Astronomy 1020 Stellar Astronomy Spring_2016 Day-13

Course Announcements 1 st “Hot Topics in Science”: Tues. 2/23 6-8pm E106B 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 on Friday, 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.

Accelerating charges (think electrons and protons) produce light – electromagnetic radiation! But, where does light actually come from?

Photons  Light also behaves as a particle.  Photon: particle of light.  Photons carry energy and can have different amounts of energy.  Photons with high energy = light with high frequency.  Photons with low energy = light with low frequency.  Atoms can absorb or emit photons.

Einstein (Nobel Prize) In 1905 Einstein calculated the energy of a particle of light (photon) and proposed the photoelectric effect. E photon = hc/  = h e- photon

 Light moves at 300,000 km/s in a vacuum.  First measured by Rømer when observing Jupiter’s moons.  Speed is slower in other materials, e.g., glass.

 Wavelength ( ): length between crests.  Amplitude: height.  Frequency (f): number of waves that pass by each second.  Period (P): time to complete one cycle.

 A long wavelength means low frequency.  A short wavelength means high frequency.  The speed of light, c, is constant.

 Light is a wave of combined electricity and magnetism, called an electromagnetic wave.  Changing electric and magnetic fields create a self-sustaining electromagnetic wave.

Maxwell – EM Field Theory Scottish physicist James Clerk Maxwell showed mathematically in the 1860s that light must be a combination of electric and magnetic fields.

 Knowing the speed of light and one other variable, either the wavelength or frequency of the light in question, you can find the remaining quantity.  Example: Find the wavelength of the light wave coming from a radio station broadcasting on 770 AM: MATH TOOLS 5.1

Like the flavors of Ice cream – they each provide us with different information. EM Spectrum But what do you get when you put all the flavors (light) together?

Lecture Tutorial EM Spectrum: (pg. 47) 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.