Astronomy 1020 Stellar Astronomy Spring_2016 Day-14

Course Announcements 1 st “Hot Topics in Science”: Coming Soon Topics this semester are: Human Cloning, Environmental Toxicology, & Fracking … includes pizza. Dark Night Observing: Mon. 2/29 & Wed. 3/2 – 7:30pm at the APSU Observatory Exam-2 – Fri. 3/4 Chapters 5 & 6 Smartworks Chapters 5 & 6: Due Fri. 3/4 Spring Break Mar (Sat.-Sun.) APSU Research and Creativity Forum April 15, 2016 Abstracts are due: 4:00pm Fri., March 18 Feb. 29 – Last day to drop with an automatic “W” Apr. 1 – Last day to drop a class with W, F, FA

Course Announcements Colloquium TODAY, Feb. B310 Dr. David James, Cerro-Tololo InterAmerican Obs. Open Clusters, Stellar Evolution and Calibrating the Ages of Stars: Blanco 1 Galactic open clusters are laboratories, provided by nature, for us to study stellar evolution. Using 1m-, 4m- and 8m-class telescopes, I will show how spectroscopic and photometric observations of solar-type stars in open clusters allow us to establish a stellar chronometer, and create an age-ranking system for an ensemble of nearby, well-studied clusters. With the aid of new observations of Blanco 1, an high-Galactic latitude, Pleiades-age cluster, I will show how deriving stellar age must be based upon very high quality observational data and a diverse range of stellar models.

 Visible spectrum: small range of wavelengths that humans can see.  Red light = longest wavelength ( ~ 750 nm).  Violet light = shortest wavelength ( ~ 380 nm).  “Roy G. Biv.”

 Visible light is just one small part of the electromagnetic spectrum: Gamma rays X-rays UV Visible IR Microwave Radio increasing increasing f decreasing

Concept Quiz—AM and FM On the FM dial, the frequencies run from 88 to 107 MHz (million cycles per second). On the AM dial, the range is 570 to 1600 kHz (thousand cycles per second). Which statements are true? A. FM photons have shorter wavelengths than AM. B. FM photons have higher energies than AM. C. FM photons travel at the same speed as AM. D. All the above statements are true.

 Atoms have a dense nucleus of protons and neutrons.  Electrons surround the nucleus in a “cloud.”

 Electrons can have certain energies; other energies are not allowed.  Each type of atom has a unique set of energies.  Energy level diagram represents this.  Lowest energy is the ground state.

 Emission: An electron emits a photon and drops to a lower energy state, losing energy.  The photon’s energy is equal to the energy difference between the two levels.

 Absorption: An electron absorbs the energy of a photon, moving the electron to a higher energy level.  The photon’s energy has to be equal to the energy difference between the two levels.

Concept Quiz—Energy Levels In the energy level diagram, transition B has half the energy of transition A. What is the wavelength of emitted light? A. 225 nm B. 450 nm C. 900 nm A: = 450 nm B: = ?

Lecture Tutorial Light & Atoms: (pg. 65) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.

 The spectrum of a cloud of glowing gas contains emission lines.  When viewed through a cloud of gas, a continuous spectrum will have absorption lines.

Lecture Tutorial Types of Spectra: (pg. 63) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group.