Jan 11 2008
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AAS #18: Two supernovae, no waiting
This will be my last post from the actual physical location of the American Astronomical Society meeting; I’ve preloaded this entry to go up when I’ll be on a plane winging it back to Boulder. I’ll have some wrap-up stuff later (oh, just you wait) but since I’m heading back, I want to leave you with a really cool supernova remnant image. But I can’t… so instead I’ll leave you with two!
This object looks like a single nebula with two lobes, but new studies show that it’s actually two separate object next to each other in the sky! This Gemini telescope image is of DEM L316, and it was always assumed to be what’s called a bipolar nebula, a single object blowing bubbles of gas in opposite directions. However, it’s now understood to be the expanding gas (called the remnant) from two separate exploding stars. The two stars blew up in the Large Magellanic Cloud, a small galaxy orbiting our Milky Way galaxy.
X-ray observations support the idea that these are two distinct objects: the X-ray emission indicates the chemical composition (the relative amount of iron, oxygen, and so on) are different in the two objects. In fact, it looks like these were two different types of supernovae altogether: the smaller lobe on the left is probably from the detonation of a white dwarf star, while the bigger one on the right is from the explosion of a star more like the Sun (though with substantially more mass — the Sun can’t go supernova). While both explosions probably happened around the same time (give or take a few tens of thousands of years), the stars were much different ages when they blew: the white dwarf was probably billions of years old, while the massive star was only a few million years old. The two stars were almost certainly totally unrelated to each other.
But through a cosmic coincidence, they both chose the same epoch of the Universe to light up the skies around them. And from our perspective they form a pretty, if somewhat lopsided, example of just how pretty death and destruction on an epic scale can be.
I don’t know why, exactly, but it looks to me like two separate events to me. But, what are all those little white spots? Could they be stars? At my house I can see only six or eight of those, unless, I use my 8″ Newtonian. Then I can see 10 or 12 little white spots. I love light pollution.
Seriously, that is a beautiful picture!
Wow! This latest bunch of postings is really awe-inspiring.
Thanks!
Back read-only mode.
Cool! Any chance that the explosion of one contributed to the initiation of the explosion of the other?
I wonder how the star on the right was more like the sun since it was much larger and had a much shorter life. I’d think the star on the left would be more like the sun. Just wondering.
Just had to drop feedback on this one, ’cause this is my Favorate Remnant(s) Evar.
Phil - small correction; in Ye Olde Days, it was thought to have been one supernova remnant that exploded into a bipolar nebula and thus took on the nebular shape. It was known to be a remnant of some sort since the 70’s.
Back in The Day, when our research group was looking at this region, we got the idea in our heads that these were two remnants, and what’s more, they were actually interacting with each other. (Suggested paper title: Supernova Remnants Collide! World to End?) We built up a pretty good case for it, too, and published it. Full of enthusiasm, we proposed to the Chandra X-ray observatory to study it in the X-ray. Well…
“The great tragedy of Science - the slaying of a beautiful hypothesis by an ugly fact.” — Thomas Henry Huxley.
Thing is, in the X-ray, you can use the spectrum to get a very good idea what elements are present, and thus, barring significant contamination, what elements were produced when the supernova went blammo. Phil covered the two types of supernovae above - well, white-dwarf supernovae are thought to produce a lot of iron. One of those shells (the smaller one) shows a lot of spectral signatures of iron, while the big ‘un shows very little.
This makes me sad. Massive stars live fast, die young; low-mass stars live long and dwindle to white dwarfs. Sometimes, the white dwarfs, still later, borrow mass from a companion star, get up to higher mass, and then the aforementioned blammo. So you could easily imagine two massive stars that were born together, lived nearby, and blew up in the same area of space at nearly the same time. But it strains credulity to think that one white dwarf just happened to collect enough mass to blow its top - at almost the exact same time (astronomically speaking) as a massive star went critical. That’s what would be required for the two remnants to be colliding now. So we had to write another paper saying that the hypothesis of the first paper had now been rendered highly improbable. Pfui. But at least we could show that these were pretty firmly two separate remnants, due to the one being iron-rich and the other iron-poor.
http://chandra.harvard.edu/photo/2005/d316/
It would still have been neater if they had been colliding. Darn it.
So as for one helping to “trigger” the other - it’s hard to see how, since the odds of them actually being close in space seem now to be pretty small. Most likely they just happened to line up along our line of sight in that direction. Either that, or the FSM put them that way to frustrate astronomers, which is my current hypothesis.
[…] most of this week, and has had a wonderful series of posts about the meeting. He just posted the final one this morning (though there will undoubtedly be follow-up posts once he is home as sorted things […]
Thanks great image … & awe-inspiring science.
How true to life are the colours here? Is it pretty much as you’d see with the unaided eye if it were colour sensitive enough and close enough or is it more near infra-red or enhanced?
# lagomorph on 11 Jan 2008 at 6:08 pm wrote :
“I wonder how the star on the right was more like the sun since it was much larger and had a much shorter life. I’d think the star on the left would be more like the sun. Just wondering.”
Yeah, I’m with you on that one Iagomorph. A red or perhaps blue supergiant is hardly what I’d call a sunlike star …
The type II (right hand remnant causing) supernova would have started life with at least 10 or so solar masses and been a massive blue-hot type O or early B star. It would have lived only ten million or so years (I think -off cranium top) before using upits core hydrogen supplyand shiftinmg toburn helium and other elements transforming and swelling up in the process into a redsupergiant shifting between supergiant types ( blue-white-yellow-orange-red & perhaps back again or even if massive enough just hypergaint blue star, Luminous Blue variable eg. Eta Carinae -> Supernova!) before detonating as a supernova.
The type Ia (left-hand remnnant causing) supernova star would ahve started as astar under about 8 solar masses, quiteproabbnaly sun-like or onlyslightly brighetr and moremassive, lived from 300 million to ten or twelve billion years before running out of core hydrogen, shifting tohelium burningand then swelling into a red giant (NOT supergiant) formed a planetary nebula, left behind a massicve white dwraf, accreted material froma companion star , perhaps expoldedas arecurrent nova befroe going supernova.
To me, the latter could have been a sun-like star, the former definitely not. Personally, I’d limit the term ‘Sun-like’ to stars from mid type F to mid type K …
Type sA I’d call Sirian as their like Sirius, type s)O &B I’d call high mass or perhaps Rigellian … ? Types M (& some late K tyep) I’d describe as low -mass or red dwarfs .. But maybe that’s just me?
Actually Rigel is a supergiant star which is somewhat different to normal Btype dwarfs.
So I guess make that Achernarese after Achernar, (Alpha Eridani) the brightest normal blue dwarf star, a B5 star located 145 light years away for B type stars. (Achernar is sometimes described as a giant but pretty sure its actually still on the main-sequence & wrongly listed as 85 ly off in older sources.)
High mass for classes O & B (O stars ‘Naoisian’ after Naods the brightest example?)
Siran and Procyonese for types A and F dwarfs respectively then Sun-like applying for stars from about spectral type F6 (Procyon at type F5 is already seven times brighter and twice as large diameter-wise than our Sun) through to about K5 and fianlly redwrafs for stars fainetr than that …
Maybe?
Sorry, Naos not “Naods” is the proper name of the brightest spectral class O star.
My typo in the above …
I think Procyon is a subgiant. I seem to remember it getting the luminosity class “IV-V” in the old Gliese catalogue. They may have retyped it since then, though. What does SIMBAD say?
StevoR-
It’s all in the visible spectrum, but it’s not true color. The Gemini website says that the red = H-alpha, blue = OIII, and green = SII. H-alpha really is a deep red, but SII is actually an even darker red. OIII is a pretty blueish-green. So, the blue needs to be greener, and all the yellow parts are actually dark red. The only parts of this you might be able to see, even if you were close, are the OIII sections shown in blue. (The color would probably be washed out all the way to gray though.) Your eye is not at all sensitive to red light, especially when it’s faint. Supernova remnants are especially faint, so the red parts are pretty much invisible. (If you were to get closer, it would appear larger and more spread out, so that wouldn’t help.) There are other emission lines in this nebula than what are shown here, of course, but the rest are probably fainter and even less helpful to you in the unaided-eye department.
Many thanks for that answer, Dan Gerhards, its much appreciated.
Barton Paul Levenson : My understanding is Procyon A (Procyon B is the white dwarf comapnion to the “Little Dogstar” of course!) is right on the edge of being a main-sequence-dwarf / subgiant star; just beginning to evolve off fusing hydrogen and into “burning” helium at its core. There does seem to be some doubt as to whether Procyon A falls into luminosity class V (main-sequence dwarf) or IV (subgiant) with some astronomers & groups listing it as one & others as the other …
Not sure about SINBAD … or how they / it (?) classifies Procyon A …
I know Ken Croswell has one article online :
http://kencroswell.com/AgeOfProcyon.html
(hope the link works!)
discussing Procyon’s age - he says its 1.7 billion years old, 1/3rd the Sun’s age & is, quote:
“… evolving from the main sequence to the subgiant stage.”
Unquote.
James B. kaler also describes Procyon online via :
http://www.astro.uiuc.edu/~kaler/sow/procyon.html
(again, hope the link works) where he writes :
” … (true to the stars’ subgiant status) that it is about to give up core hydrogen fusion as it prepares to become a much cooler and brighter subgiant (the stars age around three billion years).”
From site linked above; brackets original, any typos mine.
So a bit of a disparity and unclarity there regarding the age figure but … still hope that helps!
A little more on Naos too for the curious :
Naos has the Bayer or Greek letter designation of Zeta Puppis & is an O type supergiant; the brightest star in Puppis - roughly in a line from the tail stars of Canis Major shines at 2.3 mag in our skies though actually very much more luminous - esp. at UV wavelengths!
So O type dwarfs are .. well extremely, *extremely*, rare. Only other ones I’m really aware of, Alnitak or Zeta Orionis & Mintaka or Delta Orionis although both these “Belt stars “of Orion -bottom of the “Saucepan” asterism for us southerners - are supergiants and, at O9.5 Ia class, only barely fall into that spectral type as the coolest of O class stars.
Incidentally, the other “Belt star” - the middle one Alnilam or Epsilon Ori is a B0 supergiant so nearly the same class .. Then we have Gamma-2 Velorum or Regor is also an O type star -an O7 giant & is accompanied by a Wolf-Rayet star although pretty sure its southern circumpolar. Northern circumpolar though, I think, pretty faint is Alpha Camelopardalis another O type star not sure if its a dwarf or giant but think iRecallseeing its got a “bow-shock” nebula around it.
Finally we have perhaps the brightest star in our Galaxy HD 93129A an O3 type supergiant located in the Carinae nebula’s Trumpler 14 starcluster. HD 93129 A is visually mag. 7.3 but has a total bolometric (all radiation wavelengths included.) absolute Magnitude (real brightness) of - 11.2! This means if you were 30 odd light years away from this star it would be about as bright as the full Moon!
Pretty sure Kaler’s star-of-the-week website - you can access that via the Procyon link I posted before - has entries on those stars if y’all wish to know more …
Sources : Kaler, James B., ‘The 100 GreatestStars’, Copernicus Books, 2002.
& ‘Collins Guide to Stars & Planets’, Ridpath, Ian & Tirion, Wil, Collins, 1988.
Stevo — thank you for the data on Procyon.
-BPL