## Supplementary Problems

What is the force of gravity between the Earth and the Sun Ans. 3.52 x 1022N 1.40. If someone weighs 120 pounds on Earth, how much do they weigh on the Moon Ans. 20 pounds 1.41. What is the circular velocity of the Moon Ans. 1,000 m s 1.42. What is the density of the Moon How does this compare to the density of rocks Ans. 3,300 kg m3, about the same as rock 1.43. An asteroid's semimajor axis is 3.5 AU. What is its period Ans. 6.5 years 1.44. How would the gravitational force between two...

## Average Speed Of Particles In A

The particles in a gas are moving in random directions, with speeds that depend on the temperature. Hotter gases have faster particles, and cooler gases have slower particles, on average. The average speed depends on the mass, m, of the particles This equation gives the average speed of the particles in a gas. There will be some particles moving faster than this speed, and some moving slower. If this average speed is greater than 1 6 the escape velocity of a planet, the gas will eventually...

## Escape Velocity Of Venus

In terms of mass and radius, Venus is the most similar to Earth. Venus is about 0.82 Earth masses, and 95 the radius of the Earth. Here, however, the resemblance stops. Perhaps the most poorly understood difference between Venus and the Earth is the sense and rate of rotation. Venus's rotation is retrograde (opposite, i.e., clockwise rather than counterclockwise) to its orbit, and to the orbits and rotations of the vast majority of the rest of the solar system bodies. The rotation is also very...

## Degenerate Gas Pressure

In an ordinary gas, the pressure depends on the density and on the temperature. At very high densities, a mutual repulsion develops between electrons. This repulsion is not due to the classical behavior of their electrical charge rather, it is due to their quantum mechanical properties. This repulsion produces an additional pressure, the so-called degenerate pressure, which depends on the density alone, not the temperature. Thus, the material can be heated without expanding, and can be cooled...

## The Temperature Of Stars

Studies of the absorption lines in star spectra allowed the grouping of similar stars together. The spectral classification led, as our understanding has increased, to a scheme in which stars are ordered by their surface temperature. The spectral classes, from hottest to coolest are OBAFGKM. O stars are the hottest stars and M stars are the coolest stars. Each spectral class is divided into 10 subclasses, 0-9. An 00 star is the hottest, followed by an 01, 02, etc. 09 is just a little bit hotter...

## Solved Problems

What is the peak wavelength of the emission from cool (100 K) dust Recall Wien's law from Chapter 1, which relates the peak wavelength and the temperature A _ 2.9 x 10 3m K Amax _ 100K Am 2.9 x 10 5m The peak wavelength of 100 K dust is about 30 x 10 6m, or 30 microns. This is in the infrared part of the spectrum. 6.2. How do astronomers determine the chemistry of a cool dust cloud As in many other applications, astronomers determine the presence of atoms and molecules in dust clouds from...

## Astronomy

Department of Astronomy University of Washington New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto A Division of The McGraw-Hill Companies Copyright 2002 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a...

## Pluto and Charon

Pluto is the smallest of the planets and fits neither the Jovian nor the terrestrial class. Pluto's orbit is highly inclined, about 17 , to the ecliptic, and has the most eccentric orbit of all the solar system planets. At its farthest, Pluto is 49.3 AU from the Sun at its closest, 29.7 AU, it actually crosses inside the orbit of Neptune. This has led astronomers to believe that perhaps Pluto was an escaped Neptunian moon. Pluto's density is consistent with a composition of rock and ice. The...

## The Interstellar Medium

The interstellar medium (ISM) is the dust and gas between the stars. The interstellar medium is seen as the dark dust lanes in the Milky Way (or in other galaxies), or by its effects on starlight reddening and extinction. It is also observed more directly as reflection or emission nebulae. Approximately 20 of the Galaxy's mass is ISM. The ISM absorbs visible light, but at the same time emits radio waves or infrared radiation. So, while we can't make an accurate map of the distant Galaxy in...

## Escape Velocity Of Spacecraft Solved Examples

What might be a result of a sudden melting of the CO2 ice caps on Mars (Hint melting these caps would release large amounts of CO2 into the atmosphere.) The sudden addition of a large amount of CO2 to the atmosphere of Mars would significantly warm the planet. With no water oceans to cycle the carbon back into rocks, it might seem that there is the potential for a runaway greenhouse effect. However, there is not nearly enough CO2 to actually cause a runaway greenhouse effect. Mars is much...

## Active Galaxies and Quasars

An active galaxy is a galaxy with a nucleus that produces an exceptionally large amount of energy, up to 1015 solar luminosities. This is about 10,000 times the amount of energy produced by the entire Milky Way Galaxy. The spectrum of an active galaxy is quite flat compared with the spectrum of a star, and in many cases contains both broad and narrow emission lines. The luminosity in the radio waves through far-infrared is dominated by synchrotron radiation radiation produced by electrons...

## Escape Velocity Of Sirius B

The total luminosity of the Sun is 4 x 1026 watts. Calculate the total number of watts that fall on a 1 m2 sheet of paper on the Earth's surface. (Recall the inverse square law.) Compare this number to the power output of a standard light bulb. The total luminosity of the Sun is the amount of light emitted by the entire surface area of the Sun. This means that the flux here at Earth is the total power of the Sun, divided by the surface area of a sphere the size of the Earth's orbit 3.80 x...

## The Mass Of Stars

There is a wide variation in the mass of stars. The smallest stars have masses of about 0.08 MSun. Objects less massive than this never begin hydrogen fusion, and so are never technically considered stars. Objects just below the cutoff often emit energy produced by gravitational collapse, and are called brown dwarfs. These objects are brightest in the infrared. The most massive stars known (for example, Eta Carinae) are as large as 150 MSun. In general, more massive main-sequence stars are...

## White Dwarfs

White dwarfs are hot (M0,000K), low luminosity stars composed mainly of carbon and helium. Their luminosity is low because their surface is small. The electrons in white dwarfs are degenerate. As mentioned above the more mass in the white dwarf, the smaller the radius. This peculiar mass-radius relation is shown in Table 9-1. Table 9-1. Mass-radius relationship for white dwarfs Table 9-1. Mass-radius relationship for white dwarfs The largest possible white dwarf mass is 1.4 MSun. This is called...