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I want to add this text to clarify the analysis:
"The Earth would only be in danger if the actual angle of the star's pole relative to the Earth is less than half the opening angle."
Can a subject-matter expert confirm that that statement is obviously accurate to an astronomer, that is, "opening angle" doesn't have some weird and different meaning in astronomy than it does in geometry?
Rolf H Nelson ( talk) 21:49, 20 December 2015 (UTC)
HI Rolf
I don't have a wiki edit account (no time unfortunately) so will reply like this. Note that I work in quite a few different fields, and the WR stars have taken a back seat over recent years so I am not fully up do date with the latest papers.
The most usual definition of "opening angle" is as you have it in the article. It might be easier to just say "Earth would only be in danger if it lies along a line-of-sight within the opening angle of the eventual GRB (that is, the star lies pole-on to Earth to within half the opening angle)."
Even then Earth so far from WR104 as to be at the extreme end of the dangerous range for GRBs (although exactly what this range is depends on still further unknown factors).
You should also mention somewhere that while the pole-on orientation is supported by imaging studies (starting with my work), this interpretation was not backed up by spectroscopy. Studying the radial velocity excursions of certain stellar lines, my colleague Grant Hill at Keck decided that the inclination was more like 30degrees: http://adsabs.harvard.edu/abs/2009AAS...21334103H
Just how to reconcile these conflicting data from two different (but on the surface of it valid) approaches is not yet clear. Or at least, that was the way things stood a couple of years back and I have not looked into it lately.
I also think this statement: "WR 104 is believed to have sufficient spin to create a small possibility of such a hypernova" significantly overstates the case. Really, we don't know. It is very hard to measure rotation velocies for WR stars like these. Statistically, it is hugely unlikely that WR 104 can create a GRB, simply because GRBs are very very rare in metal rich old galaxies like ours. WR104 is also in a binary that has fingerprints of past mass exchange, so this makes it all but impossible to know what might have happened to the stellar spins.
In summary, although I know of no way to categorically rule out the potential for harm from WR104, the odds are extremely long that this is something we need to worry about.
Cheers Peter Tuthill — Preceding unsigned comment added by 129.78.233.210 ( talk) 23:42, 20 December 2015 (UTC)
The comment(s) below were originally left at Talk:WR 104/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Comment(s) | Press [show] to view → |
---|---|
Yes, except for the fact that it may have blown 7,999 years ago, and we wouldnt know it until the gamma ray wavefront hit the Earth. Our failure to have noticed WR104 sooner in no way obligates it to blow at some point in our distant future. Astronomers do not have sufficient instrumentation or understanding, as yet, to characterize the late end-stage behavior of stars, immediately prior to supernova. They've never been looking at one just before it blew, and have nothing to compare WR104 to. Current models can only place WR104 in its last 100,000 years of life. The data obtained on it so far consists of a handful of snapshots, taken weeks apart, at a limited selection of wavelengths. Given that a WR104 GRB represents a potential "Extinction Level Event", its important that more be done to observe and characterize its behavior, as soon as possible.
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Last edited at 20:32, 24 February 2015 (UTC). Substituted at 10:07, 30 April 2016 (UTC)
Whether or not a GRB from WR 104 will pose a danger to life on Earth is an unresolved matter. Some tabloid refs have been playing alot with potential cataclysmic scenarios and a few journalists have decided that WR 104 is unlikely to pose a danger. This "unlikely-ness" is not backed up by the scientific facts we have about WR 104. Here are the reasons:
As long as there are no scientific model calculations to refer to, we can only say that it is "unclear" if the GRB from WR 104 will pose any danger to life on Earth. RhinoMind ( talk) 22:22, 25 July 2016 (UTC)
Some journalists have spoken with mainstream scientists, found out from the scientists that WR 104 is unlikely to pose a danger, and then published magazine or newspaper articles accordingly. These published pop-science articles are suitable for inclusion in Wikipedia per WP:WEIGHT. In addition, blog postings from recognized subject experts are sometimes admissible, per WP:BLOGS. Rolf H Nelson ( talk) 03:10, 27 July 2016 (UTC)
At the moment it is not clear what the scope of this article is. The box is a star-box and only describes the Wolf-Rayet star. For historical reasons WR 104 can mean both the WR star, the binary system or the WR nebula. The text in the article describes the total system, including the nebula. For clarity I suggest that we make a new separate page for the nebula, called the Pinwheel Nebula in the literature, and outfit it with a nebula-box. That is how other nebulae are handled. Then this page can perhaps describe the star system. Preferably with info on when the secondary star was discovered. And hopefully more about the stellar system facts. Radius, more data on the third star, etc.. RhinoMind ( talk) 03:18, 27 July 2016 (UTC)
This article still needs a lot of work, as it if full of speculation and poorly cited material, which seems to be just from one solitary source. Much of the material is repeated several times throughout the document, making the whole text near impossible to read. Some is contradictory too.
The threat to Earth is interesting, but it is both overstated and discussed out of proportion to the actual reality. It read much like personal research and is not written from a necessary WP:NPOV. 70% could easily be culled, IMO.
Worst, the text reads in terms of absolutes when much of the story is conjecture. A supernova is the final event (absolute), but as the star has not gone supernova, the scientific truth is really an expectation (speculative.) I.e. It is likely or predicted to go supernova, but this is not written in stone. (It is also possible for example, that an accretion disk or super-wind could remove much of the outer radiative region into space, downgrading the mass so that it does go supernova or as a core-collapse-SN. The binary companion could change that too.)
Also the editor(s) here should stop the repeated use of 'supernova explosion'. (I have removed nine six of them!) Another is the repeated use of "destructive", which the term supernova already implies. Also these same editor(s) have used the same wrong terminology across multiple Wiki pages. By definition, a supernova is already a 'destructive exploding star', so why repeat it again (and again)? It is a simply a supernova or SN Type (whatever).
Arianewiki1 (
talk)
14:44, 20 January 2017 (UTC)
What happened? When did a WR designation change to be just a single component of a binary or multiple system? Without any references? The Galactic Wolf Rayet Catalogue which assigns WR designations certainly doesn't say that. Lithopsian ( talk) 14:28, 23 January 2017 (UTC)
The lede is misleading when it says
"Some articles decide to reject the catastrophic scenario, while others leave it as an open question."
The articles cited that say it will hit Earth are dated around 2008, or they are based on these older articles. The ones that say it will miss are from 2009 onwards. So the variation in what the articles say is a result of a progression in understanding, not a variation in opinion about what is known. What happened is that spectroscopic observations now strongly suggest that it is tilted at an angle of 30°-40° and so any gamma ray burst can't hit us. See [5] and also [6]
There are other things that make gamma ray bursts unlikely too. They occur preferentially in metal poor dwarf galaxies. Ours is a larger metal rich galaxy. Our galaxy is about as large a galaxy as one can be and still have gamma ray bursts, but also metal rich and it is so far less likely to have them than most galaxies. For details see this paper ( https://arxiv.org/pdf/1303.4809.pdf) which says "We find that only galaxies with present stellar masses below < 10^10 M☉and low metallicity reproduce the observed GRB rate."
See also this list of Gamma Ray Burst Host Galaxies ( http://www.grbhosts.org/). Our galaxy has about 100 billion times the mass of the sun, so would have a figure of 11 in the log (M*/M?) column - at the time of the article they said they were all in dwarf galaxies - and there is currently only one example of a nearby GRB in such a large galaxy, GRB 080207 ( http://www.grbhosts.org/Host.aspx?id=147).
For all these reasons they seem unlikely to occur often in the Milky Way.
For details see Astrobiological Effects of Gamma-Ray Bursts in the Milky Way Galaxy ( https://arxiv.org/pdf/1609.09355.pdf)
Conclusion of that study was
"The results in this work, and others found in the literature imply that GRBs may be uncommon in the Milky Way and may not pose a significant danger to the propensity of planets to host life in the Galaxy."
Robert Walker ( talk) 17:52, 12 February 2018 (UTC)
Decided to "be bold" and just added an extra sentence: "However spectroscopic observations now strongly suggest that it is tilted at an angle of 30°-40° and so any gamma ray burst can't hit us." cited to the Universe Today source. Robert Walker ( talk) 18:01, 12 February 2018 (UTC)
The Effects on earth section lists a unlikely "sequence of events" : 1,2,3, but #3 is very confusingly stated and is not in the Tuthill source used to introduce the list. It seems more a combination of circumstances than a sequence of events ? Points 2 & 3 could be combined (combination of pointing angle and half-open-angle), and maybe we need an earlier event - the actual occurrence of a supernovae that just might cause an observable GRB. (Is it a GRB if we're not in the beam ?). Perhaps we could reorganise the section to : what's the chance of a supernovae (in next N years), what's the probability it generates any GR beam, and what's the probability that we'd be in the GR beam and experience a damaging GRB. ? Also, the Tuthill webpage (undated?) does not give references and does not seem a suitable source for how it's used here. - Rod57 ( talk) 13:23, 23 July 2020 (UTC)
This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||
|
I want to add this text to clarify the analysis:
"The Earth would only be in danger if the actual angle of the star's pole relative to the Earth is less than half the opening angle."
Can a subject-matter expert confirm that that statement is obviously accurate to an astronomer, that is, "opening angle" doesn't have some weird and different meaning in astronomy than it does in geometry?
Rolf H Nelson ( talk) 21:49, 20 December 2015 (UTC)
HI Rolf
I don't have a wiki edit account (no time unfortunately) so will reply like this. Note that I work in quite a few different fields, and the WR stars have taken a back seat over recent years so I am not fully up do date with the latest papers.
The most usual definition of "opening angle" is as you have it in the article. It might be easier to just say "Earth would only be in danger if it lies along a line-of-sight within the opening angle of the eventual GRB (that is, the star lies pole-on to Earth to within half the opening angle)."
Even then Earth so far from WR104 as to be at the extreme end of the dangerous range for GRBs (although exactly what this range is depends on still further unknown factors).
You should also mention somewhere that while the pole-on orientation is supported by imaging studies (starting with my work), this interpretation was not backed up by spectroscopy. Studying the radial velocity excursions of certain stellar lines, my colleague Grant Hill at Keck decided that the inclination was more like 30degrees: http://adsabs.harvard.edu/abs/2009AAS...21334103H
Just how to reconcile these conflicting data from two different (but on the surface of it valid) approaches is not yet clear. Or at least, that was the way things stood a couple of years back and I have not looked into it lately.
I also think this statement: "WR 104 is believed to have sufficient spin to create a small possibility of such a hypernova" significantly overstates the case. Really, we don't know. It is very hard to measure rotation velocies for WR stars like these. Statistically, it is hugely unlikely that WR 104 can create a GRB, simply because GRBs are very very rare in metal rich old galaxies like ours. WR104 is also in a binary that has fingerprints of past mass exchange, so this makes it all but impossible to know what might have happened to the stellar spins.
In summary, although I know of no way to categorically rule out the potential for harm from WR104, the odds are extremely long that this is something we need to worry about.
Cheers Peter Tuthill — Preceding unsigned comment added by 129.78.233.210 ( talk) 23:42, 20 December 2015 (UTC)
The comment(s) below were originally left at Talk:WR 104/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Comment(s) | Press [show] to view → |
---|---|
Yes, except for the fact that it may have blown 7,999 years ago, and we wouldnt know it until the gamma ray wavefront hit the Earth. Our failure to have noticed WR104 sooner in no way obligates it to blow at some point in our distant future. Astronomers do not have sufficient instrumentation or understanding, as yet, to characterize the late end-stage behavior of stars, immediately prior to supernova. They've never been looking at one just before it blew, and have nothing to compare WR104 to. Current models can only place WR104 in its last 100,000 years of life. The data obtained on it so far consists of a handful of snapshots, taken weeks apart, at a limited selection of wavelengths. Given that a WR104 GRB represents a potential "Extinction Level Event", its important that more be done to observe and characterize its behavior, as soon as possible.
|
Last edited at 20:32, 24 February 2015 (UTC). Substituted at 10:07, 30 April 2016 (UTC)
Whether or not a GRB from WR 104 will pose a danger to life on Earth is an unresolved matter. Some tabloid refs have been playing alot with potential cataclysmic scenarios and a few journalists have decided that WR 104 is unlikely to pose a danger. This "unlikely-ness" is not backed up by the scientific facts we have about WR 104. Here are the reasons:
As long as there are no scientific model calculations to refer to, we can only say that it is "unclear" if the GRB from WR 104 will pose any danger to life on Earth. RhinoMind ( talk) 22:22, 25 July 2016 (UTC)
Some journalists have spoken with mainstream scientists, found out from the scientists that WR 104 is unlikely to pose a danger, and then published magazine or newspaper articles accordingly. These published pop-science articles are suitable for inclusion in Wikipedia per WP:WEIGHT. In addition, blog postings from recognized subject experts are sometimes admissible, per WP:BLOGS. Rolf H Nelson ( talk) 03:10, 27 July 2016 (UTC)
At the moment it is not clear what the scope of this article is. The box is a star-box and only describes the Wolf-Rayet star. For historical reasons WR 104 can mean both the WR star, the binary system or the WR nebula. The text in the article describes the total system, including the nebula. For clarity I suggest that we make a new separate page for the nebula, called the Pinwheel Nebula in the literature, and outfit it with a nebula-box. That is how other nebulae are handled. Then this page can perhaps describe the star system. Preferably with info on when the secondary star was discovered. And hopefully more about the stellar system facts. Radius, more data on the third star, etc.. RhinoMind ( talk) 03:18, 27 July 2016 (UTC)
This article still needs a lot of work, as it if full of speculation and poorly cited material, which seems to be just from one solitary source. Much of the material is repeated several times throughout the document, making the whole text near impossible to read. Some is contradictory too.
The threat to Earth is interesting, but it is both overstated and discussed out of proportion to the actual reality. It read much like personal research and is not written from a necessary WP:NPOV. 70% could easily be culled, IMO.
Worst, the text reads in terms of absolutes when much of the story is conjecture. A supernova is the final event (absolute), but as the star has not gone supernova, the scientific truth is really an expectation (speculative.) I.e. It is likely or predicted to go supernova, but this is not written in stone. (It is also possible for example, that an accretion disk or super-wind could remove much of the outer radiative region into space, downgrading the mass so that it does go supernova or as a core-collapse-SN. The binary companion could change that too.)
Also the editor(s) here should stop the repeated use of 'supernova explosion'. (I have removed nine six of them!) Another is the repeated use of "destructive", which the term supernova already implies. Also these same editor(s) have used the same wrong terminology across multiple Wiki pages. By definition, a supernova is already a 'destructive exploding star', so why repeat it again (and again)? It is a simply a supernova or SN Type (whatever).
Arianewiki1 (
talk)
14:44, 20 January 2017 (UTC)
What happened? When did a WR designation change to be just a single component of a binary or multiple system? Without any references? The Galactic Wolf Rayet Catalogue which assigns WR designations certainly doesn't say that. Lithopsian ( talk) 14:28, 23 January 2017 (UTC)
The lede is misleading when it says
"Some articles decide to reject the catastrophic scenario, while others leave it as an open question."
The articles cited that say it will hit Earth are dated around 2008, or they are based on these older articles. The ones that say it will miss are from 2009 onwards. So the variation in what the articles say is a result of a progression in understanding, not a variation in opinion about what is known. What happened is that spectroscopic observations now strongly suggest that it is tilted at an angle of 30°-40° and so any gamma ray burst can't hit us. See [5] and also [6]
There are other things that make gamma ray bursts unlikely too. They occur preferentially in metal poor dwarf galaxies. Ours is a larger metal rich galaxy. Our galaxy is about as large a galaxy as one can be and still have gamma ray bursts, but also metal rich and it is so far less likely to have them than most galaxies. For details see this paper ( https://arxiv.org/pdf/1303.4809.pdf) which says "We find that only galaxies with present stellar masses below < 10^10 M☉and low metallicity reproduce the observed GRB rate."
See also this list of Gamma Ray Burst Host Galaxies ( http://www.grbhosts.org/). Our galaxy has about 100 billion times the mass of the sun, so would have a figure of 11 in the log (M*/M?) column - at the time of the article they said they were all in dwarf galaxies - and there is currently only one example of a nearby GRB in such a large galaxy, GRB 080207 ( http://www.grbhosts.org/Host.aspx?id=147).
For all these reasons they seem unlikely to occur often in the Milky Way.
For details see Astrobiological Effects of Gamma-Ray Bursts in the Milky Way Galaxy ( https://arxiv.org/pdf/1609.09355.pdf)
Conclusion of that study was
"The results in this work, and others found in the literature imply that GRBs may be uncommon in the Milky Way and may not pose a significant danger to the propensity of planets to host life in the Galaxy."
Robert Walker ( talk) 17:52, 12 February 2018 (UTC)
Decided to "be bold" and just added an extra sentence: "However spectroscopic observations now strongly suggest that it is tilted at an angle of 30°-40° and so any gamma ray burst can't hit us." cited to the Universe Today source. Robert Walker ( talk) 18:01, 12 February 2018 (UTC)
The Effects on earth section lists a unlikely "sequence of events" : 1,2,3, but #3 is very confusingly stated and is not in the Tuthill source used to introduce the list. It seems more a combination of circumstances than a sequence of events ? Points 2 & 3 could be combined (combination of pointing angle and half-open-angle), and maybe we need an earlier event - the actual occurrence of a supernovae that just might cause an observable GRB. (Is it a GRB if we're not in the beam ?). Perhaps we could reorganise the section to : what's the chance of a supernovae (in next N years), what's the probability it generates any GR beam, and what's the probability that we'd be in the GR beam and experience a damaging GRB. ? Also, the Tuthill webpage (undated?) does not give references and does not seem a suitable source for how it's used here. - Rod57 ( talk) 13:23, 23 July 2020 (UTC)