Type Ia supernovae stem from the explosion of white dwarfs coupled with twin stars

Type Ia supernovae stem from the explosion of white dwarfs coupled with twin stars: A new model postulating the fusion of two white dwarfs is now challenging the predominant one, consisting of a white dwarf and a normal star. The new scenario does not imply the existence of a maximum mass limit and will not, therefore, necessarily produce explosions of similar luminosity...

"If these results were to gain general acceptance, the cosmological consequences would be weighty, because the use of type Ia supernovae to measure distances would come into question," the researcher concludes.

Standard-Candle Supernovae are Still Standard, but Why? � Berkeley Lab News Center

Standard-Candle Supernovae are Still Standard, but Why? � Berkeley Lab News Center: ... a new analysis of normal Type Ia supernovae... shows that in fact they have a range of masses. Most are near or slightly below the Chandrasekhar mass, and about one percent somehow manage to exceed it...

A supernova eruption thoroughly trashes its white dwarf progenitor, so the most practical way to tell how much stuff was in the progenitor is by spectrographically “weighing” the leftover debris, the ejected mass...

The SNfactory team compared masses and other factors with light curves: the shape of the graph, whether narrow or wide, that maps how swiftly a supernova achieves its brightest point, how bright it is, and how hastily or languorously it fades away. The typical method of “standardizing” Type Ia supernovae is to compare their light curves and spectra....

“The conventional wisdom holds that the light curve width is determined primarily or exclusively by the nickel-56 mass,” Scalzo says, “whereas our results show that there must also be a deep connection with the ejected mass, or between the ejected mass and the amount of nickel-56 created in a particular supernova.”

Astronomers Discover New Kind of Supernova | Carnegie Institution for Science

Astronomers Discover New Kind of Supernova | Carnegie Institution for Science: This new type, Iax, is fainter and less energetic than Type Ia. Although both types come from exploding white dwarfs, Type Iax supernovas may not completely destroy the white dwarf.
“A Type Iax supernova is essentially a mini supernova..."

The team calculates that Type Iax supernovae are about a third as common as Type Ia supernovae. The reason so few have been detected is that the faintest are only one-hundredth as bright as a Type Ia supernova.

Finding the star in this supernova could unlock the secrets of the universe

Finding the star in this supernova could unlock the secrets of the universe: At the center of this supernova remnant should be the companion star to the star that blew up. Identifying this star is important for understanding just how Type Ia supernova detonate, which in turn could lead to a better understanding of why the brightness of such explosions are so predictable, which in turn is key to calibrating the entire nature of our universe. The trouble is that even a careful inspection of the center of SNR 0509-67.5 has not found any star at all.

Universe's 'standard candles' are white dwarf mergers

Universe's 'standard candles' are white dwarf mergers: ...the new study by American, Israeli and Japanese astronomers using Subaru and Keck telescopes in Hawaii instead suggests that many, if not most, of the Type Ia supernovae result when two white dwarf stars merge and annihilate in a thermonuclear explosion.

Though the two-faced nature of Type Ia supernovae still allows them to be used as calibratable candles to measure cosmic distance, Filippenko said, it might affect attempts to “quantify in detail the history of the expansion rate of the universe. The subtle differences between single- and double-degenerate models could introduce a systematic error that we’ll need to account for.”

Astronomers Discover New Standard Candle - Technology Review

Astronomers Discover New Standard Candle - Technology Review: Active galactic nuclei are galaxies with a central supermassive black hole that emits intense radiation. When this radiation hits nearby gas clouds, it ionises them causing them to emit a characteristic light of their own.

In recent years, astronomers have found that they can see both the emissions from the supermassive black hole as well as the emissions from the gas clouds. These are obviously related but the time it takes for radiation to reach the cloud means that changes here lag those in the supermassive black hole.

This delay, which can be measured with a technique called reverberation mapping, is then clear measure of the radius of the cloud.

But since the flux of the radiation from the black hole drops as an inverse square law, the brightness of these clouds also depends on their radius.

So a good measure of their radius also gives an indication of their intrinsic brightness.

Now Watson and co have used this technique to measure the distance to 38 active galactic nuclei at distances of up to z=4. That's significantly further than is possible with type 1a supernova, whose distance cannot be accurately measured beyond z=1.7.

More Evidence for a Preferred Direction in Spacetime - Technology Review

More Evidence for a Preferred Direction in Spacetime - Technology Review: They point to evidence from the study of Type 1 supernovas, which appear to be accelerating away from us, indicating the Universe is not just expanding but accelerating away from us. The curious thing is that this acceleration is not uniform in all directions. Instead, the universe seems to be expanding faster in some directions than others...
Today, they confirm that the preferred axis is real. According to their calculations, the direction of greatest acceleration is in the constellation of Vulpecula in the Northern hemisphere. That's consistent with other analyses and also with other evidence such as other data showing a preferred axis in the cosmic microwave background.

[1104.3654] Cosmological extrapolation of MOND

[1104.3654] Cosmological extrapolation of MOND: "Regime of MOND, which is used in astronomy to describe the gravitating systems of island type without the need to postulate the existence of a hypothetical dark matter, is generalized to the case of homogeneous distribution of usual matter by introducing a linear dependence of the critical acceleration on the size of region under consideration. We show that such the extrapolation of MOND in cosmology is consistent with both the observed dependence of brightness on the redshift for type Ia supernovae and the parameters of large-scale structure of Universe in the evolution, that is determined by the presence of a cosmological constant, the ordinary matter of baryons and electrons as well as the photon and neutrino radiation without any dark matter."

Cosmos At Least 250x Bigger Than Visible Universe, Say Cosmologists� - Technology Review

Cosmos At Least 250x Bigger Than Visible Universe, Say Cosmologists� - Technology Review: "The breakthrough that Vardanyan and pals have made is to find a way to average the results of all the data in the simplest possible way. The technique they use is called Bayesian model averaging and it is much more sophisticated than the usual curve fitting that scientists often use to explain their data...

Instead of asking how well the model fits the data, its asks a different question: given the data, how likely is the model to be correct. This approach is automatically biased against complex models--it's a kind of statistical Occam's razor.