Fusion is only 50 years away and it will solve all of the worlds energy problems. That is the good news. The bad news is that it has been 50 years away for the last 50 years. If that situation is maddening to you then you are not alone. Leonardo Mascheroni, a retired Los Alamos National Laboratory physicist, wanted funding to build a colossal laser for producing energy from fusion and was willing to trade the United States' nuclear weapons secrets to realize his dream. Mascheroni was recently indicted on charges of treason concerning selling nuclear arms secrets and is awaiting trial sometime this year. In the meantime the United States is pressing forward with a completely separate laser fusion project called the National Ignition Facility or the NIF which uses 192 lasers fired in unison to recreate the energy source of the stars harnessed on Earth.In this post I am going to talk about the basics of fusion and the NIF. I also have questions and answers with a physicist on the project, Siegfried Glenzer, at the end of the post. I asked him some hard questions not just about the science, but also about the politics going on around the project. Physicists would like their experiments and budgets to work in a vacuum, but alas they never are. I deeply thank doctor Glenzer for answering my questions. What is fusion?Fusion is the joining of two or more separate atomic nuclei into a larger nuclei. Fusion can create energy because the mass of the input and output nuclei are not necessarily equal in mass. Specifically, if the mass of the output nuclei is less than the total mass of the input nuclei then the mass difference is made up by the production of energy as Einstein taught us E=mc2 (conversely if the output nuclei are more in total mass than the input nuclei then the reaction would consume energy). In particular, stars like our Sun fuse lighter elements into heavier elements up until the point the star is attempting fusion of iron which does not produce energy because iron has the largest binding energy per nucleon. Actually fusion processes in stars normally involve several intermediate nuclei or elements. The most important process for our Sun is the proton-proton chain which fuses four hydrogen nuclei, 11H, to form a single helium nuclei 42He with a mass difference of ΔM. Einstein's mass energy relation shows us how much energy this process releases.4 ⋅ 11H -42He = ΔMΔM c2 ≈ 27 MeVThe key to joining two nuclei together is overcoming the repulsive electric Coulomb force between nuclei. The positive charge on nuclei repel each other until the two nuclei actually meet and then the attractive short range strong nuclear force takes over to bind the two nuclei into new larger nuclei. The fewer the number of protons in the nuclei the easier it is to fuse. The repulsive force between nuclei may be overcome in several ways. Inside stars heat and pressure, which comes from the stars gravitational contraction, occasionally forces two nuclei close enough together for them to fuse and all together the star burns consistently for a very long time. The more massive the star the hotter and denser it is at the center so larger nuclei can be fused. The production of heavier elements by stars fusing hydrogen is essentially the origin of all elements heavier than lithium; massive stars occasionally explode, and thus we are all made of stardust. The input elements for the first fusion reactors will be the hydrogen isotopes of deuterium (H with a neutron) and tritium (H with two neutrons) because this reaction has the highest nuclear cross section and high energy yield.Why is fusion important?Fusion is very important; this is the kind of physics that future presidents should understand. In this post I am focusing on the basics of fusion and the prospects for the National Ignition Facility and a in a future post I will talk about another project known as ITER. I should clarify that there are effectively many different kinds of fusion machines and an important distinction is net energy positive and net energy negative machines. The ratio of fusion power to input power (often denoted Q in the field) must be positive to have a viable energy solution. There exist at this moment very many fusion machines which take more input power than they make in output power (they have a fractional Q value). Some of the current machines seem fantastic like 'table top' pyroelectric fusion devices, but the reality is that they take energy to run and have no foreseeable future in the energy game. These devices play a role as portable neutron generators in labs for various research purposes or in security as nuclear material detectors. Net energy positive machines have not yet been invented. The NIF will not produce energy, but will be a testbed for fusion technologies. The fusion technology goal is the sustainable production of energy from abundant raw elements such as hydrogen, helium, or related isotopes (Helium 3, deuterium, tritium). Fusion using these light elements is cheap, safe, and green. Fusion is cheap (however the technology development is expensive!) because the raw elements like hydrogen are abundant, further as a consequence of this virtually infinite supply (one in every 6,500 atoms on Earth is a deuterium atom) it can be considered a renewable energy. Fusion is safe because when a fusion nuclear reactor malfunctions unlike a fission nuclear reactor the reaction will snuff itself out rather than proceed uncontrollably to the point of a thermonuclear explosion. Finally, fusion is green or environmentally friendly because it produces no climate altering products.There are so many reasons fusion is important. Fusion is the future. It is the next step in humanity's technological evolution. This video from the BBC Horizons series with physicist Brian Cox gives a cursory look at the NIF, and puts the entire endeavor into perspective (and to boot in finishes with The Kinks This Time Tomorrow which has the most appropriate lyrics ever).How do we use fusion to make energy?Under the correct conditions of incredibly high density, pressure, and temperature a self sustaining fusion process can occur. These conditions are of course exactly what you find at the center of a star, but on Earth these conditions are engineered via the use of confinement and heating mechanisms. The NIF will use a symphony of lasers to simultaneously heat and compress a pellet of deuterium and tritium to simulate the conditions inside of a star. A deuterium and tritium target has been chosen for this first experiment because the fusion cross section between deuterons and tritons is three orders of magnitude larger than for any other atoms. Other fusion projects like ITER will use a toroidal (or doughnut shaped) chamber known as a tokamak to confine a deuterium and tritium plasma which is then heated through magnetic field confinement or radio frequency heating kind of like a big nuclear microwave. Once the fusion process is begun radiation and fast neutrons will be emitted which will be absorbed by the walls of the machine in order to gather heat to drive a steam-turbine generator to produce electricity pretty much just like every power plant.How does NIF work?It all starts with a single primordial laser source with very low power which is slightly preamplified and split into 48 parts. These pulses are then amplified by a factor of 10 billion in another set of preamplifiers then they are split into 192 parts and sent to the main amplifier. Then electrical energy stored in capacitors is dumped into 7680 xenon flashtubes which operate pretty much like the flash on your camera, except they are over 6 feet tall and take 30 kilojoules of input power each. The bright incoherent full spectrum light from the flashtubes passes through Neodymium doped glass and in a stupendously inefficient process amplifies the laser beams. The lasers bounce back and fourth a few times and finally go through the amplifier and the main optics system again before heading to the target chamber. At this point the primordial laser has been amplified by a factor of 1015 (in the video below he says quadrillion which apparently doesn't even have an agreed upon meaning, I think 1015 is right). The beams trave... Read more »
Glenzer, S., MacGowan, B., Michel, P., Meezan, N., Suter, L., Dixit, S., Kline, J., Kyrala, G., Bradley, D., Callahan, D.... (2010) Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies. Science, 327(5970), 1228-1231. DOI: 10.1126/science.1185634
The authors and editor knew exactly what they were doing with this one:... Read more »
You might not be able to tell from wherever you are reading this, but black holes in the distant universe just shrunk down to as little as a tenth of their previous size. This is not some cosmic disappearing act; … Continue reading →... Read more »
Kollatschny, W., & Zetzl, M. (2011) Broad-line active galactic nuclei rotate faster than narrow-line ones. Nature, 470(7334), 366-368. DOI: 10.1038/nature09761
Supermassive black hole in a type of galaxy where nobody expected to find one? Henize 2-10 is a small, mostly unremarkable compact dwarf galaxy. Its estimated dynamical mass is about 1010 M⊙, only a few percent of our galaxy's mass, and its distance from us is about 30 million light years. It is irregular in shape and does not fit in any category of the standard Hubble sequence.The only respect in which Henize 2-10 has attracted attention – for several decades – before now is an extremely high rate of star formation in comparison to its size. The rate is 10 times that of the Large Magellanic Cloud, a satellite galaxy of the Milky Way that is also irregular in form and has approximately the mass of Henize 2-10.This research – An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10 – recently published Nature, now offers good evidence that at the center of Henize 2-10 is an active black hole of substantial but somewhat uncertain mass between 2×105 M⊙ and 2×107 M⊙. That's a lot – it could exceed the mass of the Milky Way's black hole, ~4.2× 106 M⊙.The evidence presented that Henize 2-10 contains an actively accreting massive black hole is pretty good. It includes detection of radio emissions with a substantial non-thermal component. In other words, much of the radio emissions is due to something besides black body radiation – perhaps synchrotron radiation typical in active black hole jets. There is also a point source of high-energy X-ray emissions coming from the same location as the radio emissions. The evidence that these emissions are due to an active black hole isn't perfect. In particular, long-baseline interferometry shows gaps in the radio source, and the radio spectrum does not have the shape of a typical radio galaxy's. But consideration of other possible explanations indicates that the alternatives are rather improbable.However, the paper concludes "the massive black hole in Henize 2-10 does not appear to be associated with a bulge, a nuclear star cluster or any other well-defined nucleus. This unusual property may reflect an early phase of black-hole growth and galaxy evolution that has not been previously observed. If so, this implies that primordial seed black holes could have pre-dated their eventual dwellings."The authors are implying that this black hole could have existed before Henize 2-10 itself. And further, since galaxies in the very early universe (z≥7) have many similarities to Henize 2-10 (as well as certain differences), that many of these very early galaxies could also have formed around pre-existing massive black holes.These concluding observations should, on the basis of the evidence provided, be regarded as rather speculative. There are substantial logical gaps in the reasoning. For one thing, Henize 2-10 is pretty unusual based on its high rate of star formation. This implies an unusual and probably chaotic recent history. And so there really isn't much solid reason to think that the central black hole predated the galaxy.How closely Henize 2-10 resembles very early galaxies is also open to question. The earliest stars, which made up the earliest galaxies, had very low metallicity and therefore tended to be much larger, brighter, and short-lived than stars forming in the present era. The assumption that galaxy evolution would be pretty similar between now and then is hard to make.Some of the popular media accounts go even further and suggest that "most" galaxies probably formed around pre-existing black holes. Even if that were true for Henize 2-10, all that can legitimately be inferred is the possibility, not the necessity, of that circumstance in most cases. There have been reports of the existence of supermassive black holes in galaxies without central bulges (not just irregular galaxies) – here, for example. There have even been studies of active black holes in the early universe that may have predated their galaxies, one of which I wrote about in this article: Which came first - the galaxy or the black hole?. There are also cases of fairly normal galaxies, such as M33, that seem to have at most a very small central black hole – see here.So it's certainly a very real issue whether, at least in some cases, central black holes form before their galaxies, but the present study is just another interesting data point, not the last word on the subject.Reines, A., Sivakoff, G., Johnson, K., & Brogan, C. (2011). An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10 Nature, 470 (7332), 66-68 DOI: 10.1038/nature09724Further reading:Dwarf Galaxy Harbors Supermassive Black Hole – 1/9/11Ginormous Black Hole May Solve Longstanding Mystery – 1/9/11Baby Galaxy Hosts Monster Black Hole – 1/10/11Astronomers Discover Supermassive Black Hole in Center of Tiny Galaxy – 1/9/11Supermassive Black Hole Peeks From Behind The Skirt Of A Dwarf Galaxy – 1/10/11Huge Black Hole Found in Dwarf Galaxy – 1/10/11Henize 2-10: A Surprisingly Close Look at the Early Cosmos – 1/10/11A Black Hole “Too Big” For Its Galaxy – 1/12/11Supersized Black Hole Seen in Small Galaxy – 1/11/11Dwarf galaxy solves supermassive mystery – 1/10/11Dwarf galaxy hides a cosmic 'Little Big Man' – 1/10/11New Evidence Shows Black Hole Growth Preceding Galactic Formation – 1/9/11A tiny galaxy that hides a big secret – 1/11/11Itty Bitty Galaxy Home to Gargantuan Supermassive Black Hole – 1/11/11... Read more »
Reines, A., Sivakoff, G., Johnson, K., & Brogan, C. (2011) An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10. Nature, 470(7332), 66-68. DOI: 10.1038/nature09724
Typically it takes quite a few months before a submitted article in nature has passed the peer review process and has been accepted – and then until it is actually printed, it usually takes even more then a quarter of … Continue reading →... Read more »
Lissauer JJ, Fabrycky DC, Ford EB, Borucki WJ, Fressin F, Marcy GW, Orosz JA, Rowe JF, Torres G, Welsh WF.... (2011) A closely packed system of low-mass, low-density planets transiting Kepler-11. Nature, 470(7332), 53-8. PMID: 21293371
In light of the recent solar flare, here's a breakdown of the radiation we're exposed to, how we're shielded, and how solar flares can actually protect our astronauts.... Read more »
B. F. Rauch, J. T. Link, K. Lodders, M. H. Israel, L. M. Barbier, W. R. Binns, E. R. Christian, J. R. Cummings, G. A. de Nolfo, S. Geier, R. A. Mewaldt, J. W. Mitchell, S. M. Schindler, L. M. Scott, E. C. Stone, R. E. Streitmatter, C. J. Waddington, M. E. (2009) Cosmic-ray origin in OB associations and preferential acceleration of refractory elements: Evidence from abundances of elements 26Fe through 34Se. Astrophys.J.697:2083-2088,2009. info:/arXiv:0906.2021v1
Svensmark, H., Bondo, T., & Svensmark, J. (2009) Cosmic ray decreases affect atmospheric aerosols and clouds. Geophysical Research Letters, 36(15). DOI: 10.1029/2009GL038429
I’ve previously blogged about extreme particle acceleration producing gamma-rays in many different astrophysical contexts, including galactic binary systems & blazars, but I haven’t talked in any great depth about another source of extremely high energy particles: supernova remnants. The Crab Nebula: a typical supernova remnant (Image: NASA/STScI) A supernova remnant is the remains of a [...]... Read more »
Globular Clusters (GCs) Globular clusters are groups of roughly spherical, densely packed stars. They are thought to have formed at the same time as most galaxies and the stars which make them up are some of the oldest known–thus GCs are an excellent probe of galaxy formation and evolution. They have a high central stellar [...]... Read more »
A. P. Huxor, A. M. N. Ferguson, N. R. Tanvir, M. J. Irwin, A. D. Mackey, R. A. Ibata, T. Bridges, S. C. Chapman, & G. F. Lewis. (2011) Exploring the Properties of the M31 Halo Globular Cluster System. MNRAS. arXiv: 1102.0403v1
Abadi, M., Navarro, J., & Steinmetz, M. (2006) Stars beyond galaxies: the origin of extended luminous haloes around galaxies. Monthly Notices of the Royal Astronomical Society, 365(3), 747-758. DOI: 10.1111/j.1365-2966.2005.09789.x
Galaxy clusters are some of the largest structures in the universe. Astronomers have found these clusters, which are large groups of galaxies bound together by gravity, as far back as only 4 billion years after the Big Bang (less than … Continue reading →... Read more »
Capak PL, Riechers D, Scoville NZ, Carilli C, Cox P, Neri R, Robertson B, Salvato M, Schinnerer E, Yan L.... (2011) A massive protocluster of galaxies at a redshift of z ≈ 5.3. Nature, 470(7333), 233-5. PMID: 21228776
Its the 14th of February, or at least thats what the calendar on the wall says, you have been out in deep space heading towards that new colony for so long each day pretty much blurs in to the next. Despite how cold it is outside (and believe me its cold), today is a day [...]... Read more »
Tore Straume, Steve Blattnig, & Cary Zeitlin. (210) Radiation Hazards and the Colonization of Mars: Brain, Body, Pregnancy, In-Utero Development, Cardio, Cancer, Degeneration. Journal of Cosmology, 3992-4033. info:/
Frame Dragging, an effect spinning black holes have on spacetime and on the light in its vicinity, is causing a measurable corkscrew effect on photons, newly discovered and published in this issue of Nature Physics. "Twisting of light around rotating black holes"... Read more »
QFT I’m lucky to have a job in which I can take two weeks of mornings of work to study a nominally tangential subject in greater depth. These past two weeks I attended a series of lectures at the ETH on physics beyond the standard model, the first week was very technical but exciting to [...]... Read more »
F. I. Cooperstock, & S. Tieu. (2005) General Relativity Resolves Galactic Rotation Without Exotic Dark Matter. arXiv. arXiv: astro-ph/0507619v1
he research into the nature and properties of the black hole at the centre of the Milky Way galaxy is one of the highlights of astronomical discovery of the last two decades. Using the biggest telescopes on the planet and state of the art observing technology, we’ve been able to track the young massive stars that are whizzing around the black hole in a dense cluster, and shown with a high level of certainty that the galaxy’s central object really is a supermassive black hole, referred to as Sagittarius A*. Using these stellar orbits, we’ve also determined its mass – 4 million solar masses.... Read more »
F. H. Vincent, T. Paumard, G. Perrin, L. Mugnier, F. Eisenhauer, & S. Gillessen. (2011) Performance of astrometric detection of a hotspot orbiting on the innermost stable circular orbit of the galactic centre black hole. MNRAS. arXiv: 1011.5439v1
Ariel Goobar and Bruno Leibundgu have recently submitted an article to Annual Review of Nuclear and Particle Science summing up our current understanding of physics from the current set of supernova data. We have accrued quite a lot of supernova data over the years and so it is interesting to take a look at how much we have learned. I will not report everything but will post a few interesting
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In continuing this review and analysis of the film 'Knowing', we must absolutely address the numeric sequence which was obsessively scribed by the character Lucinda Embry. The sheet of paper containing several hundred seemingly random digits was placed into an elementary school's 'time capsule' to be opened some 50 years later. Upon opening and rediscovery of this number sequence, we are taken on a thrilling journey to unlock the secrets embedded in this sequence of digits - which as interpreted - is a key to a deterministic (see Part 1) past, present, and future existence (or rather destruction).
Codes, symbols, and translative indices have been among those most controversial topics throughout history. Science has uncovered factual significance with several coded objects - and yet an equal number of conspiracies have evolved from them. This is largely given that the historical knowledge gap is so broad and left wide open for interpretation - wildly imaginative interpretation in many cases.
With 2012 around the corner, this topic has been right out there in the mainstream public eye, and in full force. We frequently hear about deep and dark conspiracies associated with things like the Dresden Codex, Nostradamus, Georgia Guidestones, the Rosetta Stone, and even the Bible. All of this is truly fascinating, but one can only hope that some hard science comes from their interpretations to help us narrow that broad knowledge gap out there and help us progress somewhat constructively rather than wallowing away in front of the tv thinking that the world is coming to an end!
In 'Knowing', the codex that we are presented with is a number sequence. This is unique from those previously listed as numbers are considered a universal mode of communication, as opposed to communicating in a specific language. In fact, count systems have been discovered that may be as early as 35,000 years old, making numbers the oldest known mode of written communication. Lucinda, in her extra-terrestrial state of possession, communicated in numbers to allow her message of Earthly disasters to be understood by anyone in the future - any race, any language, any age, and possibly even on any other intelligent planet.
It is not too far fetched to send numeric messages into the future for this very purpose. In fact, Carl Sagan is well known for the first, using the Arecibo telescope in 1974, in an attempt to solicit a response from extra-terrestrial intelligences.
Numbers are at the foundation of everything - including all of the bits and bytes behind this website. Numbers run so deep in all aspects of life, that we often seek to define relationships in nature and fundamental existence with numerical sequences and patters. And herein lies our problem with 'Knowing'...are the patterns that we arrive at with - including those with statistical significance - manifestations of creativity? coincidences of random chance? some universally implicated determinism? or prophecy?
That item - prophecy - will be addressed in our review of 'Knowing', Part 3.
LaLonde, L. (1974). The Upgraded Arecibo Observatory Science, 186 (4160), 213-218 DOI: 10.1126/science.186.4160.213
Sitler, R. (2006). The 2012 Phenomenon New Age Appropriation of an Ancient Mayan Calendar Nova Religio, 9 (3), 24-38 DOI: 10.1525/nr.2006.9.3.024
random chance vs determinism | Knowing, Part 1 (anewlifeinthesea.blogspot.com)
the historical value of the history on The History Channel (anewlifeinthesea.blogspot.com)
for more from the author, visit oceanopportunity.com.
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Sitler, R. (2006) The 2012 Phenomenon New Age Appropriation of an Ancient Mayan Calendar. Nova Religio, 9(3), 24-38. DOI: 10.1525/nr.2006.9.3.024
In the news this month we roundup of some highlights from the 217th meeting of the American Astronomical Society held in Seattle during January. The annual meetings of the American Astronomical Society are the largest gatherings of astronomers on the planet, and the presentations cover topics across the whole field of astronomy and astrophysics, including observational results, theoretical studies and simulations. Here are some of the highlights from this year's meeting.Starting big, astronomers working on the Sloan Digital Sky Survey released the largest colour map of the sky ever made. It's freely available, but be warned - it's big! Covering a third of the sky and created from millions of 2.8 megapixel images obtained by a dedicated 2.5-m telescope over the last decade, the full image is more than a terapixel in size - that's more than one trillion pixels. But it's not just a pretty picture. The full data release, the eighth from the SDSS project, contains a catalogue of objects as well as spectra allowing astronomers anywhere in the world to use the data as the basis for a diverse range of investigations into questions of galaxy evolution, dark matter and dark energy, the distribution and motion of stars in our own Galaxy, and much, much more.One use for sky surveys like the SDSS is searching for distant galaxies which can tell us about star and galaxy formation in the early universe. Because they are so far away, these first galaxies appear very faint by the time their light reaches us here on Earth. But there is a way around this. Gravitational lensing is the effect whereby the matter in a foreground galaxy can bend the light of a background object, making it appear distorted and magnified. This can be a helpful effect, allowing astronomers to see objects more distant than would otherwise be possible, but in surveys where the aim is to discover the size and brightness distributions of early galaxies, this effect can confuse the results. At the AAS meeting, a team of astronomers led by Stuart Wyithe at the University of Melbourne have estimated that as many as 20 per cent of the most distant galaxies currently detected appear brighter than they actually are, because of this lensing effect. With deeper surveys planned in order to probe the early universe, this lensing effect means that the best place to look for these primitive galaxies is probably near larger foreground galaxies, but understanding the lensing effects will be crucial to determining accurate statistics.Closer to home, spiral galaxies like the Milky Way often have numerous satellite galaxies orbiting around them. Over time, these galaxies slowly spiral inwards and are eventually disrupted, becoming streams of stars that are often only detectable in large surveys. Others are just too dim to see. But Sukanya Chakrabarti, a researcher at the University of California, has developed a new method of detecting such galactic companions. These dwarf galaxies may be too small and dim to be seen directly, but their mass affects the surrounding regions of their parent galaxies, causing ripples in the clouds of hydrogen within the spiral arms. Chakrabarti's method uses these ripples to infer the mass and location of otherwise invisible dwarf galaxies and has already been used to infer the existence of an undiscovered dwarf on the opposite side of the Milky Way to the Earth. The technique has also been tested on spiral galaxies in the nearby universe where high resolution radio observations can map the hydrogen gas in detail, correctly predicting the location of the companion to the Whirlpool galaxy, M51.Many galaxies are spirals, like our own Milky Way, containing large reservoirs of gas from which stars are currently being formed, while other so-called early-type galaxies are largely devoid of gas and no longer producing new stars. One of the current problems with our understanding of galaxy evolution is just how galaxies move from the spiral star-forming phase to the gas-poor "red and dead" phase of ellipticals. In a poster presented at the AAS meeting, a team have discovered that one particular elliptical galaxy is rapidly shedding molecular gas from its core. The galaxy, NGC1266, located in the constellation of Eridanus, is pumping out some 13 solar masses worth of molecular gas each year at speeds of up to 400 kilometres per second. Such a strong outflow could completely strip the galaxy of molecular gas required to form stars in just 100 million years, about 1 per cent of the age of the Milky Way. Many galactic outflows are driven by powerful starformation activity, but in this case there is little starformation occuring and the more likely culprit is a central black hole.The question of which came first, galaxies, or the supermassive black holes at their cores, is an ongoing debate in astrophysics. There is a direct relation between the mass of a spiral galaxy's central bulge of stars and that of its supermassive black hole, suggesting that black holes and bulges affected each others' growth. Previous studies have found galaxies in the early universe where the black holes were more massive than this relationship would suggest, implying that black holes came first. Now, astronomers have discovered a dwarf galaxy with a central supermassive black hole but no central bulge of stars, which they say strengthens the case that black holes did come first. This dwarf galaxy has an irregular shape, and strong radio and X-ray emission characteristic of outflows from the region around a black hole, and is likely to be similar to the first galaxies which formed in the early universe.Black holes are not all supermassive. GRS1915+105 is a binary system in the Milky Way with a black hole just 14 times the mass of the Sun, feeding on material from a companion star. As material from the companion spirals towards the black hole, it forms an X-ray emitting disk with material at its inner edge travelling at speeds of up to 50 per cent of the speed of light. Observations of the system at certain times show short pulses of X-rays being emitted every 50 seconds. Now, using a combination of observations from the Chandra X-ray Observatory and the Rossi X-ray Timing Explorer, a team think they know what's going on. In this phase, the inner region of the disk emits enough radiation to push material away from the black hole. Eventually the disk gets so bright and so hot that it disintegrates and falls towards the black hole, before the cycle begins again. Between pulses, the inner part of the disk refills from material further away from the black hole, while the radiation emitted heats up the outer disk and drives material away from the system, eventually limiting the amount of matter which the black hole can consume, and pushing the system into one of its other known states.More well-known periodic objects are pulsars, compact remnants left over when stars larger than eight times the mass of the Sun end their lives as supernovae. One of the brightest and well-observed pulsars lies in the heart of the Crab nebula in Taurus, a pulsar which has long been thought of as one of the steadiest high energy sources in the sky. So steady, in fact, that X-ray telescopes use it as a calibrator, and the brightness of other sources are often quoted in units of "millicrabs". But now, observations made with several high energy instruments have revealed that the Crab pulsar is far less steady than has been assumed. Observations with the Gamma-ray Burst Monitor on the Fermi satellite suggested that the Crab pulsar was dimming, but to prove it was a real effect rather than an instrumental problem affecting the observations, the team made further observations with several other high energy instruments, confirming that the pulsar has dimmed by seven per cent over two years. The result has implications for the in-flight calibration of X-ray instruments, as well as possible effects on previous results where the Crab pulsar was used to calibrate the observations.It's not just pulsars which vary. A class of stars known as Cepheid variables have a direct relationship between their maximum brightness and their period of variability. If you can measure the period, then you can calculate how bright the star would be at a given distance. By comparing this to how bright the star actually appears, you can calculate how far away it is. This relationship has long been used as a rung on the so-called cosmic distance ladder, allowing the distances of objects throughout the universe to be determined. Since Cepheids are the first rung on this ladder, and each rung on the ladder relies on the accuracy of the previous one, it is vital to much of cosmology that the calibration of Cepheid variability is accurate. But in a study carried out with the Spitzer space telescope, astronomers have discovered that the first star in the class, delta Cephei, is losing mass in a stellar wind at a rate which alters its mass and creates a surrounding nebula which affects the stars' apparent brightness. Further observations showed that as many as 25 per cent of Cepheids are also losing mass at a significant rate, with implications for distance measurements that underpin much of modern cosmology.Even the smallest of stars turn out to be not so constant. A study of more than 215,000 red dwarf stars has found that even these old stars produce flares strong enough to disrupt the atmosphere of any orbiting planets. Originally observed in a survey to search for dimming due to transiting planets, the data were later searched for evidence of flaring and produced several interesting results. The average flare duration was 15 minutes, and some flares increased the brightness of the star by 10 per cent, making them brighter than flares on our own, much larger, Sun. The astronomers also found that variable red dwarfs were about one thousand times more likely to flare than non-variable red dwarfs, possibly due to their strong magnetic fields.P... Read more »
SDSS-III collaboration: Hiroaki Aihara, Carlos Allende Prieto, Deokkeun An, Scott F. Anderson, Éric Aubourg, Eduardo Balbinot, Timothy C. Beers, Andreas A. Berlind, Steven J. Bickerton, Dmitry Bizyaev.... (2011) The Eighth Data Release of the Sloan Digital Sky Survey: First Data from SDSS-III. Astrophysical Journal Supplements. arXiv: 1101.1559v1
Wyithe JS, Yan H, Windhorst RA, & Mao S. (2011) A distortion of very-high-redshift galaxy number counts by gravitational lensing. Nature, 469(7329), 181-4. PMID: 21228870
In a trillion years we will be sitting in a big blob of a galaxy with no extragalactic sources to observe. I know what you are thinking, what about all the unemployed cosmologists in the far future? But don’t start a collection for the hardship fund just yet, luckily a new paper by a researcher at Harvard has come up with a way for astronomers in the far future to measure the parameters of the universe.... Read more »
Abraham Loeb. (2011) On the Importance of Hypervelocity Stars for the Long-Term Future of Cosmology. ApJ. arXiv: 1102.0007v1
As photons move through the universe they get gravitationally lensed as the pass by large clumps of matter. (As shown in the image above.) Dark matter, being the dominant form of matter, lenses these photons more than anything. Therefore, by studying the lensing properties of incoming photons, in principle we can reconstruct what the profiles of the dark matter doing that lensing.
Now, put (
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Michael L. Brown, & Richard A. Battye. (2011) Mapping the dark matter with polarized radio surveys. E-Print. arXiv: 1101.5157v1
Before we get too far ahead of ourselves, let's remember that dark energy being a cosmological constant fits the data very well and has for years. That said, experimental constraints allow for dark energy actually being an exotic form of phantom energy. (So for the time being we have to allow for the possibility and work out the details.) This was recently done by Dabrowski and Denkiewicz.
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Yesterday I came across this article, proclaiming to the world that "Saturn’s icy moon Rhea has an oxygen and carbon dioxide atmosphere that is very similar to Earth’s. Even better, the carbon dioxide suggests there’s life – and that possibly humans could breathe the air."
Say what? Ok. There's so much badness packed into those two lede sentences that I feel dirty just reprinting them here.... Read more »
Teolis BD, Jones GH, Miles PF, Tokar RL, Magee BA, Waite JH, Roussos E, Young DT, Crary FJ, Coates AJ.... (2010) Cassini finds an oxygen-carbon dioxide atmosphere at Saturn's icy moon Rhea. Science (New York, N.Y.), 330(6012), 1813-5. PMID: 21109635
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