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Fraser
2004-Nov-04, 06:20 PM
SUMMARY: European astronomers have produced the first image of an object using high energy gamma rays - the most penetrating form of radiation known. The image is of a supernova remnant called RX J1713.7-3946, which exploded 1,000 years ago. Over time, a ring of material has expanded to twice the diameter of the Moon in the sky. If you had gamma ray eyes, you would be able to see a large ring in the sky every night. This also helps solve a 100 year mystery about the origin of cosmic rays; the remnant seems to be acting as a particle accelerator.

What do you think about this story? Post your comments below.

om@umr.edu
2004-Nov-04, 06:27 PM
It's great to see another technique used to study supernova debris.

I am puzzled that the size of the RX J1713.7-3946 debris after 1,000 years is compared to "the diameter of the Moon in the sky", instead of giving this number in terms of AU or light-years.

It is interesting that this supernova remnant is "acting like a giant particle accelerator in space". In a paper submitted for publication we have reported evidence that the Sun also acts as a particle accelerator, accelerating H+ ions upward from the core and then departing in the solar wind.

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Nov-04, 06:40 PM
Originally posted by om@umr.edu@Nov 4 2004, 06:27 PM
I am puzzled that the size of the RX J1713.7-3946 debris after 1,000 years is compared to "the diameter of the Moon in the sky", instead of giving this number in terms of AU or light-years.
This article left out a lot of bits of details that would be interesting to you or me. For example, it mentioned HESS, but it didn't really tell us the energy of the gamma rays being observed. In fact there have previously been gamma-ray images more detailed than this, but they were of the low-energy gamma-rays, in the hundreds of KeV range.

What really makes THIS image new is that it shows the source locations for very high energy gamma-rays [eight to twelve orders of magnitude more energetic than the ones observed by the Compton observatory] which are detected by the showers of partcles created as they slam into the atmosphere.

These are the gamma-rays whose source is a mystery. This is a very significant demonstration of something that had previously been suspected. The question with RX J1713.7-3946 [SN1006a] was whether the HEGRs came from the shock fronts in the expanding clouds, or only from the remaining core. This image clearly shows them coming from the shock fronts.

om@umr.edu
2004-Nov-05, 03:17 PM
Thanks, Anton.

Our studies suggest that this supernova remnant, "acting like a giant particle accelerator in space", "the source locations for very high energy gamma-rays", may be

like the giant particle accelerator at the core of the Sun that accelerates H+ ions upward and causes 3 x 10^43 H+ ions to depart the Sun's surface each year in the solar wind.

In other words, Anton, the solar wind may be like high-energy cosmic rays that have been attenuated and altered after passing outward from the Sun's core.

With kind regards,

Oliver
http://www.umr.edu/~om

VanderL
2004-Nov-05, 03:41 PM
This image clearly shows them coming from the shock fronts.

I don't know enough about particle accelerations, but isn't it logical that they are accelerated by electro-magnetic fields? Why is that happening in the shock fronts? Imo, it is significant that they are found coming from the shell.
Btw, there is an overlay of X-ray and Gamma-ray, and it seems to me they are not exactly the same sources, is it a detection problem or is it also expected?

Cheers

antoniseb
2004-Nov-05, 03:54 PM
Originally posted by om@umr.edu@Nov 5 2004, 03:17 PM
like the giant particle accelerator at the core of the Sun that accelerates H+ ions upward and causes 3 x 10^43 H+ ions to depart the Sun's surface each year in the solar wind.
If I remember correctly, you are claiming that the H+ ions you are referring to are coming out of a neutron-star-fragment at about 10 to 22 MeV, and converting to protons through neutron decay [somehow avoiding being pulled back into the gravitational well of the neutron-star-fragment]. These protons then find their way through 430,000 miles of dense gasses. After all that, you say that they come out with the energy we see in the solar wind.

Somehow you are trying to say that this is similar to the source of the gamma rays [not protons] which have a trillion times as much energy as the supposed solar protons. I don't see the similarity.

om@umr.edu
2004-Nov-05, 05:58 PM
Originally posted by VanderL@Nov 5 2004, 03:41 PM

This image clearly shows them coming from the shock fronts.

I don't know enough about particle accelerations, but isn't it logical that they are accelerated by electro-magnetic fields?
It seems reasonable to me that electro-magnetic fields accelerate particles, both in the vicinity of distant supernova remnants and near the core of the Sun.

Perhaps the accelerated particles generate cosmic rays by interacting with other matter at shock front.

With kind regards,

Oliver
http://www.umr.edu/~om

om@umr.edu
2004-Nov-05, 06:39 PM
Originally posted by antoniseb+Nov 5 2004, 03:54 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb @ Nov 5 2004, 03:54 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-om@umr.edu@Nov 5 2004, 03:17 PM
like the giant particle accelerator at the core of the Sun that accelerates H+ ions upward and causes 3 x 10^43 H+ ions to depart the Sun&#39;s surface each year in the solar wind.

If I remember correctly, you are claiming that the H+ ions you are referring to are coming out of a neutron-star-fragment at about 10 to 22 MeV, and converting to protons (that) find their way through 430,000 miles of dense gases. After all that, you say that they come out with the energy we see in the solar wind. [/b][/quote]
No, Anton, neutrons emitted with E = 10-22 MeV are not simply converted to protons that traverse 432,000 miles (the solar radius) of material and emerge as the solar wind.

The H+ ions are accelerated upward in the Sun&#39;s electro-magnetic fields.

This upward flow of H+ ions is the carrier gas that maintains mass separation in the Sun.

Remember, Anton, that is why Marcey and Wright found last summer that Sun-like stars are iron-rich when their electro-magnetic fields shut down.

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Nov-06, 02:59 PM
Originally posted by om@umr.edu@Nov 5 2004, 06:39 PM
neutrons emitted with E = 10-22 MeV are not simply converted to protons that traverse 432,000 miles (the solar radius) of material and emerge as the solar wind.
OK, I was aware that you are including some unknown magnetic process to accelerate Hydrogen ions through the sun [that for some reason, doesn&#39;t accelerate the other types of ions in the Iron Sun]. Still I thought it was amusing to me, but misleading to others that you quoted me, but omitted the part about 22MeV neutrons being unable to escape from the gravitational well of a neutron star.

Guest
2004-Nov-06, 04:44 PM
They are emitted because they penetrate the gravitational well barrier of the neutron star.

antoniseb
2004-Nov-06, 05:00 PM
Originally posted by Guest@Nov 6 2004, 04:44 PM
They are emitted because they penetrate the gravitational well barrier of the neutron star.
That&#39;s amusing. You obviously know no more about quantum barriers than Dr. Manuel.
This barrier is miles wide. Neutrons of this energy would tunnel through this about one per every trillion years.

Duane
2004-Nov-06, 09:54 PM
Remember, Anton, that is why Marcey and Wright found last summer that Sun-like stars are iron-rich when their electro-magnetic fields shut down.


That is incorrect Oliver. What Wright found, as confirmed by Wright himself in an earlier thread in this forum was:


2) Stars which are metal rich (by which we mean they have many times more iron in their atmospheres than the sun does -- a part in 10,000 instead of a part in 100,000) have always been metal rich. Most don&#39;t get that way from nuclear fusion in their cores because that material generally doesn&#39;t get to the surface, so high metal abundance doesn&#39;t really trace age in a useful way. The reason metal-rich stars and subgiants can get confused is that they have similar brightnesses and colors. When I wrote the second paper, I couldn&#39;t tell the difference, so I had to allow for both possibilities.

Now, however, I can tell the difference. Although it might look like metal-rich stars are more inactive, they really aren&#39;t. A couple of effects conspired to make it look that way, but now that I have measurements of the metal abundance in these stars, it is clear that it is age, not metallicity, which keeps their activity levels low. I&#39;m working on a follow-up paper to this effect now.

Which was in this thread: http://www.universetoday.com/forum/index.p...t=ST&f=2&t=4101 (http://www.universetoday.com/forum/index.php?act=ST&f=2&t=4101)

One should be careful to accurately quote an article that one cites in support of a position.

om@umr.edu
2004-Nov-07, 04:56 AM
The UC-Berkeley news report states:

"Star surveys typically find that 10 to 15 percent of all sun-like stars are in an inactive state like the Maunder minimum, which would indicate that the sun spends about 10 percent of its time in this state," Wright said. "But our study shows that the vast majority of stars identified as Maunder minimum stars are well above the main sequence, which means they&#39;re not sun-like at all, but are either evolved stars or stars rich in metals like iron and nickel. To date, we&#39;ve found no star that is unambiguously a Maunder minimum star."

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2004-Nov-07, 07:42 PM
Originally posted by om@umr.edu@Nov 7 2004, 04:56 AM
The UC-Berkeley news report states:

"Star surveys typically find that 10 to 15 percent of all sun-like stars are in an inactive state like the Maunder minimum, which would indicate that the sun spends about 10 percent of its time in this state," Wright said. "But our study shows that the vast majority of stars identified as Maunder minimum stars are well above the main sequence, which means they&#39;re not sun-like at all, but are either evolved stars or stars rich in metals like iron and nickel. To date, we&#39;ve found no star that is unambiguously a Maunder minimum star."

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

With kind regards,

Oliver
http://www.umr.edu/~om
Ok Oliver, so where in that quote does Wright state that

"sun-like stars are iron rich when their electro-magnetic fields shut down" ???

Wright says past surveys showed that about 10 to 15% of sunlike stars surveyed were thought to be in a minimum state similar to the Mander Minimum that Earth experienced, but their new survey found that many of these stars were misidentified. They were either evolved stars or stars that are rich in metals. (ie-not sunlike)

He has now said in this very forum, where I quoted him, that they are actually metal-rich stars, not evolved ones, and they are not actually inactive. (ie-their electro-magnetic fields are not shut down)

One should be careful to accurately state the conclusions of a study one cites to support a premise.

om@umr.edu
2004-Nov-07, 11:55 PM
You are right, Duane.

Wright did not say, "Sun-like stars are iron rich when their electro-magnetic fields shut down".

I said that. I referenced the UC-Berkeley news report on Wright and Marcey&#39;s survey.

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

Darn if I can follow your other quotes, Duane.

You first quoted Wright saying, "I have measurements of the metal abundance in these stars, it is clear that it is age, not metallicity, which keeps their activity levels low.

Now you quote Wright saying "that they are actually metal-rich stars, not evolved ones, and they are not actually inactive."

First it is age, not metallicity. Then metallicity, not age.

Anyway, Duane, the survey found that the surfaces of Sun-like stars were iron-rich when their electro-magnetic fields shut down.

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2004-Nov-08, 06:06 PM
First it is age, not metallicity. Then metallicity, not age.

Read the quote again Oliver, as you appear to misunderstand what he is saying. I would point out that these are his words, not mine, but I will try to paraphrase.


Although it might look like metal-rich stars are more inactive, they really aren&#39;t.

In other words, stars which showed a higher percentage of metalicy in their spectrum at first looked like they were less active. This turned out to be incorrect, for reasons Wright did not state, because:


A couple of effects conspired to make it look that way, but now that I have measurements of the metal abundance in these stars, it is clear that it is age, not metallicity, which keeps their activity levels low.

SO because of additional measurements, he has determined that aged stars are less active, and it is age, not metallicy, that determines how active a star is. An older star is more inactive than a metal-rich star.

Neither of these two types of stars is sunlike, in that the sub-giant older stars are in the process of leaving the main sequence, and the metal rich stars contain 10 times as much metal (1 in 100,000 parts per million for the sun, vrs 1 in 10,000 ppm for these metal-rich stars).

SO again, the method by which you quote Wright&#39;s paper:


You first quoted Wright saying, "I have measurements of the metal abundance in these stars, it is clear that it is age, not metallicity, which keeps their activity levels low.

Now you quote Wright saying "that they are actually metal-rich stars, not evolved ones, and they are not actually inactive."


is misleading, as you have edited the content to convey a message that was not stated, and you have mnisquoted me in that I did not "first say" and then later say, I quoted the entire passage written by Wright in the thread I linked to.

And finally, the survey did not find that

the survey found that the surfaces of Sun-like stars were iron-rich when their electro-magnetic fields shut down. , it found that stars which were thought to be representative of Maunder Minimum stars have been misidentified. It says that right in the article Oliver. I challenge you to show me anything that leads to the conclusion you have made up for the article.

Nothing anywhere in that article says "Marcey and Wright found last summer that Sun-like stars are iron-rich when their electro-magnetic fields shut down." This is a misquote and does not convey the results of their work or survey.

om@umr.edu
2004-Nov-08, 06:25 PM
From my reading of the UC-Berkely news report last summer,

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

I conclude Marcey and Wright found that Sun-like stars are iron-rich when their electro-magnetic fields shut down.

Since that is not the subject of this string, I suggest that UT readers read the report themselves and make their own conclusions.

Of concern here is the possibility that the same mechanism that generates high energy cosmic rays in space might accelerate H+ ions upward from the solar core and maintain mass separation in the Sun.

With kind regards,

Oliver
http://www.umr.edu/~om

Duane
2004-Nov-08, 07:08 PM
I conclude Marcey and Wright found that Sun-like stars are iron-rich when their electro-magnetic fields shut down.


A conclusion not supported by the article, nor the clarification provided by the auther of the study himself.


Since that is not the subject of this string,

Touche&#33; You are right here Oliver&#33;

Regardless, I feel it does no service to anyone to allow a misquoted source to stand uncorrected. Especially when it is stated in a way to convey the impression that the people responsible for the study reached the conclusion stated.

I would point out that Oliver did not say "I conclude that Marcy and Wright found..." he said "Marcy and Wright found that..." As I have said, a misleading statement that does not convey the message of the authors responsible for the study in question.

om@umr.edu
2004-Nov-09, 04:11 AM
As suggested before, UT readers should read the report themselves

http://www.berkeley.edu/news/media/release...1_maunder.shtml (http://www.berkeley.edu/news/media/releases/2004/06/01_maunder.shtml)

and decide if Marcey and Wright found that stars are iron-rich when their electro-magnetic fields shut down.

With kind regards,

Oliver
http://www.umr.edu/~om

pepsi78
2005-Nov-15, 05:37 AM
Hi there i was hopeing if some one can provide me with some answers.
What level of gamma ray does the moon have.
I would prefer in rad rather than mev.
1 rad= 1 rem in gamma radiation.
I am new at this stuff so i understand that mev is the intensity of gamma?
How do i convert mev in to rem or is it even posible.
Any answers would be grate for me.
What i want is to figure out is gamma radiation in rem there on the moon.
Thanks