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Crab Nebula

Crab Nebula

The Crab Nebula (also known as Messier Object 1, M1 or NGC 1952) is a gaseous diffuse nebula in the constellation Taurus. It is the remnant of a supernova that was recorded by Chinese and Arab astronomers in 1054 as being visible during daylight for 23 days. Located at a distance of about 6500 ly from Earth, it has a diameter of 6 ly and is expanding at a rate of 1000 km per second. A neutron star in the center of the nebula rotates 30 times per second.

Crab Pulsar

At the center of the nebula is the Crab Pulsar, a neutron star remnant of the supernova which is roughly 10 km in diameter. It was discovered in 1969. The Crab Pulsar rotates once every 33 milliseconds, or 30 times each second, and the beams of radiation it emits interact with the nebular gases to produce complex patterns of wind and fluorescence. The most dynamic feature in the inner part of the nebula is the point where one of the pulsar's polar jets slams into the surrounding material forming a shock front. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar to well out into the main body of the nebula.

General information

The Crab Nebula is often used as a calibration source in X-ray astronomy. It is very bright in X-rays and the flux density and spectrum are known to be constant, with the exception of the pulsar. The pulsar provides a strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, 'Crab' and 'milliCrab' are sometimes used as units of flux density. Very few X-ray sources ever exceed one Crab in brightness. The Crab Nebula derived its name from its appearance in a drawing made by Lord Rosse in 1844 using his 36-inch telescope. In this sketch it does indeed resemble a crab, but upon reobserving the nebula in 1848 with his newly-built 72-inch telescope he produced a much more accurate drawing which bore little resemblance to the original. However, the name "Crab Nebula" stuck.

External links

- [http://www.seds.org/messier/m/m001.html Messier 1, SEDS Messier pages] Category:Supernova remnants Category:Messier objects Category:NGC objects Category:Taurus constellation ja:かに星雲

List of Messier objects

Gaseous

:For other meanings see gas (disambiguation). ---- A gas is one of the four main phases of matter (after solid and liquid, and followed by plasma), that subsequently appear as a solid material is subjected to increasingly higher temperatures. Thus, as energy in the form of heat is added, a solid (e.g. ice) will first melt to become a liquid (e.g. water), which will then boil or evaporate to become a gas (e.g. water vapor). In some circumstances, a solid (e.g. "dry ice") can directly turn into a gas: this is called sublimation. If the gas is further heated, its atoms or molecules can become (wholly or partially) ionized, turning the gas into a plasma.

Properties of a gas

#All collisions are perfectly elastic #The gas fills the entire container #The molecules have negligible volume In the gas phase, the atoms or molecules constituting the matter basically move independently, with no forces keeping them together or pushing them apart. Their only interactions are rare and random collisions. The particles move in random directions, at high speeds, whose range is dependent on the temperature and defined by the Maxwell-Boltzmann distribution. Therefore, the gas phase is a completely disordered state. Following the second law of thermodynamics, gas particles will immediately diffuse to homogeneously fill any shape or volume of space that is made available to them. The thermodynamic state of a gas is characterized by its volume, its temperature, which is determined by the average velocity or kinetic energy of the molecules, and its pressure, which is determined by the average velocity and density or number of molecules. These variables are related by the fundamental gas laws, which state that the pressure in an ideal gas is proportional to its temperature and number of molecules, but inversely proportional to its volume. Like liquids and plasmas, gases are fluids: they have the ability to flow and do not tend to return to their former configuration after deformation, although they do have viscosity. Unlike liquids, however, unconstrained gases do not occupy a fixed volume, but expand to fill whatever space they occupy. The kinetic energy per molecule in a gas is the second greatest of the states of matter (after plasma). Because of this high kinetic energy, gas atoms and molecules tend to bounce off of any containing surface and off one another, the more powerfully as the kinetic energy is increased. A common misconception is that the collisions of the molecules with each other is essential to explain gas pressure, but in fact their random velocities are sufficient to define that quantity. Mutual collisions are important only for establishing the Maxwell-Boltzmann distribution. Gas particles are normally well separated, as opposed to liquid particles, which are in contact. A material particle (say a dust mote) in a gas moves in Brownian Motion. Since it is at the limit of (or beyond) current technology to observe individual gas particles (atoms or molecules), only theoretical calculations give suggestions as to how they move, but their motion is different from Brownian Motion. The reason is that Brownian Motion involves a smooth drag due to the frictional force of many gas molecules, punctuated by violent collisions of an individual (or several) gas molecule(s) with the particle. The particle (generally consisting of millions or billions of atoms) thus moves in a jagged course, yet not so jagged as we would expect to find if we could examine an individual gas molecule.

Etymology

The word "gas" was apparently coined in the early 17th century by the Belgian chemist Jan Baptist van Helmont, as a re-spelling of his pronunciation of the Greek word chaos.

Constellation

A constellation is a group of stars visibly related to each other in a particular configuration.

Explanation

In three-dimensional space, most of the stars we see have little relation to one another, but can appear to be grouped on the celestial sphere of the night sky. Humans excel at finding patterns and throughout history have grouped stars that appear close to one another into constellations. An "unofficial" constellation, that is, one that may be widely known but is not recognized by astronomers or the International Astronomical Union, is also called an asterism, such as The Plough (also known in the US as the Big Dipper) and the Little Dipper. The stars in a constellation or asterism rarely have any astrophysical relationship to each other; they just happen to appear close together in the sky as viewed from Earth and typically lie many light years apart in space. However, one exception to this is the Ursa Major moving group. The grouping of stars into constellations is essentially arbitrary, and different cultures have had different constellations, although a few of the more obvious ones tend to recur frequently, e.g., Orion and Scorpius. The International Astronomical Union (IAU) divides the sky into 88 official constellations with precise boundaries, so that every direction belongs to exactly one constellation. In the northern celestial hemisphere, these are mostly based upon the constellations of the ancient Greek tradition, passed down through the Middle Ages, and contains the signs of the zodiac. The constellation boundaries were drawn up by Eugène Delporte in 1930, and he drew them along vertical and horizontal lines of right ascension and declination. However, he did so for the epoch B1875.0, which means that due to precession of the equinoxes, the borders on a modern star map (eg, for epoch J2000) are already somewhat skewed and no longer perfectly vertical or horizontal. This skew will increase over the years and centuries to come.

History of the Constellations

:Main article:List of Constellations Our current list is based on those listed by the Roman astronomer, Claudius Ptolemy, who lived in Alexandria, Egypt. (Claudius Ptolemy, the astronomer, was not related to the Greek kings of Egypt named Ptolemy.) In more recent times this list has been added to, to fill gaps between Ptolemy's patterns. The Greeks considered the sky as including both constellations and dim spaces between. But Renaisance star catalogs by Johann Bayer and John Flamsteed required every star to be in a constellation, and the number of visible stars in a constellation to be manageably small. Twelve of the constellations in the southern celestial hemisphere were not observable by the Greeks, and were created by Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman in the sixteenth century and first cataloged by Johann Bayer. Other proposed constellations didn't make the cut, most notably Quadrans Muralis (now part of Boötes) for which the Quadrantid meteors are named. Also the ancient constellation Argo Navis was so big that it was broken up into several different constellations, for the convenience of stellar cartographers.

Star names

All modern constellation names are Latin proper names or words, and some stars are named using the genitive of the constellation in which they are found. The genitive is formed using the usual rules of Latin grammar, and for those unfamiliar with that language the form of the genitive is unpredictable and must be memorized. Some examples include: Aries → Arietis; Taurus → Tauri; Gemini → Geminorum; Virgo → Virginis; Libra → Librae; Pisces → Piscium; Lepus → Leporis. These names include Bayer designations such as Alpha Centauri, Flamsteed designations such as 61 Cygni, and variable star designations such as RR Lyrae. However, many fainter stars will just be given a catalog number designation (in each of various star catalogs) that does not incorporate the constellation name. For more information about star names, see Star designations and the list of stars by constellation.

External links

- [http://www.dibonsmith.com/constel.htm The Constellations]
- [http://www.allthesky.com/constellations/ Photographic Atlas of the Constellations]
- [http://celestia.sourceforge.net Celestia] free 3D realtime space-simulation (OpenGL)
- [http://stellarium.free.fr/ Stellarium] realtime sky rendering program (OpenGL)
- [http://cdsweb.u-strasbg.fr/viz-bin/Cat?VI/49 Strasbourg Astronomical Data Center Files on official IAU constellation boundaries] (the older NASA ADC service does not function anymore)
- [http://www.astro.wisc.edu/~dolan/constellations/ Interactive Sky Charts] (Allows navigation through the entire sky with variable star detail, optional constellation lines)
- http://www.astronomical.org/constellations/obs.html
- http://www.seds.org/Maps/Stars_en/Fig/const.html
- [http://reference.allrefer.com/encyclopedia/categories/const.html Constellations Articles]
- [http://borghetto.astrofili.org/costellazioni/bordo.htm Full constellation diagrams resembling their names]
- [http://images.google.com/images?q=constellations Images of constellations] ko:별자리 ja:星座 th:กลุ่มดาว

Supernova remnant

A supernova remnant (SNR) is a plasma made up of the materials left behind by the gigantic explosion of a star in a supernova. There are two possible routes to this end: either a massive star may cease to generate fusion energy in its core, and collapse inward under the force of its own gravity, or a white dwarf star may accumulate material from a companion star until it reaches a critical mass and undergoes a thermonuclear explosion. In either case, the resulting supernova explosion expels much or all of the stellar material with great force. This plasma may reach temperatures of 10,000 to 1,000,000 K, and with densities of about 10,000,000 particles per cubic meter. In the case of a massive-star explosion, the core of the star may collapse so rapidly that it forms a sort of extremely compact (degenerate) matter. This compact object, which may be a neutron star or a black hole, is referred to as a compact supernova remnant. For both massive and white-dwarf stellar progenitors, the outermost layers of the star will be blown off by the force of the explosion into an expanding cloud of dust and gas. The shock wave and ejected material expanding from this explosion, and the interstellar material it sweeps up along the way, are called a diffuse supernova remnant. Perhaps the most famous and best-observed supernova remnant is SN 1987A, the newly formed remnant of a supernova in the Large Magellanic Cloud. A few other well-known supernova remnants are the Crab Nebula, a remnant of a relatively recent explosion (AD 1054); Tycho's Nova (SN 1572), a remnant named after Tycho Brahe, who recorded the brightness of its original explosion (AD 1572); and Kepler's SNR (SN 1604), named after Johannes Kepler.

External links

- [http://www.mrao.cam.ac.uk/surveys/snrs/ SNR Catalogue](D. A. Green Cambridge University)
- [http://agile.gsfc.nasa.gov/docs/objects/snrs/snrstext.html NASA: Introduction to Supernova Remnants.]
- [http://www.site.uottawa.ca:4321/astronomy/index.html#novaremnant_table Supernova Remnant] (UOttawa)
- [http://www.universetoday.com/am/publish/afterlife_supernova.html Afterlife of a Supernova]
- [http://www.ipac.caltech.edu/2mass/gallery/images_snrs.html 2MASS images of Supernova Remnants] Category:Supernova remnants Category:Supernovae Category:Nebulae

1054

Events

- Battle of Mortemer, February: Normans defeated a French army as it was caught pillaging and plundering. King Henry I of France withdrew his main army from Normandy as a result.
- Cardinal Humbertus, a representative of Pope Leo IX, and Michael Cerularius, Patriarch of Constantinople, decree each other's excommunication. Some historians look to this act as initiating the Great Schism between the Roman Catholic and Orthodox Christian Churches. To this day each claims to be the One Holy Catholic and Apostolic Church and each denies the other's right to that name. However, at the time of the excommunication, the Pope was dead; therefore, Cardinal Humbertus' act had no legal force. Moreover, individuals were excommunicated, not entire Churches.
- Malcolm Canmore begins his campaign for the throne of Scotland.
- July 4 - The SN 1054 supernova is recorded by the Chinese and possibly Native Americans near the star ζ Tauri. For several months it remains bright enough to be seen during the day. Its remnants form the Crab Nebula (NGC 1952). -- Reference, Journal of Astronomy, part 9, chapter 56 of Sung History (Sung Shih) first printing, 1340. facsimile on the frontispiece of Misner, Thorne, Wheeler Gravitation, 1973.
- July 27 - King Macbeth of Scotland's troops defeated in Dunsinane Hill. Macbeth himself escapes.

Deaths

- April 19 - Pope Leo IX (b. 1002)
- September 24 - Hermannus Contractus
- The death of Yaroslav the Wise, prince of Kievan Rus.

Light year

:There was also a 1988 animated science fiction film named "Light Years". A light year (or light-year), abbreviated ly, is the distance light travels in one year: about 9.461 × 10¹⁵ metres (9.461 petametres), or about 5.879 × 10¹² (nearly six trillion) miles. More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely distant from any gravitational or magnetic fields, in one Julian year (365.25 days of 86,400 seconds each). Since the speed of light in a vacuum is exactly 299,792,458 m/s by the definition of metre, one light year is exactly equal to 9,460,730,472,580,800 m. The light year is often used to measure distances to stars: a light year is not a unit of time. In astronomy, the preferred unit of measurement for such distances is the parsec which is defined as the distance at which an object will generate one arcsecond of parallax when the observing object moved one astronomical unit perpendicular to the line of sight to the observer. This is equal to approximately 3.26 light years. The parsec is preferred because it can be more easily derived from, and inter-compared with, observational data. However, outside scientific circles, the term light year is more widely used by the general public. A light year is also equal to about 63,241.077 astronomical units (AU). For a list of lengths on the order of one light year, see the article 1 E15 m. Units related to the light year are the light minute and light second, the distance light travels in a vacuum in one minute and one second, respectively. A light minute is equal to 17,987,547,480 m. Since light travels 299,792,458 m in one second, a light second is 299,792,458 m in length.

Miscellaneous facts

- It takes 8.3 minutes for light to travel from the Sun to the Earth (a distance of light years).
- The most distant space probe, Voyager 1, was 13 light hours (only light years) away from Earth in September 2004. It took Voyager 27 years to cover that distance.
- The nearest known star, Proxima Centauri is 4.22 light years away.
- The center of our galaxy, the Milky Way, is about 28,000 light years away. The Galaxy is about 100,000 light years across.
- The nearest large galaxy cluster, the Virgo Cluster, is about 60 million light years away.
- The particle horizon (observable part) of the universe has a radius of about 46 billion light years, but light from the edge of the observable universe was emitted only 13.7 billion years ago (the age of the universe). The figures differ because distant objects have continued to recede from us due to cosmological expansion (see Hubble's law).
- One gigaparsec is equal to approximately 3.2 billion light years.

External link

- [http://www.ex.ac.uk/trol/scol/ccleng.htm Conversion Calculator for Units of LENGTH] Category:Astronomical units of length ko:광년 ms:Tahun cahaya ja:光年 simple:Light year th:ปีแสง

Light-years

Miscellaneous facts

External link

- [http://www.ex.ac.uk/trol/scol/ccleng.htm Conversion Calculator for Units of LENGTH] Category:Astronomical units of length ko:광년 ms:Tahun cahaya ja:光年 simple:Light year th:ปีแสง

Neutron star

Neutron stars are one of the few possible endpoints of stellar evolution. A neutron star is formed from the collapsed remnant of a massive star after a Type II or Ib/c supernova. A typical neutron star has a mass between 1.4 to 5 solar masses, with a corresponding radius between 20 and 10 km — 30,000 to 70,000 times smaller than the Sun. Thus, neutron stars have densities of 8×10 to 2×10 g/cm³, about the density of an atomic nucleus. [http://heasarc.gsfc.nasa.gov/docs/xte/learning_center/ASM/ns.html] Compact stars of less than 1.4 solar masses, the Chandrasekhar limit, are white dwarfs; above three to five solar masses (the Tolman-Oppenheimer-Volkoff limit), gravitational collapse to a black hole is inevitable. Due to its small size and high density, a neutron star possesses a very high rotation speed (one revolution can take anything from thirty seconds to one six-hundredth of a second) and a surface gravity 2×10 to 3×10 times stronger than that of Earth. One of the measures for the gravity is the escape velocity, the velocity needed for an object to escape from the gravitational field to infinite distance. For a neutron star, such velocities are typically 150,000 km/s, about 1/2 of the velocity of light. Conversely, an object falling onto the surface of a neutron star would strike the star also at 150,000 km/s. To put this in perspective, if an average human were to encounter a neutron star, he or she would impact with roughly the energy yield of a 100 megaton nuclear explosion.

Structure

Current understanding of the structure of neutron stars is defined by existing mathematical models, which of course are subject to revision. Based on current models, the matter at the surface of a neutron star is composed of ordinary nuclei as well as electrons. The "atmosphere" of the star is roughly one meter thick, below which one encounters a solid "crust". Proceeding inward, one encounters nuclei with ever increasing numbers of neutrons; such nuclei would quickly decay on Earth, but are kept stable by tremendous pressures. Proceeding deeper, one comes to a point called neutron drip where free neutrons leak out of nuclei. In this region we have nuclei, free electrons, and free neutrons. The nuclei become smaller and smaller until the core is reached, by definition the point where they disappear altogether. The exact nature of the superdense matter in the core is still not well understood. While this theoretical substance is referred to as neutronium in science fiction and popular literature, the term "neutronium" is rarely used in scientific publications, due to ambiguity over its meaning. The term neutron-degenerate matter is sometimes used, though that term incorporates assumptions about the nature of neutron star core material. Neutron star core material could be a superfluid mixture of neutrons with a few protons and electrons, or it could incorporate high-energy particles like pions and kaons in addition to neutrons, or it could be composed of strange matter incorporating quarks heavier than up and down quarks, or it could be quark matter not bound into hadrons. However so far observations have neither indicated nor ruled out such exotic states of matter.

History of discoveries

In 1932 Sir James Chadwick discovered (Nature Vol 129, p. 312 "on the possible existence of a neutron") the neutron as an elementary particle, good for a Nobel Prize in Physics in 1935. In 1933 Walter Baade and Fritz Zwicky (Phys. Rev. 45 "Supernovae and Cosmic rays") proposed the existence of the neutron star, only a year after Chadwick's discovery of the neutron. In seeking an explanation for the origin of a supernova, they proposed that the neutron star is formed in a supernova. Supernovae are suddenly appearing new stars in the sky, whose luminosity in the optical might outshine an entire galaxy for days to weeks. Baade and Zwicky correctly proposed at that time that the release of the gravitational binding energy of the neutron stars powers the supernova: "In the supernova process mass in bulk is annihilated". If the central part of a massive star before its collapse contains (for example) 3 solar masses, then a neutron star of 2 solar masses can be formed. The binding energy E of such a neutron star, when expressed in mass units via E=mc², is the equivalence of 1 solar mass. It is ultimately this energy that powers the supernova. In 1967 Jocelyn Bell and Anthony Hewish discover radio pulses from a pulsar, later interpreted as originating from an isolated, rotating neutron star. The energy source is rotational energy of the neutron star. The largest number of known neutron stars are of this type. In 1971 Riccardo Giacconi, Herbert Gursky, Ed Kellogg, R. Levinson, E. Schreier, and H. Tananbaum discover 4.8 second pulsations in an X-ray source in the constellation Centaurus, Cen X-3. They interpret this as resulting from a rotating hot neutron star in orbit around another star. The energy source is gravitational and results from a rain of gas falling onto the surface of the neutron star.

Some neutron stars that can be observed

- X-ray burster - a neutron star with a low mass binary companion from which matter is accreted resulting in irregular bursts of energy from the surface of the neutron star.
- Pulsar - general term for neutron stars that emit directed pulses of radiation towards us at regular intervals due to their strong magnetic fields.
- Magnetar - a neutron star with an extremely strong magnetic field; some magnetars are observed as soft gamma repeaters. Neutron stars rotate extremely rapidly after their creation due to the conservation of angular momentum; like an ice skater pulling in his or her arms, the slow rotation of the original star's core speeds up as it shrinks. A newborn neutron star can rotate several times a second; sometimes, when they orbit a companion star and are able to accrete matter from it, they can increase this to several thousand times per second, distorting into an oblate spheroid shape despite their own immense gravity (an equatorial bulge). Over time, neutron stars slow down because their rotating magnetic fields radiate energy; older neutron stars may take several seconds for each revolution. The rate at which a neutron star slows down its rotation is usually constant and very small: the observed rates are between 10^-10 and 10^-21 second for each rotation. In other words, for a typical slow down rate of 10^-15 seconds per rotation, then a neutron star now rotating in 1 second will rotate in 1.000003 seconds after a century, or 1.03 seconds after 1 million years. Sometimes a neutron star will undergo a glitch: a rapid and unexpected increase of its rotation speed (of the same, extremely small scale as the constant slowing down). Glitches are thought to be the effect of a sudden coupling between the superfluid interior and the solid crust. Neutron stars also have very intense magnetic fields - typically about 10¹² times stronger than Earth's. Neutron stars may "pulse" due to particle acceleration near the magnetic poles, which are not aligned with the rotation axis of the star. Through mechanisms not yet entirely understood, these particles produce coherent beams of radio emission. External viewers see these beams as pulses of radiation whenever the magnetic pole sweeps past the line of sight. The pulses come at the same rate as the rotation of the neutron star, and thus, appear periodic. Neutron stars which emit such pulses are called pulsars.

Pulsars

When pulsars were first discovered, the fast time scale of radio pulses (about 1 s, uncommon to astronomy in the 1930s) was half-seriously considered to be caused by extraterrestrial intelligence, later jokingly referred to as LGM-1, for "Little Green Men." The discovery of many pulsars, spread all over the sky with different rotation periods quickly excluded this option. The discovery of a pulsar associated with the Vela supernova remnant, soon followed by the further discovery of a pulsar which appeared to be powering the Crab Nebula, produced compelling arguments for the neutron star interpretation.

Magnetars

Another class of neutron star, known as the magnetar, exists. These have a magnetic field of about 100 gigateslas, strong enough to wipe a credit card on Earth from the Moon's orbit. By comparison, the Earth's natural magnetic field is about 60 microteslas. A small neodymium based rare earth magnet has a field of about a tesla, and most media used for data storage can be erased with milliteslas. Magnetars occasionally produce bursts of X-ray emission. About once per decade, a magnetar somewhere in the Galaxy produces a giant flare of gamma-rays. Magnetars have long rotation periods, typically 5 to 12 seconds, because their strong magnetic fields have caused them to slow down.

External links

- [http://www.astro.umd.edu/~miller/nstar.html Introduction to neutron stars]

References

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- Category:Star types ja:中性子星 th:ดาวนิวตรอน

Crab Pulsar

The Crab Pulsar (PSR B0531+21) is a supernova remnant located in the Crab Nebula, discovered in 1969. The pulsar is roughly 10 km in diameter and rotates once every 33 milliseconds, or 30 times each second. The beams of radiation it emits interact with the nebular gases to produce complex patterns of wind and fluorescence. The most dynamic feature in the inner part of the nebula is the point where one of the pulsar's polar jets slams into the surrounding material forming a shock front. The shape and position of this feature shifts rapidly, with the equatorial wind appearing as a series of wisp-like features that steepen, brighten, then fade as they move away from the pulsar to well out into the main body of the nebula. The Crab Nebula is often used as a calibration source in X-ray astronomy. It is very bright in X-rays and the flux density and spectrum are known to be constant, with the exception of the pulsar itself. The pulsar provides a strong periodic signal that is used to check the timing of the X-ray detectors. In X-ray astronomy, 'Crab' and 'milliCrab' are sometimes used as units of flux density. Very few X-ray sources ever exceed one Crab in brightness. Category:Pulsars

Supernova remnant

External links

1969

1969 (MCMLXIX) was a common year starting on Wednesday :For other uses, see Number 1969. :For the movie, see 1969 (movie). :For the Velvet Underground live album, see 1969: The Velvet Underground Live.

Events

January

- January 1 - Australian media baron Rupert Murdoch purchases the largest selling British Sunday newspaper The News Of The World
- January 3 - Pele scores his 1000th goal
- January 5 - The Derry Riots leave over 100 people injured
- January 10 - After 147 years, the last issue of the Saturday Evening Post is published
- January 12 - Super Bowl III: the New York Jets defeat the Baltimore Colts
- January 14 - An explosion aboard the USS Enterprise near Hawaii kills 25
- January 15 - The Soviet Union launches Soyuz 5
- January 16 - Ten paintings defaced in New York's Metropolitan Museum of Art
- January 16 - Student Jan Palach sets himself on fire in Prague's Wenceslas Square to protest the invasion of Czechoslovakia by the Soviet Union. Three days later he dies.
- January 20 - Richard Nixon succeeds Lyndon Johnson as President of the United States of America
- January 24 - Martial Law declared in Madrid, the University is closed and over 300 students are arrested
- January 27 - 14 men, nine of them Jews, were executed in Baghdad for spying for Israel
- January 27 - Reverend Ian Paisley, hardline Protestant leader in Northern Ireland, is jailed for three months for illegal assembly.
- January 30 - The Beatles' last public performance, on the roof of Apple Records. The impromptu concert was broken up by the police

February

- February 1 - Birth, in Paris, France, of Denis Cheyrouze, French media guru.
- February 4 - In Cairo Yasser Arafat is appointed Palestinian Liberation Organization leader at the Palestinian National Congress and takes command the next day
- February 8 - The last issue of the Saturday Evening Post hits magazine stands
- February 13 - FLQ terrorists bomb the Stock Exchange in Montreal, Quebec
- February 24 - Launch of the Mariner 6 Mars probe
- February 24 - Tinker v. Des Moines Independent Community School District (Case against pure speech in schools)
- February 25 - George Jones marries Tammy Wynette

March

- March 1 - Major league baseballer Mickey Mantle announces his retirement.
- March 1 - During a performance at Miami's Dinner Key Auditorium, Jim Morrison of the Doors is arrested for exposing himself during the show. Morrison is officially charged with lewd and lascivious behavior, indecent behavior, open profanity and public drunkenness.
- March 1 - John Kerry officially leaves active duty in Vietnam
- March 2 - In Toulouse, France the first Concorde test flight is conducted
- March 2 - Soviet and Chinese forces clash at a border outpost on the Ussuri River
- March 3 - In a Los Angeles, California court, Sirhan Sirhan admits that he killed presidential candidate Robert F. Kennedy
- March 3 - Apollo program: NASA launches Apollo 9 to test the lunar module
- March 10 - In Memphis, Tennessee, James Earl Ray pleads guilty to assassinating Martin Luther King Jr. Ray would later retract his guilty plea
- March 13 - Apollo program: Apollo 9 returns safely to Earth after testing the Lunar Module
- March 17 - Golda Meir of Milwaukee, Wisconsin, USA, becomes Prime Minister of Israel
- March 17 - The Longhope lifeboat in Scotland is lost, the entire crew of eight die.
- March 19 - British paratroopers and Marines land on the island of Anguilla.
- March 28 - Dwight D Eisenhower dies after a long illness in the Walter Reed Army Medical Center, Washington DC.

April

- April 1 - The Hawker Siddeley Harrier enters service with the RAF
- April 4 - Dr. Denton Cooley implants the first temporary artificial heart
- April 13 - Queensland: The final day of the Brisbane Tramways after 84 years of operation.
- April 20 - British troops arrive in Northern Ireland to reinforce the Royal Ulster Constabulary.
- April 22 - Robin Knox-Johnston becomes the first person to sail around the world solo without stopping
- April 28 - General de Gaulle steps down as president of France after having suffered a defeat in a referendum the day before.
- April 29 - First anniversary of the Broadway production of the musical Hair is celebrated with free concert at Wollman Skating Rink

May

- May 10 - Zip to Zap, a harbringer of the Woodstock Concert, ends with dispersal and eviction of youth and young adults at Zap, North Dakota by the National Guard.
- May 10 - The Battle of Dong Ap Bia, also known as the Hamburger Hill, begins in Vietnam War
- May 13 - May 13th Incident: Race riots occur in Kuala Lumpur, Malaysia
- May 16 - Venera program: Venera 5, a Soviet spaceprobe, lands on Venus
- May 17 - Venera program: Soviet Venera 6 begins to descend into Venus' atmosphere sending back atmospheric data before being crushed by pressure
- May 17 - Tom McClean completes the first solo transatlantic crossing by a rowboat
- May 18 - Apollo program: Apollo 10 launches
- May 19-20 - French Foreign Legion paratroopers land onto Kolwezi, Zaire, to rescue Europeans in a middle of a civil war
- May 20 - National Guard helicopters spray skin-stinging powder on anti-war protesters in California
- May 22 - Apollo program: Apollo 10's lunar module flies within 15,400 m of the moon's surface
- May 26 - Apollo program: Apollo 10 returns to earth after a successful eight-day test of all the components needed for the upcoming first manned moon landing
- May 26-June 2: John Lennon and Yoko Ono conduct their Bed-In at the Queen Elizabeth Hotel in Montreal, Quebec, and record the song "Give Peace a Chance."
- May 29 - Mashina Vremeni Russian rock band official birthday
- May 30 - Riots in Curaçao, marking the start for a movement for Afro-Caribbean civil rights on the island.

June

- June 2 - In Ottawa, Canada the National Arts Centre opens its doors to the public for the first time
- June 2 - Australian aircraft carrier Melbourne collides with the US destroyer Frank E. Evans in the South China Sea - 74 US sailors dead
- June 8 - After the Columbia Broadcasting System (CBS) cancels the program, the last Smothers Brothers Comedy Hour airs
- June 8 - President Nixon and South Vietnamese President Nguyen Van Thieu meet at Midway Island. Nixon announced that 25,000 U.S. troops would be withdrawn by September.
- June 20 - Georges Pompidou elected President of France
- June 23 - Warren E. Burger is sworn in as Chief Justice of the United States by retiring chief Earl Warren.
- June 24 - United Kingdom and Rhodesia sever diplomatic ties
- June 28 - The Stonewall riots mark the start of the modern gay rights movement in the U.S.

July

gay rights movement
- July 5 – Assassination of Mboya, Kenyan Minister of Development
- July 7 - French is made equal to English throughout the Canadian national government
- July 8 - Vietnam War: The very first U.S. troop withdrawals are made
- July 10 - Trimaran the Teignmouth Electron of Donald Crowhurst is found drifting and unoccupied - Crowhurst might have committed suicide
- July 14 - Football War - after Honduras loses a soccer game against El Salvador, rioting breaks out in Honduras against Salvadoran migrant workers. Of the 300,000 Salvadorean workers in Honduras, tens of thousands are expelled, prompting a brief Salvadoran invasion of Honduras. The OAS works out a cease-fire on July 18, taking effect on July 20
- July 18 - Ted Kennedy drives off a bridge on his way home from a party on Chappaquiddick Island, Massachusetts. Mary Jo Kopechne, a former campaign aide to his brother who was in the car with him, dies in the incident
- July 20 - Apollo program: The human race, represented by Neil Armstrong and Buzz Aldrin, lands on the Moon. Apollo 11 lifted off for the moon on July 16 and returned safely on July 24
- July 25 - Vietnam War: US President Richard Nixon declares the Nixon Doctrine stating that the United States now expects its Asian allies to take care of their own military defense. This was the start of the "Vietnamization" of the war
- July 30 - Vietnam War: US President Richard M. Nixon makes an unscheduled visit to South Vietnam and meets with President Nguyen Van Thieu and with US military commanders
- July 31 - Halfpenny ceases to be legal tender in the UK

August

- August 4 - Vietnam War: At the apartment of French intermediary Jean Sainteny in Paris, US representative Henry Kissinger and North Vietnamese representative Xuan Thuy begin secret peace negotiations. The negotiations will eventually fail
- August 5 - Mariner program: Mariner 7 makes its closest fly-by of Mars (3,524 kilometers)
- August 8 - Fire in the Bannerman's Castle in the Hudson River - most of the roof collapses
- August 9 - Members of a cult led by Charles Manson murder five people including Sharon Tate, Jay Sebring and, Abigail Folger. The next day The Family would murder Rosemary and Leno LaBianca
- August 10 - Manson family kills Leno and Rosemary LaBianca
- August 12 - Jack Lynch, Taoiseach of the Republic of Ireland, makes a speech to the United Nations in which he asks them to deploy a peace-keeping mission in Northern Ireland.
- August 13 - Serious border clash between Soviet Union and People's Republic of China
- August 14 - British troops deployed in Northern Ireland
- August 15 - The Woodstock Festival of music begins in upstate New York lasting three days and featuring some of the top rock musicians of the era
- August 17 - Category 5 Hurricane Camille hits the Mississippi coast killing 248 people and causing US$1.5 billion in damage (1969 dollars)
- August 21 - Part of the al-Aqsa Mosque is destroyed by arson

September

- September 1 - A coup in Libya oust King Idris and brings Col. Moammar Qaddafi to power
- September 2 - The first automatic teller machine in the United States is installed in Rockville Centre, New York.
- September 5 - My Lai Massacre: Lt. William Calley is charged with six specifications of premeditated murder for the death of 109 Vietnamese civilians in My Lai
- September 22 - 25 Islamic conference in Rabat, Morocco after al-Aqsa Mosque fire (Augusr 21) condemns Israeli occupation of Jerusalem
- September 28 - Social Democrats and Free Democratic Party have received a majority of votes in the German parliamentary elections and decide to form a common government

October

- October 1 - In Sweden, Olof Palme is elected Labour party leader, replacing Tage Erlander as prime minister on October 14
- October 9 - In Chicago, Illinois, the United States National Guard is called in for crowd control as demonstrations continue in connection to the trial of the "Chicago Eight" (trial started on September 24)
- October 15 - Vietnam War: Hundreds of thousands of people take part in National Moratorium antiwar demonstrations across the United States
- October 16 - The ("miracle") New York Mets win the World Series, beating the heavily favored Baltimore Orioles, four games to one.
- October 17 - Willard S. Boyle and George Smith invent the CCD at Bell Laboratories. Today, this technology is widely used in digital cameras.
- October 21 - Willy Brandt becomes Chancellor of West Germany
- October 21 - Siad Barre comes to power in Somalia in a coup
- October 31 - Wal-Mart incorporates as Wal-Mart Stores, Inc.

November

- November - Creation of ARPANET, the predecessor of the Internet
- November 3 - Vietnam War: US President Richard M. Nixon addresses his nation on television and radio asking the "silent majority" to join him in solidarity on the Vietnam War effort and to support his policies
- November 9 - Group of Amerindians lead by Richard Oakes seize the Alcatraz island for 19 months, inspiring a wave of renewed Indian pride and government reform
- November 12 - Vietnam War: My Lai Massacre - Independent investigative journalist Seymour Hersh breaks the My Lai story
- November 13 - Vietnam War: Anti-war protesters in Washington, DC stage a symbolic "March Against Death"
- November 14 - Apollo program: NASA launches Apollo 12, the second manned mission to the surface of the Moon (landed on the Moon on November 19)
- November 15 - Cold War: The Soviet submarine K-19 collides with the American submarine USS Gato in the Barents Sea
- November 15 - Vietnam War: In Washington, DC, 250,000-500,000 protesters staged a peaceful demonstration against the war
- November 15 - Regular colour television broadcasts begin on BBC1 and ITV in UK.
- November 17 - Cold War: Negotiators from the Soviet Union and the United States meet in Helsinki to begin SALT I negotiations aimed at limiting the number of strategic weapons on both sides
- November 19 - Apollo program: Apollo 12 astronauts Charles Conrad and Alan Bean land at Oceanus Procellarum ("Ocean of Storms") and become the third and fourth humans to walk on the Moon
- November 20 - Vietnam War: The Cleveland Plain Dealer publishes explicit photographs of dead villagers from the My Lai massacre in Vietnam
- November 20 - Richard Oakes returns with 90 followers and offers to buy the Alcatraz for $24 (he leaves the island January 1970)
- November 21 - U.S. President Nixon and Japanese Premier Eisaku Sato agree in Washington on the return of Okinawa to Japanese control in 1972. Under the terms of the agreement, U.S. retains rights to military bases on island, but must be nuclear-free.
- November 21 - The first ARPANET link is established
- November 21 - The senate voted down the Supreme Court nomination of Clement F. Haynsworth, the first such rejection since 1930.
- November 24 - Apollo program: The Apollo 12 spacecraft splashes down safely in the Pacific Ocean, ending the second manned mission to the Moon
- November 25 - John Lennon returns his OBE to protest the British government's support of the US war in Vietnam

December

- December 1 - Vietnam War: The first draft lottery in the United States is held since World War II (on January 4, 1970, the New York Times ran a long article, "Statisticians Charge Draft Lottery Was Not Random")
- December 2 - The Boeing 747 jumbo jet makes its debut. It carries 191 people, most of them reporters and photographers, from Seattle to New York City.
- December 4 - Black Panther members Fred Hampton and Mark Clark are shot dead in their sleep during a raid by 14 Chicago police officers.
- December 12 - Piazza Fontana Slaughter in Italy (Strage di Piazza Fontana). A U.S. officer and C.I.A. agent called David Carrett involved.

Undated events

- Parker Morris Standards became mandatory for all Council housing in the UK.
- Summer saw the invention of Unix
- In the autumn, the first four nodes of the ARPAnet went up
- ACM SIGGRAPH founded

Ongoing events

- Vietnam War (1964 - 1975)
- War of Attrition, between Egypt and Israel, which lasted until August 1970. This conflict was characterized by escalating artillery duels, air raids and commando missions

Births

January

- January 2 - Christy Turlington, American fashion model
- January 2 - Tommy Morrison, American boxer
- January 3 - Michael Schumacher, German race car driver
- January 5 - Marilyn Manson, American singer
- January 14 - Jason Bateman, American actor
- January 14 - David Grohl, American drummer and composer (Nirvana; later, Foo Fighters)
- January 16 - Roy Jones Jr., American boxer
- January 17 - Lukas Moodysson, Swedish film director
- January 20 - Patrick K. Kroupa, American writer, hacker
- January 20 - Skeet Ulrich, American actor

February

- February 1 - Gabriel Batistuta, Argentine footballer
- February 3 - Retief Goosen, South African golfer
- February 5 - Bobby Brown, American singer
- February 11 - Jennifer Aniston, American actress
- February 12 - Hong Myung-Bo, South Korean footballer
- February 17 - Tuesday Knight, American actress

March

- March 1 - Javier Bardem, Spanish actor
- March 1 - Dafydd Ieuan, Welsh drummer (Super Furry Animals)
- March 19 - Connor Trinneer, American actor

April

- April 6 - Bret Boone, baseball player
- April 10 - Billy Jayne, American actor
- April 11 - Cerys Matthews, Welsh singer
- April 17 - Henry Ian Cusick, Peruvian actor
- April 19 - Susan Polgar, Hungarian chess player
- April 25 - Joe Buck, baseball and American football broadcaster
- April 25 - Darren Woodson, American football player
- April 25 - Renée Zellweger, American actress

May

- May 2 - Brian Lara, West Indian cricketer
- May 3 - Daryl F. Mallett, American author and actor
- May 7 - Eagle Eye Cherry, Swedish-born musician
- May 10 - Dennis Bergkamp, Dutch soccer player
- May 13 - Nikos Aliagas, French-born television host
- May 14 - Cate Blanchett, Australian actress
- May 15 - Emmitt Smith, American football player
- May 16 - Tracey Gold, American actress
- May 16 - Steve Lewis, American athlete
- May 18 - Martika, American singer
- May 21 - Georgiy R. Gongadze, Ukrainian journalist (d. 2000)

June

- June 11 - Steven Drozd, American drummer (The Flaming Lips)
- June 14 - Steffi Graf, German tennis player
- June 15 - Oliver Kahn, German football goalkeeper
- June 17 - Paul Tergat, Kenyan athlete
- June 18 - Pål Pot Pamparius, Norwegian guitarist and keyboardist (Turbonegro)
- June 24 - Sissel Kyrkjebø, Norwegian singer
- June 25 - Matt Gallant, American television host

July

- July 5 - John LeClair, American hockey player
- July 10 - Gale Harold, American actor
- July 18 - Masanori Murakawa, Japanese professional wrestler
- July 20 - Josh Holloway, American actor
- July 24 - Jennifer Lopez, American actress and singer
- July 27 - Triple H, American professional wrestler

August

- August 2 - Fernando Couto, Portuguese footballer
- August 6 - Elliott Smith, American musician (d. 2003)
- August 9 - Troy Percival, baseball player
- August 13 - Midori Ito, Japanese figure skater
- August 18 - Edward Norton, American actor
- August 18 - Christian Slater, American actor
- August 19 - Matthew Perry, American actor
- August 28 - Jack Black, American actor

September

- September 2 - Cedric "K-Ci" Hailey, American singer
- September 5 - Dweezil Zappa, American actor and musician
- September 9 - Rachel Hunter, New Zealand model and actress
- September 13 - Shane Warne, Australian cricketer
- September 24 - Donald DeGrate, Jr., American music producer
- September 25 - Hansie Cronje, South African cricketer (d. 2002)
- September 25 - Hal Sparks, American actor and comedian
- September 25 - Catherine Zeta-Jones, Welsh actress

October

- October 1 - Igor Ulanov, Russian hockey player
- October 3 - Gwen Stefani, American singer (No Doubt)
- October 8 - Julia Ann, American porn actress
- October 10 - Brett Favre, American football player
- October 13 - Nancy Kerrigan, American figure skater
- October 14 - David Strickland, American actor (d. 1999)
- October 17 - Ernie Els, South African golfer
- October 19 - Trey Parker, American television producer
- October 20 - Juan Gonzalez, baseball player
- October 30 - Clay Enos, American photographer

November

- November 4 - Matthew McConaughey, American actor
- November 7 - Michelle Clunie, American actress
- November 7 - Hélène Grimaud, French pianist
- November 7 - Bryant H. McGill, American poet
- November 11 - Carson Kressley, American fashion expert
- November 12 - Heinz-Christian Strache, Austrian politician
- November 17 - Jean-Michel Saive, Belgian table tennis player
- November 18 - Sam Cassell, basketball player
- November 20 - AQi Fzono, Japanese composer
- November 21 - Ken Griffey, Jr., baseball player
- November 28 - Bosco Tesanovic, Bosco accountancy franchiser
- November 29 - Mariano Rivera, Panamanian Major League Baseball player
- November 29 - Pierre van Hooijdonk, Dutch footballer

December

- December 4 - Jennifer Unger, Public health researcher
- December 15 - Rick Law, American illustrator and producer
- December 19 - Kristy Swanson, American actress
- December 21 - Julie Delpy, French actress
- December 23 - Martha Byrne, American actress and singer
- December 28 - Linus Torvalds, Finnish computer programmer
- December 30 - Jay Kay, English singer (Jamiroquai)

Deaths

January

- January 4 - Violet and Daisy Hilton, English conjoined twin actresses (b. 1908)
- January 8 - Albert Hill, British athlete (b. 1889)
- January 19 - Jan Palach Czech student protester (suicide) (b. 1948)
- January 25 - Irene Castle, English dancer (b. 1893)
- January 29 - Allen Dulles, American director of the Central Intelligence Agency (b. 1893)
- January 30 - Georges Pire, Belgian monk, recipient of the Nobel Peace Prize (b. 1910)

February

- February 4 - Thelma Ritter, American actress (b. 1905)
- February 9 - Gabby Hayes, American actor (b. 1885)
- February 20 - Ernest Ansermet, Swiss conductor (b. 1883)
- February 23 - King Saud of Saudi Arabia (b. 1902)
- February 26 - Levi Eshkol, Prime Minister of Israel (b. 1895)

March

- March 4 - Nicholas Schenck, Russian-born film empresario (b. 1881)
- March 11 - John Wyndham, British author (b. 1903)
- March 21 - Pinky Higgins, American baseball player and manager (b. 1909)
- March 26 - John Kennedy Toole, American author (b. 1937)
- March 27 - B. Traven, German writer
- March 28 - Dwight D. Eisenhower, 34th President of the United States (b. 1890)

May

- May 4 - Osbert Sitwell, English writer (b. 1892)
- May 14 - Frederick Lane, Australian swimmer (b. 1888)
- May 19 - Coleman Hawkins, American musician (b. 1904)

June-December

- June 21 - Maureen Connolly, American tennis player (b. 1934)
- June 22 - Judy Garland, American actress and singer (b. 1922)
- July 5, Walter Gropius, German architect (b. 1883)
- July 18 - Mary Jo Kopechne, American campaign aide to U.S. Senator Robert F. Kennedy (b. 1940)
- July 24 - Witold Gombrowicz, Polish novelist and dramatist (b. 1904)
- August 9 - Cecil Frank Powell, British physicist, Nobel Prize laureate (b. 1903)
- August 9 - Sharon Tate, American actress (murdered) (b. 1943)
- August 17 - Otto Stern, German physicist, Nobel Prize laureate (b. 1888)
- August 27 - Ivy Compton-Burnett, English novelist (b. 1884)
- August 27 - Erika Mann, German writer (b. 1905)
- August 31 - Rocky Marciano, American boxer (b. 1923)
- September 2 - Ho Chi Minh, President of Vietnam (b. 1890)
- October 4 - Natalino Otto, Italian singer (b. 1912)
- October 12 - Sonja Henie, Norwegian figure skater (b. 1912)
- October 21 - Jack Kerouac, American author (b. 1922)
- October 21 - Waclaw Sierpinski, Polish mathematician (b. 1882)
- October 30 - Pops Foster, American musician
- November 12 - William F. Friedman, American cryptanalyst (b. 1891)
- November 15 - Iskander Mirza, first President of Pakistan
- November 18 - Joseph P. Kennedy, Sr., American politician (b. 1888)
- December 4 - Fred Hampton, Black Panther (shot by police) (b. 1948)
- December 4 - Mark Clark, Black Panther (shot by police) (b. 1896)
- December 12 - Magic Sam, American musician (b. 1937)
- December 31 - (CdSe) quantum dots.]] Fluorescence is a luminescence which is mostly found as an optical phenomenon in cold bodies, in which a molecule absorbs a high-energy photon, and re-emits it as a lower-energy (longer-wavelength) photon. The energy difference between the absorbed and emitted photons ends up as molecular vibrations (heat). Usually the absorbed photon is in the ultraviolet, and the emitted light (luminescence) is in the visible range, but this depends on the absorbance curve and Stokes shift of the particular fluorophore. Fluorescence is named after the mineral fluorite (calcium fluoride), which exhibits this phenomenon.

Equation

S_1 \to S_2 + h \nu

This means that the system starts in state

S_1

, and after the fluorescent emission of a photon with energy

h \nu

, it is in state

S_2

where: h = Planck's constant and

\nu

= frequency of the fluorescing light

Rules

Kasha–Vavilov rule The quantum yield of luminescence is independent of the wavelength of exciting radiation. Jablonski diagram

Crab Nebula

Crab Pulsar

General information

Further reading

See also

External links

List of Messier objects

See also

Gaseous

Properties of a gas

Etymology

See also

Constellation

Explanation

History of the Constellations

Star names

See also

External links

Supernova remnant

See also

External links

1054

Events

Deaths

See also

Light year

Miscellaneous facts

See also

External link

Light-years

Miscellaneous facts

See also

External link

Neutron star

Structure

History of discoveries

Some neutron stars that can be observed

Pulsars

Magnetars

See also

External links

References

Crab Pulsar

Supernova remnant

See also

External links

1969

Events

January

February

March

April

May

June

July

August

September

October

November

December

Undated events

Ongoing events

Births

January

February

March

April

May

June

July

August

September

October

November

December

Deaths

January

February

March

May