Starship Asterisk*

Stevenson wrote:My explanation:

In other words: Not 400 years earlier from now (the present time on Earth) but

- the star that went supernova lies about 160,000 light years away from us.

- It went supernova ‘400 years earlier’ that is (160,000 – 400 = 159,600) years ago.

Only then the light from the initial blast should have been seen on Earth 400 years ago; the light of the initial blast that took 160,000 light years to reach Earth.

DavidLeodis wrote:...
Through the Hubble Space Telescope link I came on this "Pointing Accuracy: In order to take images of distant, faint objects, Hubble must be extremely steady and accurate. The telescope is able to lock onto a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of 1 mile". Wow, that is staggering precision.
...

garrry wrote:Well, it looks like a ring, not a sphere. If it was spherical you would not be able to see the centre. The other point is that the assumption is it is from a supernova. From looking at the photo it appears not to be. A supernova would produce a shell, not a ring. Would not it be more prudent to say "we do not know the mechanism that caused this" Surely Astronomers do not know exactly how the Universe works. There are only assumptions. The better the instruments we put out there, the more we realise the less we know....

Chris Peterson wrote:

Third Flowerpot Man wrote:If I may put the same question in a different manner, "Has the Earth travelled around the sun approximately 400 times or 160,400 times since the event occurred?". From what I understand of the answers given, the answer is the latter, i.e. up until today, the Earth has revolved around the sun approximately 160,400 times since the event occurred.

Hope this helps.

Not really <g>. It's the same question, and the same answer. It depends on the definition you want to use for "when" the event occurred. It would have been observed about 400 years ago, or 400 trips around the Sun. Most astronomers would say that's when it happened, because there would be no point in correcting for the time it took the light to get here. If they were trying to place it in context with another event, however, they might change the time reference to include the light time, in which case they might say it happened 160,400 years ago.

One reason to avoid that latter time, however, is that most objects at this distance have their distances poorly known. There is probably a huge uncertainty on that 160,000 light year figure. So rather than using a number that has to be adjusted every time we get a better distance estimate, you can simply use when it was observed- a figure that won't change.

Chris Peterson wrote:

Cahethe wrote:"why wasn't this supernova seen 400 years ago when light from the initial blast should have passed the Earth?"

Perhaps it happened on the daylight side of the sky, for a short time?

Supernova hold near their peak brightness for many days, so if it was bright enough to be visible at all, it should not have gone unnoticed (even if it went unrecorded).

garrry wrote:Well, it looks like a ring, not a sphere. If it was spherical you would not be able to see the centre. The other point is that the assumption is it is from a supernova. From looking at the photo it appears not to be. A supernova would produce a shell, not a ring. Would not it be more prudent to say "we do not know the mechanism that caused this" Surely Astronomers do not know exactly how the Universe works. There are only assumptions. The better the instruments we put out there, the more we realise the less we know....

Third Flowerpot Man wrote:If I may put the same question in a different manner, "Has the Earth travelled around the sun approximately 400 times or 160,400 times since the event occurred?". From what I understand of the answers given, the answer is the latter, i.e. up until today, the Earth has revolved around the sun approximately 160,400 times since the event occurred.

Hope this helps.

Chris Peterson wrote:

Stevenson wrote:

Hawkings wrote:Why wasn't it seen 400 years ago? You said it was 160,000 light years away. That means the light from the super nova would take 160,000 years to get here, therefore the supernova happened more than 160,000 years ago, not 400...

I have the same question and no disrespect but a bit better/more detailed answer shall be greatly appreciated.

"When" an event happens can be defined in different ways. The vast majority of time, the only definition that is really useful is when that event is observed. So most of the time, this is what is meant when a time is given. There is no correction for the distance, because it doesn't matter. We can say this supernova happened 400 years ago, because in a very real sense, it did.

Chris Peterson wrote:

Cahethe wrote:"why wasn't this supernova seen 400 years ago when light from the initial blast should have passed the Earth?"

Perhaps it happened on the daylight side of the sky, for a short time?

Supernova hold near their peak brightness for many days, so if it was bright enough to be visible at all, it should not have gone unnoticed (even if it went unrecorded).

Cahethe wrote:"why wasn't this supernova seen 400 years ago when light from the initial blast should have passed the Earth?"

Perhaps it happened on the daylight side of the sky, for a short time?

http://chandra.harvard.edu/photo/2008/snr0509/ wrote:
SNR 0509-67.5: Action Replay Of Powerful Stellar Explosion

Credit: X-ray: NASA/CXC/Rutgers/J.Warren, J.Hughes; Optical (Light Echo): NOAO/AURA/NSF/Harvard/A.Rest et al.; Optical (LMC): NOAO/AURA/NSF/S.Points, C.Smith & MCELS team

---

<<This combination of X-ray and optical images shows the aftermath of a powerful supernova explosion in the Large Magellanic Cloud (LMC), a small galaxy about 160,000 light years from Earth. The debris from this explosion, the supernova remnant SNR 0509-67.5, is shown in a Chandra X-ray Observatory image (upper inset), where the lowest energy X-rays are shown in red, the intermediate energies are green and the highest energies are blue. In 2004, scientists used Chandra to show that SNR 0509-67.5 was likely caused by a Type Ia supernova, using an analysis of the elements, such as silicon and iron, that were detected. A Type Ia is thought to result from a white dwarf star in a binary system that reaches a critical mass and explodes.

The light echo image (lower inset), from the National Science Foundation's Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile, shows optical light from the original supernova explosion that has bounced off dust clouds in the neighboring regions of the LMC (the light echoes are shown in blue and stars in orange). The light from these echoes travels a longer path than the light that travels straight toward us, and so can be seen hundreds of years after the supernova itself. This image is one of a sequence of 5 images taken between 2001 and 2006 that are shown separately in a time-lapse movie.

The large optical image is from the Magellanic Cloud Emission Line Survey (MCELS), obtained with the University of Michigan's 0.9-meter Curtis Schmidt telescope at CTIO. Emission lines of hydrogen (H-alpha) are red, singly-ionized sulfur is green and doubly-ionized oxygen is blue. The image highlights regions of star formation in the LMC, including supernova remnants and giant structures carved out by multiple supernovas.

For the first time astronomers have used two methods - X-ray observations of a supernova remnant and optical observations of the expanding light echoes from the explosion - to estimate the energy of a supernova explosion. In two separate papers, astronomers concluded that the supernova occurred about 400 years ago (in Earth's time frame), and was unusually bright and energetic. This is the best ever determination of the power of a supernova explosion long after it was visible from Earth.

In the new optical study spectra of the light echo, obtained with Gemini Observatory, were used to confirm that the supernova was a Type Ia and to unambiguously determine the particular class of explosion and therefore its energy. In the new X-ray study, spectra from Chandra and ESA's XMM-Newton Observatory were then independently used to calculate the amount of energy involved in the original explosion, using an analysis of the supernova remnant and state-of-the-art explosion models. The X-ray work also concluded that the explosion was an especially energetic and bright variety of Type Ia supernova, confirming the validity of the explosion models.>>

hstarbuck wrote:
Maybe there is a Polynesian petroglyph or chant that tells of this light 400 years ago.
They did, after all, navigate vast distances using the stars.

http://en.wikipedia.org/wiki/History_of_Easter_Island wrote:
<<Early European visitors to Easter Island recorded the local oral traditions about the original settlers. In these traditions, Easter Islanders claimed that a chief Hotu Matu'a arrived on the island in one or two large canoes with his wife and extended family. Published literature suggests the island was settled around 300-400 CE, or at about the time of the arrival of the earliest settlers in Hawaii [a chief Obama with his wife and extended family]. Some scientists say that Easter Island was not inhabited until 700-800 CE. This date range is based on glottochronological calculations and on three radiocarbon dates from charcoal that appears to have been produced during forest clearance activities. Moreover a recent study which included radiocarbon dates from what is thought to be very early material suggests that the island was settled as recently as 1200 CE. This seems to be supported by a 2006 study of the island's deforestation, which could have started around the same time. The first-recorded European contact with the island was on 5 April (Easter Sunday) 1722 when Dutch navigator Jacob Roggeveen visited for a week. Fossil pollen analysis shows that the main trees on the island had gone 72 years earlier in 1650. The civilization of Easter Island was long believed to have degenerated drastically during the century before the arrival of the Dutch, as a result of overpopulation, deforestation[, LMC supernovae] and exploitation of an extremely isolated island with limited natural resources.>>

http://en.wikipedia.org/wiki/Polynesian_navigation wrote:
<<Polynesian navigation was a system of navigation used by Polynesians to make long voyages across thousands of miles of open ocean. Navigators traveled to small inhabited islands using only their own senses and knowledge passed by oral tradition from navigator to apprentice, often in the form of song. In order to locate directions at various times of day and year, navigators in Eastern Polynesia memorized important facts: the motion of specific stars, and where they would rise and set on the horizon of the ocean; weather; times of travel; wildlife species (which congregate at particular positions); directions of swells on the ocean, and how the crew would feel their motion; colors of the sea and sky, especially how clouds would cluster at the locations of some islands; and angles for approaching harbors.

These wayfinding techniques along with outrigger canoe construction methods, were kept as guild secrets. Generally each island maintained a guild of navigators who had very high status; in times of famine or difficulty these navigators could trade for aid or evacuate people to neighboring islands. To this day, original traditional methods of Polynesian Navigation are still taught in the Polynesian outlier of Taumako Island in the Solomon Islands.>>

Chris Peterson wrote:

BMAONE23 wrote:

davidgin50 wrote:"why wasn't it seen 400 years ago" Maybe it was but how many people were capable of leaving written records of such events in the Southern Hemisphere in 1611?

1611 is when the King James version of the bible was published for the masses

Yeah. In the northern hemisphere. Most of the southern hemisphere masses couldn't read, and didn't even have writing systems.

hstarbuck wrote:Maybe there is a Polynesian petroglyph or chant that tells of this light 400 years ago. They did, after all, navigate vast distances using the stars.

Chris Peterson wrote:

BMAONE23 wrote:

davidgin50 wrote:"why wasn't it seen 400 years ago" Maybe it was but how many people were capable of leaving written records of such events in the Southern Hemisphere in 1611?

1611 is when the King James version of the bible was published for the masses

Yeah. In the northern hemisphere.
Most of the southern hemisphere masses couldn't read, and didn't even have writing systems.