New method 'confirms dark energy'

19 May 2011 Last updated at 21:27 GMT By Paul Rincon Science reporter, BBC News One type of observation measured a pattern in the distribution of galaxies First results from a major astronomical survey using a cutting-edge technique appear to have confirmed the existence of mysterious dark energy.

Dark energy makes up some 74% of the Universe and its existence would explain why the Universe appears to be expanding at an accelerating rate.

The finding was based on studies of more than 200,000 galaxies.

Scientists used two separate kinds of observation to provide an independent check on previous dark energy results.

Two papers by an international team of researchers have been accepted for publication in the Monthly Notices of the Royal Astronomical Society journal.

One type of observation used by the astronomers involves measuring a pattern in how galaxies are distributed in space. This pattern is known by the term "baryon acoustic oscillations".

The second type of observation involves measuring how quickly clusters of galaxies have formed over time. Both of these techniques confirmed the existence of dark energy and the acceleration in the expansion of the Universe.

The concept of dark energy was first invoked in the late 1990s by studying the brightness of distant supernovas - exploding stars.

Einstein was right

To explain why the expansion of the Universe was speeding up, astronomers had to either rewrite Albert Einstein's theory of gravity or accept that the cosmos was filled with a novel type of energy.

"The action of dark energy is as if you threw a ball up in the air, and it kept speeding upward into the sky faster and faster," said co-author Dr Chris Blake of the Swinburne University of Technology in Melbourne, Australia.

"The results tell us that dark energy is a cosmological constant, as Einstein proposed. If gravity were the culprit, then we wouldn't be seeing these constant effects of dark energy throughout time."

The Anglo-Australian telescope was used in the galaxy survey

The latest findings have come from a galaxy survey project called WiggleZ, which began in 2006 and finished this year. WiggleZ used data from Nasa's Galaxy Evolution Explorer (Galex) space telescope and the Anglo-Australian Telescope on Siding Spring Mountain in Australia.

The survey mapped the distribution of galaxies in an unprecedented volume of the Universe, looking eight billion years back in time - more than half the age of the Universe.

Cosmologist Bob Nicholl, who was not involved with the research, told BBC News: "This is a major step forward. These guys are serious, major scientists and we've been waiting for this result for some time.

The professor of astrophysics at Portsmouth University, UK, added: "It's re-confirmation of dark energy, it gives us another data point to fit our theories around and it shows us the way to the future. More astronomers are going to be doing this in years to come."

While dark energy makes up about 74% of the Universe, dark matter - which does not reflect or emit detectable light - accounts for 22%. Ordinary matter - gas, stars, planets and galaxies - makes up just 4% of the cosmos.

However, despite scientists being able to infer the existence of dark energy and dark matter, these phenomena still elude a full explanation.

Paul.Rincon-INTERNET@bbc.co.uk

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Japan plant confirms partial meltdowns

24 May 2011 Last updated at 03:59 GMT The problems with the Fukushima nuclear plant have raised questions over Tepco's future Tokyo Electric Power (Tepco) has confirmed the meltdown of extra fuel rods in reactors at its damaged Fukushima nuclear power plant.

The company said that the rods were in its Number 2 and Number 3 reactors.

Tepco has been trying to contain radiation from the plant, crippled by the 11 March earthquake and tsunami.

The company said that it planned to stick to its timetable of getting the radiation under control by January.

Tepco's announcement came on the same day that a team from the United Nations' atomic watchdog, the International Atomic Energy Agency (IAEA), kicked off a visit in Japan.

100 hours Continue reading the main story

Based on our analysis, we have reached the conclusion that a certain amount of nuclear fuel has melted down.”

End Quote Ken Matsuda Tepco Earlier this month, Tepco had revealed that rods at its Number 1 reactor melted down. It was thought that a similar problem had occurred in the other reactors but it was difficult to confirm.

"Based on our analysis, we have reached the conclusion that a certain amount of nuclear fuel has melted down," Ken Matsuda, a Tepco spokesman told the BBC.

He said the analysis came from a report that Tepco was required to submit to Japan's Nuclear and Industrial Safety Agency (Nisa).

The spokesman added that most of the fuel from the Number 2 reactor had melted approximately 100 hours after the earthquake, which measured 9 on the Richter scale, struck Japan.

The meltdown in the Number 3 reactor took place about 60 hours after the quake.

Mr Matsuda said the new discovery would not alter Tepco's plans.

The company has said that it wants to reach a "cold shutdown" of the power plant by January, and has been trying to cool the reactors and get the unstable fuel rods back under control.

"This result does not change our work," he said.

Continue reading the main story Roland Buerk BBC News, Tokyo

Japan's government has faced some criticism at home, and from its neighbours, over its handling of the crisis at the Fukushima nuclear power station.

The Chief Cabinet Secretary Yukio Edano has said the team from the International Atomic Energy Agency is being welcomed into the country to demonstrate transparency.

Led by Mike Weightman, Britain's chief inspector of nuclear installations, the 20 experts from a dozen countries are expected to visit the crippled plant.

They'll also meet officials as they compile a report which will be presented to member states of the IAEA next month.

The aim is to learn lessons to improve nuclear safety worldwide, and to share expertise.

Radiation monitoring Earlier in May, Tepco revealed that the damage sustained by the Number 1 reactor immediately after the earthquake and tsunami was far more severe than initially thought.

Professor Nobumasa Akiyama of Hitotsubashi University in Tokyo said Tepco's new revelation reinforces that idea.

In an effort to better understand the current situation in Japan specialists from the IAEA are joining other international experts in Tokyo for a fact-finding mission.

They are expected to submit a report on Japan's handling of the nuclear crisis to present to the IAEA's member states.

The group is expected to visit the Fukushima nuclear plant, though details have not been finalised.

Professor Akiyama said that the IAEA had come under criticism for its reaction to the Fukushima crisis.

"First of all, it has not been able to provide the information on what's going on on the ground," he said. "Secondly, it hasn't been able to provide a prescription for the solution of the crisis."

Mr Akiyama said the nuclear agency would be expected to provide more guidelines for nuclear safety after the visit to Japan this week.

He added that it may need to be beef up its funding and staff if it was going to be able to fulfil its mandate.

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