Order of Kilopi
It's an interesting point, because it illustrates how confusing it can be when people say, "it's about to blow up." What they really mean is probably, "it blew up at a time when it's about to appear to us that it's blown up," but it can be confusing because people aren't necessarily talking about the same thing.Originally Posted by Argos
As above, so below
Established Member
Sorry to be picky, but I just don't see that statement in that article. (Are my eyes deceiving me?)
I am not doubting that you read it. I just want to be sure to have the facts straight that they did in fact link the shrinking to the possibility of a supernova, so I want to be able to read it myself.
...
I just checked--that statement came from the Fox News article, not the Berkeley release and it is not a quote from the researcher. A reporter wrote it.
I know I'm being picky, but I can't believe a conclusion made in a news article until I have proof that it came from the scientists.
If I am overlooking something--please enlighten me!
Order of Kilopi
Nope, it was my error. I was looking at several releases and had Berkeley on the brain, apparently.
Yep, and thanks for the correction. [I've edited the prior posts, too.]I just checked--that statement came from the Fox News article, not the Berkeley release and it is not a quote from the researcher. A reporter wrote it.
That's wise since I doubt anyone in history has ever correctly predicted that a certain star would go supernova. Trinitree may be the first.I know I'm being picky, but I can't believe a conclusion made in a news article until I have proof that it came from the scientists.
Maybe someday core compositions can be determined, which would make the predictions much more... iron clad.
Member
I saw a bright light in the western sky just before sundown. Too small to be the moon, way too bright to be a normal star, and I've never seen any planet, even Venus that bright. I thought weather balloon reflecting the sun- but it was very bright for that, or maybe a star went supernova. I still don't know what it was, but imagine my surprise when I read this article. I'm not saying it was Betelgeuse, but it would be kind of cool if it was.
Order of Kilopi
Betelgeuse will be big news when it goes. It's not something that nobody but you will notice.
As above, so below
Member
I didn't say it was. It was the COINCIDENCE that surprised me.
Order of Kilopi
Sorry, but I took that to mean that you thought it might be.
As above, so below
Order of Kilopi
I believe Betelgeuse is currently in the daytime sky. If it happens about now, we should see something that looks like an extra-bright venus in the daytime sky.
But remember, in astronomy, something that is about to happen can take thousands of years.
Established Member
Well, I strongly assume that that's the integrated magnitude of the whole nebula. The Andromeda Galaxy also is third magnitude integrated, but it's nowhere as visible as typical third magnitude stars.
Blackbody, peaking in the far ultraviolet.
It seems the old Hipparcos distance of 427 ly is in error. Last year, a new measurement combining Hipparcos and VLBI came out, placing it at about 660 ly.
Order of Kilopi
If it does come close to a blackbody distribution, then it will only look slightly blue. You will need the temperature to be about 10 million degrees or so in order to get enough of the blues outweighing the other colors in order to see a blue the would match something like the blue sky overhead. The Sun's core, for instance, would look very blue if we could take a quick look at it and at a greatly reduced level tolerable for our eyes.
Order of Kilopi
Yeah, but I was referring to the fact that the data are inconclusive as to the time frame. It is a variable, and the fluctuations observed don´t seem to point to a drastic regime change. Researchers point out that the increased shhrinkage might be only a result of observation errors. Based on statistics, I´d say it is still there [It would be nice if it did explode in 1400, so we could enjoy a cool show one of these days].
Order of Kilopi
This almost floors me. I was slapped about the board for stating there were significant errors in the Hipparcos distance scales that were broadly defended by the PIs for ~ a decade. 30% is not a big error in astronomical terms, but it is kinda bad for an object this close.
Established Member
Well, I wasn't trying to imply it would be a pure blue, sorry. More like the bluish white seen in early B stars (like Rigel) and O stars.
Though as yet it is not clear what the actual evolution of the X-ray eruption and this "shock breakut" peak are. Possibly, the are one and the same flash which rapidly cools and expands. XRF 060218/SN 2006aj, where the UV flash was observed in detail, had early X-ray emission that was mostly swamped by a non-thermal low-luminosity/energy gamma-ray burst (though a rising thermal component is visible in the second thousand seconds of the explosion), whereas XRO 080109 (O standing for Outburst, as it very probably is not due to the same processes that produce GRBs)/SN 2008D lay behind a significant amount of host galaxy extinction, which strongly damped the UV flash, so there are only sparse data.
@Jerry: Whoops, it was 640, not 660 ly. I got this from Jim Kaler's page, and ADS led my to the paper. Alas, it is NOT on astro-ph (silly, silly - the paper we are actually discussing in this thread also isn't), so I can only give abstracts now:
Hm, the latter doesn't contain a lot of info...
Established Member
Yes, but it is visible when looking carefully. There are other naked eye nebulae - Orion nebula, Praesepe and many other open clusters, Omega Centauri and 47 Tucanae.
Also, Crab is magnitude +8,4 now, 955 years after explosion. What was the total magnitude of Crab in 1154? In 1064?
Betelgeuse is about 10 times closer, thus 5 magnitudes brighter than Crab - about 250 times closer and thus 12 magnitudes brighter than Sanduleak.
How long did the Sanduleak take to brighten from its previous magnitude (12, which means a bit over 100 000 times brighter than Sun) to its peak brightness (+2,9)?
How bright is Sanduleak now (22 years after burst)?
Crab is now about 1000 times brighter than the Sun.
Order of Kilopi
Ok, I was thinking that perhaps you might be refering to more of a spike in the spectrum due to elemental decay of specific elements perhaps, and not a bb distribution.
Are there SEDs of any of these? I would assume non-thermal emissions would not be that close to a blackbody.Though as yet it is not clear what the actual evolution of the X-ray eruption and this "shock breakut" peak are. Possibly, the are one and the same flash which rapidly cools and expands. XRF 060218/SN 2006aj, where the UV flash was observed in detail, had early X-ray emission that was mostly swamped by a non-thermal low-luminosity/energy gamma-ray burst (though a rising thermal component is visible in the second thousand seconds of the explosion), whereas XRO 080109 (O standing for Outburst, as it very probably is not due to the same processes that produce GRBs)/SN 2008D lay behind a significant amount of host galaxy extinction, which strongly damped the UV flash, so there are only sparse data.
Established Member
The light curve decay has flattened at about 20th magnitude. Though I'd expect the SNR to brighten with time, as more and more outflowing matter collides with the old ring around the star (the outer parts of the shock front are already lighting it up).
Nope, definitely no line emission. The only thing in that spectral range which could be really powerful is Lyman alpha and C IV, and I've never heard of those being in emission in supernovae... Though I guess FUV spectra of SNe are very rare, since hardly any are bright enough to yield sufficient S/N. Also, there's no dedicated big FUV mission flying. GALEX and Swift are small, and HST has lost (though hopefully regained now!) STIS...
Can't find a direct SED now... Here's the PDF of the Campana et al. Nature paper (free arXiv-Version) on the SN 2006aj shock break-out. Check out figure 2. The color coding is a bit suxky. The V (visual) band, the longest Swift UVOT measures, is in red. Red is the blue B band... The SN itself (the late bump) is seen to peak in B and V, whereas the FUV flash is brightest in the UVW2 band at 188 nm (yellow points), whereas the SN itself is clearly strongly damped in the UV.
And the UV flash is a thermal component. The top panel, showing X-ray data, shows, in the left side, the total x-ray emission (thick points) and the rising thermal X-ray component (open points).
Established Member
Wow, that´s dim. It seems 100 times dimmer than Crab!
Established Member
Remember that it's just two decades old, not a 1000 years. Still a lot to come.
Established Member
Just curious, and maybe I missed it somewhere, but if the observations before and now were close to correct, and we have seen a 15% decrease in size...
Is this what we would expect with current theory of a supernova collapse rate? Or is there not such a thing as a "standard" rate of collapse?
Order of Kilopi
I was wondering....does the composition of the star affect the schedule for going nova? Curious.
Has a nearby...relatively....star gone nova in modern times...underscientific scrutiny?
Best regards, Dan
Order of Kilopi
No--the last naked-eye supernova was a couple hundred years ago. We are, statistically speaking, overdue. But since stars don't communicate with each other (as far as we know), that doesn't mean one will come sooner any more than flipping a fair coin 9 times and getting heads means the next flip has a greater than 50-50 chance of being tails.
Established Member
No - 22 years.
Order of Kilopi
ok, I looked it up, SN1987A in the large Magellanic cloud was visible to the naked eye.
I was thinking of "Milky Way" I guess--we expect about one every 50 years, but actually somewhat longer because we can't see all of the Milky Way from the inside, but haven't had any since 1604, which Galileo used to argue against the immutability of the celestial sphere.
Order of Kilopi
What percentage of the Milky Way are we now able to detect [visibly] a supernova? [Added: Ok, it's 100% thanks to neutrino detectors.] Prior to this, wasn't it less than half not long ago?
Established Member
Actually (reading the posts above) I'm not even sure that the original authors even inferred anything about a supernova...
Anyway, if a star goes supernova, it's not like you will see it to start shrinking because the core has collapsed under it (unless it's one of those hypothesized failed SNe!). It will just sit there being a merry red supergiant or Wolf-Rayet or LBV, and suddenly it will blast apart.
What seems to be implied is that this shrinking my be due to an earlier stage of core collapse, when the "ash" of the last round of fusion has accumulated into such a heavy core that it starts to contract gravitationally. And the rest of the star's matter is following it. I'm not much into stellar theory, but I also recall that such a gravitational collapse releases extreme amounts of energy, which should actually make the star expand and become brighter. This is exactly what happens when stars move up the asymptotic giant branch during first and second ascension.
Yes and no, from what I know. The hypothesized Population III stars in the very early Universe were made almost entirely of H and He, and had no efficient cooling mechanism, meaning they grew to huge sizes, possibly up to 1000 solar masses. This strongly affects the way the star evolves. The extremely massive ones are actually supposed to collapse quite rapidly into black holes without exploding, while the one of ~ 150 - several 100 M_O will form pair-production supernovae, ultra-powerful explosions which leave no remnant whatsoever, like Type Ia.
Today, though, all young stars are quite "polluted" with metals. Still, late in their life, the metallicity is crucial in driving powerful winds. Very massive stars in our Milky Way mostly blow off their outer shells and become Wol-Rayet stars, while in low-metallicity galaxies (like the SMC) red supergiant are much more common.
I am, in the end, not really sure if the metallicity really has a strong effect on the speed of the fusion sequence in the core (excepting Pop III which had no CNO cycle).
Yes, SN 1987A, see above. Though of course astronomical technology has developed vastly compared to even 22 years ago.
Some months ago, a radio supernova was found near the core of the Milky Way that is 135 years old, the newest supernova we know of, but it was utterly invisible to the naked eye.
There is debate if Cassiopeia A, which exploded in 1680, was visible to the naked eye, if so, it was extincted down to like 4th magnitude, very unspectacular.
Otherwise, you have Kepler's SN in 1604, and Tycho's in 1572.
Before that, there was one in the late 12th century that seems to have reached mag 0, I also recall it was detected from isotope ratios in the Greenland ice sheet.
And of course the two great SNe 1054 (Crab) and 1006 (Lupus).
Before that, according to Wikipedai, three in 185, 386 and 393 (unfair!). There was either a 600 year hole, or a problem with record-keeping then...
Also, we are overdue for a SN from Andromeda, the last known was 1885, and I think if a newer one had occured in a heavily obscured region, it would hve been detected as an X-ray and radio source by now...
Otherwise, the nearest one in recent years was 1993J in M81, that one exceeded tenth magnitude.
Last edited by Don Alexander; 2009-Jun-14 at 07:26 PM. Reason: Did check, added some more SNe.
Honored Member
A similar question came up in Fred Hoyle's novel The Inferno, where the Milky Way briefly becomes a quasar/Seyfert galaxy. The protagonist Cameron shows that since the human eye cannot resolve a point source to an image of less than ten arcseconds or so, some reasonable assumptions about absolute brightness result in an intensity 100 times less than the equivalent Sun or more, too low to harm vision.
If someone could confirm that, I'd appreciate it.
Order of Kilopi
This thread might be of interest.
http://www.bautforum.com/space-astro...-safe-see.html
That's even safer than the limit in Hoyle's story, I think.
Established Member
Arcturus?
Order of Kilopi
yeah, that's right, Aldebaran is the eye of the bull.
Established Member
OK so when the big B does go there is a possibility that it could develop into a black hole. If a black hole did occur, how much of a light show would we really see? The initial explosion would push much of the material away , but I would think that much of it would fall back in because of the gravitational effect. Instead of a huge light show we would only see something the brightness of a nova.
Posting Permissions
Reply With Quote