HEAPOW: SN2014J (2014 Feb 03)

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HEAPOW: SN2014J (2014 Feb 03)

Post by bystander » Mon Feb 10, 2014 9:20 pm

Image HEAPOW: SN2014J (2014 Feb 03)

A nearby supernova is something to get excited about. And on January 21, 2014, the astronomical world was abuzz with the discovery of a Type Ia supernova, the deflagration of a compact white dwarf star in the nearby galaxy M82. This explosion, now known as SN2014J, was serendipitously discovered by astronomer Steve Fossey and his astronomy class during a teaching session at the University of London Observatory. Its location in M82, about 12 million lightyears distant, makes it one of the nearest supernovae of any type in about a decade, and the nearest Type Ia supernova in modern history. This is especially important, since Type Ia supernovae are regarded as "standard candles", useful for determining distances to the edge of the Universe, and instrumental in the discovery of Dark Energy, the surprising force which accelerates the expansion of the Universe. This event represents a rare opportunity and is currently being studied by observatories around the world as well as NASA's fleet of space-based facilities, including the Hubble Space Telescope, the Chandra X-ray Observatory, Swift, the Fermi Gamma-ray Space Telescope, and NuSTAR. The image above is an early observation of the supernova taken on January 22 by Swift's Ultraviolet and Optical Telescope. Mid-ultraviolet light is shown in blue, near-UV light in green, and visible light in red, while the arrow marks the location of SN 2014J.
NASA Spacecraft Take Aim At Nearby Supernova
http://asterisk.apod.com/discuss_apod.php?date=140124
http://asterisk.apod.com/viewtopic.php?f=31&t=32797
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MargaritaMc
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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by MargaritaMc » Tue Feb 11, 2014 3:01 pm

"Deflagration" was a new to my vocabulary. Clicking on the link on it above went to a most useful and informative video.
Thank you for posting this, bystander.

M
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by neufer » Tue Feb 11, 2014 4:06 pm

MargaritaMc wrote:
"Deflagration" was a new to my vocabulary. Clicking on the link on it above went to a most useful and informative video.
  • Why, sure, I'm a billiard player
    Certainly mighty proud to say,
    I'm always mighty proud to say it
    I consider the hours I spend with a cue in my hand are golden
    Help you cultivate horse sense and a cool head and a keen eye
    Didja ever take and try to give an iron clad leave
    to yourself from a three-rail billiard shot?
    But just as I say it takes judgement, brains and maturity
    to score in a balk-line game
    I say that any boob can take and shove a ball in a pocket
    And I call that sloth;
    the first big step on the road to the depths of deflagration.
Art Neuendorffer

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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by Beyond » Tue Feb 11, 2014 4:10 pm

The beginning of the explosion in the "Deflagration" video reminds me of an atomic bomb explosion. IF the earth wasn't in the way, would an a-bomb explosion expand back over itself like the super nova did? And is it common for a super nova (or any kind of nova) to blow out in a rather straight line, instead of something more like a 360&deg; pattern?
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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by MargaritaMc » Tue Feb 11, 2014 4:21 pm

Art: I don't see what the adapted - unattributed - quotation from "The Music Man" has to do with Breaking Science News.

Beyond: I wondered about the straight line, too. More to investigate!
M
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by neufer » Tue Feb 11, 2014 7:12 pm

Beyond wrote:
The beginning of the explosion in the "Deflagration" video reminds me of an atomic bomb explosion. IF the earth wasn't in the way, would an a-bomb explosion expand back over itself like the super nova did?
If the earth's atmosphere was not a factor and the explosive debris doesn't exceed escape velocity
then an a-bomb explosion would fall back on itself due to gravity with little in the way of an expanding mushroom cloud.

http://www.youtube.com/watch?v=SMW9BOELTFc
Beyond wrote:
And is it common for a super nova (or any kind of nova) to blow out in a rather straight line, instead of something more like a 360&deg; pattern?
If 1) the degenerate electron core of the common carbon-oxygen variety of white dwarf reaches fusion ignition temperature prior to attaining the collapse Chandrasekhar limit of 1.44 solar mass

2) and it ignites just off center

it will produce a narrow off-center fusion flame that is unable to widen (since pressure is independent of temperature).

Once that fusion flame reaches the non-degenerate outer (atmospheric) shell of the white dwarf
it is finally able to expand into a mushroom shaped cloud.
http://en.wikipedia.org/wiki/Type_Ia_supernova wrote:<<Type Ia supernovae occur in binary systems (two stars orbiting one another) in which one of the stars is a white dwarf while the other can vary from a giant star to an even smaller white dwarf. A white dwarf is the remnant of a star that has completed its normal life cycle and has ceased nuclear fusion. However, white dwarfs of the common carbon-oxygen variety are capable of further fusion reactions that release a great deal of energy if their temperatures rise high enough.

Physically, carbon-oxygen white dwarfs with a low rate of rotation are limited to below 1.38 solar masses. Beyond this, they re-ignite and in some cases trigger a supernova explosion. Somewhat confusingly, this limit is often referred to as the Chandrasekhar mass, despite being marginally different from the absolute Chandrasekhar limit where electron degeneracy pressure is unable to prevent catastrophic collapse. If a white dwarf gradually accretes mass from a binary companion, the general hypothesis is that its core will reach the ignition temperature for carbon fusion as it approaches the limit. If the white dwarf merges with another star (a very rare event), it will momentarily exceed the limit and begin to collapse, again raising its temperature past the nuclear fusion ignition point. Within a few seconds of initiation of nuclear fusion, a substantial fraction of the matter in the white dwarf undergoes a runaway reaction, releasing enough energy (1–2×1044 J) to unbind the star in a supernova explosion.

This category of supernovae produces consistent peak luminosity because of the uniform mass of white dwarfs that explode via the accretion mechanism. The stability of this value allows these explosions to be used as standard candles to measure the distance to their host galaxies because the visual magnitude of the supernovae depends primarily on the distance.

The Type Ia supernova is a sub-category in the Minkowski-Zwicky supernova classification scheme, which was devised by American astronomer Rudolph Minkowski and Swiss astronomer Fritz Zwicky. There are several means by which a supernova of this type can form, but they share a common underlying mechanism. When a slowly-rotating carbon-oxygen white dwarf accretes matter from a companion, it can exceed the Chandrasekhar limit of about 1.44 solar masses, beyond which it can no longer support its weight with electron degeneracy pressure. In the absence of a countervailing process, the white dwarf would collapse to form a neutron star, as normally occurs in the case of a white dwarf that is primarily composed of magnesium, neon, and oxygen.

The current view among astronomers who model Type Ia supernova explosions, however, is that this limit is never actually attained and collapse is never initiated. Instead, the increase in pressure and density due to the increasing weight raises the temperature of the core, and as the white dwarf approaches about 1% of the limit, a period of convection ensues, lasting approximately 1,000 years. At some point in this simmering phase, a deflagration flame front is born, powered by carbon fusion. The details of the ignition are still unknown, including the location and number of points where the flame begins. Oxygen fusion is initiated shortly thereafter, but this fuel is not consumed as completely as carbon.

Once fusion has begun, the temperature of the white dwarf starts to rise. A main sequence star supported by thermal pressure would expand and cool in order to counterbalance an increase in thermal energy. However, degeneracy pressure is independent of temperature; the white dwarf is unable to regulate the burning process in the manner of normal stars, so it is vulnerable to a runaway fusion reaction. The flame accelerates dramatically, in part due to the Rayleigh–Taylor instability and interactions with turbulence. It is still a matter of considerable debate whether this flame transforms into a supersonic detonation from a subsonic deflagration.

Regardless of the exact details of nuclear burning, it is generally accepted that a substantial fraction of the carbon and oxygen in the white dwarf is burned into heavier elements within a period of only a few seconds, raising the internal temperature to billions of degrees. This energy release from thermonuclear burning (1–2×1044 J) is more than enough to unbind the star; that is, the individual particles making up the white dwarf gain enough kinetic energy to fly apart from each other. The star explodes violently and releases a shock wave in which matter is typically ejected at speeds on the order of 5,000–20000 km/s, roughly 6% of the speed of light. The energy released in the explosion also causes an extreme increase in luminosity. The typical visual absolute magnitude of Type Ia supernovae is Mv = −19.3, with little variation>>
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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by Beyond » Tue Feb 11, 2014 10:15 pm

Thanks neufer.
To find the Truth, you must go Beyond.

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Re: HEAPOW: SN2014J (2014 Feb 03)

Post by MargaritaMc » Wed Feb 12, 2014 10:33 am

There's a set of lecture notes for a 2013 Stony Brook University course entitled Cosmic Catastrophes here:
http://www.astro.sunysb.edu/lattimer/AST301/

SNe 1a are discussed in http://www.astro.sunysb.edu/lattimer/AS ... ast301.pdf
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS