Contents
- Preface
1Science and the Universe: A Brief Tour
2Observing the Sky: The Birth of Astronomy
7Other Worlds: An Introduction to the Solar System
13Comets and Asteroids: Debris of the Solar System
14Cosmic Samples and the Origin of the Solar System
18The Stars: A Celestial Census
20Between the Stars: Gas and Dust in Space
21The Birth of Stars and the Discovery of Planets outside the Solar System
27Active Galaxies, Quasars, and Supermassive Black Holes
- AHow to Study for an Introductory Astronomy Class
- BAstronomy Websites, Images, and Apps
- CScientific Notation
- DUnits Used in Science
- ESome Useful Constants for Astronomy
- FPhysical and Orbital Data for the Planets
- GSelected Moons of the Planets
- HFuture Total Eclipses
- IThe Nearest Stars, Brown Dwarfs, and White Dwarfs
- JThe Brightest Twenty Stars
- KThe Chemical Elements
- LThe Constellations
- MStar Chart and Sky Event Resources
- Index
Figuring for Yourself
Figuring for Yourself
In the future, astronomers discover a solid moon around a planet orbiting one of the nearest stars. This moon has a diameter of 1948 km and a mass of 1.6 × 1022 kg. What is its density?
The Moon was once closer to Earth than it is now. When it was at half its present distance, how long was its period of revolution? (See Orbits and Gravity for the formula to use.)
Astronomers believe that the deposit of lava in the giant mare basins did not happen in one flow but in many different eruptions spanning some time. Indeed, in any one mare, we find a variety of rock ages, typically spanning about 100 million years. The individual lava flows as seen in Hadley Rille by the Apollo 15 astronauts were about 4 m thick. Estimate the average time interval between the beginnings of successive lava flows if the total depth of the lava in the mare is 2 km.
The Moon requires about 1 month (0.08 year) to orbit Earth. Its distance from us is about 400,000 km (0.0027 AU). Use Kepler’s third law, as modified by Newton, to calculate the mass of Earth relative to the Sun.