How the Sun ShinesZachary Robinson

Phys 406

What creates the sun’s energy?◦ Composition of Sun◦ Fusion in the Sun (and other stars)

Creation of the elements Studying the sun with helioseismology

◦ What is it?◦ How is it used?

Studying the sun through neutrino detection◦ Solar neutrino problem◦ SNO

Overview

74% Hydrogen 24% Helium 2% Trace Elements

Composition of the Sun

http://www.nasa.gov/images/content/449080main_img_feature_1650_4x3_946-710.jpg

Major Fusion Reaction in Sun

Hydrogen Recycling:

Images from: http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/

More Fusion in the Sun

Images from: http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/

The CNO Cycle

http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/

Positron

Video from NOVA’s “Origins” mini-series: http://www.youtube.com/watch?feature=pla

yer_embedded&v=neMEo8ZrwuI

Creation of the Elements via Fusion

What is it?◦ Study of the interior of the sun via observations of

sound waves on its surface How does it work?

◦ Sun acts as a spherical resonant cavity for acoustic waves

◦ Oscillations from acoustic waves result in small Doppler shifts of spectrum lines

Helioseismology

How is it used?◦ By numerically solving solar models we can

determine information about the sun For example: Solar structure, chemical composition,

temperature at different depths

Helioseismology

http://www.stat.berkeley.edu/~stark/Seminars/Aaas/helio.htm

Detecting the proper amount of neutrinos from the sun would verify fusion theories

Solar Neutrino Problem (SNP):◦ Solar neutrino measurements

have yielded inconsistent and perplexing results

◦ Presently the measured flux of neutrinos is significantly less than the expected output from the sun’s fusion reactions! SAGE and GALLEX detect only 60

to 70% of expected

Neutrino Detection

http://www.chemistry.bnl.gov/SciandTech/SN/

The sun’s reaction mechanisms are not correctly understood◦ This would be a huge blow to models which have

otherwise been very successful◦ No satisfactory modifications have been proposed

Experiments could be performed incorrectly Reaction rates in the Sun could be lower

than calculations predict Something could happen to the neutrinos in

transit to earth…

Explanations for the SNP

Three types of neutrinos:◦ Electron, muon, tau

The sun should only produce electron neutrinos

Until recently, neutrino detectors could only detect electron neutrinos

MSW effect: Sun’s high mass densities enhance the flavor oscillations of neutrinos

Neutrino Flavors

conferences.fnal.gov

Detector that could detect all three flavors

Built 6800 feet underground in Canada

Cherenkov detector using 1000 metric tons of heavy water (D2O)

All air, water, and materials in detector are extremely pure to reduce background noise from radioactive elements

Collecting data since 1999

Sudbury Neutrino Observatory (SNO)

http://www.sno.phy.queensu.ca/images/man_on_deck.GIF

"Fusion Process of the Sun." Grant Chronicles. GrantChronicles.com, 2009. Web. 28 Nov 2011. <http://www.grantchronicles.com/astro01.htm>.

Guenther, D.B. "Age of the Sun." Astrophysics Journal. 339. (1989): 1156-1159. Print.

Graps, Amara. "Helioseismology." Stanford.edu. Stanford University, 19 Feb 2009. Web. 6 Dec 2011. <http://soi.stanford.edu/results/heliowhat.html>.

"How the Sun Shines". Nobelprize.org. 30 Nov 2011 http://www.nobelprize.org/nobel_prizes/physics/articles/fusion/

Stark, P.B.. "Sounding the Sun: Helioseismology." AAAS Seminars. University of California, Apr 2011. Web. 3 Dec 2011. <http://www.stat.berkeley.edu/~stark/Seminars/Aaas/helio.htm>

Strobel, Nick. "Neutrino." The Sun and Stellar Structure. AstronomyNotes.com, 12 Jun 2010. Web. 3 Dec 2011. <http://www.astronomynotes.com/starsun/s4.htm>

"The SNO Homepage." The Sudbury Neutrino Observatory. The SNO Institute, 21 Apr 2011. Web. 24 Nov 2011. <http://www.sno.phy.queensu.ca/>.

Sources