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Herschel's first images promise bright future
Posted: JULY 10, 2009

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ESA's Herschel Space Observatory has completed test observations with all of its instruments with spectacular results, promising a mission rich in discovery.

With a 3.5-metre diameter primary mirror, Herschel is nearly four times larger than any previous infrared space telescope. Galaxies, star-forming factories and stellar graveyards were among the telescope's first targets, which set the precedent for the thousands of images to follow in the coming months and years.

Herschel's first look at barred spiral galaxy M66 and face-on spiral M74. Structural features in the galaxies are clearly resolved. Image: ESA and the SPIRE Consortium.

Even though the instruments are not fully calibrated, these "first-light" images are still impressive. The SPIRE instrument (Spectral and Photometric Imaging Receiver) provided the best images of galaxies M66 and M74 at a 250 micron wavelength yet. SPIRE detects the dusty clouds of gas that give rise to stars, rather than the stars themselves, but clearly reveals structures such as distinct spiral arms, a central bar and the nuclei of the galaxies.

The frames are also filled with many more distant galaxies showing up only as point sources, as well as structures that might be due to clouds of dust in our own Milky Way Galaxy.

"I am thrilled by the quality of these first images from SPIRE," says Professor Robert Kennicutt of Cambridge University, who will use Herschel to study nearby galaxies. "They reveal the cold dust and star formation in these galaxies in stunning detail, and are a sneak preview of future observations that promise to revolutionize our understanding of star formation in the Universe."

A close up look at the structure of the Cat's Eye Nebula, by the PACS instrument suite. Image: ESA and the PACS Consortium.

Meanwhile, the Photodetector Array Camera (PACS) soaked up the sights of the Cat's Eye Nebula as its first target, which consists of a complex shell of gas shed by a dying star. To understand how an initially spherical star can create such intricate nebula, PACs takes images in spectral lines to see how the wind from the star shapes the nebula in three dimensions. Using its photometer, PACS also imaged the nebula in the 70 micron band, revealing the structure of a dust ring with an opening on one side.

Herschel's Heterodyne Instrument for the Far-Infrared (HIFI) also struck gold on its first attempt, detecting ionised carbon, carbon monoxide and water in a massive star-forming region known as DR21, in the constellation Cygnus. The instrument works by zooming in on specific wavelengths to reveal the fingerprint spectral lines unique to each atom and molecule. As the mission progresses, HIFI will study the role of gas and dust in the formation of stars and even planets.

These spectacular first look results provide a taster of what Herschel will be able to offer in the future. "We have dreamed of seeing such images for a very long time, more than ten year," says Dr Laurent Vigroux of CEA/IRFU Saclay and Institut d’Astrophysique de Paris, and Co-Principal Investigator for the SPIRE Team. "And they are an achievement: the first real images in the far infrared, opening a new window in astronomy."

The instruments are now in the performance verification phase, where they will be further tested and calibrated until the end of November before science operations officially commence.

More first-look images can be found on the ESA-news homepage.