One supernova type, two different sources

May 7, 2012, Harvard-Smithsonian Center for Astrophysics
The Tycho supernova remnant is the result of a Type Ia supernova explosion. The explosion was observed by Danish astronomer Tycho Brahe in 1572. More than 400 years later, the ejecta from that explosion has expanded to fill a bubble 55 light-years across. In this image, low-energy X-rays (red) show expanding debris from the supernova explosion and high energy X-rays (blue) show the blast wave - a shell of extremely energetic electrons. Credit: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS

The exploding stars known as Type Ia supernovae serve an important role in measuring the universe, and were used to discover the existence of dark energy. They're bright enough to see across large distances, and similar enough to act as a "standard candle" - an object of known luminosity. The 2011 Nobel Prize in Physics was awarded for the discovery of the accelerating universe using Type Ia supernovae. However, an embarrassing fact is that astronomers still don't know what star systems make Type Ia supernovae.

Two very different models explain the possible origin of Type Ia supernovae, and different studies support each model. New evidence shows that both models are correct - some of these supernovae are created one way and some the other.

"Previous studies have produced conflicting results. The conflict disappears if both types of explosion are happening," explained Smithsonian astronomer and Clay Fellow Ryan Foley (Harvard-Smithsonian Center for Astrophysics).

Type Ia supernovae are known to originate from white dwarfs - the dense cores of . White dwarfs are also called degenerate stars because they're supported by quantum degeneracy pressure.

In the single-degenerate model for a supernova, a white dwarf gathers material from a until it reaches a tipping point where a runaway begins and the star explodes. In the double-degenerate model, two merge and explode. Single-degenerate systems should have gas from the companion star around the supernova, while the double-degenerate systems will lack that gas.

"Just like mineral water can be with or without gas, so can supernovae," said Robert Kirshner, Clowes Professor of Astronomy at Harvard University and a co-author on the study.

Foley and his colleagues studied 23 Type Ia supernovae to look for signatures of gas around the supernovae, which should be present only in single-degenerate systems. They found that the more powerful explosions tended to come from "gassy" systems, or systems with outflows of gas. However, only a fraction of supernovae show evidence for outflows. The remainder seem to come from double-degenerate systems.

"There are definitely two kinds of environments - with and without outflows of gas. Both are found around Type Ia supernovae," Foley said.

This finding has important implications for measurements of and the expanding universe. If two different mechanisms are at work in Type Ia supernovae, then the two types must be considered separately when calculating cosmic distances and expansion rates.

"It's like measuring the universe with a mix of yardsticks and meter sticks - you'll get about the same answer, but not quite. To get an accurate answer, you need to separate the yardsticks from the meter sticks," Foley explained.

This study raises an interesting question - if two different mechanisms create , why are they homogeneous enough to serve as standard candles?

"How can supernovae coming from different systems look so similar? I don't have the answer for that," said Foley.

Explore further: Team finds Type Ia supernovae parents

More information: Their work will be published in The Astrophysical Journal and is available online.

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15 comments

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Anda
2.6 / 5 (7) May 07, 2012
So, as suspected, our standard candles ain't so standard.
We 'll see the implications in mesurements of spacetime and dark energy.
Keep waiting as always for new consistent discoveries.
Ventilator
3.4 / 5 (5) May 07, 2012
A2G:

Telescopes do wonders when it comes to optics and extending our range of sight, either for assisted eyesight or use of a camera.

Just to point it out, a radiotelescope basically "sees" as normal, just the radio waves of the electromagnetic spectrum.
yyz
4.8 / 5 (18) May 07, 2012
"But to be clear no one with absolute certainty has ever truly seen a star explode."

Whatever happened to Sanduleak -69° 202, a 12th magnitude blue supergiant star in Dorado? Prior to 1987, a solitary star, with no associated nebulosity, was observed in this part of the sky. Since it went supernova in 1987, only a strangely shaped nebula is visible at this position: http://en.wikiped...tion.gif

Where did the star go and where did the rapidly evolving nebula come from? And from where did the detected neutrino burst originate? Was it mere coincidence it was seen simultaneously with the rise in optical brightness in February of 1987?
Lurker2358
1.4 / 5 (9) May 07, 2012
More than 400 years later, the ejecta from that explosion has expanded to fill a bubble 55 light-years across.


This would require the ejecta to be moving at an average velocity of 0.06875c radially, which is about 13 or 14 times faster than the average velocity of the Crab Pulsar's ejecta.

Given the fact kinetic energy is related to velocity squared, this means the Tycho explosion would need to be 169 to 196 times more energetic than the Crab Pulsar Supernova in order to explain this averaged expansion rate.

Moverover, at this expansion rate, there is no chance in hell of this shell ever contributing to the mass of a star or planet, as the ejecta has a velocity 26 times greater than galactic escape velocity, and about 20 times greater than escape velocity from the surface of the Sun's core.

If this ejecta shell hit a planet, or even another star, it would disintegrate it on impact.
Lurker2358
5 / 5 (2) May 07, 2012
A2g:

At the current size and the average velocity it would have needed to get that big since the explosion, you would be able to SEE the cloud expanding in almost real time.

Every 16 years the radius of the cloud should increase by about 1 light year, which would make the diameter increase by about 1 light year every 8 years. That's how fast it's expanding.

This means, for example, in the Hubble telescopes lifetime, scientists could have actually watched the expansion taking place across enough pixels to establish a relative expansion rate.
Lurker2358
2.3 / 5 (4) May 07, 2012
I need to fix or clarify something in my first post.

It's possible Tycho's left-over core is much less massive than the Crab Pulsar, in which case the expansion rate may not have been slowed by gravity.

Must of the Crab Pulsar's expanding nebula's energy was "cancelled" by gravity during the first second or two, as it exploded out of the insane gravity well of the neutron star core.

Perhaps that explains the enormous discrepancy in velocity.

Maybe Tycho literally disintegrated from the core outwards, leaving no central mass behind to slow down the expanding shell?
Lurker2358
1.4 / 5 (11) May 07, 2012
When I looked this up in Wikipedia, I couldn't help but laugh at the fact that there is a greater than 100% margin of error in the calculation of distance to this object...even though it is supposedly a "standard candle" used for making precise measurements of distance.

The distance to the supernova remnant has been estimated to between 2 and 5 kpc (approx. 6,500 and 16,300 light-years), but recent studies suggest a value closer to 2.5 and 3 kpc (approx. 8,000 and 9,800 light-years).


How sad, and dishonest, of the astronomers.
Shinichi D_
5 / 5 (10) May 07, 2012
When I looked this up in Wikipedia, I couldn't help but laugh at the fact that there is a greater than 100% margin of error in the calculation of distance to this object...even though it is supposedly a "standard candle" used for making precise measurements of distance.

The distance to the supernova remnant has been estimated to between 2 and 5 kpc (approx. 6,500 and 16,300 light-years), but recent studies suggest a value closer to 2.5 and 3 kpc (approx. 8,000 and 9,800 light-years).


How sad, and dishonest, of the astronomers.


Wow. You just refuted yourself. AND IT'S ONLY A STANDARD CANDLE IF YOU CATCH THE LIGHT CURVE OF THE EXPLOSION. It took about 500 years until we understood what it is. The explosion would be the standard candle, not a century old nebula. Distances of this scale are determined with parallax, but the Crab pulsar is on the upper limit of that method.
Shinichi D_
3.7 / 5 (3) May 07, 2012
Tycho whatever.
comendant
4.3 / 5 (12) May 07, 2012
After viewing this file(http://en.wikiped...ion.gif) you still get this type of response...

If you know of such an image then please let me know. I have been looking for years for actual photos of a star exploding. Still have not seen one. It just does not make sense that there was a huge explosion and this structure appears in 1987 and still stays the same today. It should of changed dramatically since then.


Where do these retards come from?
javjav
not rated yet May 07, 2012
I have been looking for years for actual photos of a star exploding. Still have not seen one.

Do you want to see one? Just look trough the window and you will see one, the sun. It is a exploding star, all the light you see come form explosions as per the formula E=mc^2. It is an ongoing star explosion, it is just that it is going slow and it does not disintegrate because gravity forces maintain an equilibrium. Now imagine that suddenly, the amount of light you see grows hundreds of times, solve "m" from the formula and tell me that it is not a exploding star.
encoded
3 / 5 (2) May 07, 2012
look up facts
deny them
report A2G for spam..
(not to say wikipedia is /fact/)
julianpenrod
1 / 5 (6) May 07, 2012
Again, the, frankly, lie that the universe has been discovered to be accelerating. The claim was that galaxies five billion light years away were found to be further away. Frankly, that is exactly what they are saying. That the "acceleration" took place five billion years ago, meaning the galaxies are five billion light years away, but the Type 1a supernovae were so dim they had to be further away than five billion lights years. And, again, the velocity the galaxies were found to be expected, but, which, in fact, they were supposedly exceeding, is that derived from the Hubble Constant. Every galaxy out to five billion light years conformed to the same linear relationship between speed and distance. Suddenly the distant galaxies are moving faster than the nearer galaxies indicate, they are moving faster than galaxies nearer in tinme. Whicht means, if there was an acceleration, it is not happening now!
CardacianNeverid
5 / 5 (4) May 08, 2012
Again, the, frankly, lie that the universe has been discovered to be accelerating -JulianAssRod

I guess Adam Riess, Brian Schmidt and Saul Perlmutter will have to give their Nobel back, thanks to your brilliant insights!
julianpenrod
1 / 5 (1) May 08, 2012
Like there aren't those, even among defenders of "science" who question the veracity of Obama's Nobel Prize. To say nothing of the prizes given for "economics", even though none of them prevented monetary disasters or helped the "rank and file", because "economics" isn't even a legitimate field. But notice CardacianNeverid's "argument". No addressing whatsoever of the actual facets of what I said! Instead raising an arbitrary issue! That's because CardacianNeverid has absolutely nothing to contradict what I say! There is absolutely nothing CardacianNeverid can come up with the counter my statements! And, yet, they went ahead and criticized them still! Criticism although they have nothing they can criticize! A quality so often of those who talk only to hear themselves talk!

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