Thor's Helmet (NGC 2359) and Planetary Nebula (2009 Mar 12)

[bearkite]

I must thank Rogelio & Ray for this fantastic image of one of my favorite visual objects.

I find myself returning to this object almost every time I'm out during the winter. And, have often thought that this needed to be done (imaged) in a wide-field format.

Not only have they done so, but have done it in a spectacular manner...

Thanks Guys...

[orin stepanek]

http://apod.nasa.gov/apod/ap090312.html

It indeed spectacular! 8)

Orin

[Doum]

Quote, "the central star is an extremely hot giant thought to be in a brief, pre- supernova stage of evolution."

Now, when will that supernova explosion happen. 15000 tousands light years away seem far enough for security. So i would of enjoy seeing it explode. Thats why i ask the question. Is there a theory that say how long, after a pre-supernova stage, it take for a supernova to explode?

[neufer]

http://antwrp.gsfc.nasa.gov/apod/ap080117.html
http://antwrp.gsfc.nasa.gov/apod/ap080522.html

<<Wolf-Rayet stars (often referred to as WR stars) are evolved, massive stars (over 20 solar masses), which are losing mass rapidly by means of a very strong stellar wind, with speeds up to 2000 km/s. While our own Sun loses approximately 10−14 solar masses every year, Wolf-Rayet stars typically lose 10−5 solar masses a year.

Wolf-Rayet stars are very hot, with surface temperatures in the range of 25,000 K to 50,000 K. It is believed that the star in the galaxy NGC 2770 that exploded into a supernova on January 9, 2008 — SN 2008D, the first supernova ever observed in the act of exploding — was a Wolf-Rayet star.
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. Observation history
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http://antwrp.gsfc.nasa.gov/apod/ap080813.html
http://antwrp.gsfc.nasa.gov/apod/ap060706.html
http://antwrp.gsfc.nasa.gov/apod/ap081107.html
http://antwrp.gsfc.nasa.gov/apod/ap000802.html
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In 1867, astronomers using the 40 cm Foucault telescope at the Paris Observatory, discovered three stars in the constellation Cygnus (now designated HD191765, HD192103 and HD192641), that displayed broad emission bands on an otherwise continuous spectrum. The astronomer's names were Charles Wolf and Georges Rayet, and thus this category of stars became named Wolf-Rayet (WR) stars. Most stars display absorption bands in the spectrum, as a result of overlaying elements absorbing light energy at specific frequencies. The number of stars with emission lines is quite low, so these were clearly unusual objects.
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The nature of the emission bands in the spectra of a Wolf-Rayet star remained a mystery for several decades. Edward C. Pickering theorized that the lines were caused by an unusual state of hydrogen, and it was found that this "Pickering series" of lines followed a pattern similar to the Balmer series, when half-integral quantum numbers were substituted. It was later shown that the lines resulted from the presence of helium; a gas that was discovered in 1868.
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http://antwrp.gsfc.nasa.gov/apod/ap040421.html
http://antwrp.gsfc.nasa.gov/apod/ap030410.html
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By 1929, the width of the emission bands was being attributed to the Doppler effect, and hence that the gas surrounding these stars must be moving with velocities of 300–2400 km/s along the line of sight. The conclusion was that a Wolf-Rayet star is continually ejecting gas into space, producing an expanding envelope of nebulous gas. The force ejecting the gas at the high velocities observed is radiation pressure.
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In addition to helium, emission lines of carbon, oxygen and nitrogen were identified in the spectra of Wolf-Rayet stars. In 1938, the International Astronomical Union classified the spectra of Wolf-Rayet stars into types WN and WC, depending on whether the spectrum was dominated by lines of nitrogen or carbon-oxygen respectively.
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. Description
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Wolf-Rayet stars are a normal stage in the evolution of very massive stars, in which strong, broad emission lines of helium and nitrogen ("WN" sequence) or helium, carbon, and oxygen ("WC" sequence) are visible. Due to their strong emission lines they can be identified in nearby galaxies. About 230 Wolf-Rayets are known in our own Milky Way Galaxy, about 100 are known in the Large Magellanic Cloud, while only 12 have been identified in the Small Magellanic Cloud.
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Conti (1976) originally proposed that the WR stars as a class are descended from massive O-stars in which the strong stellar winds characteristic of extremely luminous stars have ejected the unprocessed outer H-rich layers. The characteristic emission lines are formed in the extended and dense high-velocity wind region enveloping the very hot stellar photosphere, which produces a flood of UV radiation that causes fluorescence in the line-forming wind region. This ejection process uncovers in succession, first the nitrogen-rich products of CNO cycle burning of hydrogen (WN stars), and later the carbon-rich layer due to He burning (WC & WO stars). Most of these stars are believed finally to progress to become supernovae of Type Ib or Type Ic. A few (roughly 10%) of the central stars of planetary nebulae are, despite their much lower (typically ~0.6 solar) masses, also observationally of the WR-type; i.e., they show emission line spectra with broad lines from helium, carbon and oxygen. Denoted [WR], they are much older objects descended from evolved low-mass stars and are closely related to white dwarfs, rather than to the very young, very massive stars that comprise the bulk of the WR class.
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It is possible for a Wolf-Rayet star to progress to a "collapsar" stage in its death throes: This is when the core of the star collapses to form a black hole, pulling in the surrounding material. This is thought to be the precursor of a long gamma-ray burst.
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The best known (and most visible) example of a Wolf-Rayet star is Gamma 2 Velorum (γ² Vel), which is a bright star visible to those located south of 40 degrees northern latitude. One of the members of the star system (Gamma Velorum is actually at least six stars) is a Wolf-Rayet star. Due to the exotic nature of its spectrum (bright emission lines in lieu of dark absorption lines) it is dubbed the "Spectral Gem of Southern Skies".>>

[Pappa Charlie]

Good Morning
Is the circular object in the lower left corner of APOD of Thor's Helment a part of Thor's Helment or is it incidental to the photo. I almost missed it until I looked at the full resolution version of this beautiful picture.
P.C.

[neufer]

Is the circular object in the lower left corner of APOD of Thor's Helment a part of Thor's Helment or is it incidental to the photo. I almost missed it until I looked at the full resolution version of this beautiful picture.

It is planetary nebula: PHR0719-1222

"A close look at the lower left corner of the image might identify the object of the cosmic stare as a faint, round nebula."

[Pappa Charlie]

Thank you Art for that information.

P.C.

[Doum]

So i have to have a million year to go before i see it become a supernova.

http://antwrp.gsfc.nasa.gov/apod/ap000802.html

Hmmm well ok ill do something else then.

[Chris Peterson]

So i have to have a million year to go before i see it become a supernova.

Or maybe it will happen today.

[Doum]

[neufer]

So i have to have a million year to go before i see it become a supernova.

Or maybe it will happen today.

Let's hope not :

<<According to the Prose Edda, Thor was to meet his death during Ragnarök (Old Norse "Final destiny of the gods"):

The serpent Jörmungandr opens its gaping maw, yawning widely in the air, and is met in combat by Thor. Thor furiously fights the serpent, defeating it, but Thor is only able to take nine steps afterward before collapsing. After this, people flee their homes, and the sun becomes black while the earth sinks into the sea, the stars vanish, steam rises, and flames touch the heavens.>>

[aristarchusinexile]

So i have to have a million year to go before i see it become a supernova.

Or maybe it will happen today.

Let's hope not :

Ahh .. our pitiable lack of belief in perfect eternity .. holding us back from perfection.