Page last updated at 19:27 GMT, Wednesday, 17 March 2010

Planck spies massive dust clouds

By Jonathan Amos
Science correspondent, BBC News

The location of the region of sky mapped by Planck (Esa)
Planck can see really cold dust sweeping through our galaxy

Europe's Planck observatory has given another brief glimpse of its work.

The space telescope's main goal is to map the "oldest light" in the Universe, but this data is being kept under wraps until the surveying is complete.

Instead, Planck scientists have released a snapshot of the colossal swathes of cold dust that spread through the Milky Way galaxy.

Such imagery will be very useful to astronomers seeking to understand star formation.

The regions of space that are thick with gas and dust are most likely to give rise to new suns.

It's the 'reject' for some people, but the 'treasure' for others
Dr Jan Tauber, Esa Planck project scientist

The latest Planck pictures will be of special interest to researchers working on the European Space Agency's (Esa) other great telescope, Herschel.

This observatory is investigating processes that trigger the creation of stars.

Dr Jan Tauber is the Esa project scientist on the Planck mission.

He told BBC News: "The latest release shows how well Planck works on its own, but it also emphasises the complementarity with Herschel; with Planck looking at the whole sky at very large scales, and Herschel zooming in and making very detailed investigations of a much smaller part of the sky."

Planck and Herschel were launched last May and sent to an observing position some 1.5m km (0.9m miles) from Earth.

Herschel sees the sky at far-infrared wavelengths. Planck, on the other hand, sees the Universe at radio wavelengths.

The new Planck view combined with data from a previous satellite

The latter is trying to make the finest-ever measurements of what has become known as the Cosmic Microwave Background (CMB).

This is light that was finally allowed to move out across space once a post-Big-Bang Universe had cooled sufficiently to permit the formation of hydrogen atoms.

Scientists can glean from the CMB information about the age, contents and structure of the cosmos.

But to investigate this "fossil light", Planck must first clean the signal of extraneous emissions coming from unrelated phenomena.

These include the very cold clumps and lanes of dust that sit in between the stars.

Although this "contamination" may be a nuisance to Planck's main mission, the subtracted information can still be mined by astronomers with interests outside the CMB.

"It's the 'reject' for some people, but the 'treasure' for others," Dr Tauber said.

Herschel and Planck views of the sky (Esa)
The filaments are apparent at large scales (Planck image, right) and at small-scales (Herschel image, left) in the Milky Way

Wednesday's pictures come from Planck's highest frequency channels and cover about 10% of the sky.

They show the great filaments of dust within about 500 light-years of Earth. In the wavelengths it is working, Planck is well-tuned to see cold matter. Some of the dust it detects is about minus 261C (12 kelvin).

Planck scanning animation (Esa)
The Planck observatory always points away from the Sun and rotates once per minute
As it rotates, it gathers precise temperature information from a narrow "strip" of the sky
The strips are then fitted together to form an unprecedented thermal picture of our Universe
It takes about six months to cover the whole sky. The aim is to scan the sky at least four times

"We have the ability to look at very cold emission, essentially dust. We can do unbiased searches over the whole sky for these regions that are very important because they are where stars are forming," Dr Tauber explained.

Planck should complete its first all-sky survey within weeks. Recently agreed funding should see the telescope eventually acquire at least four-times coverage.

The project team plans to release a catalogue of "point-like sources" in January 2011. These are interesting new objects that emit at radio wavelengths that, again, will be worth following up with other telescopes.

But the intention is to hold back the key CMB data until those involved in the telescope venture have had a chance to analyse its significance for themselves. CMB maps and scientific papers should be published at the end of 2012.

Past pioneers in the study of the Cosmic Microwave Background have earned a clutch of Nobel Prizes and there is great hope that the super-sensitivity of Planck will advance the field considerably.

There was some controversy last year when the only previous public release of imagery from Planck was "reverse-engineered" by external researchers to try to get some crude science results.


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