We studied 14 presolar SiC mainstream grains for C-, Si-, and S-isotopic compositions and S elemental abundances. Ten grains have low levels of S contamination and CI chondrite-normalized S/Si ratios between 2 × 10−5 and 2 × 10−4. All grains have S-isotopic compositions compatible within 2σ of solar values. Their mean S isotope composition deviates from solar by at most a few percent, and is consistent with values observed for the carbon star IRC+10216, believed to be a representative source star of the grains, and the interstellar medium. The isotopic data are also consistent with stellar model predictions of low-mass asymptotic giant branch (AGB) stars. In a δ33S versus δ34S plot the data fit along a line with a slope of 1.8 ± 0.7, suggesting imprints from galactic chemical evolution. The observed S abundances are lower than expected from equilibrium condensation of CaS in solid solution with SiC under pressure and temperature conditions inferred from the abundances of more ...
TY - JOUR. T1 - Constraining phosphorus chemistry in carbon- and oxygen-rich circumstellar envelopes. T2 - Observations of PN, HCP, and CP. AU - Milam, S. N.. AU - Halfen, D. T.. AU - Tenenbaum, E. D.. AU - Apponi, A. J.. AU - Woolf, N. J.. AU - Ziurys, Lucy M. PY - 2008/9/1. Y1 - 2008/9/1. N2 - Millimeter-wave observations of PN, CP, and HCP have been carried out toward circumstellar envelopes of evolved stars using the Arizona Radio Observatory (ARO). HCP and PN have been identified in the carbon-rich source CRL 2688 via observations at 1 mm using the Submillimeter Telescope (SMT) and 2-3 mm with the Kitt Peak 12 m. An identical set of measurements were carried out toward IRC +10216, as well as observations of CP at 1 mm. PN was also observed toward VY Canis Majoris (VY CMa), an oxygen-rich supergiant star. The PN and HCP line profiles in CRL 2688 and IRC +10216 are roughly flat topped, indicating unresolved, optically thin emission; CP, in contrast, has a distinct "U" shape in IRC +10216. ...
An intermediate-mass black hole (IMBH) is a hypothetical class of black hole with mass in the range 100 to one million[citation needed] solar masses: significantly more than stellar black holes but less than supermassive black holes. There is as yet no unambiguous detection of an IMBH, but the indirect evidence from various directions is promising. The strongest evidence for IMBHs comes from a few low-luminosity active galactic nuclei. Due to their activity, these galaxies almost certainly contain accreting black holes, and in some case the black hole masses can be estimated using the technique of reverberation mapping. For instance, the spiral galaxy NGC 4395 at a distance of about 4 Mpc appears to contain a black hole with mass of about 3.6×105 solar masses.[relevant? - discuss] Some ultra-luminous X ray sources (ULXs) in nearby galaxies are suspected to be IMBHs, with masses of a hundred to a thousand solar masses. The ULXs are observed in star-forming regions (e.g., in starburst galaxy ...
ADC_Keywords: Stars, S ; Mass loss ; Masers ; Photometry, infrared Keywords: stars: mass-loss - stars: AGB - stars: late-type - infrared: stars - radio lines: stars Abstract: It is the purpose of this paper to rediscuss the circumstellar properties of S stars and to put these properties in perspective with our current understanding of the evolutionary status of S stars, in particular the intrinsic/extrinsic dichotomy. This dichotomy states that only Tc-rich ("intrinsic") S stars are genuine thermally-pulsing asymptotic giant branch stars, possibly involved in the M-S-C evolutionary sequence. Tc-poor S stars are referred to as "extrinsic" S stars, because they are the cooler analogs of barium stars, and like them, owe their chemical peculiarities to mass transfer across their binary system. Accordingly, an extensive data set probing the circumstellar environment of S stars (IRAS flux densities, maser emission, CO rotational lines) has been collected and critically evaluated. This data set ...
Black holes are an important area of research for theoretical physics as the behavior of the strong gravitational fields near the singularity of a black hole likely involve both gravitational and quantum effects. Understanding the behavior and properties of black holes tackles the ultimate goal of theoretical physics, unifying all known physical forces into a single theory. Recently, there has been much work done in understanding the thermodynamics of black holes, relating the properties of black holes to the laws of thermodynamics as well as understanding the concepts of information and entropy in the case of black holes. Considering black hole thermodynamics puts quantum effects and classical gravity in discussion with each other, as quantum field theory based descriptions of the Standard Model interactions on a curved spacetime around a black hole dictate black hole thermodynamics. In the course of this paper, I will derive and outline the various laws of black hole thermodynamics and discuss Hawking
Methanol Masers as Tracers of Circumstellar Disks: We show that in many methanol maser sources the masers are located in lines, with a velocity gradient along t
Supernova Sonata by Alex Parker From April, 2003 until August, 2006, the Canada-France-Hawaii Telescope watched four parts of the sky as often as possible. Armed with the largest digital camera in the known universe, CFHT monitored these four fields for a special type of supernova (called Type Ia) which are created by the thermonuclear detonation of one or more white-dwarf stars. Each supernova is assigned a note to be played: The volume of the note is determined by the distance to the supernova, with more distant supernova being quieter and fainter. The pitch of the note was determined by the supernovas "stretch," a property of how the supernova brightens and fades. Higher stretch values played higher notes. The pitches were drawn from a Phrygian dominant scale. The instrument the note was played on was determined by the properties of the galaxy which hosted each supernova. Supernovae hosted by massive galaxies are played with a stand-up bass, while supernovae hosted by less massive galaxies ...
In a newly published study, astronomers reveal evidence for a new intermediate-mass black hole about 5,000 times the mass of the sun. Nearly all black holes come in one of two sizes: stellar mass black holes that weigh up to a few dozen times the mass of our sun or supermassive black holes ranging from a million to several billion times the suns mass. Astronomers believe that medium-sized black holes between these two extremes exist, but evidence has been hard to come by, with roughly a half-dozen candidates described so far.. A team led by astronomers at the University of Maryland and NASAs Goddard Space Flight Center has found evidence for a new intermediate-mass black hole about 5,000 times the mass of the sun. The discovery adds one more candidate to the list of potential medium-sized black holes, while strengthening the case that these objects do exist. The team reported its findings in the September 21, 2015 online edition of Astrophysical Journal Letters.. The result follows up on a ...
Of Contraction of the Universe which Finally Becomes Dominant in the Big Crunch!. In the interest of accuracy and also to mention that this information is being misused by NASA and other U.S. government propagandists to try to distract from and obscure the significance of black holes and the central role black holes play in the process of contraction of the Universe, which ultimately becomes dominant over the simultaneous process of expansion. First, it is a fact that matter generally enters a black hole through a combination of both gravitation and magnetism. Matter in the accretion disk which spins around the black hole can only enter the black hole after it loses its angular momentum. The inertia of the material in the accretion disk keeps it spiraling in a disk rather than falling straight into the black hole. The inertia in turn is due to the mass of the material in the disc and the gravitational field caused by the extremely rapid rotation of the black hole itself. An accretion disc is a ...
Of Contraction of the Universe which Finally Becomes Dominant in the Big Crunch!. In the interest of accuracy and also to mention that this information is being misused by NASA and other U.S. government propagandists to try to distract from and obscure the significance of black holes and the central role black holes play in the process of contraction of the Universe, which ultimately becomes dominant over the simultaneous process of expansion. First, it is a fact that matter generally enters a black hole through a combination of both gravitation and magnetism. Matter in the accretion disk which spins around the black hole can only enter the black hole after it loses its angular momentum. The inertia of the material in the accretion disk keeps it spiraling in a disk rather than falling straight into the black hole. The inertia in turn is due to the mass of the material in the disc and the gravitational field caused by the extremely rapid rotation of the black hole itself. An accretion disc is a ...
Context. Intermediate-mass black holes (IMBHs) may provide the missing link to understanding the growth of supermassive black holes in the early Universe. Some formation scenarios predict that IMBHs could have formed by runaway collisions in globular clusters (GCs). However, it is challenging to set observational constraints on the mass of a black hole in a largely gas-free (and hence accretion-free) stellar system such as a GC. Understanding the influence of an IMBH in the center of a GC on its environment might provide indirect detection methods. Aims. Our goal is to test the effects of different initial compositions of GCs on their evolution in a tidal field. We pin down the crucial observables that indicate the presence of an IMBH at the center of the cluster. In addition to central IMBHs, we also consider the effects of different stellar-mass black hole retention and stellar binary fractions. Methods. We performed a set of 22 N-body simulations and varied particle numbers, IMBH masses, ...
A Black Hole is a region of space in which the gravitational field is so powerful that nothing can escape after it has past the event horizon of the Black Hole. The reason it is called a Black hole is that even light is unable to escape it. Black holes can be detected, when a black hole interacts with matter out-side of the event horizon a large amount of radiation emits from it. Black holes are currently understood by Einsteins general theory of relativity, which was formed in 1916. The idea of an object with a gravitational pull strong enough to prevent light escaping from it was first thought of in the 18th century. Einsteins theory predicts that when a large enough amount of mass is present within a sufficiently small region of space, all paths through space are warped inwards towards the center of the volume, forcing all matter and radiation to fall inward. While general relativity describes a black hole as a region of empty space with a pointlike singularity at the center and an event ...
These positrons are born at nearly the speed of light, and travel thousands of light years before they slow down enough in dense clouds of gas to have a chance of joining with an electron to annihilate in a dance of death," explains Higdon. "Their slowing down occurs from the drag of other particles during their journey through space. Their journey is also impeded by the many fluctuations in the galactic magnetic field that scatter them back and forth as they move along. All of this must be taken into account in calculating the average distance the positrons would travel from their birthplaces in supernova explosions." "Some positrons head towards the center of the Galaxy, some towards the outer reaches of the Milky Way known as the galactic halo, and some are caught in the spiral arms," said Rothschild. "While calculating this in detail is still far beyond the fastest supercomputers, we were able to use what we know about how electrons travel throughout the solar system and what can be inferred ...
In the available supporting (yet unreliable) study regarding the REACH endpoint "toxicity to soil microorganisms", toxicity o f TiO2 to soil bacteria was determined in the Biolog test over 7 consecutive days. No effects could be observed. The authors report the EC50 (7 d) to be , 100 mg TiO2/L. This result may in principle be used in a read-across approach to cover the endpoint requirements for the REACH registration of TiC. Toxic effects to soil microorganisms arise from exposure via soil pore water. Due to lower transformation/dissolution results for titanium carbide (the target substance) than titanium dioxide (the source substance), the resulting toxicity potential of TiC is also expected to be lower. Therefore, the dose descriptors are expected to be sufficiently high for the target substance, and read-across to the source chemical is adequately protective. In fact, (eco-)toxicologically relevant release of Ti ions from titanium carbide is not expected as the concentration of soluble Ti ...
A theoretical study of the interaction between supernovae and their surroundings is presented.. Supernovae are the endpoint of the life of massive stars, and are the dominant contributors to the chemical evolution of the Universe. During its life a massive star greatly modifies its environment. During and after the explosion of the star it interacts with its surroundings in a number of ways. A study of this interaction yields invaluable information about the late stages of stellar evolution and the physics of supernova explosions. Recent advances in observational facilities have given a wealth of observational data on interacting supernovae, and it is therefore essential to have good theoretical models for interpreting the data.. This thesis presents an overview of the physics of supernovae and of their interaction with a circumstellar medium. In particular the reverse shock created by the interaction is investigated. In most Type IIL and Type IIn supernovae this shock is radiative, and due to ...
The galaxy next door, Andromeda, is twice as massive as our own Milky Way galaxy, a new paper published online today in the Monthly Notices of the Royal Astronomical Society concludes. Astronomers have long known that Andromeda is bigger and brighter than the Milky Way, but some studies have suggested that our galaxy packs in enough extra invisible dark matter to beat it in total bulk. Now, calculations based on the latest measurements of galactic distances and motions show that each galaxy contains the same proportion of dark matter-about 90%-and that Andromeda is top dog after all.. ...
Just like normal black holes, they are regions of space-time with gravitational effects so strong that even electromagnetic radiation such as light can not escape from inside of them.. Julie Comerford, an astronomer at the University of Colorado Boulder, has led a team of scientists in analyzing this particular black hole and its two burps.. The Hubble telescope then picked up clouds of blue-green gas emerging from the black hole from a previous burp. While these two events are thought to have happened some 100,000 years apart, thats actually an incredibly short period of time when were talking about black hole activity. While even light can not escape the pull of one of these gravity wells, blacks holes do, very occasionally, "burp" back out chunks of half-consumed gas.. A paper on the subject was published in a recent issue of The Astrophysical Journal.. The black hole in question, known as J1354, is situated about 800 million light years from Earth and was studied using data captured by ...
Scientists have, for the first time, captured an image of a black hole. The image, captured by the Event Horizon Telescope, shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun, according to EHT officials. The image is the first visual evidence of a supermassive black hole. The shadow of a black hole is the closest scientists are able to get to taking a photo of the black hole itself, since black holes are
Scientists have, for the first time, captured an image of a black hole. The image, captured by the Event Horizon Telescope, shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun, according to EHT officials. The image is the first visual evidence of a supermassive black hole. The shadow of a black hole is the closest scientists are able to get to taking a photo of the black hole itself, since black holes are
Scientists have, for the first time, captured an image of a black hole. The image, captured by the Event Horizon Telescope, shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun, according to EHT officials. The image is the first visual evidence of a supermassive black hole. The shadow of a black hole is the closest scientists are able to get to taking a photo of the black hole itself, since black holes are
Scientists have, for the first time, captured an image of a black hole.The image, captured by the Event Horizon Telescope, shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun, according to EHT officials.The image is the first visual evidence of a supermassive black hole. The shadow of a black hole is the closest scientists are able to get to taking a photo of the black hole itself, since black holes are
Most galaxies in the universe, including our own Milky Way, harbor super-massive black holes varying in mass from about one million to about 10 billion times the mass of our sun. To find them, astronomers look for the enormous amount of radiation emitted by gas which falls into such objects during the times that the black holes are active, i.e., accreting matter. This gas infall into massive black holes is believed to be the means by which black holes grow.
What shape is the Milky Way? - The Milky Way shape is most likely in the form of a spiral galaxy because of its disc shape. Learn more about the shape of the Milky Way galaxy.
The black hole is like a generator spinning around in these magnetic fields," said BYU professor David Neilsen, lead author of the study. "The way the field lines get twisted around and pulled by the spinning black hole creates electromagnetic tension that gets turned into radiation and energy that goes out.". One black hole in the galaxy Centauras A propels radiation in a jet measuring 1 million light-years long.. The spin of black holes has been believed to play a role since the idea was put forward in 1977. The new study confirms this theory while also introducing a totally new component: that a black holes lateral movement also powers these jets.. ...
The biggest known explosion in the universe has been spotted by astronomers - and it was so intense it punched a crater the size of 15 Milky Way galaxies into a part of space hundreds of millions of light-years away. Scientists say theyve never seen anything like it. According to a study published Thursday in The Astrophysical Journal, astronomers discovered the record-breaking eruption using X-ray data from several sources, including NASAs Chandra X-ray Observatory and ESAs XMM-Newton, and radio data from the Murchison Widefield Array (MWA) in Australia and the Giant Metrewave Radio Telescope (GMRT) in India. It was so massive, they have little to compare it to. "In some ways, this blast is similar to how the eruption of Mt. St. Helens in 1980 ripped off the top of the mountain," lead author Simona Giacintucci of the Naval Research Laboratory in Washington, DC said in a press release Thursday. "A key difference is that you could fit fifteen Milky Way galaxies in a row into the crater this ...
We present new near-infrared (IR) observations of the Hβ λ4861 and Mg II λ2798 lines for 32 luminous quasars with 3.2 , z , 3.9 using the Palomar Hale 200 inch telescope and the Large Binocular Telescope. We find that the Mg II FWHM is well correlated with the Hβ FWHM, confirming itself as a good substitute for the Hβ FWHM in the black hole mass estimates. The continuum luminosity at 5100 Å well correlates with the continuum luminosity at 3000 Å and the broad emission line luminosities (Hβ and Mg II). With simultaneous near-IR spectroscopy of the Hβ and Mg II lines to exclude the influences of flux variability, we are able to evaluate the reliability of estimating black hole masses based on the Mg II line for high redshift quasars. With the reliable Hβ line based black hole mass and Eddington ratio estimates, we find that the z ∼ 3.5 quasars in our sample have black hole masses 1.90 × 10{sup 9} M {sub ☉} ≲ M {sub BH} ≲ 1.37 × 10{sup 10} M {sub ☉}, with a median of ∼5.14 ...
Recent spectroscopic observations of the outer halo globular cluster (GC) NGC 2419 show that it is unique among GCs, in terms of chemical abundance patterns, and some suggest that it was originated in the nucleus of a dwarf galaxy. Here we show, from the Subaru narrowband photometry employing a calcium filter, that the red giant branch (RGB) of this GC is split into two distinct subpopulations. Comparison with spectroscopy has confirmed that the redder RGB stars in the hk[=(Ca-b) - (b - y)] index are enhanced in [Ca/H] by ∼0.2 dex compared to the bluer RGB stars. Our population model further indicates that the calcium-rich second generation stars are also enhanced in helium abundance by a large amount (ΔY = 0.19). Our photometry, together with the results for other massive GCs (e.g., ω Cen, M22, and NGC 1851), suggests that the discrete distribution of RGB stars in the hk index might be a universal characteristic of this growing group of peculiar GCs. The planned narrowband calcium ...
Up until now, though, that hasnt been a terribly urgent goal; the time-scale of galactic events is immense, usually so long that the average scientist quickly gives up on the idea of seeing the universes most dramatic displays within their lifetime. That attitude may change with respect to galactic supernovae now, thanks to this teams finding that the Milky Way is virtually certain to host a supernova within the next 50 years. Given those sorts of odds, the team argues, it would be silly not to start investing right away.. Though it is nearby within the context of the entire universe, even a galactic supernova is happening very, very far away; the probability of a supernova strong and close enough to be visible to the naked eye is closer to 1 in 5. The chance of a sky-brightening event that outshines all other objects in the sky, something like the incredible event observed by Kepler in 1604, is more like 1 in 20.. This sort of work can be difficult to justify to funding boards since it could ...
Considering all that was accomplished in the field of physics last year, it is exciting to think about what the new year will bring. If the Event Horizon Telescope actually allows for images of the black hole at the center of our universe, it will significantly impact scientists and the general public. Physicists doing related work may be able to more accurately predict the volume and mass of the black hole, or how long it will be before our solar system gets devoured. For the general public, specifically those who often question the authenticity of science for religious reasons or other causes, a tangible image of a black hole could give them hard evidence that black holes are in fact real, or even merely more appreciation for what scientists do. It is impossible to predict exactly what might get uncovered about the universe in the future or what effect it will bear, especially on a galactic level, but the more we understand, the more questions we have yet to answer ...
A fleet of spacecraft including NASAs Hubble Space Telescope has uncovered unprecedented details in the surroundings of a supermassive black hole. Observations reveal huge bullets of gas being driven away from the gravitational monster and a corona of very hot gas hovering above the disk of matter that is falling into the black hole.. A team led by Jelle Kaastra of SRON Netherlands Institute for Space Research made use of data from ESAs XMM-Newton and INTEGRAL spacecraft (which study X-rays and gamma rays, respectively), the Hubble Space Telescope (for ultraviolet observations with the COS instrument), and NASAs Chandra (X-ray) Observatory and Swift (gamma-ray) satellites.. The black hole that the team chose to study lies at the heart of the galaxy Markarian 509 (Mrk 509), 500 million light-years away. This black hole is colossal, containing 300 million times the mass of the Sun, and is growing more massive every day as it continues to feed on surrounding matter, which glows brightly as it ...
A faint star in the Milky Way has been found to consist virtually only of hydrogen and helium. It has the lowest abundance of heavier elements ever observed, 20 times less than the previous record-holding star. This result is based on observations with the VLT telescope at the ESO Paranal Observatory. The discovery opens a new window towards the early times when the Milky Way galaxy was young, possibly still in the stage of formation.
These X-ray pulses take 300 years to traverse the distance between the central black hole and a large cloud known as Sagittarius B2, so the cloud responds to events that occurred 300 years earlier. When the X-rays reach the cloud, they collide with iron atoms, kicking out electrons that are close to the atomic nucleus. When electrons from farther out fill in these gaps, the iron atoms emit X-rays. But after the X-ray pulse passes through, the cloud fades to its normal brightness. Amazingly, a region in Sagittarius B2 only 10 light-years across varied considerably in brightness in just 5 years. These brightenings are known as light echoes. By resolving the X-ray spectral line from iron, Suzakus observations were crucial for eliminating the possibility that subatomic particles caused the light echoes. By observing how this cloud lit up and faded over 10 years, we could trace back the black holes activity 300 years ago, says team member Katsuji Koyama of Kyoto University. The black hole was a ...
It is said that fact is sometimes stranger than fiction, and nowhere is that more true than in the case of black holes. Black holes are stranger than anything dreamed up by science fiction writers.". In 2016 Professor Stephen Hawking delivered the BBC Reith Lectures on a subject that has fascinated him for decades - black holes.. In these flagship lectures the legendary physicist argues that if we could only understand black holes and how they challenge the very nature of space and time, we could unlock the secrets of the universe. ...
Another model involves a dense stellar cluster undergoing core-collapse as the negative heat capacity of the system drives the velocity dispersion in the core to relativistic speeds.[24] Finally, primordial black holes could have been produced directly from external pressure in the first moments after the Big Bang. These primordial black holes would then have more time than any of the above models to accrete, allowing them sufficient time to reach supermassive sizes. Formation of black holes from the deaths of the first stars has been extensively studied and corroborated by observations. The other models for black hole formation listed above are theoretical. The difficulty in forming a supermassive black hole resides in the need for enough matter to be in a small enough volume. This matter needs to have very little angular momentum in order for this to happen. Normally, the process of accretion involves transporting a large initial endowment of angular momentum outwards, and this appears to be ...
These four images are from a computer simulation of a star flying by and disrupting a circumstellar disk of dust around the star Beta Pictoris. Frame (a) shows the encounter setup, where a small M-class star swings within 700 astronomical units (1 AU is the distance between Earth and the Sun) of Beta Pictoris, an A-class star. The circumstellar disk, seen as a black donut in this overhead view, has a 500 AU radius. In (b) the gravitational tug of the intruder star pulls the dust disk into two tidal tails stretching far beyond the disks initial radius. Like spaghetti wrapped around a fork, the tidal tails are tangled together in (c). This leads to the formation of concentric ringlets of dust (d) on one side of the star. The entire sequence takes 100,000 years. This simulation explains observed asymmetries, knots, and other unique features of the Beta Pictoris disk.. ...
About the AdS/CFT solution of the problem: Suppose [a] that you believe in string theory [I do], then I think that it is reasonable to believe in AdS/CFT. Then it is reasonable to believe that there is no information loss for AdS black holes. BUT it is NOT reasonable to conclude from this that there is no information loss for realistic black holes. In particular, it is very silly indeed to argue that "black holes are local objects, so whatever works in AdS must work in the real world". Because AdS/CFT is *not* local in this sense --- if you believe that black holes are really "local" objects then you should not believe that AdS/CFT is relevant in the first place! As for the argument that "nothing special should happen" when you tune the AdS cosmological constant from small negative to small positive values, yeah, well, thats a great argument. I can use exactly the same "logic" to "prove" that ice can never melt. [Just tune the temperature up from -1 C to +1 C --- of course nothing special ...
We present the results of analyzing H$\alpha$ spectra of the radio emitting X-ray binary LS I+61303. For the first time, the same 26.5 d radio period is clearly detected in the H$\alpha$ emission line. Moreover, the equivalent width and the peak separation of the H$\alpha$ emission line seem also to vary over a time scale of 1600 days. This points towards the $\sim4$ yr modulation, detected in the radio outburst amplitude, being probably a result of variations in the mass loss rate of the Be star and/or density variability in the circumstellar disk. In addition, the dependence of the peak separation from the equivalent width informs us that the LS I+61303 circumstellar disk is among the densest of Be-stars ...