"This means we can't entirely rule out that the Spot is caused by an unlikely fluctuation explained by the standard model. But if that isn't the answer, then there are more exotic explanations. Perhaps the most exciting of these is that the Cold Spot was caused by a collision between our universe and another bubble universe.
If further, more detailed,
analysis of CMB data proves this to be the case then the Cold Spot might be
taken as the first evidence for the multiverse - and billions of other
universes may exist like our own."
A supervoid is unlikely to
explain a 'Cold Spot' in the cosmic microwave background, according to the
results of a new survey, leaving room for exotic explanations like a collision
between universes. The researchers, led by postgraduate student Ruari Mackenzie
and Professor Tom Shanks in Durham University's Centre for Extragalactic
Astronomy, publish their results in Monthly Notices of the Royal Astronomical
Society.
The map below of the cosmic
microwave background (CMB) sky produced by the Planck satellite. Red represents
slightly warmer regions, and blue slightly cooler regions. The Cold Spot is
shown in the inset, with coordinates on the x- and y-axes, and the temperature
difference in millionths of a degree in the scale at the bottom.
The cosmic microwave
background or CMB, a relic of the Big Bang, covers the whole sky. At a
temperature of 2.73 degrees above absolute zero (or -270.43 degrees Celsius),
the CMB has some anomalies, including the Cold Spot. This feature, about
0.00015 degrees colder than its surroundings, was previously claimed to be
caused by a huge void, billions of light years across, containing relatively
few galaxies.
The accelerating expansion
of the universe causes voids to leave subtle redshifts on light as it passes
through via the integrated Sachs-Wolfe effect. In the case of the CMB this is
observed as cold imprints. It was proposed that a very large foreground void
could, in part, imprint the CMB Cold Spot which has been a source of tension in
models of standard cosmology.
Previously, most searches
for a supervoid connected with the Cold Spot have estimated distances to
galaxies using their colours. With the expansion of the universe more distant
galaxies have their light shifted to longer wavelengths, an effect known as a
cosmological redshift.
The more distant the galaxy
is, the higher its observed redshift. By measuring the colours of galaxies,
their redshifts, and thus their distances, can be estimated. These measurements
though have a high degree of uncertainty.
In their new work, the
Durham team presented the results of a comprehensive survey of the redshifts of
7,000 galaxies, harvested 300 at a time using a spectrograph deployed on the
Anglo-Australian Telescope. From this higher fidelity dataset, Mackenzie and
Shanks see no evidence of a supervoid capable of explaining the Cold Spot
within the standard theory.
The researchers instead
found that the Cold Spot region, before now thought to be underpopulated with
galaxies, is split into smaller voids, surrounded by clusters of galaxies. This
'soap bubble' structure is much like the rest of the universe, illustrated in
Figure 2 by the visual similarity between the galaxy distributions in the Cold
Spot area and a control field elsewhere.
Mackenzie commented: "The
voids we have detected cannot explain the Cold Spot under standard cosmology.
There is the possibility that some non-standard model could be proposed to link
the two in the future but our data place powerful constraints on any attempt to
do that."
If there really is no
supervoid that can explain the Cold Spot, simulations of the standard model of
the universe give odds of 1 in 50 that the Cold Spot arose by chance.
For the moment, all that can
be said is that the lack of a supervoid to explain the Cold Spot has tilted the
balance towards these more unusual explanations, ideas that will need to be
further tested by more detailed observations of the CMB.
How do we know that? We thought Pluto was a planet and it is at the edge of the solar system, but turned out it is just a moon. You erred on Pluto so I don't know if your assessment or theory is right or wrong and it is billions of miles out beyond our solar system. hmmmm
ReplyDeleteWell it's called science. It evolves with our knowledge of the world. And pluto just changed "category", the science about it didn't change at all...
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