Explanation: This shock wave plows through space at over 500,000 kilometers per hour. Moving toward to bottom of this beautifully detailed color composite, the thin, braided filaments are actually long ripples in a sheet of glowing gas seen almost edge on. Cataloged as NGC 2736, its narrow appearance suggests its popular name, the Pencil Nebula. About 5 light-years long and a mere 800 light-years away, the Pencil Nebula is only a small part of the Vela supernova remnant. The Vela remnant itself is around 100 light-years in diameter and is the expanding debris cloud of a star that was seen to explode about 11,000 years ago. Initially, the shock wave was moving at millions of kilometers per hour but has slowed considerably, sweeping up surrounding interstellar gas.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
Sure, why not? There have been humans around on this planet for -- depending on your definition of human -- anywhere from a few hundred thousand years to a few million years. I imagine they found time to look at the night sky, and an exploding star would have been nicely visible in those pristine, light-pollution-free skies.
A supernova explosion would appear as a new "guest" star in the sky shining brightly for a few months. There are many documented examples from historical records, most famously SN 1054 in the year 1054, which produced the well known Crab Nebula supernova remnant.
The picture as seen is more likely the outer edge of a 'bubble' of debris and gas, not a 'pencil' in shape. We're only seeing the illuminated area of one section of the explosion 'bubble'...in my opinion.
donn32901@yahoo.com wrote:The picture as seen is more likely the outer edge of a 'bubble' of debris and gas, not a 'pencil' in shape. We're only seeing the illuminated area of one section of the explosion 'bubble'...in my opinion.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor
http://en.wikipedia.org/wiki/Deutsche_Luft-Reederei wrote:
<<Deutsche Luft-Reederei (D.L.R), founded in 1917, was the first German airline to use heavier than air aircraft. DELAG was the first airline in the world, but flew lighter than air airships supplied by the Zeppelin company. D.L.R.'s first air services began on 5 February 1919. The company used a stylised crane, designed by Professor Otto Firle, as its logo. The airline merged to became part of Aero Lloyd AG in 1923, who again merged to became part of Deutsche Luft Hansa in 1926, which also adopted the crane logo.>>
Sure, why not? There have been humans around on this planet for -- depending on your definition of human -- anywhere from a few hundred thousand years to a few million years. I imagine they found time to look at the night sky, and an exploding star would have been nicely visible in those pristine, light-pollution-free skies.
One should note, however, that it would have been problematically low on the southern horizon for observation from
the "cradle of civilization" 11,600 years ago (assuming that they didn't have other things on their minds at night):
http://en.wikipedia.org/wiki/Vela_Supernova_Remnant wrote:
The Vela supernova remnant (Declination 11,600 years ago: -55º) is a supernova remnant in the southern constellation Vela. Its source supernova exploded approximately 11,000-12,300 years ago. The association of the Vela supernova remnant with the Vela pulsar, made by astronomers at the University of Sydney in 1968, was direct observational proof that supernovae form neutron stars.
<<The Natufian culture (Latitude~ 32º N) was an Epipaleolithic culture that existed from 13,000 to 9,800 years ago in the Levant, a region in the Eastern Mediterranean. The Natufian developed in the same region as the earlier Kebaran complex, and is generally seen as a successor which developed from at least elements within that earlier culture. It was unusual in that it was sedentary, or semi-sedentary, before the introduction of agriculture. The Natufian communities are possibly the ancestors of the builders of the first Neolithic settlements of the region, which may have been the earliest in the world. There is some evidence for the deliberate Natufians made use of wild cereals. Animals hunted include gazelles.
The Natufian had a microlithic industry, based on short blades and bladelets. The microburin-technique was used. Geometric microliths include lunates, trapezes and triangles. Sickle blades appear for the first time. The characteristic sickle-gloss shows that they have been used to cut the silica-rich stems of cereals and form an indirect proof for incipient agriculture. Shaft straighteners made of ground stone indicate the practice of archery. There are heavy ground-stone bowl mortars as well. There was a rich bone industry, including harpoons and fish hooks. Stone and bone were worked into pendants and other ornaments. There are a few human figurines made of limestone (El-Wad, Ain Mallaha, Ain Sakhri), but the favourite subject of representative art seems to have been animals. Ostrich-shell containers have been found in the Negev.>>
<<The process of sedentarization is first thought to have occurred around 12,000 BCE in the Levant region of southwest Asia though other regions around the world soon followed. The emergence of civilization is generally associated with the Neolithic, or Agricultural Revolution, which occurred in various locations between 8,000 and 5,000 BCE, specifically in southwestern/southern Asia, northern/central Africa and Central America.This revolution marked the beginning of stable agriculture and animal domestication which enabled economies and cities to develop.
Map of the world showing approximate centers of origin of agriculture and its spread in prehistory: the Fertile Crescent (11,000 BP), the Yangtze and Yellow River basins (9000 BP) and the New Guinea Highlands (9000–6000 BP), Central Mexico (5000–4000 BP), Northern South America (5000–4000 BP), sub-Saharan Africa (5000–4000 BP, exact location unknown), eastern USA (4000–3000 BP).>>
11,000 years ago? That would be somewhere around 9,000BCE. There would have been lots of folks around to see it, particularly folks standing watch all night to keep the wolves at bay.
http://heritage.stsci.edu/2003/16/supplemental.html - shows the entire Vela supernova remnant, including a pulsar. This portion of the nebula is highlighted by a tiny box toward the edge of the debris field. Kind of puts that wavy sheet in perspective.
<<Human habitation of the Australian continent is estimated to have begun between 42,000 and 48,000 years ago, possibly with the migration of people by [ice age induced] land bridges and short sea-crossings from what is now South-East Asia. These first inhabitants may have been ancestors of modern Indigenous Australians. At the time of European settlement in the late 18th century, most Indigenous Australians were hunter-gatherers, with a complex oral culture and spiritual values based on reverence for the land and a belief in the Dreamtime. The Torres Strait Islanders, ethnically Melanesian, were originally horticulturalists and hunter-gatherers.>>
Last edited by neufer on Mon Sep 24, 2012 8:20 pm, edited 1 time in total.
das wrote:
Ok, I don't understand how a shock wave can travel through (the vacuum of) space.
In many respects space is NOT a vacuum.
http://en.wikipedia.org/wiki/Interstellar_medium wrote:
<<The interstellar medium is composed of multiple phases, distinguished by whether matter is ionic, atomic, or molecular, and the temperature and density of the matter. Magnetic fields and turbulent motions also provide pressure in the ISM, and are typically more important dynamically than the thermal pressure is. In cool, dense regions of the ISM, matter is primarily in molecular form, and reaches number densities of 106 molecules per cm3 [corresponding to a mean free path of just 0.0001 light years].>>
das wrote:Ok, I don't understand how a shock wave can travel through (the vacuum of) space.
Anyone?
A shock wave doesn't travel through a vacuum. The shock wave is traveling through the dispersing cloud of material that was ejected when the progenitor star exploded. (As Art noted, there may also be interactions with the interstellar medium- also not a vacuum.)
Chris
*****************************************
Chris L Peterson
Cloudbait Observatory https://www.cloudbait.com
So if I'm understanding you, the physics is similar to a wave traveling through water or air, but simply through a much sparser medium? 106 molecules per cm3 does seem like a lot more than I had thought was the case.
And this is not the same as what are called 'gravitational waves'? That would be a completely different physical phenomena, wouldn't it?
orin stepanek wrote:
Kind of reminds me of the Bird of Paradise flower
Click to play embedded YouTube video.
And early South Africans may have observed the Vela supernova.
http://en.wikipedia.org/wiki/Strelitzia wrote:
<<Strelitzia is a genus of five species of perennial plants, native to South Africa. The genus is named after the duchy of Mecklenburg-Strelitz, birthplace of Queen Charlotte of the United Kingdom. A common name of the genus is bird of paradise flower, because of a supposed resemblance of its flowers to the bird of paradise. In South Africa it is commonly known as a crane flower. The species S. nicolai is the largest in the genus, reaching 10 m tall, with stately white and blue flowers. The flowers are produced in a horizontal inflorescence emerging from a stout spathe. They are pollinated by sunbirds, which use the spathe as a perch when visiting the flowers; the weight of the bird on the spathe opens it to release the pollen onto the bird's feet, which is then deposited on the next flower it visits.>>
NGC 2736: The Pencil Nebula
