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.”

Using black holes to measure the Universe's rate of expansion

Using black holes to measure the Universe's rate of expansion: By adding together measurements of the amount of energy being emitted from the vicinity of the black hole to the amount of radiation which reaches Earth, it's possible to infer the distance to the black hole itself and the time in the history of the universe when the energy was emitted.
Getting an accurate estimate of the radiation being emitted depends on the properties of the black hole. For the specific type of black holes targeted in this work, the amount of radiation emitted as the object draws matter into itself is actually proportional to its mass, say the researchers. Therefore, long-established methods to measure this mass can be used to estimate the amount of radiation involved.

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.

ScienceShot: A Better Cosmic Yardstick

ScienceShot: A Better Cosmic Yardstick: Now, astronomers have used observations of eight pairs of binary stars in the distant cluster to develop a new figure. The orbits of these pairs are aligned such that one star passes in front of the other as seen from Earth, which allowed the researchers to approximate the size of each member from the durations of the eclipses. The spectra of these cool, mature stars allowed the team to determine their surface temperatures. Together, those bits of data enabled the astronomers to estimate the amount of energy emitted by the stars, and that, in conjunction with observations of their actual brightness as seen from Earth, allowed the researchers to estimate the distance to each pair.

Speed of Universe's Expansion Measured Better Than Ever: Scientific American

Speed of Universe's Expansion Measured Better Than Ever: Scientific American: The new value reduces the uncertainty in the Hubble Constant to just 3 percent, and improves the precision of the measurement by a factor of three compared to a previous estimate from the Hubble Space Telescope...

Spitzer observed 90 cepheid stars, and was able to measure their apparent brightness more precisely than previous studies, leading the way to a more refined measurement of their distances, and the expansion rate of space.

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.”

Longer Cosmic Ruler Based On Black Holes - Science News

Longer Cosmic Ruler Based On Black Holes - Science News: The brightness of an active nucleus is tightly related to the radius of a region of hot gases surrounding the central black hole. When scientists determine that radius, they can predict how intrinsically bright the nucleus should be — and compare that value to how bright it appears, which depends on distance...
A technique called reverberation mapping measures how long it takes photons being kicked out of the black hole’s immediate neighborhood to reappear after they’ve traversed the hot, gassy maelstrom surrounding the black hole. Because light travels at a constant speed, astronomers can determine the gassy region’s radius. Then, the luminosity of the active galactic nucleus can be calculated.