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|WikiProject Astronomy / Astronomical objects||(Rated C-class, High-importance)|
|WikiProject Physics||(Rated C-class, Mid-importance)|
|A fact from this article was featured on Wikipedia's Main Page in the On this day... section on February 23, 2012.|
I think this article misses photos of actual supernova in its early stages. Unfortunately a few photos I found are rather pathetic (small)... —Preceding unsigned comment added by 188.8.131.52 (talk) 00:25, 28 April 2009 (UTC)
I calculated the distance myself by the light echo method, and arrived at a much smaller value for the distance. Refer http://www.geocities.com/peaceharris/sn1987a
- FYI - "Peace Harris" (Selva Harris) is arguing his position from a young earth creationist (i.e., religious) perspective. His article is not from the professional science literature, nor reflective of it, nor has it had any peer review of any kind from professional astrophysicists. (Greeneto 02:18, 8 June 2006 (UTC))
Changed "planetary nebula" to "supernova remnant". A planetary nebula is a separate astronomical phenomenon from that of a supernova remnant. A PN is formed by the mass lost by a pre-white-dwarf star over a number of episodes, while a SNR is formed by the expanding blast wave from a supernova, e.g. SN 1987a. -- April
Oh, okay! I stand corrected. Is this a recent re-designation? IIRC, I have come across books which use the term "planetary nebula" to describe the Crab, etc. --CYD
No problem! And by the way, thank you for your additions on this subject, one near and dear to my li'l heart. :) To answer your question... it's not a recent designation, per se, but the classification of given objects may be recent. I wouldn't be surprised if the Crab was thought to be a planetary nebula before it was shown to be a supernova remnant. Of course, the term planetary nebula is a horrific misnomer to begin with, as it has about zero to do with planets... hm, maybe I should put in a paragraph on that... :) -- April
The neutrino burst of a supernova takes several seconds. How should it be possible to measure the neutrino speed by to detectors on earth? If the 2 detectors measure neutrinos of different energy range and there is some neutrino mass different from zero than some delay between the corresponding bursts are expected which can be measured if they are larger than the bursts itself. But I don't know if this played a role in this case. --Wolfgangbeyer 08:37, 13 Apr 2004 (UTC)
I removed the part on the "source of regret to astrophysicists": I don't think the energy resolution was that low (except maybe IMB) and the time difference between the clocks of each detector wouldn't have allowed the measurement of the speed of the neutrinos (it is a tiny fraction below that of light). Synchronized timing would help to determine roughly the direction of the supernova by triangulation, and also it would allow coincidence measurement in the framework of SNEWS. --Fleurot 03:03, 6 Oct 2004 (UTC)
From the short antineutrino article it seems that some people think that neutrinos are identical to antineutrinos. With that in mind, how did the neutrino detectors differentiate between neutrinos and antineutrinos during the SN 1987A event? Is it possible that they just detected neutrinos and not any antineutrinos(or vice-versa)? Intangir 20:53, 12 Apr 2005 (UTC)
- We don't expect the same reactions to occur with neutrinos or antineutrinos. For example, IMB and Kamiokande II were filled with light water, so they saw mostly anti-neutrinos via the reaction nubar+p->n+e+. Neutrinos react with light water moslty via electron scattering, which has a much lower cross-section.
- The fact that neutrinos could be their own anti-particles is for the moment a hypothesis which would violate lepton-number conservation. Experiments are on their way. :)
- --Fleurot 20:15, 14 Apr 2005 (UTC)
- Ahhh, ok. So they are theoretically different, we just haven't observed the difference yet...
- I am trying to learn more about the SN 1987A evidence against antimatter-antigravity claims to incorporate that into the exotic matter article(that article sorely needs some counterarguments). Did IMB and Kamiokande II also observe neutrino electron scattering along with antineutrino events during the supernova? I have had a hard time finding a websource which goes into more detail about the antimatter gravity aspect of the SN than Gravitational effects on antimatter, do you know of any other good sources? Intangir 03:39, 16 Apr 2005 (UTC)
- The usual assumption until recently was that neutrinos were one particle, and antineutrinos were another particle, the antiparticle of neutrinos. However, all neutrinos appear to have one "handedness" (quantum spin), and all antineutrinos appear to have one other "handedness". This is difficult (though not necessarily impossible) to explain within the mathematical frameworks of the theories being built around that time. More recently, it's been proposed that they're different manifestations of one type of particle. Until we have a universally accepted and well-tested Grand Unified Theory, we're not going to be sure which is the case. The fact remains that, from an observational point of view, neutrinos and antineutrinos act as if they are different particles (antiparticles of each other), carrying lepton number and participating in normal and reverse beta decay. --Christopher Thomas 18:35, 3 April 2006 (UTC)
Question: How come the neutrinos reached earth three hours before the visible light? Were they emitted several hour earlier?
I'd like to know this too:D. An explanation should be added to the article, or a reference made to this phenomenon with a link to a relevant article/external link on this subject. I have a possible explanation, entirely unfounded as I am not an cosmologist: neutrino speed (nominally at C in a perfect vacuum) is less affected by the density of the interstellar medium than photons, perhaps? Or maybe they are less readily absorbed or reflected by the ISM, resulting in a noticeable surge in neutrino levels several hours before significant photon emissions? The latter would seem to be logical given that neutrino detection is notoriously difficult to achieve. The former probably just indicates I am totally ignorant of the concept that C is absolute for the density of the medium:D --ChrisJMoor 02:36, 18 December 2005 (UTC)
- They are emitted during the core collapse as electrons and protons combine to form neutrons. The light of the explosion is also produced at or after this time. The difference is that neutrinos can escape the collapsing star much more easily than photons, as plasma is mostly transparent to neutrinos, but is opaque to light. As a result, we see a neutrino burst at the time of the explosion, but don't see the glowing shell of expanding stellar material until the shockwave of the explosion reaches the surface of the star. --Christopher Thomas 18:35, 3 April 2006 (UTC)
The discussion of whether the particles detected were normal neutrinos or antineutrinos is a relatively minor point, and is not really relevant to the article. The important part is that the neutrino detections were consistent with a model of the formation of a compact object, and that they were the first detection of an object outside the solar system. Having a third of the neutrino section being about this subject will probably confuse laymen into thinking that it is important, or just confuse them. So, I have removed this extraneous paragraph from the article. — Preceding unsigned comment added by Takkyon (talk • contribs) 04:05, 31 May 2011 (UTC)
If Tycho's supernova is SN 1572,why SN 1987A is SN 1987A?It should be SN 1987.
- No. There were 21 supernovas discovered that took place in the year 1987: http://cfa-www.harvard.edu/iau/lists/Supernovae.html. When more than one supernova is discovered in a year, they are designated with a letter following the year it took place (not the actual year of discovery--a supernova from 1987 has been discovered as recently as 1999 by comparing photos). SN1987A was the first supernova discovered in 1987, but not the only one. On the other hand, Tycho's supernova was the only one discovered in 1572, hence it is simply "SN1572". Jsc1973 (talk) 20:11, 9 February 2008 (UTC)
According to the article: 'Although the actual neutrino count was only 24, it was a significant rise from the previously-observed background level.'
What was the previously-observed background level? It is important to know this in order to understand the relevance of the observed number. Also, the article neglects to make important distinctions between neutrinos and antineutrinos. I know that most of the observations(maybe all) were infact antineutrinos and not neutrinos. If the only significant rise was in the number of antineutrinos observed then this is not significant evidence that gravity affects matter and antimatter similarly. If this is significant evidence for this(which seems likely), it is very important for this article to give some indication as to how significant. --Intangir 00:59, 3 January 2006 (UTC)
- Look up solar neutrino problem. That should give numbers for the background from the sun. Or search for papers on SN1987A neutrino detection, and look at their measurement plots. Background levels also depend on how direction-sensitive the detector is (the Cherenkov light is emitted in a cone in approximately the direction the incident neutrino was travelling). --Christopher Thomas 18:38, 3 April 2006 (UTC)
That link looks crank-ish. Can someone check it out and remove it if appropriate? 184.108.40.206 23:07, 26 November 2006 (UTC)
- Yah. It is a completely crank link. You missed the additional link to the crank site by the 2003/2005 gif animation. I'm going to remove that link as well. --Benjamin Franz 16:35, 30 December 2006 (UTC)
Proofs aside, this paragraph is badly written. Also it makes it seem as speed of light has been decelerating since a lot of time ago. Please check. 01:21, 17 February 2007 (UTC)
- Can you be more specific? It states that the speed of light has not changed, so I don't understand the implication you refer to. Maury 15:13, 17 February 2007 (UTC)
- Reading it over I saw the problem, and fixed it (I hope). Let me know what you think. Maury 15:24, 17 February 2007 (UTC)
Northern Hemisphere or Southern Hemisphere? Both? Thanks,Rich 05:41, 24 February 2007 (UTC)
- Southern hemisphere. Declination −69° 16′ 11.79″ (J2000) 
- This means it would come barely above the horizon around 20N latitude. Tom Ruen 07:57, 24 February 2007 (UTC)
Shouldn't it be the closest since Cassiopeia A? 220.127.116.11 07:20, 10 May 2007 (UTC)
- We did not observe the supernova, of which Cassiopeia A is the remnant. In fact, we have not observed any supernova in the Galaxy since 1604. --18.104.22.168 (talk) 22:24, 14 May 2012 (UTC)
I came across a claim in the October 2004 meeting of the Aukland Astronomical Society (http://www.astronomy.org.nz/aas/Journal/Nov2004/MeetingOct2004Review.asp) that the distance to SN1987a had been revised down to 48.1 kpc. I haven't found any other mention of the "revision" anywhere else on the Internet. Is anyone aware of a revision and what it's based on? —Preceding unsigned comment added by 22.214.171.124 (talk) 22:59, 19 December 2007 (UTC)
Two alternative interpretations only? The most obvious in my opinion is that it is too far away, and by the orientation of the magnetic axis it simply cannot be seen with available instruments. After all: pulsars aren't that luminous, and not all are active in radio. Said: Rursus (☻) 14:03, 17 October 2008 (UTC)
Eureka! It is a type Id supernova (leaving behind a SUPERMASSIVE BLACK DWARF!)
How does anyone know if the light reached Earth on Feb 23 when it was discovered on Feb 24? Should it not read:
- That's a very good question, not stupid at all. The timing comes from the neutrino observatories, two of which were actually proton decay experiments that continuously recorded the events and times very precisely. As opposed to some visible astronomy which may only record a specific day. - Hydroxonium (talk | contribs) 23:25, 1 August 2010 (UTC)
Also, after it was discovered, astronomers went back and looked at photographic plates taken on February 23 and found the supernova, although it had been missed before, since it hadn't yet become very bright. --User:Takkyon —Preceding undated comment added 04:14, 31 May 2011 (UTC).
SN 1987A had a big impact on astronomy and science in general. This article does not metion its impact. Here are a couple of things I remember from that time that should probably be included in the article.
Two of the neutrino observatories, Kamiokande II and IMB, were primarily proton decay experiments at the time. When it was realized that the neutrino events were connected to SN 1987A, it really opened the door to neutrino astronomy. I think the article should mention something about that. - Hydroxonium (talk | contribs) 00:05, 2 August 2010 (UTC)
A few years after this event, Philip Morrison did a series of science lectures titled "Dark matter casts no shadows" where scientists were looking in to the possibility of dark matter being composed of neutrinos. At the time, they believed that the majority of the mass of SN 1987A had been turned into neutrinos during the collapse. I don't think this is a common belief anymore but I'm not certain. I do think something should be mentioned about it though. - Hydroxonium (talk | contribs) 00:05, 2 August 2010 (UTC)
How do you modify/edit references now? The International Astronomical Union have changed their site structure and now reference 2 no longer works. I've added the new address (http://www.cbat.eps.harvard.edu/iauc/04300/04316.html) at the ref tag but it doesn't update the link in the references section. 126.96.36.199 (talk) 23:50, 21 July 2011 (UTC)
Please do not edit this page to say that the neutrinos reached us a few hours before the light because neutrinos travel faster than light. There has not been experimental verification of this. The OPERA experiment at CERN has not been verified, and even if you take their results at face value, the neutrinos would have reached earth FOUR YEARS before the light, not a few hours. (1.59 km, the neutrinos in the OPERA experiment were faster than c by 60 ns per 730 km, giving about 13*10^8 seconds, or 4.1 years). — Preceding unsigned comment added by Jack21222 (talk • contribs) 03:43, 23 September 2011 (UTC)
It would be useful, however, to add a section mentioning the broad use of this supernova's relatively small neutrino-to-light lag as an argument against neutrinos being generally as much faster than light as the OPERA results imply. (Hopefully someone will be able to state this better than I did.) -- Dan Griscom (talk) 02:42, 15 October 2011 (UTC)
Instead of using a (non-SI) unit of energy for the mass of a neutrino, why not use a unit of mass? If energy is that much more accepted in the field (i.e. if it is the jargon du jour) why not throw it in, but in parenthesis? 018 (talk) 18:02, 26 September 2011 (UTC)
- The eV is the customary unit of mass in particle physics for historical and practical reasons, and it's pervasive throughout the field. For what it's worth, there is no convenient SI unit to use - One eV/c^2 is roughly 1.7 * 10^-33 grams, which means even yoctograms (10^-24 gram) are a billion times too large (and there is no SI prefix for going smaller). The nearest common unit of actual mass is the amu (atomic mass unit), which would leave us talking in terms of nano-amus, and that still isn't an SI unit. Tarl.Neustaedter (talk) 18:27, 7 October 2011 (UTC)
The first sentence of the Progenitor section starts "Soon after", and is marked "when?". The answer is 28 February 1987 (four days later) is when Sk -69˚202 was tentatively identified by IUE (International Ultraviolet Explorer), due to far ultraviolet flux decreasing by three orders of magnitude while optical flux was still rising. This is mostly detailed in an Article by G. Sonnenberg, IUE Observatory, Goddard Space Flight Center. This was published (among other places) in Cambridge University Press' "Supernova 1987A in the Large Magellanic Cloud", Proceedings of the fourth George Mason Astrophysics Workshop, 12-14 October 1987.
I'm not quite sure how to go about fitting that into the first section without overwhelming the text. Should I replace "Soon after" with "Four days after", and qualify it as "tentatively"? Tarl.Neustaedter (talk) 05:33, 2 October 2011 (UTC)
- While we're at it, does anyone know why this article lists the progenitor as SK -69˚202a ? All my references list it as simply SK -69˚202, with no hint of multiple components. Was there a report of a second component I missed? Tarl.Neustaedter (talk) 06:19, 2 October 2011 (UTC)
Do people in "the biz" (the IAU) know if there's been any talk or initiative about giving SN1987A a common name, like "Bob's Supernova" or "The SupercalifragilisticexpialidociousNova"? This question is asked in all seriousness. SN1987A is kinda fun to say, but there's nothing there to resonate with the public, is there? SamuelRiv (talk) 17:08, 7 October 2011 (UTC)
- Unlikely. There isn't any convenient handle (like a prominent discoverer or connected historical event) to hang on it. We now have over two decades of literature referring to it as SN1987A, so I'd say it's pretty entrenched. Unlike asteroids, the IAU doesn't have a well-greased mechanism to apply common names to supernovas. About the only remaining chance is if the remnant becomes independently significant by itself, we might hear it described as "the rings nebula supernova" or something like that. Tarl.Neustaedter (talk) 18:39, 7 October 2011 (UTC)
It would be nice if the Hubbell images movie had a pause at the end and a time indicator so that one could see there it was in a beginning to end sense. As is, it can get confusing what happens first and what happens last. It also goes fast enough that if you look at the dates, you can't look at the images and vise versa. 018 (talk) 00:15, 3 December 2011 (UTC)
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We should have a photo of the actual supernova, not just the aftermath. It was visible to the naked eye, so clearly a photo would be significant, and if necessary, use fair use for it. -- 188.8.131.52 (talk) 06:42, 18 April 2013 (UTC)