Dark mammoth trunks in the merging galaxy NGC 1316 and a mechanism of cosmic double helices

NGC 1316 is a giant, elliptical galaxy containing a complex network of dark, dust features. The morphology of these features has been examined in some detail using a Hubble Space Telescope, Advanced Camera for Surveys image. It is found that most of the features are constituted of long filaments. There also exist a great number of dark structures protruding inwards from the filaments. Many of these structures are strikingly similar to elephant trunks in H II regions in the Milky Way Galaxy, although much larger. The structures, termed mammoth trunks, generally are filamentary and often have shapes resembling the letters V or Y. In some of the mammoth trunks the stem of the Y can be resolved into two or more filaments, many of which showing signs of being intertwined. A model of the mammoth trunks, related to a recent theory of elephant trunks, is proposed. Based on magnetized filaments, the model is capable of giving an account of the various shapes of the mammoth trunks observed, including the twined structures.Comment: Accepted for publication in Astrophysics & Space Scienc

Near Mission Operations: Demonstrated Strengths and Weaknesses of a Faster, Better, Cheaper Program

The Near Earth Asteroid Rendezvous (NEAR) Mission was successfully launched on February 17, 1996 from Cape Canaveral Air Force Base. A small mission operations team of 8 to 12 people have controlled the NEAR spacecraft from the JHU/APL campus in Maryland since then, using Deep Space Network ground stations and NASCOM circuitry, a Commercial Off The Shelf (COTS) ground computer system, and a unique streamlined concept of operations. The primary science data gathering portion of the mission will not begin until rendezvous with the asteroid EROS in January 1999, but 3 exciting bonus science observations have already occurred: visible images of the Earth\u27s Moon were taken on mission day 4, passive momentum dumping was demonstrated using solar pressure and small attitude offsets held for long periods of time, and visible images of the comet Hyakutake were taken from 1 million kilometers range on mission day 37. These bonus science observations were made possible by the less-formal concept of operations coupled with a very experienced senior group of people running operations. In the arena of mission operations, the mantra faster, better, cheaper should be discarded and replaced with faster, cheaper, increased risk . No significant failures have occurred in any flight or ground subsystem, and that is fortunate because short-term operational risk was uncomfortably high in the area of contingency readiness. Contingency readiness was limited in scope due to lack of schedule time ( faster ) and man-hours ( cheaper ). No long-term operational risks are expected, but there was a sobering amount of team cross training and software tool development which remained unfinished 30 days after launch. The NEAR mission three year cruise period provides ample time to complete this work: early mission experience with simultaneous operations and software tool development will be discussed