Page last updated at 09:06 GMT, Friday, 10 July 2009 10:06 UK

Herschel shows breadth of vision

By Jonathan Amos
Science reporter, BBC News

M74: The Herschel telescope is tuned to see the dust in the galaxy

Europe's Herschel space observatory is set to become one of the most powerful tools ever to study the Universe.

The "first light" data from its three instruments demonstrates a remarkable capability even though their set-up is still not complete.

Galaxy images released on Friday by the European Space Agency show detail previously unseen in the objects.

The pictures - and the thousands that will follow - should give new insights on star formation and galaxy evolution.

"We have some excellent images; they're not calibrated, but they look spectacular," said Dr Göran Pilbratt, Esa's Herschel project scientist.

"They tell you we are working; it's just fantastic," he told BBC News.

Different view

Herschel is sensitive to light at long wavelengths - in the far-infrared and sub-millimetre range (55 to 672 microns).

Observations at these longer wavelengths do not produce the "pretty pictures" obtained at shorter wavelengths, such as the visible light detected by the famous Hubble telescope.

M66: SPIRE has not yet been properly calibrated

What they can do, however, is see features in celestial objects that are invisible to Hubble; and with Herschel's giant 3.5m mirror, the detail becomes extremely rich.

Friday's release includes the first two galaxy observations using the European telescope's SPIRE (Spectral and Photometric Imaging Receiver) instrument.

SPIRE has pictured M74 (also known as NGC 628), a face-on spiral galaxy located about 24 million light-years from Earth in the constellation Pisces; and M66 (also known as NGC 3627), a barred spiral galaxy located about 36 million light-years away in the constellation Leo.

What Herschel sees in these objects is not their stars but the dusty clouds of gas that give rise to stars.

M74 (SPIRE/Esa)
SPIRE's view of M74 at progressively shorter wavelengths (from left to right)
The shortest wavelengths will always produce the sharpest images
A range of wavelengths are needed to see all the features of a galaxy

"We're seeing the hidden life of the galaxy that never shows up in visible light images," explained Professor Matt Griffin, the principal investigator on the UK-led SPIRE consortium.

"We see the dust which is a tracer for all the gas and dust which are the raw materials from which star formation occurs. These are fairly normal galaxies where star formation is going on in a continuous cycle; and the red [freckles] you see in the images are very distant galaxies, probably undergoing intense bursts of star formation."

The design keeps Herschel's critical detectors in an ultra-cold state

The Cardiff University researcher added: "This really was take off the blindfold, point and shoot, and see what we see. These were the very first observations; and there is a long way to go in terms of the way we set up the instrument, do the image processing and the map making. But it's incredible."

Also in the release are new images from Herschel's Photoconductor Array Camera and Spectrometer (PACS); and data from its Heterodyne Instrument for the Far Infrared (HIFI).

PACS, which produced the very first Herschel image last month, has been used to look at a well-known planetary nebula - the Cat's Eye Nebula. The object has nothing to do with planets but is in fact an ageing star surrounded by a shell of ejected material.

The new PACS images illustrate the complex structure of the shell.

HIFI has a fine ability to detect the presence of particular chemical species in gas clouds that are birthing new stars. In a test observation of a star-forming region known as DR21 in the constellation Cygnus, the instrument could pick out charged carbon, carbon monoxide, and water.

Cat's Eye Nebula (Esa-PACS)
Hubble's image of the Cat's Eye (1) at visible wavelengths is a classic
But Herschel is now able to see this object in a completely new way
The PACS instrument can home in on specific chemical signatures
Oxygen (2) and nitrogen (3) distribution reveal the nebula's 3D structure
Why do these chemical species not spread evenly (4) through the nebula?
Scientists expect Herschel to be able to address many such questions

Herschel was despatched into space along with Esa's Planck telescope on 14 May.

Over the course of the past two months, both astronomical satellites have been moving to observation positions some 1.5 million km from Earth, on its "night side".

The long journey has been used by engineers to switch on and check out all of the telescopes' systems.

This past week, a major review of the observatories' status was held in Darmstadt, Germany. The meeting marked the formal handover of the facilities from the industrial manufacturers - a pan-European industrial consortium led by Thales Alenia Space.

"We're now going to start to tune the instruments for maximum performance," explained Dr Pilbratt. "We're going to try them out in many different observing situations in order to learn how to get the best out of them."

This verification period will then be followed by a six-week demonstration phase in which the operations team hope to show the world the full power of a perfectly prepared, fully mature Herschel space observatory.

Routine operations should begin towards the end of the year.

Herschel is expected to continue working through to 2013, by which time the super-fluid helium that keeps its instruments and detectors in the necessary ultra-cold state to make observations will have boiled off.

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