A couple of weeks ago we celebrated the Hubble Space Telescope鈥檚 20 years of discovery, and today astronomers gathered in Noordwijk, The Netherlands, to recognise another milestone by an up-and-coming space observatory.
It鈥檚 been almost a year since the European Space Agency launched its Herschel Space Observatory, which shared its ride to orbit with the Planck spacecraft. Both payloads are doing well: Planck has been busy compiling the most accurate map ever made of the cosmic microwave background (CMB), the relic radiation from the big bang.
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But the focus at today鈥檚 gathering was Herschel and its trove of amazing observations. The spacecraft boasts a mirror 3.5 metres across, more than twice Hubble鈥檚 light-gathering power. But Herschel looks almost exclusively at infrared light, at wavelengths from 55 to 670 microns. Since a telescope鈥檚 resolution decreases at longer wavelengths, Herschel needs all that aperture to see fine-scale details in its targets.
It also needs help to keep its own 鈥渂ody heat鈥� from swamping the faint signals from the depths of space. An onboard supply of liquid helium should keep the detectors hovering near absolute zero for another three years. Cooling the primary mirror is another story 鈥� it鈥檚 too big to refrigerate, so it stays hidden behind a sun shield to remain near -193 掳C.
Herschel carries : a pair of cameras (PACS and SPIRE) and a ultra-high-precision spectrometer (HIFI). The mission鈥檚 one serious glitch came last August, when HIFI fell silent, but in January controllers switched to a set of backup electronics and it鈥檚 been working fine since then.
Bubble birth
At a news briefing on Thursday, team member Annie Zavagno of the Laboratory of Astrophysics of Marseilles in France focused on the little-understood process that spawns beefy stars with at least eight times the sun鈥檚 mass.
These heavyweights are rarely found, both because just-forming stars exercise lots of self-control when gobbling up interstellar gas and because massive stars are short-lived 鈥� they exhaust their hydrogen fuel in just a few million years.
Zavagno and her team have used Herschel to spot high-mass stars as they form, and it now seems that the trigger points occur along the margins of rapidly expanding ionised-hydrogen bubbles.
Meanwhile, the recently rejuvenated HIFI spectrometer has been tracking down concentrations of ionised water, which has a distinct and strong spectral signature.
鈥淲ater is an excellent diagnostic tool to probe the chemical and physical structure of the interstellar medium,鈥� explained Alexander Tielens of Leiden University. In particular, he noted, water helps cool the gas and dust surrounding newborn stars by radiating infrared energy to space.
Dark horse
But what was really eye-catching was a side-by-side comparison of the famed Horsehead Nebula in Orion (see image). It turns out that the dark 鈥渧oids鈥� that give this showpiece its distinctive appearance in visible light are ablaze with star formation when spied in the infrared.
Steve Eales of the University of Cardiff showed the paired views to demonstrate the potential of the (short for Astrophysical Terahertz Large Area Survey), which will map 550 square degrees of sky in five infrared bands. Eales expects the 600-hour effort to reveal some 250,000 galaxies.
Herschel is showing us the 鈥渨arm universe鈥� as never before, and these results demonstrate that we鈥檝e only scratched the surface of what this spacecraft will be revealing in the months and years ahead.
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