About site: Astronomy/Stars/Neutron Stars - Neutron Stars and X-ray Binaries

About site: http://chandra.harvard.edu/xray_sources/neutron_stars.html

Title: Astronomy/Stars/Neutron Stars - Neutron Stars and X-ray Binaries An accessible summary of neutron stars and X-ray binaries, presented by the Chandra X-ray Observatory. Includes a comprehensive Q&A section and a selection of quality images.

Princeton_Pulsar_Group Princeton University's site on pulsars, including a definition of pulsars, multimedia and telescopic images, and links to other web data.

Pulsar_Physics Provides technical descriptions of pulsars - focussing on neutron stars, gamma ray pulsars and polar cap or outer gap gamma-ray emission.

Radio_Pulsar_Newsletter Radio pulsar abstracts published by the University of Sydney's Research Centre for Theoretical Astrophysics.

Summaries_of_Neutron_Star_Types Includes short summaries on neutron stars, including information on pulsars, neutron degeneracy, pulsar examples, binary pulsars and planets around pulsars. This information links to a useful navigabl

A_Tutorial_on_Radio_Pulsars A tutorial from the Australia Telescope National Facility, Parkes, New South Wales

Windows_to_the_Universe__Neutron_Stars A typical neutron star is the size of a small city, but it may have the mass of as many as three suns.

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X-ray_Astronomy__Neutron_Stars Brief description of neutron stars.

Angiosperm_Phylogeny Phylogenetic trees, technical descriptions of all orders and families, references, and links. By Peter Stevens of the Missouri Botanical Garden.

Angiosperms_Image_Gallery Extensive collection, organized by family.

The_Families_of_Flowering_Plants A taxonomical database with descriptions and illustrations of each family, and an interactive key to families.

Flowering_Plant_Gateway Various paths for exploration or comparison of four major flowering plant classification systems (Cronquist, Takhtajan, Thorne and the Angiosperm Phylogeny Group system). From Texas A&M University

OSU_Seed_Biology_Program_-_SeedID_Index Photographs of the seeds of selected plants.

CPC_-_La_Niña_Coverage Regularly updated discussion and coverage of the La Niña weather system including global and regional impacts and forecasting.

CPC_El_Niño/Southern_Oscillation_(ENSO) Coverage of the 1997/98 El Niño weather system from the Climate Prediction Centre, including forecasts, historical info, and the impact of the system on weather patterns.

El_Niño_and_La_Niña__Tracing_the_Dance_of_Ocean_and_Atmosphere National Academies popular article describes the basic scientific research that led to our current understanding of these weather phenomenon.

El_Niño/La_Niña_Watch Archive of images and news releases about observations of the El Nino/La Nina phenomenon in the Pacific Ocean by the U.S./French TOPEX/Poseidon, Jason-1, and other NASA/JPL satellites and instruments.

The_Potential_Use_and_Misuse_of_El_Niño_Information A workshop report from the Environmental and Social Impacts Group. Includes compilation of documents including an executive summary and a glossary.

What_is_an_El_Niño? Illustrated explanation with realtime graphics and animations of data from the tropical Pacific Ocean. From NOAA.

What_is_La_Niña? Illustrated explanation with realtime graphics and animations of data. Also numerous links to reference material from NOAA.

Atlas_of_the_Moon Interactive Moon atlas (hotspots) with links to 237 close-up images. [Also in German]

The_Captive_Moon Offers overview article including exploration history and cultural history.

Dyson\'s_Animated_Moon Interative moon map (Flash based) with brief information about various features.

Earth-Moon_Dynamics_Page Extracts from five papers studying Earth-Moon dynamics relating to evolution and gravity topics.

Geologic_Lunar_Research_Group Resource for all lunar observers interested in geologic, dome and TLP research. Some content in Italian.

Google_Moon A photographic map of the equatorial region with pan and zoom capability, showing locations of the Apollo landings.

Interactive_Map_of_the_Moon The visible and the hidden side. Includes games and basic information about the satellite and the lunar missions.

Keith\'s_Moon_Page A collection of facts, phases, folklore and photographs.

Lunar_Volcanoes An Introduction to Lunar Domes by Nigel Longshaw, an illustrated description of these features including characteristics and observation history.

Lunarsat_Info_Page Multimedia presentation of the European space mission to investigate the south pole for its suitability for the first permanent human outpost.

The_Moon_Illusion_Explained Why our satellite looks big at the horizon and smaller when higher up.

The_Moon_Museum A tour made on the 30th anniversary of the first lunar landing.

Moon_Page Some facts, quotations, trivia chosen at random.

Moon_Stereogram_Demonstration Demonstration as to why the Moon appears larger when nearer the horizon than when high in the sky.

Moon_Survey Tips for observing our satellite and drawing lunar features. Data archive, pictures, movies and selected links also available.

MoonBase7 Facts, missions, phases, news, links. Also dedicated to the space in general and robotics.

NSSDC_Photo_Gallery__Moon Select images from various space probes and telescopes.

The_Origin_of_the_Moon Scientific research report providing overview of current theories.

SMART-1__ESA\'s_Mission_to_the_Moon Official mission site includes articles, images, FLASH presentation, PDF brochures, etc.

Summer_Moon_Illusion An explanation of the illusion that the Moon, low on the horizon, is actually bigger then when seen higher in the sky.

What\'s_a_Blue_Moon? From Sky and Telescope magazine. Explains what it is and when the phenomenon happens.

Woman_in_the_Moon Several features of lunar landscape combined can be seen as a profile of a woman.

April_3_1974 Details on the Super Outbreak of Tornadoes that spawned 148 tornadoes, including thirty F4's and six F5's, in one day.

Bangladesh_and_East_India_Tornado_Prediction_Page A climatology of tornadoes for east India and Bangladesh, and the daily prediction of tornadoes are provided. Surface and upper air charts for historical tornado cases for Bangladesh and India are pr

The_Disaster_Center_Tornado_and_Severe_Weather Tornadoes, weather watchers, fact sheet statistics for every state, and links to the Disaster Center states pages.

FEMA_-_Fact_Sheet_-_Tornadoes Tornado safety tips from the Federal Emergency Management Agency.

How_Stuff_Works__Tornado Illustrated basics about tornadoes and how they are rated.

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Chandra :: Field Guide to X-ray Sources :: Neutron Stars/X-ray Binaries Chandra X-ray Observatory

An overview of the Chandra mission and goals, Chandra's namesake, top 10 facts. Classroom activities, printable materials, interactive games & more. Overview of X-ray Astronomy and X-ray sources: black holes to galaxy clusters. All Chandra images released to the public listed by date & by category Current Chandra press releases, status reports, interviews & biographies. A collection of multimedia, illustrations & animations, a glossary, FAQ & more. A collection of illustrations, animations and video. Chandra discoveries in an audio/video format. About Chandra Education Field Guide Photo Album Press Room Resources Multimedia Podcast search

Field Guide HomeX-ray Astronomy History Major Milestones X-ray Universe X-rays & Light VS. Medical X-ray X-ray Absorption Galactic Navigation Dark Matter X-ray Sources Solar System Stars White Dwarfs Supernovas Neutron Stars Black Holes Galaxies Quasars & AGN Galaxy Clusters X-ray Background Brown Dwarfs Gamma Ray Bursts Web ShortcutsChandra BlogRSS FeedChronicleEmail NewsletterNew & NoteworthyImage Use PolicyQuestions & AnswersGlossary of TermsDownload Guide More Information Chandra Images: Neutron Stars Printable Field Guide: Neutron Stars Questions & Answers: Supernova Remnants and Neutron Stars More: SCO X-1 Neutron Stars/X-ray Binaries

Chandra image of the Vela Pulsar Ordinary matter, or the stuff we and everything around us is made of, consists largely of empty space. Even a rock is mostly empty space. This is because matter is made of atoms. An atom is a cloud of electrons orbiting around a nucleus composed of protons and neutrons. The nucleus contains more than 99.9 percent of the mass of an atom, yet it has a diameter of only 1/100,000 that of the electron cloud. The electrons themselves take up little space, but the pattern of their orbit defines the size of the atom, which is therefore 99.9999999999999% open space! What we perceive as painfully solid when we bump against a rock is really a hurly-burly of electrons moving through empty space so fast that we can't see—or feel—the emptiness. What would matter look like if it weren't empty, if we could crush the electron cloud down to the size of the nucleus? Suppose we could generate a force strong enough to crush all the emptiness out of a rock roughly the size of a football stadium. The rock would be squeezed down to the size of a grain of sand and would still weigh 4 million tons! Such extreme forces occur in nature when the central part of a massive star collapses to form a neutron star. The atoms are crushed completely, and the electrons are jammed inside the protons to form a star composed almost entirely of neutrons. The result is a tiny star that is like a gigantic nucleus and has no empty space. Neutron stars are strange and fascinating objects. They represent an extreme state of matter that physicists are eager to know more about. Yet, even if you could visit one, you would be well-advised to turn down the offer.

The Crab Nebula The intense gravitational field would pull your spacecraft to pieces before it reached the surface. The magnetic fields around neutron stars are also extremely strong. Magnetic forces squeeze the atoms into the shape of cigars. Even if your spacecraft prudently stayed a few thousand miles above the surface neutron star so as to avoid the problems of intense gravitational and magnetic fields, you would still face another potentially fatal hazard. If the neutron star is rotating rapidly, as most young neutron stars are, the strong magnetic fields combined with rapid rotation create an awesome generator that can produce electric potential differences of quadrillions of volts. Such voltages, which are 30 million times greater than those of lightning bolts, create deadly blizzards of high-energy particles. Rotation-powered pulsars These high-energy particles produce beams of radiation from radio through gamma-ray energies. Like a rotating lighthouse beam, the radiation can be observed as a pulsing source of radiation, or pulsar. Pulsars were first observed by radio astronomers in 1967. There are now approximately 1000 known pulsars. The pulsar in the Crab Nebula, one of the youngest and most energetic pulsars known, has been observed to pulse in almost every wavelength—radio, optical, X-ray, and gamma-ray. A few dozen pulsars are observed to pulse in X-rays and six are seen to pulse in gamma-rays. Magnetars

These illustrations show how an extremely rapidly rotating neutron star, which has formed from the collapse of a very massive star, can produce incredibly powerful magnetic fields. These objects are known as magnetars. Magnetars are neutron stars with magnetic fields that are about a quadrillion times greater than the magnetic field of Earth. These awesome magnetic fields are thought to be produced when an extremely rapidly rotating neutron star is formed by the collapse of the core of a massive star. When a neutron star forms it triggers a supernova explosion that expels the outer layers of the star at high speeds. The high rate of the rotation of the neutron star intensifies the already superstrong magnetic field to magnetar levels. When the magnetic forces get strong enough, they may cause starquakes on the surface of the neutron star that produce powerful outbursts of X-rays called X-ray flashes. These events may represent an intermediate type of supernova explosion - more energetic than ordinary supernovae, but less so than hypernovae, thought to be responsible for gamma ray bursts. Magnetar outbursts can also occur for hundreds of years after the initial explosion. The strongest steady magnetic field produced on Earth in a lab is about a million times greater than the Earth's magnetic field. Beyond this limit ordinary magnetic material would be blown apart by magnetic forces. Only on a neutron star, where gravity is more than 100 billion times as great as on Earth, can matter withstand the magnetic forces of a magnetar, and even there the neutron star's crust can break apart under the strain. The source of the power is the rapidly rotating magnetic field, so these pulsars are sometimes called rotationally powered pulsars, to distinguish them from another type of pulsar discovered by X-ray astronomers, the accretion powered pulsars. Accretion powered pulsars If a neutron star is in a close orbit around a normal companion star, it can capture matter flowing away from that star. This captured matter will form a disk around the neutron star from which it will spiral down and fall, or accrete, onto the neutron star. The infalling matter will gain an enormous amount of energy as it accelerates. Much of this energy will be radiated away at X-ray energies. The magnetic field of the neutron star can funnel the matter toward the magnetic poles, so that the energy release is concentrated in a column, or spot of hot matter. As the neutron star rotates, the hot region moves into and out of view and produces X-ray pulses. how matter falls, or accretes, from accretion disk onto the neutron star

how matter falls, or accretes, from accretion disk onto the <b>neutron</b> star

Closeup of a Neutron Star If you have a java enabled browser, you can view our animation and discussion of X-ray pulsars. Binary Animation

Animation of an X-ray Binary System (NASA) AVI, QuickTime Movie Accretion-powered pulsars are produced by matter flowing onto the neutron star, whereas rotation-powered pulsars produce an outflow of matter. (In some cases, a significant contribution to the X-ray emission can be from polar caps heated by "instreaming" particles.) For the latter, rapid rotation is required. For the former, an abundant source of infalling gas, such as a companion star is needed. (See Binary and Multiple Star Systems) Some of the strongest X-ray sources in our galaxy are accreting neutron stars in binary star systems. With Chandra, astronomers have detected hundreds of such objects in other galaxies as well. Accreting neutron stars exhibit various behaviors thought to be related to the details of how the matter falls onto the neutron star. Some pulse steadily, some flicker in a quasi-periodic way, some burst explosively, some eject jets of high-energy particles. If you have a java-enabled browser, you can view our animation and discussion of X-ray pulsars. A black hole in a binary system could also produce an accretion-powered source. Since black holes do not have a surface or a magnetic pole in the normal sense of the word, they cannot produce regular X-ray pulses, though they may flicker.

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Operated for NASA by SAOThis site was developed with funding from NASA under Contract NAS8-03060.Revised: September 26, 2008

An	accessible	summary	of
neutron	stars	and	X-ray	binaries,
presented	by	the	Chandra	X-ray
Observatory.	Includes	a	comprehensive	Q&A
section	and	a	selection	of
quality	images.

http://chandra.harvard.edu/xray_sources/neutron_stars.html

Neutron Stars and X-ray Binaries 2008 November

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An accessible summary of neutron stars and X-ray binaries, presented by the Chandra X-ray Observatory. Includes a comprehensive Q&A section and a selection of quality images.

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