Accelerating Universe ? — Not so Fast*

Cop Giving “Exhibition of Speed” Ticket (excess Acceleration)

Cop Giving “Exhibition of Speed” Ticket (excess Acceleration)

Maybe the rush to embrace an Accelerating Universe and Dark Energy was a bit too hasty.

New analysis shows that the rulers used to measure Supernova 1A brightness curves were unknowingly measuring two different types of Supernova 1As (1) with two different brightnesses. The analysis also found the brighter types at larger distances. This, at least partially, nullifies both Acceleration and “Dark Energy.”

In 1998, some astrophysicists got excited about distant Supernovae IA seemingly acting differently than close ones. Specifically they found distant Supernovae (at intermediate Redshifts) appear about 25% dimmer than expected at maximum brightness. This comparison was from a total of only 58 “near” and far supernovae events.

The interpretation of this purported difference in close vs far Supernovae 1As, is that dimmer means the more distant Supernovae must be farther away than standard Big Bang expects them to be, thus the Big Bang conjectured Expansion was accelerating.

This quickly incited the conjecture that there is some sort of unobserved (and as of yet unexplained) “Dark Energy” pushing the Universe apart. Many Cosmologists now assert that “Dark Energy” composes some 74% of the Universe’s energy.

Nobel prizes were awarded, even though their sample size was “a very small number of”(only 58) supernovae with “large statistical error bars.”

Supernovae 1A are used as rulers, called “Standard Candles,” because of their relative uniformity. (However, calling unimaginably gigantic explosions from different sized stars “identical” seems a bit of a stretch.)

Well, recently Arizona University Astronomers looked at a data set of 23 Supernovae in ultraviolet light from Hubble and the Swift satellite. It quickly became clear to them that there are two different types of 1A Supernovae, now called Red and Blue, that have different brightnesses or Luminosity. The subtle difference was also there in visible light data, but it was much more obvious in the Ultraviolet data.

As they looked closer they found more dimmer, red, supernovae 1As close to us and brighter, blue ones dominating farther away(2).

Even if this could be a result of Malmquist Bias, it means the brightness for all Supernovae 1As needs to be recalibrated and separated into two categories (Perhaps SN-1Ab and SN-1Ar).

Dramatically, the analysts say this means there is less purported Acceleration and Dark Energy than currently believed.

Only after the original Supernovae data is recalibrated (to the extent possible) or adequate new data are collected will we understand how much less, if any, Acceleration and Dark Energy remain.

References and further reading:

“The Changing Fractions Of Type Ia Supernova Nuv–Optical Subclasses With Redshift” by Peter A. Milne et all.

Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant, Riess, Adam G et all.

* I stole the wonderful title for this article from “Accelerating universe? Not so fast” by Daniel Stolte. I’ve never done that before, but his headline was just so excellent, so perfect I had to do it – and give him full credit for the wonderful word play.

Acceleration of the Expansion of the Universe: A Brief Early History of the Supernova Cosmology Project (SCP), Gerson Goldhaber)


1. Until this research was reported, seven different types of type of Supernovae were  recognized.

2. Notably, the opposite of how redshift and blueshift changes with distance / velocity away from us – where blue shifted phenomena are closer to us than most redshifted phenomena.


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4 Responses to Accelerating Universe ? — Not so Fast*

  1. Kaley says:

    I’m wondering if the analysts got it backwards.

    It seems that since the more distant Supernovae were already dimmer than expected,
    then correcting for the lack of distant dim red Supernovae would make the distant population even dimmer yet.

    Wouldn’t that mean the expansion was occurring faster than before ?

    • David says:

      It appears you are right Kaley.

      If the distant supernovae are predominantly blue,
      correcting for that means that median or mean of the distant supernovae is actually redder, dimmer than currently believed.

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