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- Joined: Sat Sep 18, 2010 10:57 pm
- AKA: mud
- Location: New Mexico, USA
Hi, So, I'm on something like Episode 8 of "Cosmos." Sagan just said, "There's been no super nova explosion in our province of the galaxy since the invention of the telescope." Well, that was 30 yrs. ago. i can't trust my memory, so I can't swear what's true. Has there been one seen since? For some reason, I think there has.
- Vacationer at Tralfamadore
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- Joined: Mon Jan 21, 2008 1:57 pm
- Location: Alexandria, Virginia
So, I'm on something like Episode 8 of "Cosmos." Sagan just said, "There's been no super nova explosion in our province of the galaxy since the invention of the telescope." Well, that was 30 yrs. ago. i can't trust my memory, so I can't swear what's true. Has there been one seen since? For some reason, I think there has.
- Cassiopeia A Light Echoes in Infrared Credit: O. Krause (Steward Obs.) et al., SSC, JPL, Caltech, NASA <<[url=http://antwrp.gsfc.nasa.gov/apod/ap050615.html][b]Explanation[/b][/url]: Why is the image of Cassiopeia A changing? Two images of the nearby supernova remnant taken a year apart in infrared light appear to show outward motions at tremendous speeds. This was unexpected since the supernova that created the picturesque nebula was seen 325 years ago. The reason is likely light echoes. Light from the supernova heated up distant ambient dust that is just beginning to show its glow. As time goes by, more distant dust lights up, giving the appearance of outward motion. The above image is a composite of X-ray, optical, and infrared light exposures that have been digitally combined. The infrared light image was taken by the orbiting Spitzer Space Telescope and was used in the discovery of the light echo. The portion of Cassiopeia A shown spans about 15 light years and lies 10,000 light years away toward the constellation of Cassiopeia.>>
- Cassiopeia A in a Million Credit: U. Hwang (GSFC/UMD), J.M. Lamming (NRL), et al., CXC, NASA, [url=http://antwrp.gsfc.nasa.gov/apod/ap040826.html][b]Explanation[/b][/url]: One million seconds of x-ray image data were used to construct this view of supernova remnant Cassiopeia A, the expanding debris cloud from a stellar explosion. The stunningly detailed image from the Chandra Observatory will allow an unprecedented exploration of the catastrophic fate that awaits stars much more massive than the Sun. Seen in false-color, Cas A's outer green ring, 10 light-years or so in diameter, marks the location of the expanding shock from the original supernova explosion. At about 10 o'clock around the ring, a structure extends beyond it, evidence that the initial explosion may have also produced energetic jets. Still glowing in x-rays, the tiny point source near the center of Cas A is a neutron star, the collapsed remains of the stellar core. While Cas A is about 10,000 light-years away, light from the supernova explosion first reached Earth just over 300 years ago.>>
<<Cassiopeia A (Cas A) is a supernova remnant in the constellation Cassiopeia and the brightest astronomical radio source in the sky. The supernova occurred approximately 11,000 light-years (3.4 kpc) away in the Milky Way. The expanding cloud of material left over from the supernova is now approximately 10 light-years (3.1 pc) across. Despite its radio brilliance, however, it is extremely faint optically, and is only visible on long-exposure photographs.
It is believed that first light from the stellar explosion reached Earth approximately 300 years ago but there are no historical records of any sightings of the progenitor supernova, probably due to interstellar dust absorbing optical wavelength radiation before it reached Earth (although it is possible that it was recorded as a sixth magnitude star 3 Cassiopeiae by John Flamsteed on August 16, 1680). Possible explanations lean toward the idea that the source star was unusually massive and had previously ejected much of its outer layers. These outer layers would have cloaked the star and reabsorbed much of the light released as the inner star collapsed.
Calculations working back from the currently observed expansion point to an explosion around 1667. Observations of the exploded star through the Hubble telescope have shown that, despite the original belief that the remnants were expanding in a uniform manner, there are 2 opposing jets of debris that are traveling at 32 million miles per hour. This speed is estimated to be 20 million miles per hour faster than the rest of the debris. When the view of the expanding star uses colors to differentiate materials of different chemical compositions, it shows that similar materials often remain gathered together in the remnants of the explosion.
Cas A is the strongest radio source in the sky beyond our solar system, and was among the first discrete sources to be found, in 1947. The optical component was first identified in 1950.
In 1979, Shklovsky predicted that Cas A had a black hole. In 1999, the Chandra X-Ray Observatory found a "hot point-like source" close to the center of the nebula that is quite likely the neutron star or black hole predicted but not previously found. Although Cas X-1 (or Cas XR-1), the apparent first X-ray source in the constellation Cassiopeia was not detected during the June 16, 1964, Aerobee sounding rocket flight, it was considered as a possible source. Cas X-1 is Cas A, a Type II SNR at RA 23h 18m Dec +58° 30′.
Recently, infrared echo of Cassiopeia A explosion was observed on nearby gas clouds using Spitzer Space Telescope. The recorded spectrum proved the supernova was of Type IIb, meaning it resulted from the internal collapse and violent explosion of a massive star, most probably a red supergiant with a helium core which had lost almost all of its hydrogen envelope. This was the first observation of the infrared echo of a supernova which explosion had not been directly observed which opens up the possibility of studying and reconstructing past astronomical events.>>