>

 

[nexium]

With a radius of 50,000 miles plus I can't picture anything other than neutrinos happening in seconds. Transparent, perhaps compared to the opaque of our present sun, but I picture the photons taking years, instead of seconds, to get from the core to the photosphere even before fusion begins.<br />How transparent is Jupiter 90 miles below the cloud tops?/ Why do we expect a protostar to be more transparent than Jupiter?<br />Also I picture fusion beginning in a tiny spot in the core and spreading outward at 1/10 c, or much slower to cover a few cubic miles for a 0.08 solar mass protostar. It may take millions of years for the mass to reach one or two solar masses after the fusion begins. This is partly because the intense solar wind of the protostar tends to repel infalling matter.<br />A protostar may have double the luminosity that it will have later as a main sequence star, but my guess is incredibly bright is an exaggeration. Neil

 

[yevaud]

Yes.<br /><br />The Protostar is effectively transparent to Neutrinos produced when Fusion is initiated. However, they do have some bearing on heating of surrounding material (helping to blow it away from the Protostar), if it's dense enough. This effect is most profoundly seen during a Supernova's first few seconds. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[weeman]

I agree with what you're saying. Neutrinos would accelerate out of the star's core at the speed of light, correct? Neutrinos are very hard little things to catch. Neutrinos rarely interact with other subatomic particles; they don't interact like electrons do with protons, and so on.<br /><br />For example, about an inch of a slab of lead can stop an X-ray, but to stop an average neutrino, it would require a slab of lead over a lightyear thick! <br /><br />This is why scientists, in underground neutrino observatories, can typically catch just one electron neutrino in about a day. However, in a given day, there is easily thousands of trillions of neutrinos passing through the observatory. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>

 

[yevaud]

Under normal conditions, this is true. But when the intervening material is quite dense, and the neutrino flux is high, interaction <i>does</i> occur in a significant way.<br /><br />http://www.phy.ornl.gov/tsi/pages/sn.html <br /><br />As I'd mentioned, it's a similar mechanism. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[weeman]

Thanks for the interesting link, although this topic is a little over my head <img src="/images/icons/tongue.gif" /> <br /><br />However, I ALWAYS want to learn new things. I have always been fascinated with the characteristics and fundemental laws of supernovae. It is a field of study that I am reading about more and more all the time. <div class="Discussion_UserSignature"> <p> </p><p><strong><font color="#ff0000">Techies: We do it in the dark. </font></strong></p><p><font color="#0000ff"><strong>"Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.</strong><strong>" -Albert Einstein </strong></font></p> </div>