Anuncios

26 Enero 2011: On July 19, 2009 Australian amateur astronomer Anthony Wesley spied a dark scar in the clouds of Jupiter. Wesley alerted professional astronomers and immediately both Gemini telescopes and other large telescopes around the world (and in space) trained their instruments on Jupiter’s new transient feature. Now, after more than a year of studying the unique data a team led by Glenn Orton of NASA’s Jet Propulsion Laboratory and Leigh Fletcher of Oxford University have confirmed that this collision was not like at least one similar past event. The results, published in a recent issue of the journal Icarus (see citations at the end of this feature), indicate that the colliding body was rocky and not an icy comet like the last known collision with Jupiter, the comet Shoemaker-Levy 9 in 1994. These results confirm earlier indications from Hubble Space Telescope data that the collision involved a dense rocky object rather …

25 Enero 2011: Life is busy at the Blanco 4-m telescope at Cerro Tololo Inter-American Observatory right now. This is a bird’s eye view of the dome floor during the early stages of the installation of the f/8 handler for use with the Dark Energy Camera, DECam.

20 Enero 2011: On the night of January 21-22, 2011 the Gemini South 50-watt laser began on-sky engineering testing and commissioning with its successful propagation into the sky over the summit of Cerro Pachón in Chile (see Figures a&b). The laser, an integral part of the Gemini Multi-Conjugate Adaptive Optics System (GeMS), is designed to produce five individual laser guide stars (LGS) that will help provide extremely high angular resolution over a relative wide area of the sky. Adaptive optics systems work by sampling the distortion of starlight by our atmosphere with natural and artificial (laser) guide stars and removing much of the blurring caused by our atmosphere with deformable mirrors. The technical testing and integration of the laser into the GeMS system will continue through this year as the Canopus adaptive optics system and the Gemini South Adaptive Optics Imager are also commissioned and integrated (see geminiann11002c). When complete, this will be …

10 Enero 2011: Once, the stars of any individual globular cluster were interpreted as a single population, all having formed at the same time. Over the last decade, however, evidence for multiple stellar populations has emerged. New work led by Andrea Dupree (Harvard-Smithsonian Center for Astrophysics) now shows direct evidence for helium abundance variations—a sign of multiple histories—in the bright globular cluster Omega Centauri. The team further finds that helium abundance is correlated with overall metal abundance and especially with enhancement of light elements such as aluminum and sodium, which are produced by high-temperature hydrogen burning within stars (geminiann11001a). Helium enhancement is thus likely a consequence of second-generation stars formed from enriched material processed by the earlier generation of stars. Dupree and collaborators, Jay Strader (Harvard-Smithsonian Center for Astrophysics) and Graeme Smith (University of California Observatories/Lick Observatory), used the Phoenix high-resolution spectrograph on Gemini South to measure the near-infrared helium line at a …

14 Diciembre 2010: On December 6-8, 2010 about a dozen representatives from the Association of Universities for Research in Astronomy (AURA) converged at Gemini’s base facility in Hilo, Hawai‘i to discuss a broad range of topics related to diversity in the workforce. Participating institutions included the Space Telescope Science Institute (STScI), the Advanced Technology Solar Telescope (to be built on Haleakala Maui), The National Optical Astronomy Observatory (NOAO), the National Solar Observatory, and Gemini. Representatives from several academic institutions across the United States also participated, providing expert opinion and sharing experiences. This meeting is part of a coordinated effort to match the scientific workforce at the AURA centers, with the demographics of the evolving workforce. The twice-annual meeting brings participants together to review current activities, set future directions and understand issues related to workforce diversity. The agenda ranged from the issue of inspiring a diverse cross-section of youth to pursue careers in science …

24 Noviembre 2010: Above: The full moon rises over Kitt Peak on October 23, 2010. Taken by Alfredo Zazueta just south of Little Tucson, Arizona. Below: The full moon, as imaged during commissioning by the new Mosaic 1.1 imager using the 4-m telescope on Kitt Peak.

23 Noviembre 2010: The discovery of an unusual stellar system combined with near-infrared spectroscopy at Gemini North has allowed astronomers to confirm the spectral type of a cool methane dwarf (T dwarf; geminiann10020a) and determine its temperature, mass, and age with confidence. The pair, consisting of a “dead” white dwarf stellar remnant and the cooler T dwarf, provides a unique laboratory in which the age of the system is well-constrained, making the T dwarf a benchmark for testing ultracool atmospheric physics. The near-infrared spectroscopic observations were made using the Near Infrared Imager and spectrograph (NIRI) on the Gemini North telescope on Mauna Kea, Hawai‘i. The team, led by Avril Day-Jones of the Universidad de Chile and including astronomers from the University of Hertfordshire (UK), and the University of Montreal (Canada), are publishing their results in the journal Monthly Notices of the Royal Astronomical Society (preprint here). Ben Burningham (University of Hertfordshire, UK) and …

5 Noviembre 2010: Typically, determining the ages of stars is very sensitive to the assumptions or theoretical models astronomers employ. In new work, Phillip Cargile (Vanderbilt University), David James (University of Hawai'i at Hilo and Cerro Tololo Inter-American Observatory), and Rob Jeffries (Keele University, UK) take advantage of the time-dependent destruction of lithium in young stars to measure the age of the open cluster Blanco 1. They conclude that the stars formed 132 +/- 24 million years ago. Trace amounts of lithium were created with the origin of the universe, which stars incorporate as they form. However, as stars develop, the high temperatures at their centers destroy the primordial lithium, and the central temperature depends on the age and mass of the forming star. Considering a cluster of stars that all formed at the same time, the more massive (and more luminous) stars deplete their lithium first. Identifying the mass of stars that …

28 Octubre 2010: This composite image taken at Kitt Peak National Observatory outlines the Kepler satellite field of view, and within it, a circle marks the location of the faintest Kepler Mission host star yet, a G8 dwarf star harboring a 1.12 Jupiter-size exoplanet in a 3.9 day orbit. (reported by Howell et al in the Astrophysical Journal) Ground-based confirmation of this planet involved three different telescopes on Kitt Peak: the 2.1-meter, the 4-meter and the WIYN telescope. About the picture:The sky was photographed using a diffraction grating (Glaspey): spectra are visible on either side of the bright stars, the telescopes were imaged separately (Marenfeld) and later combined with the sky image.

13 Octubre 2010: pristine new coat of protected silver now glistens on the Gemini South primary mirror (M1) as part of a routine shut-down on Cerro Pachón in Chile (geminiann10018a). The coating, applied in the Gemini South coating chamber on October 8th, 2010 is thought to be one of the “best ever achieved at Gemini” according to Gemini Optics Engineer, Tomislav Vucina. The planned 28-day shut-down (including engineering checks on the sky) which began on September 27th also includes maintenance of the Cassegrain wrap, the acquisition and guiding unit, the adaptive optics fold mirror, and instruments. “A late-spring snowstorm delayed some of our critical preparations but in the last couple weeks we were able to make up that lost time,” said Gemini Systems Engineer, Brian Walls (geminiann10018b). The Gemini coating process uses “sputtering” to lay-down the ultra-thin 4-layer coatings in the giant coating chamber (geminiann10018c) in the basement of the telescope (Gemini has …

30 Septiembre 2010: As part of the Gemini South NICI Planet-finding campaign, Beth Biller and team have found an unusual star-brown dwarf pair. PZ Tel A, a young sun-like star, was imaged with NICI (Near-Infrared Coronagraphic Imager) using adaptive optics to detect the brown dwarf (PZ Tel B), which is in a highly elliptical orbit. Specialized image analysis techniques were used to remove a vast majority of light from PZ Tel A in this image (left). This is one of few brown dwarfs imaged at a distance closer than 30 Astronomical Units from its parent star. On the right the range of sizes of a brown dwarf compared to Jupiter and the Earth (to scale) is illustrated.Results are being published in ApJ letters 2010 ApJ 720 L82.

20 Septiembre 2010: A team of astronomers, led by Phil Lucas of Hertfordshire University in the UK, have discovered what is currently the coldest star-like object. The object, called UGPS J0722-05, is also of particular interest because it is one of our closest neighbors. UGPS J0722-05 is a cold brown dwarf; these small Jupiter-sized objects are hard to find as they are very faint, and they become fainter, and so even harder to find, with decreasing temperature. UGPS J0722-05 was identified as the only possible brown dwarf in a search of over 600 million sources detected in the plane of our Galaxy by the UK Infrared Telescope (UKIRT) as part of the UKIRT Infrared Deep Sky Survey (UKIDSS). Figure 1 shows the UKIDSS discovery image. Using the Near-Infrared Imager and Spectrometer (NIRI) on Gemini North a spectrum of UGPS J0722-05 was obtained in early February of 2010. This spectrum is shown in Figure …

31 Agosto 2010: This image of NGC 6334 was produced with the NOAO Extremely Wide-Field Infra-Red Mosaic camera (NEWFIRM) during commissioning on the Blanco 4-meter telescope at CTIO. See the Newsletter cover image for more details. Please note that with Newsletter 102 NOAO and NSO have begun separate publications. NSO will shortly offer its own publication.

27 Agosto 2010: Laura Churcher and UK colleagues at the Institute of Astronomy, University of Cambridge, and the University of Keele have used the Thermal-Region Camera Spectrograph (T-ReCS) on the Gemini South telescope to obtain the first resolved image of the debris disk around the 12 million year old star HD191089 (geminiann10016a). The value of a resolved image of a debris disk is not only that it shows the radial location of the dust in the system but, as in this case, it can also reveal exciting features such as brightness differences in the disk, which hint at hidden planets. These observations, at a wavelength of 18 microns, show emission from dust that the central starlight has heated. The image of HD191089's debris disk shows that there is dust between 28 and 90 AU (Pluto's orbit is at about 40 AU in the solar system). Inside the inner edge of the disk there …

26 Agosto 2010: Recent observations with the Near-Infrared Imager (NIRI) on the Gemini North telescope have revealed the presence of a large circumstellar disk around the young embedded protostar L1527. The discovery team, led by University of Michigan astronomer John Tobin and including Lee Hartmann also of the University of Michigan and Laurent Loinard of the Centro de Radioastronomía y Astrofísica - Universidad Nacional Autonoma de Mexico, detected the disk in scattered mid-infrared light, as shown in geminiann10015a. The upper layers of the disk appear as two bright bowl-shaped features. The mid-plane of the disk hides the central protostar from direct view, resulting in the dark band between the disk surfaces. The object, located in a star-forming region in the constellation of Taurus, is at a distance of about 450 light-years (140 parsecs) making it one of the nearest and youngest protostars known. Although L1527 is otherwise a fairly typical protostar and will …

24 Agosto 2010: Testing the idea that the powerful radio galaxies (PRGs) are triggered in galaxy interactions, Cristina Ramos Almeida, Clive Tadhunter (University of Sheffield, UK), and collaborators obtained deep imaging data using the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope to study the morphologies of a complete sample of 46 intermediate redshift (0.05<z<0.7) PRGs. In what represents the first systematic imaging study of a major sample of radio galaxies using an 8-meter-class telescope, the team searched for signs of nearby companions in the 2Jy southern radio galaxy sample to look for secondary nuclei, shells, and extended low surface brightness features such as tidal tails and bridges. The observations show that 78-85% of this complete sample of PRGs present peculiar morphologies at relatively high levels of surface brightness (μv = 23.6 mag/arcsec2). This fraction of distorted morphologies is much higher than for radio quiet ellipticals at similar sample brightness level, implying …

23 Julio 2010: Using the Near-Infrared Coronagraphic Imager (NICI) on the Gemini-South telescope in Chile, an international team led by University of Hawai‘i astronomers Beth Biller and Michael Liu have directly imaged a brown dwarf in a tight orbit around a young Sun-like star. This discovery is a rare find, as the 36 Jupiter-mass brown dwarf companion (dubbed "PZ Tel B" for "PZ Telescopii B") resides only 18 Astronomical Units (AU) from its primary star, similar to the distance of Uranus from the Sun. Most young brown dwarf and planetary companions found by direct imaging are at orbital separations greater than 50 AU – larger than the orbit of Pluto (~40 AU) from the Sun. In the past year, the researchers observed PZ Tel B moving quickly outward from its parent star. However, as recently as 2003 PZ Tel B was undetectable due to its close proximity to its parent star, indicating its …

2 Julio 2010: The first two accepted papers based on observations with the Near-Infrared Coronagraphic Imager (NICI) at Gemini South illustrate the instrument’s potential diverse uses. The papers include discoveries of several previously unknown companions in binary star systems as well as the study of the age distributions of stars in the outer regions of the galaxy M83. Primarily envisioned as a planet-hunting “machine,” NICI combines an 85-element curvature adaptive optics (AO) system, a Lyot coronagraph, and a dual-channel infrared imager into a single instrument. The high image quality provided by the AO system together with the coronagraph’s light-suppression capability optimize NICI for the detection of extremely faint companions to bright stars. To that end, NICI is currently being used in an extensive campaign to search about 300 nearby stars for planetary-mass companions. However, NICI is also useful for many other applications requiring high-resolution or high-contrast imaging. These first papers present the results …

10 Junio 2010: A Canadian-U.S. team led by Patrick Dufour (University of Montreal) discovered the most metal-rich white dwarf known to date by examining thousands of stars from the Sloan Digital Sky Survey. Their analysis, based on follow-up observations using the Gemini North telescope and the Multiple-Mirror Telescope (MMT), shows a clear signature of a tidally destroyed dwarf planet that once orbited the parent star. White dwarfs are essentially dead stars that no longer have nuclear reactions in their core. Thus, they slowly cool off by simply radiating the remaining thermal energy left in the core at the end of their lives. They are also very compact objects with surface gravities on the order of 100,000 times larger than that of Earth. As a result, heavy elements sink rapidly toward the center of the star while light elements tend to float at the surface. Consequently, most white dwarfs are found to have nearly …

8 Junio 2010: The central star is HD 56925, a massive Wolf-Rayet star nearing the end of its lifetime, which is responsible for the wind sweeping through the surrounding molecular cloud. Also listed as NGC 2359, this image was obtained at CTIO by the PROMPT consortium. When not chasing gamma-ray bursts, PROMPT serves a wide variety of users, including Star Shadows Remote Observatory (SSRO), a group of astrophotographers. This image was captured using broadband and narrowband filters: the blue-green color is oxygen emission.