Are "standard candle" supernovae reliable?

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brian livesey
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Are "standard candle" supernovae reliable?

Post by brian livesey »

A white dwarf has to have 1.4 times the mass of the Sun to explode as a Type Ia supernova. These supernovae all have the same brightness, which makes them useful as standard candles for measuring cosmic distances and the effects of dark energy.
Astronomers had thought that to reach the mass required to explode as a Type Ia, a white dwarf has to acquire mass by merging with another star, or sloughing off material from a companion.
Now, Marina Orio and colleagues at the University of Wisconsin Madison have calculated that some white dwarfs can go off with just 0.85 of the solar mass and without a secondary star.
This is because lighter elements like hydrogen and helium can trigger an explosion at a lower density than carbon alone: in a normal Type Ia supernova, carbon atoms fuse and release enough energy to blow the dwarf apart.
The new calculations show that if a white dwarf is "contaminated" with lighter elements, the star can have a shorter fuse: "This could mean that up to half of supernovas are 30% closer than believed. This could also mean that dark energy is more powerful than we thought" - NEW SCIENTIST, 31/01/2015.
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big_kev
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Re: Are "standard candle" supernovae reliable?

Post by big_kev »

Interesting, however if the supernovae are 30% closer isn't this the same as them being approx 30% fainter, upon which the theory of dark energy is based.

In other words it was assumed that because these "standard candles" appeared approx. 30% fainter than expected then they must be further away than expected, hence "dark energy" must be accelerating an expansion of the universe.

If it turns out that they are in reality fainter then the " dark energy" is not required and hence does not exist....there's about 70% of the universe just vanished...gone !

Could be a very important realisation !
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