Dark energy is real, say astronomers

[cleanhippie]

A visual impression of the data used in the study. The relevant extra-galactic maps are represented as shells of increasing distance from Earth from left to right. The closest thing seen is our Milky Way galaxy, which is a potential source of noise for the analysis. After this are six shells containing maps of the millions of distant galaxies used in the study. These maps are produced using different telescopes in different wavelengths and are colour-coded to show denser clumps of galaxies as red and under-dense regions as blue. There are holes in the maps due to data quality cuts. The last, largest shell shows the temperature of the cosmic microwave background from the WMAP satellite (red is hot, blue is cold), which is the most distant image of the Universe seen, some 46 billion light-years away. The team have detected (at 99.996% significance) very small correlations between these foreground maps (on the left) and the cosmic microwave background (on the right). Image credits: Earth: NASA/BlueEarth; Milky Way: ESO/S. Brunier; CMB: NASA/WMAP.

(Phys.org)—Dark energy, a mysterious substance thought to be speeding up the expansion of the Universe is really there, according to a team of astronomers at the University of Portsmouth and LMU University Munich. After a two-year study led by Tommaso Giannantonio and Robert Crittenden, the scientists conclude that the likelihood of its existence stands at 99.996 per cent.

Their findings are published in the journal Monthly Notices of the Royal Astronomical Society. Professor Bob Nichol, a member of the Portsmouth team, said:

"Dark energy is one of the great scientific mysteries of our time, so it isn't surprising that so many researchers question its existence. "But with our new work we're more confident than ever that this exotic component of the Universe is real – even if we still have no idea what it consists of."

Over a decade ago, astronomers observing the brightness of distant supernovae realised that the expansion of the Universe appeared to be accelerating. The acceleration is attributed to the repulsive force associated with dark energy now thought to make up 73 per cent of the content of the cosmos. The researchers who made this discovery received the Nobel Prize for Physics in 2011, but the existence of dark energy remains a topic of hot debate.

Many other techniques have been used to confirm the reality of dark energy but they are either indirect probes of the accelerating Universe or susceptible to their own uncertainties. Clear evidence for dark energy comes from the Integrated Sachs Wolfe effect named after Rainer Sachs and Arthur Wolfe.

Read more at: http://phys.org/news/2012-09-dark-energy-real-astronomers.html#jCp

[niyad]

1. most interesting

[DreamGypsy]

2. 46 billion light years

I doubt this article is actually proclaiming that the universe is now estimated to be 46 billion light-years old. That would be big news. I checked the NASA WMAP website and they still say 13.7 ± 0.13 billion years.

My guess is that the 46 bly shell on the image is an extrapolation of the data based on a model of the faster than light expansion of the universe due to dark energy.

I attempted to get a full copy of the article but $35.00 is a bit steep for 24 hour access.

Anyone else have more information? Or other interesting conjectures?

[caraher]

3. Get the preprint for free from arxiv

http://arxiv.org/abs/1209.2125

[DreamGypsy]

5. Yeah, I got that...

but it doesn't contain the lovely color graphic.

I expect the graphic comes from

After a two-year study led by Tommaso Giannantonio and Robert Crittenden, the scientists conclude that the likelihood of its existence stands at 99.996 per cent. Their findings are published in the journal Monthly Notices of the Royal Astronomical Society.

The article for that is the one costing $35/day.

But thanks for the suggestion!

[cleanhippie]

4. I'm looking.

Thats a great question. Perplexing.

[pokerfan]

6. a light-year is a unit of distance, not time

The age of the universe is about 13.75 billion years, but due to the expansion of space humans are observing objects that were originally much closer but are now considerably farther away (as defined in terms of cosmological proper distance, which is equal to the comoving distance at the present time) than a static 13.75 billion light-years distance.[2] The diameter of the observable universe is estimated to be about 28 billion parsecs (93 billion light-years),[3] putting the edge of the observable universe at about 46–47 billion light-years away.[4][5]

http://en.wikipedia.org/wiki/Observable_universe

[DreamGypsy]

8. Thanks. We all should have learned that in third grade. But...

...the article says:

These maps are produced using different telescopes in different wavelengths and are colour-coded to show denser clumps of galaxies as red and under-dense regions as blue.

and shows images apparently (at least by an obvious interpretation of the graphic) from 46 billion light-years away (distance). EMR travels 1 light-year in 1 year. Any electromagnetic radiation from 46 billion light-years away will reach the solar system (if it still existed, which it won') in 32 billion years, give or take a couple years. Hence, my guess that the farthest shell was an extrapolation of real data to a distance which is conjectured to be the within the extent of the universe based on faster than light expansion of the universe. Estimates beyond which we can perform measurements are better termed conjectures unless the model (like the rate of acceleration on the expansion of the universe) is well understood. Such things should be noted in popular articles about science; there's already way too much confusion about basic science.

[bananas]

7. where the 46 billion comes from...

http://en.wikipedia.org/wiki/Observable_universe

The age of the universe is about 13.75 billion years, but due to the expansion of space humans are observing objects that were originally much closer but are now considerably farther away (as defined in terms of cosmological proper distance, which is equal to the comoving distance at the present time) than a static 13.75 billion light-years distance.[2] The diameter of the observable universe is estimated to be about 28 billion parsecs (93 billion light-years),[3] putting the edge of the observable universe at about 46–47 billion light-years away.[4][5]

[Odin2005]

10. It's taking into account the expansion of the universe...

...after the light was emitted.

[DreamGypsy]

9. Well, since I just ranted ...

...on my opinion about deficiencies in (some, not all) popular scientific journalism, I might as well complete the rant.

After my reply last post I went back to the Phys.Org site again. The caption for the graphic also says:

The last, largest shell shows the temperature of the cosmic microwave background from the WMAP satellite (red is hot, blue is cold), which is the most distant image of the Universe seen, some 46 billion light-years away.

So "the most distant image of the Universe seen" was a perfect place to put a comment about how the graphic for that shell was generated. But no, the captioner uses the words 'image' and 'seen'.

Furthermore, an other pet peeve of mine is pandering to cultural biases that deviate from scientific observation. The graphic shows "red is hot, blue is cold" when, of course, blue light is hotter (more energetic) than red light. WMAP is probably responsible for this color faux pas. When I stay in hotel rooms I actually do not repaint the cold water tap with a red indicator and the hot water tap with a blue indicator ....but I think about doing that.

OK. I'm done. Thanks for your patience.