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Post Info TOPIC: The Crab Nebula
Blobrana


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Observatories Combine to Crack Open the Crab Nebula

In the summer of the year 1054 AD, Chinese astronomers saw a new "guest star," that appeared six times brighter than Venus. So bright in fact, it could be seen during the daytime for several months. Halfway around the world, Native Americans made pictographs of a crescent moon with the bright star nearby that some think may also have been a record of the supernova.
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Title: Cas A and the Crab Were Not Stellar Binaries At Death
Author: C.S. Kochanek (1) ((1) Department of Astronomy, The Ohio State University)

The majority of massive stars are in binaries, which implies that many core collapse supernovae (ccSNe) should be binaries at the time of the explosion. Here we show that the three most recent, local (visual) SNe (the Crab, CasA and SN1987A) were not binaries, with limits on the initial mass ratios of q=M2/M1<0.1. No quantitative limits have previously been set for CasA and the Crab, while for SN1987A we merely updated existing limits in view of new estimates of the dust content. The lack of stellar companions to these three ccSNe implies a 90% confidence upper limit on the q>0.1 binary fraction at death of fb<44%. In a passively evolving binary model (meaning no binary interactions), with a flat mass ratio distribution and a Salpeter IMF, the resulting 90% confidence upper limit on the initial binary fraction of F<63% is in considerable tension with observed massive binary statistics. Allowing a significant fraction fM~25% of stellar binaries to merge reduces the tension, with F<63/(1-fM)~81%, but allowing for the significant fraction in higher order systems (triples, etc.) reintroduces the tension. That CasA was not a stellar binary at death also shows that a massive binary companion is not necessary for producing a Type IIb SNe. Much larger surveys for binary companions to Galactic SNe will become feasible with the release of the full Gaia proper motion and parallax catalogues, providing a powerful probe of the statistics of such binaries and their role in massive star evolution, neutron star velocity distributions and runaway stars.

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Blobrana


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NGC 1952
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Chikang Li brings the Crab Nebula to the lab

Senior research scientist Chikang Li wants to experiment with the stars. Intrigued by a curious kink phenomenon observed in the Crab Nebula, an interstellar cloud of gas and dust that formed in the wake of a supernova explosion, he has been looking for answers.
Images from the Chandra X-ray observatory show that a jet of plasma pouring straight out from the neutron star at the center of the nebula appears to change direction every few years, without changing its structure. Why? Scientists have hypothesized that magnetic fields with the right properties could explain this behaviour, but Li wanted proof.
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Blobrana


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A Death Star's Ghostly Glow

The nebula was first identified in 1731 and named in 1844. In 1928, Edwin Hubble linked the nebula to a supernova first witnessed in the spring of 1054 A.D. Now, the eerie glow of the burned-out star reveals itself in this new Hubble Space Telescope snapshot of the heart of the Crab Nebula. The green hue has been added to give the image a Halloween theme
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Title: 45 Years of Rotation of the Crab Pulsar
Author: Andrew Lyne, Christine Jordan, Francis Graham-Smith, Cristobal Espinoza, Ben Stappers, Patrick Weltrvrede

The 30-Hz rotation rate of the Crab pulsar has been monitored at Jodrell Bank Observatory since 1984 and by other observatories before then. Since 1968, the rotation rate has decreased by about 0.5Hz, interrupted only by sporadic and small spin up events (glitches). 24 of these events have been observed, including a significant concentration of 15 occurring over an interval of 11 years following MJD 50000. The monotonic decrease of the slowdown rate is partially reversed at glitches. This reversal comprises a step and an asymptotic exponential with a 320-day time constant, as determined in the three best-isolated glitches. The cumulative effect of all glitches is to reduce the decrease in slowdown rate by about 6%. Overall, a low mean braking index of 2.342(1) is measured for the whole period, compared with values close to 2.5 in intervals between glitches. Removing the effects of individual glitches reveals an underlying power law slowdown with the same braking index of 2.5. We interpret this value in terms of a braking torque due to a dipolar magnetic field in which the inclination angle between the dipole and rotation axes is increasing. There may also be further effects due to a monopolar particle wind or in-falling supernova debris.

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Blobrana


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NGC 1952
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Messier 1 (also M1, Crab Nebula, NGC 1952, Sharpless 244 and Taurus A) is a magnitude +8.4 supernova remnant and pulsar wind nebula located 6,500 ±1600 light-years away in the constellation Taurus. 

The supernova remnant was discovered by English astronomer John Bevis using a 7.62 cm (3-inch) 24-foot focal length simple refractor at Stoke Newington, Middlesex in 1731.
The supernova remnant was independently rediscovered by French astronomer Charles Messier using a 8.38 cm (3.3-inch) refracting telescope at the Hôtel de Cluny (now the Musée national du Moyen Age), in Paris, France on the 28th August 1758.

" What was the most remarkable night, was only browsing the sky with the telescope catadioptric around the southern horn of Taurus, marked x Bayer, M. Messier discovered there light about sembleable than the Comet, but was nevertheless brighter, whiter and a little more elongated than that then oservait Comet: Comet that had always seemed to him almost round in his hair, without appearance or tail or beard. Since the discovery of this new light or nebulous star did not take place until late this morning's observations ... "
Source. 

Right Ascension 05h 34m 31.97s, Declination +22° 00' 52.1"

At X-ray and gamma ray energies above 30 keV, the Crab is generally the strongest persistent source in the sky, with measured flux extending to above 10 TeV.
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Blobrana


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Messier 1
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Its remnant was accidentally re-discovered by the Englishman John Bevis in 1731. Although Bevis did not record a catalogue as such, he placed the object among sixteen others he labelled as 'nebula', in the Star Map of Taurus within his beautifully detail and expressive star atlas, Uranographia Britannica, which later published in London in 1750. This particular reference went unnoticed by all of the astronomical elite of the time, so Bevis' discovery remained just an obscure oddity.
In September 1758, Charles Messier also again accidentally found this object in the year of the first predicted return of Halley's comet. Messier discovery occurred while he was making nearby observations of the now obscure Comet De la Nux. When Messier eventually publish his famous deep-sky catalogue until 1771, Bevis wrote to Messier on the 10th June to inform him that he had discovered the small nebulosity in 1731. Messier examined his claim and agreed, and then in the subsequent versions of the catalogue acknowledged Bevis' discovery.
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Blobrana


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'Supernova' Cave Art Myth Debunked

Thousands of years ago a star exploded in a supernova, leaving behind the glorious riot of colored gas we see now as the Crab Nebula. The light from this explosion reached Earth in 1054 A.D., creating what looked like a new bright star in the sky as recorded by ancient Chinese and Arab astronomers. Native American cave paintings, too, have been thought to represent the supernova, but when one scientist went to look at the paintings in person recently he arrived at a different story altogether.
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An Image Gallery Gift from NASA's Swift

716499main1_crab_uv_labeled-673.jpg
Credit: NASA/Swift/E. Hoversten, PSU

Of the three telescopes carried by NASA's Swift satellite, only one captures cosmic light at energies similar to those seen by the human eye. Although small by the standards of ground-based observatories, Swift's Ultraviolet/Optical Telescope (UVOT) plays a critical role in rapidly pinpointing the locations of gamma-ray bursts (GRBs), the brightest explosions in the cosmos.
The Crab Nebula is the wreckage of an exploded star, or supernova, observed in the year 1054. The expanding cloud of gas is located 6,500 light-years away in the constellation Taurus. This composite of three Swift UVOT ultraviolet images highlights the luminous hot gas in the supernova remnant. The image is constructed from exposures using these filters: uvw1, centred at 2,600 angstroms (shown as red); uvm2, centred at 2,246 angstroms (green); and uvw2, centred at 1,928 angstroms (blue).
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Explosive origins for cosmic dust

The European Space Agency's Herschel Space Observatory has produced an intricate view of the remains of a star that died in a stellar explosion a millennium ago. This new view provides further proof that the cosmic dust which lies throughout our Galaxy is created when massive stars reach the end of their lives.
The study, led by Dr Haley Gomez of the School of Physics and Astronomy focused on the Crab Nebula which lies about six and a half thousand light years away from Earth and is the remnant of a dramatic explosion, called a supernova, originally seen by Chinese Astronomers in 1054 AD.
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