Astronomers make first radio observations of key type of supernova

The uncertainty of science: Using a variety of telescopes, astronomers have not only made the first radio observations of key type of supernova, they have also detected helium in the data, suggesting that this particular supernova of that type was still atypical.

This marks the first confirmed Type Ia supernova triggered by a white dwarf star that pulled material from a companion star with an outer layer consisting primarily of helium; normally, in the rare cases where the material stripped from the outer layers of the donor star could be detected in spectra, this was mostly hydrogen.

Type Ia supernovae are important for astronomers since they are used to measure the expansion of the universe. However, the origin of these explosions has remained an open question. While it is established that the explosion is caused by a compact white dwarf star that somehow accretes too much matter from a companion star, the exact process and the nature of the progenitor is not known. [emphasis mine]

The highlighted sentences are really the most important take-away from this research. Type Ia supernovae were the phenomenon used by cosmologists to detect the unexpected acceleration of the universe’s expansion billions of years ago. That research assumed these supernovae were well understood and consistently produced the same amount of energy and light, no matter how far away they were or the specific conditions which caused them.

This new supernovae research illustrates how absurd that assumption was. Type Ia supernovae are produced by the interaction of two stars, both of which could have innumerable unique features. It is therefore unreasonable as a scientist to assume all such supernovae are going to be identical in their output. And yet, that is what the cosmologists did in declaring the discovery of dark energy in the late 1990s.

It is also what the scientists who performed this research do. To quote one of the co-authors: “While normal Type Ia supernovae appear to always explode with the same brightness, this supernova tells us that there are many different pathways to a white dwarf star explosion.”

Forgive me if I remain very skeptical.

Fermi proves that novae produce gamma rays

The Fermi Gamma-Ray Space Telescope has discovered that novae, small scale stellar explosions similar to some supernovae but far less powerful, also produce gamma rays when they explode.

A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Each nova explosion releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays, emission with energy levels millions of times greater than visible light and usually associated with far more powerful cosmic blasts.

What is significant about this is that it demonstrates a solid link between novae and supernovae, since only recently have scientists shown that some supernovae also produce gamma ray bursts. It suggests that the two explosions are produced by somewhat similar processes, but at very different scales. This fact will have important ramifications in the study of stellar evolution and the death of stars. For example, some nova stars often go nova repeatedly. Other data suggest that some more powerful eruptions can be recurrent as well. Extending this recurrent pattern to supernova suggests many new theoretical possibilities.

Have astronomers found a future supernova?

A press release from the Carnegie Institute today described a recent paper by astronomers that might have identified a star in the Milky Way that might go supernova sometime in the future. The star QU Carinae, is a cataclysmic variable, a binary system in which material dumped from one star onto another periodically causes an outburst of X-rays.

I emailed Stella Kafka, the lead scientist of the research paper, to find out how far away QU Carinae is and how soon it might go supernova. She responded as follows:
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