PHYS 1060: Introduction To Stellar and galactic astronomy. 1.Syllabus, Expectations, Guidelines. (I.e.; how not to screw up!) 2.Course content, Table of Contents 3.Course expectations. (We’ll see..) Dr. Deborah Leddon

Useful Stuff we need to know from the first 2 chapters. Distances, scale and measurements

Size Is Everything Since Astronomy is the study of the Universe, we define the Universe to be the totality of all space, time, matter and energy. Consider the big picture!

Terms and definitions Star: a glowing ball of hot gas held together by it’s own gravity and powered by atomic fusion processes within its core. Constellation: A grouping of stars into a recognizable pattern in the night sky, a human convention only, actually has nothing to do with whether the stars are gravitationally bound together in a cluster. Star Cluster: A grouping of stars from about a dozen to a million in number. Formed from the same gas cloud. Light year (ly): distance light travels in a year

More stuff to know. Since we see stars in this manner: It is useful to consider extending this concept to …… 1,000 light-years

Celestial Sphere You will use Celestial sphere coordinates to find deep space objects such as stars and galaxies. The celestial analogs of latitude and longitude are respectively, Declination and Right ascension.

Celestial Sphere Definitions & Concepts Declination (δ, dec) (0 - ±90 0 )  latitude Right Ascension (α, RA) (0h0m – 23h59m)  longitude Example: Betelgeuse celestial coordinates are: 5h 52m 0s Rigel: 5h 13 m 36 s Celestial equator  equator Constellation labeling: Sirius – Canis Major: α Cma Rigel: β Ori ( more examples: A-7 )

Chapter 2. Revolutions and Laws History Scientific Method Laws: a.Kepler’s Laws b.Newtonian Physics

Distance and definitions 1 A.U. is the distance from the Earth to the Sun. 1 A.U. = 1.5 x 10 8 km. Again, 1 ly (light-year) = 6 trillion miles (9.46 x km). 1 pc (parsec) = 3.3 ly (our closets star, Alpha Centauri is 1.33 pc) 1 mile = km. 1 arc degree (1 0 ) = 60 arc minutes. 1 arc minute (1 ’ ) = 60 arc seconds (1”). There are 3600 arc seconds in 1 degree. Lets see how to use these in stellar distances 

Angular Measure section 1.5 of your text 360 arc degrees (360 0 ) in a full circle. 1 arc degree (1 0 )1 arc minute (1’) 1 arc second (1”)

Stellar distances The apparent displacement of a foreground object relative to its background is known as Parallax. Earth 6 months later If this angle is 1 arc sec (1”) _ the star is at a distance of 1 parsec [parallax in arc second] 1 AU The ‘star’ Distance (in parsecs) = 1 parallax (arc secs.) 1 parsec = 3.3 ly (light-years)

Stellar distances (2) Distance (in parsecs) = 1 parallax (arc secs.) Using: Problem: An object with a parallax of 0.5” lies at a distance of 1/0.5 = 2 pc Note: with most telescopes (and lots of effort) direct parallaxes are possible out to pc (0.1 to 0.02 arcsec). (Page 439)

History and Scientific Revolutions Stonehenge, 2800 B.C.E. Geocentric Universe Aristotle: BCE Ptolemy: 140 AD Heliocentric Universe Aristarchus BCE Copernicus: late 1400 – early 1500 Galileo: Tycho Brahe: J. Kepler:

Scientific Method A theory is a framework /paradigm/picture of ideas and assumptions used to explain observations and make predictions. It is continually tested. If experiments and observations explain it – Great!, if not then move on to another one that explains things better. The Scientific method is a process (with no end point) combining theory, observations/tests, predictions. Hypothesis: a possible explanation  theory

Rules, rules and more rules ….. The laws of Planetary motion: Kepler and Newton Kepler’s Laws 1. The orbital paths of the planets are elliptical with the sun at one focus. e: eccentricity a: semi-major axis a Lets see table 2.1, page 47

Kepler’s 2 nd & 3 rd laws 2. An imaginary line connecting the Sun to any planet sweeps out equal areas of the ellipse in equal intervals of time. 3. The square of a planet’s orbital period is proportional to the cube of its semi-major axis P 2 = a 3 Where P = planet’s year Kepler’s laws are universal

Newton’s Laws Newton’s 3 laws Law of gravitation Centripetal motion

Newton’s universe 3 laws Gravitational law Gravitational and Kepler’s laws