This news article summary source being of course from the UT homepage.

OK, now...lemme see if I can truly, really get this weird thing straight: no matter how distant, all Type 1A Supernovae are the same apparent brightness? ...Or Actual Brightness?

corrected version
Sometimes you surprise me Starlab. There are quite a few topics that you know a fair amount about for someone your age, but every once in a while there's a giant gaping hole in your knowledge-base. In this case we can fix that easily enough.

A type 1a supernova is presumed to be a white dwarf [note, in the first edit of this message I said neutron star, thanks to JohnL for spotting this, see below] near the critical mass to collapse, and this white dwarf is accreting matter from an evolved close companion. When this thing collapses, it explodes with just about exactly the same energy every time. The only things that vary are:
- our angle of view with respect to the axis of rotation of the white dwarf [and presumably the orbital plane of the companion]
- the size and depth of the cloud blown off previously by the companion

So, the type 1a supernova can be used to tell how far away something is fairly precisely. As we learn more about the variations caused by the items mentioned above, and the precise details of the light curves at various wavelengths, and get better equipment like the stuff mentioned in this article, we'll be able to get absolute positions [within a few percent] to hundreds of distant galaxies per year.

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And, Antoniseb, its even rarer for you to be wrong. In this case, though, you are.

A Type Ia Supernova is when a white dwarf, the mostly carbon and oxygen core of a dead star (the end of the line for our Sun as well) acretes matter from a binary star companion. When the white dwarf star acretes enough matter that its total mass goes over the 1.4 solar mass limit for these objects it explodes. The light signature of these explosions is always the same, and, based on the brightness measured compared to the actual brightness of these objects, you can determine the distance to the explosion. This is why they're being called standard candles. If the theory is correct they can be used to accurately measure the distance to objects throughout the entire universe.

I did a quick Google search and can only find the white dwarf explanation of Type Ia's, with no neutron stars explanations found in the search...

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Doh!

Yes you are right, and I knew better, but spaced it. Thanks for the correction. I modified my original post in a way that makes your correction still a meaningful part of the thread, but such that people who read it won't be misled.

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To continue this thread a bit. What is the closest white dwarf in a binary system that could end up a Type Ia supernova?

I know Sirius B is the white dwarf that orbits the bright star Sirius A, but the separation between the two is too great for the acretion of Sirius A's matter onto Sirius B. Are there any others in our neighborhood?

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...and we'll be saying a big hello to all intelligent life forms everywhere; and to everyone else out there, the secret is to bang the rocks together, guys...

JohnL there's isn't a really good answer to that. It was thought that a white dwarf could be swallowed by a partner that entered it's red giant stage, and then they found a couple that showed spectroscopic evidence of having orbited inside the atmosphere of the red giant before it went supernova (the red giant).

I seem to recall an article about an odd star a few months ago, where they decided that it was a star that had another star or large planet orbiting in it's atmosphere as they were measuring it.

So it seems that a white dwarf can be very close to a companion star. Once the companion begins dropping mass onto the white dwarf and the Chandra limit is exceeded, boom.

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You're looking for a type 1a progenitor system? There are none in our neighborhood that are in the accretion phase, and since we're just passing through this neighborhood, it might make sense to look ahead to where we're going for such a system.

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Does our "neighborhood" - in other words, the surrounding stars - move with us as we orbit the galactic center, or are we just passing through? Because if it's the latter, our solar system may well have passed through supernova clouds in the past, or close to stars themselves about to supernova, and could do so sometime in the near or far future.

There was a thread about this in Other Stories that started with a link to a paper on this subject.
Sun's Path Through The Galaxy, descending in an elliptical orbit
Take a look at the paper, it's an easy read.

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That's good news! How much too big is the separation? several times the critical distance? One less dagger the universe has aimed at our heart, for now.

Arcturus orbits the galaxy at a relatively large angle to the plane of the disk (I read somewhere long ago). This seems plausible however true it may be. It also seems plausible that other stars have similar orbits however transient this apparent observation may be. My guess is that most of our stellar system neighbors orbit essentially "in synch" with us except for gravitational flirtations with one another and the random mutual occurrences of the "apgalactic" points and elliptical eccentricities of the galactic orbits of each. While a few interlopers like Arcturus mess things up now and then. These variations, although not likely to occur in regular cycles, can make our future extremely difficult to predict. If the galactic arms are a phase phenomenon with an appreciablly different velocity (especially an opposite one) from our neighborhood, we could pass in and out of the different arms with uncertain impact.

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Sirius B orbits Sirius A at about the distance that Uranus orbits the sun. This is ten to twenty times the critical distance. BTW, note that Sirius A is about 2 times the mass of the sun. Sirius B must have been more than that as it evolved and blew up first. What is left of Sirius B is about one solar mass.

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Thanks antoniseb.

Sirius B must have salted the solar system with a lot of the higher mass elements since it's relatively near and perhaps only a few 100 millions of years ago. Is there any evidence of the cloud B must have generated? Type II, I presume. Perhaps B is a likely suspect for one of the mass extinctions of earth life.

In some descriptions of type II supernovae it is stated that fusion beyond iron does not happen. It seems more likely that it happens but the energy consumed reduces the temperature thereby allowing the collapse which fuses even more of the higher elements just prior to the explosion.

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

Sirius is unlikely to have been very near us when it became a white dwarf; the relative motions of the stars are slow, except for some like 61 Cygni amd Barnard's star; but over hundreds of millions of years, our Sun would find itself surrounded by an entirely different stellar neighborhood.

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Sirius B is a white dwarf, which is not a supernova remnant. Sirius B did most likely blow off clouds of material [largely hydrogen, helium, and some carbon] probably creating a planetary nebula. As eburacum45 pointed out, that nebula was made a very long time ago, and probably not anywhere near where the sun was at the time.

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Does the current proper motion of Sirius indicate that it is not a long term fellow traveller with the solar system. It seems reasonable to assume that stellar systems that are "close" neighbors will have very nearly the same periods of revolution about the center of the MW. However, differences in elliptical eccentricities and the lack of coincidences of "apgalactic" points of their orbits could cause appreciable galactic radial differences in distance. Then there's gravitational slingshoting adding random variations in relative locations.

Thanks for reminding me that B could not have been a supernova of any type. Earlier values (5 or 10 years ago) for the mass of Sirius (not sure whether A & B were both included) were near 9 solar masses, when did the estimate get reduced to 2 solar masses? Do current theories of stellar physics allow for binaries to exchange masses in an oscillatory fashion? One can easily imagine that when B went nova that A acquired most of the expanded shell of gas from B. If so A was probably the smaller one of the pair before the B nova event.

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
Whether there is a limit to the magnitude of a modulation of chaos below which order remains invariant? Or, is order but a fiction invented by perspectives applied over finite, however large, time intervals?

A could have gotten some extra mass [but not much when B was blowing off material near the end of its life, but the distance between the two would make any sort of back and forth dumping unlikely. The orbit varies from 8 to 35 AU.

Note that the mass of A is thought to be about 2.0 solar masses [RECONS], and its luminosity is about 26 times the solar luminosity. The current age estimate for Sirius A is 300 million years.

Proper motion - Sirius is moving about 1.4 arcseconds per year, so in 36,000 years, it will appear to have moved about 10 degrees across the sky. It is not yet at it's closest approach to the sun.

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