And I'm just farting about, too"The wretched world lies now under the tyranny of foolishness; things are believed by Christians of such absurdity as no one ever could aforetime induce the heathen to believe." - Agobard of Lyons, ca. 830 AD
More than four years after light from supernova 1987A first reached Earth, radiation remains the key tool for investigating the hidden energy sources powering this exploded star. Soon after the supernova appeared, emissions of ultra-violet, infrared and visible light grew steadily fainter, following a predicted decay curve. But changes in the supernova's "light curve" over the past year now leave astronomers puzzled.
The changes hint at two dramatic possibilities: the abundance of elements in 1987A may differ widely from that in our solar system, or a new energy source -- perhaps a dense, spinning sphere of neutrons known as a pulsar -- lies hidden at the core of the object.
Some of the gammas excite atoms in the cloud of debris surrounding 1987A, causing the atoms to emit infrared and visible light observable from Earth. Based on the abundance of cobalt-65 as well as its half-life, scientists believe that until recently it provided the supernova's chief fuel.
But as observations of 1987A hit the three-year mark, little cobalt-56 remained, and the light curve flattened, reports Walker, Nicholas B. Suntzeff and their colleagues in the September ASTRONOMICAL JOURNAL. The flatter curve matches the slower decay of another isotope, cobalt-57, which the supernova produced in smaller amounts, the group notes. Another team, at the European Southern Observatory in La Silla, Chile, reports similar results.
So far so good. But although the shape of the light curve mimics the decay of cobalt-57, the magnitude of the curve -- indicating the amount of light now emitted by 1987A -- exceeds that predicted by theory, both teams say. One way to explain the greater emissions, note Suntzeff and his colleagues, is to assume that the supernova produced a ratio of cobalt-57 to cobalt-56 five times the ratio typical in our solar system. They will report these results in an upcoming ASTROPHYSICAL JOURNAL LETTERS.
The unusual ratio may pose a problem, several astronomers assert, even though the turbulent environment of 1987A -- located 160,000 light-years from Earth -- differs from that of the solar system. While nuclear burning inside stars creates the lighter elements, researchers believe it requires the violence of a supernova explosion to produce the heaviest materials, such as radioactive nickel, which then decays to cobalt, and ultimately to iron. Over time, thousands of supernovas spew out their contents, thus determining the abundance of heavy elements in our galaxy and others. According to this model, the abundance of isotopes created by individual supernovas should not differ radically from the ratio found near Earth.
Suntzeff's team suggests another explanation for the new findings, one that no longer requires 1987A's ratio to conflict with our solar system's. A constant energy source lurking at the core of the supernova could also account for the larger light output -- perhaps a pulsar, long sought but never observed in 1987A, or a black hole. While such sources generally produce a totally flat light curve rather than the slowly declining one observed, Suntzeff says the latest data indicate 1987A's curve appears to be flattening.
Many astronomers caution that the findings provide only sketchy evidence for a pulsar. And absorption of the supernova's far-infrared emissions by Earth's atmosphere complicates efforts to measure the supernova's total brightness.
A study last month with NASA's Gamma Ray Observatory (GRO) may answer the cobalt ratio question, says Mark Leising of Clemson (S.C.) University. GRO measured the spectra of gamma rays from 1987A, which should allow researchers to calculate the amount of cobalt-57 produced by the supernova. In 1988, the Solar Maximum Mission satellite precisely calculated 1987A's quantity of cobalt-56. Comparing both isotopes will directly determine the relative abundance of cobalt-57. Very early results, Leising notes, suggest that GRO did not find the large increase inferred from the ground-based measurements.
Added by edit: Test Test Test
Edited by Percy, : Performance testing...
Edited by Percy, : Performance testing...
Edited by Adminnemooseus, : Testing editing while suspended.
The information at the link Jar gave in message 7 explains the quoting codes about as well as it can be done. Again, that is at here.
My guess is your problem is how the get the desired text into the quote box. That is done through copying and pasting just like you can do in a word processor.
I find it easiest to right click on the "reply" button, and then choose "open in a new tab" or "open in a new window". That way you have separate tabs/windows for the message you wish to reply to and the text entry box. You then don't have to scroll up and down a page to see both.
To copy, highlight the text you wish to copy and hit "control c". Then go to the text entry box, find the location you wish to enter the text, and hit "control v". That will paste the copied text. Then you need to put the desired startquote code in front of that text, and the corresponding endquote code at the end of that text. Be careful to use the normal slash (/} and not the backslash (\).
Quite a while back we had a "reply with quote" button, that would automatically quote the entire message. Various problems of people misusing it caused us to disable that feature.
When replying, please note that there are two types of "reply" buttons. If you are replying to a specific message, use the little reply button at the bottom of that message. That causes the "reply to" and "reply from" information to be displayed.
If you are making a general reply, use the "Gen Reply" button at the top or bottom of the page. Be careful not to use the "New Topic" button.