*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 274 2009 September 6 ==================================================== Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/ GLYCINE DISCOVERED IN COMET Goddard Space Flight Center NASA scientists have discovered traces of the amino acid glycine in samples of Comet Wild 2 returned by the Stardust spacecraft. Stardust passed through dense gas and dust surrounding the icy nucleus of Wild 2 on 2004 January 2. As the spacecraft shot past, a special collection grid filled with aerogel -- a novel sponge-like material that is more than 99% empty space -- 'gently' captured samples of the comet's gas and dust. The grid was stowed in a capsule that detached itself from the spacecraft and parachuted to Earth on 2006 January 15. Since then, scientists have been analyzing the samples to learn a bit about comet formation and our Solar System's history. Preliminary analysis detected glycine in the aluminium foil from the sides of tiny chambers that held the aerogel in the collection grid and also in a sample of the aerogel. However, since terrestrial life uses glycine, at first the team was unable to rule out contamination from sources on Earth. It was possible that the glycine originated from handling or manufacture of the Stardust spacecraft itself. The new research used isotopic analysis to adjudicate on that possibility. A glycine molecule from space will tend to have more carbon-13 atoms in it than glycine from Earth. The team found that the Stardust glycine has an extra-terrestrial carbon-isotope signature, indicating that it originated in the comet. OLD STAR SHEDS NEW LIGHT ON OLD TIMES Subaru Telescope Facility The chemical composition of the old star BD +44 493, recently investigated with the Subaru telescope, may have relevance to how the earliest stars developed when the Universe was young. According to the Big Bang theory, the Universe was initially composed almost entirely of hydrogen and helium. The creation of heavier elements occurred later, through the process of nucleosynthesis, in which more-complex atomic nuclei were formed inside stars. Therefore, the proportion of heavier elements in an astronomical object (its 'metallicity') may provide an indication of its age. Older stars have lower metallicities than younger stars such as our Sun. Because their atmospheres usually preserve the chemical composition of the gas from which they formed, old, low-metallicity stars retain evidence of the chemical abundances that existed at the time of their own creation -- information that provides clues to processes occurring early in the history of the Universe. That idea has prompted searches for stars with very low metal content; one called HE1327-2326 has the record for the lowest iron content ever seen, but its ratio of carbon and nitrogen relative to iron was remarkably high. Another very iron-deficient star, HE0107-5240, shows a similar pattern. Astronomers supposed that the metal-enrichment histories of those two stars were quite different from that of other low-metal stars. Spectroscopic studies of a larger sample of metal-deficient stars have been made with the Subaru telescope in an effort to provide more clues about their early development. At one point a ninth-magnitude star was observed in twilight as a reference star for the programme. Analysis showed that that star, BD +44 493, contained only 1/5000 of the heavy elements of the Sun and was 10 times brighter than any star of such low metallicity known so far. A follow-up observation showed a relatively high abundance of carbon, as in the cases mentioned above, and gave abundance ratios for other elements. The best explanation of the findings is that the star was formed from a gas cloud polluted by a supernova explosion of a first-generation massive star, which yielded carbon-rich but metal-poor material. The measurements of BD +44 493 have thus provided new evidence of the type of supernovae present in the very early phase of the Galaxy. EXTRA-SOLAR PLANET OUGHT NOT TO EXIST Science Daily A photometric survey called WASP has discovered a planet that has ten times the mass of Jupiter but orbits its star in less than a day. That poses a challenge to the experts' understanding of tidal interactions in planetary systems. The planet, called WASP-18b, belongs to a now-common class of extra-solar planets known as 'hot Jupiters'. It is so massive, and so close to its star -- only about three stellar radii away -- that tidal interactions between star and planet ought to cause the planet to spiral inwards to its destruction in less than a million years. Yet, astronomers think that the WASP-18 parent star is about a billion years old, so either we have to admit that the likelihood of catching sight of WASP-18b at this critical time is only about one in a thousand, or else tidal dissipation in the WASP-18 system somehow manages to be a thousand times less than in our Solar System. If the planet's remaining existence is as short as predicted, the orbital decay should be measurable within a decade. CYGNUS X-1 Science Daily Since its discovery 45 years ago, Cygnus X-1 has been one of the most intensively studied cosmic X-ray sources. About a decade after its discovery, it secured a place in the history of astronomy when a combination of X-ray and optical observations led to the conclusion that it was a black hole, the first such identification. The Cygnus X-1 system is thought to consist of a black hole with a mass about 10 solar masses in a close orbit with a blue supergiant star with a mass of about 20 Suns. Gas flowing away from the supergiant in a fast stellar wind is focused by the black hole, and some of it forms a disc that spirals into the hole. The gravitational energy released by the infalling gas powers the X-ray emission from Cygnus X-1. Although more than a thousand scientific articles have been published on Cygnus X-1, its status as a nearby black hole continues to attract the interest of scientists seeking to understand the nature of such holes and how they affect their environment. Observations with Chandra and XMM-Newton have helped to investigate the properties of the stellar wind that fuels the emission, and determining the hole's rate of spin. The conclusion is that Cygnus X-1 is spinning unusually slowly. STAR-BIRTH RATIO NOT FIXED CSIRO Australia Doubt has been cast on a long-held beliefs about how stars are formed. It has been thought that in a family of new-born stars the ratio of massive stars to lesser ones was always pretty much the same -- for instance, that for every star 20 times more massive than the Sun or larger, there would be 500 stars the mass of the Sun or less. The distribution of stellar masses at birth is called the 'initial mass function' (IMF). Most of the light we see from galaxies comes from stars of the highest mass, while the total mass is dominated by those of lower masses. By measuring the amount of light from a population of stars, and making some corrections for the stars' ages, astronomers can use the IMF to estimate the total mass of that population. Results for different galaxies can be compared only if the IMF is the same everywhere, but astronomers have now shown that the ratio of high-mass to low-mass newborn stars differs between galaxies. For instance, small 'dwarf' galaxies form many more low-mass stars than expected. To arrive at that finding, researchers used galaxies from the HIPASS Survey (H I Parkes All-Sky Survey). Selecting galaxies on the basis of their neutral hydrogen gave a sample of many different shapes and sizes, unbiased by their star-formation histories. The astronomers measured two tracers of star formation, ultraviolet and H-alpha emissions, in 103 galaxies with the GALEX satellite and the 1.5-m CTIO optical telescope in Chile. H-alpha emission traces the presence of very massive stars called O stars, which are born with masses more than 20 times that of the Sun. The UV emission traces both O stars and the less-massive B stars -- overall, stars more than three times the mass of the Sun. The ratio of H-alpha to UV emission was found to vary from galaxy to galaxy, implying that the IMF did too, at least at its upper end. That confirms a tentative suggestion made by French astronomers in 1987. The new research suggests that the IMF is sensitive to the physical conditions of the star-forming region. GIANT GALAXY HOSTS THE MOST DISTANT SUPERMASSIVE BLACK HOLE RAS Astronomers have been able to detect the giant galaxy surrounding the most distant known supermassive black hole. The galaxy, so distant that it is seen as it was 12.8 billion years ago, is as large as the Milky Way galaxy and its black hole has a mass at least a billion times that of our Sun. The galaxy and black hole must have formed rather 'rapidly' in the early Universe. Knowledge of the host galaxies of supermassive black holes is needed if astronomers are ever to understand how galaxies and black holes have evolved together. After forming, supermassive black holes continue to grow because their gravity draws in surrounding matter. The energy released in that process accounts for the light emitted from the regions around the holes. Studying host galaxies in the distant Universe has been difficult because the light from the vicinity of the hole swamps that from the faint galaxy around it. In the case referred to here, the scientists used CCDs on the Subaru telescope on Mauna Kea. They found that 40% of the near-infrared light came from the galaxy itself and 60% from the clouds of material surrounding and illuminated by the black hole. INDIA LOSES MOON SATELLITE LINKS BBC India's space agency has reported that communication with the Chandrayaan-1 Moon-orbiting spacecraft was lost abruptly just over a week ago. The craft was launched last October in what was billed as a two-year mission. Its launch, from the southern state of Andhra Pradesh, was a major step for India as it seeks to keep pace with other space-faring nations in Asia. The probe was intended to orbit the Moon, compiling a 3-D atlas of the surface and mapping the distribution of elements and minerals. Powered by a single solar panel generating about 700 watts, the probe carries five instruments built in India and six constructed in other countries, including the US, Britain and Germany. The mission was expected to cost £45m, considerably less than Japanese and Chinese probes sent to the Moon last year. Bulletin compiled by Clive Down (c) 2009 the Society for Popular Astronomy The Society for Popular Astronomy has been helping beginners to amateur astronomy -- and more experienced observers -- for more than 50 years. If you are not a member then you may be missing something. Membership rates are extremely reasonable, starting at just £16 a year in the UK. You will receive our bright quarterly magazine Popular Astronomy, regular printed News Circulars, help and advice in pursuing your hobby, the chance to hear top astronomers at our regular meetings, and other benefits. The best news is that you can join online right now with a credit card or debit card at our lively website: http://www.popastro.com/ Astronomica is sponsoring the SPA Electronic News Bulletin. 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