In the OSTI Collections: Supernovae

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Article Acknowledgement:
Dr. William N. Watson, Physicist
DOE Office of Scientific and Technical Information

 

Theory and supernova behavior 

Observations and their implications

References

Research Organizations

Reports available through OSTI's SciTech Connect

Data sets accessible through OSTI's DOE Data Explorer

Additional References

 

 

 

Figure 1.  Supernova 1994D in the outskirts of the galaxy NGC 4526.  This example of a type Ia supernova shows that at peak brightness they rival the cores of galaxies in luminosity (Hubble Space Telescope photo).  (From "Visual Analytics for the Nearby Supernova Factory", available under the title "Sunfall: Visual Analytics for Astrophysics" at "Visualization Gallery from the Computational Research Division at Lawrence Berkeley National Laboratory"[DoE Data Explorer] through the DoE Data Explorer.)

 


The sun and the other stars produce their light and other radiation through one main mechanism. 

 

Like other sufficiently massive objects, a star is held together by the mutual gravitational attraction of all its particles for each other.  The gravitational attraction results in the star’s outer layers squeezing the atoms of the star’s core into less space than they’d take up otherwise, and heating them up. 

 

This heating alone would make stars somewhat luminous, but their cores generate even more radiation through an additional effect.  Generally, a stellar core’s atoms are squeezed to such a high density and temperature that the atoms’ nuclei constantly bang hard into each other.  If the core has enough of the right sort of nuclei, a small fraction of their collisions will end with the nuclei fusing together and releasing energy in the form of neutrinos and gamma rays.  Even though the fraction is small, the large number of nuclei and high collision frequency found in stars means that energy-releasing fusions constantly occur. 

 

Since matter is extremely transparent to neutrinos, almost all the neutrinos produced by fusion immediately escape through the star’s core and outer layers.  The gamma rays, on the other hand, don’t get through as easily.  They readily interact with the charged particles in the star, each gamma ray losing a different amount of energy as it collides with more or fewer charged particles with varying momenta on its way out.  By these collisions, the gamma rays exert an outward pressure on the star’s outer layers as they travel through them, eventually emerging with different energy losses as starlight, in every form from high-energy gamma rays, through lower-energy x-rays, ultraviolet light, visible light, infrared light, and microwaves, to the lowest-energy radio waves. 

 

Gravity’s contraction of the star’s outer layers is opposed by the core particles’ own resistance to being squeezed into less space, and by the outward pressure of the radiation released by the fusion that the outer layers’ inward pressure on the core produces in the first place.  A star can shine steadily while its core and outer layers’ opposing pressures remain in equilibrium for anywhere from millions to trillions of years, depending on the star’s mass, which determines the strength of the gravitational attraction and the resulting pressures.[Wikipedia]  But certain disruptions of the pressures’ equilibrium, such as the core running out of nuclei for energy-releasing fusion, or matter from outside the star accumulating on its outer layers, can redistribute the star’s mass to produce new energy-releasing reactions that make the star explode. 

 

Such explosions have been observed and recorded throughout human history as sudden changes in the brightness of nearby stars, some of which went from being too dim to see without a telescope to being conspicuous even in daytime.  One such star became visible in 1572, before the modern invention of the telescope, and was called a “nova” (Latin for “new”)[Wikipedia] by astronomer Tycho Brahe.  Whether a star ever becomes a “nova” depends greatly on its mass and what kind of atoms it forms from.  The most common novae explode powerfully enough that, at peak brightness, they shine several times as brightly as the sun.  But some extremely massive stars, like the one observed by Tycho, have a peak brightness billions of times as bright as the sun—as bright as an entire galaxy.  Stars that reach this state are known as “supernovae”. 

 

According to an abstract provided for a 2012 research report[SciTech Connect] from Princeton University,

 

Supernova explosions are the central events in astrophysics. They are the major agencies of change in the interstellar medium, driving star formation and the evolution of galaxies. Their gas remnants are the birthplaces of the cosmic rays. Such is their brightness that they can be used as standard candles to measure the size and geometry of the universe and their investigation draws on particle and nuclear physics, radiative transfer, kinetic theory, gravitational physics, thermodynamics, and the numerical arts. 

 

Because of the things we can learn from supernovae—not only about cosmic phenomena but, because of supernovae’s extreme physical conditions, about the elementary particles and interactions involved in all physical phenomena—astronomers now have the sky monitored for supernova explosions across the universe.  Although, on average, supernovae only occur every few decades in a large galaxy, finding one can be an everyday occurrence when today’s telescopes and high-throughput data processing are used to constantly scan tens of thousands of galaxies.  Some of the more recent results of these efforts are described in reports available through OSTI’s SciTech Connect and in data sets accessible through the DoE Data Explorer. 

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Theory and supernova behavior

 

Supernovae are roughly categorized into a few types and subtypes according to the frequencies of light waves they emit, which depend on the amounts of each chemical element they contain.  Those supernovae whose light shows little or no evidence of hydrogen are called type I and the rest are called type II.  Type I supernovae are subcategorized into those whose light indicates a relative abundance of silicon ions (type Ia), those without so much silicon but with plenty of neutral helium atoms (type Ib), and those without such obvious amounts of either element (type Ic). 

 

With increased knowledge, this categorization has come to seem somewhat superficial, since the process that triggers type Ia explosions appears to be different from the one that drives supernovae of types Ib, Ic, or II.  A supernova of one of these latter types is thought to originate when a star’s core runs out of enough fuel to sustain fusion and produce the radiation that holds the star’s outer layers up, so that the outer layers fall in.  If the outer layers rebound energetically enough from the core, a supernova explosion can result.  On the other hand, a type Ia supernova apparently results from matter accumulating from outside onto a white dwarf star[Wikipedia], which causes its interior temperature to rise enough to produce runaway fusion, thus explosively disrupting the star. 

 

Hypotheses about more precise details of these processes are worked out with computer simulations.  Calculations of what would happen in a supernova if particular hypotheses were true are compared with observations of real supernovae to see if the hypotheses hold up.  Calculations by different research groups emphasize different aspects of supernovae as well as different hypotheses about the same aspects. 

 





Figure 2.  Hydrodynamical simulation of two merging white dwarfs during their last few orbits.  The color scheme shows the logarithm of temperature through a slice of the orbital plane.  Boundary conditions on the equations describing the mass flow between the stars are set for a sphere surrounding the star on the left (cyan circle) and for a cone between the two stars (cyan wedge).  The white boxes with labels show the development of a standing shock (I); a region where shear from lower-density fluid pushing higher-density fluid leads to Rayleigh-Taylor instability [Wikipedia] (II); and the place where gravity changes sign and all wave modes become unstable (III).  (After the University of California at Santa Cruz report “Computational Astrophysics Consortium 3 - Supernovae, Gamma-Ray Bursts and Nucleosynthesis”[SciTech Connect], p. 14.) 

 

The density of the plasma (ionized gas)[Wikipedia] that stars are made of can vary greatly over short distances and can flow in a turbulent manner—something that simulations of supernovae, in particular, need to take into account.  Researchers at Los Alamos National Laboratory describe their incorporation of a mathematical model of turbulence to improve a computer program for simulating fluid flow in the report “Implementation and Validation of the BHR Turbulence Model in the FLAG Hydrocode”[SciTech Connect].  The hydrodynamics program is designed to simulate the kinds of flow that occur not only in supernovae, but in the earth’s atmosphere and in inertial confinement fusion[Wikipedia].  Experiments with the latter phenomenon reproduce the fusion reactions that occur in stars on a small scale on earth, but use a different means to confine the hot plasma long enough for the nuclei to be practically certain to fuse.  Atomic nuclei that fuse and release energy in the cores of stars are confined there by the star’s outer layers.  In inertial confinement experiments, a portion of a small volume of plasma is confined by its own inertia when the plasma’s outer layers, bombarded by lasers, suddenly heat up.  The hot outer layers, expanding further outward, recoil from the inner core of the plasma and thus squeeze that portion further inward, so that nuclei in the inner core collide and fuse.  The fluid flows within small inertial-confinement plasmas, the larger atmosphere of earth, and the very large plasmas of supernovae can all be turbulent, with the precise behavior of each affected by the turbulence.  The Los Alamos report describes details of how the hydrodynamics program represents the turbulence mathematically so that effects of the turbulence can be determined.  

 

Improved computer representations of other aspects of fluid flow have been developed by the SciDAC Computational Astrophysics Consortium, whose members included researchers at Princeton University and the University of California at Santa Cruz.  As noted in the abstract quoted above[SciTech Connect], the Princeton group set out to address supernova phenomena by more accurately simulating the relevant particle and nuclear processes, energy transfer by gamma rays and other forms of light, gravitational effects, and thermodynamics.  Supernovae were also among the phenomena modeled by the UC Santa Cruz group, along with gamma-ray bursts, processes (like stellar fusion) that synthesize larger atomic nuclei from smaller ones, and the evolution of stars generally.  The report on their work[SciTech Connect] notes that, along with such “secondary advances” as a better understanding of what are thought to be the earliest population of stars in the universe[Wikipedia] and of x-ray bursts from neutron stars[Wikipedia], the UC Santa Cruz group made major advances in understanding supernovae of all types, especially of type Ia. 

 


Figure 3.  From p. 12, “Computational Astrophysics Consortium 3 - Supernovae,
Gamma-Ray Bursts and Nucleosynthesis”[SciTech Connect]; caption there states that
this depicts a computer simulation of carbon-fusion deflagration in a star near the
end of burning, 1.21 seconds after ignition.  Red shows the interface between “ash” and “fuel”,
and light blue color indicates the star surface where density equals one million grams
per cubic centimeter.  (The density of liquid water is approximately one gram per
cubic centimeter.)  In this simulation the flame speed was set to 100 kilometers per second. 

 

Output from computer models of supernovae can be seen online.  Two sets of animations and simulations, “Supernova Simulations from the T-6 Group at Los Alamos National Laboratory (LANL)”[DoE Data Explorer] and “Stellar Evolution/Supernova Research Data Archives from the SciDAC Computational Astrophysics Consortium”[DoE Data Explorer], are available through the DoE Data Explorer.  Both sets of simulations include models of supernovae caused by collapse of a stellar core when it no longer emits enough radiation to support the star’s outer layers; the SciDAC simulations also include studies of cosmic gamma-ray bursts[OSTI Collections].  Both sets, however, also include simulations of Type Ia supernovae. 

 

Neutrinos commonly participate in nuclear interactions; as noted above, neutrinos are produced when nuclei fuse in stellar cores.  Matter is largely transparent to neutrinos, but not entirely.  Researchers at the University of Washington have used computer simulations to study neutrino interactions in supernovae as part of a collaboration of investigators at several institutions.  As they report in “Shedding New Light on Exploding Stars:  Terascale Simulations of Neutrino-Driven Supernovae and Their Nucleosynthesis”[SciTech Connect], their contributions include investigating the nuclear and neutrino physics governing rapid neutron captures by heavy nuclei that produce even heavier neutron-rich nuclei.  They have also explored the effects of new neutrino physics on the mechanism of supernova explosion, nucleosynthesis, and the detection on earth of neutrinos produced by supernovae.  A wider range of nuclear and neutrino physics studies was undertaken at the University of Arizona, which included investigations of processes that contribute to neutrino production in our atmosphere and neutrino signals of annihilation of dark matter in the sun.  These studies included the effects of previously uninvestigated neutrino interactions on the conversion of neutrinos from one type to another in supernovae and the role of new processes in stellar collapse.[SciTech Connect] 

 

The report “Spectra and Light Curves of Type Ia Supernovae for Probing Dark Energy”[SciTech Connect] from the University of Oklahoma describes supernova research that involves both computer modeling, in which the group’s 3-dimensional simulation software was advanced from test programs to full production programs, and the examination of several actual supernovae of different types, including type Ia.  The report consists of an introduction followed by copies of published papers and a slide presentation on various aspects of the work done.  Several of the papers deal with how the software simulates energy transfer by light within supernovae; other papers describe observations of real supernovae and what comparing the observations with computer models suggests about supernovae’s internal processes. 

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Observations and their implications

 

Type Ia supernovae are heavily emphasized in the aforementioned reports, and for good reason.  Not only do these supernovae seem to differ from the others in their triggering mechanism, but their differing light outputs appear to correlate strongly with easily observed features of their “light curves”—the graphs of how rapidly their luminosities rise and fall.  This makes them well suited for their role as “standard candles”—light sources whose intrinsic brightnesses are known—as was mentioned in the abstract to the Princeton University report quoted above.  Any light source looks dimmer, the farther away it is.  If the light source has a known intrinsic brightness, one can work out its distance by precisely measuring its apparent brightness, taking into account the additional dimming effect of any intervening matter.  Since the intrinsic light output of a type Ia supernovae is correlated with the time it takes after exploding to attain, and then fall from, its peak brightness, a comparison of the light curve with the apparent brightness is enough to estimate how far away the supernova explosion was.  Other variables also correlate with the light curve to lesser extents, so knowledge of those correlations can help astronomers refine their estimates of a Ia supernova’s distance. 

 

The most famous recent use of this type of information, “to measure the size and geometry of the universe”, was awarded the 2011 Nobel Prize in physics.[R&D Accomplishments]  The expansion of the universe had been discovered decades earlier, and its rate of expansion approximately measured, by relating the recession speeds of distant galaxies with their distances from us.  While other galaxies’ recession speeds are easily determined, since the faster they recede from us, the more their light waves are shifted toward lower frequencies (“redshifted”)[Wikipedia], it’s not as easy to determine how far away other galaxies are from our own galaxy.  But by the late 20th century, enough had been learned about type Ia supernovae and their light curves to determine their distances, and thus the distances to the galaxies they inhabit, with much greater precision.  A project to hunt for large numbers of type Ia supernovae and determine their distances from us was launched in order to measure how much the universe’s expansion rate has changed over time, which could be revealed by comparing the recession speeds of more distant galaxies (whose light was emitted longer ago) with the speeds of nearer galaxies.  It was expected that the expansion has slowed down over time because of the mutual gravitational attraction of all the matter in the universe.  Surprisingly, the expansion was found to have slowed down at first, but to have sped up afterward and to continue speeding up ever since.  This implies, according to the general theory of relativity, that most of the overall curvature of spacetime results from something that acts like a positive energy associated with a negative pressure—a so-called “dark energy”.[OSTI Collections] 

 

More precise information about the way that light curve parameters, intrinsic brightnesses, and other features of type Ia supernovae are interrelated should help us more accurately determine galactic distances and the overall dynamics of the universe.  Some of the papers included in the University of Oklahoma report describe new information of just this kind.  One paper in particular suggests that variations in a white dwarf star’s central density and carbon-to-oxygen profile can affect its light output when it becomes a supernova.  The carbon-to-oxygen profile and central density vary in turn, according to calculations, with the white dwarf’s original mass and pre-explosion mass accumulation rate, respectively.  Comparison with real light curves indicates that such variables may account for some type Ia features, but other variables are also involved. 

 

Other variables that affect the light curve have been sought in the character of the galaxies they form in.  Investigations of this by two groups, one at Lawrence Berkeley National Laboratory and one at Princeton University, are reported in “Type Ia Supernova Hubble Residuals and Host-Galaxy Properties”[SciTech Connect] and “Systematic Effects in Type-1a Supernovae Surveys from Host Galaxy Spectra”[SciTech Connect] respectively.  The Lawrence Berkeley group examined the relation between a new parameterization of actual Ia supernova light curves, how bright the supernovae were expected to be just from their recession speeds, and properties of the galaxies that the supernovae were found in.  They found that the galactic properties may account for some of the differences among type Ia supernovae.  Similarly, the Princeton group found “strong evidence for two distinct populations of supernovae, and correlations between the progenitor stellar populations and the nature of the supernova light curves.” 

 

Final reports for a project entitled “Discovering the Nature of Dark Energy:  Towards Better Distances from Type Ia Supernovae” were submitted by groups at Rutgers University[SciTech Connect] and the University of California, Berkeley[SciTech Connect].  The Rutgers report is essentially a bibliography of papers and presentations which that group contributed to during the project, but the Berkeley report describes that group’s accomplishments in more detail.  To make type Ia supernovae “more precise and more accurate distance indicators, and increase [their] power to elucidate the nature of dark energy”, the project’s original goals included understanding how dust in supernovae’s host galaxies affects their apparent brightness, identifying type Ia subsamples that give more precise and accurate distances, and using measurement of the light frequencies emitted by type Ia supernovae to quantify the evolution of their luminosity and constrain mathematical models of it.  The Berkeley group’s principal investigator described how these goals were exceeded, with particulars spelled out in synopses of the resulting published papers and in a summary of the project, which says in part: 

 

A major accomplishment was the publication of supernova (SN) rates derived from about a decade of operation of the Lick Observatory Supernova Search (LOSS) with the 0.76-meter Katzman Automatic Imaging Telescope (KAIT). We have determined the most accurate rates for SNe [supernovae] of different types in large, nearby galaxies in the present-day Universe, and these can be compared with SN rates far away (and hence long ago in the past) to set constraints on the types of stars that explode. Another major accomplishment was the publication of the light curves (brightness vs. time) of 165 SNe la, along with optical spectroscopy[Wikipedia] of many of these SNe as well as other SNe la, providing an extensive, homogeneous database for detailed studies. We have conducted intensive investigations of a number of individual SNe la, including quite unusual examples that allow us to probe the entire range of SN explosions and provide unique insights into these objects and the stars before they explode. My team’s studies have also led to the identification of subsamples of SNe la that can be used to provide the most reliable cosmological distances, and we developed ways to deal with the dust that makes SNe la appear fainter than they really are. Using the KAIT/LOSS sample, we produced an excellent Hubble diagram (galaxy recession speed vs. distance), accurately showing the expansion of the Universe.  Even smaller scatter was achieved when spectroscopic characteristics were taken into account. Another high-quality Hubble diagram was constructed with SNe la from the Sloan Digital Sky Survey (SDSS). These Hubble diagrams provide useful new constraints on the nature of the dark energy that is accelerating the expansion of the Universe. As an added bonus of our research, we also studied core-collapse SNe, which differ fundamentally from SNe la.  [Links added.—wnw]

 

Like many projects, the gathering of supernova data involves solving many problems, some extraordinary, some seemingly routine.  A very brief report from Yale University describes one of the smaller but significant problems in gathering data on nearby Ia supernovae at other observatories.  Here is the entirety of the text of  “High Statistics Study of Nearby Type 1a Supernovae. QUEST Camera Short Term Maintenance: Final Technical Report”[SciTech Connect]: 

 

The QUEST large area astronomical camera was installed at the prime focus of the Oschin Schmidt Telescope at the Palomar Observatory in California. The camera was used to carry out a survey of low redshift Type 1a supernovae which are the distance indicators used in the measurement of the expansion history of the universe and thus provided a method to study the nature of the recently discovered major component of our Universe that is commonly designated as Dark Energy, The camera had been in operation at this telescope since 2003. We anticipated another 5 or more years of operation of this survey. The camera thus needed some maintenance and minor upgrades to operate efficiently for the planned period of continued operation.

 

The purpose of this DOE grant was to perform short term maintenance on the QUEST camera. This work was completed in 2007-2008. The resulting camera was described in detail in C. Baltay et al PASP [Publications of the Astronomical Society of the Pacific] 119,1278, 2007.The maintenance and minor upgrades were successful: so much so that the camera is still operating efficiently in 2012. The funds awarded to this grant were fully utilized during this period.  [Link added.—wnw]

 

Data gathered by such means, combined with knowledge of the laws of physics, informs conclusions about processes ranging from the workings of supernovae themselves to the expansion of the universe.  The Nearby Supernova Factory collaboration, whose work has resulted in “an automated system consisting of specialized software and custom-built hardware that systematically searches the sky for new supernovae, screens potential candidates, then performs multiple spectral and photometric observations on each supernova”, is one group that makes their results available to supernova researchers world-wide for further study and analysis in a publicly accessible database.   This numeric data is available through the DoE Data Explorer at the page “Supernova Discoveries from the Nearby Supernova Factory (SNfactory)”[DoE Data Explorer]. 

 

As the SNfactory database’s description indicates, gathering raw telescope data is just one step toward various larger goals.  Afterwards, supernovae in the telescopic field of view have to be recognized and characterized.  Results of processing SNfactory data can be seen in the “Visualization Gallery from the Computational Research Division at Lawrence Berkeley National Laboratory”[DoE Data Explorer], also available through the DoE Data Explorer.  Particular gallery items related to SNfactory data are entitled “Sunfall: Visual Analytics for Astrophysics”, “Fast Contour Descriptor Algorithm for Supernova Image Classification”, and “Supernova Recognition Using Support Vector Machines”.  This gallery of data visualizations also contains animations derived from computer models of supernovae under titles like “Visualizing Type Ia Supernova Explosions”, “Buoyant Burning Bubbles in Type Ia Supernovae”, and “Computational Astrophysics”, as well as visualizations of several other phenomena from astrophysics.  The Gallery also has visualizations from entirely different fields of research. 

 


Figure 4.  “Supernovae are detected by subtracting a reference image from a new one to reveal the newly luminous object. Each such object becomes a supernova candidate. [In each row] the leftmost subimage is the “reference” or original subimage depicting a galaxy before the supernova explosion; the middle subimage is the “new” subimage taken after the supernova explosion; and the rightmost subimage is the resulting subtraction of the two, revealing the presence of the supernova. ... These subimages are then visually scanned by humans, a process that takes approximately 16 person-hours for each night’s data. ... All of these subimages were “passed” by the search software before our new roundness features were added.  [The second row] depicts a good candidate (note the compact circular form), but [the third and fourth rows] display bad subtractions which should have been culled out. After our algorithm had been implemented (features R1 and R2 added to the thresholded criteria), [the third row] failed the R1 cut and would not have been passed for human scanning. [The fourth row] failed the R2 cut and likewise would not have been passed.”  (From "A fast contour descriptor algorithm for supernova image classification", available under that title at "Visualization Gallery from the Computational Research Division at Lawrence Berkeley National Laboratory"[DoE Data Explorer] through the DoE Data Explorer.)

  

 

 

The particular larger goal of determining the nature of what accelerates the universe’s expansion is addressed in a 2009 paper listed in the Rutgers bibliography mentioned above.  This report, “Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves”[SciTech Connect], describes how authors from Rutgers, Harvard University, the Harvard-Smithsonian Center for Astrophysics, the University of Pittsburgh, the European Southern Observatory, Stanford University’s Kavli Institute for Particle Astrophysics and Cosmology, and the Cerro Tololo Inter-American Observatory in Chile combined data from several sets of type-Ia supernova observations and determined their implications for how a dark energy’s pressure should relate to its density.  The data available at the time were consistent with the pressure and density being in a ratio of (-1) to (+1) that wasn’t varying rapidly, though the authors noted that large numbers of very distant Ia supernovae were needed to provide much information about whether this ratio has varied over the long term.  Random variations in supernova characteristics produce uncertainties in the calculated value of the dark energy’s pressure/density ratio, but so do systematic uncertainties, such as the accuracy of supernova luminosity measurements, differences between supernova distances calculated from measurements of their own luminosity and their galaxies’ recession speeds, how much the color of light received from a supernova is affected by the supernova itself and by absorption of light by the galaxy it’s in, and whether different populations of type-Ia supernovae could have different luminosities but the same light curves.  Increasing the number of observed Ia supernovae should help reduce both the random and systematic uncertainties in the calculation of dark-energy properties and the universe’s past and projected expansion.*

 

Deductions about the expansion rate of the universe are made by accounting for observed features of supernovae and other entities in terms of Einstein’s general theory of relativity.  In  the last century, general relativity has proven to accurately describe many different astrophysical phenomena, from the effects of gravity on starlight to the behavior of orbiting clocks on which location systems like GPS[Wikipedia] are based.  However, it’s not clear how to combine the use of general relativity and the similarly-verified quantum theory to analyze physical processes that involve phenomena for which both theories should be relevant.  Various attempts have been made, however, to construct theories that accurately describe such phenomena but still agree with ordinary quantum theory and relativity descriptions where those descriptions are known to be accurate.  Several theories propose to account for the weakness of gravitation compared to other basic interactions by postulating the existence of additional dimensions besides the ordinary four of spacetime.  One such theory implies that supernovae formed after stellar-core collapse should produce massive quanta of gravitational interaction somewhat like the photons, W and Z particles, and gluons that mediate electromagnetic interactions, weak interactions, and strong interactions respectively; if the collapsed core becomes a neutron star, the gravitational quanta should be trapped in its gravitational field.  This theory also implies that if these quanta exist, they should have a half-life on the order of billions of years, and that their decay should produce a measurable flux of gamma rays.  These implications are described in a dissertation (“Search for Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT”[SciTech Connect]) by Bijan Berenji of Stanford University and the SLAC National Accelerator Laboratory.  The dissertation describes how new neutron-star observations, made with the main instrument of the Fermi Gamma-ray Space Telescope[Wikipedia], logically narrow the range of possibilities of the extra dimensions’ extent and shape. 

 

__

* This report was also described in the aforementioned OSTI Collections article on dark matter and dark energy[OSTI Collections]  more briefly—and erroneously.  As originally posted, the article indicated that the larger data set improved calculations of the universe’s expansion rate by reducing the effect of random galactic motions rather than the variations and uncertainties listed above.  The dark matter/dark energy article has been rewritten to correct the error.—wnw

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References

 

Wikipedia

 

Research Organizations

 

Reports available through OSTI’s SciTech Connect

  • “Final Report:  SciDAC Computational Astrophysics Consortium (at Princeton University)” [Metadata]
  • “Implementation and Validation of the BHR Turbulence Model in the FLAG Hydrocode” [Metadata]
  • “Computational Astrophysics Consortium 3 - Supernovae, Gamma-Ray Bursts and Nucleosynthesis” [Metadata]
  • “Shedding New Light on Exploding Stars:  Terascale Simulations of Neutrino-Driven Supernovae and Their Nucleosynthesis” [Metadata]
  • “Final Technical Report for University of Arizona Grant:  Research in Theoretical Nuclear and Neutrino Physics” [Metadata]
  • “Spectra and Light Curves of Type Ia Supernovae for Probing Dark Energy” [Metadata]
  • “Type Ia Supernova Hubble Residuals and Host-Galaxy Properties” [Metadata]
  • “Systematic Effects in Type-1a Supernovae Surveys from Host Galaxy Spectra” [Metadata]
  • “Final Technical Report: Discovering the Nature of Dark Energy: Towards Better Distances from Type Ia Supernovae” (from Rutgers University) [Metadata]
  • “Discovering the Nature of Dark Energy: Towards Better Distances from Type Ia Supernovae -- Final Technical Report” (from the University of California, Berkeley) [Metadata]
  • “High Statistics Study of Nearby Type 1a Supernovae. QUEST Camera Short Term Maintenance: Final Technical Report” [Metadata]
  • “Improved Dark Energy Constraints From ~ 100 New CfA Supernova Type Ia Light Curves” [Metadata]
  • “Search for Large Extra Dimensions Based on Observations of Neutron Stars with the Fermi-LAT” [Metadata]

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Data sets accessible through the DoE Data Explorer

  • “Supernova Simulations from the T-6 Group at Los Alamos National Laboratory (LANL)” [Metadata]
  • “Stellar Evolution/Supernova Research Data Archives from the SciDAC Computational Astrophysics Consortium” [Metadata]
  • “Supernova Discoveries from the Nearby Supernova Factory (SNfactory)” [Metadata]
  • “Visualization Gallery from the Computational Research Division at Lawrence Berkeley National Laboratory” [Metadata]

 

Additional references

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Last updated on Wednesday 27 July 2016