At location A there is an electric field in the direction shown by the orange arrow. This electric field is due to charged particles that are not shown in the diagram.
If a proton is placed at location A, which of the arrows below best indicates the direc
Dependent on the Earth
Proper Motion & Tangential Velocity
Independent of the Earth
Size (Diameter, Volume)
1. 2. Find the average distance from the Sun to Pluto in parsecs. Compared to Pluto, how many times farther away from the Sun is Proxima Centauri? The average distance from the sun to Pluto is 39.5 AU (p.157). But 1 pc = 206265 AU (p.421), so the distance
Light has wave-like characteristics.
Emitted light depends upon the object’s temperature.
Light has particle-like characteristics.
The motion of a light source affects wavelengths.
The t t
Th structure of atoms explains why each chemical elem
Main Sequence Stars
Thermal and Gravitational Energy
Two large stores of energy in a star are its internal heat (thermal energy)
and its gravitational energy. The heat stored in a gas is simply the energy
of motion (kinetic energy) of the particles that
Hipparchus [160 - 127 BC]
Hipparchus compiled a catalog of about a
thousand stars in the second century, BC.
He classified them into six categories of
brightness, now called magnitudes.
Recognizing that (a) the response o
Star or Gas?
How Are Stars Born?
The energy radiated by stars comes from thermonuclear reactions, which
consume hydrogen each second and convert it into helium.
The amount of hydrogen i
Spectroscopy is the technique that allows astronomers to decode the
messages contained in starlight. Stellar spectra can tell us the intrinsic
luminosity of a star, how hot it is, how fast it rotates, and its composition.
Observational Testbeds of Stellar Evolution
If stars exist for billions of years but mortals live less than a century,
How are we able to study, derive, and understand Stellar Evolution?
Astronomy is unlike all other sc
Distances and Motions
Determining the AU
Today, the Earth-Sun distance (= 1 AU) is known to high precision from
radar measurements of the distances to the planets. (The relative scale
of the planet distances is known from Copernicus and Kepler.) Radar
26 April 2010
1. What is stellar parallax? What information does it provide? Stellar parallax is the 1/2 the angle the Earth appears to subtend in its orbit about the Sun as seen from a distant start. This is also 1/2 the angle the
from _future_ import division from visual import * # Constants you = 1e-7 qproton = 1.6e-19 scalefactor=8e-0010 # Objects #Change the initial vector position of the proton below: proton = sphere(pos=vector(-3e-10,0,0), radius=1e-11, color=color.red) #Chan
STARS, GALAXIES, AND THE UNIVERSE
Physics 2022 Spring 2012
Lecture Room 3
J. R. Sowell
W102 Physics Building
Office Hours: MWF 10:30 11:00 and Open Door Policy
About half of all stars are binary or multiple star systems
Used to determine stellar masses
Used to determine stellar diameters
Major Types of Binary Stars
The Active Sun
Flares, Coronal Holes
1500 K cooler than the surface
Last for a couple of months
Frequently in groups of 2-20 members
Sizes are usually larger than th
Basic Solar Data
100 times larger than the Earth
One million times as massive as Earth
Surface Temperature ~10,500 F (5,800 K)
10 500 (5 800
Rotates once per month
Is half a degree in size on the sky
Basic Solar Data
PROBLEM SET 1
1. The age of the universe is about 14 billion years. What is this age in seconds? Use powersof-ten notation. 2. At what distance would a person have to hold a European 2-euro coin (which has a diameter of about 2.6 cm) in order
PROBLEM SET 3
1. What is the magnification of a telescope that has an objective with twice the focal length of its eyepiece? 2. The observing cage in which an astronomer sits at the prime focus of the 5-m telescope on Palomar Mountain is abou
PROBLEM SET 4
1. The average distance from the Earth to the Sun is 1.496 x 108 km. Express this distance in light-years. Use powers-of-ten notation. Are light-years useful units for describing distances of this size? Explain. 2. Find the aver
PROBLEM SET 5
1. What temperature and spectral classification would you give to a star with equal line strengths of hydrogen (H) and neutral helium (He I)? Explain. 2. The bright star Rigel in the constellation Orion has a surface temperature
PROBLEM SET 6
1. At one stage during its birth, the protosun had a luminosity of 1000 L and a surface temperature of about 1000 K. What was its radius then compared to today's? 2. Use the Sun's luminosity (3.84 x 1026 W) to calculate the mass
SAMPLE TEST 2 QUESTIONS Physics 2022 Spring 2012
1. A star has an apparent magnitude of +5.6 and a distance of 18 pc. What is its absolute magnitude, M? a. +2.7 b. +1.4 c. -0.9 d. +4.3 e. +2.1
2. The spectral type of Star 1 is A8 and that of star 2 is F0.
SOLUTION SET 1
1. t = 14 x 109 years x 365.25 days/year x 24 hr/day x 60 min/hr x 60 sec/min = 4.42 x 1017 seconds 2. a) b) c) 3. a) b) 4. D = d tan D = d tan D = d tan d = 0.026/2 m / tan (0.5 deg) = 1.5 m d = 0.026/2 m / tan (0.5 deg / 60)
SOLUTION SET 4
1. d = 1.496 x 108 km / 9.46 x 1012 km/ly = 1.58 x 10-5 ly No - too small 2. dpluto = 39.5 AU / 206,265 AU/pc = 1.92 x 10-4 pc dprox_c / dpluto = 1.30 / (1.92 x 10-4) = 6790 3a. 3b. 4. 5a. 5b. 5c. 6a. 6b. d = (2 x 106 AU) / (20
SOLUTION SET 5
1. 2. The two curves cross at about 20,000 K, which is about at the B3-B4 spectral type. Lrigel = 1.6 Tsun Lrigel = 64,000 Lsun
Lrigel / Lsun = (Rrigel / Rsun)2 (Trigel / Tsun)4 (64,000) = (Rrigel / Rsun)2 (1.6)4 Rrigel = 98.8
Lowell 24-inch Telescope
Keck 10-m Telescope
In order for a telescope to be advantageous, it must manipulate light in a
way that is beneficial to the observer. Optimal designs give the observer
(1) a magnified view (so that it
How do we orient objects in the sky?
How do we find objects on the moving sky?
What b t th
Wh t about the moving objects?
bj t ?
How is the Earth (and humans) affected by the sky?
Observations and Theories
The Ancient Greeks and Egyp
Online Astronomy 162
6. [1pt] The gure shows a very simplied version of the structure of the Sun. For each statement below select, in order, the symbol in the picture. Do not use symbols more than once.
Answer Key Version 1
E D C B A G