PHYS 420: Astrophysics & Cosmology

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1 PHYS 420: Astrophysics & Cosmology

2 Dr Richard H. Cyburt Assistant Professor of Physics My office: 402c in the Science Building My phone: (304) My My webpage: In person or is the best way to get a hold of me.

3 My Office Hours TR 5:30-17:00am W 5:00-5:00pm Meetings may also be arranged at other times, by appointment

4 Midterm 1 Thurs. Feb 9, 4-5:15pm Cosmic Perspective & Scientific Method(s) History & development of Modern Science & Cosmology Information from Light Building Blocks of the Universe

5 No Class Thur, Feb 2 In the meantime. Homework: From all we have discussed so far, think of questions and topics you are particularly very interested in. Pick 2 questions or topics you are interested in and would like to use for a possible project. Write a paragraph or two on why you are interested and the kinds of question you have or hope to address. What experiments and/or observations do you think are relevant?

6 Douglas Adams Hitchhiker s Guide to the Galaxy

8 What is the Universe made of?

Oxygen Neon Sulfur Nitrogen Magnesium Iron Silicon 10

9 Nuclide Properties Cosmic Composition 1 Hydrogen Helium Carbon Relative abundance Oxygen Neon Sulfur Nitrogen Magnesium Iron Silicon Boron Lithium Beryllium Atomic number

10 Chart of Nuclides All nuclei made of neutrons and protons The strong force holds these nucleons very tightly packed. The ground state of nuclei has neutrons and protons that are basically uniformly packed into a sphere. The liquid-droplet model works great! There are deviations showing more complicated underlying structure(s).

11 Chart of Nuclides All nuclei made of neutrons and protons The strong force holds these nucleons very tightly packed. The ground state of nuclei has neutrons and protons that are basically uniformly packed into a sphere. The liquid-droplet model works great! There are deviations showing more complicated underlying structure(s). Z-fixed = isotope

12 Chart of Nuclides All nuclei made of neutrons and protons The strong force holds these nucleons very tightly packed. The ground state of nuclei has neutrons and protons that are basically uniformly packed into a sphere. The liquid-droplet model works great! There are deviations showing more complicated underlying structure(s). N-fixed = isotone

13 Chart of Nuclides All nuclei made of neutrons and protons The strong force holds these nucleons very tightly packed. The ground state of nuclei has neutrons and protons that are basically uniformly packed into a sphere. The liquid-droplet model works great! There are deviations showing more complicated underlying structure(s). A-fixed = isobaric

14 Pick out the most stable isotope for each Z

15 Nuclei enjoy being in lowest energy state Strong force tells us which Nuclide is most stable for a given A Weak force tells us how we decay

16 Excited States Atoms absorb/emit radiation transitioning from one state to the another. Collisions with other atoms or electrons can excite/de-excite atoms EM radiation (a.k.a. light) can excite/de-excite atoms (infared, visible, ultraviolet) Nuclei also can have excited states Collisions of nuclei with other particles can excite/de-excite nuclei EM transitions (a.k.a. light) can excite/de-excite nuclei (gamma) Weak transitions can excite/de-excite nuclei (np-interconversion with release of e ± & υ)

17 Excited States Lightest Nuclei have no excited states!! Nucleons=n,p are basically the same particle (as seen via the strong force) H 2,3, He 3 He 4 first excited state is ~20 MeV above ground state energy What does this mean?

18 Atoms, molecules and nuclei Atoms stick together to make molecules The binding of atoms together (sharing of electrons) does not fundamentally change atoms The EM force binding electrons to atoms is relatively weak Nucleons stick together to make nuclei The binding of nuclei is very strong and greatly affects its building blocks

19 TUNL Nuclear Data Evaluation

20 These are similar to molecular states He 4 = H 3 +p He 4 = He 3 +n He 4 = H 2 +H 2 TUNL Nuclear Data Evaluation

21 He 4 is the most tightly bound light nucleus It is so tightly bound that 2 a particles are more stable than the ground state of Be 8 This is called particle unstable: It is easy and preferable to simply break into smaller stable nuclei There are no other mass=8 nuclei that are even this close to being bound or rather UNBOUND!! These are similar to molecular states Be 8 = He 4 + He 4 2 He 4 are more bound by only 92 kev! TUNL Nuclear Data Evaluation

22 TUNL Nuclear Data Evaluation

23 These are similar to molecular states Be 8 + He 4 = He 4 +He 4 + He 4 TUNL Nuclear Data Evaluation

24 This excited state is very close to the triple a ground state * C 12 = He 4 +He 4 + He 4 These are similar to molecular states Be 8 + He 4 = He 4 +He 4 + He 4 This excited state is called the Hoyle state Was predicted to exist before observed. TUNL Nuclear Data Evaluation

25 Why do you think so?

26 Zooming into the Chart Z N

27 No stable Mass = 5 or 8 Z N

28 Hoyle state Central Temperature of Sun 1.571x10 7 K = 1.34 kev Stars burning all central H, contract and heat up to ~10 8 K = 10 kev If state didn t exist, the probability of forming a C 12 excited state is basically 0 Was predicted to exist before observed. because we exist!!!! TUNL Nuclear Data Evaluation

29 What are your thoughts?

30 Particle Discoveries

31 Particle Discoveries (We need to organize this better!!!)

32 Radiation & Particles RADIATION Electromagnetic Visible light Heat rays = infared Chemical rays = ultraviolet X-rays Gamma rays Weak b-rays Strong a-rays, fission PARTICLES Electron (e $ ) Positron (e % ) Proton (p) Negatron or Anti-proton (p ) Neutron (n) anti-neutron (n)) Muon (μ ± ) neutrinoss (n) Pion (π ±, π - ) Kaon (K ±, K - ) Lambda (Λ - ) Delta ( %%, %, -, $ )

33 Particles LEPTONS (NO, STRONG INTERACTION) Electrons Muons Neutrinos HADRONS (YES, STRONG INTERACTION) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n)) Pion (π ±, π - ) Kaon (K ±, K - ) Lambda (Λ - ) Delta ( %%, %, -, $ )

34 Hadrons MESONS (LIGHTER THAN PROTON) Pion (π ±, π - ) Kaon (K ±, K - ) BARYONS (= OR HEAVIER THAN PROTON) Proton (p) anti-proton (p ) Neutron (n) anti-neutron (n)) Lambda (Λ - ) Delta ( %%, %, -, $ )

35 Does this help?

PHYS 420: Astrophysics & Cosmology

PHYS 420: Astrophysics & Cosmology Dr Richard H. Cyburt Assistant Professor of Physics My office: 402c in the Science Building My phone: (304) 384-6006 My email: rcyburt@concord.edu My webpage: www.concord.edu/rcyburt