Speed Of Light

All kinds of electromagnetic waves move through empty space at the same speed that is, at the speed of light. The speed of light in empty space, usually symbolized by the letter c, is practically 300,000 km second (186,000 miles per second). The speed of light in empty space has been called the speed limit of the universe, because no known object can be accelerated to move faster. It is one of the most important and precisely measured numbers in astronomy (Appendix 2). A light-year (ly) is the...

The Electromagnetic Spectrum

Visible light is only one small part of all the electromagnetic radiation in space. Energy is also transmitted in the form of gamma rays, X-rays, ultraviolet radiation, infrared radiation, and radio waves. Figure 2.4. The electromagnetic spectrum includes all electromagnetic radiation from shortest, highest-frequency gamma rays to longest, lowest-frequency radio waves. Figure 2.4. The electromagnetic spectrum includes all electromagnetic radiation from shortest, highest-frequency gamma rays to...

Mo

6,000 5,000 3,500 HI TEMPERATURE (K) Figure 5.3. Theoretical tracks of evolution showing luminosity and temperature changes of contracting protostars of different masses. (Contraction times are marked on the tracks.) Approximately how long does it take each of the following protostars to reach zero age main sequence (to be born) (a) stars like our Sun_ _ (b) stars with mass much greater than the Sun's_ (c) stars with mass much less than the Sun's_ Answer (a) About 50 million years (b) about...

Spectral Classes

When you compare the spectra of stars like Polaris or Vega with the Sun's spectrum (Figure 3.8), you see that some look the same while others look quite different. Absorption spectra are used to classify stars into nine principal types, called spectral classes. Hydrogen lines are much stronger in the spectra of some stars than in the Sun's spectrum. Astronomers once mistakenly thought that these stars had more hydrogen than other stars. They classified stars by the strength of the hydrogen...

Info

The Sun is the star closest to Earth. It provides the light, heat, and energy for life. Ancient peoples worshipped the Sun as a life-giving god. Some of the names given to the Sun god were Aton, Apollo, Helios, and Sol. Scientists study the Sun today. It is critical to Earth and is a key to understanding distant stars that cannot be observed in detail. The Sun's total energy output is enormous. The Sun's luminosity L0 is 3.85 x 1026 watts. Solar energy is practically inexhaustible. The amount...

Telescope Enhancements O

Research time is in great demand, so astronomers do not sit at giant telescopes and simply stargaze. Instead, observers usually look at a computer display Starlight, directly or after passing through electronic imaging systems, is recorded for exhaustive study later by many scientists and for obtaining pictures. Powerful computers are vital to the acquisition, archiving, processing, and analysis of astronomical data today. A charge coupled device (CCD) is a popular electronic detector. The CCD...

Dinah L Moch PhD

This book is printed on acid-free paper.' Copyright 1978, 1981, 1987, 1993, 2000, 2004, 2009 by John Wiley & Sons, Inc. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United...

Telescope Design And Selection

Structure Keck Telescope

Nothing will kill your enthusiasm for stargazing faster than a poor-quality telescope with a shaky mount that provides blurry, wiggling images. Large refractors are used where image quality and resolution are most important, as for viewing surface details of the Moon and planets or for observing double star systems. Giant reflectors are used where aperture is most important, as to probe the faintest, most distant objects. They are easier to build and are more cost effective than...

Infrared Astronomy

Infrared astronomy studies incoming radiation with wavelengths beyond visible red to radio. Infrared telescopes were first built in the 1960s. They are basically optical reflectors with a special heat detector at the prime focus. Detectors are shielded and cooled to about 2 K to ensure that they register infrared rays from space, rather than stray heat from people, equipment, and observatory walls. Water vapor and carbon dioxide in the air strongly absorb infrared rays. Large infrared...

F g h

Answer (a) Protostar, gravitational contraction of cloud of gas and dust (b) stable main sequence star, shining by nuclear fusion (converting hydrogen to helium) (c) evolution to red giant when helium core forms (d) red giant, shining by helium fusion (e) variable star, formation of carbon core (f) planetary nebula, enriched hydrogen envelope ejected into space (g) white dwarf, mass packed into star about the size of Earth (h) dead black dwarf in space. A supernova is a gigantic stellar...

The Suns Structure

The chromosphere, from the Greek color ball, is a thin, transparent layer that extends about 10,000 km (6000 miles) above the photosphere. It is normally visible from Earth only during a total eclipse of the Sun, when it glows red due to its hydrogen gas. The temperature unexpectedly increases outward through the chromosphere, where the average temperature of matter is about 15,000 K. The corona, from the Latin crown, is the outermost atmosphere just above the chromosphere. It is a rarified,...

Double Star Systems

Double Stars Orbits

A binary star consists of two stars A and B orbiting a common center of mass, bound together by their mutual gravity. Figure 3.19. A binary star consists of two stars A and B orbiting a common center of mass, bound together by their mutual gravity. A visual binary can be resolved with a telescope so that two separate stars can be seen. Over 70,000 visual binaries are known. Mizar in Ursa Major was the first binary star discovered, in 1650. Beautiful Albireo in Cygnus is a colorful...