Its been a good week for the Herschel-ATLAS survey that I work on – last Friday we released our first set of data to the public and this Friday we’re publishing some exciting results, led by Mattia Negrello from the Open University, on a new way to find cosmic lenses. Gravitational lensing occurs when light [...]... Read more »
Negrello, M., Hopwood, R., De Zotti, G., Cooray, A., Verma, A., Bock, J., Frayer, D., Gurwell, M., Omont, A., Neri, R.... (2010) The Detection of a Population of Submillimeter-Bright, Strongly Lensed Galaxies. Science, 330(6005), 800-804. DOI: 10.1126/science.1193420
When we look up into the sky at night, we see stars (even in London I can usually spot a few!). But there haven’t always been stars and galaxies in the universe. In a period known as the dark ages – not to be confused with the other dark ages – there was no light [...]... Read more »
M. D. Lehnert, N. P. H. Nesvadba, J. -G. Cuby, A. M. Swinbank, S. Morris, B. Clement, C. J. Evans, M. N. Bremer, & S. Basa. (2010) Spectroscopic confirmation of a galaxy at redshift z. Nature. arXiv: 1010.4312v1
A neutron star is made of neutrons, right? Astrophysicists ponder this question and forge theory after theory, but the only thing they conclude with certainty is that a neutron star by any other name would still be made of the densest form of matter know to exist in our Universe. Under certain conditions a star which has exhausted all of its fuel and is sufficiently massive will not be able to support its own weight with pressure support (as in a regular star) or with electron degeneracy support (as in a white dwarf) such that electrons and protons merge to form neutrons because it is a more energetically favorable arrangement of the matter. A neutron star is a sort of massive atomic nucleus, but without charge. The actual composition and detailed properties of neutron star are still theoretically uncertain.New measurements of the pulsating neutron star and helium-oxygen-carbon white dwarf binary system J1614-2230 reported in a Nature letter are the highest precision determinations of a neutron star's mass to date. The data comes from the massive Green Bank Telescope using the new Green Bank Ultimate Pulsar Processing instrument which accurately records the time of arrival of each radio pulse sent out by the rapidly rotating neutron star (which is a pulsar). The quality of this instrument, having over a tera op of computing power, and the size of the telescope, 100 meters, made this measurement possible. For a quick rundown of this result you can watch these quick movies on the scientific implications and the technology behind the discovery which were created by the NRAO.The analysis uses a general relativistic effect involving the time delay of light known as the Shapiro delay effect. When a light ray passes a massive object it follows a curved path. General relativity says that curvature of light rays can only take place when the velocity of the propagation of the light rays also varies with position. The Shapiro delay increases the light travel time through the curved space-time near a massive body. The equation to determine the time delay effect is delightfully simple.The delay depends on the mass, M, of the time delaying body between the source and the observer, the gravitational constant G, the speed of light, c, and the geometry of the system. The geometry is that light has to be passing near the gravitating body before it gets to the observer for the effect to occur at all so the vector that points from the observer to the source, R, and the vector that points from the observer to the gravitating mass are vital. Pulsar J1614-2230 is a nearly edge on, 89 degrees, system meaning that when the white dwarf passes in front of the pulsar during the binary orbit the Shapiro effect will be very strong. I ran a quick calculation of the time delay and found it to be exactly on the order of a few microseconds. The first figure in the paper shows the geometry and the measured effect.With this data in hand the standard Keplerian orbital parameters are calculated for this clean binary system and the masses of the objects are calculated. The mass of the neutron star was found to be 1.97 +/- 0.04 solar masses which is the most precise measurement of neutron star mass to date. Unfortunately this measurement technique does not provide any information about the radius of the neutron star, but because the mass was so high it already set a limit on the equation of state of the neutron star matter. This means that we can begin to answer what a neutron star is really made of. Different kinds of matter have a different behavior as you add more mass to them which is intuitive if you thought how discrepant with respect to size a planet made out of cotton candy versus rock would be. This result indicates that exotic models of hadronic matter including hyperons, kaon condensates are ruled out. Condensed quark matter is not ruled out, but highly constrained with this data. This is a big deal for particle physicists because this kind of system is an experiment that could never be carried out in a lab, but is necessary to probe fundamental physics.This cool result on neutron stars glosses over another application of precise pulsar measurements that the authors of this Nature paper regarded as noise. The plot above is very neat and clean, but before the data looks like that a timing analysis must take into account the time delays associated with many more mundane effects. Effects that change the time of arrival of the pulsar include the variations in the Euclidean distance between the Earth and the pulsar resulting from Earth’s orbital motion, the proper motion of the pulsar, and its binary motion, dispersive delays in the interstellar medium, and time dilation of clocks in the observatory and pulsar frames and along the propagation path. The Earth's orbital motion about the solar system barycenter (known as the Roemer delay) is up to 500 seconds and so must be removed from the data. The powerful thing is that the Earth's orbital motion tells us about the mass and orbits of all the bodies in our solar system. A paper published in the Astrophysical Journal states that with ten years of careful observation of 20 pulsars the masses and orbits of solar system bodies could be determined better than with any other method and even undiscovered trans-Neptunian objects could be found.Precise pulsar measurements are powerful. The first extrasolar planet ever discovered was actually made with pulsar measurements. Pulsars can tell us about the nature of neutron stars, the properties of own solar system, oh and even gravitational waves. If only astronomers had the money to build a pulsar timing array... ReferencesDemorest PB, Pennucci T, Ransom SM, Roberts MS, & Hessels JW (2010). A two-solar-mass neutron star measured using Shapiro delay. Nature, 467 (7319), 1081-3 PMID: 20981094D. J. Champion, G. B. Hobbs, R. N. Manchester, R. T. Edwards, D. C. Backer, M. Bailes, N. D. R. Bhat, S. Burke-Spolaor, W. Coles, P. B. Demorest, R. D. Ferdman, W. M. Folkner, A. W. Hotan, M. Kramer, A. N. Lommen, D. J. Nice, M. B. Purver, J. M. Sarkissian, I. H. Stairs, W. van Straten, J. P. W. Verbiest, & D. R. B. Yardley (2010). Measuring the mass of solar system planets using pulsar timing ApJ arXiv: 1008.3607v1... Read more »
Demorest PB, Pennucci T, Ransom SM, Roberts MS, & Hessels JW. (2010) A two-solar-mass neutron star measured using Shapiro delay. Nature, 467(7319), 1081-3. PMID: 20981094
D. J. Champion, G. B. Hobbs, R. N. Manchester, R. T. Edwards, D. C. Backer, M. Bailes, N. D. R. Bhat, S. Burke-Spolaor, W. Coles, P. B. Demorest.... (2010) Measuring the mass of solar system planets using pulsar timing. ApJ. arXiv: 1008.3607v1
Two weeks of news in one!
Astrophysics and Gravitation:
Did We Already Have the Data to Show Dark Matter Annihilation?
Dan Hooper, & Lisa Goodenough (2010). Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope arXiv arXiv: 1010.2752v1
Analyzing old data from the Fermi Gamma Ray Space Telescope, the authors have noticed gamma ray emissions consistent with predictions for a certain type of dark matter. Unfortunately, these things are never nice, clear problems where they’ve definitely seen dark matter or have definitely not seen it, but it’s an exciting collection of data points for astrophysicists who are on the dark matter hunt. It could turn out to be the evidence that people have been looking for, but it’s too early to say anything definitively.
For more, see Signs of Destroyed Dark Matter Found in Milky Way’s Core, Fermilab theorist sees dark matter evidence in public data.
Weighing Planets with Pulsars
Champion, D., et al. (2010). MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING The Astrophysical Journal, 720 (2) DOI: 10.1088/2041-8205/720/2/L201
What can’t pulsars do? The team, using an array of pulsars (PSRs J0437–4715, J1744–1134, J1857+0943, J1909–3744), have identified the masses of the planetary system from Mercury to Saturn, in agreement with the best-known masses determined by spacecraft and other observations. This new method relies on the incredibly predictable nature of pulsars and solar system ephemeris (the past and future positions of the Sun, Moon, and nine planets in three-dimensional space).
From the authors:
While spacecraft are likely to produce the most accurate measurements for individual solar system bodies, the pulsar technique is sensitive to planetary system masses and has the potential to provide the most accurate values of these masses for some planets.
For more, see A New Way to Weigh Planets.
A New Standard Candle?
Poznanski, D., Nugent, P., & Filippenko, A. (2010). TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED The Astrophysical Journal, 721 (2), 956-959 DOI: 10.1088/0004-637X/721/2/956
For years, Type Ia supernovae have been used as standard candles to measure cosmic distances; they were especially important for the measurements that determined that the expansion of the universe ws accelerating. Now, some astrophysicists are suggesting that for even higher accuracy, we use Type II supernovae as well. Initially, Type II supernovae weren’t used as standard candles because we weren’t as sure about their properties and actual brightness as we were for Type Ia supernovae. Using additional markers to gauge cosmic distances could help confirm and strengthen current observations, as well as discover inconsistencies.
Adam Burrows, astrophysicist at Princeton University:
It is unlikely that this technique will be able to compete with Ia, but it can contribute complementary cosmic information. It is coming into its own.
For more, see Alternative yardstick to measure the universe.
Dark Matter in the Sun, Revisited
Lopes, I., & Silk, J. (2010). Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun Science, 330 (6003), 462-462 DOI: 10.1126/science.1196564
After being gravitationally captured, low-mass cold dark-matter particles (mass range from 5 to ~50 x 109 electron volts) are thought to drift to the center of the Sun and affect its internal structure. Solar neutrinos provide a way to probe the physical processes occurring in the Sun’s core. Solar neutrino spectroscopy, in particular, is expected to measure the neutrino fluxes produced in nuclear reactions in the Sun. Here, we show how the presence of dark-matter particles inside the Sun will produce unique neutrino flux distributions in 7Be- and 8B-, as well as 13N-, 15O-, and 17F-.
Finally, a credible sounding experiment to test this dark-matter-in-the-sun-hypothesis, discover that there is no cold dark matter in the sun, and convince people to stop taking things seriously just because they technically “could” be possible. We’re not 100% sure of the consistency of the moon either, therefore I propose it’s full of anaerobic unicorns.
For more, see Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun.
New Oldest/Farthest Object in the Universe*
... Read more »
Dan Hooper, & Lisa Goodenough. (2010) Dark Matter Annihilation in The Galactic Center As Seen by the Fermi Gamma Ray Space Telescope. arXiv. arXiv: 1010.2752v1
Champion, D., Hobbs, G., Manchester, R., Edwards, R., Backer, D., Bailes, M., Bhat, N., Burke-Spolaor, S., Coles, W., Demorest, P.... (2010) MEASURING THE MASS OF SOLAR SYSTEM PLANETS USING PULSAR TIMING. The Astrophysical Journal, 720(2). DOI: 10.1088/2041-8205/720/2/L201
Poznanski, D., Nugent, P., & Filippenko, A. (2010) TYPE II-P SUPERNOVAE AS STANDARD CANDLES: THE SDSS-II SAMPLE REVISITED. The Astrophysical Journal, 721(2), 956-959. DOI: 10.1088/0004-637X/721/2/956
Lopes, I., & Silk, J. (2010) Neutrino Spectroscopy Can Probe the Dark Matter Content in the Sun. Science, 330(6003), 462-462. DOI: 10.1126/science.1196564
Lehnert, M., Nesvadba, N., Cuby, J., Swinbank, A., Morris, S., Clément, B., Evans, C., Bremer, M., & Basa, S. (2010) Spectroscopic confirmation of a galaxy at redshift z . Nature, 467(7318), 940-942. DOI: 10.1038/nature09462
Major, S. (2010) Shape in an atom of space: exploring quantum geometry phenomenology. Classical and Quantum Gravity, 27(22), 225012. DOI: 10.1088/0264-9381/27/22/225012
Sachdev, S. (2010) Holographic Metals and the Fractionalized Fermi Liquid. Physical Review Letters, 105(15). DOI: 10.1103/PhysRevLett.105.151602
Henrique Gomes, Sean Gryb, & Tim Koslowski. (2010) Einstein gravity as a 3D conformally invariant theory. arXiv. arXiv: 1010.2481v1
In the early 1970’s, Io, the innermost large moon of Jupiter, was somewhat of an enigma. Unlike Europa and Ganymede, it did not exhibit water ice adsorption bands it its IR spectra. Its density suggested that it was a rock and metal planet, but the surface reflectance was unlike anything known to science. This problem was addressed brilliantly in a Science paper by Fanale, Johnson, and Matson,... Read more »
Once upon a time there was a planet named Earth. It orbited exactly one astronomical unity away from a G2V type star. Billions of years went by and Earth found that it lived right in the habitable zone where liquid water was maintained on it surface and life spontaneously arose. Pretty soon life on Earth became restless, questioned its own existence, and looked for life on Gliese 581. Earthlings found many planets and exclaimed, 'Gliese 581 b is too hot, Gilese 581 c is slightly too hot, Gliese 581 d is slightly too cold, Gliese 581 e is way too hot, Gliese 581 f is too cold, but Gliese 581 g is just right!' so the story goes.Gliese 581 is an unassuming star: it is relativity close at 20 light years away (the 87th closest cataloged star to earth), it is only a third the mass of the sun, and it is relativity quiet in terms of stellar activity (which is beneficial for life because flares scorch planets). It is the sixth planet from Gliese 581 denoted merely as g that harbors so much potential. It is not to hot, not too cold, it is just right. It is the Goldilocks planet. Vogt et al. 2010 recently reported on the discovery of this planet which is a 3.1 Earth mass (or larger) planet orbiting in the habitable zone of the M3V type star Gliese 581. The problem is that this planet may not exist.The MediaI did not immediately discuss Gliese 581 here at The Astronomist because I wanted to read the paper before weighing in. However the authors were compelled to issue a press release about their findings before making their peer reviewed paper available. After I finally looked at the paper I was somewhat disappointed. The whole thing was a science journalism media circus. A selection of some of my favorite excerpts:“Found: An Earth like Planet, at Last” Time magazine“The chances of life on this planet are 100 percent,” Steven Vogt“Could contain more gold than we could ever imagine” PR Fire"Are the Gliesans going to Hell?" Huffington Post"An Alderaan Moment: Earth-Like planet disappears" Death+TaxesMedia coverage is a double edged sword for science. Scientists strive to come up with compelling results that often fall flat when presented to the media or public, but other stories make waves disproportionately large relative to their scientific impact. Arguably the discovery of an earth like planet should have been accompanied by a much larger amount of media attention. The misinformation spread about Gliese 581 g is a symptom of the real problem which is the science. This is not a confirmed planet detection, there is no evidence this planet has a hospitable atmosphere anything like Earth, and there is certainly no evidence of life. This wont stop the media from speculating or spreading dangerous misinformation (like the idea we could travel there if we trash Earth). The quote from Steven Vogt is an example of poor journalism where he prefaced the statement by saying, 'my own personal feeling is that the chances of life on this planet are 100 percent,' but the crucial context was thrown away for headlines.The ScienceAll the planets around Gliese 581 were discovered using the radial velocity technique. In any gravitationally bound system the bodies orbit their common center of mass. It is a subtle effect in a star-planet system where the central star dominates the mass. The central star will move at a characteristic speed depending on the orbits of the planets around it. The movement of the star is measured through the Doppler shift of the light emitted by the star. Modern instruments are super sensitive to even the smallest movements of stars down to as little as 1 m/s. Observations of the radial velocity of the star over a period of time (usually several years) is analyzed using Fourier analysis. The Fourier analysis identifies periodic signals in the data corresponding to the orbital period of the planet or planets.The researchers used two data sets spanning almost two decades. Most of the data came from the researcher's own instrument HIRES, and additional data came from a Swiss group with the HARPS instrument. The HIRES data spans a larger time range, but the HARPS data is more precise. This combined data set is how the researchers identified two new planets f and g.The ProblemsA little after this new Goldilocks planet was announced the Swiss group announced that they could find no evidence of Gliese 581 g in their data. Does this mean it doesn't exist? Well this is tricky. A planetary researcher in my department, Rory Barnes, spoke to the New York times before the Swiss group had spoke up and said that the planet looked like the 'real deal'. After the announcement was made I spoke to Barnes again and he said that he would have to hold off further judgment until more information was available. The onus of proof in science is upon those who make extraordinary claims. Vogt et al. were only able to find this planet by combing the available data sets; they actually state in their paper that they did not detect the planet in either of the data sets independently, only in combination. The damning part of the Swiss groups statement is that they say they have much more data available at this point that Vogt et al. did no have access to during their analysis. When the Swiss team forces planet g to fit their complete data they actually get a negative fit indicating that planet g really isn't there. The thing about this paper that I am least happy with is the quoted false alarm probability. The false alarm probability appears to be 1% based on the figures in the paper (see figure 3 specifically), but in the text it is quoted as ~10-5. I don't know what is going on.Then there is their error analysis (warning this is about to get technical feel free to skip this paragraph). Vogt et al. used the peaks in the power spectrum to identify the planets in the system then subtracted off the highest power modes corresponding to the planets they had found. The power spectrum for each planet carried with it a false alarm probability, but once the planet had been subtracted out of the power spectrum its false alarm probability was washed away (you can see this happening in figure 3). They compound their errors after the 1st, 2nd, 3rd, 4th, and 5th planets which have varying false alarm rates. The proper way to do this is a joint fit model to all planets in the system using Bayesian analysis.The strangest thing about all this is that when this paper was first submitted to The Astrophysical Journal the Swiss group was reviewing the paper and it was rejected. This Vogt paper meta chronicles its own history and discusses why it was retracted previously over concern of systematics. Unfortunatly the quality of the paper may not have improved. The Swiss group has actually leveled one specific concern, Vogt used perfectly circular orbits to find planet g, but the evidence shows the orbits are probably slightly elliptical. In fact in 2009 Vogt used elliptical orbits, but in this new paper circular orbits have been adopted. The image above illustrates this and makes a pictorial argument as to how circular vs elliptical orbits could introduce errors.The discovery of an Earth-like planet seems imminent. I do not know if this is it. I will hold off further judgment until more information was available.References:... Read more »
Steven S. Vogt, R. Paul Butler, Eugenio J. Rivera, Nader Haghighipour, Gregory W. Henry, . (2010) The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581. ApJ accepted. info:/arXiv: 1009.5733v1
The discovery of planet Gliese 581 g, an exoplanet just 3 times the mass of our Earth and located in its host star’s Habitable Zone, was one of the biggest science headlines of the year. The news broke, typically, somewhere between my observing proposal deadline and box number 15: “all the crap that didn’t fit [...]... Read more »
Steven S. Vogt, R. Paul Butler, Eugenio J. Rivera, Nader Haghighipour, Gregory W. Henry, & Michael H. Williamson. (2010) The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581. ApJ accepted. arXiv: 1009.5733v1
Back in January the Lincoln Near Earth Asteroid Research (LINEAR) survey saw something a bit odd amongst the asteroids in the main asteroid belt (found between Mars and Jupiter). Initially the mystery object, P/2010 A2, was designated as a main-belt comet (a rare object found within this region of the Solar System, unlike the majority [...]... Read more »
Jewitt, D., Weaver, H., Agarwal, J., Mutchler, M., & Drahus, M. (2010) A recent disruption of the main-belt asteroid P/2010 A2. Nature, 467(7317), 817-819. DOI: 10.1038/nature09456
Snodgrass, C., Tubiana, C., Vincent, J., Sierks, H., Hviid, S., Moissl, R., Boehnhardt, H., Barbieri, C., Koschny, D., Lamy, P.... (2010) A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2. Nature, 467(7317), 814-816. DOI: 10.1038/nature09453
Astrophysics and Gravitation:
Early Universe was Overheated, says NASA
Michael Shull, Kevin France, Charles Danforth, Britton Smith, & Jason Tumlinson (2010). Hubble/COS Observations of the Quasar HE 2347-4342: Probing the Epoch of He II Patchy Reionization at Redshifts z = 2.4-2.9 arXiv arXiv: 1008.2957v1
Credit: NASA/Michael Shull, University of Colorado
From the Press Release:
During a period of universal warming 11 billion years ago, quasars — the brilliant core of active galaxies — produced fierce radiation blasts that stunted the growth of some dwarf galaxies for approximately 500 million years. This important conclusion comes from a team of astronomers that used the new capabilities of NASA’s Hubble Space Telescope to probe the invisible, remote universe. The team’s results will be published in… The Astrophysical Journal.
For more, see Hubble Astronomers Uncover an Overheated Early Universe.
Dark Matter, Neutron Stars, and Strange Quark Matter, Oh My!
Perez-Garcia, M., Silk, J., & Stone, J. (2010). Dark Matter, Neutron Stars, and Strange Quark Matter Physical Review Letters, 105 (14) DOI: 10.1103/PhysRevLett.105.141101
We show that self-annihilating weakly interacting massive particle (WIMP) dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi-gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.
For more, see Does dark matter trigger strange stars?.
High Energy Physics and Particles:
Hey, this isn’t research news!
Yeah, it’s not… But, for anyone who will be in Manchester from October 23rd – 27th, 2010 should make sure they check out Super K Sonic Booooum!
This large installation consists of a 22 meter long ‘river’ of water running through a tunnel lined with thousands of silver balloons (photomultiplier tubes). Members of the public embark on a boat, pulled through the tunnel on a submerged track using a pulley system, with sound and lighting effects, and with an expert particle physicist navigator as a guide. On the journey they learn of neutrinos, their role in the Universe and how scientists detect them. All crew members must first don white Tyvek suits, wellies and hard hats or else face the wrath of Nelly the security chief, at the entrance of the tunnel. This installation is designed to deliver physically thrilling experiences; emerging the audience on a journey through the physics of the Universe.
Workshop on Sunday 24 October – 2pm – 4pm
Capture the Invisible: Craft and Science in particle physics.
In this workshop you will get the chance to make your own photomultiplier tube to capture the invisible in your own bedroom! Designed by Nelly Ben Hayoun in collaboration with Dr Jonathan Perkin, physicist and glassblower Jochen Holz
For more, see Super K Sonic Booooum.
SuperB Project Preparing for Construction!
SuperB Collaboration, E. Grauges et al., Francesco Forti, Blair N. Ratcliff, & David Aston (2010). SuperB Progress Reports — Detector arXiv arXiv: 1007.4241v1
It looks like funding for the SuperB Collaboration will come through and see the new experiment built in Frascati. I hope the Italians take this great opportunity to make many “flavour country” jokes.
From the press release:
The most elementary components of matter, quarks and leptons, have been found, as the result of 100 years of research, to be organized into three replicating “families”. The reason for this specific number or organization remains a full mystery. Flavor physics, the detailed understanding of the relationship between these families and the comparison between properties of matter and antimatter, is one of the most promising ways to explore new physics, quite complementary to the energy frontier research most notably pursued at the CERN LHC collider. Different kinds of new physics have different effects on rare decays of bottom and charmed quarks and of heavy tau leptons. These particles are all produced at SuperB in unparalleled abundance, making possible for the first time measurements of the precision required to be sensitive to the details of new physics uncovered at CERN.
For more, see SuperB project moves forward, preparing for construction.
Bonner Nuclear Lab to Study Quark-Gluon Plasma
Credit: Frank Geurts/Rice University
It was a good week to get funding for high-energy experiments.
From the Press Release:
Rice University’s Bonner Nuclear Lab has won a $1.175 million grant that will support its research on high-density and hot nuclear matter. Rice physicist Frank Geurts, who has spent his career looking for clues to the basic elements of the universe by smashing the nuclear contents of gold, lead and other heavy atoms, said the Department of Energy grant will facilitate his group’s transition from constructing and commissioning a highly complex detector system to using that machinery to do basic research.
Video: Quark gluon plasma (QGP)
For more, see Grant advances quark-gluon ... Read more »
Michael Shull, Kevin France, Charles Danforth, Britton Smith, & Jason Tumlinson. (2010) Hubble/COS Observations of the Quasar HE 2347-4342: Probing the Epoch of He II Patchy Reionization at Redshifts z . arXiv. arXiv: 1008.2957v1
Perez-Garcia, M., Silk, J., & Stone, J. (2010) Dark Matter, Neutron Stars, and Strange Quark Matter. Physical Review Letters, 105(14). DOI: 10.1103/PhysRevLett.105.141101
Gary Felder, & Stephanie Erickson. (2010) CurvedLand: An Applet for Illustrating Curved Geometry without Embedding. arXiv. arXiv: 1010.1426v1
Poltis, R., & Stojkovic, D. (2010) Can Primordial Magnetic Fields Seeded by Electroweak Strings Cause an Alignment of Quasar Axes on Cosmological Scales?. Physical Review Letters, 105(16). DOI: 10.1103/PhysRevLett.105.161301
Or at least so says a quartet of physicists who are certain that the flow of time has a 50% chance of ending in about 3.3 billion years because according to them, in a universe that expands infinitely, every unlikely event, as far as physics is concerned, will happen an infinite amount of times. Therefore, [...]... Read more »
Astronomers from the Carnegie Institution and the University of California, Santa Cruz, have discovered and earth-sized planet called Gilese 581. It's 20 light-years away, which makes it an unlikely traveling destination, but this is exciting news nonetheless. The abstract is enthusiastic yet cautions, saying that:"The estimated equilibrium temperature of GJ 581g is 228 K, placing it squarely in the middle of the habitable zone of the star and offering a very compelling case for a potentially habitable planet around a very nearby star."The press release is about the same, emphasizing the potential habitability of the planet, how hard it was to locate it and explains a bit about radial velocity. It more-or-less follows the rules I mentioned in a previous post. The news, however, say: "Odds of life on nearby planet '100 percent,' astronomer says." (Fox News and others).What went wrong? Where did the over-hyping come from? Unfortunately, Prof. Steven Vogt, one of the discoverers, told AP that "We don't have any direct way to sense that there's life there, my own personal opinion is that it is hard to imagine that life has not taken a foothold there."He also said: "Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it." It went downhill from there. So, we have a scientist hyping his findings, and media all-to-ready to hype it. The results are false (or at least unverified) headlines. (video: Steven Vogt talking to AP)Hat tip: Yoav Landsman (Hebrew)Vogt, S. S., Butler, P. R., Rivera, E. J., Haghighipour, N., Henry, G. W., & Williamson, M. H. (2010). The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581 Arxiv : 1009.5733v1... Read more »
Vogt, S. S., Butler, P. R., Rivera, E. J., Haghighipour, N., Henry, G. W., & Williamson, M. H. (2010) The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581. Arxiv. info:/1009.5733v1
Image via WikipediaPaschalidis et al. recently simulated what will happen when a white dwarf collides with a neutron star in a head on collision incorporating the effects of general relativity.
In each case I will list the mass of the white dwarf and neutron star in solar masses, (meaning the mass of these objects after dividing my the mass of the sun) the ratio of
... Read more »
Vasileios Paschalidis, Zachariah Etienne, Yuk Tung Liu, & Stuart L. Shapiro. (2010) Head-on collisions of binary white dwarf--neutron stars: Simulations in full general relativity. Submitted to PRD. arXiv: 1009.4932v1
Srednicki and Hartle have raised an interesting concern recently about a limitation on the predictive power of multiverse theories. They observe that in multiverse theories, exact snapshots of our universe happen several times in different places. So if we want to have a physical theory that describes our universe, the one we live in, then the question arises: how can we tell which one it is from
... Read more »
I know, I know, I switched back to writing these on Mondays again without telling anyone. It turns out, Wednesdays were a terrible choice of day for me. I swear I asked someone to fill in for me last week…
...but I guess she wasn't all that interested in the job.
Astrophysics and Gravitation:
Taking a Swim in the Lagoon Nebula
Credit: NASA/ESA Hubble Space Telescope
NASA and the ESA Hubble Space Telescope, via the Advanced Camera for Surveys, have provided us with a gorgeous picture of the Lagoon Nebula. This nebula is of particular interest to amateur astronomers because it is one of only a few of its kind actually visible with the naked eye from Earth. While it may be a blurry oval to the unassisted human viewer, to Hubble, this gas cloud is a giant, dynamic, home to new stars. Okay, so there isn’t any new physics here, but they did get a great image.
For more, see Breaking Waves in the Stellar Lagoon.
AGILE on Gamma Rays
Marisaldi, M., et al. (2010). Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes Physical Review Letters, 105 (12) DOI: 10.1103/PhysRevLett.105.128501
A team using satellite data to watch thunderstorms has figured out to to locate gamma rays (sometimes produced in said thunderstorms) with exceptional accuracy. These models are helping physicists understand gamma rays and how they relate to electrical storms (which most theories wouldn’t actually anticipate).
For more, see Pinpointing Earthly Gamma Rays.
ANITA on Cosmic Rays
S. Hoover, & et al. (2010). Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer Physical Review Letters arXiv: 1005.0035v2
A team using airborne radio detectors has noticed a characteristic radio wave signal produced by ultrahigh energy cosmic rays as they hit the ice in the Antarctic. Since we still don’t know where these ultrahigh energy particles come from, being able to track them once they hit the earth will be a useful tool in figuring out where they originated from.
For more, see Tuning In to Highest Energy Cosmic Rays.
So Long S-Process
A. J. Gallagher, S. G. Ryan, A. E. García Pérez, & W. Aoki (2010). The barium isotopic mixture for the metal-poor subgiant star HD140283 Astronomy and Astrophysics arXiv: 1008.3541v1
Snipet from the abstract:
Current theory regarding heavy element nucleosynthesis in metal-poor environments states that the r-process would be dominant. The star HD140283 has been the subject of debate after it appeared in some studies to be dominated by the s-process. We provide an independent measure… that observations and analysis do not validate currently accepted theory.
It’s another one of these fun astrophysics mysteries. We have a reasonable idea how stars work, but every now and then an observation comes along and tells us that our theoretical mechanisms can not be the end all be all of star dynamics and formation. Star HD140283 is another fun piece to contradictory puzzle. Because of the suspected age of HD140283 (ie. that it’s very, very old), it should have formed in its galaxy before the first red giants/barium producing stars formed, meaning that it shouldn’t (and according to current theory, couldn’t) have inherited any barium from its neighbours (and thus undergo r-process nucleosynthesis). However, Gallagher et al.’s team’s observations say otherwise (that instead, we see s-process nucleosynthesis). Is the current model of star formation incorrect, ie. do we need to rethink this late production of s-process isotope issue? Could there have been barium somehow to kick off this stars life? Could it be something else? Could that star have somehow been pulled in from an older galaxy? At this point, it seems pretty open.
For more, see Ancient star poses galactic puzzle.
High Energy Physics and Particles:
Good news, everyone! We might have been way off about quarks and gluons!
... Read more »
Marisaldi, M., Argan, A., Trois, A., Giuliani, A., Tavani, M., Labanti, C., Fuschino, F., Bulgarelli, A., Longo, F., Barbiellini, G.... (2010) Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes. Physical Review Letters, 105(12). DOI: 10.1103/PhysRevLett.105.128501
S. Hoover, & et al. (2010) Observation of Ultra-high-energy Cosmic Rays with the ANITA Balloon-borne Radio Interferometer. Physical Review Letters. arXiv: 1005.0035v2
A. J. Gallagher, S. G. Ryan, A. E. García Pérez, & W. Aoki. (2010) The barium isotopic mixture for the metal-poor subgiant star HD140283. Astronomy and Astrophysics. arXiv: 1008.3541v1
CMS Collaboration. (2010) Observation of Long-Range Near-Side Angular Correlations in Proton-Proton Collisions at the LHC. JHEP. arXiv: 1009.4122v1
Lehner, L., & Pretorius, F. (2010) Black Strings, Low Viscosity Fluids, and Violation of Cosmic Censorship. Physical Review Letters, 105(10). DOI: 10.1103/PhysRevLett.105.101102
I’m going to be upfront here: this post is about CCDs and readout electronics. Wait, come back, it’s going to be interesting I promise*. It involves the Hubble Space Telescope. Everyone likes that, don’t they? Many astronomical instruments, including the ones on Hubble, use Charge Coupled Devices or CCDs. These detectors are like containers for [...]... Read more »
Massey, R., Stoughton, C., Leauthaud, A., Rhodes, J., Koekemoer, A., Ellis, R., & Shaghoulian, E. (2010) Pixel-based correction for Charge Transfer Inefficiency in the Advanced Camera for Surveys . Monthly Notices of the Royal Astronomical Society, 401(1), 371-384. DOI: 10.1111/j.1365-2966.2009.15638.x
Richard Massey. (2010) Charge Transfer Inefficiency in the Hubble Space Telescope since Servicing Mission 4. MNRAS. arXiv: 1009.4335v1
I'm sure most of you have heard of the twin paradox "in which a twin makes a journey into space in a high-speed rocket and returns home to find he has aged less than his identical twin who stayed on Earth." This paradox has been worked out for special relativity in Minkowski spacetime. Recently, Boblest et al. worked out the details using general relativity for an expanding universe. (de Sitter
... Read more »
Gravitons are the particles that mediate the force of gravity in the analogous way that photons are responsible for the electro-magnetic field. And like photons, gravitons are thought to be massless. In fact, assuming general relativity is correct, the mass of the graviton has an upper bound of 7x10-32 eV which is really small. (See bold text at bottom.) However, for alternative gravity
... Read more »
Kejia Lee, Fredrick A. Jenet, Richard H. Price, Norbert Wex, & Michael Kramer. (2010) Detecting massive gravitons using pulsar timing arrays. Accepted by ApJ. arXiv: 1008.2561v2
Unlike with health and medicine press releases (Woloshin and Schwartz have a few good papers about the matter) I haven't seen much research about other scientific press release. That's why I was glad to find the paper "Credibility of science communication: An exploratory study of astronomy press releases" by Nielsen et al. (2007).They conducted 11 in-depth interviews with journalists, scientists and public information officers, and came up with several conclusions regarding the accuracy and credibility of astronomy press releases.Credibility was defined by the interviewees as "being honest and doing your homework." Hype was defined as overstating the importance of results in order to increase visibility. Credibility problems with press releasesProblems were usually caused by either the press release trying to make the issuing institution look better, or trying to make other institutions look worse. The level of communication effort: finding some well-known person to tell the media how much the research described in the press release is significant to science.The wording of the press release: even if it is possible you found alien life, keep that question mark at the end of "Alien life found?".Dictating the timing of a press release: we just happened to discover something really important, just in time for the annual budget meeting! Other time-related sins are publishing the press release before the peer-review paper is out, and timing the release to screw up the competition's own press release or event. Omission of reference to other scientists' work: this isn't the 17th century. It is hardly likely you did everything by yourself, or haven't built on some previous research.Unjust comparison with other facilities.Good ways to avoid lack of credibility (which can be in science, unlike in politics, problematic) is to have internal referees to the press release before its publication. Also, the importance of a peer-reviewed paper backing the press release can't be overstated.Despited everything said here, the authors' overall conclusion is that "...credibility problems for astronomy press release do not exist, though examples certainly exist." I find this conclusion very encouraging. Nielsen, L. H., Torpe Jørgensen, N., Jantzen, K., & Christensen, L. L. (2007). Credibility of science communication: An exploratory study of astronomy press releases Proceedings from the IAU/National Observatory of Athens/ESA/ESO Conference, Athens, Greece.... Read more »
Nielsen, L. H., Torpe Jørgensen, N., Jantzen, K., & Christensen, L. L. (2007) Credibility of science communication: An exploratory study of astronomy press releases. Proceedings from the IAU/National Observatory of Athens/ESA/ESO Conference, Athens, Greece. info:/
There are three neutrino species in the standard model, hereafter refereed to as 1, 2, and 3, that we know have mass from atmospheric and solar neutrino oscillation experiments. Furthermore, data from these experiments put constraints on the mass-splittings between these three neutrinos. From atmospheric experiments we know the mass differences between 2 and 3 is |M223| ~ 1.4x10-3 eV2 and from
... Read more »
Jimenez, R., Kitching, T., Peña-Garay, C., & Verde, L. (2010) Can we measure the neutrino mass hierarchy in the sky?. Journal of Cosmology and Astroparticle Physics, 2010(05), 35-35. DOI: 10.1088/1475-7516/2010/05/035
Astrophysics is not only a complicated discipline, but it’s becoming more and more esoteric, so much so that there seems to be an entire genre of deriving "groundbreaking papers" from obscure numerology, and the scientific community took a while to catch up with the Bogdanov brothers’ papers and show them to be just the sort [...]... Read more »
Do you write about peer-reviewed research in your blog? Use ResearchBlogging.org to make it easy for your readers — and others from around the world — to find your serious posts about academic research.
If you don't have a blog, you can still use our site to learn about fascinating developments in cutting-edge research from around the world.
Research Blogging is powered by SMG Technology.
To learn more, visit seedmediagroup.com.