May 29, 2020

10.06.10: Herschel Celebrates its 1st Year in Space.

While everyone was celebrating Hubble’s 20th this past April, and equally amazing instrument past a quiet milestone: the European Space Agencies’ Herschel Space Observatory passed its first anniversary in space. On May 14, 2009, Herschel was launched as part of a dual payload along with the Planck spacecraft which is in the midst of mapping the cosmic microwave background. Sporting an 11.5 foot mirror (larger than HSTs) Herschel specializes in the far-infrared to submillimeter wavelengths of 55 to 670 microns. To this end, Herschel must be kept “on ice” and is placed at the L2 point in a Lissajous orbit to observe its infrared quarry. This also means that it is well beyond any hope of repair, which will also be the case for the James Webb Space telescope when it’s launched in 2014. An onboard supply of liquid helium keeps the detectors cooled down; cooling of the primary is completed by deployment of an enormous sunshade. Herschel sports three instruments: The PACS (the Photodetecting Array Camera and Spectrometer) and SPIRE (the Spectral and Photometric Imaging Receiver) cameras, and the on-again, off again ultra-high-precision spectrometer (HIFI, or the Heterodyne Instrument for the Far Infrared) detector. Herschel allows us to probe the “cold universe” in ways that would be impossible from the ground. Images such as the famous Horsehead Nebula in the far-infrared have given us key insight as to the inner workings of these dusty regions. In addition, studies have zeroed in on key star forming regions inaccessible from ground based telescopes, such as the enormous RCW 120 interstellar bubble 4,300 light years distant, which may one day collapse into an ultra-massive star. And that’s just the beginning… a proposed program known as ATLAS (the Astrophysical Terahertz Large Area Survey) may utilize Herschel’s capabilities to map a 550 square degree area (about 23.5 degrees on a side) of the sky at five wavelengths as a sort of “Herschel Deep Field” in the submillimeter. Such as task is expected to take up to 600 hours of exposures to complete and uncover perhaps a quarter million primordial galaxies at new wavelengths… Hershel is definitely a platform worth keeping tabs on!

Astro-Challenge of the Week: Aristarchus & the TLP.

This week, we turn your attention to the waxing crescent Moon and an enduring mystery that surrounds a unique crater; Aristarchus. About 40 km across, this crater was named after the Greek scientist Aristarchus of Samos by map maker Giovanni Riccioli. This lone crater sits on the Aristarchus plateau amid the Mare Oceanus Procellarum. This crater is near the lunar limb and becomes visible during the early waxing crescent phase, and is markedly brighter than the surrounding lunar plains.

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