Center For Astrophysics Research Articles

Models as feedback: Developing representational competence in chemistry.

[Correction Notice: An Erratum for this article was reported in Vol 107(2) of Journal of Educational Psychology (see record 2015-16952-001). The affiliation of Shamin Padalkar was incorrectly listed in the author note as the Inter-University Centre for Astronomy and Astrophysics (IUCAA). Dr. Padalkar is now a freelance consultant. Dr. Padalkar’s contact information as it appears in the author note otherwise remains the same.] Spatial information in science is often expressed through representations such as diagrams and models. Learning the strengths and limitations of these representations and how to relate them are important aspects of developing scientific understanding, referred to as representational competence. Diagram translation is particularly challenging for students in organic chemistry, and although concrete models greatly help in solving diagram translation problems, most students do not use models spontaneously. In 2 experiments, we examined the effectiveness of instructional interventions for teaching diagram translation using models. In Experiment 1, students drew diagrams and checked their accuracy by attempting to match concrete models to their solutions (model-based feedback). The instruction helped students in the experimental group to identify their mistakes, understand the usefulness of concrete models, and led to large improvements in performance, compared with a control group. To examine whether feedback, the opportunity to match models, or both was the critical aspect of the intervention, in Experiment 2, 1 group was provided only verbal feedback (by a tutor) and another group matched diagrams and concrete models, but not in the context of receiving an evaluation of their pretest performance. Feedback alone did not improve performance relative to a control group, but the opportunity to match models and diagrams improved performance relative to control. The results indicate that using models as feedback is an effective way of training representational competence in the domain of organic chemistry and more generally in science, technology, engineering, and mathematics disciplines.

ERRATUM: “CHAOS IN THE TEST PARTICLE ECCENTRIC KOZAI-LIDOV MECHANISM” (2014, APJ, 791, 86)

The Astrophysical Journal, 802:71 (1pp), 2015 March 20 doi:10.1088/0004-637X/802/1/71 © 2015. The American Astronomical Society. All rights reserved. ERRATUM: “CHAOS IN THE TEST PARTICLE ECCENTRIC KOZAI-LIDOV MECHANISM” (2014, APJ, 791, 86) Gongjie Li 1 , Smadar Naoz 2 , Matt Holman 1 , and Abraham Loeb 1 Harvard-Smithsonian Center for Astrophysics, The Institute for Theory and Computation, 60 Garden Street, Cambridge, MA 02138, USA; gli@cfa.harvard.edu Department of Physics & Astronomy, Division of Astronomy and Astrophysics, UCLA, Los Angeles, CA 90095, USA Received 2015 February 5; accepted 2015 February 11; published 2015 March 24 The following corrections should be made to the published version of our article. A typographical error occurred in Equations (1) and (2) in the published paper. The rest of the paper is unaffected. The correct equations are F quad ( J , , J z , Ω ) ) J J )( 1 F oct ( J , , J z , Ω ) 11 J z 5 J z 2 15 J z 3 J J 2 J 3 11 J z 5 J z 2 15 J z 3 J J 2 J 3 J J 2 J 2 ) cos (2 cos ( cos ( J z J z 2 J z 3 J J 2 J 3 J z J z 2 J z 3 J J 2 J 3 J 2 J z 2 2 J J z 2 J 2 J z 2 J 2 cos (3 cos (3

Trials and tribulations of playing the devil's advocate

Beginning with his student days at school and college, the author describes his training at Cambridge with special emphasis on his mentor Fred Hoyle. His early experience of participating in a controversy at Cambridge played a major role in giving him the confidence to defend his scientific ideas. All through his later life he chose areas that were not part of mainstream research. These included the steady state theory and later the quasi steady state cosmology, action at a distance, noncosmological redshifts, quantum conformal cosmology, etc. After being a founding member of the Institute of Theoretical Astronomy (IOTA) at Cambridge, the author joined the Tata Institute of Fundamental Research (TIFR) in Mumbai and later moved to Pune to set up the Inter-University Centre for Astronomy and Astrophysics (IUCAA). He briefly reviews his own work and ends by pointing out the difficulties a non-conformist scientist faces in his professional life. In the conclusion, he mentions his interests in science popularization and science fiction for which he has won awards and appreciation, including UNESCO's Kalinga Prize.

Arthur Michael Wolfe

Arthur Michael Wolfe

How do astronomers share data? Reliability and persistence of datasets linked in AAS publications and a qualitative study of data practices among US astronomers.

We analyze data sharing practices of astronomers over the past fifteen years. An analysis of URL links embedded in papers published by the American Astronomical Society reveals that the total number of links included in the literature rose dramatically from 1997 until 2005, when it leveled off at around 1500 per year. The analysis also shows that the availability of linked material decays with time: in 2011, 44% of links published a decade earlier, in 2001, were broken. A rough analysis of link types reveals that links to data hosted on astronomers' personal websites become unreachable much faster than links to datasets on curated institutional sites. To gauge astronomers' current data sharing practices and preferences further, we performed in-depth interviews with 12 scientists and online surveys with 173 scientists, all at a large astrophysical research institute in the United States: the Harvard-Smithsonian Center for Astrophysics, in Cambridge, MA. Both the in-depth interviews and the online survey indicate that, in principle, there is no philosophical objection to data-sharing among astronomers at this institution. Key reasons that more data are not presently shared more efficiently in astronomy include: the difficulty of sharing large data sets; over reliance on non-robust, non-reproducible mechanisms for sharing data (e.g. emailing it); unfamiliarity with options that make data-sharing easier (faster) and/or more robust; and, lastly, a sense that other researchers would not want the data to be shared. We conclude with a short discussion of a new effort to implement an easy-to-use, robust, system for data sharing in astronomy, at theastrodata.org, and we analyze the uptake of that system to-date.

Wondering About Things

Here you will find facts about and the opinions of an American astrophysicist who practiced in the second half of the twentieth century. The title explains why I did it. I invented some new ideas, I applied them to some astro objects, I computed things with pen and paper; I ended up thinking that I had succeeded in pushing the field ahead a bit. Attracted by Newtonian theory, I did some experiments too. I love hydrodynamics and magnetic fields in space. The math is beautiful, and the objects are stupendous in their brilliant displays. For some reason I meditated on gases between the stars, their pressures and motions. I left the stars to others, believing that their physics was under control. As I grew older, I had to decide whether to direct others rather than just myself and ended up at the Harvard–Smithsonian Center for Astrophysics doing both. It was thrilling because I had never had management experience and was flying by the seat of my pants, as I guess other astrodirectors do. In the process, I advised the US government on future directions in astronomy, chairing a number of committees. It is astonishing that the government is interested in astronomy, and it is exciting to interact with the people in the National Academy of Sciences (NAS), the Congress, and the Executive branch who have dedicated their lives to enable the expansion of our knowledge of astronomy. Along the way I studied more abstract concepts in physics, including magnetic helicity and its relation to the winding numbers of nonabelian particle physics. These are topological concepts that I should have learned in grad school but did not. This review has two parts. The first part is for scientists, and covers my life in chronological order. The second part is for laymen who are interested in science. It gives a flavor of my scientific work with no math and a minimum of jargon.

Semiempirical photospheric models of a solar flare on May 28, 2012

The variation of the photosphere physical state during the decay phase of SF/B6.8-class solar flare on May 28, 2012 in active region NOAA 11490 is studied.We used the data of the spectropolarimetric observations with the French–Italian solar telescope THEMIS (Tenerife, Spain). Semi-empirical model atmospheres are derived from the inversion with SIR (Stokes Inversion based on Response functions) code. The inversion was based on Stokes profiles of six photospheric lines. Each model atmosphere has a two-component structure: a magnetic flux tube and non-magnetic surroundings. The Harvard Smithsonian Reference Atmosphere (HSRA) has been adopted for the surroundings. The macroturbulent velocity and the filling factor were assumed to be constant with the depth. The optical depth dependences of the temperature, magnetic field strength, and line-of-sight velocity are obtained from inversion.According to the received model atmospheres, the parameters of the magnetic field and the thermodynamical parameters changed during the decay phase of the flare. The model atmospheres showed that the photosphere remained in a disturbed state during observations after the maximum of the flare. There are temporal changes in the temperature and the magnetic field strength optical depth dependences. The temperature enhancement in the upper photospheric layers is found in the flaring atmospheres relative to the quiet-Sun model. The downflows are found in the low and upper photosphere at the decay phase of the flare.

Tsinghua Center for Astrophysics and the Dark Universe

The Tsinghua Center for Astrophysics (THCA) was founded in 2001 by Prof. Li Tipei and Shang Rencheng. A distinguishing characteristic of THCA's astrophysics program is its emphasis on space X-ray and gamma-ray instrumentation, by taking advantage of Tsinghua's strong programs on nuclear physics, nuclear engineering, space and aeronautics engineering, as well as electronics and information technology. The main research directions in THCA include high energy astrophysics and cosmology with space and ground observations in X-rays and gamma-rays, and more recently in optical wavelengths, radio-astronomy, gravitational waves, dark matter and dark energy analyses and projects.

OPTICAL SPECTRA OF 73 STRIPPED-ENVELOPE CORE-COLLAPSE SUPERNOVAE

We present 645 optical spectra of 73 supernovae (SNe) of Types IIb, Ib, Ic, and broad-lined Ic. All of these types are attributed to the core collapse of massive stars, with varying degrees of intact H and He envelopes before explosion. The SNe in our sample have a mean redshift <cz> = 4200 km/s. Most of these spectra were gathered at the Harvard-Smithsonian Center for Astrophysics (CfA) between 2004 and 2009. For 53 SNe, these are the first published spectra. The data coverage range from mere identification (1-3 spectra) for a few SNe to extensive series of observations (10-30 spectra) that trace the spectral evolution for others, with an average of 9 spectra per SN. For 44 SNe of the 73 SNe presented here, we have well-determined dates of maximum light to determine the phase of each spectrum. Our sample constitutes the most extensive spectral library of stripped-envelope SNe to date. We provide very early coverage (as early as 30 days before V-band max) for photospheric spectra, as well as late-time nebular coverage when the innermost regions of the SNe are visible (as late as 2 years after explosion, while for SN1993J, we have data as late as 11.6 years). This data set has homogeneous observations and reductions that allow us to study the spectroscopic diversity of these classes of stripped SNe and to compare these to SNe associated with gamma-ray bursts. We undertake these matters in follow-up papers.

Give until it hurts.

Give until it hurts.

Catalyst Induced Hydrino Transition (CIHT) electrochemical cell

SUMMARY Atomic hydrogen is predicted to form fractional Rydberg energy states H(1/p) called ‘hydrino atoms’ wherein n = 1/2,1/3,1/4,…,1/p (p ≤ 137 is an integer) replaces the well-known parameter n = integer in the Rydberg equation for hydrogen excited states. The transition of H to a stable hydrino state H[aH/p = m + 1] having a binding energy of p2 × 13.6 eV occurs by a nonradiative resonance energy transfer of m × 27.2 eV (m is an integer) to a matched energy acceptor such as nascent H2O which has a potential energy of 81.6 eV (m = 3) to form an intermediate that decays with the emission of continuum bands with short wavelength cutoffs and energies of m2 × 13.6 eV. The predicted H(1/4) continuum radiation in the region 10 to 30 nm was observed first at BlackLight Power, Inc. (BLP) and reproduced at the Harvard Center for Astrophysics (CfA) wherein H2O catalyst was formed by a hydrogen reduction reaction at the anode of a hydrogen pinch plasma. By the same mechanism, the nascent H2O molecule formed by an oxidation reaction of OH− at a hydrogen anode is predicted to serve as a catalyst to form H(1/4) with an energy release of 204 eV compared to the 1.48 eV required to produce H from electrolysis of H2O. CIHT cells, each comprising a Ni anode, NiO cathode, a LiOH–LiBr eutectic mixture as the electrolyte, and MgO matrix exploit hydrino formation as a half-cell reaction to serve as a new electrical energy source. The cells were operated under intermittent H2O electrolysis to generate H at the anode and then discharged to form hydrinos wherein trace H2O vapor was supplied as entrained in an inert gas flow in otherwise closed cells. Net electrical production over the electrolysis input was measured using an Arbin BT 2000 (<0.1% error) and confirmed using a digital oscilloscope, wherein no theoretical conventional energy was possible. Materials characterizations included those that quantified any compositional change of the electrolyte by elemental analysis using ICPMS, XRF, and XRD, and SEM were performed on the anode. The electrical energies were continuously output over long-duration, measured on different systems, configurations, and modes of operation and were typically multiples of the electrical input that in most cases exceed the input by a factor of greater than 10. Calorimetry of solid fuels that exploited the same catalyst and a similar reaction mechanism showed excess thermal energy greater than 10 times the maximum possible from any conventional reaction. The predicted molecular hydrino H2(1/4) was identified as a product of CIHT cells and solid fuels by MAS 1H NMR, ToF-SIMS, ESI-ToFMS, electron-beam excitation emission spectroscopy, Raman spectroscopy, photoluminescence emission spectroscopy, FTIR, and XPS. Copyright © 2013 John Wiley & Sons, Ltd.

The high resolution X-ray imaging detector planes for the MIRAX mission

The MIRAX X-ray observatory, the first Brazilian-led astrophysics space mission, is designed to perform an unprecedented wide-field, wide-band hard X-ray (5–200 keV) survey of Galactic X-ray transient sources. In the current configuration, MIRAX will carry a set of four coded-masks telescopeswith high spatial resolution Cadmium Zinc Telluride (CZT) detector planes, each one consisting of an array of 64 closely tiled CZT pixelated detectors. Taken together, the four telescopes will have a total detection area of 959 cm2, a large field of view (60° × 60° FWHM), high angular resolution for this energy range (6 arcmin) and very good spectral resolution ( ∼ 2 keV @ 60 keV). A stratospheric balloon-borne prototype of one of the MIRAX telescopes has been developed, tested and flown by the Harvard-Smithsonian Center for Astrophysics (CfA) as part of the ProtoEXIST program. In this paper we show results of validation and calibration tests with individual CZT detectors of the ProtoEXIST second generation experiment (P2). Each one of 64 detector units of the P2 detector plane consists of an ASIC, developed by Caltech for the NuSTAR telescope, hybridized to a CZT crystal with 0.6 mm pixel size. The performance of each detector was evaluated using radioactive sources in the laboratory. The calibration results show that the P2 detectors have average energy resolution of ∼ 2.1 keV @ 60 keV and 2.3 @ 122 keV. P2 was also successfully tested on near-space environment on a balloon flight, demonstrating the detector unit readiness for integration on a space mission telescope, as well as satisfying all MIRAX mission requirements.

Cosmic ray variations recorded by the CARPET facility on March 7, 2011

The CARPET cosmic ray detector was installed in 2006 in the Argentinean Andes at an altitude of 2550 m at the El Leoncito Astronomical Complex (CASLEO) in San Juan, Argentina (S31.8, W69.3; R c = 9.659.65 GV). This instrument was developed at the Lebedev Physical Institute (LPI) in Russia as part of an international collaboration between the LPI, Brazil’s Mackenzie Center for Radioastronomy and Astrophysics (CRAAM), and the CASLEO. This work presents the results from analyzing variations in cosmic ray intensity recorded by the CARPET facility during the solar proton event of March 7, 2011. Also used in our analysis were the experimental data obtained by the GOES, FERMI, and ISS spacecraft during this solar event.

A New Inductively Driven Plasma Generator (IPG6)—Setup and Initial Experiments

As part of the partnership between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University and the Institute of Space Systems (IRS) at the University of Stuttgart, a new design for a modular inductively driven plasma generator (IPG) is being developed and tested within CASPER and the IRS. The current IPG design is built on a well-established heritage of modular IPGs designed and operated at IRS. This latest IPG source enables the electrodeless generation of high-enthalpy plasmas and will provide CASPER researchers with the ability to operate with various gases at plasma powers of approximately 15 kW. It will also provide minimized field losses and operation over a wide scope of parameters not possible using existing designs requiring flow-controlled stabilization.

GOLIA: An INTEGRAL archive at INAF–IASF Milano

We present the archive of the INTEGRAL data developed and maintained at INAF-IASF Milano. The archive comprises all the public data currently available (revolutions 0026-1079, i.e., December 2002 - August 2011). INTEGRAL data are downloaded from the ISDC Data Centre for Astrophysics, Geneva, on a regular basis as they become public and a customized analysis using the OSA 9.0 software package is routinely performed on the IBIS/ISGRI data. The scientific products include individual pointing images and the associated detected source lists in the 17-30, 30-50, 17-50 and 50-100 keV energy bands, as well as light-curves binned over 100 s in the 17-30 keV band for sources of interest. Dedicated scripts to handle such vast datasets and results have been developed. We make the analysis tools to build such an archive publicly available. The whole database (raw data and products) enables an easy access to the hard X-ray long-term behavior of a large sample of sources.

Soft X-ray continuum radiation from low-energy pinch discharges of hydrogen

AbstractUnder a study contracted by GEN3 Partners, spectra of high current pinch discharges in pure hydrogen and helium were recorded in the extreme ultraviolet radiation region at the Harvard Smithsonian Center for Astrophysics (CfA) in an attempt to reproduce experimental results published by BlackLight Power, Inc. (BLP) showing predicted continuum radiation due to hydrogen in the 10–30 nm region (Mills, R. L. and Lu, Y. 2010 Hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm. Int. J. Hydrog. Energy35, 8446–8456, doi:10.1016?j.ijhydene.2010.05.098). Alternative explanations were considered to the claimed interpretation of the continuum radiation as being that emitted during transitions of H to lower-energy states (hydrinos). Continuum radiation was observed at CfA in the 10–30 nm region that matched BLP's results. Considering the low energy of 5.2 J per pulse, the observed radiation in the energy range of about 120–40 eV, reference experiments and analysis of plasma gases, cryofiltration to remove contaminants, and spectra of the electrode metal, no conventional explanation was found in the prior or present work to be plausible including contaminants, electrode metal emission, and Bremsstrahlung, ion recombination, molecular or molecular ion band radiation, and instrument artifacts involving radicals and energetic ions reacting at the charge-coupled device and H2 re-radiation at the detector chamber. Moreover, predicted selective extraordinarily high-kinetic energy H was observed by the corresponding Doppler broadening of the Balmer α line.

Mapping the milky way [2013 Tech To Watch

Astronomers who study the Milky Way don't have it easy. Bound to the solar system, they're on the inside looking out, all the while whipping around the galactic center at roughly 900 000 kilometers per hour. made it more than a little tricky to pin down fundamental details. It's still unclear, for example, how massive the Milky Way is and whether it's on a collision course with the nearby Andromeda galaxy. And there's still a lot of uncertainty about its basic structure. There's been a pretty active debate in the last couple of years whether there are two or four spiral arms, says Mark Reid, a radio astronomer at the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Mass. That's pretty basic.

IUCAA (Inter-University Centre for Astronomy and Astrophysics, Pune, India): A Brief Description

The Inter-University Centre for Astronomy and Astrophysics (IUCAA), located in the city of Pune in India, is an autonomous institution under the University Grants Commission (UGC). It is a centre of excellence for research in astronomy and astrophysics (A&amp;A) and related areas. It also serves as a platform for the entire university community in the country for work in A&amp;A. IUCAA has a vibrant environment for research and development and attracts hundreds of national and international visitors every year who use its facilities, benefit from the interaction with the faculty and provide their own expertise to the centre.

Muñoz‐Jaramillo receives 2011 F. L. Scarf Award

Andrés Muñoz‐Jaramillo has been awarded the F. L. Scarf Award, given annually to a recent Ph.D. recipient for outstanding dissertation research that contributes directly to solar‐planetary sciences. Muñoz‐Jaramillo's dissertation is entitled “Towards better constrained models of the solar magnetic cycle.” He presented an invited talk and was formally presented with the award at the 2011 AGU Fall Meeting, held 5–9 December in San Francisco, Calif. Muñoz‐Jaramillo received undergraduate degrees in physics (2004) and electronic engineering (2005) from the Universidad de los Andes in Bogotá, Colombia. He received his M.S. and Ph.D. degrees in physics under the supervision of Piet Martens and Dibyendu Nandy at Montana State University, in Bozeman, in 2008 and 2010, respectively. Muñoz‐Jaramillo is currently a Jack Eddy Postdoctoral Fellow at the Harvard‐Smithsonian Center for Astrophysics, Cambridge, Mass., hosted by Edward DeLuca. His research interests include the solar magnetic cycle; magnetohydrodynamics and dynamo theory; and space climate, global (paleo) climate, and long‐term solar evolution.

Absolute dimensions of eclipsing binaries

CONTEXT: Accurate physical properties of eclipsing stars provide important constraints on models of stellar structure and evolution, especially when combined with spectroscopic information on their chemical composition. Empirical calibrations of the data also lead to accurate mass and radius estimates for exoplanet host stars. Finally, accurate data for unusual stellar subtypes, such as Am stars, also help to unravel the cause(s) of their peculiarities. AIMS: We aim to determine the masses, radii, effective temperatures, detailed chemical composition and rotational speeds for the Am-type eclipsing binaries SW CMa (A4-5m) and HW CMa (A6m) and compare them with similar normal stars. METHODS: Accurate radial velocities from the Digital Speedometers of the Harvard-Smithsonian Center for Astrophysics were combined with previously published uvby photometry to determine precise physical parameters for the four stars. A detailed abundance analysis was performed from high-resolution spectra obtained with the Nordic Optical Telescope (La Palma). RESULTS: We find the masses of the (relatively evolved) stars in SW CMa to be 2.10 and 2.24 solar masses, with radii of 2.50 and 3.01 solar radii, while the (essentially zero-age) stars in HW CMa have masses of 1.72 and 1.78 solar masses, radii of 1.64 and 1.66 solar radii -- all with errors well below 2%. Detailed atmospheric abundances for one or both components were determined for 14 elements in SW CMa ([Fe/H] = +0.49/+0.61 dex) and 16 in HW CMa ([Fe/H] = +0.33/+0.32 dex); both abundance patterns are characteristic of metallic-line stars. Both systems are well fit by current stellar evolution models for assumed bulk abundances of [Fe/H] = +0.05 and +0.23, respectively ([alpha/Fe] = 0.0), and ages of about 700 Myr and 160 Myr.