Physics & Astronomy

Citizen Sky is a citizen science project organized by the AAVSO and supported by a 3-year National Science Foundation (NSF) ISE grant focusing on the variable star, epsilon Aurigae. The source epsilon Aurigae is ideal for this project because of the timing of its transit (coinciding with the International Year of Astronomy 2009), and the brightness of the source (allowing for naked eye observing). The overall goals of the project are to: help answer open questions about the epsilon Aurigae system, stimulate new interest in astronomy, allow citizen scientists to experience teamwork and scientific collaboration, and fully participate in the scientific method. The project and its web site provide ways for citizen scientists to practice observing variable sources, acquire and analyze data, and present results.

We report ALMA observations with resolution ≈ 0.5 at 3 mm of the extended Sgr B2 cloud in the Central Molecular Zone (CMZ). We detect 271 compact sources, most of which are smaller than 5000 AU. By ruling out alternative possibilities, we conclude that these sources consist of a mix of hypercompact H ii regions and young stellar objects (YSOs). Most of the newly-detected sources are YSOs with gas envelopes which, based on their luminosities, must contain objects with stellar masses M * 8 M. Their spatial distribution spread over a ∼ 12 × 3 pc region demonstrates that Sgr B2 is experiencing an extended star formation event, not just an isolated 'starburst' within the protocluster regions. Using this new sample, we examine star formation thresholds and surface density relations in Sgr B2. While all of the YSOs reside in regions of high column density (N (H 2) 2 × 10 23 cm −2), not all regions of high column density contain YSOs. The observed column density threshold for star formation is substantially higher than that in solar vicinity clouds, implying either that high-mass star formation requires a higher column density or that any star formation threshold in the CMZ must be higher than in nearby clouds. The relation between the surface density of gas and stars is incompatible with extrapolations from local clouds, and instead stellar densities in Sgr B2

We present high spatial resolution mid-infrared (IR) images of the ring of ultracompact H ii regions in W49A obtained at Gemini North, allowing us to identify the driving source of its powerful H 2 O maser outflow. These data also confirm our previous report that several radio sources in the ring are undetected in the mid-IR because they are embedded deep inside the cloud core. We locate the source of the water maser outflow at the position of the compact mid-IR peak of source G (source G:IRS1) to within 0. ′′ 07. This IR source is not coincident with any identified compact radio continuum source, but is coincident with a hot molecular core, so we propose that G:IRS1 is a hot core driving an outflow analogous to the wide-angle bipolar outflow in OMC-1. G:IRS1 is at the origin of a larger bipolar cavity and CO outflow. The water maser outflow is orthogonal to the bipolar CO cavity, so the masers probably reside near its waist in the thin cavity walls. Models of the IR emission require a massive protostar with M * ≃45 M ⊙ , L * ≃3×10 5 L ⊙ , and an effective envelope accretion rate of ∼10 −3 M ⊙ yr −1. Feedback from the central star could potentially drive the small-scale H 2 O maser outflow, but it has insufficient radiative momentum to have driven the largescale bipolar CO outflow, requiring that this massive star had an active accretion disk over the past 10 4 yr. Combined with the spatialy resolved morphology in IR images, G:IRS1 in W49 provides compelling evidence for a massive protostar that formed by accreting from a disk, accompanied by a bipolar outflow.

As part of the "From Earth to the Universe" (FETTU) project, a NASA-funded tactile exhibit for the visually impaired community was launched in July 2009 at the Martin Luther King Library in D.C. The exhibit is part of the global FETTU exhibit, a project of the International Year of Astronomy 2009. The science content of the exhibit includes explanations of our Sun, Eta Carinae, Crab Nebula, Whirlpool Galaxy, and the electromagnetic spectrum, and was adapted from the NASA-funded Braille/tactile book Touch the Invisible Sky. Multiple geographic locations and venue types have been targeted for the displays. The FETTU-tactile exhibit opens a wider door to experiencing and understanding astronomy, bridging a gap in learning. This exhibit is based upon work supported by the National Aeronautics and Space Administration under proposal 08-EPO08-0068 issued through the Science Mission Directorate.

We describe the remote facilities operated by the Southeastern Association for Research in Astronomy (SARA) , a consortium of colleges and universities in the US partnered with Lowell Observatory, the Chilean National Telescope Allocation Committee, and the Instituto de Astrofísica de Canarias. SARA observatories comprise a 0.96m telescope at Kitt Peak, Arizona; a 0.6m instrument on Cerro Tololo, Chile; and the 1m Jacobus Kapteyn Telescope at the Roque de los Muchachos, La Palma, Spain. All are operated using standard VNC or Radmin protocols communicating with on-site PCs. Remote operation offers considerable flexibility in scheduling, allowing long-term observational cadences difficult to achieve with classical observing at remote facilities, as well as obvious travel savings. Multiple observers at different locations can share a telescope for training, educational use, or collaborative research programs. Each telescope has a CCD system for optical imaging, using thermoelectric cooling to avoid the need for frequent local service, and a second CCD for offset guiding. The Arizona and Chile instruments also have fiber-fed echelle spectrographs. Switching between imaging and spectroscopy is very rapid, so a night can easily accommodate mixed observing modes. We present some sample observational programs. For the benefit of other groups organizing similar consortia, we describe the operating structure and principles of SARA, as well as some lessons learned from almost 20 years of remote operations.

Bill Gray of Project Pluto brought to our attention an error of 0.03°in the listed latitude of our Kitt Peak telescope. While correcting the table where this occurred, we also take the opportunity to update the instrument properties and weather statistics of our remote telescopes.

A tactile/Braille exhibit for the visually impaired community in the USA was launched in July 2009. The exhibit is part of the global From Earth to the Universe (FETTU) project, a Cornerstone of the International Year of Astronomy 2009. The science content of the travelling tactile/Braille exhibit includes explanations of our Sun, Eta Carinae, the Crab Nebula, the Whirlpool Galaxy and the electromagnetic spectrum, and was adapted from the tactile/Braille book Touch the Invisible Sky. We present some of the early observations and findings on the tactile/Braille FETTU exhibit. The new exhibit opens a wider door to experiencing and understanding astronomy for the underserved visually impaired population.

Transiting planets have greatly expanded and diversified the exoplanet field. These planets provide greater access to characterization of exoplanet atmospheres and structure. The Kepler mission has been particularly successful in expanding the exoplanet inventory, even to planets smaller than the Earth. The orbital period sensitivity of the Kepler data is now extending into the Habitable Zones of their host stars, and several planets larger than the Earth have been found to lie therein. Here we examine one such proposed planet, Kepler-69c. We provide new orbital parameters for this planet and an in-depth analysis of the Habitable Zone. We find that, even under optimistic conditions, this 1.7 R ⊕ planet is unlikely to be within the Habitable Zone of Kepler-69. Furthermore, the planet receives an incident flux of 1.91 times the solar constant, which is similar to that received by Venus. We thus suggest that this planet is likely a super-Venus rather than a super-Earth in terms of atmospheric properties and habitability, and we propose follow-up observations to disentangle the ambiguity.

Ultracompact H II Regions have diameters less than 0.1 pc and densities larger than 10 4 cm −3 start expanding when the protostar reaches ∼10 M ⊙ are forming while the massive star is still accreting are closely connected to high-mass star formation

Black holesÐan extreme consequence of the mathematics of General RelativityÐhave long been suspected of being the main energy source for quasars, which emit more energy than any other objects in the Universe. Recent evidence indicates that supermassive black holes reside at the centres of most galaxies, where they are probably the remnants of quasars that have been starved of fuel. As our knowledge of the demographics of supermassive black holes improves, we see clues that they participated in the formation of galaxies, and strongly in¯uenced the evolution towards the present-day structure of their surrounding hosts. Black holes are a prediction of Einstein's theory of gravity, fore-shadowed by the work of Michell and later Laplace in the late eighteenth century. K. Schwarzschild discovered the simplest kind of black hole in the ®rst solution of Einstein's equations of General Relativity, and Oppenheimer was among the ®rst to consider the possibility that black holes might actually form in nature. The subject gained life in the 1960s and 1970s, when supermassive black holes were implicated as the powerhouses for quasars, and stellar-mass black holes were touted as the engines for many galactic X-ray sources. In the past decade, we have progressed from seeking supermassive black holes in only the most energetic astrophysical contexts, to suspecting that they might be routinely present at the centres of galaxies 1±3. The de®ning property of a black hole is its event horizon, the boundary of the region surrounding the black hole from which no matter or photons can escape. Because the horizon itself is invisible, we must often settle for evidence of mass without light. All dynamical techniques for ®nding supermassive black holes at the centres of galaxies rely on a determination of mass enclosed within a radius r from the velocity v of test particles. In newtonian physics, this mass is M r ˆ av 2 r=G. Determining a requires a detailed dynamical analysis, but it is often of order 1. In cases where there is extra mass above that associated with starlight, we refer to the object as a `massive dark object' (MDO). In most of the cases discussed in this paper, it is likely that the MDO is a supermassive black hole (MBH), but in only a few cases have plausible alternatives to a black hole been ruled out. These are important because they establish the reality of MBHs and justify the interpretation of less compelling objects as MBHs. Black holes as energy sources of quasars Black holes are thought to exist in two mass ranges. Small ones of ,10M (are the evolutionary end points of some massive stars. This paper discusses the much more massive black holes that might power quasars and their weaker kin, active galactic nuclei (AGN). Quasars produce luminosities of L,10 46 erg s-1 (,10 12 L (). Where they power double-lobed radio sources, the minimum energy stored in the lobes is E,10 60 ±10 64 erg. The mass equivalent of this energy is M ˆ E=c 2 ,10 6 ±10 10 M (, and the horizon scale associated with that mass is R S ˆ GM=c 2 ,10 11 ±10 15 cm. Although most quasars do not vary much at visual wavelengths, a few objects change their luminosity in minutes at high energies 4,5. Because an object cannot causally vary faster than the light-travel time t across it, such objects must be smaller than R,ct,10 13 cm. Although relativistic corrections can alter this limit somewhat in either direction via Doppler boosting or gravitational redshift, there is no escaping the conclusion that many quasars are prodigiously luminous yet tiny, outshining a galaxy in a volume smaller than the Solar System. The small size, together with the enormous energy output of quasars, mandates black-hole accretion as the energy source. Most investigators believe that quasars and AGNs are MBHs accreting mass from their environment, nearly always at the centre of a galaxy 6±8. Black holes of mass .10 7 M (must normally lie at the centre because dynamical friction drags them to the bottom of the potential well. This location is now clearly established for low-redshift (z (0:3) quasars 9. The connection between MBHs and quasars was ®rst made by Zeldovich 10 and Salpeter 11. Lynden-Bell 12 sharpened the argument by computing the ratio of gravitational energy to nuclear energy: E g E n , e g GM 2 =R e n Mc 2 , e g e n R S R ,100e g 1† where R S is the Schwarzschild radius of a black hole of mass M, R is the size of the quasar, and e g and e n are gravitational and nuclear energy conversion ef®ciencies; the last equality follows from the typical astrophysical thermonuclear ef®ciency of ,1% and the size scale from variability noted above. Because quasars were populous in the youthful Universe, but have mostly died out, the Universe should be populated with relic black holes whose average mass density r u matches or exceeds the mass-equivalent of the energy density u emitted by them 13. The integrated co-moving energy density in quasar light (as emitted) is: u ˆ # ` 0 # ` 0 L©L j z†dL dt dz dz ˆ 1:3 3 10 2 15 erg cm 2 3 2† where © is the co-moving density of quasars of luminosity L, and t is cosmic time. The corresponding present-day mass density for a radiative ef®ciency e is r u ˆ u=ec 2 † ˆ 2 3 10 5 0:1=e†M (Mpc-3. This density can be compared with the luminous density in galaxies, j ˆ 1:1 3 10 8 L (Mpc-3 (ref. 14), to obtain the ratio of the mass in relic MBHs to the light of galaxies: ¨ ˆ r u j ˆ 1:8 3 10 2 3 0:1 e M (L (: 3† Dynamical evidence for massive black holes First steps. The ®rst dynamical evidence for black holes in galactic centres was the measurement 15 of a rising central velocity dispersion , reaching ,400 km s-1 , in the giant elliptical galaxy M87. This object is a prime site to prospect for an MBH by virtue of its AGN featuresÐnon-thermal radio emission, broad nuclear emission lines, and a `jet' of collimated relativistic particles being ejected from the nucleus. Isotropic models of the stellar kinematics, when reviews A14

Systems Engineering training must look at systems engineering processes as a multifaceted and multidisciplined function within and between organizations. Likewise, it must focus on the engineering of systems and the development of a systems engineering mindset through “systems thinking.” One key element of this training is the necessity to have applied systems engineering experiences. There are a number of ways to expose students to the applied aspects of systems engineering: exercises, labs, applied homework, mentoring, projects, and the use of case studies. This paper focuses on the development and use of systems engineering case studies in systems engineering education and training programs. Systems engineering case studies are a special category of the engineering cases that are primarily focused on the application of systems engineering methodologies for complex problems. The Air Force Institute of Technology Systems Engineering Case Studies and the Georgia Institute of Technol...

EyasSAT (patent pending) has transformed the spacecraft systems engineering teaching and learning experience. This new development is a fully functional nanosatellite project that is built up, tested, and “flown” in the classroom. EyasSAT has been used in various space education programs involving high school, undergraduate, and professional students. The overall concept and results from two years of experience are presented.

The purpose of this paper is to give the reader a better understanding of case methodology used in teaching as opposed to case methodology used in research. Both address the same fundamental issues by asking “how” or “why” questions about a contemporary set of events over which the investigator has little or no control. The case method of research rigorously attempts to answer these questions whereas the case method of teaching attempts to stimulate the students by asking these questions and encouraging the students to ask “how” and “why” questions of their own. By addressing these questions in the case methodology of instruction, education receives two significant benefits. First, students are tasked with applying and honing their critical thinking skills, e.g. defining issues, using sound reasoning, and making decisions. Second, instructors maintain that all important tie with industry through the development and use of cases in the classroom. This paper gives a brief description ...

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.