ASTR 567: Observational Techniques in Astronomy

ASTR 567: Grading Scheme Start of lecture quizzes………………….. 10% Homeworks……………………………………..25% Highest of two midterm grades……….25% Telescope Proposal………………………….15% Final Exam……………………………………….25%

ASTR 370: Cosmology Offered this semester: Prof. Peterson Early history of the Universe, big bang, inflation, structure formation, dark matter and dark energy

ASTR 561: Galaxies and Large Scale Structure Offered this semester: Prof. Giannios Galactic structure and stellar dynamics, ISM, galaxy formation, galaxy clusters, dark matter.

ASTR 562: High Energy Astrophysics Offered in spring semester: Prof. Lyutikov Physics of exotic objects: neutron stars, white dwarfs, supernovae, black holes, magnetars

ASTR 563: Astroparticle Physics Typically offered in spring semesters Covers neutrinos, cosmic rays, dark matter, gravitational waves

Reading for next time: Lawrence section 1.1.1

Gathering Data in Astronomy What are some ways we gather information about the cosmos?

In Situ Solar system probes Apollo lunar landings Particles with Mass Cosmic rays Neutrinos Meteorites Solar wind Massless Particles Gravitons Photons Gathering Data in Astronomy

Astronomical Techniques – Photometry – Spectroscopy – Polarimetry – Astrometry – Imaging All of these exploit the wave and/or particle properties of E/M radiation All photon-based astronomical measurements can be classified as one or more of:

Electromagnetic Radiation Light exhibits wave-particle duality: – Massless light quanta: photons, carry a specific energy: E = hν = hc/λ h = Planck’s constant = × m 2 kg / s c = speed of light = m / s Light can also reflect, refract, diffract, polarize, and interfere with itself.

Production of E/M Waves Electromagnetic waves are created by accelerating a charged particle E/M radiation emitted from a vertically oscillating magnetic dipole

Production of E/M Waves In the quantum view, a photon is created when an electron jumps to a lower energy state or a free electron binds to an atom.

Production of E/M Waves Other types of quantum transitions that produce photons: Electron spin flip in hydrogen Vibration & Rotation Modes

Production of E/M Waves Nuclear processes can also produce photons: – electron+positron annihilation – nuclear fission and fusion – radioactive decay

E/M Wave Structure E/M wave requires no medium (‘ether’) E and B fields oscillate  to each other, sustaining the wave In a vacuum, wave travels in a straight line (geodesic) at constant speed c = λν

E/M Bands Divisions between bands are approximate: none are officially standardized. Sub-divisions are common e.g., near-IR, far-UV, soft X-ray – near, soft : longer λ – far, hard : shorter λ