Adopt a GF Blogger ... Slowly

Hi all, I guess I should apologize for being behind schedule for the Adopt a Blogger Event deadline. You see, though, I never could follow directions. Sorry Seamaiden and Stephen (and all of you who want gf df cf coconut yogurt), but it is coming... slowly.... much akin to the progress on my preliminary exam presentation (also known as D-Day for PhD proposals which is this Thursday). I'm getting there, I promise!

Thursday 11:30 am- 3pm Phillips Hall (Physics) The University of North Carolina at Chapel Hill

In the meantime, can I interest you in some astrophysics? Say, perhaps, hydrogen burning in stars? How about my favorite nuclear reaction, proton capture on 22Ne, which is relevant to evolved star (post main sequence) nucleosynthesis. Red giant stars, classical novae, presolar grains, and asymptotic giant branch (AGB) stars are all my playground (well, sorta). Yes, I hear you shout, "I love it - tell me more!" Even if you don't care, it is still a completely kosher gluten free, dairy free, blah blah free post. Does that count?

Cat Eye Nebula, image courtesy of NASA and ESA

The Cat Eye Nebula was an AGB star which has evaporated off its outer layers until its white dwarf core (tiny white dot in center) and expanding layers remain. The expanding layers are ionized by intense UV radiation and fluorescence, as seen here, in a beautiful planetary nebula.

What about the fact that for hydrogen burning in these aforementioned sites, the 22Ne proton capture rate is uncertain by a factor of up to three orders of magnitude?!? If you think that's not a big deal, imagine your credit card or loan debt suddenly being multiplied by a factor of 1000 or more (your debt, not our national debt, that doesn't count; what's the difference between 9 trillion and 9 trill * 1000?). That little problem might prompt you to take some action, perhaps call the credit company. Alternatively, you could also imagine your waistline g r o w i n g by a factor of 1000. Then you'd have BIG problems, pun not intended.

We can't call God and ask what's up with this reaction uncertainty here in physics, so we have to do experiments. That's where I come in (graduate student = cheap labor.) I love life. I aim to measure this astrophysically interesting nuclear reaction at low energies where hydrogen burning in stars takes place. That is, my experiment hopes to reduce those red and blue lines in Fig 1. below.

Fig 1. Current Proton Capture Reaction Rates, relative to NACRE recommended rates, versus stellar temperature. The regions of temperature relevant to hydrogen burning in various astrophysical sites are shaded; the largest uncertainty in the reaction rate dramatically influences AGB star nucleosynthesis (shown in orange shading). The red line indicates the upper limit (rate+uncertainty) where the blue line is the lower limit (rate-uncertainty)

You're probably thinking.. "Sure. You need to remeasure this reaction since you have whopping issues with pinning down the reaction rate. With that red line, it looks like you can't say much about 22Ne+p for AGB stars." I relent and agree. Then I jump up and down and say "Fund me to do this experiment! Please! I'll make you gluten and dairy free cookies. Maybe even coconut yogurt!"

Then you ask "But you haven't proved that this uncertainty really affects red giants and more evolved stars."

"Ah ha! Sorry, I forgot to show you this little gem, Fig 2, which shows that no direct measurements have ever been made at the astrophysically relevant energies. The red line is the Gamow peak which is a fancy thing that tells you the stellar temperature dependent "window" where the star will burn hydrogen. The dotted lines are indirect measurements which make us think that many low energy states exist in this Gamow window, and will thus contribute greatly to the reaction rate. The blue lines are the existing direct measurements (we know those states are there).

Fig 2. Resonance strengths (which are proportional to reaction rates and cross section, in case you're wondering) versus resonance energy. All the resonances (vertical lines) inside the red peak (Gamow window) will strongly affect the 22Ne+p reaction rate, so we need to know them precisely. That is, we need more direct (blue line) measurements inside the Gamow peak (if the resonances are truly there, we'll see...)

You can plainly see we need more blue lines inside the red hump (that's the technical talk) to better understand this reaction and lower the uncertainty in the rate (see Fig 1). If we can do that, maybe we won't be so full of it, if you know what I mean, when we make hydrogen burning on 22Ne predictions in AGB stars and such.

OK, I need to get back to real work or come Thursday (see above), I won't be looking forward to my passing-the-prelim celebration dinner and wine but rather melting into a sobbing mess of failed graduate student who hadn't prepared properly. I'm off to educate myself in the wise ways of nuclear astro. Hopefully this means I won't sound like so much of a moron. Hopefully. Then I can get back to coconut milk yogurt. Sorry all.

And THANK YOU Gluten Free Mommy! For those of you who don't already know, Cindalou's was adopted by Gluten Free Mommy. She made our flourless low carb/Paleo espresso cake (gluten & dairy free) which looks beautiful! Congrats Natalie, I love it. I'll write a more thorough response post-(passing)prelim. I can't wait! We really do need to meet; Carrboro to Raleigh is not too far. Then I can come knocking on your door for some of that Fish Stew of yours :)

Wondering why nuclear astrophysics interests me (or anyone)?

1. look up at the night sky
2. salt your food? The 22Ne+p reaction makes 23Na. Good old table salt is NaCl, so as you season your gluten free dinner think "Cindalou's is helping to measure how much of this stuff is made in stars"... cool
   
3. use a microwave? Thank radar physics research for finding a consumer use for radar technology (no, there were not Samsung or GE microwaves floating in space)
4. use the internet? That might not be a fair question considering this is a blog :) Thank CERN high energy physics research database construction and networking for the net