Astronomy 1021 Chapter Notes - Chapter 1: Scientific Notation, Heliosphere, Astronomical Unit
28 May 2018
School
Department
Course
Professor
Astronomy 1021:
Scientific Notation for Large Numbers
Order of Magnitude Numbers
•Sun’s radius: 7 x 105 km
•Earth’s equatorial radius: 6.4 x 103 km
•Jupiter’s equatorial radius: 7.1 x 104km
•Moon’s equatorial radius: 1.7 x 103
•Ganymede’s equatorial radius: 2.6 x 103 km
Astronomical Distance Measurements
•1 AU (astronomical unit) is Earth’s average distance from the Sun, 150 m km; 1.5 x 108 km;
Pluto’s max orbital distance is 50 AU, Solar system’s edge is 100- 10000 AU
•Sun’s region of influence: voyager reached the termination shock, sun was giving out wind of
material in the Solar system, its really fast, northern lights is sun’s material being ejected and
reading the Earth
•Milky way galaxy: 1018 km; 1.5 light seconds: Moon – Earth, 8 light-minutes: Sun-Earth, 4.5
light hours: Pluto-Earth, 1-2 x 105 light years: Milky way diameter, 2.5 x 106 light years:
Andromeda-Sun, 9.1 x 1010: observable uni diameter
•1 ly (light year) is distance light can travel in one year, 10 trillion km; use it to describe distances
of stars and galaxies; 9.5 x 1015 m; light years also gives the travel time it took for light to cross
that distance
•Father away we look in distance, further back we look in time (b/c light travels in years); ex.
brightest star in the sky (Sirius) is 8 ly away, so we see how it was 8 years ago, not how it is now
