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The prehistory of the neutrino starts in 1896 when Henri Becquerel discovered some strange radiation emitted by uranium salts [Bec96]. Isolating the radium, Pierre and Marie Curie named this new phenomenon “radioactivity”. Ernest Rutherford showed that there were two types of radioactivity, alpha and beta, and the Curies identified the beta radiation as electrons.
The beta decay, i.e. the decay of a nucleus AZX into a nucleus AZ+1X with the emission of an electron, was experimentally studied from 1910. In 1914, James Chadwick noted for the first time that the energy spectrum of the electron was continuous, and not the mass difference between the two nuclei [Cha14]. Later, in 1927, Charles Drummond Ellis and William Alfred Wooster [Ell27] made a decisive experiment on radium E (bismuth-210), using a calorimetric technique giving direct proof that the electron spectrum was continuous. To face this contradiction, several important physicists, among them the famous Niels Bohr, suggested iconoclastically that energy was not conserved.
In December 1930, Wolfgang Pauli tried a desperate rescue of “the energy conservation principle”. He suggested that the electron is accompanied by a light, neutral, weakly interacting particle which takes away part of the energy [Pau30]. He called it “neutron” but after the discovery of the neutron by Chadwick in 1932 [Cha32], Enrico Fermi used the term “neutrino” which was immediately accepted by the community. At the Solvay conference in Brussels, in October 1933, Pauli presented “officially” the neutrino [Pau33], with some properties yet to be confirmed: a very small mass (possibly null), a probable spin 1/2. Incorporating the neutrino hypothesis, Fermi built immediately the theory of beta disintegration, which describes the decay of a neutron into a proton, emitting an electron and a “neutrino” [Fer33] (later this “neutrino” will be identified as a “antineutrino”).
In 1935, Maria Goeppert-Mayer calculated the (very small) probability of the simultaneous emission of two electrons and two neutrinos (the distinction between neutrinos and antineutrinos was not yet made) [Goe35], the double beta disintegration, observed experimentally much later in the 60’s.
In 1937, Ettore Majorana published his symmetric theory of electron and positron [Maj37], extended immediately to the neutrino by Giulio Racah [Rac37]. Today, we know that the neutrino is the only particle which could be identical to its antiparticle (Majorana type) and several experiments are actively looking for double beta decay without neutrino emission.
In 1934, Hans Bethe and Rudolf Peierls had showed that the cross section (probability of interaction) between a neutrino and a proton should be extremely small and that there was no practicable way of observing the neutrino [Bet34]. In spite of this, many physicists tried, unsuccessfully, to observe the neutrino, until the 50’s. A brilliant idea was proposed in 1946 by Bruno Pontecorvo [Pon46]: the use the inverse beta-process (νe + Z → e⁻ + (Z+1)) to detect the neutrinos, mentioning the famous chlorine-argon reaction (νe + 37Cl →e⁻ + 37Ar followed by the observed 37Ar decay), and quoting the Sun and nuclear reactors as significant sources of neutrinos.
It is only in the 50’s that the combination of high intense neutrino sources and large detectors could open the door towards the observation of the neutrino. After a first attempt close to the Hanford reactor in 1953 [Rei53], with a limited statistics, Frederick Reines and Clyde Cowan succeeded to observe the neutrino in 1956 at the Savannah River power plant [Cow56,Rei56]. The high neutrino flux (in fact antineutrinos) was provided by the fission reactions in the core of the plant, and the detector measured the reaction (νe + p → e⁺ + n).
From then on, neutrinos were fully part of the game of particle physics. In 1957, Tsung-Dao Lee and Chen Ning Yang suggested that parity was not conserved in beta-decay and proposed a two-component theory of the neutrino [Lee57]. A few weeks later, Chien-Shiung Wu and her collaborators observed experimentally that parity was not conserved in beta decay [Wu57]. At the end of 1957, Maurice Goldhaber and his collaborators found in a beautiful experiment that the neutrino was left-handed (had a negative helicity) [Gol58].
The idea that the neutrino coming from the muon decay would be different from the neutrino associated to the electron emerged in the late 50’s in two papers by Pontecorvo [Pon59b] and Schwartz [Sch60]. Leon Lederman, Melvin Schwartz and Jack Steinberger built in 1962 an experiment at the Brookhaven accelerator and discovered the muon-neutrino [Dan62].
The first atmospheric neutrinos coming from the interaction of cosmic rays in the upper atmosphere were observed in 1965 in India and South Africa [Ach65b,Rei65b].
From the 60’s, neutrinos were connecting two domains: particle physics when producing neutrino beams to explore the deep structure of the matter; astrophysics when studying the many sources, as cosmic rays, Sun, supernovae, …
In 1938, Hans Bethe and others developed the theory of solar fusion and energy production in stars, starting with the primary proton-proton fusion in the core of the Sun [Bet38,Bet39]. This reaction, which produces electron-neutrinos, was followed by a complicated cycle of nuclear reactions producing also electron-neutrinos. After the first solar models developed by John Bahcall in 1964 [Bah64], Ray Davis revisited the idea to use the famous radiochemical chlorine-argon reaction (νe + 37Cl →e⁻ + 37Ar followed by the observed 37Ar decay) to observe solar neutrinos in the Homestake mine [Dav64]. The first results, in 1968, showed a deficit of observed solar neutrinos compared to the predictions [Dav68]. This was the start of the solar neutrino problem.
In 1957, Bruno Pontecorvo proposed that neutrinos could oscillate in to antineutrinos when propagating [Pon57]. In 1962, after the discovery of the second neutrino family, Maki, Nakagawa and Sakata raised the idea of flavor mixing for the neutrinos [Mak62]. Pontecorvo revived his initial idea in 1967 and discussed the oscillation between electron-neutrino and muon-neutrino [Pon67]. Oscillation would imply that neutrinos are massive.
The new accelerators built at CERN and Brookhaven from the early 60’s allowed to build intense neutrino beams. These beams were used to study the properties of the neutrino interactions. The first great success came in 1973 with the discovery of neutral currents (interactions of neutrinos with matter (quarks or electrons) by Z exchange) by the Gargamelle bubble chamber at CERN [Has73a,Has73b]. This discovery was crucial for establishing the electroweak theory (unification of weak and electromagnetic interaction). The neutrino beams were also used to study deep inelastic scattering and test quantum chromodynamics (QCD).
In 1975, at SLAC, the team led by Martin Perl discovered the third charged lepton, the tau, announcing the third neutrino, the tau-neutrino ντ [Per75] and the third particle family. The tau-neutrino ντ was first directly observed in 2001 [Kod01]. In 1989, the LEP at CERN showed that there were only three neutrino families (to be precise three families of active neutrinos), establishing the standard model of particle physics [Aar89,Akr89,Dec89].
The question of the mass of the neutrino (0 or very small) is still at the center of many theoretical and experimental questions. The minimal standard model of particle physics requires a null mass. So a mass for the neutrino gives indications towards extensions of the model. From the experimental side, there are experiments trying to measure directly the neutrino mass using the beta decay of tritium, experiments looking for neutrino oscillation, experiments looking for double beta decay without neutrinos. From the theoretical side, the most popular model is the see-saw mechanism [Min77,Gel79,Yan79]. This mechanism explains why the neutrino masses are so much smaller than the masses of the other leptons and quarks: it generates three very massive right-handed neutrinos which are sterile (do not interact). Still alive, this mechanism has still to be proven.
In February 1987, the detectors Kamiokande in Japan and IMB in USA observed approximately 20 interactions due to neutrinos coming from the explosion of the supernova SN 1987A in the Large Magellanic Cloud which occurred 150000 years ago [Hir87,Bio87]. After the paper by Baade and Zwicky [Baa34], such a great event was predicted by George Gamow in 1941 [Gam41], and founded neutrino astronomy.
At the end of the 80’s, the same detectors Kamiokande and IMB showed a possible anomaly in the behavior of atmospheric neutrinos (produced by interactions of cosmic rays in the upper atmosphere): observing less muon-neutrinos than predicted [Hir88,Cas91]. This result, not confirmed by other experiments like the Fréjus one, stood for a further for 10 years. In 1998, the SuperKamiokande detector, 10 times bigger than Kamiokande, showed without ambiguity that muon-neutrinos coming from the antipodes had been partially transformed into tau-neutrinos via the oscillation mechanism [Fuk98b]. This great result solved the atmospheric neutrino anomaly and proved the existence of the neutrino oscillation and consequently that neutrinos were massive.
In 1989, the Kamiokande detector gave a new important result: the direct detection of the high energy solar neutrinos (so-called boron-8 neutrinos), but with a flux reduction compared to solar models which confirmed the solar neutrino deficit [Hir89]. In 1992, the radiochemical GALLEX experiment (30 tons of gallium at the Gran Sasso laboratory) detected for the first time the solar neutrinos produced in the primary proton-proton fusion in the core of the Sun; but the measured flux was still less than predicted by solar models [Ans92]. The solar neutrino problem was finally solved in 2001 by the Sudbury Neutrino Observatory experiment (SNO). Using 1000 tons of heavy water which allowed to observe all the neutrino flavors, they showed that part of the solar electron-neutrinos had been transformed into muon-neutrinos or tau-neutrinos [Ahm01,Ahm02]. Until SNO, detectors were sensitive essentially to electron-neutrinos. The two messages of SNO were that a) solar models are right; and b) solar electron-neutrinos oscillate between the core of the Sun and the Earth; this was the second proof of the existence of the oscillation mechanism after that observed in atmospheric neutrinos. To be precise, the solar electron-neutrinos are modified by a mechanism involving not only oscillation, but also an adiabatic transformation in the matter of the Sun predicted in 1985 by Lincoln Wolfenstein, Stanislas Mikheyev and Alexei Smirnov [Wol78,Mik85]. The corresponding oscillation parameters have been confirmed by the KamLAND experiment studying electron-antineutrinos produced by nuclear reactors [Egu03].
A new source of natural neutrinos was observed by the KamLAND experiment in 2005: the geoneutrinos coming from the radioactivity in the crust and mantle of the Earth [Ara05]. Statistically marginal, the first observation was confirmed in 2010 by KamLAND and Borexino at Gran Sasso [Bel10].
In 2010, the OPERA experiment at Gran Sasso observed directly the first tau-neutrino candidate produced in a muon-neutrino beam produced at CERN, 732 km away, confirming the oscillation [Aga10].
Having discovered the oscillation mechanism, we come back to the mixing matrix between the flavor eigenstates of two neutrinos and the mass eigenstates proposed by Maki, Nakagawa, Sakata and Pontecorvo (extended later to three neutrinos and parametrized in the so-called PMNS matrix). After the two mixing angles obtained in atmospheric neutrinos (θ23) and solar neutrinos (θ12), physicists began looking for the third angle (θ13). This angle was measured from 2011: a) in an accelerator experiment in Japan, T2K, observing the oscillation between muon-neutrino and electron-neutrino on a distance of 280 km [Abe11a]; b) in reactor experiments observing the oscillation of antineutrinos at a distance of ~1 km; Double Chooz [Abe11b], in France, Daya Bay [An12], in China, followed by RENO [Ahn12], in Korea.
The cosmological neutrinos, produced during the Big Bang, 13.6 billion years ago, constitute with the photons the most numerous particles in the Universe. Studying the cosmic microwave background (the mass of neutrinos has an effect on the CMB power spectrum), the Planck satellite gave in 2013 an upper limit on the total mass of neutrinos of about 1 eV [Ade13].
Already in 1960, Markov had anticipated that high energy neutrinos coming from galactic or extragalactic astrophysical sources could be detected using very large volumes of water, using the Cerenkov technique [Mar60]. In the 70’s, the first proposals were made, like the Dumand project [Rob76]. The first observation of high-energy astrophysical neutrinos has been done in 2013 by the IceCube experiment: a volume of about 1 km3 of ice at the South Pole instrumented with photomultipliers [Aar13a,Aar13b]. In 2018, high-energy neutrinos were observed by IceCube simultaneously with high-energy gammas from a flaring blazar, opening multi-messenger observation from astrophysical objects [Ice18].
In 2014, the Borexino experiment at Gran Sasso observed directly the solar neutrinos produced in the primary proton-proton fusion in the core of the Sun (GALLEX had observed an integral flux) and completed the spectroscopy of solar neutrinos [Bel14].
In 2017, the first observation of coherent elastic neutrino-nucleus scattering has been performed by the COHERENT collaboration [Aki17], providing new opportunities to study neutrino properties.
The (hi)story is still continuing: we do not know yet all the properties of the neutrinos, in particular their mass; we do not know if the neutrino is its own antiparticle (Majorana type); we do not know their precise role in supernova explosions; we do not know how much are produced in violent phenomena in the Universe; we have not yet observed cosmological neutrinos, produced 13.6 billion years ago during the big bang…
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Comptes-Rendus de l’Académie des Sciences, 122 (1896) 501 (2 mars 1896)
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|Bet39||H.A. Bethe||Energy production in stars||Phys. Rev. 55 (1939) 434|
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|Cha32||J. Chadwick||Possible existence of a neutron||Nature 129 (1932) 312|
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|Dan62||G. Danby, J.M. Gaillard, K. Goulianos, L.M. Lederman, N. Mistry, M. Schwartz and J. Steinberger||Observation of high energy neutrino reactions and the existence of two kinds of neutrinos||Phys. Rev. Lett. 9 (1962) 36|
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|Dav68||R. Davis, D.S. Harmer, K.C. Hoffman||Search for neutrinos from the Sun||Phys. Rev. Lett. 20 (1968) 1205|
|Dec89||D. Decamp et al., ALEPH Collaboration||Determination of the number of light neutrino species||Phys. Lett. 231 (1989) 519|
|Egu03||K. Eguchi et al.||First results from KamLAND: Evidence for reactor antineutrino disappearance||Phys. Rev. Lett. 90 (2003) 021802|
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|Fuk96||Y. Fukuda et al.||Solar neutrino data covering solar cycle 22||Phys. Rev. Lett. 77 (1996) 1683|
|Fuk98b||Y. Fukuda et al., Super-Kamiokande collaboration||Evidence for oscillation of atmospheric neutrinos||Phys. Rev. Lett. 81 (1998) 1562|
|Gam41||G. Gamow and M. Schoenberg||Neutrino theory of stellar collapse||Phys. Rev. 59 (1941) 539|
|Gar57||Richard L. Garwin, Leon M. Lederman and Marcel Weinrich||Observations of the failure of conservation of parity and charge conjugation in meson decays||Phys. Rev. 105 (1957) 1415|
|Gel79||M. Gell-Mann, P. Ramond and R. Slansky||Complex Spinors and Unified Theories||arXiv:1306.4669Supergravity, ed. by D. Freedman and P. van Nieuwenhuizen, North-Holland (1979) p. 315, retro-print & arXiv:hep-ph/9809459Talk by P. Ramond "The family group and Grand Unified Theories" at the 19th Sanibel Symposium, February 1979, retro-print|
|Goe35||M. Goeppert-Mayer||Double-beta disintegration||Phys. Rev. 48 (1935) 512|
|Gol58||M. Goldhaber, L. Grodzins, A. Sunyar||Helicity of neutrinos||Phys. Rev. 109 (1958) 1015|
|Has73a||F.J. Hasert et al.||Search for elastic muon-neutrino electron scattering||Phys. Lett. B46 (1973) 121 – Received Jul. 2, 1973|
|Has73b||F.J. Hasert et al.||Observation of neutrino-like interactions without muon or electron in the Gargamelle neutrino experiment||Phys. Lett. B46 (1973) 138 – Received July 23, 1973|
|Hir87||K.S. Hirata et al., Kamiokande collaboration||Observation of a neutrino burst from the supernova SN1987A||Phys. Rev. Lett. 58 (1987) 1490|
|Hir88||K.S. Hirata et al., Kamiokande collaboration||Experimental study of the atmospheric neutrino flux||Phys. Lett. B205 (1988) 416|
|Hir89||K.S. Hirata et al.||Observation of 8B solar neutrinos in the Kamiokande-II detector||Phys. Rev. Lett. 63 (1989) 16|
|Ice18||Ice Cube, Fermi-LAT, Magic, Agile, HESS, … collaborations||Multi-messenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922||Science 361 (2018) 1378 ; arXiv:1807.08816|
|Kod01||K. Kodama et al., DONUT collaboration||Observation of tau neutrino interactions||Phys. Lett. B 504 (2001) 218; arXiv:hep-ex/0012035|
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|Maj37||Ettore Majorana||Teoria simmetrica dell’elettrone e del positrone||Nuovo Cimento 14 (1937) 171|
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Neutrinos are, with the photons, the most abundant particles in the Universe. In the big bang theory (the “standard” model of the Universe), light neutrinos have thermally decoupled from the other forms of matter (quarks and leptons) approximately 1 second after the big bang, when the temperature decreased to about 1010 K (~ MeV). They constitute the cosmic neutrino background, the first witnesses still alive of the big bang (the photon background, the so-called cosmic microwave background (CMB), is “younger” since the decoupling took place 380 000 years later). Their temperature has now decreased to 1.95 K and their density (all the species together) is presently 330 neutrinos per cm3.
The energy of these relic neutrinos is so low (mean energy of ~0.1 meV) that their cross section is very small (order of 10-60 cm2) and it has not yet been possible to detect them. Some hope to detect relic neutrinos emerged when it was realized that coherent interaction can enhance the cross section. Indeed these low energy neutrinos have a macroscopic de Broglie wave length (≈ 0.5 mm). Several ingeneous ideas has been proposed since more than 50 years (see the review by Gelmini in 2004 [Gel04]) :
- – mechanical momentun transfer on macroscopic object [Oph74, Lew80], but this simple idea was shown to be highly reduced at the level of GF2 [Cab82]
- – torque on a ferromagnetic plate [Sto75]
- – torsion balance to measure the mechanical force exerted by elastic scattering of cosmic neutrinos on macroscopic targets [Hag99]
Steven Weinberg proposed in 1962 to look for the signal for relic neutrino capture on tritium [Wei62]. Raghavan revised this idea [Rag07] and today the Ptolemy collaboration [Bet13] is making the first steps toward its experimental realization.
It is also worth noticing that the interaction of (still undiscovered) ultra-high energy neutrinos (~ 1021 eV) with the relic neutrinos to produce a Z0, signed by a huge increase in the cross section [Wei82] (see [Rin01] for a recent review).
If no direct method has proved the existence of the relic neutrinos, there are indirect approaches which give confidence that they really exist:
- the big bang nucleosynthesis, which generates the light nuclei (D, 3He, 4He, 7Li) [Wag67], asks for a number of neutrino species smaller than 5 [Ste77].
- the cosmic neutrino background affects the evolution of CMB anisotropies and the structure formation in the Universe. The last results of the Planck satellite also require a number of neutrinos close to 3 [Ade13]; in addition, Planck and other cosmological experiments give a very constraining upper limit on the mass of the neutrinos.
Neutrinos as dark matter candidates ?
Since the works of Zwicky in 1933 and Rubin in 1970, we know that some “dark matter”, observed only through its gravitational interaction, is present in the universe and is about 6 times more abundant than the visible matter. As soon as the solar neutrino deficit was supposed to be the consequence of neutrino oscillation and that neutrinos are thus massive, physicists, knowing that there are many neutrinos (about 330 per cm3) of cosmological origin, proposed that neutrinos could be the main component of the dark matter. But, it required the neutrino mass to be at least of 10 eV. The lastest results on the neutrino oscillation parameters and the strong cosmological constraints on the neutrino mass provided by experiments like Planck have excluded this hypothesis and the hope to have found a good candidate for the dark matter.
The idea that a fourth neutrino which would be massive (~keV) and sterile has been popular in the recent years. We need more experimental proofs before considering that they could constitute part of dark matter.
During the conference on the History of the Neutrino (Sept. 5-7, 2018 in Paris) the subject of history of Neutrinos in Cosmology was reviewed by James Rich (CEA Saclay, France) : here the slides , the video of his talk and his contribution to the Proceedings.
|Ade13||P.A.R. Ade et al.||Planck 2013 Results. XVI. Cosmological Parameters||Astronomy and Astrophysics 571 (2014) A16; arXiv:1303.5076|
|Bet13||S. Betts et al.||Development of a relic neutrino detection experiment at PTOLEMY||arXiv:1307.4738|
|Cab82||N. Cabibbo and L. Maiani||The Vanishing of order-G Mechanical Effects of Cosmic Massive Neutrinos on Bulk Matter||Phys. Lett. B114 (1982) 115|
|Gel04||G. Gelmini||Prospect for relic neutrino search||arXiv:hep-ph/0412305|
|Hag99||C. Hagmann||Cosmic neutrinos and their detection||arXiv:astro-ph/9905258|
|Lan83||P. Langacker||On the detection of cosmological neutrinos by coherent scattering||Phys. Rev. D27 (1983) 1228|
|Lew80||R.R. Lewis||Coherent detector for low-energy neutrinos||Phys. Rev. D21 (1980) 663|
|Oph74||R.Opher||Coherent Scattering of Cosmic Neutrinos||Astron. & Astrophys. 37 (1974) 135|
|Rag07||R.S. Raghavan||Zero Threshold Reactions for Detecting Ultra Low Energy Cosmic Relic Neutrinos||arXiv:hep-ph/0703028|
|Rin01||A. Ringwald||Possible detection of relic neutrinos and their mass||arXiv:hep-ph/0111112|
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|Wei82||T. Weiler||Resonant absorption of cosmic-ray neutrinos by the relic-neutrino background||Phys. Rev. Lett. 49 (1982) 234| | 0.830932 | 4.216441 |
Proto-planet has two masters
A Rice University researcher will discuss images that may show the formation of a planet—or a planetary system—around a distant binary star at the annual meeting of the American Association for the Advancement of Science in Washington, D.C., today.
Andrea Isella, an assistant professor of physics and astronomy, will present images of the binary system known as HD 142527, captured by the new Atacama Large Millimeter/submillimeter Array (ALMA) radio telescope in Chile.
Isella said the binary system has long been known to harbor a planet-forming corona of dust and gas, but ALMA images are providing more detail than ever and allowing for better analysis of the system's contents and mechanics.
Isella studies the formation of planetary systems. In his talk, he will discuss the importance of mapping them and why exoplanetary systems - those outside the solar system - "exhibit such an impressive variety of properties."
The binary star is approximately 450 light years away in the Scorpius-Centaurus association, a cluster of young stars containing objects similar to HL Tau, the subject of the first high-resolution images taken as part of ALMA's long-baseline campaign in 2014. (Long-baseline interferometry allows multiple antennas to act as one. The size of the telescope is determined by the space between the antennas. During the long-baseline campaign, ALMA antennas achieved a maximum separation of 10 miles.) Images of HL Tau revealed ring structures in the dust and gas cloud around the star, an indication that planet formation is under way.
Images of HD 142527 show a broad ring around the double star. Most of it consists of gases, including isotopologues of carbon monoxide, but a huge arc around nearly a third of the star system consists of dust and ice, Isella said.
"Where the red in the image is brightest, the density of the dust peaks," he said. "And where we find a dense clump of dust, the carbon monoxide molecules disappear."
Isella and his colleagues suspect gas molecules freeze in the dust. "The temperature is so low that the gas turns into ice and sticks to the grains," he said. "This is important for planet formation. The solid dust needs to stick together to form a bigger body that will eventually attract more rock and gas gravitationally.
"If you try to smash rocks together, they don't stick together very well," he said. "If you smash snowballs together, they do. So when you form an ice mantle around the grains, you increase their capability to stick together."
He said the crescent-shaped dust cloud may be the result of gravitational forces unique to binary stars.
Until recent years, Isella said, astronomers thought it unlikely that planets could form and survive around binary systems. "The theory was that they could hardly find stable orbits," he said. "Most of the planets would either be scattered or fall into the stars. Then people started to discover planets around binary stars, so clearly they had to tweak the theory. The observation of systems like HD 142527 yields a fantastic opportunity to study the physical processes that regulate the formation of planets around binary systems."
HD 142527 will be the subject of an upcoming paper led by Rice postdoctoral fellow Yann Boehler, who is working in Isella's group.
Isella expects many revelations from the flood of high-resolution data provided by ALMA and other new radio telescopes, which capture images of stellar objects obscured by gas and dust that cannot be seen by optical means.
Isella and his colleagues also plan to discuss the early HL Tau images at the AAAS gathering. "We've been looking at these objects for at least 20 years," he said. "There are between a few hundred and a few thousand they can look at again with ALMA. They are starting with the brightest ones, because they are the easiest to observe.
"HL Tau was the brightest object of this type in the sky, and it has been well-observed, so they used it to make sure the instrument was working OK. But the rings they found in the system were completely unexpected.
"That's the beauty of the Atacama array," he said. "Every time you get new data, it's like opening a Christmas present. You don't know what's inside."
Isella will speak as part of the "Planet Formation Seen With Radio Eyes" session at AAAS on Feb. 13. | 0.91144 | 3.790154 |
Following the theme of last week’s papers which took a look at alternatives to radio searches, this week’s papers focus on laser SETI in the optical and near-infrared. The first paper to discuss this possibility was Schwarz & Townes 1961, which was published just two years after Cocconi & Morrison motivated the radio SETI search in 1959. In an act of sheer clairvoyance (probably afforded by the fact that Townes won the Nobel prize for the discovery of lasers), the authors predicted a time when “maser apparati near the optical” technology would exist and be a viable alternative method of interstellar communication.
Notably, in our timeline, the discovery of lasers followed the development of radio communications; however, it seems that there is no necessary reason why this ought to be the case. One could imagine an ETI developing proficiency with lasers first, and hence use those as the primary means to signal to other ETI. Therefore, the abilty to detect a optical beams is an important addition in the ensemble of SETI search avenues.
To detect such a beam, the authors set two criteria: 1) that it produces enough photons per unit of area on the r eceiving end to be detectable (given the design of the detector and telescope), and 2) that it is distinguishable from the background. Given those criteria, they examined the possibility of whether or not an optical beam can be used to establish interstellar communications by testing two systems: 1) one which consists of a continuous 10kW beam at 5000A with a bandwith of 1Mhz and assuming a 200in reflector telescope, and 2) an array of 25 lasers like in part (1), but with an effective aperture of 4in. They conclude that in both cases that a signal carried on such a beam ought to be detectable to a distance 10ly given c. Earth 1960 technology. Of course, the technology of today is significantly more advanced than sixty years ago, so probably this estimate is highly underrated.
This paper is important because it was one of the first to offer a novel approach to the SETI problem (I believe the second after the Dyson 1960 paper). This paper’s predictions were vindicated by papers such as the other one for this week (Wright 2014) and others which actually conducted optical and NIR SETI searches. This paper laid the groundwork on which these subsequent additions build and helped frame our thinking about how a laser search ought to be conducted. Indeed, as we move further into the 21st century (only the second century of electronic technology on Earth) we are fastly transitioning to fiberoptical communication. Could it be that other societies also inevitably reach this conclusion as well (or at least transition through such a phase on a path of development to some even more advanced communication scheme)? Only a dedicated laser SETI search can attempt to answer those questions!
Continuing with the theme of optical SETI from last week, this week’s Howard et al (2004) paper discussed the results of an optical SETI experiment which searched for pulsed beacons around thousands of stars. Following with the other optical SETI papers we have encountered, the authors compare the merits of searches in the optical/NIR with searches for microwave/radio signals. If one’s figure of merit for the efficiency of technique is the signal-to-noise achieved for a fixed transmitter power, then optical methods are comparable to those of radio.
They further motivated this search by presenting the “Fundamental Theorem of Optical SETI”, which is a statement of the observation that even at our early stage of technology (Earth “2000”), we can already generate artificial optical pulses could appear to outshine the brightness of the Sun by a factor of 10^4. This follows a similar line of reasoning as the Schwarz & Townes paper from last time, which plausibly suggested that some ETIs would rapidly discover some form of optical interstellar communication and use it. However, in the case of Howard’s paper, the focus is on the search for pulsed beacons, which are unambiguous detections of alien laser signals (for which there are no possible astrophysical confounders or dopplegangers).
With similar avalanche photometer instruments at Harvard and Princeton, they began their campaign which would eventually consist of some 16,000 observations totalling 2400 hours of observing time spread over a five year baseline. They searched 6176 stars in their survey, of which only a handful of signals showed any promise as plausible artificial pulses (most were explained away as being stochastic in nature). Three triggers from HD 220077 were considered the most interesting, and were allotted many follow-up observations. Upon further investigation of those candidates, they found that their photon rate was consisten with Poisson noise and thus rule out the alien hypothesis. (Remember, it’s never aliens!) Another interesting pair of triggers from HIP 107395 was considered too ambiguous because of an asynchronicity between the Princeton and Harvard clocks.
This work was performed in fulfillment of Howard’s PhD thesis in astronomy; Andrew Howard is now a prominent exoplanetologist and astronomer, and so this work is a demonstration of SETI being firmly rooted as a part of astronomy and an example of the quality that SETI papers ought to strive for (that is, when it is taken seriously by astronomers and other scientists). It is also a good example of “Forensic” SETI done right, where the candidates were scrutinized on a case-by-case basis and all natural explanations were attempted to be exhausted before jumping to unsubstantiated conclusions (which contrasts with the approach of some other papers we have read this semester *cough* faces on Mars *cough*). Although the results were null, the study still placed valuable upper limits on the occurrence of beacons around nearby stars. Therefore, this paper serves as a template for how null results ought to be reported and makes a case for them to be published.
The theme between the Townes (1983) and Hippke & Forgan (2017) papers is that our SETI efforts should not be solely focused on searches in microwave and radio frequencies. These papers make the case that there are in fact equally viable if not superior alternatives to radio in both the infrared (IR) and X-ray portions of the electromagnetic spectrum, respectively. SETI experiments have been influenced by the precedent set by the earliest ideas in the field, which emphasized the radio search (and often near the 1.2-1.67GHz water hole). In fact, it was Cocconi and Morrison who gave us the idea that the most important factor when imagining interstellar communication systems is their efficiency in terms of photons per watt, which led them to pursue the radio search. However, with the development of new technologies and perspectives, it is clear that this narrow viewpoint misses out on a greater variety of possibilities.
These are examples of quality SETI papers because they attempt to expand our perspective and push boundaries. They remind us that we should be ever aware of falling into narrow-minded modes of thinking, and that when dealing with the perplexity of trying to predict the motivations and strategies of an ETI, we should stoically expect that we are wrong. They are also remarkable in their approach to the question. In the case of Townes, he thinks critically about the observational challenges of moving to the infrared and quantitatively compares the pros and cons of IR methods with those of microwave/radio. He is also cognizant of the fact that there are a lot of assumptions (which he makes explicit) made about the strategy of a transmitting ETI which we can only speculate about and limit the effectiveness of the IR search. On the other hand, Hippke & Forgan are motivated by the search of the global optimum for interstellar communication, which they decide ought to be in the X-ray near 1nm. In pursuit of this grail frequency, they examine a variety of astrophysical and observational difficulties which complicate communication, such as diffractive photon loss, interstellar extinction, and atmospheric transmission. In this way, both papers are firmly rooted in taking a classically quantitative and astronomical approach to SETI. This places these papers a tier higher than those which solely offer speculation on search strategies unsubstantiated by rigorous examinations of the merits of the alternative. Overall, the field benefits when scientists take SETI seriously and improve it by contributing to it with quality papers.
My opinion of this paper is completely biased by the fact that I’ve actually met David Kipping and that I read this paper back when it first went on the arxiv. This was my first exposure to SETI (beyond science fiction, if that counts) and I think it went well!
Kipping and Teachey postulate that a civilization (even the Earth) could use lasers in some interesting ways. They first suggest that a planet’s transit could be clocked, monochromatically, against a Kepler-like survey, without the need for much power (~30MW). Due to the Earth’s rotation, this would require multiple laser stations, but in the end, it would be doable. They then continue on to talk about clocking the signal at all wavelengths. This would be a bit more challenging, since many lasers at many different lasers would be required, and again these lasers would need to be placed around the planet, and the power requirement would increase by an order of magnitude, but a committed civilization could manage it. Both of these cloaking processes can be argued against since the planet would still be detectable via other detection methods (namely RV).
The last bit of cloaking they suggest involves the cloaking of biosignatures. A disequilibrium in an atmosphere (normally of oxygen) is a decent indication of life on a planet. These and other related absorption features are referred to as biosignatures. If lasers were emitted at these absorption features, then the planet would still be detected and noticed, but it would just not be studied much since it would be presumed uninhabitable. This is all, of course, under the assumption that other life out there is Earth-like, and that this Earth-like life would be looking for signatures similar to their life (Earth-like). Because of this Earth-like assumption, it is possibly that another civilization is already doing this for *their* biosignatures, we just don’t notice it though because we are looking for our biosignatures (also clouds are apparently all that we can see right now).
Lastly, the authors bring up the point that this laser method can be used not just to cloak, but also to signal existence. They briefly mention that the easiest way to get someone’s attention with this would be to cloak the transit’s ingress and egress, making the transit appear boxy and all around wrong.
Although this is a neat idea, it seems a little far fetched and specific to me. Sure, we have tons of data, so someone might as well look through for boxy transits (I think someone has already done this with Kepler data), but this seems so absurdly unlikely to happen. However, my thoughts on the likelihood of this completely come from the way I view humanity and our goals and motivations, so it’s just as possible that my thoughts of this being a waste are a minority in the galaxy.
I feel that it is quite appropriate for me to review this paper by David Kipping two days after we conducted an observation of 12 transiting Kepler planets from Green Bank Telescope in association with Breakthrough Listen, based on the principle outlined in this paper.
The paper talks about using lasers to cloak the presence of a planet during its transit. However, in this blog I shall not talk about a civilization trying to mask its presence but its attempts to broadcast itself. The paper proposes the principle of a temporal Schelling point in our search for ETI. The question often arises of the best time to search. Since there is no real special time, this paper suggests that the transit of an exoplanet around its host star could be one. If there is a beacon on the night side of the planet, then it would sweep out an arc as the planet revolves around its star. This beacon would be visible from our line of sight when the planet transits the star, if it is directly aimed at its sub – stellar point. This beacon if broadcast continuously would be visible to observers periodically with every transit. Doing this during a transit is an interesting proposition since transits allow for us to also measure the atmospheric composition of planets using spectroscopy. Further, in the near future we should be able to map the longitudinal heat profile as well as atmospheric composition of planets using phase curve spectroscopy. This would provide for definite clues of bio-signatures.
However, the beacon might not necessarily be on a planet which is inhabited by the ETI. The beacon can be on the closest planet, since that would have the highest probability for transiting in a randomly oriented system.
I think this paper is important in acknowledging the special place transits occupy in the optical astronomy, and subsequently extending it to SETI. Its ideas about a civilization using this phenomenon to hide its presence or beam out and advertise itself are novel, and can be one of the anomalies being considered in Wright et al. 2015 (GHat 4).
Everyone has been in a situation where they need to make themselves conspicuous. Proponents of SETI have often provided novel solutions to ensure an observer would readily identify their planet as one hosting life. The answer can be condensed to a basic principle: do something unnatural at the exact moment someone is observing you. David Kipping, an astronomer at Columbia University, who searches for planets and moons beyond our solar system, believes lasers can be used by ETI to serve as a beacon or mask a planet entirely. In a recent paper, Kipping and a graduate student argue that artificial transit profiles can be feasibly generated using laser emission. Unlike optical SETI, which focuses on pulses of light, Kipping believes the transit can be a useful signal to or cloak from Earth (see Movie 1).
Movie 1. Alex Teachey on Cloaking Planets
One of the co-authors of this paper sets out to describe how lasers could be used to cloak a transit. The timing of this video showed poor foresight (April Fool’s Day….). A secondary video by Alex provides answers to some common questions from YouTubers.
The use of transits in SETI goes back to the pre-Kepler days, when Luc Arnold first proposed distinguishing a transiting mega-structure from a natural body. Cloaking a planet requires many assumptions. Kipping ask us to consider an arbitrarily advanced civilization that discover all “nearby” habitable planets along their ecliptic plane. Kipping assumes the inhabitants would know which of these planets could observe their transits and, through some machinations privy only to ETI, such civilization would decide to prevent detection by these planets using the transit method. Kipping et. al. dismiss a previous suggestion of a mega-structure, arguing a powerful laser would be “technologically more feasible”. After performing a few calculations, Kipping et. al. argue a ~60 MW laser would serve as an optical, “broad-band” cloak and prevent detection from a mission such as Kepler. A laser, while monochromatic, could in theory serve to effectively mask a transit, as shown in Figure 1. Kipping et. al. argue that a laser array on the surface of a planet would be difficult and that instead ETI could place an array of lasers in space (colloquially known as a weapon). The authors aptly refuse to compare either solution. A similar and energetically cheaper alternative would be to use lasers to block out the absorption lines of biosignatures.
Figure 1. The Strange World of David Kipping
Both images are from Kipping et. al. 2016. On the left: Cloaking of a Transit Signal. The top panel shows the unaltered transit for various missions. The middle panel is the power profile of a 600 nm laser array designed to cloak the Earth. The bottom panel shows what an observer would detect. On the right: Using Transits as a Beacon. The top panel shows the power profile of a laser array designed to broadcast the Earth. The bottom panel shows the transit signature an observer would detect. The laser makes for very unnatural signatures that distinguish it from orbiting planets.
In addition to cloaking, Kipping et. al. briefly discuss signaling via lasers. Broadcasting would be much cheaper, as it would not have to be broadband. The ingress and egress could be altered with lasers as shown in Figure 1. Another possibility, is to use lasers to etch intriguing patterns during the light curve. Kipping has stated:
You can make your transit look strange, have bumps and wiggles, maybe even the New York City skyline—whatever you want.
Savvy extraterrestrial scientists could use a deformed transit as a beacon to announce their existence (see Figure 2). By Kipping’s hypothesis, ETI no longer required planet-size megastructures, such as a rotating triangle or louvres, to produce unnatural transit signatures.
Figure 2. Laser Doodles
Going from top to bottom: (i) An unperturbed transit showing how a star dims slightly when an orbiting planet passes in front of it. (ii) A transit showing different shapes due to a laser array aimed toward an observer. This example shows the New York City skyline. (iii) The ideal beacon would be a square. This is a simple shape that would never occur naturally (yay limb darkening) and would require a laser only at ingress and egress. Source: David Kipping
The reader is left with many questions and a sense of unease given all the assumptions. The ETI in question is apparently aware of all habitable planets in its ecliptic plane and capable of generating an array of lasers to block its transit. This is an act in vain if said planets use other techniques (i.e. direct imaging or radial velocity) to detect said planet. Kipping et. al. acknowledge this:
Transits are not the only method to discover planets and thus a truly xenophobic civilization may conclude that even a perfect and chromatic transit cloak would be ultimately defeated by observation of the planet using radial velocities. In this sense, the biocloak is perhaps the most effective strategy since certainly the transit and radial velocity measurements would appear compatible. However, even here, direct imaging would reveal a strong discrepancy in terms of the atmospheric interpretation and thus overcome the cloak.
A large part of this paper was to discuss how a transit could be cloaked, only to have that entire hypothesis appear to be an act in vain. The discussion on broadcasting with a strange transit signature is not fundamentally new. This blogger is left pondering the purpose of this paper. The authors themselves have dismissed the efficacy of cloaking and suggest we search for strange transits, something proposed by Arnold a decade earlier. Even if one were to assume cloaking to be efficient, SETI has predominantly concerned itself with civilizations indifferent to outside observers. After all, one could always invoke any arbitrary set of conditions or technology that would make a civilization impossible to detect. While the method of using lasers is novel, the rest of the paper reminds astronomers to search for strange transit signatures. Believe this requires strong priors and an indifference to all the assumptions. Kipping himself expects detections “on the order of a few dozen” and this blogger wishes him the best in his future endeavors.
Since the conception of communications with extraterrestrial civilizations in the late fifties (Cocconi & Morrison 1959), the overwhelming majority of SETI endeavors have centered on electromagnetic communication systems, often in one narrow fraction of the entire spectrum. Hippke is aware of the potential shortcomings of such an approach and presents the possibility of alternatives, not just to microwave emission as in his previous work (Hippke 2017), but to electromagnetism as a medium for information carrying in general. In particular, he examines the merits and shortcomings of a variety of non-EM carriers such as electrons, protons, neutrinos, gravity waves, and occulting megastructures. Vetting based on energy efficiency and data rates, Hippke places these alternative channels in competition with EM-based communications. For transiting megastructures, Hippke fails to find a way for this method to be competitive when it comes to target communication with high data rates, and so tepidly dismisses them. He also quickly rules out charged particles, particles with short lifetimes, and heavy particles due to interstellar magnetism, longevity, and energy requirements, respectively. He is also critical of gravitational waves as a medium for signal carrying as their artificial production is extremely resource intensive and wasteful. Lastly he examines neutrino based communication, which fails due to issues with focusing when compared to photons and size requirements of detectors. All of his conclusions are based on current knowledge of physics, and so the possibility is open that with an improvement in knowledge, some of these avenues may potentially become viable again. He has framed this investigation to work within the confines of what is currently understood. With these limitations, he concludes that the best medium for point-to-point communications is still electromagnetic radiation, at around the 1nm scale. If the assumption of preference for speed is relaxed, then the best alternative would be inscribed matter, or probes carrying vast databases of information. This paper was a novel contribution to SETI because it is one of the first attempts at an exhaustive analysis of alternative modes of communication. Scientists can often times get caught up in the present paradigm, and so it is beneficial to get a fresh perspective on the issue from someone who is not formally scientifically trained and thus potentially not subject to the same prior perceptions. His conclusions also vindicate the thinking behind the Pioneer and Voyager plaques and records, since physical media transported on long timescales is shown to be one of the preferred methods of communication. The potential this paper had to to retroactively dismiss all of our previous SETI efforts as foolishly narrow-minded or misguided should not be discounted. While we will continue to perform SETI in the radio and microwave, we should always be open to the possibility of alternative means of communication, and at the very least entertain a more expanded search of the electromagnetic spectrum when designing future SETI surveys.
This 1961 paper by R.N. Schwartz and Charles Townes, discusses using Optical Masers (Lasers) for communication across interstellar distances. I feel that it is worth noting that this falls closely on the Cocconi and Morrison paper of 1959 which first suggested the water-hole in the radio as the ideal place to look for, for intelligent extra terrestrial (ETI) civilization.
The authors talk about the recent discovery of ruby optical Masers by Townes. Since the M in Masers is for Microwave, optical Masers, were soon called Lasers or Light Amplification by Simulated Emission of Radiation.
The authors consider using Optical Masers (Lasers) on two different systems and compare the two. One is a laser on a 200 inch telescope (like the 200 inch Hale Telescope), whereas the other is 25 individual 4 inch telescopes with Lasers pointed in the same direction. They consider atmospheric seeing as a limiting factor and hence consider that the 25 individual small telescopes might be a better option. I think this paper was really advanced for its time, since 4 years after the launch of Sputnik (1957) it considers the use of Adaptive optics and space telescopes.
It also considers the detectability of Lasers using 1961 technology levels for laser power and detectability. The paper also talks about high resolution spectrometers which could spectrally resolve the laser and hence detect that this artificial beacon outshines the host star. This would be a hallmark of its artificial origins.
The paper concludes by noting that the water hole in the radio should not be the only region where we look for interstellar communication. It also mentions that an advanced ETI might develop capabilities that we have ruled out and consider impractical.
Optical SETI is not exactly a novel approach, but one that has not yet been pursued in earnest. There have been recent efforts by Andrew Howard, Shelley Wright, Nathaniel Tellis in this direction. We must take advantage of the vast resources that are plowed by the astronomical community in this direction and utilize the instruments, development and data sets that exist as a product of this.
Cocconi and Morrison initially proposed interstellar communication using radio waves, particularly near the hyperfine transition of hydrogen. The first SETI observations, conducted by Frank Drake, followed this suggestion of where to look. The focus in the microwave was a result of technological limitations, as observations at other frequencies were unimaginable when Cocconi and Morrison initially presented their work. With the discover of the maser in the 1950s, a new vector for communication became available. The authors postulated that “maser oscillators and other appropriate apparatus in or near the optical region [will] allow detectable light signals to be beamed between planets of two stars separated by a number of light years”. The creation of the laser in 1960, a more practical device than a maser, served as further justification for this claim.
Townes and Schwartz note the physics behind the maser was first described by Einstein. There was no theoretical deficit precluding its discovery or delaying development. The authors use this to argue that there may exist an extraterrestrial society comparable to Earth that discovered and developed masers before radio waves. They boldly state:
We propose to examine the possibility of broadcasting an optical beam from a planet associated with a star some few or some tens of light-years away at sufficient power-levels to establish communications with the Earth. There is some chance that such broadcasts from another society approximately as advanced as we are could be adequately detected by present telescopes and spectrographs […]
A maser, much like its optical counterpart, could theoretically operate continuously at high power and would be almost monochromatic. Townes and Schwartz note the limit to producing an ideal maser would be the technological problems in mirror accuracy and control of any optical distortions. They considered two masers (1) one energetic maser and (2) twenty-five masers pointing in the same direction and specified two criteria for the detectability of either maser:
it must produce enough photons per unit area at the receiver to be detectable with a lens of practical size and in a reasonable time and
it must be distinguishable from the background stellar light.
They argued that the intensity of radiation from the group of masers would produce a beam of high intensity capable of being observed by the naked eye or binoculars out to 0.1 or 0.4 light years, respectively. A larger telescope of long integration would be required for masers further than 10 light years. The authors note that, from the work of Cocconi and Morrison, there were ten Sun-like stars within a distance of 10 light years, making masers very applicable to SETI. Spectra would be another useful diagnostic for a maser. A grating spectrograph in the 1960s could have resolved the energetic maser as a signal equal to the stellar background. Noting this, Townes and Schwartz propose that “[a] spectral line sought can be expected to be exceptionally narrow, at an abnormal frequency for the type of star in question, and varying in intensity [o]bservation of any of these characteristics should lead to closer examination” of an object.
In less than a decade after discovery, masers were already being considered for SETI. The advantages include the coherence of radiation over a very large aperture and the theoretical possibility of obtaining coherence among several maser sources. Given that nay plausible atmosphere would prevent emission of masers, the authors propose utilizing a “very high-altitude balloon, a space platform, or natural Moon”. Only two years passed after Cocconi and Morrison published and people began considering where to look. This is an on-going discussion, but the authors correctly argue that charged particles would be deflected while UV and IR emission would be absorbed by an atmosphere. This blogger considers this to be an important discussion. When this was originally published, SETI was still in its infancy and the authors emphasized the need to consider other wavelengths before all of SETI focused on microwaves. While the development of masers may have stymied after the discovery of the more practical laser, optical SETI now exists. Recent progress in masers (see Movie 1) suggest their applicability will soon increase. Perhaps the masers of the future will become useful for SETI as Schwartz and Townes initially proposed.
Movie 1. Mainstream Masers Coming Soon™
Laser are everywhere, but masers came first! They are like lasers but in the microwave. This video shows the latest applicability of masers. Who knows, perhaps the suggestion by Schwartz and Townes to use masers for communication is not too far off.
We propose to examine the possibility of broadcasting an optical beam from a planet associated with a star some few or some tens of light-years away at sufficient power-levels to establish communications with the Earth. There is some chance that such broadcasts from another society approximately as advanced as we are could be adequately detected by present telescopes and spectrographs, and appropriate techniques now available for detection will be discussed. Communication between planets within our own stellar system by beams from optical masers appears a fortiori quite practical.
They concluded “the frequency of the hydrogen line in the micro-wave region is not the only reasonable place at which to search for possible interstellar communications, and […] the optical region also seems a logical one”. This paper can largely be viewed as a continuation of his initial work.
Townes begins by motivating SETI at other wavelengths. An extensive search focusing on one regime in the electromagnetic spectrum would be a large endeavor and potentially a waste of resources. The communication capabilities of ETI were assumed to be analogous to our capabilities. The principals for SETI are described via various strategic questions and under the assumption ETI wishes to minimize costs of any technology they use. The first question addressed is the nature of the signal, primarily if ETI signals would be isotropic or directive. It is preferred that a civilization broadcast narrow band. Townes uses the excessive power an isotropic signal would require (9 ordered of magnitude more) to suggest ETI would favor sending a beam. Other assumptions regarding ETI and its capabilities:
regarding power sources, there is no necessary choice as a function of wavelength from the radio region down at least into the ultraviolet,
there are detectors of sensitivity close to the ultimate limit dictated by the quantum properties of radiation over the whole range of wavelengths, and
if needed, the use of space for the beacons is to be expected.
Townes consider numerical evaluations of the signal-to-noise ratio (SNR) for different wavelengths. One potential observation scheme involves using longer wavelengths with linear detection of all wavelengths and a constant antenna area but solid angles corresponding to the diffraction limit only for wavelengths >1 cm. The other observation scheme involves short wavelengths with a quantum counting detector and an antenna with a fixed diameter for long wavelengths down to 1 cm and then decreasing linearly in size to 10 m in the infrared.
These were but two examples discussed. Townes concludes that, depending on the assumptions, other regions, such as the infrared, should be considered. This was a marked departure from what was initially proposed by Cocconi and Morrison. While Townes initial suggest of using the infrared may not be used today, the discussion regarding where to look is still ongoing. Experiments in optical SETI have since been conducted (e.g. Reines & March, 2002), Laser SETI is a thing (see Movie 1), and it optical SETI is one of the projects of the SETI Institute. Recent papers have scrutinized both the wavelength of photons and even the nature of the particle observed by SETI. It may have taken over forty years since the first publication from Townes discussing masers, but at least proponents of SETI are no longer latching onto the microwave.
Movie 1. Laser SETI Wants Your Money
Laser SETI is an example of the types of searches Townes proposed – something not tied to the microwave region. The optimal wavelength to observe is an important discussion that is still ongoing. | 0.923362 | 3.725842 |
Tiny particles of meteorites with portions of nitrogen and hydrogen. Image credit: Henner Busemann. Click to enlarge
When the Solar System first formed billions of years ago, organic molecules – the building blocks of life – were churned into the mix that went on to create the planets. Scientists from the Carnegie Institution have developed a technique to find these tiny organic particles hidden inside meteorites. These meteorites have survived since the formation of the Solar System, so it allows scientists to track the distribution of organic material and the processes they went through as the planets formed.
Like an interplanetary spaceship carrying passengers, meteorites have long been suspected of ferrying relatively young ingredients of life to our planet. Using new techniques, scientists at the Carnegie Institution’s Department of Terrestrial Magnetism have discovered that meteorites can carry other, much older passengers as well-primitive, organic particles that originated billions of years ago either in interstellar space, or in the outer reaches of the solar system as it was beginning to coalesce from gas and dust. The study shows that the parent bodies of meteorites-the large objects from the asteroid belt-contain primitive organic matter similar to that found in interplanetary dust particles that might come from comets. The finding provides clues about how organic matter was distributed and processed in the solar system during this long-gone era. The work is published in the May 5, 2006, issue of Science.
“Atoms of different elements come in different forms, or isotopes, and the relative proportions of these depend on the environmental conditions in which their carriers formed, such as the heat encountered, chemical reactions with other elements, and so forth,” explained lead author Henner Busemann. “In this study we looked at the relative amounts of different isotopes of hydrogen (H) and nitrogen (N) associated with tiny particles of insoluble organic matter to determine the processes that produced the most pristine type of meteorites known. The insoluble material is very hard to break down chemically and survives even very harsh acid treatments.”
The researchers used a microscopic imaging technique to analyze the isotopic composition of insoluble organic matter from six carbonaceous chondrite meteorites-the oldest type known. The relative proportion of isotopes of nitrogen and hydrogen associated with the insoluble organic matter act as “fingerprints” and can reveal how and when the carbon was formed. The isotope of nitrogen that is most often found in nature is 14N; its heavier sibling is 15N. Differing amounts of 15N, in addition to a heavier form of hydrogen called deuterium, (D), allow researchers to tell if a particle is relatively unaltered from the time when the solar system was first forming.
“The tell-tale signs are lots of deuterium and 15N chemically bonded to carbon,” commented co-author Larry Nittler. “We have known for some time, for instance, that interplanetary dust particles (IDP), collected from high-flying airplanes in the upper atmosphere, contain huge excesses of these isotopes, probably indicating vestiges of organic material that formed in the interstellar medium. The IDPs have other characteristics indicating that they originated on bodies-perhaps comets-that have undergone less severe processing than the asteroids from which meteorites originate.”
The scientists found that some meteorite samples, when examined at the same tiny scales as interplanetary dust particles, actually have similar or even higher abundances of 15N and D than those reported for IDPs. “It’s amazing that pristine organic molecules associated with these isotopes were able to survive the harsh and tumultuous conditions present in the inner solar system when the meteorites that contain them came together,” reflected co-author Conel Alexander. “It means that the parent bodies-the comets and asteroids-of these seemingly different types of extraterrestrial material are more similar in origin than previously believed.”
“Before, we could only explore minute samples from IDPs. Our discovery now allows us to extract large amounts of this material from meteorites, which are large and contain several percent of carbon, instead of from IDPs, which are on the order of a million million times less massive. This advancement has opened up an entirely new window on studying this elusive period of time,” concluded Busemann.
Original Source: Carnegie Institution | 0.811324 | 4.021338 |
An international team of scientists reveals in the journal Nature that the neutron-star merger announced in October has solved one mystery, where gold comes from, but has also raised other questions.
The merger, dubbed GW170817, took place 130 million light-years away and was detected in August by the gravitational waves it created. Astronomers then followed it up with conventional telescopes. The collision’s glowing wreckage generated radio waves, detected by international teams including an Australian one led by Associate Professor Tara Murphy.
Astronomers from the University of Sydney, Caltech, CSIRO and institutions around the world have monitored the merger site for months with three radio telescopes – the CSIRO Australia Telescope Compact Array, the Karl G. Jansky Very Large Array in the USA and the Giant Meter-wave Radio Telescope in India.
“We expected to find evidence that merging neutron stars create something we’ve never found the cause of – short gamma-ray bursts,” Associate Professor Murphy said. These bursts go off every few weeks, in any part of the sky. Each lasts less than two seconds.
“Theorists argued they were caused by colliding neutron stars,” said team member Associate Professor David Kaplan of the University of Wisconsin-Milwaukee. Neutron stars are the cores of regular stars that have exploded and contain about 1.4 times the mass of the Sun.
NASA’s Fermi space telescope detected a burst of gamma rays from GW170817.
To make a short gamma-ray burst you need an ‘ultrarelativistic’ (fast-moving) jet of radio-emitting particles, theoretical models said. So the astronomers monitored the merger site with their radio telescopes for signs of such a jet.
“But we haven’t seen them,” said team member Dr Gregg Hallinan of Caltech. “We haven’t seen a jet, so from the radio data we can’t say there’s a definite link between merging neutron star mergers and short gamma-ray bursts. The jury is still out.”
The astronomers saw the radio glow continuing to brighten more than 100 days after the cosmic crash detected in August. This suggests not an extremely fast jet but a slower, broader outflow of radio-emitting material – a ‘cocoon’ – probably matter thrown out by the explosion that’s been powered up by a jet hidden inside it.
“The cocoon scenario can explain the radio light curve of GW170817 as well as the gamma rays and Xrays. It’s the one most consistent with the data,” Associate Professor Murphy said. But the jet might later emerge from its hiding place and rescue the model, she added.
While they continue to monitor the source the astronomers are puzzling over the ‘cocoon’ they’ve found. “Cocoons may be a common outcome of neutron star mergers,” said Dr Keith Bannister from CSIRO. “Now we know their tell-tale signs we can go looking for them.”
Dr Adam Deller (Swinburne University of Technology and OzGrav) predicts a bright future for the new field of gravitational-wave astronomy. “By tying the information we gather across the electromagnetic spectrum to that gained from the gravitational wave detection, we can learn an enormous amount of detail about events like this one,” he said.
Publication: K. P. Mooley, et al., “A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817,” Nature, 2017; doi:10.1038/nature25452 | 0.86546 | 3.841218 |
Fast, small, cheap, and putting us in touch with the outer reaches of the solar system, the New Horizons spacecraft, which will reach its closest approach to Pluto this month on July 14th, is billed by NASA as the “smart phone” of interplanetary robotic explorers. The fastest spacecraft ever launched from Earth, New Horizons is an example compact, efficient engineering opening the door to new discoveries. This month the probe, launched nearly a decade ago in January of 2006, completes its three billion mile journey, the longest journey ever to a particular object in space.
Besides the technological achievements this plucky probe represents, New Horizons is a step into a new solar system frontier, a glimpse of a region of our own planetary system where we have not yet ventured. The close look at Pluto afforded by this mission is an opportunity for the first time to study the place where the solar system gets weird. Since tiny Pluto was serendipitously discovered in 1930 by Illinois native Clyde Tombaugh, we’ve known that it didn’t quite fit with the rest of the planets. We have small, rocky planets (Mercury, Venus, Earth, and Mars) in the interior of the solar system and large, gaseous planets (Jupiter, Saturn, Uranus, Neptune) on the periphery. Pluto—usually beyond Neptune and much smaller than any other planet—is the odd man out.
Yet it’s only recently that we’ve realized Pluto isn’t alone in its strangeness. Rather, it’s the first known object from a whole new region of the solar system. This region—which is turning out to be filled with small icy objects like Pluto—is known as the Kuiper Belt, and we still don’t know much about it. We do know that Pluto was only the first dwarf planet discovered in this region. Recently Pluto has been joined by the discovery of other dwarf planets beyond Neptune like Eris, Makemake, and Huamea. New Horizons affords the first close look at this strange region of space. Once it passes Pluto, the spacecraft may be redirected to pass another Kuiper Belt object.
Besides the Kuiper Belt, Pluto is itself still an oddity. It will be the first icy planet studied closely, for instance, and may help answer the question of whether certain types of comets are simply objects like Pluto that fall into the inner solar system. Pluto also offers an example of a gravitational oddity: along with its largest moon, Charon, Pluto is technically a double planet. Pluto and Charon orbit a common center of mass between the two objects, making them unique in the solar system by forming a double planet instead of simply a planet and moon.
And then there’s Pluto’s complicated system of newly discovered moons besides Charon. Tiny Nix, Hydra, Styx, and Kerberus have recently been shown to tumble about Pluto in a chaotic system. These miniscule objects have been studied using the Hubble Space Telescope, but New Horizons will provide the first opportunity to study them up close. Indeed, the presence of Pluto’s unexpectedly complex satellite system represents one of the large unknowns of the mission: is the space around Pluto empty or filled with debris that could pose a danger to the speeding spacecraft? The weeks leading up to New Horizon’s encounter with Pluto have been a time of suspense.
New Horizons is a fly-by mission, meaning that it’s not landing on Pluto’s surface (like the Mars rovers) nor is it entering orbit around the dwarf planet (like Cassini around Saturn or Messenger around Mercury). New Horizons will study Pluto from its closest distance of about six thousand miles on July 14th while barreling past the planet at nearly forty thousand mph. It has to be moving fast—it’s had over three billion miles to cover since leaving Earth almost ten years ago.
What sort of things do scientists hope to learn from this mission? For one thing, scientists want to better understand how Pluto “fits in” with the other planets of the solar system. What do its unique properties tell us about the origins and evolution of the solar system? For the first time this month, we’ll get a close look at the strange boundary region of the solar system that we’ve only ever been able to study from afar. As far as the solar system goes, it really is “the final frontier,” and we’ll get our first close views of it this month.
This article first appeared on Friday, July 10th, 2015 in the Kankakee Daily Journal. | 0.860883 | 3.836435 |
With its solar panels their cleanest in years, NASA's decade-old Mars Exploration Rover Opportunity is inspecting a section of crater-rim ridgeline chosen as a priority target due to evidence of a water-related mineral.
Orbital observations of the site by another NASA spacecraft, Mars Reconnaissance Orbiter, found a spectrum with the signature of aluminum bound to oxygen and hydrogen. Researchers regard that signature as a marker for a mineral called montmorillonite, which is in a class of clay minerals called smectites. Montmorillonite forms when basalt is altered under wet and slightly acidic conditions. The exposure of it extends about 800 feet (about 240 meters) north to south on the western rim of Endeavour Crater, as mapped by the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
"It's like a mineral beacon visible from orbit saying, 'Come check this out,'" said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.
Some of the most important findings from Opportunity's long mission came from combining CRISM and rover observations of a site about 2 miles (3 kilometers) farther north on the crater's western rim. Rocks exposed there contain evidence for an iron-bearing smectite - called nontronite -- as well as for montmorillonite. That site yielded evidence for an ancient environment with water that would have been well-suited for use by microbes, if Mars had any billions of years ago.
Evidence that Opportunity may add about the geological context for different smectites could boost understanding about diversity and changes in ancient wet environments on Mars.
Opportunity reached the northern end of the montmorillonite-bearing exposure last month, at a high spot called "Pillinger Point." Opportunity's international science team chose that informal name in honor of Colin Pillinger (1943-2014). Pillinger was the British principal investigator for the Beagle 2 project, which attempted to set a research lander on Mars a few weeks before Opportunity's January 2004 landing.
"Colin and his team were trying to get to Mars at the same time that we were, and in some ways they faced even greater challenges than we did," Squyres said. "Our team has always had enormous respect for the energy and enthusiasm with which Colin Pillinger undertook the Beagle 2 mission. He will be missed."
Though selected as a science destination, Pillinger Point also offers a scenic vista from atop the western rim of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.
A color view of Pillinger Point from the rover's panoramic camera (Pancam) is available at:
Initial measurements at this site with the element-identifying alpha particle X-ray spectrometer at the end of Opportunity's arm indicate that bright-toned veins in the rock contain calcium sulfate. Scientists deduce this mineral was deposited as water moved through fractures on Endeavour's rim. The rover earlier found veins of calcium sulfate farther north along the rim.
As Opportunity investigates this site and sites farther south along the rim, the rover has more energy than usual.
"The solar panels have not been this clean since the first year of the mission," said Opportunity Project Manager John Callas of NASA's Jet Propulsion Laboratory, Pasadena, California. "It's amazing, when you consider that accumulation of dust on the solar panels was originally expected to cause the end of the mission in less than a year. Now it's as if we'd been a ship out at sea for 10 years and just picked up new provisions at a port of call, topping off our supplies."
Both Opportunity and its rover twin, Spirit, benefited from sporadic dust-cleaning events in past years. However, on the ridge that Opportunity has been navigating since late 2013, winds have removed dust more steadily, day by day, than either rover has experienced elsewhere.
"It's easy to forget that Opportunity is in the middle of a Martian winter right now," said JPL's Jennifer Herman, power-subsystem engineer. "Because of the clean solar arrays, clear skies and favorable tilt, there is more energy for operations now than there was any time during the previous three Martian summers. Opportunity is now able to pull scientific all-nighters for three nights in a row -- something she hasn't had the energy to do in years."
The rover's signs of aging -- including a stiff shoulder joint and occasional amnesia events -- have not grown more troublesome in the past year, and no new symptoms have appeared.
During Opportunity's first decade on Mars and the 2004-2010 career of Spirit, NASA's Mars Exploration Rover Project yielded a range of findings about wet environmental conditions on ancient Mars -- some very acidic, others milder and more conducive to supporting life.
JPL manages the Mars Exploration Rover Project for NASA's Science Mission Directorate in Washington. The California Institute of Technology in Pasadena manages JPL for NASA.
For more information about Spirit and Opportunity, visit:
You can follow the project on Twitter and on Facebook at:
News Media ContactGuy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif. | 0.809039 | 3.841214 |
If a star began to eat another star, what would it look like? Natasha Ivanova can tell you better than almost anyone; as the Canada Research Chair in Astronomy and Astrophysics at the University of Alberta, pondering questions like this is her full-time job. Last week, Ivanova and her colleagues published a paper in Science which showed that a certain type of stellar cannibalism previously thought to be invisible can be observed from Earth after all. The finding may explain the existence of the recently-discovered phenomena known as luminous red novae.
Stars are more gregarious that you may realize. Although our beloved sun is typical in size for so-called main sequence stars, it’s somewhat unusual in that it doesn’t have a close companion. “At least half of stars like our sun are in binary systems,” says Ivanova. “For more massive stars, the probability is higher. Stars 20 solar masses and higher are almost all in binaries.” In binary systems two stars orbit their common centre of mass, but over time this orbit can degrade and the stars can move closer together. Moreover, when a main sequence star gets low on fuel it rapidly expands its radius and turns into a red giant, decreasing the distance between it and its neighbour even more. If they get too close, the smaller, denser star (often a white dwarf) can start to steal material from the larger, less dense red giant. As the material (mostly hydrogen) accretes around the smaller star, it is compressed by gravity and eventually explodes into nuclear fusion. The temporary burst of light created from such an event looks like a new star in the sky, and is therefore called a nova (from the Latin for ‘new’).
Ivanova is interested in what happens to stars that are really close together, so much so that at a certain point the white dwarf actually finds itself orbiting within outer layer – called the envelope – of the red giant. These common-envelope events (CEEs) are unstable, as material is transferring to the white dwarf too quickly for it to be able hold onto it all. There are two possible outcomes. The first is for the two stars to merge. The second is more complicated, so I’ll let Ivanova explain: “As the stars orbit, they have orbital energy,” she says. “This is transferred to the common envelope, heating and mixing it up. If the envelope gets enough energy in this way, it can be fully ejected from the system, leaving behind a new binary system.”
The idea of CEEs was proposed decades ago, and there are all kinds of exotic binary systems with thrilling names – X-ray binaries, cataclysmic variables, close double neutron stars – that are thought to be formed by them. But until now, nobody ever thought they’d be able to actually observe a CEE, for two reasons. Firstly, they’re relatively quick, lasting perhaps as little as a couple of months. Secondly, it was thought that CEEs wouldn’t look much brighter than a regular red giant; you might stare right at one and not even notice.
Ivanova and her team upended that theory by considering something called recombination energy. “In stars, the material is usually ionized; the electrons and protons are separated,” says Ivanova. “When they recombine, energy is released in the form of a very energetic photon.” The phenomenon is not unlike that which makes light-emitting diodes (LEDs) work here on Earth. Ivanova and her colleagues worked out that the recombination energy from a CEE would in fact be bright enough to be seen from Earth, most likely in the red part of the spectrum.
So when will we finally be able to see a CEE? As it turns out, we might have been seeing them for years. About a decade ago, astronomers began describing events knows as luminous red novae. As the name suggests, these glow in the red part of the spectrum and are from 10 to 100 times brighter than regular novae, although still much less bright than the spectacular supernovae. They also have other characteristics that are hard to explain, for example their disappearances are often quite sudden. When Ivanova realized that these and other characteristics of luminous red novae matched up with her predictions of CEEs, her heart skipped a beat. “It was kind of a gift,” she says. “It felt pretty good. It was exciting.”
Hunting for luminous red novae/CEEs could help astronomers learn more about the evolution of the exotic binary systems they give rise to. It could even help with the search for ones we could never observe directly, such as double black holes. So far, only a couple of dozen luminous red novae have been found, mostly by sheer luck. “I think now that people know what to look for, we’ll find lots more,” says Ivanova. | 0.868712 | 3.997479 |
Most of us are fascinated by the numerous stars and celestial activities. Think about it, how many times have we spent a good night observing the galaxy and have made imaginative figures joining those twinkling dotted stars? Certainly, several times! Among these awe-inspiring celestial objects, are the planets, and when we try to go into the details of the eight planets, one of them which seems to be most intriguing and much-researched is the planet Mars. The fourth planet from sun after Mercury, Venus and the Earth, Mars and its altering features are often recorded through the telescopic observations. It’s a planet that has been the subject matter of interest of many scientists and scholars for a long time. Many have even speculated the possibility of vegetation and life on Mars; however, the snapshots brought by the Mariner 4 spacecraft in 1965, depicting bleak, cratered surface shocked a large number of people. A perception was made which took Mars as a ‘dead planet’. But human curiosity did not end there, and hence, the reason why so much complexity is associated with this Red Planet, Mars. The mission is still ON across the world! Look at the next part of this article to explore what has been unveiled about Mars so far.
Distance From Sun: 228,000,000 km
Distance From Earth: 55.7 x 106 km (Min) & 401.3 x 106 km (Max)
Mean Radius: 2,439.7 km
Mean Circumference: 15,329.1 km
Volume: 60,827,208,742 km3
Mass: 6.4191 x 1023 kg
Density: 5.427 g/cm3
Surface Area: 74,797,000 km2
Surface Gravity: 3.7 m/s2
Length of Day: 58.646 Earth days
Length of Year (Orbital Period): 0.2408467 Earth years
Number of Moons: 2, Phobos and Deimos
Average Orbit Velocity: 170,503 km/h
Orbit Inclination: 7.0 ˚
Orbit Circumference: 359,976,856 km
Temperature: -87°C to -5°C (Min/Max)
Interesting And Amazing Facts About Mars
- Mars is a small rocky planet about half of the size of the planet Earth.
- Mars received its name from Roman god of war. Egyptians named it ‘Her Desher’ referring to ‘The Red One’.
- Mars has undergone volcanism, impacts, crustal movements, and atmospheric effects such as dust storms just like its neighboring planets Mercury, Venus and the Earth.
- There is no global magnetic field on the surface of Mars. However, some areas in its southern hemisphere are highly magnetized. This effect is believed to be present in the Mar’s crust from about 4 billion years.
- Mars is famous as the ‘Red Planet’ because of its reddish appearance, which it gets due to the presence of iron oxide on its surface.
- Mars has a very thin atmospheric layer which is made up of 95% carbon dioxide, 3% nitrogen, 1.6% argon and traces of water and oxygen.
- Mars surface is covered by a number of craters. Olympus Mons (22 km in height), an extinct volcanic crater, is known to be the highest mountain in the solar system. Olympus Mons is about thrice the height of Mount Everest, the highest mountain on the Earth.
- There’s a huge canyon, known as Valles Marineris, that lies on Mar’s equator. It is believed that it was formed due to possible large rifts in the Mar’s surface. The size of this valley is comparable to the distance between the New York and Los Angeles and is often called as the Martian equivalent of Earth’s Grand Canyon.
- Hellas Basin and Argyre Basin, are the largest and the second largest impact basins on the Mars, respectively. These basins are supposed to be formed when some large objects or asteroids may have hit Mar’s surface some billion years ago.
- Mars is known to have the largest dust storms in the solar system.
- There are significant variations in the temperature on Mars. During the day its temperature reaches as high as -5 ˚C whereas during the night it falls to a minimum of -87 ˚C.
- Mars is less dense than the Earth as it accounts for only 15% and 11% of the volume and mass of the Earth, respectively. However, its surface area is slightly less than the cumulative area of the dry land of the Earth.
- Mars’ moons were discovered by Asaph Hall in 1877.
- These moons, namely Phobos and Deimos, are considerably small with mean radiuses equivalent to 21 km and 12 km, respectively.
- Phobos’ orbit is much closer to Mars than any other known moon of any other known planet. As Phobos is gradually heading towards Mars, scientists believe that either it will crash into the planet or would form a ring around it in the next 50 million years.
- Deimos takes 30 hours to complete one orbit around Mars.
- The crust formation and changes on Mars takes place under Martian tectonism, which is a vertical mechanism with hot lava pushing upwards through the crust to the surface.
- The historic record of capturing first-close up photo of any planet other than the Earth was made when NASA’s Mariner 4 sent 22 photos of Mars back to the Earth in 1965.
- On 3rd September 1976, the U.S. Viking 2 planetary probe landed on the Utopia Basin of Mars.
- In the year 2005, radar data ascertained that poles and regions of mid-latitudes on the Mars had large quantity of water ice.
- The Phoenix spacecraft operated by NASA collected some data according to which Martian soil was found to be alkaline with elements like magnesium, sodium, potassium and chloride. All these elements are known to found in the garden of the Earth and promote plant growth.
- It is believed that because of low atmospheric pressure, water in liquid form cannot exist on Mars.
- The Polar Caps of the Mars have deposits of frozen carbon dioxide, also known as the dry ice, which grows and withdraws during Mars’ seasons. This layer is unique to Mars as no other known planet in the solar system has such a structure where unique spiral troughs are formed due to heating and cooling.
- Due to its elliptical orbit and tilted rotational axis, Mars has varying seasons which last longer than those on the Earth.
- The gravitational force on Mars is such that, here, a 100 pound person would weigh about 38 pounds.
- The geological history of Mars is divided into three periods: Noachian Period (4.5 to 3.5 billion years ago), the Hesperian Period (3.5 to 2.9–3.3 billion years ago) and the Amazonian Period 2.9–3.3 billion years ago to present).
- Scientific studies have suggested that around 3.5 billion years ago, Mars experienced the largest known floods in the solar system. | 0.892082 | 3.21139 |
Grab your telescope. The asteroid known as Toutatis will make its closest approach to Earth tonight.
From Tuesday night to Wednesday morning, the 3-mile long asteroid will be about 18 times the distance of the moon from the Earth.
And if you miss it Tuesday night, don’t worry. The asteroid should be visible if you have the right conditions, the right telescope and a good star chart -- through the end of the week.
Even at its closest approach you won’t be able to see Toutatis with the naked eye. You’ll need a small telescope. Of course, even if you find it, it will still appear as a small point of light moving across the night sky.
To see what this asteroid really looks like, you’d need something really, really big, such as the Goldstone Radar, which looks like a whopping satellite dish 230 feet across.
Scientists who work at the Goldstone facility near Barstow have been tracking Toutatis since Dec. 4 and posting images of the asteroid on the Internet. The images are a little fuzzy, but they give you a sense of the asteroid’s oblong shape and its lumpy topography.
Lance Benner, a Jet Propulsion Laboratoryresearch scientist, said the asteroid is rotating very slowly and that at 3 miles long it is one of the bigger objects that have come within 18 lunar distances of the Earth. But he wouldn’t consider it humongous or gigantic.
Since Toutatis’ erratic orbit takes it by Earth once every four years, scientists have been able to study it pretty closely since it was rediscovered (and named) in 1989.
As for the all-important question of whether Toutatis’ orbit will ever put it on a collision path with Earth, Benner said it is unlikely.
“There is no risk of it colliding with Earth” for hundreds of years, he said. But Benner can’t predict hundreds of thousands of years into the future.
Still, he is not worried that Toutatis will ever collide with Earth.
“Almost 9,400 asteroids have been found so far, and none of them have a significant chance of hitting us,” he said. “It’s the ones we haven’t found yet that are of greater concern.” | 0.84006 | 3.169552 |
The basic building blocks of life may have been present on Earth from the very beginning.
Astronomers detected 21 different complex organic molecules streaming from Comet Lovejoy during its highly anticipated close approach to the sun this past January. Many of these same carbon-containing compounds have also been spotted around newly forming sunlike stars, researchers said.
"This suggests that our proto-planetary nebula was already enriched in complex organic molecules (as disk models suggested) when comets and planets formed," study lead author Nicolas Biver, of the Paris Observatory, told Space.com via email. [7 Theories on the Origin of Life]
Biver and his colleagues studied Comet Lovejoy with the Institut de Radioastronomie Millimétrique's 100-foot-wide (30 meters) radio telescope in Spain during two separate three-day stretches in January 2015. That's when the spectacular, green-hued comet was making its closest approach to the sun.
At the time of the observations, Lovejoy was about 0.6 astronomical units (AU) from Earth and 1.3 AU from the sun, researchers said. (One AU is the distance from Earth to the sun, about 93 million miles, or 150 million kilometers.)
The sun's heat drove a great deal of material from the comet's surface out into space; indeed, Lovejoy was one of the most active comets to cruise through Earth's neighborhood since the superbright Hale-Bopp in 1997, the researchers write in the new study, which was published online today (Oct. 23) in the journal Science Advances.
Biver and his team spotted 21 different complex organics in the cloud of material surrounding Lovejoy, including two — ethyl alcohol and the simple sugar glycolaldehyde — that had never been seen in a comet before.
The researchers also calculated the abundances (relative to water) of each type of organic molecule, and compared these abundances to those of organics observed in Comet Hale-Bopp and around two "protostars" by other research teams.
Overall, organics are quite abundant in comets — often more abundant, in fact, than they are around newly forming stars. This result is "in line with their [organics'] synthesis through grain-surface reactions and ice irradiation in the early solar nebula," Biver and his colleagues wrote in the study.
Modeling work suggests that the solar system's four biggest planets — Jupiter, Saturn, Uranus and Neptune — migrated significantly in the solar system's early days. Some of these dramatic movements likely sent huge numbers of comets careening toward the realm of the rocky planets, which includes Earth and Mars, 4 billion years ago or so.
"So even if Earth was born dry and depleted of volatile elements, complex organics formed further away may have been supplied in large amount via comet nuclei early and certainly contributed to the emergence of more-complex molecules and ultimately life," Biver said. | 0.883554 | 3.905865 |
DrümPublished in August 2012
Going to the Moon, which is almost 400,000 kilometers away, or sending satellites to explore other planets may seem harder than investigating the Earth’s interior. Earth is only 12,000 km in diameter, but boreholes have only reached 12 km deep, hardly penetrating the crust, the outer layer of the Earth just beneath the surface. Because scientists cannot directly examine the interior of the planet, they are using computer simulations to understand how minerals behave and transform in the deepest layers of the Earth, where pressures and temperatures are much higher than those on the surface. Computations have identified minerals formed thousands of kilometers below the surface, and there may be a volume of water larger than an ocean dispersed in the thick mass of rocks under our feet.
Brazilian physicist Renata Wentzcovitch, a professor at the University of Minnesota in the United States, is responsible for fundamental discoveries about the interior of the planet. Since 1990, she has been developing analytical and computational methods to model deep-Earth structure and processes, especially in the lower mantle, the largest layer of the Earth. The lower mantle is a 2,200 km thick layer and much less understood than the other layers of the mantle (see infographics below on the layers of the Earth’s interior). In 1993, she shed light on the atomic structure of perovskite at high pressures. Perovskite is the most abundant mineral in the lower mantle (~75% vol) and its properties are essentially responsible for the properties of this large layer still not well understood.
In 2004, Wentzcovitch and her team identified post-perovskite, a mineral that results from the transformation of perovskite under pressures thousands of times greater than those on the surface. Their results helped explain the speed of seismic waves throughout the deepest part of the mantle. Seismic wave speeds depend on the density and elastic properties of rocks they travel through and three dimensional velocity maps are widely-used for investigating the nature of Earth’s interior. New studies by Wentzcovitch and her team have now indicated that post-perovskite tends to break down into elementary oxides, such as magnesium oxide and silicon oxide when pressure and temperature increase way beyond those reached in the Earth’s interior, as those found in the interior of giant planets Jupiter, Saturn, Uranus, and Neptune.
“We have powerful computational tools for discovering the mineralogical make up of planetary interiors”, she says. According to Wentzcovitch, the techniques she pioneered can forecast the behavior of complex crystalline structures, such as those of silicate perovskite with 20 atoms per unit cell. “The crystalline structure of minerals change with depth in the Earth’s mantle but its chemical composition seems to be uniform, except perhaps in the deepest regions of the mantle above the core mantle boundary.”
DrümThis kind of research helps us to understand how minerals deep in the Earth become denser and harder. Pressure and temperature increase with depth, so we expect the greatest density in the Earth’s center. Research has shown the Earth’s core is a layered mass of iron, the outer part being liquid while the inner is solid. Temperatures in the core are close to 6,000°C and density there is almost 13 grams per cubic centimeter, twice greater than the density of iron on the surface.
Without resorting to fiction, physicists, geophysicists, and geochemists are opening up the planet and expanding our knowledge about the compacted, rocky region below 600 km. Laboratory experiments have helped us understand the upper layers, the upper mantle, down to 410 km depth, and the transition zone, from 410 km to ~ 660 km. However, much less is known about the Earth below the transition region. Scientists are now making extensive use of computer simulations of rock properties, seismic wave propagation, and geodynamic flow in the Earth in addition to laboratory experiments and geological surveys to understand Earth’s interior structure and processes and perhaps one day predict surface processes such as earthquakes and tsunamis.
New facts are emerging that are calling into question the image of the interior of the planet as a sequence of regular, onion-like layers. In 2003, detailed global surveys began to show irregularities in the thickness of the crust. It varies between 20 and 68 km, leaving the thinner regions more subject to earthquakes and the thicker ones to collapse.
“We began to see the interaction of the crust and the region of the mantle closer to the surface,” commented geophysicist Walter Mooney of the United States Geological Survey (USGS) at the “Frontiers in Earth Science” meeting that was held in June at the University of São Paulo (USP). Geophysicists are reexamining the possible consequences of two phenomena that occur within the crust. The first is the diving of tectonic plates (movable and rigid pieces of the lithosphere, the surface layer that includes the outermost region of the mantle) into deeper regions of the mantle, increasing the risk of earth tremors in the regions where they occur. The data confirm the conclusions of a recent study coordinated by Marcelo Assumpção, a professor at the Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG) at USP. Assumpção, in collaboration with researchers from the University of Brasília, found that earth tremors in Brazil occur most frequently in regions where the crust and the lithosphere are thinner and, therefore, more fragile.
The entry of water into the lithosphere, below the crust, is another phenomenon being detailed. This phenomenon is intriguing: water cannot be stored in the lower crust because the pressure caused by the layers of rock and the temperature (almost 205°C) would cause the water to quickly evaporate. In fact, what is present in the Earth’s interior is not exactly water but the components of the water molecule—hydrogen and oxygen—linked to the crystalline structure of minerals in the form of H2O or OH.
Mooney and his team detected an intense aquatic intromission in regions of the Andes, where the crust is as much as 65 km thick, but they were unable to explain why. Speaking to colleagues from various countries at USP, Mooney asked, “Where is this water stored? What is the volume of the water? Perhaps,” he noted, “the water comes from tectonic plates that sink or separate.” The specialists have determined that the lithosphere without water is geologically older, whereas the hydrated lithosphere is more recent, indicating that hydration may contribute to the formation or transformation of the outer layers or even of the deeper mantle, closer to the core.
Water molecules are important because, “even in minute proportions, such as 0.1%, they can change the viscosity of materials and therefore the view of the circulation of matter and energy in the interior of the Earth,” comments physicist João Francisco Justo Filho, a professor at USP’s Polytechnic School who has been working with Renata Wentzcovitch since 2007. “A great amount of water may be hidden in the lower mantle in minerals,” says geochemist Francis Albarède, from the Lyon École Normale Superieure, in France. “Perhaps the equivalent of a whole ocean,” he adds. Or “perhaps several oceans” ponders Wentzcovitch. Using computational methods, she began to examine the possibilities of two atoms of hydrogen substituting for the magnesium linked to oxygen and forming units of H2O. “The more we looked, the more we found defects in the crystalline structures, where the hydrogen could enter,” she says. The problem is that it is not known how much hydrogen may be stored in the mantle.
DrümLower down, the uncertainties increase, given the impossibility of accurately measuring what happens at depths of 6,000 km. Little is known about the composition of the Earth’s core, which is so dense as to concentrate 30% of the planet’s mass in two regions: one external, which is molten, and the other internal, which is solid and where the temperature may exceed 6,000°C. A team from University College London used the same conceptual approach as the group from Minnesota, density functional theory, to estimate the intensity of the heat flow that comes from the boundary region between the core and the mantle, based on the amount of iron, oxygen, sulfur and silicon as suggested by the speed of the seismic waves that cross the core and by the flow of heat from the lower mantle. The results, published in May in Nature, indicate that the heat flow that emanates from the core must be two or three times greater than previously estimated. Where this energy goes, no one can yet say.
Many ongoing studies are concentrating on the mantle, a thick, solid, slightly flexible layer that deforms very slowly, like pitch. Only rarely, when magma emerges from volcanoes, bringing material from the mantle, are studies carried out indirectly, by monitoring the speed of the seismic waves, because it is difficult to directly study what happens in the mantle. The Japanese want to beat the current 12 km drilling record and reach the mantle by using a ship with a drill similar to an oil drill. The mission, announced in July in New Scientist, will not be easy: the material for the drill bits to be used for drilling through the crust and reaching the mantle has to resist pressures 2,000 times greater than on the surface, as well as temperatures close to 900°C, a task similar to the plan to extract oil from the pre-salt layer off the coast of São Paulo.
“I cook rocks to understand how they were formed,” says geologist Guilherme Mallmann, a researcher from the Institute of Geosciences at USP, who has adopted another method for getting to know the interior of the planet better. He submits the chemical components that constitute the minerals to high pressures and temperatures in the laboratory. Furnaces and presses like the ones he uses, however, only allow him to reproduce phenomena that take place up to 150 km down, the region of the upper mantle in which the magma that sometimes emerges via volcanoes is formed. The pressure conditions at a greater depth in the Earth’s interior may also be achieved experimentally, according to Mallmann, but it is far more difficult. Because pressure is the result of the force on an area, the volume of material analyzed would have to be greatly reduced to achieve these extremely high pressures. “Producing greater pressures is often unfeasible.”
Perovskite, named in honor of Russian mineralogist Lev Perovski, is formed in environments under high pressures and temperatures, which in the lower mantle may vary from 23 to 135 gigapascals (1 gigapascal is approximately 10,000 times greater than the pressure on the Earth’s surface) and 2,000°C to 4,000°C, respectively. Wentzcovitch presented the crystalline structure of this mineral (a silicate of magnesium and iron) in 1993 in Physical Review Letters using green and yellow rhombuses reminiscent of the Brazilian flag. The reason was simple: “I miss the country,” says the researcher, who lives in the twin cities of Minneapolis-Saint Paul, which have 2.5 million inhabitants and are close to the border with Canada, where the temperatures in winter can remain at – 20°C for weeks at a time.
In collaboration with physicists from Italy and Brazil, Wentzcovitch found that the iron atoms of a mineral called ferropericlase, the second most abundant mineral in the lower mantle, lose one of their magnetism, thus explaining a phenomenon that has been observed in the laboratory. In 2007, João Justo worked in Minnesota with Wentzcovitch and developed a series of equations that establish the change in elastic properties and seismic speeds during the loss of magnetism in ferropericlase.
“The size of the iron atom decreases when it loses the magnetic moment, and this is what makes the ferropericlase denser. Furthermore, minerals with iron soften during the slow densification process, as has already been observed in the laboratory, but has not yet been explained,” says Justo. This is a surprising phenomenon because the material normally becomes harder as it becomes denser.
The results that he and Wentzcovitch obtained were published in 2009 in the journal PNAS. Their results explained the loss of magnetism under pressures and temperatures equivalent to those in the lower mantle, which James Badro, from the Universities of Paris 6 and 7, had detected in the laboratory and reported in Science in 2003 and 2004. Experimental verification of this phenomenon, one of the great discoveries of geophysics in the last few years, indicated that the proportion of non-magnetic iron may increase with depth. What is more, the deeper layers of the lower mantle may be even denser than the shallower layers.
As a child, Renata Wentzcovitch enjoyed the math tests that her grandfather, Adolfo Foffano, used to give her every day when they were together during her end-of-year vacations in Sumaré, in the State of São Paulo. She studied physics at the University of São Paulo and then began studying at the University of California at Berkeley in the United States in 1983, on the recommendation of José Roberto Leite and Cylon Gonçalves da Silva.
Wentzcovitch’s journey included a stay in Cambridge, in the UK, and London from 1990 until 1992 after she had broadened the applicability of her material simulation techniques. Her new techniques were so general that they served to study the atomic movement and transformations of crystalline structures at high pressures and temperatures. To do this, she used so-called first-principles calculations, based on the density functional theory, whose essence is simple: the total energy of a group of electrons in their state of equilibrium depends on the total electron density.
Her hard work eventually paid off. “In less than a month, using my techniques, I’d solved the structure of magnesium silicate at high pressure, which researchers at Cambridge had been working on for two years,” she says. Solving a structure, she explains, “means identifying the position of equilibrium and the degrees of freedom of a crystalline structure with a certain symmetry that minimize the internal energy.” Until then, it was only possible to easily determine structures such as that of diamond, which is formed by two atoms at the base and has a degree of freedom that is reflected in the distance between the carbon atoms. The structure of perovskite has 20 silicon, magnesium and oxygen atoms and 10 degrees of freedom. “It is much more complex than the structure of semiconductors, and that’s why its behavior at high pressures was unknown until then,” she says.
In the beginning, one of her problems was that she was unable to check her theoretical forecasts experimentally. However, in 2003, while working with researchers from the Tokyo Institute of Technology, Wentzcovitch and her team from Minnesota analyzed the spectrum of X-rays, which differed greatly from what was expected at very high pressures. They concluded that a phase transformation had occurred (or a change in the crystalline structure) to an unknown structure. “At first I didn’t believe it,” she says, “because perovskite seemed so stable!” The following year, an article in Science presented the new crystalline structure, christened post-perovskite. Today, post-perovskite is recognized as the most abundant material in the region of the mantle known as D”, which is in contact with the outermost layer of the Earth’s core. “Post-perovskite explains many geophysical characteristics of this region of the Earth,” observed Mallmann, from USP.
Post-perovskite has a layered structure, through which seismic waves travel at speeds that depend on their initial direction. This work reinforced the conclusion of other studies that had indicated that this mineral could be formed at different depths in the lower mantle.
In a report published in Science on March 24, 2004, physicist Surendra Saxena, from the International University of Florida, challenged the conclusions and said that he still believed that perovskite decomposes only in those regions of the mantle closest to the core, and he reiterated that the theory was still not perfect. Subsequent studies on the propagation of seismic waves, however, seem to confirm the presence of post-perovskite in region D”. “We’ve been very lucky,” Wentzcovitch commented. “The results of the computational calculations of speeds in post-perovskite are surprising because they reproduce many seismological observations of D” inexplicable until then. It can’t be mere coincidence.”
It was also in 2004, when this work began to circulate, that Wentzcovitch received funding of US$ 3 million from the National Science Foundation of the United States to assemble the Virtual Laboratory of Planetary and Earth Materials (VLab) at the Supercomputing Institute of the University of Minnesota. The VLab brought together chemists, physicists, computational scientists, geophysicists and mathematicians who, motivated by the possible existence of post-perovskite on other planets, began to look at the probable transformations that minerals could undergo at even higher pressures and temperatures inside the giant planets in the solar system (Jupiter, Saturn, Uranus and Neptune), which have masses at least 10 times greater than that of the Earth.
The results of her group, like those detailed in Science in 2006, presenting the probable transformations of magnesium silicate in the giant planets closest to Earth, indicated that these calculation techniques might be useful for studying the evolution of planets. “The behavior patterns of minerals on different planets cannot be just a coincidence,” she commented to an audience that listened attentively to her during the seminar at USP.
Simulations of the behavior of materials at great depths and experimental studies, principally when they coincide, help clarify phenomena in the interior of the Earth. In July, French researchers announced that they had managed to re-create the environmental conditions at the limit of the outer core and lower mantle in the laboratory. They showed, by means of X-ray analyses, that partially molten rocks, when submitted to high temperatures and pressures, may move toward the surface of the Earth, giving rise to volcanic islands, such as those of Hawaii.
A more real Earth
The new information about the interior of the planet is being used in the work of Brazilian research groups in basic geophysics at São Paulo, Rio de Janeiro, Rio Grande do Norte and the Federal District who are focusing on examining the Earth on a large scale. More broadly, this information is useful to the applied geophysics teams that are working with oil, mining and underground water in Bahia, Pará, Rio, São Paulo, Rio Grande do Norte, the Federal District and Rio Grande do Sul.
Taken together, the results help construct a more solid picture of the Earth, which has been represented in many ways over the past few centuries. Knowledge of the structure of the Earth’s interior has greatly advanced since 1912, when German geophysicist Alfred Wegener concluded that the Earth is likely formed of rigid plates that move, and our understanding is moving increasingly farther away from the poetic images of Journey to the Center of the Earth, the magnificent work by French writer Jules Verne, published in 1864. “Today, we know that the center of the Earth, unlike the version described by Jules Verne,” Justo guarantees, “is absolutely mysterious and certainly uninhabitable.” “But that’s no reason for our planet to be any less fascinating,” says Assumpção. N
Simulation and modeling of minerals at high pressures no. 09/14082-3 Modality Thematic Project Coordinator João Francisco Justo Filho – USP Investment R$ 184,378.73
Wentzcovitch, R.M. et al. Ab initio molecular dynamics with variable cell shape: Application to MgSiO3. Physical Review Letters. v. 70, p. 3.947-50. 1993.
Tsuchiya, T. et al. Phase transition in MgSiO3 perovskite in the earth’s lower mantle. Earth and Planetary Science Letters. v. 224, n. 3-4, p. 241. 2004.
Wentzcovitch, R.M. et al. Anomalous compressibility of ferropericlase throughout the iron spin crossover. PNAS. v. 106, p. 8.447-52. 2009. | 0.853635 | 3.928444 |
VY Canis Majoris
VY Canis Majoris (VY CMa) is a red hypergiant star in the constellation Canis Major. It is about 1.2 kiloparsecs (3,900 light-years) distant from Earth. It is the largest known star in the universe, and one of the most luminous of its type.
VY Canis Majoris is 1,420 times wider than the Sun. If placed at the center of the Solar System, VY Canis Majoris's surface would extend beyond Jupiter's orbit. Other estimates of the radius make it larger than the orbit of Saturn.
VY CMa is a single star, a "semiregular" variable with a period of about 2,001 days. It has an average density of 5 to 10 mg/m3.
- Wittkowski M. et al 2012. Fundamental properties and atmospheric structure of the red supergiant VY CMa based on VLTI/AMBER spectro-interferometry. Astronomy & Astrophysics 540: L12.
- Massey, Philip; Levesque, Emily M.; Plez, Bertrand (2006). "Bringing VY Canis Majoris down to size: an improved determination of its effective temperature". The Astrophysical Journal. 646 (2): 1203–1208. arXiv:astro-ph/0604253. Bibcode:2006ApJ...646.1203M. doi:10.1086/505025. | 0.910413 | 3.291208 |
In the past two decades, scientific and technological advances driven by research into astronomy and space have revolutionised our understanding of, and capacity to explore, the universe. Astronomers observe the universe ever more deeply, and space offers a limitless frontier for us to explore our cosmic past, present and possible future.
While the ancient question of life beyond Earth remains unanswered, it can be addressed more effectively thanks to developments in astronomical and space technology. In the past two decades thousands of planets have been discovered orbiting stars other than the Sun, and it is estimated that billions of planets in our Galaxy could be capable of supporting life.
The search is on
A global search is on to find and remotely explore the most likely exciting planets orbiting our nearest stars; key to this global pursuit is USQ’s Mt Kent Observatory.
In conjunction with northern-hemisphere partners including the Harvard-Smithsonian Center for Astrophysics and University of Louisville, researchers in both hemispheres are exploring the sea of space in search of Earth’s sister planet. A long-term survey using the 3.9m Anglo-Australian Telescope has enabled USQ researchers to collaborate with teams in Australia, Europe, and the United States (including the Carnegie Institution for Science) to find over forty planets.
The clearer picture such studies provide of the evolution of stars and their planets is allowing us to learn more about the potential for exoplanetary habitability. This same knowledge is also helping USQ PhD students to be at the forefront of ongoing planet discovery work to explore from afar the many worlds around the stars of our night sky. | 0.86447 | 3.152194 |
Surf’s up on Jupiter’s moon. Magma waves travelling both clockwise and anticlockwise have been spotted on the surface of a lava lake on Io, the most volcanically active body in the solar system.
The lake, called Loki Patera, is a bowl-shaped volcanic crater on Io, Jupiter’s innermost moon. It is roughly 200 kilometres across, and responsible for 10 to 20 per cent of the heat that the jovian moon puts out.
We’ve known that Loki periodically brightens and dims since the 1970s. Previous observations suggested that these changes are due to the lake recycling itself. As the top layer of lava cools, it solidifies and grows dense, until eventually it sinks beneath the underlying magma and pulls nearby crust with it in waves moving across the surface.
But most of those observations, based on a technique for reducing atmospheric blurring called adaptive optics, were only sharp enough to tell which direction the waves were moving, not how fast or where they started.
Now, Katherine de Kleer at the University of California, Berkeley and her colleagues have taken advantage of a rare collusion between Jupiter’s moons to get a high-quality time lapse of the lava lake’s surface.
(Time-lapse images of the lake’s surface reveal how its surface regenerates)
Every six years, the orbits of Io and Europa – a moon of Jupiter best known for its ice shell covering a liquid water ocean – align, then cross one another from the point of view of Earth.
On 8 March 2015, de Kleer and her colleagues turned the Large Binocular Telescope Observatory in Arizona on the criss-crossing moons to observe the heat coming from Loki Patera in unprecedented detail.
By combining adaptive optics with the binocular observations, they were able to make a map of changing temperatures over time across the lava lake surface with 10 times better spatial resolution than previously possible. “People have looked at Io with each of these methods, but not together,” de Kleer says.
Knowing the temperature of different parts of the lake and how fast the magma cooled and sank helped de Kleer’s team decipher which parts of the surface recycled at which times.
Surprisingly, the temperature map revealed not one, but two waves, one clockwise and the other anticlockwise, moving from the west to the southeast of the lake. The waves started at different times and ran around a cool island in the lake’s centre.
“It’s a giant bowl of molten rock; it should all be behaving the same,” says Julie Rathbun at the Planetary Sciences Institute in Tuscon, Arizona. “But having two waves suggests there are compositional differences within the lake, and that’s strange.”
De Kleer thinks understanding how new magma is exposed on Loki Patera’s surface can offer insight into volcanism on planets and moons that are different from Earth. Io is in an almost constant state of eruption, but it lacks the plate tectonics that are responsible for much of our own planet’s volcanic activity. Instead, its volcanoes are largely driven by tidal heating from Jupiter’s enormous gravity.
It could also shed light on subsurface oceans on moons like Europa and Saturn’s Enceladus, which are also probably kept warm by tidal heating.
“The same process might lead to volcanic activity at the bottom of those oceans that injects the raw materials that would make these systems able to host life,” de Kleer says. “Understanding how heat is deposited in and transported through satellite interiors is therefore important for understanding the potential habitability of these other worlds.” | 0.847339 | 3.992908 |
Cassini ISS (Image Science Subsystem) images have been taken as an important resource for astrometry of planetary Satellites. For example, Cooper2006Cassini; Cooper2014 derived some positions of the inner Jovian satellites from ISS images, and have done the astrometry of mid-sized Saturnian satellites from ISS images of mutual events. Tajeddine2013Astro; Tajeddine2015Cassini reduced some observations of the main icy saturnian satellites. Zhang2018First; Zhang2019Astro reduced some ISS images of Enceladus and Helene. Moreover, the shape and size of the Saturn and its satellites have also been obtained from ISS images, which are crucial to analyze their interior structure (Kong201838; Kong201839; Kong201850).
The astrometry of CCD images includes the geometry distortion correction (Peng2017), and matching reference stars (Liu2018), but they have the same prerequisite: no false detected image star. In most cases, the Saturn and its satellites are disk-resolve objects in the ISS images, which will bring some false detected image stars in the disk. Hence, detecting the contour of the disk-resolved object is important to remove false image stars. In addition, the Cassini space probe has captured more than 400,000 astronomy images, most of which require using contour detection to analyze. Thus, the speed of the contour detection algorithm is also one of the important factors considered in practical applications.
Based on different application purposes and different image conditions, researchers often use different contour detection methods, which can be divided into four categories:
Traditional edge detection operators such as Canny, Roberts and so on. For example, Saheba2016Lunar used improved adaptive Canny algorithm to detect lunar surface crater. Cornet2012Edge used an image gradient-based method to compare the contours of the Ontario Lacus to examine the displacement of the lake within five years;
Methods driven by information theory based on well-designed features, such as the Statistical Edges method based on probability distribution (Konishi2003Statistical), Pb method (Martin2004Learning), gPb method (Arbelaez2011), etc.;
Deep neural network-based methods. For example, Farabet2013 constructed a multi-scale deep convolutional neural network to implement pixel-wise classification of objects in natural images. Xie2017HED proposed an end-to-end edge detection network called Holistically-Nested Edge Detection (HED).
Most of the current research focuses on the latter two categories, namely, using machine learning and deep learning techniques for contour detection. However, most of them only use natural images or other specific domain images (medical images, sensing images, etc.) as training sets. Unlike these images, Cassini ISS images have their own properties that some stars appeared as white point sources scattered in the black background and disk-resolved target has a sharply changed gray distribution to some extent. Thus, when these techniques are applied to Cassini ISS images, a large number of error detections are often caused. In addition, the training of deep neural networks often requires a lot of computing resources and time so that it may not be the best choice in practical applications. Therefore, how to accurately and quickly detect the contour of a disk-resolved object in ISS image is still a problem to be solved.
Based on our previous research (Yang2018
), a new method based on Hierarchical Extreme Learning Machine (H-ELM) and Dense Conditional Random Field (DenseCRF) is proposed for the contour detection of Cassini ISS images. Our method combines unsupervised learning with supervised learning, using H-ELM algorithm to train a contour pixel classifier while using DenseCRF algorithm to perform back-end optimization on the contour detection results. Experiments show that our method can achieve higher accuracy and faster training speed compared with some traditional machine learning methods and even deep convolutional neural networks.
2 Contour detection method in ISS images based on H-ELM
The essence of the contour detection method in ISS images based on H-ELM is to classify all the pixels in the Cassini image into two types using the best trained H-ELM model. The two types are contour pixels (denoted by 1) and non-contour pixels (denoted by 0). The overall process is divided into six parts: image preprocessing, feature selection, H-ELM network construction, network training, classification using the trained model, and back-end optimization. The key in our method is the construction and training of the H-ELM network.
2.1 Image preprocessing
In order to reduce the noise signals in an ISS image, preprocessing is required to perform before contour detection. In this paper, we use morphological transformation (erosion and dilation) to improve edge connections while using bilateral filtering to reduce noise and preserve edges.
2.2 Feature selection
Feature selection is an important step before the model training. Appropriate feature selection can make the classifier more robust. In our experiments, 34 candidate features are designed, including image gray level, Hessian feature, Kirsch operator, Robinson operator, Sobel operator, LoG operator, gradient operators, Harr-like operators and so on. Based on some common senses and some experiments, we finally select the combination of features which has the best average performance (accuracy) of the model as the feature set, namely 28 features of 3 types listed below.
2.2.1 First-order gradients
First-order gradient is commonly used in edge detection. In this paper, we extract the first-order gradient (i=1,2,…,8) in eight directions of each pixel within its 5 neighborhood. Figure 1 shows a pixel’s eight directions and its neighborhood. In every direction i, we take the difference of greys between each pixel pointed by arrow and center pixel as . Moreover, the ninth feature of a pixel is gradient amplitude that is calculated as follows:
2.2.2 Second-order gradients
Regarded the image as a two-dimensional discrete function, the second-order gradient is the rate of change of the gradient of the image, which can further show the edge information in the image. Unlike traditional second-order gradient, we perform the second-order derivatives in eight directions within 55 neighborhood of one pixel (illustrated in Figure 1). In addition, the amplitude of second-order gradient is also calculated like Equation (1).
2.2.3 Haar-like feature
Haar-like feature is a simple rectangular feature similar to Haar wavelet, proposed by Viola2001; Viola2004; Lienhart2002. There are four kinds of Haar-like features: line features, edge features, center-surround features, and diagonal features (see Figure 2). Haar-like feature can effectively show the local grayscale change in the image, and can also be calculated fast using integral image.
In this paper, line features and center-surround features are selected. The line features (Figure 2(2a)-(2b)) are calculated in 23 and 24 region, respectively. Then they are rotated at 45 and 90 to form new features (Figure 2(2c)-(2h)). One of the center-surround features (Figure 2(3a)) is obtained by an operator with the window size of 33; the other (Figure 2(3b)) is calculated in the 45 rotation of same region. Finally, 10 Haar-like features are extracted for each pixel.
So far, this paper has extracted 9 first-order gradient features, 9 second-order gradient features, and 10 Harr-like features. That is, we use a 28-dimensional feature vector to describe a pixel.
2.3 Hierarchical Extreme Learning Machine
2.3.1 Extreme Learning Machine
Extreme Learning Machine (ELM) is a single-hidden-layer forward feedback network proposed by Huang2006
. In this network, the input weight and hidden layer biases are randomly generated, and the output weight is obtained by solving regularized least squares optimization. Therefore, there are only two parameters that need to be set: the number of hidden layer neurons and the activation function. Compared with the traditional machine learning algorithm and the deep neural network, it has faster training speed and more flexible parameter selection. Nowadays, ELM has demonstrated its awesome performance in many fields (Tang2015; Mcdonnell2015; Minhas2010).
The structure of ELM is shown in Figure 3 and the steps of ELM algorithm are as follows:
Extract label matrix T from training data
Randomly generate input weight and hidden layer bias of hidden layer neurons (i=1, 2,…, N)
Compute the output matrix H of the hidden layer (This paper uses the sigmoid activation function)
(3) (4) (5)
According to the principle of least squares, the output weight can be calculated according to H and T
Compute the class probability of each pixel
2.3.2 Hierarchical Extreme Learning Machine
Although ELM has good generalization performance and approximate global approximation ability, single-hidden-layer ELM is generally used to solve simple classification problems without the feature learning and self-organization ability. Even if deep neural network has the feature learning and self-organization ability, it needs to adjust the network frequently based on the BP principle so that the training takes a long time and the parameter adjustment depends on the quality and quantity of the training samples.
proposed H-ELM, which is improved on the basis of the original ELM, adding a sparse encoding layer for unsupervised feature extraction, and then using ELM for supervised classification. It not only inherits ELM’s fast classification ability, but also has excellent generalization performance, thus is suitable for classification of data with multi-dimensional features, such as images.
The H-ELM network structure used in this paper is shown in Figure 4
, which is divided into two parts: (1) Multi-layer forward encoding part, including 2 hidden layers, using the sparse autoencoder to extract the feature layer by layer, which is the unsupervised learning phase; (2) The original ELM part, including a hidden layer, classifying according to the extracted features, which is the supervised learning phase.
The sparse autoencoder makes the encoded output fit the input raw data by minimizing the reconstruction error (Tang2016). Thus, once the output weight of the autoencoder is obtained, it can be multiplied with the input data (i.e. feature vectors) to derive features’ compact form.
After encoding the feature vector of each pixel by using the sparse autoencoder, it will be input into the original ELM model to obtain the class probability of this pixel.
3 The back-end optimization method based on DenseCRF
H-ELM can provide a set of contour pixels for each image, but the result is somewhat far from ideal. Refining the result is necessary. In this paper, we use the DenseCRF to finish the back-end optimization.
The Conditional Random Field (CRF) is a kind of conditional probability distribution model, which can convert a set of random variables into another set of random variables, and the output variables form a Markov random field (Lafferty2002).
Theoretically, CRF can also be used to learn the conditional distribution of each pixel’s class. However, in the contour detection problem, each pixel in the image is related to each other. For example, the pixel close to the contour pixel is more likely to be the contour pixel than the pixel far away from the contour pixel. Therefore, they will form a very dense full connected graph, whose amount of computation is large. Since DenseCRF proposed by Philipp2011 can reduce the computational complexity to sub-linearity, this paper uses DenseCRF for back-end optimization instead.
By minimizing the energy function, DenseCRF estimate the posterior distribution of the results according to the class probability predictions of the H-ELM network and the grayscale information of the image itself, thus making the contour prediction results more accurate.
4 Dataset preparation
We pick out 200 ISS images to train and test our method. Every image’s size is 512512, and has one disk-resolved object. All the images show some typical features of ISS images. 130 of them are used to train our H-ELM, and 70 of them are used to test our method. The data preparation includes two steps: semi-automatic labeling and sample equalization.
4.1 Semi-automatic labeling
In this paper, the training and testing images are semi-automatically labeled by combining Canny operator with manual annotation. Firstly, Canny operator is used to detect all the edge pixels in the image. Then the non-contour pixels are manually removed. Finally, check whether there are contour pixels unmarked by Canny operator, if there are, label them manually.
4.2 Sample equalization
After sample labeling, the samples are divided into two classes: positive samples (contour pixels) and negative samples (non-contour pixels). Without further processing, the proportion of positive and negative samples is as high as 1:400, which is obviously unbalanced.
For the data imbalance problem, common solutions include under-sampling, over-sampling, using cost sensitive factors (Barandela2004; Chawla2002SMOTE). After experiments, the under-sampling method is adopted in this paper. By randomly removing some negative samples, the proportion of negative samples is reduced and the positive and negative sample ratio is finally close to 1:4.
Our experiment is completed on the PC with 1.99 GHz Intel i7-8550u CPU and 8GB memory. In the training stage of the experiment, the feature vectors of each pixel in the training set are input into the H-ELM network for training. The training process is iterated for 100 times, and the optimal model parameters are saved. In the testing stage, all the pixels of the test image are input into the trained H-ELM network, and the DenseCRF is used to optimize the output result.
5.1 Hyper-parameter selection
The H-ELM network has three hyper-parameters: the regular factor C, the number of hidden layers and the number of nodes in each hidden layer. The experiment shows that the regular factor C has a great influence on the result, so we determine the appropriate value by using the grid search method, with the search interval of , and finally determine that the appropriate value is . In addition, theoretically speaking, the more hidden layers H-ELM has, the stronger ability to express feature it will obtain. However, there is still no feasible method to determine the appropriate number of hidden layers and the number of hidden layer nodes. Therefore, according to our experiments and comparative analysis, this paper determines that the number of hidden layers is 3 and the number of nodes in each hidden layer is 200, 200, 1000, respectively.
5.2 Performance metrics
There are 4 kinds of classification results: TP (True Positive), TN (True Negative), FP (False Positive), FN (False Negative). TP refers to the number of pixels divided into contours correctly, TN refers to the number of pixels divided into non-contours correctly, FP refers to the number of pixels divided into contours wrongly, and FN refers to the number of pixels divided into non-contours wrongly.
In our experiment, we select F1-measure, Precision, Recall as the numeric performance metrics of contour detection. F-measure represents the weighted average of Precision and Recall. F1-measure is a common form of F-measure and becomes a standard evaluation technology in the field of contour detection and image segmentation (Martin2004Learning; Arbelaez2011). Precision is the proportion of correctly classified contour pixels as the actual contour pixels, indicating the classifier’s ability to correctly classify positive samples. Recall is the recall rate of positive samples. The calculation of each performance metric is shown in Table 1.
5.3 Experiment results
In the training stage, the training time is about 9.004s, and the training accuracy reached 95.53%. In the testing stage, the testing time of the single image is about 7.762s, with average F1-measure of 58%. The performance evaluation results of the test set are shown in Table 2 (due to limited space, only some image results in the test set are listed).
|ISS Image No.||F1-measure||Precision||Recall|
5.3.1 Comparison with traditional edge detection operators
Figure 5 shows the results of different edge detection operators on the observed object with different resolutions. As we can see, Canny, Roberts and Prewitt operator (corresponding to Figure 5(b)-(e) respectively) bring lots of false detection, and the edge connectivity of the observed object is unsatisfactory. However, our method (Figure 5(f)) can extract the contour of the observed object well, while keeping the better edge connectivity.
5.3.2 Comparison with Support Vector Machine (SVM)
Support Vector Machine (SVM) is a Machine learning algorithm proposed by Vapnik1998
on the basis of statistical learning theory, indicating significant advantages in many pattern recognition problems like small sample problem, and achieving good results in many fields such as handwritten recognition, biological information and so on. Therefore, this paper takes SVM algorithm as the representative of statistical learning algorithm and performs comparative experiments on our dataset.
Table 3 show the difference of performance between the SVM algorithm and our method. Obviously, the training time of our method is shorter than SVM and our method is superior to SVM in all performance metrics. As is shown in Figure 6, although SVM can extract fine contour in some way, it is not as good as our method in some inner details processing. It should note that the top (c) in Figure 6 shows our method don’t detect the terminator while SVM finds it. It is because we take the terminator pixels as non-contour ones when we label images. In fact, we use contour pixels to determine the center of disk-resolved object in our astrometry of ISS images, the terminator pixel is useless.
|Training time (s)||F1-measure||Precision||Recall|
5.3.3 Comparison with original ELM
In order to prove the superiority of unsupervised learning stage in H-ELM, we perform a comparative experiment between H-ELM and original ELM. The number of hidden layer nodes in original ELM is equal with the last layer (namely ELM classification layer) in H-ELM, both of which are 1000.
As can be seen from Table 3, original ELM algorithm has the shortest training time and is slightly better than SVM algorithm in all performance metrics, which shows the superiority of ELM algorithm in some way. Of course, it can also be seen that both ELM and SVM are not as effective as our method. Figure 7 shows the comparison results of original ELM and H-ELM on different observed objects. It can be found that, no matter in the simple or complex surface condition of the observed object, the method proposed in this paper is superior to original ELM in the precision of the extracted contour.
5.3.4 Comparison with Convolution Neural Network (CNN)
In order to compare our method with the currently popular deep learning method, we use the most common neural network in deep learning, namely Convolutional Neural Network (CNN) for comparative experiment. The adopted CNN architecture includes four 33 convolution layers, two 228 image blocks, as shown in Figure 8.
As is shown in Table 3, compared with other machine learning algorithms, the training of CNN requires a lot of time, which is also the drawback of all deep learning methods. Although CNN can extract a relatively complete contour (see Figure 9), it is far inferior to our method both in average performance metric and the precision of extracted contour. In other words, CNN can be used for rough contour detection, but it may not be the best choice for work requiring high precision of contour (such as calculating the center of celestial body according to its contour).
5.3.5 Comparison with H-ELM (without optimization)
Figure 10 shows the comparison between the H-ELM algorithm (without optimization) and our method. Obviously, after the optimization using DenseCRF, the inner contour (terminator) of the observed object can be effectively removed, so that only the outer arc-like contour can be retained.
A new method for contour detection of Cassini ISS images based on H-ELM and DenseCRF is proposed in this paper. On the one hand, our method inherits the advantages of H-ELM, obtaining feature learning and self-organization ability of deep neural network while keeping the fast training ability of ELM. On the other hand, we take the implicit relation between the classes of pixels in the contour image into consider, using DenseCRF algorithm to optimize the contour results.
Through experiments, we proved that the proposed method has the following advantages:
Extremely short training time
Strong generalization ability
The back-end optimization part can effectively remove part of the inner contour and retain the outermost contour of the celestial body.
In a word, the method proposed in this paper is available for the contour detection of disk-resolved object in Cassini ISS images.
However, it should be mentioned that, at present, there are many machine learning (ML) methods. To find a better ML method than the one in the paper is our further study in the future. Compared with the traditional methods, ML methods can eliminate false contour detection to a great extent, and give a more accurate contour. It is because ML methods can learn the pattern hidden in the image, thus making solution close to manual labeled result as much as possible. Obviously, the contour extracted using ML methods will have almost no noise, and be closer to the actual contour of the object. Therefore, we believe that ML will be a promising way to solve the problem of contour detection. | 0.817144 | 3.628616 |
Katie Bouman wows U-M community with insider’s look at the black hole imaging project
Speaking to a full house in Rackham, Dr. Katie Bouman – Michigan ECE alum – explained the history and science of the project that gave us the first ever photo of a black hole.
Nine months ago, the first ever image of a black hole was released to the public, captivating the world. U-M alum, Dr. Katie Bouman (BSE EE 2011), was a key player in the project, and she spoke about the experience during her return to campus last week in an event hosted by Michigan Astronomy.
Presenting to a packed house in the 4thfloor Rackham Amphitheatre, Bouman began by explaining the methods used to photograph subjects that are invisible to the human eye, such as how we image the inside of one’s body using special sensors or how we observe space phenomena that is extraordinarily far away. Black holes are particularly challenging.
“Black holes are one of the most mysterious objects in the universe,” Bouman said.
Despite its name, a black hole isn’t a hole at all – it’s a pocket of space full of a massive amount of densely packed matter. Black holes take up a relatively little amount of space considering their ridiculous amount of mass, so they ultimately warp the very fabric of space-time. They are the universe’s ultimate quicksand, from which not even light can escape.
Einstein first predicted the presence of black holes as part of his theory of relativity, but even he had doubts that the confounding phenomenon actually existed. Over the next century, more pieces of evidence assembled: massive energy signatures that couldn’t be explained by stars alone, the cosmic sound of two black holes colliding, and finally the detection of gravitational waves.
But we had never seen one. In fact, obtaining an actual image of a black hole was believed to be impossible. Black holes are so far away that the only telescope capable of photographing them would be one the size of the earth.
Since building such a device is obviously not an option, an international team of over 200 scientists came up with an alternative: a network of radio telescopes. This conglomerate, known as the Event Horizon Telescope (EHT), features eight radio observatories that include bases on six mountains and four continents.
“Joining telescopes in this manner is called very-long-baseline interferometry or VLBI,” Bouman said. “We essentially record the light traveling from the black hole at each telescope, and then we bring it all together and use our computers to act like the lens to make the final picture.”
The target was a black hole located in the center of Messier 87 (M87), an elliptical galaxy some 55 million light-years from Earth. The team collected 5 petabytes of data, which are so much data that it would literally break the internet if you tried to send the data via e-mail. If the data were standard-sized films, it would be the equivalent size of 50,000 movies.
Due to the extraordinary volume, the data were captured on hard drives that had to be physically moved via planes, trains, and automobiles, to a common location for analysis.
“There, we used a special purpose super-computer called a ‘correlator’ to merge the massive about of data together,” Bouman explained. “The team of scientists then reduced the data down even further using newly developed algorithms, so by the time we started to make images, it was a file you could just email.”
The next step is to reconstruct the actual image, but this is easier said that done. Light from the black hole has to travel 55 million light years, and it will reach each telescope at a slightly different point in time. Atmosphere will also affect how the signal is distorted, and it will vary based on the location of each telescope. In addition, few measurements mean there is an infinite number of possible images that would fit the data.
Each phase of the process involved multiple steps and constant replication to ensure a verified result. Bouman helped with many parts of the project, including collecting data from the black hole at one of the telescopes in Mexico, but her main focus was in creating algorithms that would compensate for signal noise and distortion. The next step was the actual image reconstruction.
“The biggest challenge we faced with M87 was not just how to recover an image, but how do we make sure what we’re recovering is real?” Bouman said.
The biggest challenge we faced with M87 was not just how to recover an image, but how do we make sure what we're recovering is real?Dr. Katie Bouman
Bouman led the team that developed the tests and techniques used to verify the black hole image. One of the ways they tested their reconstruction methods was by giving teams distorting synthetic data from known images and then comparing the reconstructed image to the original image. While some images were abstract and resembled space phenomena, the team also included unexpected images, such as Frosty the Snowman, to ensure against potential human bias.
When it came time to reconstruct the actual black hole image, the team wanted to safeguard against any potential for bias, so they split into four teams. Each team used a specific method of image reconstruction (there are different approaches) and worked entirely in isolation. No team was given any information about the results of the other teams. This process took seven weeks.
“After seven weeks, we all gathered together in Cambridge, Massachusetts, and revealed our images to each other,” Bouman said.
Although each image looked slightly different, they all contained the same key features: a ring of the same size that was brighter on the bottom than the top.
“It was one of the happiest moments,” Bouman said. “Seeing the same basic structure result from each team and method made me really confident in the results that we were getting.”
The team further tested their methods by trying to break the image. They attempted to force a different picture – a solid disc of light instead of a ring, for example – but in every instance, the data would not allow there to be any structure but a ring.
The team also employed additional validation methods, and while there is some question about the wispy light appearing outside the ring, the ring itself was thoroughly verified.
The importance of the black hole image goes beyond just a cool image reconstruction project. The image itself sheds light on many mysteries about black holes and how they function. It is astonishingly similar to simulations that scientists have made for years predicting what emissions around a black hole would look like.
“By studying this image, we have the best evidence yet black holes exist, as well as a way to study and learn about the immediate environment around them,” Bouman said.
By studying this image, we have the best evidence yet black holes exist, as well as a way to study and learn about the immediate environment around them.Dr. Katie Bouman
The EHT team is looking to improve their methods to capture better images and new targets. They are developing new machine learning approaches to solve for the optimal placement of new telescopes to expand the network and see even more.
“The one I’m most excited about is we could capture a video of the gas falling in towards the black hole Sagittarius A*, the black hole in the center of our own Milky way Galaxy,” Bouman said.
Students got a chance to mingle with Bouman during a reception held before the talk and ask her questions during a Q&A after the talk.
“She was amazing!” said Isha Bhatt, an undergrad studying electrical engineering. “We found her to be extremely kind, intelligent, and candid.”
Bouman reminisced about her time on campus, including her favorite class (EECS 216) and her involvement with the Michigan Research Community.
“It’s really fun being back here and have all these memories of my time here come back to me,” Bouman said.
Bouman is currently an Assistant Professor of Computing and Mathematical Sciences and Electrical Engineering at the California Institute of Technology. | 0.878827 | 3.706705 |
Orbit Shapes Interactive Animation
This interactive animation illustrates two of the most important parameters associated with orbits - shape and size. Orbits are ellipses. Mathematicians and astronomers use the term "eccentricity" to describe how elongated (oval-shaped, as opposed to circular) an ellipse is. A high eccentricity means an ellipse is long and skinny; a low value means the ellipse is nearly circular. For an ellipse, eccentricity can range from zero to one.
Astronomers use the term "semi-major axis" length to describe the size of an ellipse. The major axis of an ellipse runs lengthwise along the long axis of the ellipse. The semi-major axis length is the distance from the center of the ellipse to one end along this major axis. The semi-major axis of an ellipse is analogous to the radius of a circle.
Use the sliders in the interactive animation (below) to alter the shape and size of the orbit of "your planet". Earth's orbit is shown for comparison.
(Note: If you cannot see the animation below, or it is not working properly, you may need to download the latest Flash player.)
Here are a few activities you may want to try, using the orbit shapes interactive, to learn more about orbits:
- A "Hohman transfer ellipse" is a trajectory commonly used to send a spacecraft between two planets that have circular orbits. The orbits of Earth and Jupiter are very nearly circular. Pretend "your planet" in the interactive is a spacecraft being sent from Earth to Jupiter. Adjust its eccentricity and semi-major axis until its perihelion point is just touching Earth's orbit and its aphelion point is just reaching out to Jupiter's orbit. About how long does it take a spacecraft on this trajectory to travel to Jupiter? Note the position of Earth when the "spacecraft" reaches perihelion; then count how many times Earth circles the Sun while the "spacecraft" travels to Jupiter. Remember, each time the Earth goes around is one year!
- As you probably know, Pluto orbits further from the Sun than any of the other eight planets. You may not know that Pluto's orbit is also more eccentric than the orbits of the other eight planets. The orbit of Pluto has an eccentricity around 0.25 and a semi-major axis length of about 39.5 AU. Set the values for "your planet" in the interactive animation to those of Pluto. How does the orbit of Pluto compare to the orbit of Neptune, the 8th planet in order from the Sun? Is Pluto always the most distant planet from the Sun? If not, how much of the time is it closer to the Sun than another planet? How does the relatively high eccentricity of Pluto's orbit influence this situation? If Pluto's orbit was less eccentric, would it ever be the 8th planet?
- Most comets have very eccentric orbits. The most famous comet, Halley's Comet, has an orbital eccentricity of 0.967 and a semi-major axis length of almost 18 AU. This interactive animation only allows eccentricity settings up to 0.9; check out the comet orbit interactive to see what Halley's orbit looks like. Some comets, called short period comets because they orbit the Sun in less than 200 years, come from a region beyond Neptune's orbit called the Kuiper Belt. A typical short period comet might have an eccentricity around 0.9 and a semi-major axis length of about 25 AU. Try out those values in the interactive animation on this page. Where does a short-period comet spend most of its time? A comet only forms its tails and becomes visible to us when it is close to the Sun, well inside the orbit of Jupiter. Notice how a comet is only visible for a few months out of an orbit lasting decades to centuries (Halley's Comet takes 76 years to orbit the Sun). Some comets have much shorter orbital periods of just a few years. Many of these are "Jupiter-family comets" that were tossed into the inner Solar System by the gravity of that giant planet during a close encounter with Jupiter. Comet Wild 2, the target of the Stardust space mission, is one such Jupiter-family comet. Wild 2 has an eccentricity of 0.54, a semi-major axis length of 3.44 AU, and an orbital period of 6.39 years. Set up Wild 2's orbit in the interactive animation to see a typical Jupiter-family comet. Finally, some comets come from the far distant reaches of the Oort Cloud, the outermost fringe of our Solar System. One such "long-period comet", Comet Hale-Bopp, has an eccentricity of 0.995 and a semi-major axis length of about 186 AU! Hale-Bopp put on a spectacular show in 1997, but won't be back this way again for more than 2,500 years! | 0.839598 | 3.656948 |
This paper provides a primarily descriptive approach to understanding the Sun-Earth system, and its place in the wider Universe. Lecture topics include ancient, classical, and modern astronomy, stellar evolution, supernovae, black holes, cosmology, and the exploration of the solar system. Special topics included are: "The size and age of the universe", "The search for extra-terrestrial intelligence", and "What would be the effect of a large meteor impact on the Earth?" The importance of historical aspects and the progressive development of ideas will be emphasized, with a minimum of mathematics. This course is intended for students who have an interest in a broad education. We aim to facilitate a continuing interest in Astronomy and space exploration.
The course consists of 24 lectures, 6 one-hour tutorial sessions and 6 three-hour laboratory classes. There is a mid-school test and two essays.
Professor Craig Rodger
|The size of the Universe, notation|
|A sense of time|
|Ancient astronomy and astrology|
|Parallax, astronomical systems and distance measurements|
|Galileo, Newton and the telescope|
|Spectroscopy and the classification of stars|
|Hertzsprung–Russell diagram and spectroscopic parallax|
|Fission, fusion and proto stars|
|Main sequence stars; death of stars|
|Exotic stars (Neutron stars, Black holes, etc)|
|Our solar system; our Sun|
|The biggest rulers & galaxy formation|
|Hubble's law, the big bang and cosmology|
|Life in the Universe & SETI|
|Textbook:Seeds and Backman (Foundations of Astronomy, Thomson Brooks/Cole, 14th edition, 2019) |
This non-advancing paper progresses in a largely descriptive way through the essentials of our understandings of the Sun-Earth system, and its place in the wider Universe. Lecture topics include ancient and classical astronomy, stellar evolution, black holes, cosmology, and the exploration of the solar system. The importance of historical aspects and the progressive development of ideas is emphasised, with a minimum of mathematics.
Special topics included are: "the size and age of the universe", "the search for extra-terrestrial intelligence" and "what would be the effect of a large meteor impact on the Earth?" This paper is intended for students who have an interest in a broad education. We aim to facilitate a continuing interest in astronomy and space exploration.
|Paper title||Sun, Earth and Universe|
|Teaching period||Summer School|
|Domestic Tuition Fees (NZD)||$1,080.30|
|International Tuition Fees (NZD)||$4,858.95|
- Schedule C
- Teaching staff
- Professor Craig Rodger
- Text books are not required for this paper.
- Graduate Attributes Emphasised
- Global perspective, Interdisciplinary perspective, Lifelong learning, Scholarship, Critical thinking, Information literacy, Self-motivation. View more information about Otago's graduate attributes.
- Learning Outcomes
Students completing this paper will:
- Be aware of the essential aspects of our understanding of the wider Universe.
- Know the importance of historical aspects and the progressive development of ideas.
- Grasp the range of scale sizes and numerical values needed to describe astronomical scales of time, space and mass. | 0.8814 | 3.267018 |
Water has been identified in the most uncanny of places – as vapors in the nebulae that roam our Milky Way Galaxy, as ices in the protoplanetary disks that surround many protostars, and as liquids below the icy crusts of the Jovian moons Europa, Ganymede, and Callisto. In 2005, the Cassini spacecraft imaged geysers of liquid water erupting from the surface of Saturn’s moon Enceladus. The liquid form of water is especially important to biotic processes, as it provides an essential solvent for making the sundry hookups and energy transfers that are necessary to life.
Despite compelling evidence for water throughout our Milky Way Galaxy and within our local Solar System, the specific origin of water on Earth remains controversial. We know that the Earth formed some 4.6 billion years ago, as the primordial Solar System gravitationally congealed from the pre-planetary disk of debris that surrounded the proto-Sun. Once the Sun “turned on” its thermonuclear fires, things began to change in a big way.
The primitive Solar System was a busy chaotic place. Did Earth’s cargo of precious water come home-grown 4.6 billion years ago or was it delivered via comets during the Late Heavy Bombardment that ended 3.9 billion years ago? (Caltech-JPL/NASA)
Some scientists contend that the inner Solar System was too hot for any water to remain in the rocky bits that ultimately came together to form the Earth. They look to wayward comets and asteroids that formed farther from the scalding Sun as the key provisioners of Earth’s oceans. However, others find important discrepancies in the relative amounts of regular water and “heavy” (deuterated) water in their comparisons of the Earth, comets, and meteorites. The few comets that have been chemically probed appear to have far more deuterated water than Earth’s oceans – indicating (to these scientists at least) that comets could not have delivered the bulk of Earth’s water.
Meteorites are interplanetary rocks of various kinds that have fallen to Earth. They are thought to represent pieces of much larger asteroids that formed between the orbits of Mars and Jupiter. Some meteorites are found to be rich in water. Others are bone dry. Again, chemical and isotopic analyses seem to rule out asteroidal meteorites delivering most of Earth’s water, as they find that the early Earth was likely the beneficiary of mostly dry meteorites. The only way to wiggle around this situation is to have a single unusually wet and very large (Moon-size) body to hit Earth shortly after its birth. Something like the Jovian moon Europa could have done the trick.
Perhaps surprisingly, several scientists have gone back to square one – working out scenarios which retain the water in the inner Solar System despite the intense solar heating and intense bombardment by other rocky bodies. Here, the water was in the form of a warm vapor that stuck to tiny grains of rock which then aggregated to build up pebbles – and ultimately – a wet Earth. Once the Earth’s crust began to solidify, it would have belched out huge quantities of water during a period of rampant volcanic eruptions. As the saturated atmosphere cooled, it began to rain – and rain – and rain, filling the Earth’s basins with the water that we inherit to this day.
Recent support for this revived scenario of home-grown water has come from analyses of ancient zircons on Earth and, perhaps surprisingly, in lunar soil and rocks that were gathered by astronauts during the Apollo 15 and 17 missions to the Moon. The zircons found in Australia represent the oldest unaltered mineral crystallizations to be found on Earth. Radioactive dating of the uranium that forms part of the zircon crystals indicate ages of 4.4 billion years for the oldest zircons – corresponding to the time when the cooling Earth had just solidified from a molten state. The balance of oxygen isotopes within these minerals suggests a watery origin. Some scientists have used the zircon data to imagine a primordial Earth that was neither scalding nor blanketed by an arid stifling atmosphere of carbon dioxide. Instead, they suggest a rather clement world, whose tectonic activity (also indicated by the zircon properties) would have sequestered the carbon dioxide into carbonate rocks – leaving behind a moist temperate atmosphere and perhaps oceans that would have been hospitable to life.
On the Moon, the Apollo astronauts collected hundreds of pounds of lunar soil (regolith) and rocks. Subsequent analyses of the fine-grained regolith have revealed microscopic glass spherules that have incorporated small but significant amounts of water. These spherules are thought to have been created during a primordial period of intense lunar volcanism. The so-called “fire fountaining” produced mists of molten lava which then cooled into solid spheroidal droplets. Falling back down to the Moon’s surface, the tiny glass beads were collected intact by the Apollo astronauts approximately 3.7 billion years after their formation. Similar amounts of water (of order 1 part per 10,000) have been found inside lunar rocks that contain magnesium-rich olivine. These rocks are also thought to have originated deep inside the Moon in the form of magma which then rose toward the surface and crystallized.
Tiny green glass beads have been found in samples of lunar regolith that were collected during the Apollo 15 and 17 missions to the Moon. These spherules contain water as part of their mineral composition. The water appears to be identical in its isotopic properties to the water found on Earth, thus suggesting identical origins. (NASA)
Analyses of the lunar glass beads and magnesium-rich rocks have yielded ratios of deuterated vs. regular water that resemble those found on Earth and in carbonaceous chondrites (a type of meteorite that contains primitive chondrules – the first major crystallizations in the inner Solar System). These sorts of isotopic measurements are tricky, as the so-called D/H ratio can change as the sample undergoes weathering from cosmic rays, solar wind implantation, and degassing of the magma. Only after compensating for such effects did the investigators find the strong resemblance among the waters of the Earth, Moon, and carbonaceous chondrites – and a significant disparity with respect to the D/H ratios that have been measured in a handful of comets.
If these results hold up, Earth’s water was likely archived in place, when the inner planets and carbonaceous asteroids condensed from the proto-planetary disk some 4.6 billion years ago. That the Earth and Moon share similar waters indicate that the archiving took place before Earth experienced the big impact that led to the formation of the Moon 4.5 billion years ago. The early caching of water within the Earth, Moon, and carbonaceous chondrites would also suggest that water is ubiquitous throughout the inner Solar System. Moreover, water is likely to be present in the inner rocky parts of other planetary systems. And where there is water co-mingling with rocky surfaces, there is a much greater chance for life to emerge.
Further research on Earth’s watery past will likely benefit from future robotic probes and landers, whereby the isotopic composition of water across the Solar System can be assayed. That will help to pin down the status of oceanic water on Earth relative to the larger context of planetary, asteroidal, and cometary sources. Meanwhile, sub-millimeter spectroscopic observations of icy objects in the Kuiper Belt may help to determine the isotopic composition of these pristine Solar System objects beyond the orbit of Neptune. Closer to home, deep-sea probes will help to determine the isotopic composition of water emerging from the Earth’s upper mantle. So, the next time you drink a glass of water, think about those trillion-trillions of H2O molecules and their long strange journey to your lips. You may be tasting the first rains that ever fell on Earth.
William H. Waller earned his Ph.D. in astronomy at the University of Massachusetts. He has since carried out diverse programs in scientific research and education at the University of Washington, NASA’s Goddard Space Flight Center, Tufts University, and the Museum of Science – Boston. He is author of The Milky Way — An Insider’s Guide (see http://press.princeton.edu/titles/9938.html) and co-editor of The Galactic Inquirer – an e-journal and forum on the topics of galactic and extragalactic astronomy, cosmochemistry, astrobiology, and the prospects for interstellar communication (see
http://galacticinquirer.net). Bill currently teaches physical sciences at his hometown high school in Rockport, MA, and serves as a Zooniverse Teacher Ambassador (seehttp://www.zooniverse.org). He can be reached at [email protected]. | 0.891295 | 3.946747 |
A team of astronomers combined data gathered by observatories all around the world to make an extraordinary discovery of multiple ancient massive galaxies. Researchers at the Insitute of Astronomy at the University of Tokyo have been suspecting the presence of unidentified objects for a long time.
In the past, The Hubble Space Telescope was used to identify these unknown structures, but with no success. However, using more technologically advanced observatories, they were finally able to find answers to their questions.
Tao Wang, one of the researchers, said: “This is the first time that such a large population of massive galaxies was confirmed during the first 2 billion years of the 13.7-billion-year life of the universe. These were previously invisible to us. This finding contradicts current models for that period of cosmic evolution, and will help to add some details, which have been missing until now.”
Ancient Massive Galaxies Discovery Could Shed More Light On Dark Matter
It sure is surprising that a galaxy of this size was so hard to see at first. Professor Kotaro Kohno explains that the recently-discovered galaxies emit such a faint light that not even the Hubble Telescope is capable of detecting the wavelengths. To identify those galaxies, scientists turned to the Atacama Large Millimeter/submillimeter Array (ALMA).
Since these galaxies are so far away, their light is also stretched. As we know, the universe is continuously expanding, elongating visible light, which eventually turns into infrared light.
At first, some researchers found it hard to believe that these galaxies were as old as it seemed. The first suspicion suggesting their existence came from the Spitzer Space Telescope. Later on, ALMA was used to reveal details about them. The Very Large Telescope in Chile was the one to gather the data that suggests the galaxies’ ancient age. The discovery of these massive ancient galaxies means that scientists will have the opportunity to study the evolution of the supermassive black holes located inside them. Even more, massive galaxies offer the chance to explore the invisible dark matter. | 0.855743 | 3.775295 |
NASA’s ICON is on a mission to investigate the ionosphere
Artist's illustration of ICON. Image: NASA Goddard's Conceptual Image Lab/B. Monroe
A NASA satellite designed to investigate a critical layer of Earth's atmosphere launched to space last Thursday.
Why it matters: Scientists think the ionosphere can interfere with communications, expose astronauts to high radiation and even drag satellites down through the atmosphere earlier than expected when space weather hits.
The spacecraft — called the Ionospheric Connection Explorer (ICON) — is tasked with gathering data about the ionosphere to understand how the region affects satellites and people in space.
- “ICON will be the first mission to simultaneously track what’s happening in Earth’s upper atmosphere and in space to see how the two interact, causing the kind of changes that can disrupt our communications systems," Nicola Fox, NASA's director for heliophysics, said in a statement.
Details: 3 of ICON's 4 instruments are designed to study airglow — bands of faint light created when neutral particles in the atmosphere are slammed by radiation from the sun, exciting the particles and causing them to emit light.
- Airglow is similar to the northern or southern lights, but instead of being relegated just to high latitudes, airglow instead appears all over the world.
- ICON data should help piece together how airglow works.
- The spacecraft's 4th instrument will measure the environment around ICON.
The bottom line: Space weather poses a major threat to people living in space and satellites in orbit, so the data ICON gathers about the way the ionosphere behaves is critical to help protect those assets and people in orbit.
Go deeper: The coming cost of moving satellites | 0.809169 | 3.146099 |
By Eric J. Chaisson
Adapted from Cosmic Evolution: The Rise of Complexity in Nature, published by Harvard University Press, 2001
It is perhaps a sobering thought that we seem so inconsequential in the Universe. It is even more humbling at first--but then wonderfully enlightening--to recognize that evolutionary changes, operating over almost incomprehensible space and nearly inconceivable time, have given birth to everything seen around us. Scientists are now beginning to decipher how all known objects--from atoms to galaxies, from cells to brains, from people to society--are interrelated. We are attempting to sketch the unifying scenario of cosmic evolution, a powerful new epic for the new millennium.
Simply defined, cosmic evolution is the study of change--the vast number of developmental and generative changes that have accumulated during all time and across all space, from big bang to humankind. To quote some long-forgotten wit, "Hydrogen is a light, odorless gas which, given enough time, changes into people." More seriously, cosmic evolution comprises the sum total of all the many varied changes in the assembly and composition of radiation, matter, and life throughout the history of the Universe. These are the changes that have produced our Galaxy, our Sun, our Earth, and ourselves.
As such, the most familiar kind of evolution--biological evolution, or neo-Darwinism--is just one subset of a much broader evolutionary scheme encompassing much more than mere life on Earth. In short, what Darwinism does for plants and animals, cosmic evolution aspires to do for all things.
Of central importance, we can now trace a chain of knowledge--a loose continuity along an impressive hierarchy—sequentially linking:
- the evolution of primal energy into elementary particles and atoms
- the evolution of those atoms into galaxies and stars
- the evolution of stars into heavy elements
- the evolution of those elements into the molecular building blocks of life
- the evolution of those molecules into life itself
- the evolution of advanced life forms into intelligence
- the evolution of intelligent life into a cultured and technological civilization.
Metaphorically (at least), cosmic evolution aims to frame a heritage--a cosmic heritage--a grand structure of understanding rooted in events of the past, a sweeping intellectual map embraced by humans of the present, a virtual blueprint for survival along the arrow of time. The objective, boldly stated, is nothing less than an interdisciplinary cosmology in which life has not merely a place in the Universe, but also perhaps a role to play as well.
Who are we? Where did we come from? How did everything around us, on Earth and in the heavens, originate? What is the source of order, form, and structure characterizing all material things? Even more fundamentally, why is there something rather than nothing?
With cosmic evolution as an intellectual framework, we can begin to understand the environmental conditions needed for matter to have become increasingly ordered, organized, and intricately structured, and not merely among biological systems. This trend toward increased complexity throughout Nature writ large violates no laws of physics, and certainly not those of thermodynamics. Indeed, it is modern thermodynamics that perhaps best helps to explain the rise in order, form, and complexity among all animate and inanimate objects.
Nor is the idea of ubiquitous change novel to our rapidly increasing knowledge of the world, the Universe, and ourselves. What is new and exciting is the way that frontier, non-equilibrium science now helps us mold an integrated cosmology, from quark to quasar, from microbe to mind--indeed one wherein life does play an integral role.
Cosmic evolution is the study of many varied changes on a universal scale, a subject that seeks to synthesize the reductionistic posture of specialized science with a holistic view of systems science. It is a story about the awe and majesty of twirling galaxies and shining stars, of redwood trees and buzzing bees, of a Universe that has come to know itself. But it is also a story about our human selves--our origin, our existence, and perhaps our destiny.
Eric J. Chaisson is Research Professor of Physics at Tufts University, where he also directs the Wright Center for Science Education. He has twice won the Science Writing Award from the American Institute of Physics--for Cosmic Dawn (1981) and for The Hubble Wars (1995). This article is adapted from a new book, Cosmic Evolution: The Rise of Complexity in Nature, published by Harvard University Press, 2001. | 0.823975 | 3.712512 |
There are a number of health risks that come with going to space. Aside from the increased exposure to solar radiation and cosmic rays, there are the notable effects that microgravity can have on human physiology. As Scott Kelly can attest, these go beyond muscle and bone degeneration and include diminished organ function, eyesight, and even changes at the genetic level.
Interestingly enough, there are also a number of potential medical benefits to microgravity. Since 2014, Dr. Joshua Choi, a senior lecturer in biomedical engineering at the University of Technology Sydney, has been investigating how microgravity affects medicine and cells in the human body. Early next year, he and his research team will be traveling to the ISS to test a new method for treating cancer that relies on microgravity.
According to Chou, the inspiration for his research came from a conversation he had with the late and great Stephen Hawking. During the conversation, Dr. Hawking remarked how nothing in the Universe defies gravity. Later, when a friend of Chou’s had been diagnosed with cancer, he recalled what Dr. Hawking had said and began to wonder, “What would happen to cancer cells if we take them out of gravity?”
Simply put, cancer is a disease where cells begin dividing uncontrollably and spread to certain parts of the body and take them over. Cancer cells do this by coming together to form a solid tumor in the body, which then grows until the cells are signaled to invade healthy tissues – such as the heart, lungs, brain, liver, pancreas, etc.
One of the biggest stumbling blocks with cancer research is that no one knows exactly when that point is reached. However, the process through which cancer grows and spreads would seem to indicate that there is a means through which the cells are able to sense each other and gravitate together to form a tumor.
However, biomedical researchers do understand that the only way cancer cells could sense each other is through mechanical forces, and that those forces evolved to work in an environment where there’s gravity. This motivated Chou to think of ways in which the lack of gravity might impede cancer cells’ ability to divide and spread.
Chou has some experience in conducting space-based medical research. While working at Harvard, he took part in a project that resulted in the creation of a drug to treat osteoporosis. Part of their research took place aboard the International Space Station (ISS). As Chou explained:
“This first experience of seeing how the space environment impacts our understanding of cell biology and disease progression inspired me to ask: ‘Why can’t we apply the same strategy to studying other cells and diseases?’”
Already, Chou and his team have tested the effects of microgravity on cancer cells in their laboratory. To do this, one of his graduate students created a device that is essentially a tissue box-sized container with a small centrifuge inside. The cells of different diseases are contained in a series of pods within the centrifuge, which then spins them up until they experience the sensation of microgravity.
As Chou indicated, the results were rather encouraging. “Our work has found that when placed in a microgravity environment, 80 to 90 percent of the cells in the four different cancer types we tested – ovarian, breast, nose and lung – were disabled,” he said. “By disabled, I mean they either die or float off because they can no longer hold on. Those four cancer types are some of the hardest cancers to kill.”
Even more impressive is the fact that these results were obtained by simply altering the gravitational forces – i.e. without the help of drugs. When subjected to microgravity-conditions, the cancer cells were unable to sense each other and therefore had a very hard time coming together.
“Driving this mission has been a whole team effort – I feel very fortunate to be supported by my faculty and a group of very talented female engineering students who inspire me to keep going. They do so much of the hard work in making this project a reality.”
The next step, which will be happening early next year, will involve the team sending their experiment to the ISS aboard a specially-designed space module (SpaceX will be providing launch services). Chou and his colleagues will spend the duration of the experiment (seven days) on the ground, where they will monitor the experiment’s progress and conduct live-cell imaging via data feeds.
Once the experiment is complete, the cells will be frozen for their return trip to Earth, whereupon Chou and his colleagues will examine them for genetic changes. If the results aboard the ISS confirm what Chou and his team found in the lab, he hopes that they will be able to develop new treatments that can have the same effect as microgravity and neutralize cancer cells’ ability to sense each other.
Ideally, these treatments would not constitute a cure but could supplement existing anti-cancer medical regimens. Combined with drugs and chemotherapy, treatments arising from this research would effectively slow the spread of cancer in the human body, thereby making conventional treatments more effective and shorter-lived (and less costly too).
“I also hope this is one of many Australian space research missions. My team and I are so fortunate to get the opportunity to do this research as it’s so rare and we’ll use our mission findings to signal to the Australian research community that the era of space biology and medicine is well and truly here.”
This research will also come in handy in space, where astronauts are forced to spend months in microgravity and are exposed to considerably more radiation (and therefore at an increased risk of developing cancer). These and other strides that are being made in the field of space medicine further demonstrate how space-based research can lead to commercial and medical benefits for people here on Earth.
Further Reading: UTS
Source: Universe Today, by Matt Williams.
Comment this news or article | 0.813524 | 3.116472 |
About 2,000 light-years away, in the constellation of Cygnus (the Swan), lies Sharpless 2-106 (after Stewart Sharpless who put the catalog together in 1959), the birth-place of a star cluster-to-be.
Two recent image releases – by Subaru and Gemini – showcase their new filter sets and image capabilities; they also reveal the stunning beauty of the million-year-long process of the birth of a star.
The filter set is part of the Gemini Multi-Object Spectrograph (GMOS) toolkit, and includes ones centered on the nebular lines of doubly ionized oxygen ([OIII] 499 nm), singly ionized sulfur ([SII] 672 nm), singly ionized helium (HeII 468nm), and hydrogen alpha (Hα 656 nm). The filters are all narrowband, and are also used to study planetary nebulae and excited gas in other galaxies.
The hourglass-shaped (bipolar) nebula in the new Gemini image is a stellar nursery made up of glowing gas, plasma, and light-scattering dust. The material shrouds a natal high-mass star thought to be mostly responsible for the hourglass shape of the nebula due to high-speed winds (more than 200 kilometers/second) which eject material from the forming star deep within. Research also indicates that many sub-stellar objects are forming within the cloud and may someday result in a cluster of 50 to 150 stars in this region.
The nebula’s physical dimensions are about 2 light-years long by 1/2 light-year across. It is thought that its central star could be up to 15 times the mass of our Sun. The star’s formation likely began no more than 100,000 years ago and eventually its light will break free of the enveloping cloud as it begins the relatively short life of a massive star.
For this Gemini image four colors were combined as follows: Violet – HeII filter; Blue – [SII] filter; Green – [OIII] filter; and Red – Hα filter.
The Subaru Telescope image was made by combining images taken through three broadband near-infrared filters, J (1.25 micron), H (1.65 micron), and K’ (2.15 micron). | 0.835941 | 3.794731 |
Using NASA’s Spitzer Space Telescope, astronomers observed gas emissions from Comet ISON, estimating that ISON is emitting about 1 million kilograms of what is most likely carbon dioxide gas and about 54.4 million kilograms of dust every day.
Pasadena, California — Astronomers using NASA’s Spitzer Space Telescope have observed what most likely are strong carbon dioxide emissions from Comet ISON ahead of its anticipated pass through the inner solar system later this year.
Images captured June 13 with Spitzer’s Infrared Array Camera indicate carbon dioxide is slowly and steadily “fizzing” away from the so-called “soda-pop comet,” along with dust, in a tail about 186,400 miles (300,000 kilometers) long.
“We estimate ISON is emitting about 2.2 million pounds (1 million kilograms) of what is most likely carbon dioxide gas and about 120 million pounds (54.4 million kilograms) of dust every day,” said Carey Lisse, leader of NASA’s Comet ISON Observation Campaign and a senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. “Previous observations made by NASA’s Hubble Space Telescope and the Swift Gamma-Ray Burst Mission and Deep Impact spacecraft gave us only upper limits for any gas emission from ISON. Thanks to Spitzer, we now know for sure the comet’s distant activity has been powered by gas.”
Comet ISON was about 312 million miles (502 million kilometers) from the sun, 3.35 times farther than Earth, when the observations were made.
“These fabulous observations of ISON are unique and set the stage for more observations and discoveries to follow as part of a comprehensive NASA campaign to observe the comet,” said James L. Green, NASA’s director of planetary science in Washington. “ISON is very exciting. We believe that data collected from this comet can help explain how and when the solar system first formed.”
Comet ISON (officially known as C/2012 S1) is less than 3 miles (4.8 kilometers) in diameter, about the size of a small mountain, and weighs between 7 billion and 7 trillion pounds (3.2 billion and 3.2 trillion kilograms). Because the comet is still very far away, its true size and density have not been determined accurately. Like all comets, ISON is a dirty snowball made up of dust and frozen gases such as water, ammonia, methane and carbon dioxide. These are some of the fundamental building blocks, which scientists believe led to the formation of the planets 4.5 billion years ago.
Comet ISON is believed to be inbound on its first passage from the distant Oort Cloud, a roughly spherical collection of comets and comet-like structures that exists in a space between one-tenth light-year and 1 light-year from the sun. The comet will pass within 724,000 miles (1.16 million kilometers) of the sun on Nov. 28.
It is warming up gradually as it gets closer to the sun. In the process, different gases are heating up to the point of evaporation, revealing themselves to instruments in space and on the ground. Carbon dioxide is thought to be the gas that powers emission for most comets between the orbits of Saturn and the asteroids.
The comet was discovered Sept. 21, roughly between Jupiter and Saturn, by Vitali Nevski and Artyom Novichonok at the International Scientific Optical Network (ISON) near Kislovodsk, Russia. This counts as an early detection of a comet, and the strong carbon dioxide emissions may have made the detection possible.
“This observation gives us a good picture of part of the composition of ISON, and, by extension, of the proto-planetary disk from which the planets were formed,” said Lisse. “Much of the carbon in the comet appears to be locked up in carbon dioxide ice. We will know even more in late July and August, when the comet begins to warm up near the water-ice line outside of the orbit of Mars, and we can detect the most abundant frozen gas, which is water, as it boils away from the comet.”
NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.
For more information about Spitzer, visit: http://www.nasa.gov/spitzer . Learn more about NASA’s Comet ISON Observing Campaign: http://www.isoncampaign.org . NASA’s Comet ISON Toolkit is at: http://solarsystem.nasa.gov/ison. | 0.851706 | 3.818392 |
There is a growing evidence that our Sun was born in a rich cluster that also contained massive stars. Therefore, the study of high-mass star-forming regions is key to understand our chemical heritage. In fact, molecules found in comets, in other pristine Solar System bodies and in protoplanetary disks, are enriched in 15N, because they show a lower 14N/15N ratio (100-150) with respect to the value representative of the Proto-Solar Nebula (PSN, 441 ± 6), but the reasons of this enrichment cannot be explained by current chemical models. Moreover, the 14N/15N ratio is important because from it we can learn more about the stellar nucleosynthesis processes that produces both the elements. In this sense observations of star-forming regions are useful to constrain Galactic chemical evolution (GCE) models. | 0.85102 | 3.381107 |
Of Saturn’s 53 known moons, Titan is the largest and is also the second largest moon in our solar system. It’s also the only moon that has a cloud system and a dense atmosphere that is similar to what a planet would have.
That’s saying a lot since we have identified around 150 known moons. Titan is bigger than the planet Mercury. In fact, if it was orbiting the sun it would be considered to be a planet.
Scientists refer to Titan as the “most Earth-like world that we have found to date.” Titan has a surface covered in liquid hydrocarbons such as ethane and methane that form lakes, rivers, and seas.
The biggest seas are as wide as hundreds of miles and hundreds of feet deep. Titan has thick crust of water ice and scientists think that there is even liquid water underneath it.
The atmosphere is made up of mostly nitrogen, but the pressure on Titan is 50% higher than that on Earth.
Given all of these conditions, Titan is a moon that scientists are looking at for potential life.
Of course, if there is life on Titan, it would be different than what we have on Earth because it would use a different type of chemistry. Until it’s verified, astronomers are unsure if Titan is lifeless or has an unknown type of lifeform.
Discovered By: Christiaan Huygens
Discovery Date: March 25, 1655
Diameter: 5,149.4 km
Mass: 1.35 × 10^23 kg (1.8 Moons)
Orbital Period: 15.9 days
Orbit Distance: 1,221,865 km
Surface Temperature: – 40 degrees C
Titan can’t be seen with the naked eye. In 1655, Titan was discovered by the Dutch astronomer, Christiaan Huygens, who used a telescope that was advanced for its time.
In 1944, 300 years later, Gerard Kuiper, a Dutch-American astronomer made the discovery of some of Titan’s special characteristics. Kuiper passed sunlight that was reflected from Titan through a spectrometer and detected methane gas.
As he studied Titan, he recognized that the moon had a hazy dense atmosphere.In 1979, the Pioneer 11 spacecraft was sent to explore Titan. Pioneer 11 confirmed the research that scientists had previously done on the temperature and mass of Titan.
They had also correctly predicted that the spacecraft would be able to see hints of a bluish color in the upper atmosphere of Titan.Titan, like many objects in our solar system, took its name from Greek mythology.
The Titans were the oldest gods that ruled over the universe before the Olympians.
Formation, Structure and Surface:
The atmosphere on Titan is believed to hold a clue as to how Titan was formed. When the NASA and European Space Agency Cassini-Huygens mission was sent to Titan it measured the atmosphere and found nitrogen-14 and nitrogen-15 isotopes.
The isotope ratio is very close to comets in the Oort Cloud, a place in the outer solar system where hundreds of billions of icy bodies orbit.
This information leads scientists to believe that Titan was formed around the same early creation time as our sun and that it formed in the cold dust and gas disk like our sun, instead of the warmer material that formed Saturn.
Scientists are unsure what the interior of Titan looks like, but computer models that have been based on Cassini-Huygens data indicate that it may have 5 major layers.
The core, or innermost layer is made up of water-bearing silicate rock that has a diameter from 2,500-4,000 km. A shell of a special type of water ice called ice-VI surrounds the core. Ice-VI is water ice that can only be found in pressures that are extremely high.
The ice-VI has a salty liquid layer that surrounds it and that sits on a water ice outer crust. It’s thought that there are organic molecule on the surface that have settled there from the atmosphere in the form of liquids and sands or arrived when it rained.
The pressure on Titan is around 60% greater than that of Earth, and if you were standing on the surface of Titan it would feel like you are underwater on Earth around 50 ft/15 m.
Scientists consider the surface of Titan to be as close to that of Earth that we have found so far in the solar system. Of course, the chemistry is completely different and the temperatures on Titan are very cold.
The average Titan temperatures range are around -290 degrees F/-179 degrees C and is so cold that instead of rock like we have on Earth, Titan has ice.
If Titan does have any volcanic activity instead of the molten rock or lave that Earth has, Titan’s “lava” would be liquid water. The surface of Titan has evidence of a lot of river channels that were carved by ethane and methane.
There are large lakes filled with natural gas, giving the kind of surface liquid activity on Titan second only to Earth.
Titan has dark dune areas that stretch out across the equator area of its landscape. The “sand” dunes contain dark hydrocarbon grains that are believed to look a bit like coffee grounds.
If you looked at the dunes they might resemble the tall sand dunes of Africa. One of the things that scientists have noticed is that Titan doesn’t have very may impact craters that are visible.
This means that its surface must be somewhat young, as the moon’s renewal process covers over the impact evidence. On Earth, we have erosion, wind, and flowing water as well as new areas of lava or tectonic activity that covers over the evidence of some of the craters.
It’s thought that similar processes are happening on Titan, but in different ways. Titan’s underground activity is due to pressures from deep inside the moon, as scientists haven’t detected any of the type of tectonic plates that we have on Earth.
Titan has an incredible number of methane lakes that are located near the southern pole. In 2014, scientists found a feature on Titan that they have nicknamed “Magic Island.”
They believe that during some times the nitrogen bubbles that formed inside the oceans of Titan may be located on the surface and this creates a temporary island that will eventually fall apart. Planetary scientists have noted that Titan is the only world other than Earth that has stable liquid on its surface.
In the case of Titan, this liquid is ethane and methane seas, lakes, and rivers and Titan even has rain. Scientists are using Titan as an example of another type of hydrological cycle and are studying it as well as the Earth’s hydrological cycle.
The data and information received from spacecraft missions and Earth-based research suggests that there is a liquid ocean underneath Titan’s surface. This has yet to be completely confirmed, but it’s pretty exciting stuff.
The temperature on Titan is too cold for water ice to be on the surface but it may very well be underneath where temperatures are warm enough to melt the water ice.
Even though Saturn is far outside what scientists refer to as “the habitable zone,” it appears that Titan isn’t the only moon of Saturn that may have water beneath its surface.
Atmosphere and Magnetosphere:
Titan’s methane is in the form of a liquid but scientists think that this methane evaporates which forms clouds and even creates methane rain. There are clouds of cyanide gas and methane ice that are floating over the surface of Titan.
Scientists are astonished at how similar the natural processes of Titan are to Earth’s, even though the chemicals and materials are different.
Titan is an example of what they refer to as a “model of cloudy bodies,” which gives scientists a new view on alternative atmospheres that may look and act like those on Earth.
Saturn and its moons are at quite a distance from the sun and so the climate is driven by dim sunlight and low temperatures.
Using high tech telescopes, scientists have been able to detect and gauge activity in Titan’s atmosphere by looking at the sunsets.
The total atmosphere on Titan is around 95% nitrogen and 5% methane with other carbon-rich compounds in small amounts. The sun’s ultraviolet light splits apart the nitrogen and methane molecules and accelerates them into Saturn’s magnetic field.
These molecules dance around and reform into many different chemicals including hydrogen and carbon as well as the nitrogen and oxygen that we use as a gauge for the importance of life on our planet.
The smog or haze that surrounds Titan is created by some of the compounds that are split and reformed. Titan has an orange-colored thick haze that makes it very difficult to examine Titan from space.
Some telescopes and spacecraft do have the ability to peer into the various light wavelengths that expose information that we can’t see with the human eyes.
The 2004 Cassini mission discovered that the atmosphere of Titan extends out around 370 mi/600 km high.
Scientists have a difficulty figuring out if Titan has its own magnetic field. This confusion is based on the fact that the magnetosphere of Titan may be shielding the moon from the solar wind and influencing the magnetic fields in the atmosphere of the moon.
Could Life Exist?
Titan has an environment that is both similar and completely different than Earth’s, and yet as crazy as it sounds, Titan might be a place that could harbor life.
The basic requirements for life to form and thrive include liquid water, an energy source, and an atmosphere. Titan may have salty liquid water below its surface, does have an atmosphere, and has low-light from the sun.
Scientists have listed Titan as a potential location for life, although it would be below the surface and not life that we are familiar with.
Some scientists have conducted experiments using the type of UV radiation to create the kind of complex organic molecules that might be created from the atmosphere of Titan.
They have made the DNA and RNA and quite a few amino acids and proteins that are found in the atmosphere gases.
- Titan’s atmosphere is denser than that of Earth or Mars. It’s the only known moon to have a substantial atmosphere.
- The Cassini spacecraft did multiple flybys of Titan and found that the surface falls and rises by around 10 meters during one orbit. The shape changing is believed to be due to the movement of the moon’s crust as it orbits Saturn and is affected by Saturn’s gravity.
- Titan may have liquid on its surface but it isn’t water. The system of lakes, rivers and channels are filled with liquid hydrocarbons.
- On Earth we have volcanoes that spit out liquid rock in the form of lava. Scientists believe that Titan may have volcanoes but they spit out icy water and ammonia.
- Even though research has identified several mountains on Titan, none of them are very high.
- Scientists think the lake of high mountains on Titan may be due to the soft crust that Titan has that prevents the formation of high mountains.
- All of the mountains that have been found on Titan are named after mountains in J.R.R. Tolkien’s Middle-Earth. The Lord of the Rings trilogy has mountains whose names are now on Titan including: Angmar Mons, named after the Mountains of Angmar, Erebor Mons, named after Erebor [The Lonely Mountain], and Moria Mons, which is named after the Mountains of Moria.
- Titan has extensive sand dunes on its landscape and they are made up of organic soot. Some may be rock eroded by liquid methane and others are organic compounds that are from the atmospheric rain.
In the 1970s and 1980s the Voyager and Pioneer spacecraft did flybys of some of Saturn’s moons, supplying initial information and somewhat fuzzy images.
The 1997 Cassini spacecraft arrived at Saturn in 2004 and dropped the ESA Huygens probe on Titan to study the moon. The detailed data and images sent back allowed scientists to prioritize Titan as one of the moons to focus on.
The probe found mountains, complex organic chemistry, an atmosphere, seasonal changes, and a suspected subterranean ocean of water and ammonia.
Facts about Triton Moon for Kids:
- When looking at Titan, the first thing that you notice is its hazy and heavy atmosphere filled with a thick organic fog of nitrogen and its methane and ethane clouds.
- Titan has a diameter that is 50% bigger than our Earth’s moon and it is one of the largest moons in the solar system.
- Titan is made up of a surface of liquid hydrocarbon and has water ice on top of a possible rocky interior.
- Scientists think that Titan’s center core is hot and is surrounded by a layer of liquid water and ammonia.
- Titan and its parent planet, Saturn, are very close in age. Scientists think that Titan may have been created with left over materials from impacts when Saturn was first formed. | 0.874511 | 3.620674 |
The ASPA instrument had quite an unconventional birth compared to the usual remote sensing instruments that we develop at BIRA-IASB. It was designed, built, tested, and used without any dedicated budget line. Still, to my experience, its realization is a huge success given the limited resources (both in time and money) that were available. And this could only happen thanks to the motivation and commitment of the engineering department, which backed the ideas of some scientists to turn a nice concept on paper into a working and reliable instrument, operated in a harsh environment.
Since several years now, my physicist colleagues Gael Cessateur and Hervé Lamy were trying to measure a small feature of the Northern lights: a subtle polarization which had recently been discovered by a team of scientists from the University of Grenoble. The fact that some auroral spectral lines are polarized and some others are not is still puzzling the scientific community, which is calling for more experimental evidence.
Gael and Hervé had developed an instrument, Premier-Cru, whose concept was inspired by the French instrument that first detected this polarization. As this instrument never really delivered satisfactory results, they were open to new instrumental concepts capable of accurately measuring the polarization of auroras.
Interdisciplinary science with AOTF filters
I was totally ignorant about the physics of auroras, and my area of expertise was more into the remote sensing of atmospheric trace gases using optical instruments. The project I’m most involved in, namely ALTIUS, is a satellite instrument whose original concept is to use special spectral filters, called AOTFs, in order to analyze the absorption of natural light (Sun, stars) by the atmospheric molecules. Those filters work under the principle of light and sound interaction inside a transparent crystal of tellurium dioxide (TeO2). The fundamental physics of this interaction was developed by the French physicist Leon Brillouin in the 1920’s.
Actually, ALTIUS is not the first space instrument using AOTFs, neither was it the first time for BIRA-IASB to dive into this filter technology. Indeed, AOTFs have been used in planetary missions such as Venus Express, or ExoMars. No need to say that there was quite a lot of expertise in the Institute both in terms of controlling these devices, and understanding their behaviour.
The ALTIUS concept has also triggered a nice ground-based application: the NO2 camera. Originally a prototype of the visible channel of ALTIUS, I made it evolve into a field instrument capable of mapping the abundance of NO2, a harmful polluting species generated in combustion processes, above power plants, or cities. The NO2 camera is also based on an AOTF to take spectral images of the scene under investigation.
Exchanging with Gael and Hervé from time to time, we realized, bit by bit, that AOTFs could actually be the core of a new instrument dedicated to the measurement of the polarization of auroras. Indeed, one feature of the AOTFs is that they physically separate the incoming light into two components of perpendicular polarization. This feature is usually used to “clean” the light after crossing the AOTFs, keeping only one polarization for further analysis. But here, we could use it to its full potential.
ASPA had to grow up quickly
The real kick-off for ASPA took place in November 2019. This is when I started designing the instrumental concept, collecting opto-mechanical parts datasheets, and evaluating the performance of the future instrument.
Soon enough, I realized that auroras are not always the bright curtains dancing in the sky that we all know from documentaries. I had to be sure that the concept would be sensitive enough, at least down to some realistic brightness levels. Affordable detectors allowing to detect very faint signals are not really common, such that I had to work out the optical design to ensure that photons would not be lost on their way through the AOTF and to the detector. The crucial point was the focusing of the light beams onto the smallest possible amount of pixels, based on affordable optical elements, of course.
The manufacturing of the instrument turned out to be a race against the clock! Indeed, Hervé was planning to join two French teams by the end of February in Skibotn, in the North of Norway. The goal was to have ASPA there and ready to see its first auroras.
In December, engineers Sophie Berkenbosch and Jurgen Vanhamel had already started conceiving the electronic chain driving the AOTFs of ASPA. In January, most opto-mechanical parts had been purchased and delivered to BIRA-IASB, and the assembling of the elements could start. In the meantime, Claudio Queirolo (B.USOC operator and engineer) had produced a CAD (computer-aided design) model of the instrument, allowing to have a definitive view on the dimensions of the beast. This was needed to move on with the organization of all the different parts into a spare box we had from a different instrument. Engineer Pepijn Cardoen then took charge of the accommodation of all the parts into the housing: RF (radio-frequency) drivers, amplifiers, thermal sensors, heaters, inclinometers and fans found a cosy place next to the optical modules.
In parallel to the hardware work, engineer Roland Clairquin developed a control and acquisition software from scratch, making sure that all operating needs would be fulfilled in his code. During the first week of February, a first version of the software was available, and the instrument could go through a minimum set of laboratory tests. To my great relief, everything worked surprisingly well: the code was almost bug-free, the alignment of the optical elements was matching the drawings, and the behaviour of the AOTFs was just as in my computer model! The only thing that we couldn’t test was the operations in the campaign conditions.
And then, a week before the campaign, when the instrument and all the equipment was packed and ready to be shipped to Norway, trouble started…
In order to get our equipment in Norway, which lies outside Europe (in the world of border control and tariffs at least), we needed to get the “ATA carnet” from the Chamber of Commerce. Not the fastest procedure. It took a week and 350 EUR to receive it. We got it just a few days before we left, and the only shipping option left by then was DHL express: “24h delivery wherever in the world”. Well, forget about that!
The DHL adventure
First, it started with a DHL employee coming to pick up the parcels, and realizing he couldn’t take them because one of them was heavier than 30kg, something which was clearly indicated on the shipping order. Second, after a truck came to pick up our equipment, we received a first phone call asking for a pro forma invoice. Something you shouldn’t need when you have an ATA carnet. The day after, on Friday, it turned out they had lost the ATA carnet… but recovered it later that afternoon, only after the customs offices had closed for the weekend.
On Monday, the three parcels were still at DHL Brussels, and they forced us to produce a fake pro forma invoice in order to pass the customs. Due to customs closing at noon, they finally scheduled the shipment for the day after. On Tuesday, the three parcels finally passed customs, ready to be shipped during the night…but on Wednesday, it turned out that one of the three parcels (the one containing the RF equipment) was on its way to… wait for it… Madrid! Despite this, we decided to drive back from Skibotn to Tromsø to pick up the two parcels that had arrived, and pay the University of Tromsø a visit to find some replacement RF equipment. Thanks to the kind collaboration from the University of Tromsø, we were already able to re-build the instrument on Wednesday, and make it work, though not in ideal conditions.
On Thursday afternoon, the last parcel finally arrived in Tromsø. We went back to Tromsø to pick it up, each travel back and forth between Skibotn and Tromsø costing us a lot of time, fuel, and stress (driving hundreds of kilometers around the fjords, in winter conditions beyond the polar circle, is something Belgians are not used to). Ten days after the campaign, we received the bill from DHL (without any discount for the substandard services).
A happy end for ASPA?
Luckily, we didn’t miss any good opportunities to observe auroras while being stuck in limbo with the shipping of ASPA. On the flip side, we didn’t get any decent auroras during the last three nights of observation either. Only very few occurred in good visibility conditions (no clouds), and they were all extremely faint and definitely below the detection limit of ASPA: while the typical green auroras can be as bright as hundreds of kiloRayleigh (a unit to measure the brightness of airglow and auroras), the ones we saw remained below 1 kiloRayleigh, which was our ultimate detection limit.
What I take home from this endeavour is the wonderful commitment of many talented people from BIRA-IASB. Together, we managed to design, manufacture, and test a completely new instrument in barely two months! I am of course a little disappointed, because of the few and faint auroras we were given to observe during the three nights of observation with ASPA. I would have loved to be able to return with nice results, to show everyone it was worth working hard to be ready for the campaign, but nature (as well as DHL, apparently) is unpredictable. On the bright side: ASPA is on location and ready now. We will make a second attempt this fall until we get good observation conditions! | 0.803973 | 3.467298 |
In the singing climate of exoplanet KELT-9b, even particles are torn to shreds.
Enormous gas Goliath called “hot Jupiters”— planets that circle excessively near their stars to support life—are probably the most odd universes discovered past our nearby planetary group. New perceptions show that the most blazing of all is more odd still, inclined to planet-wide emergencies so extreme they destroy the atoms that make up its environment.
Called KELT-9b, the planet is a ultra-hot Jupiter, one of a few assortments of exoplanets—planets around different stars—found in our system. It tips the scales at about multiple times the mass of our own Jupiter and circles a star exactly 670 light-years away. With a surface temperature of 7,800 degrees Fahrenheit (4,300 degrees Celsius) – more smoking than certain stars—this planet is the most sizzling found up until this point.
Presently, a group of stargazers utilizing NASA’s Spitzer space telescope has seen proof that the warmth is as an excessive amount of in any event, for particles to stay unblemished. Particles of hydrogen gas are likely torn separated on the day side of KELT-9b, incapable to re-structure until their disconnected iotas stream around to the planet’s night side.
Despite the fact that still incredibly hot, the night side’s slight cooling is sufficient to permit hydrogen gas particles to change—that is, until they stream back to the day side, where they’re destroyed once more.
“This kind of planet is so extreme in temperature, it is a bit separate from a lot of other exoplanets,” said Megan Mansfield, an alumni understudy at the University of Chicago and lead creator of another paper uncovering these discoveries. “There are some other hot Jupiters and ultra-hot Jupiters that are not quite as hot but still warm enough that this effect should be taking place.”
The discoveries, distributed in Astrophysical Journal Letters, feature the rising advancement of the innovation and examination expected to test these exceptionally removed universes. Science is simply starting to look into the airs of exoplanets, inspecting the atomic emergencies of the most smoking and most brilliant.
KELT-9b will remain solidly ordered among the dreadful universes. Cosmologists got mindful of its incredibly unfriendly condition in 2017, when it was first recognized utilizing the Kilo degree Extremely Little Telescope (KELT) framework—a consolidated exertion including perceptions from two mechanical telescopes, one in southern Arizona and one in South Africa.
In the Astrophysical Journal Letters study, the science group utilized the Spitzer space telescope to parse temperature profiles from this diabolical goliath. Spitzer, which mentions objective facts in infrared light, can gauge inconspicuous varieties in heat. Rehashed over numerous hours, these perceptions permit Spitzer to catch changes in the climate as the planet presents itself in stages while circling the star. Various parts of the planet fold into see as it circles around its star.
That permitted the group to get a look at the distinction between KELT-9b’s day side and its “night.” For this situation, the planet circles its star so firmly that a “year”— once around the star—takes just 1/2 days. That implies the planet is tidally bolted, introducing one face to its star forever (as our Moon displays just one face to Earth). On the most distant side of KELT-9b, evening time keeps going forever.
Yet, gases and warmth stream from one side to the next. A central issue for scientists attempting to comprehend exoplanet airs is the means by which radiation and stream balance each other out.
PC models are significant apparatuses in such examinations, indicating how these environments are probably going to act in various temperatures. The best fit for the information from KELT-9b was a model that included hydrogen particles being destroyed and reassembled, a procedure known as separation and recombination.
“If you don’t account for hydrogen dissociation, you get really fast winds of [37 miles or] 60 kilometers per second,” Mansfield said. “That’s probably not likely.”
KELT-9b turns out not to have colossal temperature contrasts between its day-and night sides, proposing heat stream from one to the next. Furthermore, the “problem area” on the day side, which should be straightforwardly under this current planet’s star, was moved away from its normal position. Researchers don’t have the foggiest idea why—one more puzzle to be explained on this bizarre, hot planet.
Caylee Baker is most will known for her stories. She writes stories as well as news related to science. She wrote number of book in her 3 years of career. And out of those books she sale around 10 books. She was more experience in online news writing. | 0.857519 | 3.95945 |
Vega VV06, in its mobile gantry, is all set for the launch of LISA Pathfinder, ESA's technology demonstrator that will pave the way for detecting gravitational waves from space.
Liftoff is planned at 04:04 GMT (05:04 CET) on 3 December.
Vega will place LISA Pathfinder into an elliptical orbit around our planet. Then, the spacecraft will use its own propulsion module to raise the highest point of the orbit in six stages. The last burn will propel the spacecraft towards its operational orbit, around a stable point called L1, some 1.5 million km from Earth towards the Sun.
Once on its final orbit, LISA Pathfinder will test key technologies for space-based observation of gravitational waves. These ripples in the fabric of spacetime are predicted by Albert Einstein’s general theory of relativity but have not yet been directly detected.
To demonstrate the fundamental approach that could be used by future missions to observe these elusive cosmic fluctuations, LISA Pathfinder will realise the best free-fall ever achieved in space. It will do so by reducing all the non-gravitational forces acting on two cubes and monitoring their motion and attitude to unprecedented accuracy. | 0.872859 | 3.07373 |
Monday, July 01, 2019
Lucie Green - 15 Million Degrees: A Journey to the Centre of the Sun
Lucie Green is a longstanding solar scientist. She is also a well known broadcaster and an excellent communicator of complex scientific ideas. This latter point is important because to understand the Sun requires some getting to grips with some fundamental physics and the concepts are not always easy to understand. So the opening chapter begins with an account of the development of our understanding of electromagnetism - we need to know this because it helps us understand the information we are receiving from the Sun via the light we receive (both visible and other parts of the electromagnetic spectrum). Knowing this helps us understand what's going on inside the Sun. Green then takes us through the history of studies of the Sun and shows how we have built on several centuries of observations and science.
This is science on a massive scale. The Sun itself is big - even just on the scale of what we can see. But the Sun's outer atmosphere (invisible to human senses) extends beyond the Earth itself, and the influence of the Sun, in terms of the solar wind, extends a very long way indeed beyond the outermost planet. I recently enjoyed Jim Bell's account of the Voyager missions The Interstellar Age, and Green explains just why the ongoing science obtained from those two ageing craft is so important. But the Sun is also huge in terms of the energy it produces and the length of time it has been doing this for. Even with my own knowledge of nuclear physics and astronomy I was still fascinated by Green's account of the Sun's formation and the fusion in its core. We are, Green explains, fortunate that our modern scientific era, and especially the space age have coincided with a particularly fascinating era of the Sun's cycles. But we have been, since around 1985 observing the Sun leaving it's "Grand Maximum State" and the Sun is likely to become relatively dimmer in coming decades. Here Green explains precisely why, contrary to the heartfelt beliefs of various commentators on climate change science, this will have no serious impact on global temperatures. One thing that becomes very clear is just how many of the processes that we observe are the result of complex magnetic interactions throughout the different layers of the Sun - I was quite amazed to find out that we have managed to observe the magnetism of other stars, though disappointed not to be told more about how! Despite Green's ability to communicate complex ideas I did struggle to follow some of the descriptions of what was taking place - my advice to other readers is not to worry too much if you can't understand all the detail - the big picture is very much the key issue.
One of the great things about the book is the way that Green links the Sun to our own lives and society. She shows how the Sun is responsible for life (and civilisation) but also the threats it can have to modern technology and society. The end of the book discusses the uniqueness of our Sun, when compared to the billions of other stars. Lucie Green concludes that while the Sun is not that unique in astronomical terms, it is in the sense that it is the one that we can study and that gave rise to life here. So I recommend 15 Million Degrees very much, not just because it's fascinating science, but also because it's subject, the Sun, is part and parcel of our life on this planet.
Winterburn - The Quiet Revolution of Caroline Herschel: The Lost Heroine of Astronomy
Bell - The Interstellar Age
Clegg - Gravity: Why What Goes Up, Must Come Down
Holmes - The Age of Wonder | 0.862765 | 3.695836 |
Each Voyager spacecraft carries a phonograph record--a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. . Image: NASA JP
Thirty-three years into its voyage into deep space the space-hardened craft of Voyager 1 nears a milestone in its journey out of the solar system. But within this small craft is a gold plated copper record disc with 115 images and natural sounds of nature as well as songs of celebration and greetings from a small pale dot in the vast black void of our solar system called Earth: Allen L Roland
Professor Edward Stone, was asked in 1972 to work part-time at NASA’s Jet Propulsion Laboratory as chief scientist for a new space mission, one that would probe the limits of the solar system and eventually enter interstellar space ~ and now, 33 years after the launch of Voyager 1 and 2 , he says the goal is in sight.
Harvey Leifert writes in Scientific America of this historic event ~ "Voyager 1 is the most remote human-made object," Stone says. "It's now 115 astronomical units from Earth," that is, 115 times farther than Earth is from the sun, or "a bit more than 10 billion miles [16 billion kilometers]." Voyager 2 has traveled somewhat slower and in a different direction and is now around 14 billion kilometers from Earth.
Both Voyagers are still within a "bubble" created by the solar wind, a stream of charged particles radiating outward from the sun at 1.6 million to 3.2 million kilometers per hour. This bubble, or heliosphere, exists, says Stone, because a magnetic field from outer space, likely resulting from the explosion of supernovae five million to 10 million years ago, is pushing back against the solar wind.
In the past six months, Voyager 1 has signaled that the radial speed of the solar wind is zero, meaning that the spacecraft is approaching the final boundary of the solar system, the heliopause. Stone and his colleagues had not expected Voyager to reach this point for several more years, meaning that the boundary lies closer to the sun than they had thought.
It may take a year or more of data analysis to confirm that Voyager 1 has actually crossed the heliopause, which is a flexible boundary, Stone says. There probably will not be a eureka moment when it happens. We will continue to receive data from the Voyagers until around 2020 or 2025, Stone says, well after they have left the solar system.
Leaving the solar system, he says, will be "a milestone in human activity." Both Voyagers will likely outlive Earth, he notes. When, billions of years from now, the sun swells into a red giant, the Voyagers, albeit with their radioactive generators long exhausted and instruments frozen, will continue to wend their lonely ways through interstellar space and remain on course for the unknown, bearing a record disk and images of 20th-century Earth, music from many of its cultures, and greetings in dozens of its languages. They may be the only evidence the human race ever existed." http://www.scientificamerican.com/article.cfm?id=cosmos-incognita-voyager&WT.mc_id=SA_WR_20101221
The contents of that copper record disc were selected for NASA by a committee chaired by the late Carl Sagan of Cornell University. Sagan and his associates assembled 115 images and a variety of natural sounds, such as those made by surf, wind and thunder, birds, whales, and other animals. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in 55 languages, along with printed messages from President Jimmy Carter and U.N. Secretary General Kurt Waldheim.
So now imagine, if you will, at some point of distant time ~ an Intergalactic spaceship retrieving a seemingly lost frozen space vehicle and cautiously examining its contents and coming across this strange gold-plated copper disc. Of course, they may not be able to fully decipher the languages but the music most certainly would connect to them. And here is a song, composed by Scott Deturk and sung by myself, that I suggest just might give them a heart felt glimpse of our mother earth and its inhabitants. Click on and enjoy ~
Allen L Roland
Freelance Alternative Press Online columnist and psychotherapist Allen L Roland is available for comments, interviews, speaking engagements and private consultations ( [email protected] )
Allen L Roland is a practicing psychotherapist, author and lecturer who also shares a daily political and social commentary on his weblog and website allenroland.com He also guest hosts a monthly national radio show TRUTHTALK on www.conscioustalk.net | 0.838021 | 3.604862 |
Exactly how much time is there in a day?
The length of a day is determined by the movements of the earth and the sun. While the earth rotates on its axis as it revolves around the sun, a day is defined as the average time between the transit time when the sun is due south, and the following transit time. This average time is defined as 24 hours, and is referred to as “one solar day.”
Actually, since the orbital path the earth takes around the sun is elliptical, and the earth’s rotational axis is tilted away from the plane of revolution, the apparent movement of the sun speeds up and slows down throughout the year, but since it would be inconvenient to have days of differing lengths, the average length of 24 hours was adopted for use, and is referred to as “mean solar day.”
Incidentally, the length of a single second was originally derived by dividing up the 24-hour-long mean solar day that was measured based on astronomical observations (24 hours ÷ 24 ÷ 60 minutes ÷ 60 seconds), but the movements of celestial bodies produce an error that cannot be predicted.
Given this, since 1967 a more accurate second has been defined as the frequency of electromagnetic waves emitted by a cesium-133 atom, which comprises 9,192,631,770 periods of radiation. This “cesium second” is then multiplied (1 sec. x 60 x 60 min. x 24 hours) to determine the length of 24 hours in a day.
The reason we need to make leap year adjustments is because the time it takes for the earth to make one complete revolution around the sun (one solar year) is not exactly 365 days, but in fact around one quarter of a day longer, at 365.2422 days (365 days, 5 hours, 48 minutes and 46 seconds).
The fact that a year lasts around a quarter-day longer than 365 days had already been discovered during the B.C. era through astronomical observations, and to correct for this, in 45 B.C. the Julian calendar took effect, establishing a leap year every four years and adding one an extra day (leap day) to the month of February during that year.
Many years later, a discrepancy of ten days had built up between spring equinox as an observable astronomical event and spring equinox according to the Julian calendar. The discrepancy was such that the Roman Catholic church could no longer ignore it.
Finally in the late 16th century, Pope Gregory XIII demonstrated through more accurate astronomical observations that a year was not in fact 0.25 days longer than 365 days, but in fact 0.2422 days long (shorter by 0.0078 days), and thus instituted the Gregorian calendar reform.
This correction became the Gregorian calendar, which was established in 1582 and is still used to this day. The specific changes to correct for the error stipulated that leap years would not be established in years exactly divisible by 100 (once every 100 years), except for years exactly divisible by 400, such as the year 2000. Through these calculations, the correction that shaved just 11 minutes and 14 seconds (0.0078 days) from the 365 days and six hours originally defined was achieved.
The Story of Calendar Reform in Japan
Before calendar reform was carried out in 1873, Japan used the Tempo Calendar, a kind of lunar-solar calendar. On November 9, 1872, the government suddenly announced an imperial edict and Grand Council of State proclamation for calendar reform. The proclamation stated that the lunar-solar calendar would be abolished on the upcoming date of December 2, with January 1 of the new year (1873) beginning on December 3, marking the switch to a solar calendar.
The lunar-solar calendar required the addition of a leap month around once every three years, and required complex handling due to conflicts with the preceding and succeeding seasons each time. Given this, the rational decision was made to adopt the same solar calendar used by many other countries.
However, behind the Meiji government’s immediate action to suddenly enact calendar reform lies speculation as to the true motives. With the new government facing a drain on its finances, the leap month in the sixth year of the Meiji Era (the following year) would have meant adding a 13th month, and by ending December of the fifth year of the Meiji Era in just two days, the reform meant that the government effectively saved on two months of salaries.
Perhaps because the decisions was made to reform a lunar-solar calendar that had been in effect for more than a millennium just three weeks hence, in fact the solar calendar that was first adopted was the Julian calendar, which only called for establishing leap years once every four years. For this reason, in 1898 it was decided that Japan would adopt the Gregorian calendar from 1900, thereby avoiding the imposition of a leap year that would set Japan one day apart from the rest of the world.
What is the relationship between leap years and leap seconds?
While leap years serve to correct for the error in the revolutions of the earth around the sun, leap seconds correct for the error in the earth’s own rotation. Leap years and leap seconds are therefore not directly related to one another.
As we mentioned at the start, there is a slight error in the rotation of the earth, and to correct for the variation between the accurate one-second period that currently uses cesium atoms as a reference and the rotating action of a solar day in which the earth rotates once every 24 hours on average, every several years the time is adjusted using a “leap second.”
Leap seconds are carried out when needed by inserting or removing one second based on minute variations in the auto-rotational speed the earth actually makes. Unlike leap years which are based on the regular orbit of the earth around the sun, as there is no regularity to the speed of rotation, there is no pre-determination as to when a leap second should be implemented.
In fact, short-term predictions looking one or two years into the future are made based on various observations, and when it is deemed necessary, a one-second time adjustment in the form of a leap second is made.
Leap second corrections in practice
In fact, Coordinated Universal Time, or UTC, was established in 1972. A single universal time was determined according to astronomical observations and designated UT1, and corrections of one-second increments were stipulated to ensure that the international atomic time (TAI) set according to an atomic clock stayed within a variance of 0.9 seconds.
Since UTC was implemented in 1972, leap seconds have already been inserted 27 times (as of January 2017).
The corrections are carried out on January 1 or July 1. In Japan, immediately after 8:59:59 according to Japan Standard Time, the time 8:59:60, which is not regularly seen, is added, thus setting the recorded time back by one second. This occurs at 9:00 a.m. in Japan because it corresponds to midnight Greenwich Mean Time.
Why does the earth’s rotation undergo slight variations?
Once we began using atomic clocks, which vary less than a second over a period of tens to hundreds of millions of years, we noticed a one-second variation in the earth’s rotation every year to several years. Why does this deviation occur?
Tidal forces imposed on the oceans due to the gravitational attraction of the moon and sun are believed to have a significant effect on the earth’s rate of rotation.
As the moon has a slower period of revolution of approximately 29.5 days compared to the once-daily rotational speed of the earth, seawater that swells in an elliptical pattern primarily at the plane of the ecliptic moves relatively less while the friction produced between the seawater and the shore or seafloor produces a braking effect. In this way, the rotational speed of the earth gradually decreases each year.
However, as this deceleration is on the order of 0.0017 seconds per 100 years, by simple calculation we can deduce that it will take around 60,000 years for the rotational speed to increase by a full second, so this is not the main reason behind the current leap second corrections.
Considered as a cycle lasting from several years to around two decades, changes in the motion of the “core” at the center of the earth and complex factors such as the distribution of water (seawater, inland water and glaciers) on a global scale produce subtle variance in the earth’s rotational speed.
To date, all of the corrections made have involved inserting a second to correct for a slowing in the earth’s rotational speed, but as we are unable to predict the irregular cyclical movements of the earth, it is possible that in the future, we may have to remove a second to correct for advances in rotational speed.
・National Institute of Information and Communications Technology (NICT) website
・National Astronomical Observatory, National Institutes of Natural Sciences | 0.816921 | 3.912956 |
Photo Credit: NASA/JPL-Caltech
The slow fade of radioactive elements following a supernova allows astrophysicists to study them at length. But the universe is packed full of flash-in-the pan transient events lasting only a brief time, so quick and hard to study they remain a mystery.
Only by increasing the rate at which telescopes monitor the sky has it been possible to catch more Fast-Evolving Luminous Transients (FELTs) and begin to understand them.
According to a new study in Nature Astronomy, researchers say NASA’s Kepler Space Telescope captured one of the fastest FELTs to date. Peter Garnavich, professor and department chair of astrophysics and cosmology physics at the University of Notre Dame and co-author of the study, described the event as “the most beautiful light curve we will ever get for a fast transient.”
“We think these might actually be very common, these flashes, and we have just been missing them in the past because they are so fast,” Garnavich said. “The fact that one occurred in the small area of the sky being monitored by Kepler means they are probably fairly common.”
The FELT, captured in 2015, rose in brightness over just 2.2 days and faded completely within 10 days. Most supernovae can take 20 days to reach peak brightness and weeks to become undetectable.
Researchers debated what could be causing these particularly fast events but ultimately settled on a simple explanation: The stars “burp” before exploding and don’t generate enough radioactive energy to be seen later. As the supernova runs into the gas expelled in the burp, astrophysicists observe a flash. The supernova then fades beyond their ability to detect it.
“Our conclusion was that this was a massive star that exploded, but it had a mass loss — a wind — that started a couple of years before it exploded,” Garnavich described. “A shock ran into that wind after the explosion, and that’s what caused this big flash. But it turns out to be a rather weak supernova, so within a couple of weeks we don’t see the rest of the light.”
The only visible activity is from the quick collision of the gas and the exploding star, where some of the kinetic energy is converted to light. One mystery that remains is why the “burp” would happen such a short time before the supernova explosion. Astrophysicists want to know how the outside of the star reacts to what’s happening deep in the core, Garnavich said.
While the Kepler telescope and its K2 mission is expected to run out of fuel and end in the coming months, NASA’s Transiting Exoplanet Survey Satellite (TESS) is planned for launch following the K2 mission. Garnavich said data retrieved during the TESS mission could also be used to study FELTs.
The study was funded by NASA.
The study was led by Armin Rest at the Space Telescope Science Institute. Co-authors include Giovanni Strampelli, also at the Space Telescope Science Institute; David Khatami and Daniel Kasen at the University of California Berkeley and Lawrence Berkeley National Laboratory; Brad E. Tucker, research fellow at the Research School of Astronomy and Astrophysics, Mount Stromlo Observatory and the ARC Centre of Excellence for All-Sky Astrophysics; Edward J. Shaya, Robert P. Olling and Richard Mushotzky at the University of Maryland; Alfredo Zenteno and R. Chris Smith at the Cerro Tololo Inter-American Observatory; Steve Margheim at the Gemini Observatory; David James and Victoria A. Villar at the Harvard-Smithsonian Center for Astrophysics; and Francisco Förster at the University of Chile.
Contact: Jessica Sieff, assistant director, media relations, 574-631-3933, [email protected]
Originally published by news.nd.edu on March 28, 2018.at | 0.884198 | 4.068617 |
The Oort Cloud
In 1932 the Estonian astronomer Ernst Opik (1893-1985) proposed that long-period comets came from an orbiting cloud at the outer limits of our Solar System. The Dutch astronomer Jan Oort independently gave new life to this theory in 1950 in an effort to resolve a paradox.
Over the course of our Solar System’s history the orbits of comets have become unstable and ultimately dynamics dictate that a comet must either crash into the Sun or a planet or, alternatively, be rudely evicted from our Solar System altogether by planetary gravitational perturbations. Furthermore, their volatile composition means that, as they repeatedly migrate towards our Sun, radiation eventually boils the volatiles away until the comet either fragments or forms an insulating crust that shields it from additional outgassing.
Taking everything into account, Oort reasoned that a comet could not have formed while in its current orbit. Instead, it must have inhabited a frigid outer reservoir of comet nuclei for almost its entire existence.
Estimates have placed the outermost edge of the Oort cloud between 100,000 and 200,000 AU. The region itself can be subdivided into a spherical outer Oort cloud of 20,000 to 50,000 AU, and a torus-shaped inner Oort cloud at 2,000 to 20,000 AU. The outermost region of this vast cloud is only weakly bound gravitationally to our Star and it is the original home of the long-period comets that invade the inner Solar System. The inner Oort cloud, known as the Hills cloud, is named in honor of Dr. Jack G. Hills, a retired Laboratory Fellow of the Los Alamos National Lab (New Mexico), who proposed its existence in 1981. Models predict that the inner cloud should host tens or hundreds of times more cometary nuclei than the outer halo–and it is a possible source of new comets that resupply the thin and delicate outer cloud, as the latter’s numbers gradually diminish. The Hills cloud does, indeed, explain the continued existence of the Oort cloud over a time span of billions of years.
The Oort cloud itself is believed to be a lingering relic of the original protoplanetary accretion disc that formed around our newborn Sun. The most widely accepted theory suggests that the Oort cloud’s numerous icy inhabitants first coalesced closer to our brilliant, hot, and fiery baby Sun as part of the same process that created both the eight major planets, as well as the minor planets. However, a gravitational dance with youthful gas-giants like Jupiter hurled these objects into extremely long elliptical or parabolic orbits. Indeed, recent research conducted by NASA scientists indicates that our Sun’s sibling stars (stars that were born in the same stellar cluster as our Sun) eventually drifted apart, and went their separate ways, when they were still young. In addition, many–possibly even the majority– of icy Oort cloud denizens did not form close to our Star. Supercomputer simulations of the evolution of the Oort cloud from the birth of our Solar System to the present indicate that the cloud’s mass peaked approximately 800 million years after its formation, as the rate of accretion and collision slowed down, and depletion started to overtake supply. mkvking | 0.900924 | 4.044958 |
Inside atomic nuclei, protons and neutrons fill space with a packing density of 0.74, meaning that only 26 percent of the volume of the nucleus in is empty.
That’s pretty efficient packing. Neutrons achieve a similar density inside neutron stars, where the force holding neutrons together is the only thing that prevents gravity from crushing the star into a black hole.
Today, Felipe Llanes-Estrada at the Technical University of Munich in Germany and Gaspar Moreno Navarro at Complutense University in Madrid, Spain, say neutrons can do even better.
These guys have calculated that under intense pressure, neutrons can switch from a spherical symmetry to a cubic one. And when that happens, neutrons pack like cubes into crystals with a packing density that approaches 100%.
Anyone wondering where such a form of matter might exist would naturally think if the centre of neutron stars. But there’s a problem.
On the one hand, most neutron stars have a mass about 1.4 times that of the Sun, which is too small to generate the required pressures for cubic neutrons. On the other, stars much bigger than two solar masses collapse to form black holes.
That doesn’t leave much of a mass range in which cubic neutrons can form.
As luck would have it, however, last year astronomers discovered in the constellation of Scorpius the most massive neutron star ever seen. This object, called PSR J1614-2230, has a mass 1.97 times that of the Sun.
That’s about as large as theory allows (in fact its mere existence rules out various theories about the behaviour of mass at high densities). But PSR J1614-2230 is massive enough to allow the existence of cubic neutrons.
Astrophysicists will be rubbing their hands at the prospect. The change from spherical to cubic neutrons should have a big influence on the behaviour a neutron star. It would change the star’s density, it’s stiffness and its rate of rotation, among other things.
So astronomers will be getting their lens cloths out and polishing furiously in the hope of observing this entirely new form of matter in the distant reaches of the galaxy. | 0.806884 | 3.795781 |
Consider the possibility that an asteroid may have transformed the picture of life on Earth—but forget the dinosaurs and the massive crater, and rewind an extra 400 million years from that dramatic moment.
Back then, life was primarily an oceanic affair and backbones were the latest in arrival on the anatomy scene. But unlike the asteroid that killed the dinosaurs 66 million years ago, this earlier space rock never made it to Earth. Instead, a collision in the asteroid belt flooded the solar system with so much dust that, given some other changes at the time, allowed life on Earth to flourish, new research suggests.
“Most important events in the history of life are like that,” said Rebecca Freeman, a paleontologist at the University of Kentucky who specializes in this period but wasn’t involved in the new research. “You get a really unique set of circumstances that all come together, and you get a really dramatic event that maybe seems like it should be due to one particular dramatic thing. But in reality, it’s a more complicated system at play,” she told Space.com.
The dramatic event scientists want to explain is a spree of new species. That outburst of life, which paleontologists call the Great Ordovician Biodiversification Event, took place in the oceans, which were inhabited mostly by spineless creatures. “This is really a world that is dominated by invertebrate marine organisms,” Freeman said. “Probably the top predator would have been a cephalopod,” likely an ancestral relative of today’s chambered nautilus, with its intricate spiral shell.
But when Birger Schmitz, a geologist at Lund University in Sweden, went hunting for rock dating back 466 million years, he wasn’t hoping to find fossilized nautiluses; he was looking for fossilized meteorites. And over the past couple of decades, he and his colleagues have found dozens of these fossilized meteorites in a Swedish limestone quarry. Each carries a chemical time stamp indicating that it was heated about 470 million years ago, and scientists have thought for a while that there might have been a massive asteroid collision around that time.
“For 25 years, I’ve had a gut feeling that this must somehow have had an effect on Earth, on life in particular,” Schmitz said. “I felt there has to be some kind of connection.” So he and his team looked to the rock. In the paper, the researchers drew on two key threads of evidence: a special form of helium and a mineral carried to Earth by meteorites.
They wanted something more difficult to find than fossilized meteorites: micrometeorites, which, like their larger siblings, carry the mineral chromite. “There are a lot more micrometeorites falling on Earth than larger meteorites, so I got one of the most crazy ideas I’ve had, I think,” Schmitz said. “It wasn’t that crazy, but at the time, it felt crazy.”
It meant the team had to get awfully destructive. “How would you do it if you want to find a needle in a haystack?” Schmitz said. “It’s quite easy: You burn the haystack away. And this is what we do.” When your haystack is limestone, burning it means dumping it—2,870 lbs. (1,300 kilograms) of it—into hydrochloric acid to eat away the rock, leaving chromite grains behind. “They survive everything,” he said of the chromites. “They survive 500 million years in the sediment; they survive all our acid treatment.”
Levels of both the chromite grains and the exotic helium skyrocketed around this period—but not at precisely the same time. First, the rock shows a slow increase in extraterrestrial chromite that lasted between 2 million and 4 million years. A subset of that stretch shows a sharp increase in the grains from a particular category of meteorites, and another subset coincides with the arrival of the fossilized meteorites that have informed Schmitz’s previous research. Another slightly skewed timeline charts the arrival of the extraterrestrial flavor of helium.
For Schmitz, all of those factors come together to suggest that a massive, distant asteroid collision did indeed affect life on Earth. He and his colleagues suggested that this breakup—of an asteroid stretching nearly 100 miles (150 kilometers) across—filled the inner solar system with meteorites and asteroid dust. Larger chunks would have spread from the collision site faster than smaller pieces.
The team proposed three ways in which so many asteroid fragments could affect Earth, cooling the planet. Perhaps the particles reaching Earth carried enough iron into the ocean that plant life dramatically flourished there, feasting on carbon dioxide and pulling it out of the atmosphere, the reverse of today’s conditions. Or maybe particles strewn across the solar system blocked sunlight from reaching Earth.
The third possibility the team offered was that such cosmic dust trapped in Earth’s atmosphere could have reflected sunlight away from Earth. That’s the most plausible of the three scenarios, according to John Plane, an atmospheric chemist at the University of Leeds in the U.K. who studies cosmic dust in planetary atmospheres and has run models of the impact of increased dust levels on the climate.
The levels proposed in the new research are about 1,000 times the current levels of cosmic dust in Earth’s atmosphere, which causes some subtle phenomena on our planet today, Plane said. “But obviously, if you increase it by 1,000, then there’s no question it could have all of the effects that they’re talking about.”
Overall, Plane thought the research was intriguing. “They’ve made what I would regard as a pretty compelling case, which now needs to be investigated in a lot more detail,” he said. “I think it’s a very nice piece of work.”
But the paper doesn’t give the asteroid’s debris all the credit for that spree of diversification. That’s good, Freeman said, because many other factors would have played a role, like ocean circulation patterns and sea level rise. One particularly important factor is how land and the ocean were spread across Earth’s surface at that time, with small continents stretching from the equator to the South Pole, offering many different niches for species to adapt to, she said.
“Continents move around really slowly, and so one of the things that’s important for making these species is that you isolate populations,” Freeman said. “You can find ways to link this supposed asteroid explosion space dust idea into a lot of different things; one thing you can’t really blame on the asteroid is where the continents were.”
The famous dinosaur scenario has led paleontologists to suspect asteroids as culprits in other events, she said. (Although some scientists think other factors played a role, there’s still a clear connection between the impact and the mass extinction.) “That sent everybody into a frenzy of trying to blame meteorites for everything,” Freeman said. “As a community, we’ve maybe pulled away from wanting to blame everything on things from outer space, but they’ve got some really great documentation here.”
From that documentation, Schmitz is even willing to describe what time travelers might see if they stopped to visit the mighty nautiluses of the era.
“There would have been a lot more meteorites, light streaks,” Schmitz said. “You could stand there, wishing things all the time, because there would be a lot of these light streaks from the sky with all the dust coming in.”
The research is described in a paper published on Sept. 18 in the journal Science Advances.
Copyright 2019 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. | 0.826573 | 3.591924 |
Crescent ♈ Aries
Moon phase on 26 June 2008 Thursday is Last Quarter, 22 days old Moon is in Aries.Share this page: twitter facebook linkedin
Last Quarter is the lunar phase on . Seen from Earth, illuminated fraction of the Moon surface is 50% and getting smaller. The 22 days old Moon is in ♈ Aries.
* The exact date and time of this Last Quarter phase is on 26 June 2008 at 12:10 UTC.
Moon rises at midnight and sets at noon. It is visible to the south in the morning.
Moon is passing about ∠5° of ♈ Aries tropical zodiac sector.
Lunar disc appears visually 1.5% wider than solar disc. Moon and Sun apparent angular diameters are ∠1917" and ∠1887".
Next Full Moon is the Buck Moon of July 2008 after 21 days on 18 July 2008 at 07:59.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 22 days old. Earth's natural satellite is moving through the last part of current synodic month. This is lunation 104 of Meeus index or 1057 from Brown series.
Length of current 104 lunation is 29 days, 6 hours and 56 minutes. This is the year's shortest synodic month of 2008. It is 58 minutes shorter than next lunation 105 length.
Length of current synodic month is 5 hours and 48 minutes shorter than the mean length of synodic month, but it is still 21 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠4.4°. At beginning of next synodic month true anomaly will be ∠20.1°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
9 days after point of apogee on 16 June 2008 at 17:33 in ♏ Scorpio. The lunar orbit is getting closer, while the Moon is moving inward the Earth. It will keep this direction for the next 5 days, until it get to the point of next perigee on 1 July 2008 at 21:22 in ♊ Gemini.
Moon is 373 993 km (232 388 mi) away from Earth on this date. Moon moves closer next 5 days until perigee, when Earth-Moon distance will reach 359 513 km (223 391 mi).
3 days after its ascending node on 22 June 2008 at 23:17 in ♒ Aquarius, the Moon is following the northern part of its orbit for the next 9 days, until it will cross the ecliptic from North to South in descending node on 5 July 2008 at 15:53 in ♌ Leo.
3 days after beginning of current draconic month in ♒ Aquarius, the Moon is moving from the beginning to the first part of it.
8 days after previous South standstill on 18 June 2008 at 09:08 in ♐ Sagittarius, when Moon has reached southern declination of ∠-27.510°. Next 5 days the lunar orbit moves northward to face North declination of ∠27.541° in the next northern standstill on 1 July 2008 at 21:36 in ♊ Gemini.
After 6 days on 3 July 2008 at 02:19 in ♋ Cancer, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.16433 |
In the Australian outback sits a forest of spider-like antennas, gathering data from the distant reaches of the universe. It’s the Murchison Widefield Array, a radio telescope array that uses low-frequency radio waves to detect and study things like hydrogen emissions, the ionosphere, supernovae, and more.
This summer, four UWM undergraduates spent a week building those antennas.
Physics majors Rusty Mundorf, Kaleb Maraccini, William Fiore and Robert Bavisotto are all undergraduate researchers who work with UWM Physics professor David Kaplan. When Kaplan needed a crew to work on expanding the MWA, they each applied.
“We were responsible for the hex, which is a section of the telescope,” Mundorf explained. “We built 576 of those little antennas and went and put them out on the field and wired them so they could be hooked up to the computers for analysis.”
It’s a small thing now, but it could generate big results later. The MWA is an international collaboration among several universities and organizations, each studying different astronomical phenomena. Kaplan’s group at UWM uses the data collected from the array and other locations to search for pulsars.
“Pulsars are rapidly spinning neutron stars (leftovers from supernova explosions) which emit radio waves from their poles, creating a lighthouse effect whereby if the Earth is in the path of the pulsar’s beam of radiation, we see a “pulse” of radio waves,” Fiore said. “Pulsars are the densest objects in the universe apart from black holes, and are typically about the size of Milwaukee.”
Sometime in the future, the MWA, and the antennas built by the UWM students, might be able to use the pulsars to detect gravitational waves, ripples in the fabric of space-time predicted by Albert Einstein and recently proved to exist by a team from the Laser Interferometer Gravitational-Wave Observatory (LIGO), which included scientists from UWM.
“The LIGO announcement was really exciting. That was really cool thinking about all of the years that went into that project,” Maraccini said. “When NANOGrav (the organization Kaplan belongs to searching for pulsars) discovers gravitational waves, it’ll be really cool to be a part of that.”
“It’s always interesting to see the practical side of science, and there is a sense of pride in seeing something that you’ve built after a week of work, knowing that someone will use it to study something meaningful in the future,” Fiore added.
The students spent five days on the project in the Outback. The area around the MWA is a “radio quiet” area, meaning all radio transmissions, from car radios to microwaves to cellphone signals, must be silenced so they don’t interfere with the MWA’s data collection. The area itself is isolated and can only be reached via a long ride on dirt roads.
The work was repetitive, so much so that Mundorf bragged he could assemble a dipole antenna blindfolded by the end of it. He couldn’t, but did come close, he reported with a laugh. The students would be working on-site by 7:30 in the morning and work until about 4 or 4:30 p.m.
“For me, it was really fun, and really cool, learning more about how the MWA works,” said Maraccini. “I was taken aback by all the logistics of working on telescopes like these.”
The MWA involves miles of wire to carry data back to computers for analysis, and the instruments are very sensitive. That’s good for research but can be a problem when it comes to maintenance. Maraccini learned how the iron in Australian soil can corrode the array, especially during a wet season.
After the project ended, Fiore and Maraccini stayed behind in Australia for more research while Mundorf and Bavisotto returned to the United States. The project was a cool opportunity for research, and one that will look great on a resume, Maraccini said.
“I want to go to graduate school and get into research,” he added. “This is a great place to start.”
– Sarah Vickery | 0.884212 | 3.753558 |
The Green Bank Telescope in West Virginia, and the Arecibo Observatory in Puerto Rico have detected six bursts of strong radio signals originating from a constellation 3 billion light years away from Earth. Known as Fast Radio Bursts or FRBs – they only last milliseconds but generate as much energy as the Sun in an entire day – 11 FSBs were captured by high-powered telescopes in March, from similar sources in deep space.
A team of researchers from McGill University wrote in a paper published in The Astrophysical Journal:
“We report on radio and X-ray observations of the only known repeating fast radio burst source, FRB 121102. We have detected six additional radio bursts from this source: five with the Green Bank Telescope at 2 GHz, and one at 1.4 GHz with the Arecibo Observatory, for a total of 17 bursts from this source.
“We find that the intrinsic widths of the 12 FRB 121102 bursts from Arecibo are, on average, significantly longer than the intrinsic widths of the 13 single-component FRBs detected with the Parkes telescope.”
Given the signals’ energy, repeating nature and location, speculation has already begun on whether an advanced alien civilization is trying to contact us. The scientists haven’t ruled out the possibility that the signals originated from extra-terrestrial intelligence, however, they say it is more likely to be solar flares from a young neutron star.
“Our discovery of repeating bursts from FRB 121102 shows that for at least one source, the origin of the bursts cannot be cataclysmic, and further, must be able to repeat on short [less than 1 minute] timescales. Whether FRB 121102 is a unique object in the currently known sample of FRBs, or all FRBs are capable of repeating, its characterization is extremely important to understanding fast extragalactic radio transients.”
In May 2015, RATAN-600 observatory in Russia’s Zelenchukskaya, detected a mysterious burst of radio signal (lasting no more than two seconds) coming from a 6.3 billion-year-old star in a constellation 94.4 light years away from Earth. Astronomers who are engaged in the search for extraterrestrial intelligence (SETI) are now examining the radio signal and its sun-like star, HD 164595, in the hopes of determining its origin using the Allen Telescope Array in California.
“It’s hundreds of times more than all the energy falling on the Earth from sunlight. It goes without saying this would require a power source far beyond anything that exists on Earth.”
Astronomer Douglas Vakoch, president of METI International (which searches for life beyond Earth), told CNN:
“The signal from HD 164595 is intriguing, because it comes from the vicinity of a sun-like star, and if it’s artificial, its strength is great enough that it was clearly made by a civilization with capabilities beyond those of humankind.”
Type I – a civilization that is capable of harnessing the total energy of its own planet including solar, wind, earthquakes, and other fuels;
Type II – an interstellar civilization that is capable of harnessing the total energy output of a star;
Type III – a galactic civilization that is capable of inhabiting and harnessing the energy of an entire galaxy.
At present, our civilization is somewhere near Type I on the Kardashev scale. International Business Times observes:
“If the newly-received FRBs’ source is artificial, they could have been sent by at least a Type-II extraterrestrial civilization as a means to reach out to other, similarly intelligent civilizations. That is because the amount of energy in these FRBs cannot be produced by any conventional means known to man, but could be emitted by an artificial source from a civilization that has harnessed the power of an entire star.”
While scientists are still investigating the radio signals and are far away from concluding whether aliens could be trying to contact Earth, theoretical physicist Stephen Hawking warns humans should not respond to alien signals from outer space because aliens would be far more advanced than us. | 0.878693 | 3.854517 |
October 10, 2015 – New images from NASA’s New Horizons reveal the size and shape of Pluto’s smallest moon, Styx.
Styx – also the faintest of Pluto’s five moons – was discovered using the Hubble Space Telescope in 2012, when New Horizons was more than two-thirds into its voyage to Pluto. The Styx images downlinked on October 5, 2015, were taken by the Long Range Reconnaissance Imager (LORRI) on July 13, approximately 12.5 hours before New Horizons’ closest approach to Pluto.
At that time, the spacecraft was still 391,000 miles (631,000 kilometers) from Styx, making it difficult even for the powerful LORRI camera to see details on such a small moon.
“Although it may not look like much, the new composite image of Styx reveals a highly-elongated satellite, roughly 4.5 miles [7 kilometers] across in its longest dimension and 3 miles [5 kilometers] in its shortest dimension,” said New Horizons Project Scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.
Styx’s measured brightness, combined with this new size estimate, suggest this tiny moon has a highly reflective, icy surface, similar to what was previously found for two of Pluto’s other small moons, Nix and Hydra.
Using these new images, together with the many measurements of Styx’s brightness taken over several months during New Horizons’ approach to Pluto, the science team hopes to unravel more details about this small moon’s shape and rotational properties.
“Ultimately, we hope to learn more about all four of Pluto’s small moons, to understand their similarities and differences, how they formed, and how they evolved,” says New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. | 0.800287 | 3.494642 |
The answer kind of depends on how old you are. At a very introductory level, say, maybe middle school or younger, it's "okay" to refer to Jupiter as a failed star to get the idea across that a gas giant planet is sort of similar to a star in composition. But around middle school and above (where "middle school" refers to around 6-8 grade, or age ~12-14), I think you can get into enough detail in science class where this is fairly inaccurate.
If you ignore that the solar system is dominated by the Sun and just focus on mass, Jupiter is roughly 80x lighter than the lightest star that undergoes fusion. So it would need to have accumulated 80 times what it already has in order to be a "real star." No Solar System formation model indicates this was remotely possible, which is why I personally don't like to think of it as a "failed star."
Below 80 MJ (where MJ is short for "Jupiter masses"), objects are considered to be brown dwarf stars -- the "real" "failed stars." Brown dwarfs do not have enough mass to fuse hydrogen into helium and produce energy that way, but they do still produce their own heat and glow in the infrared because of that. Their heat is generated by gravitational contraction.
And Jupiter also produces heat through both gravitational contraction and differentiation (heavy elements sinking, light elements rising).
Astronomers are not very good at drawing boundaries these days, mostly because when these terms were created, we didn't know of a continuum of objects. There were gas giant planets, like Jupiter and Saturn, and there were brown dwarf stars, and there were full-fledged stars. The line between brown dwarf and gas giant - to my knowledge - has not been drawn. Personally, and I think I remember reading somewhere, the general consensus is that around 10-20 MJ is the boundary between a gas giant planet and brown dwarf, but I think it's fairly arbitrary, much like what's a planet vs. minor planet, Kuiper belt object (KBO) or asteroid.
So during Solar System formation, was there a chance Jupiter could have been a star and it failed ("failed star!") because the mean Sun gobbled up all the mass? Not really, at least not in our solar system. But for getting the very basic concept across of going from a gas giant planet to a star, calling Jupiter a "failed star" can be a useful analogy. | 0.839713 | 3.814734 |
Astronomers used the Venus transit to make measurements of how the Venusian atmosphere absorbs different kinds of light, revealing clues to what elements are layered above Venus’s surface.
Two of NASA’s heliophysics missions can now claim planetary science on their list of scientific findings. A group of scientists used the Venus transit – a very rare event where a planet passes between Earth and the sun, appearing to us as a dark dot steadily making its way across the sun’s bright face – to make measurements of how the Venusian atmosphere absorbs different kinds of light. This, in turn, gives scientists clues to exactly what elements are layered above Venus’s surface. Gathering such information not only teaches us more about this planet so close to our own, but it also paves the way for techniques to better understand planets outside our solar system.
Transits of Venus are so rare that they only happen twice in a lifetime. About every 115 years, Venus will appear to cross over the face of our home star twice, with eight years passing between the pair of transits. This stunning phenomenon is not only incredible to watch, but it provides a unique opportunity for scientific observations of one of our nearest neighboring planets.
NASA’S Solar Dynamics Observatory, or SDO, and the joint Japanese Aerospace Exploration Agency and NASA’s Hinode mission took pictures of the entire event in several wavelengths of light. A team of scientists led by Fabio Reale of the University of Palermo used these pictures to watch the backlit planet as it crossed in front of the sun. By observing the planet’s atmosphere in different wavelengths of light during its journey, they learned more about what kinds of atoms and molecules are actually in its atmosphere. This work was published in Nature Communications on June 23, 2015.
Just as on Earth, each of the layers of Venus’ atmosphere absorb light differently from one another. Some layers may completely absorb a certain wavelength of light, while that same wavelength can pass right through another layer. As Venus passes across the face of the sun — which emits light in almost every wavelength of the electromagnetic spectrum — scientists get a rare chance to see how all different types of light filter through Venus’s atmosphere.
A layer in the upper atmosphere around Venus–called the thermosphere–absorbs certain high-energy wavelengths of light. When looking at the planet against the sun in one of these high-energy wavelengths, the thermosphere will appear opaque, rather than transparent as it does in visible light.
“Radiation goes into the atmosphere and is absorbed, creating ions and a layer of the atmosphere called the ionosphere,” said Dean Pesnell, SDO project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Because the energy in this light is captured by the ions, it is not re-emitted on the other side. In certain wavelengths, Venus’s atmosphere is as solid as a wall, blocking light from traveling to our eyes. To our telescopes, the atmosphere is as dark as the planet itself — so, Venus will appear to have a different size, depending on the wavelength of the telescope’s pictures.
Reale and his team chose images of the Venus transit taken in several X-ray and ultraviolet wavelengths and measured the apparent size of the planet to within several miles. For each set of pictures, the team calculated just how large the atmospheric blocking was–a measure of how high in Venus’ atmosphere that particular wavelength of light is completely absorbed.
Because the various types of atoms absorb light slightly differently, the height of this light absorption lets scientists know how many and what types of molecules make up Venus’s atmosphere. This information is important for planning missions to Venus, as those ions and molecules can change the amount of course-altering drag a spacecraft feels.
“Learning more about the composition of the atmosphere is very important for understanding the braking process for spacecraft when they enter the upper atmosphere of the planet, a process called aerobraking,” said Reale.
The shape of Venus’ atmosphere also gave scientists important clues to how the sun impacts the atmosphere. “If the atmosphere observed were asymmetric, that could tell us more about how the star is impacting the planet,” said Sabrina Savage, NASA project scientist for Hinode.
During the transit, only the sides of the atmosphere could be seen, but they were particularly interesting areas. From the perspective of Venus, these were the areas where day turns into night and night turns into day–on Earth, these transition areas can host interesting effects in the ionosphere. The data from the Venus transit showed that these two transition areas are virtually the same.
“The planet appeared very round in all wavelengths,” said Pesnell. “If the transition from day to night were different from the transition from night to day, you would expect a bulge in the atmosphere on one side of the planet.”
This video shows the entire June 5-6, 2012 Venus transit as captured by the Solar Dynamics Observatory (SDO) in 171 wavelength of extreme ultraviolet light.
Studying the Venus transit can also help improve studies of planets around other stars. Such exoplanets are often discovered by transits just like this, as we can detect the very small amount of light the planets block as they pass across their home star. The more we can observe transiting planets close to home the more it will teach us about how to study distant exoplanets that we can’t currently see in as much detail. When instrument technology advances, we may be able to gather better information about the atmospheres of such exoplanets as well.
“In the future, there might be missions that have enough sensitivity to detect the difference in radius in different wavelengths,” said Reale. “In particular, if there are exoplanets with an extremely thick thermosphere, the size difference in different wavelengths will be larger and there will be a better chance of detecting the change.”
Publication: Fabio Reale, et al., “Using the transit of Venus to probe the upper planetary atmosphere,” Nature Communications 6, Article number: 7563; doi:10.1038/ncomms8563 | 0.88646 | 4.122703 |
Relative motion everywhere performs in our life and the Solar System, and it can be interpreted that a moving object can only have one velocity at any moment when observed by single observer. Humankind has always been fascinated by the night sky, and, in particular, by the movements of the Sun, the Moon, and the objects which the ancient Greeks called plantai ("wanderers"), and which we call planets . Moreover, the planets were vital to Astronomy. Eudoxas (408-355 BC), a Greek mathematician , who was the first to describe a theoretical explanation of the movements of the planets, and proposed model became known as the Geocentric model of the Solar System. Each planet is attached to differing spheres, which revolve around the Earth as its center. From philosophical viewpoints, orbital pattern is circular in this model, and because of it is the most perfect imaginable shape. For an alternative model, Aristarchus (310-230 BC), a Greek astronomer , who was the first to propose the Heliocentric model, that the Earth and other planets orbited the Sun.
Refinements of Geocentric model for capable of accurate predictions, Claudius Ptolemy (85-165 AD), a Alexandrian philosopher, who proposed in his famous book, now known as the Almagest , remained the dominant scientific picture of the Solar System for over a millennium. In significant modifications of Ptolemy, the deferent is a large circle centered on the Earth, and the epicycle is a small circle whose centers move around the circumference of the deferent . Fig. 1 shows the modifications of Ptolemy for Geocentric model of the Solar System. Occasionally, planetary motion sometimes seems in the opposite direction to its apparent direction of rotation around the Earth, and performs the phenomenon of retrograde motion . This confusing behavior became the riddle of the astronomers, embarrassing the Greeks, who believed in order and regularity. Obviously, the trajectory of deferent represents a circle. Nevertheless, based on occasional bouts of the retrograde motion, the trajectory of epicycle has a certain appearance of a petal.
In John's book , he trickily refined the Ptolemaic system. John modified the center of deferent to serve as a kind of spinning crank, which was called a moveable eccentric, and produced an egg-shaped deferent as the Mercury's apparent trajectory in the heavens (see Fig. 2). John proposed that no modern theory exists to explain the miracle of conscious life or the cosmic coincidences that surround our planet. John also revealed the exquisite orbital patterns of the planets and the mathematical relationships that govern them in his book. For instances, with the Sun back in the center, he represent the orbits of Venus and the Earth and draw a line between the two planets positions every couple of days. Because Venus orbits faster the Earth, and so these lines represent the beautiful geometric patterns.
Hipparchus (162-126 BC), a Greek astronomer , who created detailed studies of the motions of the Moon and the Sun, and he found some heavenly bodies necessary to employ three or four circles that moved around each other. Within the illustrations of Fig. 3a, a planet P thus moves in a circle around the mathematical point Q, while Q moves in a circle around the point R, and R moves around the Earth, every point or object moving at its own velocity and appropriate choices of radii for the circles. Relative motion can prove consequently the mechanism for the orbital motions with moving around each other of the heavenly bodies. The number of heavenly bodies moved around with relative motion can be unlimited in theory, and nevertheless the operating mechanism of relative motion can be surely simplified as the illustrations of Fig. 3b. P0 is the initiation of the absolute coordinate system for relative motions. P1 represents the point moving on plane P0 and also the origin of plane P2 . P2 is the termination of coordinate system, and represents the point moving on plane P10 . P1 and P2 simultaneously move at the counterclockwise relative to each its superior coordinate system. | 0.827729 | 3.941347 |
Electric gravity? What gravity actually is is still a mystery to science.
We think we know what gravity does but we do not know why it does it. There are theories about gravity but what gravity really is has not been confirmed.
Gravity is the weakest of the natural forces yet seems to have the biggest effect on space and life itself?
Could gravity be an electromagnetic force and not due to mass?
Normal Gravity (Mass Gravity)
A few quotes explaining what science does and does not know about what it calls gravity.
Question: What is gravity?
Answer: We don't really know. We can define what it is as a field of influence, because we know how it operates in the universe. And some scientists think that it is made up of particles called gravitons which travel at the speed of light. However, if we are to be honest, we do not know what gravity "is" in any fundamental way - we only know how it behaves.
StarChild Question | NASA
The electromagnetic force is one of the four known fundamental forces ... The electromagnetic force is responsible for practically all phenomena one encounters in daily life above the nuclear scale, with the exception of gravity. Roughly speaking, all the forces involved in interactions between atoms can be explained by the electromagnetic force acting between the electrically charged atomic nuclei and electrons of the atoms.
Electromagnetism - Fundamental forces | Wikipedia
What exactly is the strength of gravity? Surprisingly, physicists still can’t agree on the value of the ‘big G’ constant that features both in Isaac Newton’s law of gravitation — which dates back to the year 1687 — and in Albert Einstein’s general theory of relativity. Different experimental techniques have found contradictory values for it. And the entrance of experiments based on quantum physics that exploit the wave-like aspects of matter have only made the discrepancy worse.
It is also possible that the discrepancy points not to a measurement problem but to something completely new. Some physicists have suggested that different techniques give different results because the physics of gravity itself needs to be revised.
Zombie physics: 6 baffling results that just won't die | Nature
There is a problem with Big G (so called to distinguish it from little g, the acceleration due to gravity at Earth's surface). Current measurements of it are, frankly, all over the place. Seven separate experiments in the past decade or so have given results that have a spread of about 0.05%. For a fundamental constant of physics, that is extraordinarily imprecise.
Don't stop the quest to measure Big G | Nature
gravity is the wimpiest of all forces in the universe.
This weakness also makes it the most mysterious, as scientists can't measure it in the laboratory as easily as they can detect its effects on planets and stars. The repulsion between two positively charged protons, for example, is 10^36 times stronger than gravity's pull between them—that's 1 followed by 36 zeros less macho.
... "Gravity is completely different from the other forces described by the standard model," said Mark Jackson, a theoretical physicist at Fermilab in Illinois. "When you do some calculations about small gravitational interactions, you get stupid answers. The math simply doesn't work."
Greatest Mysteries: What Causes Gravity? | Live Science
Gravity is the weakest of the four universal forces which also include nuclear force, weak radiation force, and electromagnetism ... Gravity affects light, time, matter and biology in a variety of ways. However, there are many questions about gravity that remain unanswered ... What exactly causes gravity? It appears to be a wavelike kinetic force, but no one knows for sure.
What is Gravity? Gravity Lesson | NASA
Gravity is the weakest of the four fundamental interactions of nature. The gravitational attraction is approximately 10−38 times the strength of the strong force (i.e. gravity is 38 orders of magnitude weaker), 10−36 times the strength of the electromagnetic force, and 10−29 times the strength of the weak force.
As a consequence, gravity has a negligible influence on the behavior of sub-atomic particles, and plays no role in determining the internal properties of everyday matter (but see quantum gravity).
On the other hand, gravity is the dominant force at the macroscopic scale, that is the cause of the formation, shape, and trajectory (orbit) of astronomical bodies, including those of asteroids, comets, planets, stars, and galaxies.
It is responsible for causing the Earth and the other planets to orbit the Sun; for causing the Moon to orbit the Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; for solar system, galaxy, stellar formation and evolution; and for various other phenomena observed on Earth and throughout the universe.
Gravity | wikipedia
But physicists think about gravity all the time. To them, gravity is one of the mysteries to be solved in order to get a complete understanding of how the Universe works. So, what is gravity and where does it come from? To be honest, we’re not entirely sure.
... Our understanding of gravity breaks down at both the very small and the very big: at the level of atoms and molecules, gravity just stops working. And we can’t describe the insides of black holes and the moment of the Big Bang without the math completely falling apart.
The problem is that our understanding of both particle physics and the geometry of gravity is incomplete.
Where Does Gravity Come From? | Universe Today
The origin of mass in the electrical nature of matter
Without accepting his model in its entirety, I consider Ralph Sansbury’s straightforward electrical theory of magnetism and gravity to have conceptual merit. Simply stated, all subatomic particles, including the electron, are resonant systems of orbiting smaller electric charges of opposite polarity that sum to the charge on that particle. These smaller electric charges he calls ‘subtrons.’ This is the kind of simplification of particle physics required by Ockham’s razor and philosophically agreeable, though it leaves unanswered the real nature and origin of the subtrons. In this model, the electron cannot be treated like a fundamental, point-like particle. It must have structure to have angular momentum and a preferred magnetic orientation, known vaguely as ‘spin.’ There must be orbital motion of subtrons within the electron to generate a magnetic dipole. The transfer of energy between the subtrons in their orbits within the classical electron radius must be resonant and near instantaneous for the electron to be a stable particle. The same argument applies to the proton, the neutron, and, as we shall see —the neutrino.
This model satisfies Einstein’s view that there must be some lower level of structure in matter to cause resonant quantum effects. It is ironic that such a model requires the electric force between the charges to operate incomparably faster than the speed of light in order that the electron remain a coherent particle. It means that Einstein’s special theory of relativity, that prohibits signalling faster than light, must be repealed. A recent experiment verifies this.
Electric Gravity in an Electric Universe | Wal Thornhill on his website holoscience
Ralph Sansbury, the author of these calculations involving sub-electron particles, viewed gravity as involving radially oriented electrostatic dipoles generated by spin and orbiting i.e. by pure centripedal/centrifugal force.
In other words, if you were to put the Earth out into pure intergalactic space and stop all of its motions, it would have no gravity. As to the question of a surface charge attenuating gravity in prehistoric times, it doesn't seem to matter how the dipole effect was generated, the surface charge would neutralize it.
'tholden' post on Thornhill's Latest Gravity Presentation | Thunderbolts forum
Immanuel Velikovsky proposed in his 1946 synopsis a Cosmos Without Gravitation: Attraction, repulsion and electromagnetic circumduction in the solar system. This included a mention of dipole and electromagnet gravity.
MOND [Modified Newtonian Dynamics] was offered as an alternative to cold, dark matter’s inferred gravity field. Since stars on the outskirts of galactic disks revolve at greater-than-apparently-possible velocities, they “must be” experiencing the effects of an unseen and undetectable mass. In short, a volume of dark matter five times the volume of normal matter is supposed to exist in and around many, if not all, galaxies. It is that invisible matter that is said to be exerting itself so strongly.
Both phenomena, the deceleration of space probes in the Solar System, as well as the unexpected stellar velocities in galaxies, can be explained by one thing: electricity flowing through dusty plasma.
As a spacecraft travels through the interplanetary medium it builds up a negative charge differential with respect to the positive charge of the Sun. The Sun’s weak, radial electric field, extending outward for almost a light-day without diminishing, and generated by the movement of charged particles known as the “solar wind,” draws the negatively charged object back toward itself.
The linear attributes of MOND gravity theory are a powerful hint at what might actually be taking place in galaxies as well as star systems. Since electric forces can scale by many orders of magnitude, the weak, radial electric field of the Milky Way galaxy, for example, is most likely doing the same thing to the stars at its outer boundary as the Sun is doing to the charged objects within its sphere of influence.
The Sun is not keeping its family of planets in lockstep by gravity alone, its electric field is also acting in an additional, if not principal manner. It is the electric field of the galaxy that is keeping the stars in orbit around the nucleus, in addition to its far less powerful gravitational field. If electric fields and electrical transmission over star-spanning distances are given their due, MOND, dark matter and all the other ad hoc Big Bang theories would vanish.
As Electric Universe advocate Wal Thornhill wrote: “Common sense suggests that it is unlikely that the laws of physics will need to be rewritten, simply that we should understand better those we have. We need not trouble ourselves with arguments about the nature of gravity in this instance because the mystery can be solved if the electrical nature of the universe is acknowledged. The mystery only arises because astrophysics is taught incorrectly. Students are taught that any separation of charge in space is quickly neutralized as electrons rush to neutralize the charge imbalance. As a result, electricity in space is almost never mentioned, except as a transient effect.”
Charged Gravity | Thunderbolts TPOD
What is gravity?
Gravity is due to radially oriented electrostatic dipoles inside the Earth’s protons, neutrons and electrons. The force between any two aligned electrostatic dipoles varies inversely as the fourth power of the distance between them and the combined force of similarly aligned electrostatic dipoles over a given surface is squared. The result is that the dipole-dipole force, which varies inversely as the fourth power between co-linear dipoles, becomes the familiar inverse square force of gravity for extended bodies. The gravitational and inertial response of matter can be seen to be due to an identical cause. The puzzling extreme weakness of gravity (one thousand trillion trillion trillion trillion times less than the electrostatic force) is a measure of the minute distortion of subatomic particles in a gravitational field.
The 2,000-fold difference in mass of the proton and neutron in the nucleus versus the electron means that gravity will maintain charge polarization by offsetting the nucleus within each atom (as shown). The mass of a body is an electrical variable—just like a proton in a particle accelerator. Therefore, the so-called gravitational constant—‘G’ with the peculiar dimension [L]3/[M][T]2, is a variable! That is why ‘G’ is so difficult to pin down.
Electric Gravity in an Electric Universe | Wallace Thornhill on his website holoscience
A fair scale model of the cosmos can represent one light-year (the distance travelled by light in one year) by one mile, and also represent one Astronomical Unit (distance from the Sun to Earth) by one inch. In the model the orbit of the Earth around the Sun will be represented by a circle with a one-inch radius. An 880,000-mile diameter Sun will scale down to a mark of approximately 1/100 inch across – just a speck. Pluto the outermost planet (or planetesimal) will orbit around this speck at a radius of approximately three and a half feet. But the nearest star on the model – another mere speck – will lie four and a half miles away. This is fairly typical of the closest distances between any of the stars in the galaxy.
How conceivable can it be, therefore, for gravity to be the driving factor of a galaxy? We are thinking, comparatively speaking, of gravitational forces between 1/100th inch specks isolated by over four miles from one another.
It may be, therefore, that the way the solar system runs, with our own as the only example we can know to any great extent, is quite different from the way the galaxy runs as a whole. Even if we are right in judging gravity to have a comparatively dominant influence upon the positions and movements of the planetary bodies of our system, that certainly does not imply we would be right to assume gravitational dominance for interstellar forces in a galaxy, and even less so, for intergalactic forces in the cosmos. Indeed, if the galaxies were powered by vast electrical energy transfers through the plasma environment of space, the puny force of gravitation in such a context could be safely ignored altogether.
Gravity or Electricity – which one Rules the Universe? | Thunderbolts
The Electric Universe cosmology is new and is based on the most general case of the behaviour of electrically charged bodies embedded in a charged plasma. Plasma is a gas in which electrons have been removed from some of the atoms – in other words, it is ionised. Like a metal where the electrons are free to move, plasma is an excellent electrical conductor. 99.999% of matter in the universe is composed of plasma. A charged plasma has a small excess of negative or positive charge. Plasma naturally forms filaments in response to electric and magnetic fields. Those filaments may “pinch” magnetically to form stars. Stars are not isolated but receive electrical power from the galaxy – hence the million degree solar corona. Electromagnetic forces are infinitely more powerful than gravity and capable of simply explaining phenomena attributed to Black Holes. Electromagnetic forces can repel or attract. Gravity only attracts – requiring amazing legerdemain to explain colossal outpourings of matter from centres of galaxies. Plasma cosmology is the practical realm of electrical engineers. It is verifiable by experiment because of the enormous scalability of the phenomena.
GRAVITY vs PLASMA | Wallace Thornhill on Holoscience
The largest dinosaurs are many times the size of an elephant. And dinosaur skeletons aren't as well-designed for bearing weight as elephant skeletons. Dinosaurs are impossibly large for planet Earth, but their bones are proof that they must have existed. How could that be? The limit on size depends on weight, and weight depends on the force of gravity. Most conventional theories assume that gravity throughout the universe has always been and will always be a constant property of matter. But that's only an assumption, and it must be verified empirically.
The Electric Universe offers a different point of view. Gravity is not a constant. It's a variable that depends on the plasma environment. So Earth in the Mesozoic Era may have had less gravity than it has today. Holden calculates that in order for the largest dinosaurs to function, gravity must have been at least 1/3 (and possibly as low as 1/4) what it is today. He also postulates that gravity increased suddenly at the close of the age of dinosaurs but not to the present value. Lower-than-present gravity continued into the following ages of giant mammals and possibly even to the days when early humans were building giant monuments like Stonehenge.
Impossible Dinosaurs | Thunderbolts TPOD
Almost all the matter in space is in the form of plasma. Clouds of gas and dust contain free charged particles — ions, electrons and charged dust (molecules). These charged particles respond strongly to electric and magnetic fields. In cosmic molecular clouds, where stars are formed, just one charged particle in ten thousand neutral particles is sufficient for electric and magnetic forces to overcome gravity.
Twinkle, twinkle electric star | Holoscience
A significant fact, usually overlooked, is that Newton’s law of gravity does not involve time. This raises problems for any conventional application of electromagnetic theory to the gravitational force between two bodies in space, since electromagnetic signals are restricted to the speed of light. Gravity must act instantly for the planets to orbit the Sun in a stable fashion. If the Earth were attracted to where the Sun appears in the sky, it would be orbiting a largely empty space because the Sun moves on in the 8.3 minutes it takes for sunlight to reach the Earth. If gravity operated at the speed of light all planets would experience a torque that would sling them out of the solar system in a few thousand years. Clearly, that doesn’t happen. This supports the view that the electric force operates at a near infinite speed on our cosmic scale, as it must inside the electron. It is a significant simplification of all of the tortuous theorizing that has gone into the nature of gravity and mass. Einstein’s postulates are wrong. Matter has no effect on empty space. Space is three-dimensional—something our senses tell us. There is a universal clock so time travel and variable aging is impossible—something that commonsense has always told us. But most important—the universe is connected and coherent.
‘Instantaneous’ gravity - Electric Gravity in an Electric Universe | Holoscience
Another serious problem faced by conventional thinking is that the quantum shifts seem to occur galaxy-wide without delay. No object has been found with two different redshifts. Yet a change propagating at the speed of light would take something like 100,000 years to traverse a galaxy. It seems that the kind of particle dipole distortions that create inertial mass and gravity propagate at the near infinite speed of the electrostatic force. So, once begun, the quantum shift in atomic orbitals could spread across a galaxy in less than a second. I suppose it could be termed “galactic quantum entanglement.”
The Remarkable Slowness of Light | Holoscience
A simple calculation shows that the sub-particles that form an electron must travel at a speed far in excess of the speed of light – some 2.5 million light-years per second, or from here to the far side of the Andromeda galaxy in one second! So the electrostatic force must act at a speed which is almost infinite on our scale for the electron to be stable.
Electric Universe Theory (EU theory) basics | Holoscience
Electric Gravity links and articles
- Electric Gravity in an Electric Universe | Holoscience
- The Remarkable Slowness of Light | Holoscience
- GRAVITY vs PLASMA | Holoscience
- Gravity or Electricity – which one Rules the Universe? | thunderbolts
- Thornhill's Latest Gravity Presentation and related discussion Clarification Request for Wal Thornhill | Thunderbolts forum
- Electric gravity? Comet 67P | everythingselectric
- Electromagnetic orbits evidence? Small asteroid has mini moon | everythingselectric
- Planets orbits due to electromagnetic forces? | everythingselectric
- The Problem with Gravity: New Mission Would Probe Strange Puzzle | Space
- Electromagnetic gravity related articles on everythingselectric | 0.886646 | 3.414509 |
Crescent ♓ Pisces
Moon phase on 4 January 2014 Saturday is Waxing Crescent, 3 days young Moon is in Aquarius.Share this page: twitter facebook linkedin
Previous main lunar phase is the New Moon before 3 days on 1 January 2014 at 11:14.
Moon rises in the morning and sets in the evening. It is visible toward the southwest in early evening.
Lunar disc appears visually 0.3% wider than solar disc. Moon and Sun apparent angular diameters are ∠1957" and ∠1951".
Next Full Moon is the Wolf Moon of January 2014 after 11 days on 16 January 2014 at 04:52.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 3 days young. Earth's natural satellite is moving from the beginning to the first part of current synodic month. This is lunation 173 of Meeus index or 1126 from Brown series.
Length of current 173 lunation is 29 days, 10 hours and 24 minutes. It is 3 minutes longer than next lunation 174 length.
Length of current synodic month is 2 hours and 20 minutes shorter than the mean length of synodic month, but it is still 3 hours and 49 minutes longer, compared to 21st century shortest.
This New Moon true anomaly is ∠353°. At beginning of next synodic month true anomaly will be ∠8.3°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
2 days after point of perigee on 1 January 2014 at 21:00 in ♑ Capricorn. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 11 days, until it get to the point of next apogee on 16 January 2014 at 01:53 in ♋ Cancer.
Moon is 366 290 km (227 602 mi) away from Earth on this date. Moon moves farther next 11 days until apogee, when Earth-Moon distance will reach 406 537 km (252 610 mi).
7 days after its ascending node on 28 December 2013 at 00:21 in ♏ Scorpio, the Moon is following the northern part of its orbit for the next 4 days, until it will cross the ecliptic from North to South in descending node on 9 January 2014 at 11:26 in ♉ Taurus.
7 days after beginning of current draconic month in ♏ Scorpio, the Moon is moving from the beginning to the first part of it.
4 days after previous South standstill on 31 December 2013 at 04:49 in ♐ Sagittarius, when Moon has reached southern declination of ∠-19.537°. Next 8 days the lunar orbit moves northward to face North declination of ∠19.501° in the next northern standstill on 13 January 2014 at 08:14 in ♊ Gemini.
After 11 days on 16 January 2014 at 04:52 in ♋ Cancer, the Moon will be in Full Moon geocentric opposition with the Sun and this alignment forms next Sun-Earth-Moon syzygy. | 0.83659 | 3.132319 |
A few months ago, physicist Harold White stunned the aeronautics world when he announced that he and his team at NASA had begun work on the development of a faster-than-light warp drive. His proposed design, an ingenious re-imagining of an Alcubierre Drive, may eventually result in an engine that can transport a spacecraft to the nearest star in a matter of weeks — and all without violating Einstein's law of relativity. We contacted White at NASA and asked him to explain how this real life warp drive could actually work.
The above image of a Vulcan command ship features a warp engine similar to an Alcubierre Drive. Image courtesy CBS.
The idea came to White while he was considering a rather remarkable equation formulated by physicist Miguel Alcubierre. In his 1994 paper titled, "The Warp Drive: Hyper-Fast Travel Within General Relativity," Alcubierre suggested a mechanism by which space-time could be "warped" both in front of and behind a spacecraft.
Michio Kaku dubbed Alcubierre's notion a "passport to the universe." It takes advantage of a quirk in the cosmological code that allows for the expansion and contraction of space-time, and could allow for hyper-fast travel between interstellar destinations. Essentially, the empty space behind a starship would be made to expand rapidly, pushing the craft in a forward direction — passengers would perceive it as movement despite the complete lack of acceleration.
White speculates that such a drive could result in "speeds" that could take a spacecraft to Alpha Centauri in a mere two weeks — even though the system is 4.3 light-years away.
In terms of the engine's mechanics, a spheroid object would be placed between two regions of space-time (one expanding and one contracting). A "warp bubble" would then be generated that moves space-time around the object, effectively repositioning it — the end result being faster-than-light travel without the spheroid (or spacecraft) having to move with respect to its local frame of reference.
"Remember, nothing locally exceeds the speed of light, but space can expand and contract at any speed," White told io9. "However, space-time is really stiff, so to create the expansion and contraction effect in a useful manner in order for us to reach interstellar destinations in reasonable time periods would require a lot of energy."
And indeed, early assessments published in the ensuing scientific literature suggested horrific amounts of energy — basically equal to the mass-energy of the planet Jupiter (what is 1.9 × 1027 kilograms or 317 Earth masses). As a result, the idea was brushed aside as being far too impractical. Even though nature allowed for a warp drive, it looked like we would never be able to build one ourselves.
"However," said White, "based on the analysis I did the last 18 months, there may be hope." The key, says White, may be in altering the geometry of the warp drive itself.
In October of last year, White was preparing for a talk he was to give for the kickoff to the 100 Year Starship project in Orlando, Florida. As he was pulling together his overview on space warp, he performed a sensitivity analysis for the field equations, more out of curiosity than anything else.
"My early results suggested I had discovered something that was in the math all along," he recalled. "I suddenly realized that if you made the thickness of the negative vacuum energy ring larger — like shifting from a belt shape to a donut shape — and oscillate the warp bubble, you can greatly reduce the energy required — perhaps making the idea plausible." White had adjusted the shape of Alcubierre's ring which surrounded the spheroid from something that was a flat halo to something that was thicker and curvier.
He presented the results of his Alcubierre Drive rethink a year later at the 100 Year Starship conference in Atlanta where he highlighted his new optimization approaches — a new design that could significantly reduce the amount of exotic matter required. And in fact, White says that the warp drive could be powered by a mass that's even less than that of the Voyager 1 spacecraft.
That's a significant change in calculations to say the least. The reduction in mass from a Jupiter-sized planet to an object that weighs a mere 1,600 pounds has completely reset White's sense of plausibility — and NASA's.
Theoretical plausibility is all fine and well, of course. What White needs now is a real-world proof-of-concept. So he's hit the lab and begun work on actual experiments.
"We're utilizing a modified Michelson-Morley interferometer — that allows us to measure microscopic perturbations in space time," he said. "In our case, we're attempting to make one of the legs of the interferometer appear to be a different length when we energize our test devices." White and his colleagues are trying to simulate the tweaked Alcubierre drive in miniature by using lasers to perturb space-time by one part in 10 million.
Of course, the interferometer isn't something that NASA would bolt onto a spaceship. Rather, it's part of a larger scientific pursuit.
"Our initial test device is implementing a ring of large potential energy — what we observe as blue shifted relative to the lab frame — by utilizing a ring of ceramic capacitors that are charged to tens of thousands of volts," he told us. "We will increase the fidelity of our test devices and continue to enhance the sensitivity of the warp field interferometer — eventually using devices to directly generate negative vacuum energy."
He points out that Casimir cavities, physical forces that arise from a quantized field, may represent a viable approach.
And it's through these experiments, hopes White, that NASA can go from the theoretical to the practical.
Given just how fantastic this all appears, we asked White if he truly thinks a warp-generating spacecraft might someday be constructed.
"Mathematically, the field equations predict that this is possible, but it remains to be seen if we could ever reduce this to practice."
What White is waiting for is existence of proof — what he's calling a "Chicago Pile" moment — a reference to a great practical example.
"In late 1942, humanity activated the first nuclear reactor in Chicago generating a whopping half Watt — not enough to power a light bulb," he said. "However, just under one year later, we activated a ~4MW reactor which is enough to power a small town. Existence proof is important."
His cautious approach notwithstanding, White did admit that a real-world warp drive could create some fascinating possibilities for space travel — and would certainly reset our sense of the vastness of the cosmos.
"This loophole in general relativity would allow us to go places really fast as measured by both Earth observers, and observers on the ship — trips measured in weeks or months as opposed to decades and centuries," he said.
But for now, pursuit of this idea is very much in science mode. "I'm not ready to discuss much beyond the math and very controlled modest approaches in the lab," he said.
Which makes complete sense to us, as well. But thanks to these preliminary efforts, White has already done much to instill a renewed sense of hope and excitement over the possibilities. Faster-than-light travel may await us yet. | 0.855564 | 3.84406 |
Alan Friedman, a greeting card printer by day, is an avid astrophotographer by night. With a pretty simple setup, he's produced images that rival Hubble shots in terms of beauty.
Friedman starts with a standard telescope and a diagonal—an attachment that, with the use of a prism to reflect light at a specific angle, allows viewers to look perpendicular to the telescope, giving them views they'd otherwise have to crouch below the telescope to see. He then uses a high-speed, high-resolution webcam and a hydrogen alpha filter. The camera allows him to scan many frames and select the crispest one as his final photograph, and the filter allows him to look at the sun safely, as well as take better images of it. The filter has many layers of material that interfere with various wavelengths of light, leaving an image that only includes certain levels of light emitted by burning hydrogen. This wavelength is both safe for the human eye and perfect for taking detailed photos of the sun—a far cry from the white blob an unfiltered camera would record.
Hobbies such as astrophotography are pretty addicting, and Friedman has progressed to much more elaborate equipment. But you can get started right now with a homemade telescope, a good filter, and a webcam.
Scientists have been staring at the sun for centuries. Before the advent of advanced imaging techniques that let people look at the sun without hurting their eyes, people such as Galileo observed sunspots and other solar phenomena by gazing at the sun when it was on the horizon or covered by clouds. Today space telescopes not only keep a constant watch on the sun, but do so without having to account for any atmospheric interference.
The Solar Dynamics Observatory, launched in February 2011 and currently in orbit at 22,000 miles above Earth, is NASA's main heliocentric project. SDO contains three instruments, which together take photographs of the sun every 10 seconds. With 10 times the resolution of an HD television, the probe takes every shot in eight wavelengths of light. Other solar observation satellites, such as the Solar Terrestrial Relations Observatory and the Solar and Heliospheric Observatory, also take pictures of the sun in eight wavelengths simultaneously.
The sun emits light in all visible colors, but since our eyes combine them all for processing, we see the sun as being white or yellow. Since each wavelength of light represents a different temperature of burning gas, focusing on one instead of another can allow researchers to capture images of different layers of the sun. That's how they know what's going on inside. Focusing on yellow-green light shows the surface of the sun, which is about 10,000 degrees Fahrenheit, but looking at extreme ultraviolet light reveals atoms at around 11 million F—a temperature many solar flares reach, allowing NASA researchers to see and document them.
There's one occasion that turns even the most casual of astronomers into a regular Icarus: the solar eclipse.
On a normal day the sun's rays are so bright that evolutionary failsafes kick in if we try to stare too long. Blinking, eye watering, and pupil dilation keep your sensitive peepers safe. But during an eclipse, just enough visible light is blocked to trick your reflexes, and you're able to keep your eyes open. The harmful UV rays are still present, though, so you'll still get the sunburned corneas. And without the pain and blinking that unblocked sunlight produce, you're more likely to stare long enough to sustain permanent retina damage. That's why we're all warned not to look directly at a solar eclipse.
The easy fix is a pair of specially made sunglasses (most standard glasses won't block enough UV rays to be of any help) branded either for eclipses or welding, which work by blocking enough of the strongest wavelengths of light to save your eyeballs. You can also make a pinhole projector, which projects a shadow of the eclipse onto a piece of cardboard or the ground. It produces a reversed image when light passes through a hole and hits a flat surface. Pinhole projectors are useful for any sun-blocking phenomenon, such as last year's transit of Venus. On a normal day a pinhole projector will just show you a round sun, but if anything is passing in front of it, you'll get a great view–without roasting your eyes. | 0.837849 | 3.732918 |
Ceres' Geological Activity, Ice Revealed in New Research
A lonely 3-mile-high (5-kilometer-high) mountain on Ceres is likely volcanic in origin, and the dwarf planet may have a weak, temporary atmosphere. These are just two of many new insights about Ceres from NASA’s Dawn mission published this week in six papers in the journal Science.
“Dawn has revealed that Ceres is a diverse world that clearly had geological activity in its recent past,” said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
A Temporary Atmosphere
A surprising finding emerged in the paper led by Russell: Dawn may have detected a weak, temporary atmosphere. Dawn’s gamma ray and neutron (GRaND) detector observed evidence that Ceres had accelerated electrons from the solar wind to very high energies over a period of about six days. In theory, the interaction between the solar wind’s energetic particles and atmospheric molecules could explain the GRaND observations.
A temporary atmosphere would be consistent with the water vapor the Herschel Space Observatory detected at Ceres in 2012-2013. The electrons that GRaND detected could have been produced by the solar wind hitting the water molecules that Herschel observed, but scientists are also looking into alternative explanations.
“We’re very excited to follow up on this and the other discoveries about this fascinating world,” Russell said.
Ahuna Mons as a Cryovolcano
Ahuna Mons is a volcanic dome unlike any seen elsewhere in the solar system, according to a new analysis led by Ottaviano Ruesch of NASA’s Goddard Space Flight Center, Greenbelt, Maryland, and the Universities Space Research Association. Ruesch and colleagues studied formation models of volcanic domes, 3-D terrain maps and images from Dawn, as well as analogous geological features elsewhere in our solar system. This led to the conclusion that the lonely mountain is likely volcanic in nature. Specifically, it would be a cryovolcano — a volcano that erupts a liquid made of volatiles such as water, instead of silicates. “This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past,” Ruesch said.
Ceres: Between a Rocky and Icy Place
While Ahuna Mons may have erupted liquid water in the past, Dawn has detected water in the present, as described in a study led by Jean-Philippe Combe of the Bear Fight Institute, Winthrop, Washington. Combe and colleagues used Dawn’s visible and
infrared mapping spectrometer (VIR) to detect probable water ice at Oxo Crater, a small, bright, sloped depression at mid-latitudes on Ceres.
Exposed water-ice is rare on Ceres, but the low density of Ceres, the impact-generated flows and the very existence of Ahuna Mons suggest that Ceres’ crust does contain a significant component of water-ice. This is consistent with a study of Ceres’ diverse geological features led by Harald Hiesinger of the Westfälische Wilhelms-Universität, Münster, Germany. The diversity of geological features on Ceres is further explored in a study led by Debra Buczkowski of the Johns Hopkins Applied Physics Laboratory, Laurel, Maryland.
Impact craters are clearly the most abundant geological feature on Ceres, and their different shapes help tell the intricate story of Ceres’ past. Craters that are roughly polygonal — that is, shapes bounded by straight lines — hint that Ceres’ crust is heavily fractured. In addition, several Cerean craters have patterns of visible fractures on their floors.
Some, like tiny Oxo, have terraces, while others, such as the large Urvara Crater (106 miles, 170 kilometers wide), have central peaks. There are craters with flow-like features, and craters that imprint on other craters, as well as chains of small craters. Bright areas are peppered across Ceres, with the most reflective ones in Occator Crater. Some crater shapes could indicate water-ice in the subsurface.
The dwarf planet’s various crater forms are consistent with an outer shell for Ceres that is not purely ice or rock, but rather a mixture of both — a conclusion reflected in other analyses. Scientists also calculated the ratio of various craters’ depths to diameters, and found that some amount of crater relaxation must have occurred. Additionally, there are more craters in the northern hemisphere of Ceres than the south, where the large Urvara and Yalode craters are the dominant features.
“The uneven distribution of craters indicates that the crust is not uniform, and that Ceres has gone through a complex geological evolution,” Hiesinger said.
Distribution of Surface Materials
What are the rocky materials in Ceres’ crust? A study led by Eleonora Ammannito of the University of California, Los Angeles, finds that clay-forming minerals called phyllosilicates are all over Ceres. These phyllosilicates are rich in magnesium and also have some ammonium embedded in their crystalline structure. Their distribution throughout the dwarf planet’s crust indicates Ceres’ surface material has been altered by a global process involving water.
Although Ceres’ phyllosilicates are uniform in their composition, there are marked differences in how abundant these materials are on the surface. For example, phyllosilicates are especially prevalent in the region around the smooth, “pancake”-like crater Kerwan (174 miles, 280 kilometers in diameter), and less so at Yalode Crater (162 miles, 260 kilometers in diameter), which has areas of both smooth and rugged terrain around it. Since Kerwan and Yalode are similar in size, this may mean that the composition of the material into which they impacted may be different. Craters Dantu and Haulani both formed recently in geologic time, but also seem to differ in composition.
“In comparing craters such as Dantu and Haulani, we find that their different material mixtures could extend beneath the surface for miles, or even tens of miles in the case of the larger Dantu,” Ammannito said.
Now in its extended mission, the Dawn spacecraft has delivered a wealth of images and other data from its current perch at 240 miles (385 kilometers) above Ceres’ surface, which is closer to the dwarf planet than the International Space Station is to Earth. The spacecraft will be increasing its altitude at Ceres on Sept. 2, as scientists consider questions that can be examined from higher up. | 0.812427 | 3.777919 |
OSIRIS-REx bound for 4.5 billion mile journey for some priceless pebbles
CAPE CANAVERAL, Fla. — Tomorrow evening, Thursday, September 8, 2016, NASA’s latest foray into space, a mission named OSIRIS-REx, is scheduled to launch from Launch Complex 41 at Cape Canaveral Air Force Station adjacent to Kennedy Space Center in Florida. While the objective of the mission might appear tiny, what the “might” possibly be is profound.
Its payload, which contains instruments, a sample acquisition mechanism, and a return capsule, will begin a 7-year journey to the Asteroid 101955 Bennu and back. Its goal is to study the remnant of our solar system’s early formation in detail and collect a sample of the asteroid’s surface material for return to Earth and intensive study.
The timeline for this mission is an example of just how long space exploration efforts take, from start to finish. Planning for OSIRIS-REx began 5 years ago, led by a team of scientists and engineers from the University of Arizona, and including scores of others from NASA, United Launch Alliance, and Lockheed Martin.
The spacecraft will take two years to chase down the asteroid, a year to map and explore the asteroid’s surface, and another 2 years to return, not to mention the years of subsequent analysis of the returned samples.
According to NASA, asteroids are metallic, rocky bodies without atmospheres that orbit the Sun but are too small to be classified as planets. Known as “minor planets”, tens of thousands of asteroids congregate in the so-called main asteroid belt: a vast, doughnut-shaped ring located between the orbits of Mars and Jupiter. Asteroids are thought to be primordial material prevented by Jupiter’s strong gravity from accreting into a planet-sized body when the Solar System was born some 4.6 billion years ago.
Known asteroids range in size from the largest – Ceres, the first discovered asteroid in 1801 – at about 600 miles (966 km) in diameter down to the size of pebbles. Sixteen asteroids have diameters of 150 miles (241 km) or greater. The majority of main belt asteroids follow slightly elliptical, stable orbits, revolving in the same direction as the Earth and taking from three to six years to complete a full circuit of the Sun.
The OSIRIS-REx mission is slated to visit Bennu, a mid-sized asteroid about 1,640 feet (500 meters) in average diameter (about the height of World Trade Center destroyed in 2011). It travels at about 63,000 mph (102,998 km/h) – Earth travels at about 67,000 mph (107,826 km/h) – around the Sun every 1.2 years.
Bennu is considered a primitive asteroid that has not significantly changed in 4.5 billion years; it is carbon-rich and is thought to have a composition similar to that of Earth. In 2035, Bennu is predicted to come as close to our home world as 186,000 miles (257,495 km) – the Moon orbits Earth at a mean distance of 238,854 miles (384,399 km). At present, Bennu is about 340 million miles from our planet (3-and-a-half times the distance from the Earth to the Sun).
During a Sept. 6, 2016, press conference, Dante Lauretta, OSIRIS-REx’s principal investigator from the University of Arizona (Tucson) explained that Bennu was chosen for the target of this mission based on criteria including distance from Earth, its orbit isn’t too close to the Sun, has an orbital inclination of less than 10 degrees compared to our planet, and the possibility of having loose material on the surface. Five reasonably sized asteroids met those criteria, from which Bennu was chosen.
The OSIRIS-REx spacecraft that is being prepped to fly to Bennu weighs a bit over 2 tons (1,814 kg) and is roughly the size of a FedEx truck. It will be powered by two solar panels that will deploy after launch. The spacecraft’s payload includes a camera suite, three spectrometers, a laser altimeter, a sampling arm, and a sample return capsule. Lockheed Martin built the spacecraft with instruments produced by the University of Arizona, the Canadian Space Agency (OLA), Arizona State University, NASA’s Goddard Space Flight Center, and the Massachusetts Institute of Technology.
Lauretta describes the process in a NASA video: Engineers will activate thrusters with which to navigate the spacecraft very slowly toward the asteroid, and in about mid-2020, will slowly descend the spacecraft to the surface of the asteroid. Given that the probe will be traveling approximately 30 times faster that the fastest high-velocity rifle bullet – this is tricky indeed.
A robotic arm with a sampler head will then be deployed, allowing the disc-shaped sampler head (about 18” in diameter) to briefly contact the asteroid surface for 5 seconds or so. During that contact, compressed nitrogen gas will stir up the surface material (anticipated about 1 cm in diameter) that will be captured in a basket-like chamber.
Once engineers confirm that material has been collected, they will orient the spacecraft for its 2-year return to Earth. It will then conduct a fiery re-entry through the Earth’s atmosphere, with a parachute-assisted landing in the Southwest of the United States.
Only about 25 percent of the sample will be made available for immediate analysis. The remaining 75 percent will be preserved for future analysis by succeeding generations of scientists with more sophisticated technology.
Worried that Bennu or some other asteroid might someday smash into the Earth? NASA is keeping a close watch. Explains Lauretta on his website, “The tabulation of potential Earth impacts results in a cumulative impact probability of approximately 1 in 2700 sometime in the 2175–2196 time frame. The effect of a Bennu impact on Earth would be insignificant on a planetary scale. The Earth is not strongly disturbed by such an impact and loses negligible mass. The impact does not make a noticeable change in the tilt of Earth’s axis and it does not shift the Earth’s orbit noticeably. Local effects, however, would be much more noticeable.”
For Lauretta and the other team members working on this mission, tomorrow’s planned launch will not mark the culmination of five years of work, but rather the beginning of an odyssey of another seven years, awaiting the return of their precious treasure in 2023.
Jim Siegel comes from a business and engineering background, as well as a journalistic one. He has a degree in Mechanical Engineering from Purdue University, an MBA from the University of Michigan, and executive certificates from Northwestern University and Duke University. Jim got interested in journalism in 2002. As a resident of Celebration, FL, Disney’s planned community outside Orlando, he has written and performed photography extensively for the Celebration Independent and the Celebration News. He has also written for the Detroit News, the Indianapolis Star, and the Northwest Indiana Times (where he started his newspaper career at age 11 as a paperboy). Jim is well known around Celebration for his photography, and he recently published a book of his favorite Celebration scenes. Jim has covered the Kennedy Space Center since 2006. His experience has brought a unique perspective to his coverage of first, the space shuttle Program, and now the post-shuttle era, as US space exploration accelerates its dependence on commercial companies. He specializes in converting the often highly technical aspects of the space program into contexts that can be understood and appreciated by average Americans. | 0.84173 | 3.593403 |
Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a `circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.
- Pub Date:
- January 2012
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- Accepted and published in Nature (2012 Jan 26). This is the submitted version of paper, merged with the Supplementary Information | 0.880993 | 3.794161 |
Welp, that’s clinched it. It seems like it really is the end of the road for 2I/Borisov, a comet that travelled light-years across space before winding up in the Solar System. New data show that the comet is coming apart.
The most recent Hubble observations of the comet suggest that the comet has broken into at least two pieces, according to a notice posted to Astronomer’s Telegram.
“Images from UT 2020 March 23 show a single inner brightness core, like that observed in all previous HST images of 2I/Borisov,” wrote a team of astronomers led by David Jewitt of the University of California Los Angeles.
“In contrast, images from UT 2020 March 30 show a clearly non-stellar core, consistent with two unresolved components separated by 0.1 arcsecond (180 km at the distance of the comet) and aligned with the main axis of the larger dust coma.”
This is not at all an unexpected turn of events. Astronomers have been avidly watching the comet following its closest approach to the Sun, or perihelion, on 8 December 2019.
It’s pretty normal for comets to break up as they reach and pass perihelion. What we think happens has to do with outgassing, due to the sublimation of cometary ices as they are heated by the Sun. This is thought to spin up the comet’s nucleus, causing it to fragment under centripetal instability.
Not all comets come apart like this, so astronomers were watching and waiting to see whether 2I/Borisov – a comet discovered in August last year, with a trajectory indicating that it came from outside the Solar System – would continue on its way, or come to the end its long journey right here.
And sure enough, last month, it seemed the latter was the case. A team of Polish astronomers led by Michal Drahus and Piotr Guzik of Jagiellonian University noticed that, in early March, the comet brightened significantly, twice in a few days. This behaviour, they said, was “strongly indicative of an ongoing nucleus fragmentation.”
According to these new observations, as of at least March 28, the comet is now in bits.
“The double appearance, indicating the ejection of a nucleus fragment, is confirmed in HST data from UT 2020 March 28,” Jewitt’s team wrote.
This process may seem like sad news for 2I/Borisov, but it’s an amazing opportunity for astronomers. As the comet fragments further, we can take images of its spectrum to figure out what it’s made of, and how similar or different it is from Solar System comets.
So far, observations have found that the comet’s colour and composition are, in fact, very similar to comets from the outer limits of the Solar System. This is exciting because it’s thought that Solar System comets could have carried a bunch of the ingredients for life to Earth. If 2I/Borisov is similar to those comets, it hints that comets could have carried such ingredients to other worlds, too.
Astronomers are definitely going to be keeping an eye on 2I/Borisov, and more Hubble observations have been planned to make sure we catch as much of its ongoing fragmentation as possible. | 0.857615 | 3.721111 |
By The Metric Maven
Recently I read the book Gravitational Waves by Brian Clegg in conjunction with attending a talk on the subject. Both were quite interesting and had their method of numerical presentation in common. During the presentation it was revealed that the distance of the source of the first gravitational wave detected was 1.8 Billion light years. “Is this a lot?”—as my friend Dr. Sunshine likes to ask when putting numbers in context. I immediately wanted to know the distance with a metric prefix. If it is in Exameters, then it would be inside of our galaxy. Our galaxy is about 1000 Exameters or a Zettameter. I did not stop to estimate the values as I wanted to listen to the presentation.
First we have an Olde English prefix with a ersatz “unit” called the light year. 1.8 billion of them is 1.8 Giga units, and the light year unit is 9.4607 Petameters. We end up with 1.8 * 9.4 x 109 * 1015 = 16.92 x 1024 or about 17 Yottameters. Wow! the observable universe is about 880 Yottameters, can this possibly be right? It seems very large, just based on the metric prefix. I go to Wikipedia to see if I can verify this number. They currently quote it as 1.4 +/- 0.6 billion light years. It’s a bit less, but same magnitude. They also state it is 440 Megaparsecs. A parsec is about 31 Petameters, so we have 440*31 x 106 * 1015 or 13.64 Yottameters! I’m immediately able to grasp the size of this number in metric, and it seems astonishing.
Assuming I haven’t made a mistake, what are the detection distances in ascending order of the gravitational wave observations to date?
GW170817 2017-08-17 1.24 Ym
GW170608 2017-06-08 10.54 Ym
GW150914 2015-09-14 13.64 Ym
GW151226 2015-12-26 13.64 Ym
GW170814 2017-08-14 16.74 Ym
GW170104 2017-01-04 27.28 Ym
This is a rather amazing list to me. They are all further out than I would have expected gravitational waves to be detected. There is an unconfirmed observation that occurred at 31 Ym. This gives me some idea of the approximate detection limit for the current version of LIGO. This list gives you metric units that allow you to compare the distances to the size of the observable universe. As our Milky Way Galaxy is about 1 Zettameter across, we could write the list in a way that allows us to use our galaxy as a measurement touchstone:
GW170817 2017-08-17 1 240 Zm
GW170608 2017-06-08 10 540 Zm
GW150914 2015-09-14 13 640 Zm
GW151226 2015-12-26 13 640 Zm
GW170814 2017-08-14 16 740 Zm
GW170104 2017-01-04 27 280 Zm
That is a lot of galactic lengths from us. According to Brian Clegg, it is expected that around 2020 a LIGO upgrade has the potential to increase the detection distance by about a factor of three. If my estimate is right, this will be about 75 Yottameters. The detection volume will increase by 30 %. A set of enhancements scheduled for implementation from now to 2026 (LIGO A+) are expected to double the sensitivity distance again. So if my estimate is good, it would be out to 150 Yottameters! With this sensitivity, several black hole mergers per hour are expected to be detected.
There are discussions of a 40 Kilometer long LIGO receiver in space called the Cosmic Explorer. This is expected to increase the volume of sensitivity to black hole merger detection to cover the entire 880 Yottameter extent of the visible Universe. That would be amazing.
Why stop there? Brian Clegg discusses a concept known as LISA (Laser Interferometer Space Antenna). The arms of the interferometer would be formed between three satellites in a triangular configuration with 2.5 Gigameter sides! LISA would orbit the Sun following along Earth’s orbit at a distance of about 50 to 65 Gigameters! Wow that seems just really big. Below is an animated GIF of the LISA satellite array orbit.
LISA Motion — Wikimedia Commons
In Brian Clegg’s words:
Unlike a ground-based observatory such as LIGO, LISA would have the chance to take in the whole of the sky. Rather than orbit the Earth as most satellites do, LISA is planned to be in an orbit around the Sun, following the Earth’s path at a distance of between 50 and 65 million kilometres, about a quarter again the distance at which the Moon orbits. (pg 142)
Did I compute this distance wrong? 65 * 106 * 103 meters = 65 Gigameters. The distance from the Earth to Venus is about 42 Gm unless I’m mistaken. The length of the arc the Earth travels around the Sun is about 940 Gm. This is about one-fifteenth the distance arc length of the orbit. The animated gif above seems consistent with this value.
The distance from the Earth to the Moon is 384 402 Km or 384 Megameters. 1.25 multiplied by this number is 480 Megameters. The number is not even in the right metric prefix “area code.” The Olde English prefixes when used with metric are a pigfish disaster. They provide no real magnitude distinction when concatenated with metric prefixes. I’m still concerned I’ve made a conversion error or misinterpreted Glegg’s prose. He seems to be conflating a distance in Gigameters with one in Megameters. Perhaps the Megameter distance is the closest approach of each satellite.
Clegg discusses the history of LISA on Page 142-143:
LISA was originally a joint venture between the European Space Agency (ESA) and NASA, but in 2011, suffering severe funding restrictions, NASA pulled out. Initially, ESA looked likely to go for a scaled-down version, known as the New Gravitational Wave Observatory, but with a renewed interest in gravitational waves after the LIGO discoveries, in early 2017 a revamped version of LISA, now featuring 2.5-million-kilometre beams, was proposed at the time, was proposed and at the time of writing has just been accepted for funding. This followed the test launch in 2015 of the LISA Pathfinder, as single satellite with tiny 38-centimetre (15 inch) interferometer arms……
He uses the pseudo-inch known as the centimeter with conversion to barleycorn inches next to it to express the tiny arm length. Would writing 380 mm arms killed him?
I don’t want my readers to get the wrong impression. I like Brian Clegg’s book. It is well worth reading if you are interested in gravitational waves. (I recommended it to the audience at the talk I attended) Its pigfish metric usage is common in science writing. He is doing what essentially all other contemporary science writers do. Astronomers only offer the same manner of visceral push-back at using metric units that citizens of the US exhibit. For those of you who might be interested in metric astronomy, I recommend my essay Long Distance Voyager.
On page 58-59 Clegg explains the density of a neutron star thus:
But a neutron star consists only of neutrons. With no electrical charge to repel each other, these particles can be pulled closer and closer by gravity until the exclusion principle kicks in when they’re practically on top of one another, enabling that great mass to be squeezed into a ridiculously small space. The result is that a teaspoonful of neutron star material would weigh about 100 million tonnes.
Once again an Olde English prefix (million) and a retro Olde English “metric” value tonne serve to obscure as much as impress. When the Olde English prefix is converted to metric and the tonne converted to metric we have a MegaMegagram or Teragram! Wow 100 Teragrams! The total mass of humanity is about 423 Teragrams, so about 65 mL of neutron star would contain the mass of all the humans on Earth. If you cup both of your hands together side-by-side, they would easily contain all of humanity at this density.
The future of gravitational wave astronomy is bright, it would be brighter if it was expressed exclusively with the metric system.
If you liked this essay and wish to support the work of The Metric Maven, please visit his Patreon Page.
Currently I have disabled comments as Akismet determined I’m a for profit and therefore need to pay them more than the amount contributed per month to me by my patrons. I would rather use it to pay the site fees each year. I received over 6000 spam comments from bots and currently have to clear them one-by-one. Until I find another option, I will have to suspend comments going forward. | 0.91742 | 3.428738 |
Last year, Stephen Hawking and Russian billionaire Yuri Milner hatched an ambitious plan to send a tiny probe to the Alpha Centauri star system. Travelling at 20 per cent the speed of light, the researchers weren’t entirely sure how the probe was supposed to stop once it arrived at its destination, or whether it would even be able to. Excitingly, a pair of European scientists now say they have solved the problem.
In a new paper published in The Astrophysical Journal Letters, physicist René Heller from the Max Planck Institute, along with computer scientist Michael Hippke, has shown that the radiation and gravity from Alpha Centauri’s stars can be used to decelerate an incoming probe. So instead of whizzing by in a flash, the lightsail-driven nanocraft will hit the brakes, slowing down enough to explore the system’s trio of stars — and even the Earth-like planet Proxima b.
As part of the Breakthrough Starshot Initiative, Milner plans to invest $US100 million ($132 million) in an effort to develop an ultra-light autonomous lightsail that can be accelerated to one-fifth the speed of light (60,000km/s). At this ludicrous speed, a sail-driven robotic probe could reach Alpha Centauri — the closest star system to Earth — in just 20 years, as opposed to 100,000 years using traditional chemical thrusters.
Under the original proposal, a tiny probe would be mounted to a small, metre-sized light sail, and driven away from Earth by a phased array of lasers. The energy produced by the lasers could theoretically accelerate an object thousands of times faster than the fastest spacecraft today.
But this isn’t the only scheme being considered. Under Heller and Hippke’s plan, a much larger “photon” sail would replace the laser array. The probe itself would measure a several centimetres across and weigh just a few grams (sorry, no passengers on this trip!). To propel it through interstellar space, the device would be attached to large, square-shaped sails. In addition to being big, the sails would need to be exceptionally light, and thus very thin. Radiation emanating away from the Sun would push the probe in the direction of Alpha Centauri. Once enough gravitational inertia is acquired, the probe would retract its sails for the long journey ahead.
Under this scheme, it would take the probe about 95 years travelling at 4.6 per cent the speed of light to reach Alpha Centauri. It’s nearly five-times longer than Milner’s original timeframe — but excitingly, the probe could theoretically be made to stop.
“Interstellar travel to the Alpha Centauri system will supposedly happen with speeds that are a significant fraction of the speed of light in order to keep travel times well below 1000 or, better, even below 100 years,” Heller told Gizmodo. “At that speed, however, an incoming lightsail would need extremely high amounts of energy to slow down [and enter] bound orbits.” Adding fuel for deceleration, he says, would only make matters worse. “If the ship has the required fuel on board, then it would be very heavy — increasing its needs for even more fuel.”
Given this limitation, and without a solution, it was assumed that the probes would zoom past the Alpha Centauri system similarly to how the New Horizons flew past Pluto. But at near relativistic speeds, the probe would likely experience great difficulty taking accurate and meaningful measurements of the star system itself. Thankfully, however, there may be a solution — one that would not just slow down the nanocraft to more manageable speeds, but allow mission scientists to explore the Alpha Centauri system in great detail.
“We found a method to slow down incoming light sails using the energy output of the target star instead,” said Heller. “We use the energy of the stellar light particles to slow down the sail. Hence, the incoming light sail would need no onboard fuel, which nicely fits the scenario of an interstellar, extremely-light sail proposed by the Breakthrough Starshot Initiative.”
Above: An animation showing the “photogravitational assist” at Alpha Centauri A.
For this plan to work, the probe would redeploy its sail on arrival, leveraging the incoming radiation from the stars in the Alpha Centauri system. Using a computer simulation, Heller and Hippke based their calculations on a 100g space probe attached to a 100,000-square-metre sail, which is about the size of 14 soccer fields. As the probe gets increasingly close to the star system, the braking force increases.
On arrival, instead of using solar photons as a propulsion force, the sail “catches” the outgoing solar radiation from Alpha Centauri, gradually slowing the vehicle down. Ironically, the same physics that will push the probe away from our solar system will be used to slow it down at its destination.
During the deceleration manoeuvre, the tiny probe will need to approach the star Alpha Centauri A to within five stellar radii (that is, a distance equal to five times the width of the star), or about four million km, in order to be captured into orbit. By this point, the nanocraft will have slowed down to about 2.5 per cent the speed of light. Failure to slow the craft down from its maximum cruising speed (4.6 per cent the speed of light) would fling the probe away and back into interstellar space.
Every successful journey starts with a map. This one shows the manoeuvring of the autonomous “nanocraft” as it decelerates at Alpha Centauri A, makes a quick four-day journey to Alpha Centauri B, and finally proceeding on a 46-year trip to Proxima Centauri — home of an Earth-like planet.
Once at Alpha Centauri A, the star’s gravity can be used to manoeuvre the probe, similar to the “slingshot” manoeuvres used to direct probes like Voyagers 1 and 2 around the solar system. Theoretically, the autonomous probe could settle into an orbit around Alpha Centauri A and explore its planets. Excitingly, Heller and Hippke have also outlined a plan for sending the probe to the system’s other stars, namely Alpha Centauri B (the binary companion to Alpha Centauri A) and Proxima Centauri (a distant third star located about 0.22 light-years (two trillion km) from A and B’s common centre of mass). Under this plan, it would take the probe about a century to reach Alpha Centauri A, a few days to reach Alpha Centauri B and then another 46 years to reach Proxima Centauri.
But the added years would be worth it. In one of the most remarkable discoveries of 2016, astronomers learned that Proxima Centauri hosts an Earth-like planet. It’s one of the most tantalising objects of inquiry within striking distance — and we finally have a plan for observing it up close. Data collected by the probe would take a little over four years to reach mission scientists on Earth (given the extreme distances involved, we’re going to have be patient with such things, and get accustomed to such long term planning/thinking). A system for sending the data back still needs to be developed.
A battery of technical hurdles still need to be sorted out before such a mission is launched, but the researchers are optimistic. For example, some of the super-light materials required for the mission have already been produced in the lab. “We might need one or two decades to be able to build such interstellar light sails,” Heller told Gizmodo. He adds that the sail’s surface would need to be very reflective from the red to the blue part of the visible spectrum, and possibly even beyond that. “This technology is not yet available but, again, huge progress has been made in laboratories over the past few years and scientists have found… materials that can reflect up to 99.99% the amount of light that they receive.”
Next, Heller and Hippke plan to present their study in detail to the Breakthrough Starshot Initiative at its upcoming Breakthrough Discuss meeting in Palo Alto in April.
“We are very interested in their feedback, because these people are the world’s leading experts in this emerging field of interstellar light sail research,” he said. “Then, Michael [Hippke] and I are working out ideas for an interstellar travel catalogue to our most nearby stars, but this is work in progress and mostly confidential between Michael and me so far.”
Ooooh, such a tease. As always, Gizmodo will be on the lookout for when this research is made public. Until then, let’s celebrate the fact that we’re a step closer to embarking on humanity’s first interstellar space mission. | 0.861922 | 3.865166 |
NASA's Hubble Space Telescope has snapped a spectacular new image of an iconic nebula to celebrate its 23 years of peering deep into the heavens.
The Hubble observatory, which launched on April 24, 1990, captured the Horsehead Nebula in infrared light, peering through obscuring veils of dust to reveal the object's hidden features.
"The result is a rather ethereal and fragile-looking structure, made of delicate folds of gas — very different to the nebula’s appearance in visible light," mission officials wrote in an image description today (April 19). The new observations allowed astronomers to create a dazzling video of the Horsehead Nebula based on Hubble's photos.
The Horsehead Nebula, also known as Barnard 33, is located about 1,500 light-years from Earth in the constellation Orion (The Hunter). The Horsehead is a huge interstellar cloud of gas and dust, like other nebulae, and the light from a nearby star gives it a beautiful glow.
The object is a popular observing target, and Hubble has taken numerous Horsehead photos over the years — including in 2001, to celebrate the telescope's 11-year anniversary.
The Horsehead's dramatic pillar is made of sterner stuff than the clouds surrouding the nebula, which have already dissipated. But the pillar will disintegrate as well in another 5 million years or so, astronomers say, and the Horsehead will go the way of the dodo.
The Hubble Space Telescope is perhaps best known for its photos in visible light. But the telescope's Wide Field Camera 3, which was installed by spacewalking astronauts in 2009, also takes crisp images in infrared wavelengths, researchers said.
Hubble, a collaboration between NASA and the European Space Agency, has made more than 1 million science observations since its 1990 launch, and it's still going strong. NASA announced last month that it had extended the telescope's science operations through April 2016.
NASA's highly anticipated successor to Hubble, the $8.8 billion James Webb Space Telescope, is slated to blast off in 2018. JWST is optimized to view in infrared light. | 0.847965 | 3.22518 |
Stargazers will be treated to a rare skyshow when NASA’s OSIRIS-REx spacecraft ‘sling-shots’ its way over Australian skies on September 23, 2017.
Using Earth’s gravity to give it an orbital boost, OSIRIS-REx will rendezvous with the asteroid Bennu in 2018. The Earth flyby will give astronomers and those with high-end cameras a chance to view this rare encounter.
OSIRIS-REx is on an extraordinary journey to bring back to Earth a sample from the surface of the carbonaceous asteroid Bennu that could potentially record the early history of the solar system and molecular precursors to the origin of life.
The ‘sling-shot’ or Earth Gravity Assist manoeuvre will bring OSIRIS-REx close enough to Earth to be viewed through high-end cameras, where Desert Fireball Network (DFN) team members will be stationed across Australia in strategic locations to optimise viewing angles, creating a 3D triangulated track above Australia and demonstrating the capabilities of the DFN system.
Curtin University Professor Phil Bland, team leader of the Desert Fireball Network, and member of the OSIRIS-REx science team, said the rare encounter would offer an opportunity to highlight the capabilities of the DFN and planetary science research in Australia.
“The teams will be equipped with high-end DSLR cameras that will work together to track the OSIRIS-REx spacecraft across the sky from each viewpoint, enabling the DFN team to create a 3D triangulated track of its sling-shot around the Earth,” Professor Bland said.
“This important milestone furthers the work of planetary research here at Curtin and our relationship with NASA.
“We know very little about how the planets came together and why the Earth has the composition that it does. The samples that OSIRIS-REx delivers may hold the key to some of these answers.”
The DFN project is based at Curtin University in Perth, Western Australia, and aims to unlock the mysteries of our universe by studying meteorites, fireballs and their pre-Earth orbits.
Together with NASA, the DFN is expanding to a Global Fireball Observatory through the Solar System Exploration Research Virtual Institute (SSERVI). SSERVI’s science and technical research focuses on the connection between planetary exploration and human exploration via funded US teams and a large network of international partners.
The apparent pathway of the OSIRIS-REx spacecraft over Australian skies will take an hour, beginning over Rockhampton at 00.22am (AEST) and exit over Adelaide at 00.53am local time on September 23, 2017. | 0.916728 | 3.388219 |
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Most of the objects the SDSS sees are so far away that they do not appear to move. Most stars in the sky move so slowly, you would not notice any significant change over your whole lifetime.
But some objects are much closer to Earth, so they move much more quickly across the night sky. The planets move across the sky - our word "planet" comes from the Greek word for "wanderer." If you look carefully, you can see the planets move from night to night. With a large telescope, you can see the planets move right before your eyes!
The planets are the largest, most famous moving sky objects. But when our solar system formed, not all the matter combined to form planets. If a planet tried to form near Jupiter, Jupiter's enormous gravity would rip it apart. So the Solar System has a lot of leftover debris, mostly between the orbits of Mars and Jupiter.
The first asteroid was discovered in 1801 by Italian astronomer Giuseppe Piazzi. At first, he thought he had discovered a comet. But after he calculated its orbit, he realized that he had found a totally new type of object between Mars and Jupiter.
Most asteroids are small pieces of rock a few kilometers across. The largest is named Ceres and is about 900 km across. But large asteroids are rare: there are only 26 known asteroids larger than 200 km across. The total mass of all the asteroids is probably about the mass of the Earth's moon.
Asteroids are so close that they move across the sky quickly. The SDSS telescope takes pictures through 5 filters, one after the other. If the asteroid is close enough, it appears to move between filters. You can see a very fast moving asteroid in the picture at the right. The asteroid moved as the picture was taken in each filter.
Notice how the red and green streaks are close together and the blue streak is farther away. Although the SDSS takes images through five filters, astronomers use only three to make the color image you see. Color computer images are made by combining red, green, and blue pictures. To make SDSS pictures, the i filter makes the red picture, r filter makes the green picture, and the g filter makes the blue picture. (Note: the assignment of picture colors to filters is not related to the color of light the filters see.)
Look at the picture below, which shows the SDSS camera. Look at the labels in the upper left corners of the center squares. You can see that the r and i filters are close together and the g filter is at the other end. Therefore, more time passes between the red and blue images than between the green and red images. The asteroid moves farther in this time. This is why the blue streak is so far from the other streaks in the picture above.
Most asteroids move much more slowly than the one above. Most do not move much as a picture is being taken, and most do not even move significantly between the r and i filters. But since the g filter is at the other end of the camera, the asteroid will move much more by the time the g filter takes a picture of that area of sky. For such a slow-moving asteroid, you will see what appears to be a yellow dot (the combination of red and green) next to a blue dot!
The animation to the right shows what happens when the SDSS's filters scan a part of sky with a slow-moving asteroid. The asteroid is the brown dot moving across the animation. The animation shows the camera's r, i, and g filters sweeping across the sky. (In reality, it works the opposite - the cameras stay still and the sky moves during the night.) The camera takes a picture of the asteroid through the r and i filters (which are next to one another), leaving a yellow dot. When the g filter scans the asteroid, the asteroid has moved; it shows up as a blue dot in its new place.
In the last frame of the animation, the asteroid is removed, leaving only the image that would be seen by the SDSS. So this animation tells you how to find asteroids - just look for a yellow dot and a blue dot close together! | 0.820402 | 3.798219 |
Europe’s Galileo satellite navigation system – already serving users globally – has now provided a historic service to the physics community worldwide, enabling the most accurate measurement ever made of how shifts in gravity alter the passing of time, a key element of Einstein’s Theory of General Relativity.
Two European fundamental physics teams working in parallel have independently achieved about a fivefold improvement in measuring accuracy of the gravity-driven time dilation effect known as ‘gravitational redshift.’
The prestigious Physical Review Letters journal has just published the independent results obtained from both consortiums, gathered from more than a thousand days of data obtained from the pair of Galileo satellites in elongated orbits.
“It is hugely satisfying for ESA to see that our original expectation that such results might be theoretically possible have now been borne out in practical terms, providing the first reported improvement of the gravitational redshift test for more than 40 years,” comments Javier Ventura-Traveset, Head of ESA’s Galileo Navigation Science Office.
“These extraordinary results have been made possible thanks to the unique features of the Galileo satellites, notably the very high stabilities of their onboard atomic clocks, the accuracies attainable in their orbit determination and the presence of laser-retroreflectors, which allow for the performance of independent and very precise orbit measurements from the ground, key to disentangle clock and orbit errors.”
These parallel research activities, known as GREAT (Galileo gravitational Redshift Experiment with eccentric sATellites), were led respectively by the SYRTE Observatoire de Paris in France and Germany’s ZARM Center of Applied Space Technology and Microgravity, coordinated by ESA’s Galileo Navigation Science Office and supported through its Basic Activities.
Happy results from an unhappy accident
These findings are the happy outcome of an unhappy accident: back in 2014 Galileo satellites 5 and 6 were stranded in incorrect orbits by a malfunctioning Soyuz upper stage, blocking their use for navigation. ESA flight controllers moved into action, performing a daring salvage in space to raise the low points of the satellites’ orbits and make them more circular.
Once the satellites achieved views of the whole Earth disc their antennas could be locked on their homeworld and their navigation payloads could indeed be switched on. The satellites are today in use as part of Galileo search and rescue services while their integration as part of nominal Galileo operations is currently under final assessment by ESA and the European Commission.
However, their orbits remain elliptical, with each satellite climbing and falling some 8500 km twice per day. It was these regular shifts in height, and therefore gravity levels, which made the satellites so valuable to the research teams.
Reenacting Einstein’s prediction
Albert Einstein predicted a century ago that time would pass more slowly close to a massive object, a finding that has since been verified experimentally several times – most significantly in 1976 when a hydrogen maser atomic clock on the Gravity Probe-A suborbital rocket was launched 10 000 km into space, confirming Einstein’s prediction to within 140 parts per million.
In fact, atomic clocks aboard navigation satellites must already take into account the fact that they run faster up in orbit than down on the ground – amounting to a few tenths of a microsecond per day, which would result in navigation errors of around 10 km daily, if uncorrected.
The two teams relied upon the stable timekeeping of the passive hydrogen maser (PHM) clocks aboard each Galileo – stable to one second in three million years – and kept from drifting by the worldwide Galileo ground segment.
“The fact that the Galileo satellites carry passive hydrogen maser clocks, was essential for the attainable accuracy of these tests,” noted Sven Hermann at the University of Bremen’s ZARM Center of Applied Space Technology and Microgravity.
“While every Galileo satellite carries two rubidium and two hydrogen maser clocks, only one of them is the active transmission clock. During our period of observation, we focus then on the periods of time when the satellites were transmitting with PHM clocks and assess the quality of these precious data very carefully. Ongoing improvements in the processing and in particular in the modelling of the clocks, might lead to tightened results in the future.”
Refining the results
A key challenge over three years of work was to refine the gravitational redshift measurements by eliminating systematic effects such as clock error and orbital drift due to factors such as Earth’s equatorial bulge, the influence of Earth’s magnetic field, temperature variations and even the subtle but persistent push of sunlight itself, known as ‘solar radiation pressure.’
“Careful and conservative modelling and control of these systematic errors has been essential, with stabilities down to four picoseconds over the 13 hours orbital period of the satellites; this is four millionth of one millionth of a second,” Pacôme Delva of SYRTE Observatoire de Paris.
“This required the support of many experts, with notably the expertise of ESA thanks to their knowledge of the Galileo system.”
Precise satellite tracking was enabled by the International Laser Ranging Service, shining lasers up to the Galileos’ retro-reflectors for centimetre-scale orbital checks.
Major support was also received from the Navigation Support Office based at ESA’s ESOC operations centre in Germany, whose experts generated the reference stable clock and orbit products for the two Galileo eccentric satellites and also determined the residual errors of the orbits after the laser measurements.
European Space Agency
Sven Herrmann et al. Test of the Gravitational Redshift with Galileo Satellites in an Eccentric Orbit. Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.121.231102
P. Delva et al. Gravitational Redshift Test Using Eccentric Galileo Satellites. Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.121.231101
The relativistic eccentricity of Galileo satellites 5 and 6 reaches a peak amplitude of approximately 370 nanoseconds (billionths of a second), driven by the shifting altitude, and hence changing gravity levels, of their elliptical orbits around Earth. A periodic modulation of this size is clearly discernible, given the relative frequency stability of the Passive Hydrogen Maser atomic clocks aboard the satellites
Credit: European Space Agency | 0.86731 | 3.595449 |
What is like in the core of large rocky planets? Using high-powered laser beams, a team of researchers from Princeton University, Lawrence Livermore National Laboratory and the University of Rochester have simulated conditions inside those so-called super-Earths, exoplanets that have up to ten times that of Earth's mass.
Super-Earths have long captured astronomers’ attention because a lot of them have Earth-like planetary features. If they also orbit a star in the habitable zone, they could be prime candidates to host alien life form. These exoplanets all have a mass higher than Earth's, but substantially below the masses of the Solar System's ice giants such as Uranus and Neptune.
The first super-Earths were discovered orbiting around a pulsar called PSR B1257+12 in 1992. The two outer planets of the system have masses approximately four times Earth. In the following decades, 2,000 of super-Earths have been found.
In August 2016, astronomers announced the detection of Proxima b. It is an exoplanet that is 1.3 times the size of earth, and its red dwarf star Proxima Centauri, the closest star to the Sun, in the so-called Goldilocks zone. The news has triggered huge public interests of exoplanets and extra-terrestrial life.
Although all are rocky planets, different makeup ingredients could determine the size of the planets. For example, Iron-rich planets are smaller and denser, when compared to other planets of comparable mass but made of other elements such as silica, carbon, water and even carbon monoxide.
The structures and compositions of super-Earths are intriguing subjects because we cannot find any example in our own backyard. Mercury, Venus, and Mars are rocky planets, but they are all smaller than the Earth.
Scientists can safely assume the main components of super-Earths are iron-silicon alloy due to their size and density relationship. By studying how iron and silicon alloys behave under an extraordinarily high pressure created by the laser, researchers are modeling what could be happening at the core of super-Earths and gain new insights into the nature of these planetary giants.
In the study, two samples of the iron-silicon alloy were compressed for only a tiny fraction of a second, just long enough to allow scientists to probe the atomic structure using a technique called X-ray diffraction. The pressures measured in this study was 1,314 gigapascals (GPa) at the highest, almost four times higher compared to the Earth (330-360 GPa). The X-ray diffraction pattern provided information on the density and crystal structure of the iron-silicon alloys, revealing that the crystal structure changed with higher silicon content and generate new, more robust models for the interior structure of large, rocky exoplanets.
The work was recently published in the journal Science Advances
NASA Confirms Closest Super-Earth Ever. (Wall Street Journal) | 0.914982 | 3.872878 |
NASA used images from two orbiting observatories to create this video of the comet Pan-STARRS. It appears in the middle, its tail streaming away to the right. At left, solar wind streams away from the sun and Mercury moves higher. At right, Earth is stationary.
Comet Pan-STARRS is putting on a bit of a show for those in the Northern Hemisphere through the end of this month. We're seeing some beautiful photos, such as those taken this week by AFP/Getty's Stan Honda. He pointed his camera skyward near Magdalena, N.M.
The best viewing came earlier this week, but Forbes writes that if you're in the Northern Hemisphere you're not too late to see Pan-STARRS. It offers some tips:
"In order to view the comet, you'll need to find a spot where you have an unobstructed view of the western sky, all the way down to the horizon. Try to get away from cities so you don't have to deal with light pollution, and cross your fingers for clear weather, because clouds will block the show. Wait until about half an hour after sunset, and then look towards the west [and to the left of the moon]. ...
"Pan-STARRS will remain in our night sky through the end of the month. Each night it will appear slightly higher in the sky, and further to the east. But don't wait too long to get your glimpse: As March draws to a close, the light from the comet will get dimmer and dimmer. If you have a good pair of binoculars or a decent telescope, that will help."
What caught our eye today is a view of Pan-STARRS from space. NASA used its STEREO (Solar TErrestrial RElations Observatory) to produce a video of PanSTARRS that combines two orbiting perspectives.
Here's how the space agency describes what it has created:
"In early March 2013, Comet Pan-STARRS became visible to the naked eye in the night sky in the Northern Hemisphere, appearing with a similar shape and brightness as a star, albeit with a trailing tail. Up in space, NASA's STEREO (Solar TErrestrial RElations Observatory) has an even better view. This movie, captured by the STEREO-B spacecraft on March 9-12, shows the comet and its fluttering tail as it moves through space. The stationary planet on the right is Earth, and the moving planet on the left is Mercury. The material moving in from the left is solar wind streaming off the sun, which is out of view on the left. Comet scientists say the tail looks quite complex and it will take computer models to help understand exactly what's happening in STEREO's observations."
How did Pan-STARRS get its name? Space.com says it comes from how it was discovered in June 2011, "by astronomers using the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) in Hawaii. The comet's official name is C/2011 L4 (PANSTARRS)."
Space.com also offers "6 Fun Facts About Comet Pan-STARRS," including this:
"You will never see it again," because the comet is on "a 110,000-year path around the sun."
Stan Honda /AFP/Getty Images
Comet PanSTARRS in the sky above Magdalena, N.M., on March 12.
Stan Honda /AFP/Getty Images | 0.865254 | 3.463 |
Oh Planet Nine, when will you stop toying with us?
Whether you call it Planet Nine, Planet X, the Perturber, Jehoshaphat, “Phattie,” or any of the other proposed names—either serious or flippant—this scientific back and forth over its existence is getting exhausting.
Is this what it was like when they were arguing whether Earth is flat or round?
Continue reading “Maybe the Elusive Planet 9 Doesn’t Exist After All”
Even though Earthling scientists are studying Mars intently, it’s still a mysterious place.
One of the striking things about Mars is all of the evidence, clearly visible on its surface, that it harbored liquid water. Now, all that water is gone, and in fact, liquid water couldn’t survive on the surface of the Red Planet. Not as the planet is now, anyway.
But it could harbour water in the past. What happened?
Continue reading “Mars Doesn’t Have Much of a Magnetosphere, But Here’s a Map”
For the child inside all of us space-enthusiasts, there might be nothing better than discovering a new type of explosion. (Except maybe bigger rockets.) And it looks like that’s what’s happened. Three objects discovered separately—one in 2016 and two in 2018—add up to a new type of supernova that astronomers are calling Fast Blue Optical Transients (FBOT).
Continue reading “A New Kind of Supernova Explosion has been Discovered: Fast Blue Optical Transients”
Thanks to the success of the Kepler mission, we know that there are multitudes of exoplanets of a type called “Hot Jupiters.” These are gas giants that orbit so close to their stars that they reach extremely high temperatures. They also have exotic atmospheres, and those atmospheres contain a lot of strangeness, like clouds made of aluminum oxide, and titanium rain.
A team of astronomers has created a cloud atlas for Hot Jupiters, detailing which type of clouds and atmospheres we’ll see when we observe different Hot Jupiters.
Continue reading “Extremely Hot Exoplanets Can Have Extreme Weather, Like Clouds of Aluminum Oxide and Titanium Rain”
The Milky Way has a number of satellite galaxies; nearly 60 of them, depedending on how we define them. One of them, called the Sagittarius Dwarf Spheroidal Galaxy (Sgr d Sph), may have played a huge role when it comes to humans, our world and our little civilization. A collision between the Milky Way and the Sgr d Sph may have created the Solar System itself.
Continue reading “The Solar System Might Not Exist if There Wasn’t a Huge Galactic Collision with the Milky Way Billions of Years Ago”
If we want to understand how the Universe evolves, we have to understand how its large structures form and evolve. That’s why astronomers study galaxy formation. Galaxies are enormous structures of stars, planets, gas, dust, and dark matter, and understanding how they form is critical to understanding the Universe itself.
In 2017, astronomers working with ALMA (Atacama Large Millimeter/sub-millimeter Array) discovered an ancient galaxy. This massive rotating disk galaxy was born when the Universe was only about 1.5 billion years old. According to the most accepted understanding of how galaxies form and evolve, it shouldn’t exist.
But there it is.
Continue reading “A Massive Rotating Disc Discovered in the Early Universe”
The Antarctic Peninsula is the northernmost part of Antarctica, and has the mildest climate on the continent. In January, the warmest part of the year, the temperature averages 1 to 2 °C (34 to 36 °F). And it’s getting warmer.
Those warm temperatures allow snow algae to grow, and now scientists have used remote sensing to map those algae blooms.
Continue reading “The Coast of Antarctica is Starting to Turn Green”
In 2017, astronomers used ALMA (Atacama Large Millimeter/sub-millimeter Array) to look at the star AB Aurigae. It’s a type of young star called a Herbig Ae star, and it’s less then 10 million years old. At that time, they found a dusty protoplanetary disk there, with tell-tale gaps indicating spiral arms.
Now they’ve taken another look, and found a very young planet forming there.
Continue reading “This is an Actual Image of a Planet-Forming Disc in a Distant Star System”
The date is finally set for OSIRIS-REx’s sampling maneuver. The spacecraft has been at asteroid Bennu since the end of December 2018. During that time, it’s found a few surprises, and mapped the surface in great detail.
Now, we can circle October 20th on our calendars, as the date OSIRIS-Rex will collect its sample.
Continue reading “OSIRIS-REx Will Collect a Sample from Bennu on October 20th”
We’ve found thousands and thousands of exoplanets now. And spacecraft like TESS will likely find thousands and thousands more of them. But most exoplanets are gassy giants, molten hell-holes, or frozen wastes. How can we find those needles-in-the-haystack habitable worlds that may be out there? How can we narrow our search?
Well, first of all, we need to find water. Oceans, preferably, since that’s where life began on Earth. And according to a new study, those oceans need to circulate in particular ways to support life.
Continue reading “Ocean Circulation Might Be the Key to Finding Habitable Exoplanets” | 0.907068 | 3.42324 |
Cold Gas in the Andromeda Galaxy
New radio map shows distribution of star forming regions in great detail
A new radio frequency map of the Andromeda galaxy has been made by a German-French research team of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn and the Institut de Radioastronomie Millimétrique (IRAM) in Grenoble. The map shows the first detailed distribution of cold gas in a neighbouring galaxy, revealing the sites where new stars are born. The motions of this gas were also obtained. With more than 800 hours of telescope time this study is one of the most extensive observational projects in millimetre radio astronomy (Astronomy & Astrophysics, Vol. 453 No. 2, July II 2006).
How are stars formed? This is one of the most important questions in astronomy. We know that star formation takes place in cold gas clouds with temperatures below -220 C (50 K). Only in these regions of dense gas can gravitation lead to a collapse and hence to star formation. Cold gas clouds in galaxies are composed preferentially of molecular hydrogen, H2 (two hydrogen atoms bound as one molecule). This molecule emits a weak spectral line in the infrared bandwidth of the spectrum that cannot be observed by Earth-based telescopes because the atmosphere absorbs this radiation. Therefore, astronomers study another molecule which is always found in the neighbourhood of H2, namely carbon monoxide, CO. The intense spectral line of CO at the wavelength of 2.6 mm can be observed with radio telescopes that are placed on atmospherically favourable sites: high and dry mountains, in the desert or at the South Pole. In cosmic space carbon monoxide is an indicator of conditions favourable for the formation of new stars and planets.
In our galaxy, the Milky Way, studies of the distribution of carbon monoxide have been carried out for a long time. Astronomers find enough cold gas for star formation during millions of years to come. But many questions are unanswered; for instance how this raw material of molecular gas comes to exist in the first place. Is it supplied by the early development stage of the Galaxy, or can it be formed from warmer atomic gas? Can a molecular cloud collapse spontaneously or does it need an action from outside to make it unstable and collapse? Since the Sun is located in the disk of the Milky Way it is very difficult to obtain an overview of the processes taking place in our Galaxy. Looking from "outside" would help and so too does a look at our cosmic neighbours.
The Andromeda galaxy, also known under its catalogue number M31, is a system of billions of stars, similar to our Milky Way. The distance of M31 is 'only' 2.5 million light years, making it the nearest spiral galaxy The galaxy extends over some 5 degrees in the sky and can be seen with the naked eye as a tiny diffuse cloud. Studies of this cosmic neighbour can help to understand processes in our own Galaxy. Unfortunately, we are seeing the disk of gas and stars in M31 nearly edge-on (see Fig. 1, right).
In 1995 a team of radio astronomers at the Institut de Radioastronomie Millimétrique (IRAM) in Grenoble (Michel Guélin, Hans Ungerechts, Robert Lucas) and at the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn (Christoph Nieten, Nikolaus Neininger, Elly Berkhuijsen, Rainer Beck, Richard Wielebinski) started the ambitious project of mapping the entire Andromeda galaxie in the carbon monoxide spectral line. The instrument used for this project was the 30-meter radio telescope of IRAM which is situated on Pico Veleta (2970 metres) near Granada in Spain. With an angular resolution of 23 arcseconds (at the observing frequency of 115 GHz = wavelength of 2.6 mm) 1.5 million individual positions had to be measured. To speed up the observing process a new method of measurement was used. Rather than observing at each position, the radio telescope was driven in strips across the galaxy with continuous recording of the data. This observing method, called 'on the fly', was especially developed for the M31 project; it is now standard practice, not only at the Pico Veleta radio telescope but also at other telescopes observing at millimeter wavelengths.
For each observed position in M31 not just one value of CO intensity was recorded, but 256 values simultaneously across the spectrum with a bandwidth of 0.2% of the central wavelength of 2.6 mm. Thus the complete observational data set consists of some 400 million numbers! The exact position of the CO line in the spectrum gives us information about the velocity of the cold gas. If the gas is moving towards us, then the line is shifted to shorter wavelengths. When the source moves away from us, then we see a shift to longer wavelengths. This is the same effect (the Doppler effect) that we can hear when an ambulance’s siren moves towards us or away from us. In astronomy the Doppler effect allows the motions of gas clouds to be studied; even clouds with different velocities seen in the same line of sight can be distinguished. If the spectral line is broad, then the cloud may be expanding or else it consists of several clouds at different velocities.
The observations were finished in 2001. With more than 800 hours of telescope time this is one of the largest observing projects carried out with the telescopes of IRAM or MPIfR. After extensive processing and analysis of the huge quantities of data, the complete distribution of the cold gas in M31 has just been published (see Fig. 1, left).
The cold gas in M31 is concentrated in very filigree structures in the spiral arms. The CO line appears well suited to trace the spiral arm structure. The distinctive spiral arms are seen at distances between 25,000 and 40,000 light years from the centre of Andromeda, where most of the star formation occurs. In the central regions, where the bulk of older stars are located, the CO arms are much weaker. As a result of the high inclination of M31 relative to the line of sight (about 78 degrees) the spiral arms seem to form a large, elliptical ring with a major axis of 2 degrees. In fact, for a long time Andromeda was taken, mistakenly, to be a 'ring'-galaxy.
The map of the gas velocities (see Fig. 2) resembles a snap shot of a giant fire wheel. On the one side (in the south, left) the CO gas is moving with some 500 km/second towards us (blue), but on the other side (north, right) with 'only' 100 km/second (red). Since the Andromeda galaxy is moving towards us with a velocity of about 300 km/second, it will closely pass the Milky Way in about 2 billion years. In addition, M31 is rotating with about 200 km/second around its central axis. Since the inner CO clouds are moving on a shorter path than the outer clouds, they can overtake each other. This leads to a spiral structure.
The density of the cold molecular gas in the spiral arms is much larger than in the regions between the arms, whereas the atomic gas is more uniformly distributed. This suggests that molecular gas is formed from the atomic gas in the spiral arms, especially in the narrow ring of star formation. The origin of this ring is still unclear. It could be that the gas in this ring is just material not yet used for stars. Or perhaps the very regular magnetic field in M31 triggers the star formation in the spiral arms. Observations with the Effelsberg telescope showed that the magnetic field closely follows the spiral arms seen in CO.
The ring of star formation ('birth zone') in our own Milky Way, extending from 10,000 to 20,000 light years from the centre, is smaller than in M31. In spite of this, it contains nearly 10 times as much molecular gas (see table in Appendix). As all galaxies are about the same age, the Milky Way has been more economical with its raw material. On the other hand, the many old stars near the centre of M31 indicate that in the past the star formation rate was much higher than at present: here most of the gas has already been processed. The new CO map shows us that Andromeda was very effective in forming stars in the past. In some billions of years from now our Milky Way may look similar to Andromeda now. | 0.860161 | 4.026915 |
- Title: Implementing Molecular Hydrogen in Hydrodynamic Simulations of Galaxy Formation
- Author: Charlotte Christensen
- Author’s Institution: Steward Observatory, University of Arizona
Galaxy simulations are a big business in astronomy these days. We’ve talked about papers that use simulations in many previous astrobites, and Nathan even wrote a couple of posts about how to use Gadget-2 to create your own. With so many researchers using simulations to probe different aspects of galaxy formation and evolution, one might begin to wonder what could possibly be left. As it turns out, the answer is a lot. While a simple simulation like the one Nathan described is easy to set up and run, creating a truly accurate model of how galaxies evolve is very, very hard. Not only are galaxies complicated to model spatially, with important structure on scales from solar systems to galaxy clusters, but they are also next to impossible to manage temporally, with relevant time steps ranging from seconds, the sort of scale important in supernova explosions, to billions of years, the time it takes for one galaxy to go from making its first stars to what we see today. With that much to consider, creating more accurate galaxy simulations is a field that can keep lots of astronomers busy for a long time. In today’s astrobite, we feature a paper that tackles one of the major missing pieces in many galaxy simulations – the inclusion of molecular hydrogen (H2).
So what’s so important about molecular hydrogen? Well, as we’ve mentioned in several astrobites, observational evidence tells us that stars form in giant, dense clouds of molecular gas. So including this gas in a theoretically-motivated way in a simulation should provide a more physically accurate view of the way star formation proceeds and affects galaxy evolution. In addition, in small, metal-poor galaxies, which were prevalent in the early universe and exist today as dwarf galaxies, self-shielding of molecular hydrogen was important in helping gas cool – gas between 200 K and 5000 K loses energy via radiation and condenses into the sorts of regions where stars form (more on shielding in a moment). Because of its efficient cooling properties, molecular gas tends to lead to clumpier regions in the disks of galaxies. This clumpiness is interesting in its own right, as it can give us clues about spiral structure and overdensities in disks of galaxies, but is also important for another reason: supernova feedback. A dense interstellar medium (ISM) full of molecular would more readily absorb the energy of supernovae. This may lead to galactic-scale outflows, which have been observed in many galaxies but are not yet well understood. Essentially, correctly implementing molecular hydrogen in a simulation should affect nearly everything.
In this paper, the authors simulate two dwarf galaxies, one with molecular hydrogen and one without. The abundance of molecular hydrogen in the simulation (as in reality) is governed by its formation and destruction mechanisms; H2 tends to form on dust grains, so the dust-to-gas ratio and metal content of the gas in the galaxy is important, and H2 is primarily destroyed by radiation from nearby stars, which photo-dissociates it. In addition, the density of the gas is imporant, because H2 can self shield – molecules on the outside of a cloud get photo-dissociated, but if the surface density of the gas is high enough, the radiation never penetrates to the interior of the cloud. Other than the implementation of molecular hydrogen, everything about the two simulations is the same, including the resolution, initial conditions, and supernova feedback. The simulations are then run from a very early time in the universe, all the way to today, so that the results can be compared with current observations of nearby galaxies.
The figure at right shows the two simulated galaxies overlaid on a color-magnitude diagram with a number of observed dwarf galaxies. As the figure shows, both the color and brightness of the galaxies are within the range of scatter of the observations. The somewhat surprising fact is that the galaxy with molecular hydrogen (indicated by the square) is both bluer (as indicated by its lower position on the y-axis), and brighter than the galaxy without H2. This means that the galaxy with H2 has more young stars and that there was more star formation in its past. This is surprising because in the simulation with H2, star formation is tied to the amount of molecular gas available (as opposed to being tied to the total amount of gas available, as in the other simulation). Since there is less molecular gas than the total amount of gas in the galaxy, requiring a certain density of H2 to form stars could make star formation less efficient. But in fact, the inclusion of the molecular gas makes the overall amount of star formation more efficient, because of the colder, clumpier state of the interstellar gas, which is naturally conducive to forming stars.
In addition to having more star formation at late times and having a larger stellar mass, the authors find that the galaxy simulated with molecular hydrogen ended up slightly larger and had more total gas at the end of the evolution. These differences can all be tied to the changes in the interstellar medium, which became colder and denser with the inclusion of H2. The increased clumpiness also led to more star formation at large galactic radii, because there were regions farther out in the galaxy with high enough densities for stars to form. All of these changes highlight the importance of correctly modeling molecular gas in simulations, as it can have a large effect on a galaxy’s size, structure, brightness, gas content, metallicity, and more. | 0.834976 | 4.129924 |
Moon* ♈ Aries
Moon phase on 6 April 2073 Thursday is Waning Crescent, 28 days old Moon is in Aries.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 7 days on 30 March 2073 at 11:04.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Moon is passing about ∠5° of ♈ Aries tropical zodiac sector.
Lunar disc appears visually 8.1% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1768" and ∠1917".
Next Full Moon is the Pink Moon of April 2073 after 15 days on 22 April 2073 at 01:54.
There is medium ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at very acute angle, so their combined tidal force is moderate.
The Moon is 28 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 905 of Meeus index or 1858 from Brown series.
Length of current 905 lunation is 29 days, 17 hours and 58 minutes. It is 1 hour and 57 minutes longer than next lunation 906 length.
Length of current synodic month is 5 hours and 14 minutes longer than the mean length of synodic month, but it is still 1 hour and 49 minutes shorter, compared to 21st century longest.
This lunation true anomaly is ∠168.4°. At the beginning of next synodic month true anomaly will be ∠192.2°. The length of upcoming synodic months will keep decreasing since the true anomaly gets closer to the value of New Moon at point of perigee (∠0° or ∠360°).
Moon is reaching point of apogee on this date at 05:19, this is 13 days after last perigee on 23 March 2073 at 16:57 in ♍ Virgo. Lunar orbit is starting to get closer, while the Moon is moving inward the Earth for 14 days ahead, until it will get to the point of next perigee on 21 April 2073 at 03:38 in ♎ Libra.
This apogee Moon is 406 521 km (252 600 mi) away from Earth. This is the year's farthest apogee of 2073. It is 1 113 km farther than the mean apogee distance, but it is still 188 km closer than the farthest apogee of 21st century.
3 days after its descending node on 3 April 2073 at 11:42 in ♒ Aquarius, the Moon is following the southern part of its orbit for the next 11 days, until it will cross the ecliptic from South to North in ascending node on 17 April 2073 at 19:11 in ♌ Leo.
15 days after beginning of current draconic month in ♍ Virgo, the Moon is moving from the second to the final part of it.
7 days after previous South standstill on 30 March 2073 at 05:47 in ♑ Capricorn, when Moon has reached southern declination of ∠-19.120°. Next 7 days the lunar orbit moves northward to face North declination of ∠19.238° in the next northern standstill on 14 April 2073 at 00:42 in ♋ Cancer.
After 1 day on 7 April 2073 at 14:14 in ♈ Aries, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.848363 | 3.20523 |
Unprecedented observations of a nova outburst in 2018 by a trio of satellites, including two NASA missions, have captured the first direct evidence that most of the explosion’s visible light arose from shock waves — abrupt changes of pressure and temperature formed in the explosion debris.
A nova is a sudden, short-lived brightening of an otherwise inconspicuous star. It occurs when a stream of hydrogen from a companion star flows onto the surface of a white dwarf, a compact stellar cinder not much larger than Earth. NASA’s Fermi and NuSTAR space telescopes, together with the Canadian BRITE-Toronto satellite and several ground-based facilities, studied the nova.
“Thanks to an especially bright nova and a lucky break, we were able to gather the best-ever visible and gamma-ray observations of a nova to date,” said Elias Aydi, an astronomer at Michigan State University in East Lansing who led an international team from 40 institutions. “The exceptional quality of our data allowed us to distinguish simultaneous flares in both optical and gamma-ray light, which provides smoking-gun evidence that shock waves play a major role in powering some stellar explosions.”
The 2018 outburst originated from a star system later dubbed V906 Carinae, which lies about 13,000 light-years away in the constellation Carina. Over time — perhaps tens of thousands of years for a so-called classical nova like V906 Carinae — the white dwarf’s deepening hydrogen layer reaches critical temperatures and pressures. It then erupts in a runaway reaction that blows off all of the accumulated material.
Each nova explosion releases a total of 10,000 to 100,000 times the annual energy output of our Sun. Astronomers discover about 10 novae each year in our galaxy.
Fermi detected its first nova in 2010 and has observed 14 to date. Although X-ray and radio studies had shown the presence of shock waves in nova debris in the weeks after the explosions reached peak brightness, the Fermi discovery came as a surprise.
Gamma rays — the highest-energy form of light — require processes that accelerate subatomic particles to extreme energies. When these particles interact with each other and with other matter, they produce gamma rays. But astronomers hadn’t expected novae to be powerful enough to produce the required degree of acceleration.
Because the gamma rays appear at about the same time as the peak in visible light, astronomers concluded that shock waves play a more fundamental role in the explosion and its aftermath.
In 2015, a paper led by Brian Metzger at Columbia University in New York showed how comparing Fermi gamma-ray data with optical observations would allow scientists to learn more about nova shock waves. In 2017, a study led by Kwon-Lok Li at Michigan State found that the overall gamma-ray and visible emissions rose and fell in step in a nova known as V5856 Sagittarii. This implied shock waves produced more of the eruption’s light than the white dwarf itself.
The new observations from V906 Carinae, presented in a paper led by Aydi and published on Monday, April 13, in Nature Astronomy, spectacularly confirm this conclusion.
On March 20, 2018, the All-Sky Automated Survey for Supernovae, a set of two dozen robotic telescopes distributed around the globe and operated by Ohio State University, discovered the nova. By month’s end, V906 Carinae was dimly visible to the naked eye.
Fortuitously, a satellite called BRITE-Toronto was already studying the nova’s patch of sky. This miniature spacecraft is one of five 7.9-inch (20 centimeter) cubic nanosatellites comprising the Bright Target Explorer (BRITE) Constellation. Operated by a consortium of universities from Canada, Austria and Poland, the BRITE satellites study the structure and evolution of bright stars and observe how they interact with their environments.
BRITE-Toronto was monitoring a red giant star called HD 92063, whose image overlapped the nova’s location. The satellite observed the star for 16 minutes out of every 98-minute orbit, returning about 600 measurements each day and capturing the nova’s changing brightness in unparalleled detail.
“BRITE-Toronto revealed eight brief flares that fired up around the time the nova reached its peak, each one nearly doubling the nova’s brightness,” said Kirill Sokolovsky at Michigan State. “We’ve seen hints of this behavior in ground-based measurements, but never so clearly. Usually we monitor novae from the ground with many fewer observations and often with large gaps, which has the effect of hiding short-term changes.”
Fermi, on the other hand, almost missed the show. Normally its Large Area Telescope maps gamma rays across the entire sky every three hours. But when the nova appeared, the Fermi team was busy troubleshooting the spacecraft’s first hardware problem in nearly 10 years of orbital operations — a drive on one of its solar panels stopped moving in one direction. Fermi returned to work just in time to catch the nova’s last three flares.
In fact, V906 Carinae was at least twice as bright at billion-electron-volt, or GeV, energies as any other nova Fermi has observed. For comparison, the energy of visible light ranges from about 2 to 3 electron volts.
“When we compare the Fermi and BRITE data, we see flares in both at about the same time, so they must share the same source — shock waves in the fast-moving debris,” said Koji Mukai, an astrophysicist at the University of Maryland Baltimore County and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “When we look more closely, there is an indication that the flares in gamma rays may lead the flares in the visible. The natural interpretation is that the gamma-ray flares drove the optical changes.”
The team also observed the eruption’s final flare using NASA’s NuSTAR space telescope, which is only the second time the spacecraft has detected X-rays during a nova’s optical and gamma-ray emission. The nova’s GeV gamma-ray output far exceeded the NuSTAR X-ray emission, likely because the nova ejecta absorbed most of the X-rays. High-energy light from the shock waves was repeatedly absorbed and reradiated at lower energies within the nova debris, ultimately only escaping at visible wavelengths.
Putting all of the observations together, Aydi and his colleagues describe what they think happened when V906 Carinae erupted. During the outburst’s first few days, the orbital motion of the stars swept a thick debris cloud made of multiple shells of gas into a doughnut shape that appeared roughly edge-on from our perspective. The cloud expanded outward at less than about 1.3 million mph (2.2 million kph), comparable to the average speed of the solar wind flowing out from the Sun.
Next, an outflow moving about twice as fast slammed into denser structures within the doughnut, creating shock waves that emitted gamma rays and visible light, including the first four optical flares.
Finally, about 20 days after the explosion, an even faster outflow crashed into all of the slower debris at around 5.6 million mph (9 million kph). This collision created new shock waves and another round of gamma-ray and optical flares. The nova outflows likely arose from residual nuclear fusion reactions on the white dwarf’s surface.
Astronomers have proposed shock waves as a way to explain the power radiated by various kinds of short-lived events, such as stellar mergers, supernovae — the much bigger blasts associated with the destruction of stars — and tidal disruption events, where black holes shred passing stars. The BRITE, Fermi and NuSTAR observations of V906 Carinae provide a dramatic record of such a process. Further studies of nearby novae will serve as laboratories for better understanding the roles shock waves play in other more powerful and more distant events.
The Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Fermi was developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.
NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR's mission operations center is at the University of California Berkeley, and the official data archive is at NASA's High Energy Astrophysics Science Archive Research Center. ASI provides the mission's ground station and a mirror archive. Caltech manages JPL for NASA.
Banner image: A GIF cycles between an image of V906 Carinae taken on April 7, 2018, about 18 days after the nova's discovery and near its peak brightness, and one showing its faded appearance on May 4, 2019. Credit: Copyright 2018 by W. Paech + F. Hofmann, Team Chamaeleon, Chamaeleon and Onjala Observatory, Namibia, used with permission. | 0.9098 | 4.148116 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2020 May 27
Explanation: What are those dots between Saturn's rings? Our Earth and Moon. Just over three years ago, because the Sun was temporarily blocked by the body of Saturn, the robotic Cassini spacecraft was able to look toward the inner Solar System. There, it spotted our Earth and Moon -- just pin-pricks of light lying about 1.4 billion kilometers distant. Toward the right of the featured image is Saturn's A ring, with the broad Encke Gap on the far right and the narrower Keeler Gap toward the center. On the far left is Saturn's continually changing F Ring. From this perspective, the light seen from Saturn's rings was scattered mostly forward , and so appeared backlit. After more than a decade of exploration and discovery, the Cassini spacecraft ran low on fuel in 2017 and was directed to enter Saturn's atmosphere, where it surely melted.
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | 0.841287 | 3.119943 |
The Hubble Space Telescope is uniquely able to study planets that are observed to transit their parent stars. The extremely stable platform afforded by an orbiting spacecraft, free from the contaminating effects of the Earth's atmosphere, enables HST to conduct ultra-high precision photometry and spectroscopy of known transiting extrasolar planet systems. Among HST's list of successful observations of the first such system, HD 209458, are (1) the first detection of the atmosphere of an extrasolar planet, (2) the determination that gas is escaping from the planet, and (3) a search for Earth-sized satellites and circumplanetary rings. Numerous widefield, ground-based transit surveys are poised to uncover a gaggle of new worlds for which HST may undertake similar studies, such as the newly-discovered planet TrES-1. With regard to the future of Hubble, it must be noted that it is the only observatory in existence capable of confirming transits of Earth-like planets that may be detected by NASA's Kepler mission. Kepler could reveal Earth-like transits by the year 2010, but without a servicing mission it is very unlikely that HST would still be in operation.
When both the photometric transits and the radial velocity variations due to an extrasolar planet are observed, we are granted access to key quantities of the object that Doppler monitoring alone cannot provide. In particular, precise measurements of the planetary mass and radius allow us to calculate the average density and infer a composition. | 0.864217 | 3.690687 |
Students will learn about space with these leveled activities and lessons for different skills and grade ranges.
"Abandon all hope, ye who enter here," would be an appropriate warning for any space traveler foolish enough to approach a black hole. Black holes are proposed by astrophysicists as regions of space where gravity is so strong that the black holes act like stellar vacuum cleaners, sucking in matter and energy from space and allowing nothing, not even light, to escape.
The American physicist John Wheeler coined the term "black hole" in 1969, but, in fact, the theory has been around for much longer. As far back as 1783, English astronomer John Michell suggested that if a star were massive enough, it would have such a strong gravitational field that any light leaving the star would immediately be dragged back to the star's surface.
Michell's theories were largely ignored until 1939, when physicists Robert Oppenheimer and Hartland S. Snyder demonstrated that, based upon Albert Einstein's general theory of relativity, it would be possible for a star to collapse to the point where it would become a black hole.
|This artist's concept of frame dragging in a black hole shows the curvature of space-time. No, it's not science fiction! Frame dragging is where the fabric of space (not just matter) is literally shifted by the gravitational pull of a black hole. A black hole is a region defined as the ultimate expression of gravity. (NASA)|
How a Star Ages
In order to understand how a star could collapse into a black hole, it is first important to understand the life cycle of a star. A star is, essentially, a giant fusion reactor. At the central core of the star, swirling atoms of hydrogen gas collide with one another and merge to form helium. In the process of fusing together, these hydrogen atoms release a tremendous amount of energy in the form of heat.
At the same time, the star as a whole is continuously struggling against the inward pull of gravity. The inward gravity is from the central core of the star, which is surrounded by a massive envelope of gas. This inward pull is so immense that the star is always on the verge of collapsing under its own weight.
What prevents the star from collapsing? Tremendous internal pressure that is generated by the extreme heat at the star's core, which pushes outward, counterbalancing the inward pull of gravity. In our own sun, for example, the temperature at the core is about 25,000,000 — Fhrenheit (14,000,000—C), generating pressure 100 billion times the air pressure at sea level on Earth.
After thousands of millions of years, however, a star comes to the end of its hydrogen fuel supply. It starts to cool and contract. What happens next will depend entirely on the mass of the star.
Small stars, such as our Sun, will collapse to form objects called white dwarfs. About the size of the planet Earth, white dwarfs resist further collapse with internal pressure caused by electrons spinning at near the velocity of light. White dwarfs are very dense objects: 1 cubic inch of white dwarf weighs several tons. But they are considered lightweights when compared to neutron stars.
Neutron stars are the evolutionary end products of larger stars — those 1.4 to 2 times as large as the Sun. Electrons cannot resist the greater gravitational collapse of such stars, and are pushed into atomic nuclei where they combine with protons to form uncharged, tightly packed neutrons. Neutron stars are only a few miles in diameter. They weigh about 1 million tons per cubic centimeter. They can resist further collapse only by invoking the strongest force in nature — appropriately called the "strong force" — the force that binds together an atomic nucleus.
The strong force halts the imploding matter so abruptly — in a tenth of a second — that the collapsed stellar core acts as an explosive charge. The resulting explosion in the star's outer regions is called a supernova. Such celestial fireworks, observed by Chinese astronomers in July 1054, produced the Crab nebula, a cloud of gas that still writhes and glows today, 4,000 light-years from Earth.
What happens to a dying star that is more than twice as large as the Sun? Even the strong force cannot halt its in-falling momentum. It collapses completely, beyond the neutron-star stage, to an even smaller, denser object. Back in 1939, Oppenheimer and Snyder calculated that the gravitational field at the surface of such an object would become so strong that even light (traveling at a speed of 186,282 miles — 299,792 kilometers — per second) would be unable to escape. According to Einstein's theory of relativity, nothing in the universe can travel faster than light. Therefore, if light cannot escape, neither can anything else. The collapsed star becomes what we call a black hole.
Perhaps the best way to visualize a black hole is to imagine, for a moment, that space is a flat rubber sheet. If you were to drop a steel ball on the sheet, the rubber would curve downward, forming a shallow hole. This, in a nutshell, is how Einstein interpreted gravity. According to Einstein, gravity exists because massive objects bend the fabric of space around them. If, for example, we rolled a small marble across our rubber sheet, it would roll around the top of the hole formed by the steel ball, much in the way that the Earth orbits around the Sun.
Now imagine that we could increase the weight of the steel ball that we dropped on our rubber sheet. As the weight increased, the ball would sag farther and farther downward, creating a deep "gravity" hole. Eventually the rubber would be stretched so tight that the top of the hole would pinch together, closing off from the outside world the region containing the steel ball. Similarly, a collapsed star could eventually become so dense that it would curve space completely around on itself, isolating it from the rest of the universe.
How far would a star have to collapse before it "disappeared" from the visible universe? Astronomers refer to that critical size as the "event horizon" (otherwise known as the "Schwarzschild radius," named after German physicist Karl Schwarzschild). The event horizon is the outer boundary of a black hole, the exact point at which light rays fail to escape. The horizon acts as a one-way membrane — light and matter can cross the horizon into a black hole, but once inside, the horizon can never be recrossed.
The size of the event horizon is proportional to the mass of the collapsing star. Typically, the event horizon of a star would be on the order of miles. (For example, a star 10 times as massive as our Sun would have a Schwarzschild radius of 18.6 miles — 30 kilometers.)
Yet, according to our current knowledge of theoretical physics, once a star starts collapsing, no known force can stop it. It will continue to shrink past its event horizon, smaller and smaller, until it becomes a "singularity" — a mathematical point with zero volume and infinite density. This singularity lies at the very center of a black hole.
Exploring a Black Hole
If an astronaut were to attempt to visit a black hole, it would be a one-way trip. Before the astronaut even arrived at the event horizon, he or she would encounter tremendous tidal forces exerted by the black hole. Imagine, for example, that the astronaut is falling feetfirst toward the hole. The gravitational force pulling on the legs would be considerably stronger than the gravitational force pulling on the head. The difference between those two forces would stretch the astronaut like a piece of taffy.
As if that weren't bad enough, every single atom in the astronaut's body would be pulled toward the singularity at the black hole's center. For the astronaut the sensation might be similar to being squeezed by a giant fist.
After being stretched and squeezed by the black hole's gravitational forces, our intrepid space traveler would resemble a strand of spaghetti, and would likely not be in the mood for any further exploration.
Let's imagine for a moment that we could instead send a robot probe to investigate the black hole, one that could somehow stay intact despite the tremendous tidal forces. For the sake of discussion, we will mount a clock and a light source on the outside of our probe.
If we were watching the robot back on Earth, we would notice a curious phenomenon. The light source mounted on the side of the probe would start to change color. If the light, for instance, started out green, it would turn yellow, and then red as it got closer and closer to the event horizon of the black hole.
This is because light is composed of particles known as photons. As the photons move away from the black hole, they expend some of their energy as they try to escape from the hole's tremendous gravitational pull. The closer they are to the event horizon, the more energy they need to pull away.
The energy of a photon is proportional to the frequency of its radiation. As a result, light that loses energy will have a reduced frequency, and therefore a longer wavelength. This effect is known as "gravitational redshift." When light has a long wavelength, it is red in color.
Eventually, as the robot probe moves closer and closer to the event horizon, the light source will seem to disappear from view. The wavelength of the light will have become so long that it can only be detected with infrared and radio telescopes.
Just above the event horizon of the black hole, the wavelength of the light will approach infinity. Theoretically, radiation from the light source would still reach us back on Earth, but by then the wavelengths would be so long that no known scientific instruments would be able to detect them.
Meanwhile, the clock mounted on the side of our robot probe would also be behaving rather oddly. According to Einstein's theory of relativity, time slows down in the presence of a strong gravitational field — at least as viewed by an outside observer. As the probe got nearer and nearer to the black hole, astronomers back on Earth would notice that the clock was ticking more and more slowly.
The clock would continue to slow down, until the probe arrived at the event horizon, at which point the clock would stop altogether. The probe would appear frozen in time, hovering at the brink of the black hole for the rest of eternity.
Relativity predicts, however, that from the perspective of the robot, time would not seem to be affected in any way. The probe would arrive at the event horizon and enter the black hole without the clock slowing down for even an instant. Yet our dutiful robot explorer would have only a fraction of a second to contemplate this peculiar law of nature, at which point it would be pulled toward the center of the black hole, where it would encounter the singularity and be crushed to infinite density.
Proving That Black Holes Exist
All of this might sound very strange, and, in fact, for many years the majority of astronomers and physicists were reluctant to believe it. (The prominent English astronomer Sir Arthur Eddington even declared that there must be "a law of Nature to prevent a star from behaving in this absurd way!") If astronomers were to believe in black holes, they wanted more than just mathematical equations on a blackboard; they wanted hard, physical evidence.
Such evidence became available in 1967, when two British astronomers, Jocelyn Bell and Antony Hewish, discovered objects in space that were emitting regular pulses of radio waves. At first the astronomers thought that they had made contact with an alien civilization in a distant galaxy. They even named the objects "LGMs," for Little Green Men. Eventually, however, astronomers came to the conclusion that the objects were rotating neutron stars, emitting radiation in the form of narrow beams. Like a celestial lighthouse, each time the neutron star spun toward Earth, astronomers could detect a pulse. Hence, these objects were named pulsars.
This was the first hard evidence that neutron stars actually exist. If a star could collapse into an object as small as a neutron star, it then seemed reasonable to assume that it could collapse to an even smaller size and become a black hole.
One problem remains. How do you find a black hole? They aren't as accommodating as neutron stars, in that they don't emit easily detectable beams of radiation. In fact, according to conventional theory, black holes don't emit anything at all.
Astronomers saw a way out of this dilemma. Black holes exert an enormous gravitational force on nearby objects. So although scientists can't see a black hole"in the flesh," so to speak, they can observe how it would affect its surrounding environment.
To date, binary-star systems offer the best hope for locating a black hole. Astronomers have detected many such systems, where two stars orbit around one another. In some cases the astronomers have observed only one visible star, which seemed to be in orbit around an unseen companion. It is possible that the companion might be a star too faint to be seen from Earth. It is also possible, however, that the second object could be a black hole.
If a black hole were part of a binary-star system, its enormous tidal forces would pull gaseous material off the surface of the neighboring star. Like water draining out of a bathtub, the gaseous material would slowly spiral into the black hole, forming a swirling disk of gas around the event horizon, a phenomenon that astronomers refer to as an accretion disk.
Within the accretion disk, compression and internal friction would heat the gas to temperatures as high as 1,800,000— F (1,000,000— C). When gas gets this hot, it radiates tremendous energy in the form of X rays detectable by astronomers.
In 1970, a United States artificial satellite, the Uhuru, was launched off the coast of East Africa. (Uhuru is the Swahili word for "freedom.") Its purpose was to detect sources of X rays while above the interference of Earth's atmosphere. Uhuru has found more than 100 stars emanating X-ray pulses. One of the most powerful X-ray sources was Cygnus X-1, located about 6,000 light-years from Earth.
Closer examination of Cygnus X-1 revealed it to be a binary-star system, with a supergiant star orbiting around an unseen companion. By measuring the velocity and the orbital period of the supergiant star, astronomers were able to roughly calculate the mass of the unseen object. The object was estimated to be at least six solar masses (six times the mass of the Sun), far too massive to be either a white dwarf or a neutron star. By 1974, astronomers concluded that Cygnus X-1 must contain a black hole.
In 1997, astronomers found in the core of the active galaxy NGC 6521 what appears to be a warped, dusty disk swirling around a supermassive black hole, giving them the first direct line of sight into the immediate environment of a black hole.
In January 2000, astronomers found what may be the closest black hole to Earth — a mere 1,600 light years away. Located near the center of the Milky Way in the direction of the constellation Sagittarius, the black hole emits gamma rays continuously rather than in flashes or bursts.
And deep within the core of the distant galaxy NGC 4395, astronomers discovered what may be a new type of mid-mass black hole, weighing perhaps as "little" as 10,000 to 100,000 Suns.
Perhaps the best black-hole candidate yet discovered is a binary-star system that goes by the uninspiring name A0620-00. Like Cygnus X-1, A0620-00 emits intense levels of X-ray radiation. The binary system has a visible orange dwarf star, which orbits around a dark, unseen mass. In the late 1980s, astronomers studied the motions of the orange dwarf and estimated that the star's dark companion was 3.2 times the mass of our Sun.
With a mass that large, the dark object was placed high on the black-hole suspect list. But in order to get a more accurate estimate, astronomers would have to measure the velocity of the dark object. At first that seemed impossible: How can you measure an object that you cannot even see?
The Hubble Telescope has found seemingly conclusive evidence for massive black holes at the cores of many galaxies throughout our universe. One such galaxy, known as M87, is bright enough to see with a small backyard telescope. Others are distant galaxies with highly energetic nuclei. In some of the galaxies, the Hubble Telescope has detected disks of material spiraling inward toward the black hole; in other galaxies, it has found beams of energetic radiation and gaseous knots being ejected at tremendous speeds.
English physicist Stephen Hawking suggested that radiation might not only exist in the vicinity of a black hole, but that it actually might be leaking from the hole itself. Energy leaking from a black hole? It sounds impossible. But Hawking says that black holes emit radiation in the form of subatomic particles that do not obey the traditional laws of physics. Such "virtual" particles, as Hawking calls them, can be created in pairs in empty space, only to instantly collide and annihilate each other. If such a pair were to come into being near a black hole, one particle would be sucked in, while the other would escape into space.
As a black hole loses energy, it would also lose a proportionate amount of mass. Hawking's theory suggests that there might come a time when a black hole will lose so much mass that it will no longer be able to curve space around itself. The black hole would cease to be a black hole, and the remaining mass would likely explode outward, with a force equivalent to millions of hydrogen bombs.
But don't look up in the sky expecting to see a fireworks display of exploding black holes. A large black hole lives a very long time. More specifically, it would take trillions upon trillions of years for it to lose enough energy to explode outward. The universe itself has been around for only 20 billion years.
Yet it may be possible that very small black holes, formed in the early days of the universe, might be exploding just about now, releasing energy in the form of gamma rays, equivalent to about 100 million volts of electricity.
Astronomers are now searching the skies for just such bursts of gamma radiation. If found, then astronomers could verify what Stephen Hawking has been saying for the last 20 years: "Black holes ain't so black."
In 1895 H. G. Wells wrote a book about a device that could carry a man back and forth through time. The book was called The Time Machine, and for a century after it was published, the concept of time travel remained a favorite topic among writers of science fiction.
In 1988, however, science fiction moved closer to becoming science fact when American physicist Kip Thorne and his colleagues at the California Institute of Technology (Caltech) published a paper in the prestigious journal Physical Review Letters, titled "Wormholes, Time Machines, and the Weak Energy Condition."
Thorne didn't actually publish a blueprint for a do-it-yourself time machine. He speculated that an "arbitrarily advanced civilization" might be able to find a loophole in the laws of physics that would allow individuals to travel through time.
The loophole that Thorne had in mind is what physicists call a "wormhole." A wormhole is similar to a black hole, but with one noteworthy difference. At the bottom of a black hole, there is a singularity, a mathematical point of infinite mass through which nothing can pass.
A wormhole, by contrast, has no bottom. It has two "mouths" connected by a "throat." It is, essentially, a tunnel through space. A space traveler entering one mouth of a wormhole might emerge from the second mouth only a few seconds later, but halfway across the galaxy.
Einstein's equations predict that wormholes exist, although nobody has ever found one. American physicist John Wheeler has suggested that a good place to look for one would be at a submicroscopic level, where random fluctuations occur in the fabric of space-time. In such an environment, wormholes would spontaneously appear and collapse, giving space a frothy, foam-like appearance.
Kip Thorne suggests that an advanced civilization could pull a wormhole out of this foam, enlarge it, and then move its openings around the universe until the wormhole assumed a desired size, shape, and location. Unfortunately, once such a wormhole was created, it would be highly unstable. If a space traveler entered the wormhole, the throat might instantly pinch shut. Even moving at the speed of light, the space traveler might be unable to reach the other side of the wormhole before it collapsed around him or her.
In order to avoid such a catastrophe, the Caltech physicists recommend that our hypothetical advanced civilization thread the throat of the wormhole with what they call "exotic material." In order to prop open a wormhole a half a mile or so across, the material would have to possess a radial (outward) tension comparable to the pressure at the center of a neutron star. Kip Thorne believes that there is a 50–50 chance that the laws of physics permit such a substance to exist.
Once our "arbitrarily advanced scientists" finished building a safe, traversable wormhole, they would be ready to convert it into a time machine. At this point they would rely upon Albert Einstein's general theory of relativity. According to Einstein, time slows down for a moving object when it is measured by a stationary observer.
This is often illustrated with what is known as the "twin paradox." Imagine that you have twin brothers, named Bill and Ted, each 20 years old. Bill takes off in a spaceship, while Ted stays back on Earth. Bill's destination is a star 25 light-years away. (A light-year is the distance that a beam of light can travel in one year.) His spaceship can attain a speed of 99.9 percent of the speed of light. From Ted's point of view, Bill will be gone for 50 years (25 years to reach the star, plus 25 years to return). However, from Bill's point of view on board the spaceship, the entire trip will last only one year. This effect is known as "time dilation." When Bill returns to Earth, he will be only 21 years old, but his brother Ted will be a 70-year-old man.
Now, instead of two brothers, imagine that we are dealing with two mouths of a wormhole. Our advanced civilization could move one end of the wormhole, perhaps by using a heavy asteroid or a neutron star as a kind of gravitational tugboat. If the mouth of the wormhole were accelerated to a high enough speed and then returned to its original position, it would behave just like our space-traveling twin brother. A clock fixed to the moving mouth would tick more slowly than one at the stationary mouth.
For instance, the clock outside the accelerated mouth might read 12:00 noon, but the clock outside the stationary mouth would read 1:00 p.m. By passing from one mouth to the other, a space traveler could move back and forth through time.
How far could our traveler move through time? That would depend upon how long and how fast the wormhole mouth is accelerated. If the mouth were moved at 99.9 percent of the speed of light for 10 years, the time difference between the two mouths would be nine years and 10 months. Theoretically, if you accelerated a wormhole mouth fast enough and long enough, the time difference between the two mouths could be stretched across several centuries.
There is, however, a limitation to Kip Thorne's time machine. Common sense tells us you cannot travel back to a time before you created the wormhole and accelerated one of the mouths through space. After all, what we're doing is exploiting the relative rate at which time passes under the effects of speed. So, unfortunately, you could not pop back through time to visit the dinosaurs. Unless, of course, you were lucky enough to find a time hole that had already been constructed by an advanced civilization several million years ago. | 0.906503 | 4.089037 |
NGC 3175 is located around 50 million light-years away in the constellation of Antlia (The Air Pump). The galaxy can be seen slicing across the frame in this image from the NASA/ESA Hubble Space Telescope, with its mix of bright patches of glowing gas, dark lanes of dust, bright core, and whirling, pinwheeling arms coming together to paint a beautiful celestial scene.
The galaxy is the eponymous member of the NGC 3175 group, which has been called a nearby analogue for the Local Group. The Local Group contains our very own home galaxy, the Milky Way, and around 50 others — a mix of spiral, irregular, and dwarf galaxies. The NGC 3175 group contains a couple of large spiral galaxies — the subject of this image, and NGC 3137 — and numerous lower-mass spiral and satellite galaxies. Galaxy groups are some of the most common galactic gatherings in the cosmos, and they comprise 50 or so galaxies all bound together by gravity.
This image comprises observations from Hubble’s Wide Field Camera 3. | 0.859439 | 3.010673 |
ULAS J1342+0928 is the most distant known quasar detected and contains the most distant and oldest known supermassive black hole, at a reported redshift of z = 7.54, surpassing the redshift of 7 for the previously known most distant quasar ULAS J1120+0641. The ULAS J1342+0928 quasar is located in the Boötes constellation. The related supermassive black hole is reported to be "800 million times the mass of the sun".
Artist concept of a similar related quasar
|Observation data (Epoch J2000.0)|
|Right ascension||13h 42m 08.10s|
|Declination||+09° 28′ 38.61″|
|Distance||29.36 Gly (9.00 Gpc)|
13.1 Gly (4.0 Gpc)
(light travel distance)
|ULAS J134208.10+092838.61, Quasar20171206|
|See also: Quasar, List of quasars|
On 6 December 2017, astronomers published that they had found the quasar using data from the Wide-field Infrared Survey Explorer (WISE) combined with ground-based surveys from one of the Magellan Telescopes at Las Campanas Observatory in Chile, as well as the Large Binocular Telescope in Arizona and the Gemini North telescope in Hawaii. The related black hole of the quasar existed when the universe was about 690 million years old (about 5 percent of its currently known age of 13.80 billion years).
The quasar comes from a time known as "the epoch of reionization", when the universe emerged from its Dark Ages. Extensive amounts of dust and gas have been detected to be released from the quasar into the interstellar medium of its host galaxy.
ULAS J1342+0928 has a measured redshift of 7.54, which corresponds to a comoving distance of 29.36 billion light-years from Earth. As of December 2017[update], it is the most distant quasar yet observed. The quasar emitted the light observed on Earth today less than 690 million years after the Big Bang, about 13.1 billion years ago.
The quasar's luminosity is estimated at 4×1013 solar luminosities. This energy output is generated by a supermassive black hole estimated at 8×108 solar masses. According to lead astronomer Bañados, "This particular quasar is so bright that it will become a gold mine for follow-up studies and will be a crucial laboratory to study the early universe."
The light from ULAS J1342+0928 was emitted before the end of the theoretically-predicted transition of the intergalactic medium from an electrically neutral to an ionized state (the epoch of reionization). Quasars may have been an important energy source in this process, which marked the end of the cosmic Dark Ages, so observing a quasar from before the transition is of major interest to theoreticians. Because of their high ultraviolet luminosity, quasars also are some of the best sources for studying the reionization process. The discovery is also described as challenging theories of black hole formation, by having a supermassive black hole much larger than expected at such an early stage in the Universe's history, though this is not the first distant quasar to offer such a challenge.
- Bañados, Eduardo; et al. (6 December 2017). "An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5". Nature. 553 (7689): 473–476. arXiv:1712.01860. Bibcode:2018Natur.553..473B. doi:10.1038/nature25180. PMID 29211709.
- Venemans, Bram P.; et al. (6 December 2017). "Copious Amounts of Dust and Gas in a z = 7.5 Quasar Host Galaxy". The Astrophysical Journal Letters. 851 (1): L8. doi:10.3847/2041-8213/aa943a. hdl:10150/626419.
- Staff. "Finding the constellation which contains given sky coordinates". djm.com. Retrieved 6 December 2017.
- Choi, Charles Q. (6 December 2017). "Oldest Monster Black Hole Ever Found Is 800 Million Times More Massive Than the Sun". Space.com. Retrieved 6 December 2017.
- Landau, Elizabeth; Bañados, Eduardo (6 December 2017). "Found: Most Distant Black Hole". NASA. Retrieved 6 December 2017.
"This black hole grew far larger than we expected in only 690 million years after the Big Bang, which challenges our theories about how black holes form," said study co-author Daniel Stern of NASA's Jet Propulsion Laboratory in Pasadena, California.
- Decarli, Roberto; et al. (September 2017). "Rest-frame optical photometry of a z-7.54 quasar and its environment". CalTech. Retrieved 6 December 2017.
- Grush, Loren (6 December 2017). "The most distant supermassive black hole ever found holds secrets to the early Universe - We're seeing how it looked when the Universe was a toddler". TheVerge. Retrieved 6 December 2017.
- Bañados, Eduardo (2017). "Eduardo Bañados - Bio/CV". Carnegie Institution for Science. Retrieved 7 December 2017.
- Matson, John (29 June 2011). "Brilliant, but Distant: Most Far-Flung Known Quasar Offers Glimpse into Early Universe". Scientific American. Retrieved 7 December 2017.
- Willott, C. (2011). "Cosmology: A monster in the early Universe". Nature. 474 (7353): 583–584. arXiv:1106.6090. Bibcode:2011Natur.474..583W. doi:10.1038/474583a. PMID 21720357.preprint of this paper
- Davide Castelvecchi (25 February 2015). "Young black hole had monstrous growth spurt". Nature. Retrieved 9 December 2017.
A black hole that grew to gargantuan size in the Universe's first billion years is by far the largest yet spotted from such an early date, researchers have announced. The object, discovered by astronomers in 2013, is 12 billion times as massive as the Sun, and six times greater than its largest-known contemporaries. Its existence poses a challenge for theories of the evolution of black holes, stars and galaxies, astronomers say. Light from the black hole took 12.9 billion years to reach Earth, so astronomers see the object as it was 900 million years after the Big Bang. That “is actually a very short time” for a black hole to have grown so large, says astronomer Xue-Bing Wu of Peking University in Beijing.
- "Discovery in the early universe poses black hole growth puzzle". Phys.org. 11 May 2015. Retrieved 9 December 2017.
Now, researchers from the Max Planck Institute for Astronomy (MPIA) have discovered three quasars that challenge conventional wisdom on black hole growth. These quasars are extremely massive, but should not have had sufficient time to collect all that mass. The astronomers observed quasars whose light took nearly 13 billion years to reach Earth. In consequence, the observations show these quasars not as they are today, but as they were almost 13 billion years ago, less than a billion years after the big bang. The quasars in question have about a billion times the mass of the sun. All current theories of black hole growth postulate that, in order to grow that massive, the black holes would have needed to collect infalling matter, and shine brightly as quasars, for at least a hundred million years. But these three quasars proved to be have been active for a much shorter time, less than 100,000 years. "This is a surprising result," explains Christina Eilers, a doctoral student at MPIA and lead author of the present study. "We don't understand how these young quasars could have grown the supermassive black holes that power them in such a short time."
| Most distant known quasar | 0.854117 | 3.778046 |
The search for life elsewhere has long focused on what we are most familiar with on Earth – in other words, “life as we know it,” or organisms which are carbon-based and require water to survive. However, a growing number of scientists are now thinking that alternative forms of life are possible, ones which have never been seen on Earth, but could flourish in other types of alien environments. A new study from Cornell University addresses this very question, demonstrating a form of microscopic life which would be possible on Saturn’s largest moon Titan.
Liquid water is essential to life on Earth; Titan also has large bodies of liquid on its surface, but they are composed of methane/ethane instead of water. At the extremely cold temperatures on Titan’s surface, water can only exist as rock-hard ice. It has long been thought that life would be impossible under those conditions, but new research is showing that alternative forms of biology could actually thrive. These putative lifeforms would be methane-based, oxygen-free cells which could metabolize and reproduce just like their carbon-based counterparts. The cell membrane would be composed of small organic nitrogen compounds and capable of functioning in liquid methane temperatures of 292 degrees below zero.
The new study is led by chemical molecular dynamics expert Paulette Clancy, the Samuel W. and Diane M. Bodman Professor of Chemical and Biomolecular Engineering at Cornell. The co-author of the new paper is Jonathan Lunine, the David C. Duncan Professor in the Physical Sciences in the College of Arts and Sciences’ Department of Astronomy.
“We’re not biologists, and we’re not astronomers, but we had the right tools,” Clancy said. “Perhaps it helped, because we didn’t come in with any preconceptions about what should be in a membrane and what shouldn’t. We just worked with the compounds that we knew were there and asked, ‘If this was your palette, what can you make out of that?’”
Lunine is, however, an expert on Saturn’s moons and an interdisciplinary scientist for the Cassini-Huygens mission which is still orbiting Saturn.
The team wanted to know what kind of organism could possibly exist in Titan’s methane seas and lakes. They came up with the azotosome (“nitrogen body”), a theoretical cell membrane which would be based on methane instead of water. Life on Earth is based on the water-based phospholipid bilayer membrane which contains the organic matter of every cell. A vesicle made from this type of membrane is called a liposome. Such an azotosome would be composed of nitrogen, carbon, and hydrogen molecules, all of which are already known to exist in Titan’s seas and lakes. Surprisingly, they showed the same flexibility and stability as liposomes on Earth. A form of life which mimics cells on Earth, but in a very alien kind of environment. Even the extreme cold isn’t a problem, as these azotosomes are well suited to survive in it.
The team also searched for candidate compounds from methane which could assemble themselves into membrane-like structures. An acrylonitrile azotosome seemed to be the best candidate, since it showed good stability, a strong barrier to decomposition, and a flexibility similar to that of phospholipid membranes on Earth. Acrylonitrile is also already known to exist in Titan’s atmosphere.
Now that the team has shown that such cell structures could theoretically exist on Titan, the next step is to figure out how metabolism and reproduction might occur. As do many others, Lunine would like to investigate this directly on Titan itself, by sending another mission to explore Titan’s seas, “someday sending a probe to float on the seas of this amazing moon and directly sampling the organics.”
From the paper:
“The availability of molecules with an ability to form cell membranes does not by itself demonstrate that life is possible. However, it does direct our search for exotic metabolic and reproductive chemistries that would be similarly compatible under cryogenic conditions. As our understanding of conditions that could nurture extraterrestrial life expands, so does our probability of finding it, perhaps within the liquid methane habitable zone.”
The findings are an exciting example of how life elsewhere may have evolved and adapted to environments very different to those on Earth. As paper co-author James Stevenson, a graduate student in chemical engineering, stated, “Ours is the first concrete blueprint of life not as we know it.” Stevenson was inspired by science fiction writer Isaac Asimov, who wrote about the concept of non-water-based life in his 1962 essay, “Not as We Know It.”
Along with Europa and Enceladus, which both have liquid water oceans beneath surface crusts of ice, Titan may turn out to be another good place to search for life elsewhere in the solar system.
The new paper is available here in Science Advances.
This article was first published on AmericaSpace. | 0.853916 | 3.674762 |
About this Research Topic
For more than half a century, scientific space missions have provided the experimental underpinning for advances in space plasma physics. In-situ and remote observations have revealed an incredible variety of processes throughout the heliosphere and beyond, including the solar corona, solar wind, planetary magnetospheres, and local interstellar medium. These range from large-scale and transient heliospheric structures to common plasma processes, such as turbulence, instabilities, particle acceleration, reconnection, waves, shocks, dissipation. These phenomena have been widely studied but remain to be fully understood, both in their fundamental nature and in the role that they play in our heliosphere.
Each new mission so far has answered many questions and changed our perspective, driving forward our understanding of space plasmas, but has also given rise to many new questions about how our solar system works. Recent examples are the NASA missions MMS and Parker Solar Probe; the variety of new phenomena discovered and their complex nature has stimulated much interest and activity within the community while raising new fundamental questions about space plasmas. While awaiting new insights from the recently launched ESA spacecraft Solar Orbiter and Bepi Colombo, many in the community are working on innovative concepts for future space missions, both in response to theoretical and numerical advances and also in light of the most recent observations. Recently, the European Space Agency launched its long-term planning exercise, Voyage 2050, with a call for white papers. In the USA, the NASA/NSF/NOAA Heliophysics 2050 exercise is taking place to examine the long-term goals for the community.
This Research Topic, open for submissions in both Frontiers in Astronomy and Space Sciences and Frontiers in Physics, aims at collecting innovative ideas, white papers and recent results suggesting the need for innovative space measurements. These should be presented as Perspective, Review, Mini Review, Methods, Specialty Grand Challenge, Technology and Code, Brief Research Report, Opinion or Original Research papers, demonstrating the current and future open challenges in space plasma physics, and the proposed approaches to address them.
Keywords: Space plasmas, Heliosphere, Space missions, Experimental space plasmas, Challenges
Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review. | 0.841743 | 3.055681 |
Martian Meteorite Almost 4 Billion Years Younger Than Previously Thought
A team of researchers has revealed that a common group of meteorites from Mars is almost 4 billion years younger than previously thought, providing scientists with a clearer picture of the Red Planet’s evolution.
A team led by Western University’s Desmond Moser has solved a Martian meteorite age puzzle that paints a much clearer picture of the Red Planet’s evolution that can now be compared to habitable Earth.
By directing energy beams at tiny crystals found in a Martian meteorite, a Western University-led team of geologists has proved that the most common group of meteorites from Mars is almost 4 billion years younger than many scientists had believed – resolving a long-standing puzzle in Martian science and painting a much clearer picture of the Red Planet’s evolution that can now be compared to that of habitable Earth.
In a paper published today in the journal Nature, lead author Desmond Moser, an Earth Sciences professor from Western’s Faculty of Science, Kim Tait, Curator, Mineralogy, Royal Ontario Museum, and a team of Canadian, U.S., and British collaborators show that a representative meteorite from the Royal Ontario Museum (ROM)’s growing Martian meteorite collection, started as a 200 million-year-old lava flow on Mars, and contains an ancient chemical signature indicating a hidden layer deep beneath the surface that is almost as old as the solar system.
The team, comprised of scientists from ROM, the University of Wyoming, UCLA, and the University of Portsmouth, also discovered crystals that grew while the meteorite was launched from Mars towards Earth, allowing them to narrow down the timing to less than 20 million years ago while also identifying possible launch locations on the flanks of the supervolcanoes at the Martian equator.
More details can be found in their paper titled, “Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon.”
Moser and his group at Western’s Zircon & Accessory Phase Laboratory (ZAPLab), one of the few electron nanobeam dating facilities in the world, determined the growth history of crystals on a polished surface of the meteorite. The researchers combined a long-established dating method (measuring radioactive uranium/lead isotopes) with a recently developed gently-destructive, mineral grain-scale technique at UCLA that liberates atoms from the crystal surface using a focused beam of oxygen ions.
Moser estimates that there are roughly 60 Mars rocks dislodged by meteorite impacts that are now on Earth and available for study, and that his group’s approach can be used on these and a much wider range of heavenly bodies.
“Basically, the inner solar system is our oyster. We have hundreds of meteorites that we can apply this technique to, including asteroids from beyond Mars to samples from the Moon,” says Moser, who credits the generosity of the collectors that identify this material and make it available for public research.
Publication: D. E. Moser, et al., “Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon,” Nature 499, 454–457, 25 July 2013; doi:10.1038/nature12341
Image: Western University
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- Astronomers Discover a Probable Free-Floating Planet, CFBDSIR2149
- Backyard Worlds Planet 9 Citizen Science Project Discovers a Brown Dwarf | 0.848661 | 3.601807 |
Star spotted with spirograph orbit around supermassive black hole
In space, most orbiting objects will have circular- or elliptical-shaped orbits. But now, almost 30 years of observations has revealed that a star in the center of our galaxy orbits the supermassive black hole Sagittarius A* (Sgr A*) in a rosette, or spirograph shape. The find once again confirms a prediction made by Einstein’s General Relativity.
If you were to look down at the “plane” of the planets orbiting the Sun, their paths would mostly appear as a series of irregular circles. Sure, Earth’s orbit wobbles from an almost perfect circle to more egg-shaped over 100,000 years or so, but it still centers on the Sun.
But things are very different for S2. This star orbits the supermassive black hole at the heart of the Milky Way on an oval-shaped path – but the oval isn’t centered on the black hole. Instead, it’s located at one end. Thanks to the extremely powerful gravitational pull of Sgr A*, S2 speeds up as it falls towards the black hole, before it’s slingshotted away, slows back down, and is eventually pulled back towards the black hole.
Astronomers have been studying S2 for decades, and its unusual orbit was actually one of the first compelling pieces of evidence that there is a supermassive black hole at the center of the Milky Way.
And now, scientists have found an even stranger aspect of this star’ orbit. The ellipsis isn’t the same every time – the intense gravity throws S2 off in a slightly different direction every time. The path shifts forwards, and then next time it loops back around it shifts again. Over many iterations the star’s orbit comes to resemble a rosette or a spirograph. This phenomenon is known as Schwarzchild precession, and this was the first time it had been seen in a star orbiting a black hole.
It took a long time to make these observations however – S2 takes 16 years to complete one lap around Sgr A*. To confirm that its orbit was on a precession, astronomers had to watch it for 27 years, making over 330 measurements of the star’s position and velocity. This was done using multiple instruments on the Very Large Telescope (VLT) in Chile.
Interestingly, the team says that this observation once again confirms elements of Einstein’s Theory of General Relativity. At the same time it also gives new evidence of the properties of Sgr A* and the environment around it.
“Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*,” say Guy Perrin and Karine Perraut, lead scientists on the project. “This is of great interest for understanding the formation and evolution of supermassive black holes.”
The research was published in the journal Astronomy & Astrophysics. An animation of S2’s odd orbit can be seen in the video below.
Source: European Southern Observatory | 0.878314 | 3.92383 |
It might sound like science fiction, but we already know how to make objects move at near light speed. Physicists do it all the time inside particle accelerators, where they accelerate particles to relativistic speeds just a small fraction below the speed of light (about 186,000 miles per second).
But when we try to reach these speeds on a macro scale, we run into all kinds of problems. Things like spacecraft are really heavy, especially when they're loaded down with fuel for long trips, and it's difficult to accelerate them to really fast speeds.
Now researchers are saying a new kind of laser-based propulsion would eliminate the need for fuel and could accelerate spacecraft up to 26% of the speed of light. At that blistering pace, a tiny space probe could get to Mars in just 30 minutes. And it could travel four light years to our nearest star, Alpha Centauri, in just 15 years.
Researchers say eventually, with a scaled up version of laser propulsion, a full-sized, 100-kilogram spacecraft could get to Mars in just a few days.
For comparison, right now it takes around four to eight months to get to Mars with our current technology. It took 35 years for the Voyager 1 spacecraft to reach the edge of our solar system. It's only traveling at about 0.006% of the speed of light, according to Popular Science.
If we ever want to become interstellar travelers, that sluggish speed simply won't cut it.
"As remarkable as this [is,] we will never reach even the nearest stars with our current propulsion technology in even 10 millennium," Philip Lubin, a cosmologist at the University of California Santa Barbara, writes in a paper titled "A Roadmap to Interstellar Flight."
So Lubin has proposed a laser system called photonic propulsion, in which spacecraft equipped with giant laser sails could be pushed along to increasing speeds with a powerful laser.
But instead of relying on one giant, ultra-powerful laser like the one on the Death Star, which are too impractical to build, Lubin is proposing a series of laser amplifiers that can sync up multiple lasers and combine them into one powerful beam.
The good news, Lubin notes, is that all of this technology already exists. We just need to start testing and developing it.
"There is no known reason why we cannot do this," Lubin says in a video explanation of laser propulsion.
Right now we have laser amplifiers about the size of a textbook, but Lubin thinks a 6-square-mile array of lasers and amplifiers floating out in Earth orbit would be powerful enough to beam a gram-sized spacecraft to Alpha Centauri in 15 years. But it would still take 2,200 years to send a full-sized and fully loaded space shuttle that far, so we'd eventually need an even larger laser array, according to Popular Science.
Luckily, Lubin says the design is easily scalable.
This all sounds incredible, but the researchers have a really big problem to solve first: braking. Currently there's no way to slow down one of these spacecraft once it approaches relativistic speeds. So for now if we sent a laser-propelled probe to a distant world, it could only snap a few photos and take some preliminary data measurements as it goes flying by.
But interstellar travel isn't the only thing this laser array could do. Lubin says it might be able to protect us from asteroids and space debris.
For now the researchers don't have plans to build any of the giant arrays that would be capable of beaming a spacecraft to Mars in a few days. They'll be testing the system on a smaller scale, and hopefully we'll be able to start sending teeny-tiny space probes out to explore the universe around us.
You can hear Lubin describe photonic propulsion in the video below:
h/t Popular Science | 0.843121 | 3.782456 |
Solar System, technical/Saturn
The 6th planet Saturn is first recorded around 1610 by Galileo and is most widely recognised by it's icy rings. It has an atmosphere which is rich in both Hydrogen and Helium. Over 24 moons and satellite bodies orbit the planet of which Titan is the largest with an atmospheric pressure on the surface 50% greater than that on Earth.
With an average density lower than water Saturn is unlikely to contain any solid surface under it's hazy exterior.
- C ring - Innermost ring, dark in colour. Also called the Crepe ring.
- B ring - Between the C ring and Cassini's division.
- A ring - The large ring between the Cassini division and the Enke division
- G ring - Outermost ring, quite thin.
The gaps between the rings are formed in some cases due to resonances with moons or confined by shepherd satellites which gravitationally tug straying particles back into the rings. There are not enough moons to fully account for all the ringlets hence it is believed that gravitational / spiral waves are to account for them (akin to the spiral density waves in galaxies).
Studied briefly by a Pioneer mission it has been much more extensively studied by the Cassini mission since the spacecraft arrived in 2004.
- Average distance from sun: 9.5388 AU (14.27 x 10^8km)
- Average orbital velocity: 9.64 km/s
- Orbital period: 29.461 years (10,760 days)
- Rotation period: 10h 39m 25s
- Average density: 0.69 g/cm^3
- Gravity at base of clouds: 1.16 G
- Temperature at cloud tops: -180 C (-292 F)
"The upper clouds are composed of ammonia crystals"
"In 1990, the Hubble Space Telescope imaged an enormous white cloud near Saturn's equator that was not present during the Voyager encounters and in 1994, another, smaller storm was observed. The 1990 storm was an example of a Great White Spot, a unique but short-lived phenomenon that occurs once every Saturnian year, roughly every 30 Earth years, around the time of the northern hemisphere's summer solstice. Previous Great White Spots were observed in 1876, 1903, 1933 and 1960, with the 1933 storm being the most famous. If the periodicity is maintained, another storm will occur in about 2020."
"Infrared imaging has shown that Saturn's south pole has a warm polar vortex, the only known example of such a phenomenon in the Solar System. Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, believed to be the warmest spot on Saturn."
The second image at left is Saturn's atmosphere and its rings shown "in a false color composite made from Cassini images taken in near infrared light through filters that sense different amounts of methane gas. Portions of the atmosphere with a large abundance of methane above the clouds are red, indicating clouds that are deep in the atmosphere. Grey indicates high clouds and brown indicates clouds at intermediate altitudes. The rings are bright blue because there is no methane gas between the ring particles and the camera."
"A large, bright and complex convective storm that appeared in Saturn's southern hemisphere in mid-September 2004 was the key in solving a long-standing mystery about the ringed planet."
"The complex feature with arms and secondary extensions just above and to the right of center is called the Dragon Storm. It lies in a region of the southern hemisphere referred to as "storm alley" by imaging scientists because of the high level of storm activity observed there by Cassini in the last year."
"Dragon Storm (dubbed so in September 2004 because of its unusual shape) is a large, bright and complex convective storm in Saturn's southern hemisphere. The Saturnian storm appears to be long-lived and periodically flares up to produce dramatic white plumes which then subside. The storm is a strong source of radio emissions."
The X-ray astronomy image of Saturn is on the left in the composite at right. The Chandra X-ray Observatory "image of Saturn held some surprises for the observers. First, Saturn's 90 megawatts of X-radiation is concentrated near the equator. This is different from a similar gaseous giant planet, Jupiter, where the most intense X-rays are associated with the strong magnetic field near its poles. Saturn's X-ray spectrum, or the distribution of its X-rays according to energy, was found to be similar to that of X-rays from the Sun. This indicates that Saturn's X-radiation is due to the reflection of solar X-rays by Saturn's atmosphere. The intensity of these reflected X-rays was unexpectedly strong. ... The optical image of Saturn is also due to the reflection of light from the Sun - visible wavelength light in this case - but the optical and X-ray images obviously have dramatic differences. The optical image is much brighter, and shows the beautiful ring structures, which were not detected in X-rays. This is because the Sun emits about a million times more power in visible light than in X-rays, and X-rays reflect much less efficiently from Saturn's atmosphere and rings."
"One of a series, this image [at right] of Saturn was taken when the planet's rings were at their maximum tilt of 27 degrees toward Earth. Saturn experiences seasonal tilts away from and toward the sun, much the same way Earth does. This happens over the course of its 29.5-year orbit. Every 30 years, Earth observers can catch their best glimpse of Saturn's south pole and the southern side of the planet's rings. ... NASA's Hubble Space Telescope [captured detailed images of Saturn's Southern Hemisphere and the southern face of its rings."
The movie at right records Saturn "when its rings were edge-on, resulting in a unique movie featuring the nearly symmetrical light show at both of the giant planet's poles. It takes Saturn almost thirty years to orbit the Sun, with the opportunity to image both of its poles occurring only twice during that time. The light shows, called aurorae, are produced when electrically charged particles race along the planet's magnetic field and into the upper atmosphere where they excite atmospheric gases, causing them to glow. Saturn's aurorae resemble the same phenomena that take place at the Earth's poles."
"Powered by the Saturnian equivalent of (filamentary) Birkeland currents, streams of charged particles from the interplanetary medium interact with the planet's magnetic field and funnel down to the poles. Double layers are associated with (filamentary) currents, and their electric fields accelerate ions and electrons."
"Towering more than 1,000 miles above the cloud tops, these Saturnian auroral displays are analogous to Earth's. ... In this false color image, the dramatic red aurora identify emission from atomic hydrogen, while the more concentrated white areas are due to hydrogen molecules."
"The best view of Saturn's rings in the ultraviolet indicates there is more ice toward the outer part of the rings, than in the inner part, hinting at the origins of the rings and their evolution."
"Images taken during the Cassini spacecraft's orbital insertion on June 30 show compositional variation in the A, B and C rings. From the inside out, the "Cassini Division" in faint red at left is followed by the A ring in its entirety. The Cassini Division at left contains thinner, dirtier rings than the turquoise A ring, indicating a more icy composition. The red band roughly three-fourths of the way outward in the A ring is known as the Encke gap."
"The ring system begins from the inside out with the D, C, B and A rings followed by the F, G and E rings. The red in the image indicates sparser ringlets likely made of "dirty," and possibly smaller, particles than in the icier turquoise ringlets."
The image at right "was taken with the Ultraviolet Imaging Spectrograph instrument, which is capable of resolving the rings to show features up to 97 kilometers (60 miles) across, roughly 100 times the resolution of ultraviolet data obtained by the Voyager 2 spacecraft."
"The north polar region of Saturn is pictured in great detail in this Voyager 2 image obtained Aug. 25 from a range of 633,000 kilometers (393,000 miles)."
"Two oval cloud systems some 250 km (150 mi) across are visible at about 72 degrees north latitude. The bright spot in the center of the leftmost cloud is a convective cloud storm about 60 km. (37 mi.)across. The outer ring of material rotates in an anti-cyclonic sense(counterclockwise in the northern hemisphere). A similar cloud structure of comparable dimension appears at 55 degrees north (bottom center of this picture). These northern latitudes contain many bright, small-scale cloud spots--only a few tens of kilometers across--representative of convective cloud systems. Across the top of this image stretch several long, linear, wavelike features that may mark the northernmost east-flowing jet in Saturn's atmosphere."
"In this orange-and-violet-image composite, the smallest features visible are about 16 km. (10 mi.) across."
In the second image at right, "[t]he gas planet's subtle northward gradation from gold to azure is a striking visual effect that scientists don't fully understand. Current thinking says that it may be related to seasonal influences, tied to the cold temperatures in the northern (winter) hemisphere. Despite Cassini's revelations, Saturn remains a world of mystery."
In the image at right, "Mimas drifts along in its orbit against the azure backdrop of Saturn's northern latitudes in this true color view from NASA's Cassini spacecraft. The long, dark lines on the atmosphere are shadows cast by the planet's rings."
"Saturn's northern hemisphere is presently relatively cloud-free, and rays of sunlight take a long path through the atmosphere. This results in sunlight being scattered at shorter (bluer) wavelengths, thus giving the northernmost latitudes their bluish appearance at visible wavelengths."
At right is an infrared astronomy image of Saturn. "This is the sharpest image of Saturn's temperature emissions taken from the ground; it is a mosaic of 35 individual exposures made at the W.M. Keck I Observatory, Mauna Kea, Hawaii on Feb. 4, 2004. The images to create this mosaic were taken with infrared radiation. The black square at 4 o'clock represents missing data."
"In the most precise reading of Saturn's temperatures ever taken from Earth, a new set of infrared images suggests a warm "polar vortex" at Saturn's south pole - the first warm polar cap ever to be discovered in the solar system. The vortex is punctuated by a compact spot that is the warmest place on the planet."
"The puzzle isn't that Saturn's south pole is warm; after all, it has been exposed to 15 years of continuous sunlight, having just reached its summer Solstice late in 2002. But both the distinct boundary of a warm polar vortex some 30 degrees latitude from the southern pole and a very hot "tip" right at the pole were completely unexpected. If the increased southern temperatures are the result of the seasonal variations of sunlight, then temperatures should increase gradually with increasing latitude. But they don't – the tropospheric temperature increases toward the pole abruptly near 70 degrees latitude from 88 to 89 Kelvin (- 301 to -299 degrees Fahrenheit) and then to 91 Kelvin (-296 degrees Fahrenheit) right at the pole. Near 70 degrees latitude, the stratospheric temperature increases even more abruptly from 146 to 150 Kelvin (-197 to -189 degrees Fahrenheit) and then again to 151 Kelvin (-188 degrees Fahrenheit) right at the pole."
The second image at right is "constructed from data collected in the near-infrared wavelengths of light, the auroral emission is shown in green. The data represents emissions from hydrogen ions in of light between 3 and 4 microns in wavelength. In general, scientists designated blue to indicate sunlight reflected at a wavelength of 2 microns, green to indicate sunlight reflected at 3 microns and red to indicate thermal emission at 5 microns. Saturn's rings reflect sunlight at 2 microns, but not at 3 and 5 microns, so they appear deep blue. Saturn's high altitude haze reflects sunlight at both 2 and 3 microns, but not at 5 microns, and so it appears green to blue-green. The heat emission from the interior of Saturn is only seen at 5 microns wavelength in the spectrometer data, and thus appears red. The dark spots and banded features in the image are clouds and small storms that outline the deeper weather systems and circulation patterns of the planet. They are illuminated from underneath by Saturn's thermal emission, and thus appear in silhouette. The composite image was made from 65 individual observations by Cassini's visual and infrared mapping spectrometer on 1 November 2008. The observations were each six minutes long."
The third image at right shows Saturn's northern polar region with "the aurora and underlying atmosphere, seen at two different wavelengths of infrared light as captured by NASA's Cassini spacecraft. Energetic particles, crashing into the upper atmosphere cause the aurora, shown in blue, to glow brightly at 4 microns (six times the wavelength visible to the human eye). The image shows both a bright ring, as seen from Earth, as well as an example of bright auroral emission within the polar cap that had been undetected until the advent of Cassini. This aurora, which defies past predictions of what was expected, has been observed to grow even brighter than is shown here. Silhouetted by the glow (cast here to the color red) of the hot interior of Saturn (clearly seen at a wavelength of 5 microns, or seven times the wavelength visible to the human eye) are the clouds and haze that underlie this auroral region."
Also on the right is a fourth image of Saturn's north polar region in infrared. "This striking false-color mosaic was created from 25 images taken by Cassini's visual and infrared mapping spectrometer over a period of 13 hours, and captures Saturn in nighttime and daytime conditions. The visual and infrared mapping spectrometer acquires data simultaneously at 352 different wavelengths, or spectral channels. Data at wavelengths of 2.3, 3.0 and 5.1 microns were combined in the blue, green and red channels of a standard color image, respectively, to make this false-color mosaic."
"This image was acquired on 24 February 2007, while the spacecraft was 1.58 million km (1 million miles) from the planet and 34.6 degrees above the ring plane. The solar phase angle was 69.5 degrees. In this view, Cassini was looking down on the northern, unlit side of the rings, which are rendered visible by sunlight filtering through from the sunlit, southern face."
"On the night side (right side of image), with no sunlight, Saturn's own thermal radiation lights things up. This light at 5.1 microns wavelength (some seven times the longest wavelength visible to the human eye) is generated deep within Saturn, and works its way upward, eventually escaping into space. Thick clouds deep in the atmosphere block that light. An amazing array of dark streaks, spots and globe-encircling bands is visible instead. Saturn's strong thermal glow at 5.1 microns even allows these deep clouds to be seen on portions of the dayside (left side), especially where overlying hazes are thin and the glint of the sun off of them is minimal. These deep clouds are likely made of ammonium hydrosulfide and cannot be seen in reflected light on the dayside, since the glint of the sun on overlying hazes and ammonia clouds blocks the view of this level."
"A pronounced difference in the brightness between the northern and southern hemispheres is apparent. The northern hemisphere is about twice as bright as the southern hemisphere. This is because high-level, fine particles are about half as prevalent in the northern hemisphere as in the south. These particles block Saturn's glow more strongly, making Saturn look brighter in the north."
"At 2.3 microns (shown in blue), the icy ring particles are highly reflecting, while methane gas in Saturn's atmosphere strongly absorbs sunlight and renders the planet very dark. At 3.0 microns (shown in green), the situation is reversed: water ice in the rings is strongly absorbing, while the planet's sunlit hemisphere is bright. Thus the rings appear blue in this representation, while the sunlit side of Saturn is greenish-yellow in color. Within the rings, the most opaque parts appear dark, while the more translucent regions are brighter. In particular, the opaque, normally-bright B ring appears here as a broad, dark band separating the brighter A (outer) and C (inner) rings."
"At 5.1 microns (shown in red), reflected sunlight is weak and thus light from the planet is dominated by thermal (i.e., heat) radiation that wells up from the planet's deep atmosphere. This thermal emission dominates Saturn's dark side as well as the north polar region (where the hexagon is again visible) and the shadow cast by the A and B rings. Variable amounts of clouds in the planet's upper atmosphere block the thermal radiation, leading to a speckled and banded appearance, which is ever-shifting due to the planet's strong winds."
The fifth infrared image of Saturn is a detailed false color image. "[T]aken in January 1998 by the Hubble Space Telescope [it] shows the ringed planet in reflected infrared light. Different colors [indicate] varying heights and compositions of cloud layers generally thought to consist of ammonia ice crystals. The eye-catching rings cast a shadow on Saturn's upper hemisphere, while the bright stripe seen within the left portion of the shadow is infrared sunlight streaming through the large gap in the rings known as the Cassini Division."
"Two of Saturn's many moons have also put in an appearance (in the full resolution version), Tethys just beyond the planet's disk at the upper right, and Dione at the lower left."
The panoramic images at right "from NASA's Cassini spacecraft chronicle a day in the life of a huge storm that developed from a small spot that appeared 12 weeks earlier in Saturn's northern mid-latitudes."
"This storm is the largest and most intense observed on Saturn by NASA's Voyager or Cassini spacecraft. The storm is still active. As seen in these and other Cassini images, the storm encircles the planet - whose circumference at these latitudes is 300,000 kilometres. From north to south, it covers a distance of about 15,000 kilometres, which is one-third of the way around the Earth. It encompasses an area of 4 billion square kilometres, or eight times the surface area of Earth. This storm is about 500 times the area of the biggest of the southern hemisphere storms ... observed by Cassini."
"The highest clouds in the image are probably around 100 millibars pressure, 100 kilometres above the regular undisturbed clouds. These false colors show clouds at different altitudes. Clouds that appear blue here are the highest and are semitransparent, or optically thin. Those that are yellow and white are optically thick clouds at high altitudes. Those shown green are intermediate clouds. Red and brown colors are clouds at low altitude unobscured by high clouds, and the deep blue color is a thin haze with no clouds below. The base of the clouds, where lightning is generated, is probably in the water cloud layer of Saturn's atmosphere. The storm clouds are likely made out of water ice covered by crystallized ammonia."
"Taken about 11 hours -- or one Saturn day -- apart, the two mosaics in the lower half of this image product consist of 84 images each. The mosaic in the middle was taken earlier than the mosaic at the bottom. Both mosaics were captured on Feb. 26, 2011, and each of the two batches of images was taken over about 4.5 hours."
"Two enlargements from the earlier, middle mosaic are shown at the top of this product. The white lines below the middle mosaic identify those parts of the mosaic that were enlarged for these close-up views. The enlargement on the top left shows the head of the storm, and that on the top right shows the turbulent middle of the storm. Cassini observations have shown the head of the storm drifting west at a rate of about 2.8 degrees of longitude each Earth day (28 meters per second, or 63 miles per hour). The central latitude of the storm is the site of a westward jet, which means that the clouds to the north and south are drifting westward more slowly or even drifting eastward. In contrast, clouds at Saturn's equator drift eastward at speeds up to 450 meters per second (1,000 miles per hour). "
"Both of the long mosaics cover an area ranging from about 30 degrees north latitude to 51 degrees north latitude. The views stretch from about 138 degrees west longitude on the left to 347 degrees west longitude on the right, passing through 360/0 degrees west longitude near the far right of the mosaics."
"The images were taken with the Cassini spacecraft narrow-angle camera using a combination of spectral filters sensitive to wavelengths of near-infrared light. The images filtered at 889 nanometers are projected as blue. The images filtered at 727 nanometers are projected as green, and images filtered at 750 nanometers are projected as red."
"The views were acquired at a distance of approximately 2.4 million kilometres from Saturn and at a sun-Saturn-spacecraft angle (phase angle) of 62 degrees. Both the top and bottom images are simple cylindrical map projections, defined such that a square pixel subtends equal intervals of latitude and longitude. At higher latitudes, the pixel size in the north-south direction remains the same, but the pixel size in the east-west direction becomes smaller. The pixel size is set at the equator, where the distances along the sides are equal. The images of the long mosaics have a pixel size of 53 kilometres at the equator, and the two close-up views have a pixel size of 9 kilometres per pixel at the equator."
"[T]he PH3 1-0 rotational line (266.9 GHz) line [has been detected] in [the atmosphere of] Saturn".
"Three simultaneous radio signals at wavelengths of 0.94, 3.6, and 13 centimeters (Ka-, X-, and S-bands) were sent from Cassini through the rings to Earth. The observed change of each signal as Cassini moved behind the rings provided a profile of the distribution of ring material and an optical depth profile."
"This simulated image was constructed from the measured optical depth profiles of the Cassini Division and ring A. It depicts the observed structure at about 10 kilometers (6 miles) in resolution. The image shows the same ring A region depicted in a similar image (Multiple Eyes of Cassini), using a different color scheme to enhance the view of a remarkable array of over 40 wavy features called 'density waves' uncovered in the May 3 radio occultation throughout ring A."
"Color is used to represent information about ring particle sizes based on the measured effects of the three radio signals. Shades of red [purple] indicate regions where there is a lack of particles less than 5 centimeters (about 2 inches) in diameter. Green and blue shades indicate regions where there are particles of sizes smaller than 5 centimeters (2 inches) and 1 centimeter (less than one third of an inch), respectively."
"Note the gradual increase in shades of green towards the outer edge of ring A. It indicates gradual increase in the abundance of 5-centimeter (2-inch) and smaller particles. Note also the blue shades in the vicinity of the Keeler gap (the narrow dark band near the edge of ring A). They indicate increased abundance of even smaller particles of diameter less than a centimeter. Frequent collisions between large ring particles in this dynamically active region likely fragment the larger particles into more numerous smaller ones."
"The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. ... [Its] exterior is predominantly composed of gas and it lacks a definite surface ... The planet primarily consists of hydrogen ... The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium. ... The proportion of helium is significantly deficient compared to the abundance of this element in the Sun. ... Trace amounts of ammonia, acetylene, ethane, propane, phosphine and methane have been detected in Saturn's atmosphere."
"Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. [It is n]amed after the Roman god Saturn ... Saturn is a gas giant with an average radius about nine times that of Earth. ... Saturn has a ring system that consists of nine continuous main rings and three discontinuous arcs, composed mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-two known moons orbit the planet; fifty-three are officially named. This does not include the hundreds of "moonlets" within the rings."
"Saturday is the day of Saturn, and the color of Saturn, according to astronomers, is said to be black".
Apparently 5102 b2k (before the year 2000.0), -3102 or 3102 BC, is the historical year assigned to a Hindu table of planets that does include the classical planet Saturn. "Babylonian astronomy, too, had a four-planet system. In ancient prayers the planets Saturn, Jupiter, Mars, and Mercury are invoked; ... and one speaks of "the four-planet system of the ancient astronomers of Babylonia.""
Anu may be an early Sumerian, Akkadian, and Babylonian name for Saturn.
"An, the oldest and highest of the Sumero-Babylonian gods, whose primordial age was "the year of abundance," signified Saturn, according to Jensen.6"
"The potential cruelty of Saturn was enhanced by his identification with Cronus, known for devouring his own children. He was thus equated with the Carthaginian god Ba'al Hammon, to whom children were supposedly sacrificed. Saturn was also among the gods the Romans equated with Yahweh, whose Sabbath (on Saturday) he shared as his holy day."
"In the Canaanite religion, or Levantine religion as a whole, Ēl or Il was the supreme god, the father of humankind and all creatures and the husband of the goddess Asherah as recorded in the clay tablets of Ugarit ... The noun ʾēl was found at the top of a list of gods as the "Ancient of gods" or the "Father of all gods", in the ruins of the royal archive of the Ebla civilization, in the archaeological site of Tell Mardikh in Syria dated to 2300 BC."
"Osiris is the mythological father of the god Horus, whose conception is described in the Osiris myth, a central myth in ancient Egyptian belief. The myth described Osiris as having been killed by his brother Seth, who wanted Osiris' throne. Isis joined the fragmented pieces of Osiris, but the only body part missing was the phallus. Isis fashioned a golden phallus, and briefly brought Osiris back to life by use of a spell that she learned from her father. This spell gave her time to become pregnant by Osiris before he again died. Isis later gave birth to Horus. As such, since Horus was born after Osiris' resurrection, Horus became thought of as a representation of new beginnings and the vanquisher of the evil Set."
"The Phoenician El - Saturn - has four eyes, as does the Orphic Kronos (Saturn)."
"The Chinese Yellow Emperor Huang-ti--identified as Saturn--is also four-eyed.74"
"Osiris, as the Ram of Mendes, is the god of "four faces on one neck."62"
Have observers recorded images of sky entities in the green?
“The Latins considered Saturn the predecessor of Jupiter. Saturn reigned in Latium during a mythical Golden Age reenacted every year at the festival of Saturnalia. Saturn also retained primacy in matters of agriculture and money. Unlike the Greek tradition of Cronus and Zeus, the usurpation of Saturn as king of the gods by Jupiter was not viewed by the Latins as violent or hostile; Saturn continued to be revered in his temple at the foot of the Capitol Hill, which maintained the alternative name Saturnius into the time of Varro.”
"There is one God, greatest among gods and men, neither in shape nor in thought like unto mortals ... He abides ever in the same place motionless, and it befits him not to wander hither and thither."
"Saturn, the old man who lives at the north pole, and brings with him to the children of men a sprig of evergreen (the Christmas tree), is familiar to the little folks under the name Santa Claus, for he brings each winter the gift of a new year."
"The religions of all ancient nations ... associate the abode of the supreme God with the North Pole, the centre of heaven; or with the celestial space immediately surrounding it."
"Lenormant, speaking of Rome and Olympia, remarks, "It is impossible not to note that the Capitoline was first of all the Mount of Saturn, and that the Roman archaeologists established a complete affinity between the Capitoline and Mount Cronios in Olympia, from the standpoint of their traditions and religious origin (Dionysius Halicarn., i., 34). This Mount Cronios is, as it were, the Omphalos of the sacred city of Elis, the primitive centre of its worship. It sometimes receives the name Olympos."1 Here is not only symbolism in general, but also a symbolism pointing to the Arctic Eden, already shown to be the primeval mount of Kronos, the Omphalos of the whole earth.2"
"As an offshoot of these Hellenistic speculations we should place Tacitus, Histories V,2: "Iudaeos Creta insula profugos novissima Libyae insedisse memorant, qua tempestate Saturnus vi Jovis pulsus cesserit regnis" (quoted from Loeb Classical Library)." i.e., "Jews were fugitives from the island of Crete and settled in Libya recorded the time when Saturn was driven from his throne by force of Jupiter".
"The motif of Saturn handing over power to Jupiter derives, of course, from Hesiod's account of the succession of the gods in his Theogony, and his story of the five successive ages of men -- the first, or golden, age being under the reign of Kronos (Saturn) and the following ages being under the reign of Zeus (Jupiter) -- in his Works and Days (110ff.). These stories were often retold. Ovid, for example, combines in his Metamorphoses the stories in the Theogony and Works and Days, telling us how, "when Saturn was consigned to the darkness of Tartarus, and the world passed under the rule of Jove, the age of silver replaced that of gold."8"
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- Varro V 42; Vergil Aeneis VIII 357-8; Dionysius Hal. I 34; Solinus I 12; Festus p. 322 L; Tertullian Apologeticum 10; Macrobius I 7, 27 and I 10, 4 citing a certain Mallius. See also Macrobius I 7, 3: the annalistic tradition attributed its foundation to king Tullus Hostilius. Studies by E. Gjerstad in Mélanges Albert Grenier Bruxelles 1962 p. 757-762; Filippo Coarelli in La Parola del Passato 174 1977 p. 215 f.
- "Jupiter (mythology)". Wikipedia (San Francisco, California: Wikimedia Foundation, Inc). May 11, 2012. http://en.wikipedia.org/wiki/Jupiter_(mythology). Retrieved 2012-05-11.
- Joseph Campbell (2008). The Masks of God: Occidental Mythology. Paw Prints. p. 564. ISBN 1439508925. Retrieved 2013-01-06. Unknown parameter
- Manly Palmer Hall (1928). Secret Teachings of All Ages. San Francisco: Hall Publishing Company. p. 648. Retrieved 2013-01-06.
- William Fairfield Warren (1885). Paradise Found The Cradle of the Human Races at the North Pole. Boston: Houghton, Mifflin and Company. Retrieved 2013-01-06.
- John Strange (1980). Caphtor/Keftiu: A New Investigation. Brill Archive. p. 227. ISBN 9004062564. Retrieved 2013-01-11.
- David Ulansey (1989). The Origins of the Mithraic Mysteries: Cosmology and Salvation in the Ancient World. Oxford, England: Oxford University Press. ISBN 0-19-505402-4. Retrieved 2013-01-13. | 0.891858 | 3.785622 |
Phaethon confirmed as rock comet by STEREO vision
The Sun-grazing asteroid, Phaethon, has betrayed its true nature by showing a comet-like tail of dust particles blown backwards by radiation pressure from the Sun. Unlike a comet, however, Phaethon's tail doesn't arise through the vaporization of an icy nucleus. During its closest approach to the Sun, researchers believe that Phaethon becomes so hot that rocks on the surface crack and crumble to dust under the extreme heat. The findings will be presented by David Jewitt on Tuesday 10 September at the European Planetary Science Congress (EPSC) 2013 in London.
Most meteor showers arise when the Earth ploughs through streams of debris released from comets in the inner solar system. The Geminids, which grace the night sky annually in December, are one of the best known and most spectacular of the dozens of meteor showers. However, astronomers have known for 30 years that the Geminids are not caused by a comet but by a 5 km diameter asteroid called (3200) Phaethon.
Until recently, though, and much to their puzzlement, astronomer's attempts to catch Phaethon in the act of throwing out particles all ended in failure. The tide began to turn in 2010 when Jewitt and colleague, Jing Li, found Phaethon to be anomalously bright when closest to the Sun. The key to success was their use of NASA's STEREO Sun-observing spacecraft. Phaethon at perihelion appears only 8 degrees (16 solar diameters) from the sun, making observations with normal telescopes impossible. Now, in further STEREO observations from 2009 and 2012, Jewitt, Li and Jessica Agarwal have spotted a comet-like tail extending from Phaethon.
"The tail gives incontrovertible evidence that Phaethon ejects dust," said Jewitt. 'That still leaves the question: why? Comets do it because they contain ice that vaporizes in the heat of the Sun, creating a wind that blows embedded dust particles from the nucleus. Phaethon's closest approach to the Sun is just 14 per cent of the average Earth-Sun distance (1AU). That means that Phaethon will reach temperatures over 700 degrees Celsius – far too hot for ice to survive."
The team believes that thermal fracture and desiccation fracture (formed like mud cracks in a dry lake bed) may be launching small dust particles that are then picked up by sunlight and pushed into the tail. While this is the first time that thermal disintegration has been found to play an important role in the Solar System, astronomers have already detected unexpected amounts of hot dust around some nearby stars that might have been similarly-produced.
So, is Phaethon an asteroid or a comet? Asteroids and comets derive from entirely different regions of the solar system; asteroids from between Mars and Jupiter (roughly 2 to 3.5 AU) and comets from the frigid trans-Neptunian realms (30 AU and beyond).
"By the shape of its orbit, Phaethon is definitely an asteroid. But by ejecting dust it behaves like a 'rock comet'," said Jewitt. | 0.887868 | 3.827633 |
The smallest extrasolar
On April 5, 2007, a team of astronomers in a European observatory in Chile discovered another planet found outside our solar system. This accomplishment was made through the use of a High Accuracy Radial Velocity for Planetary Searcher (HARPS) installed in a 3. 6 meter telescope (NASA). The smallest extrasolar planet known to date, it was dubbed Gliese 581c after Gliese 581 – the name of the star it orbits. Belonging to the constellation Libra, the planet is 20. 5 light years away or 190 trillion kilometers from Earth. Still, its parent star belongs to the 100 nearest stars to our sun.
Studying the planet up close using current space technology and within a man’s lifetime is still a remote possibility. This is because at the speed of light, it would take two decades of interstellar travel to reach it, about one decade to explore it and another two decades for the return trip. Gliese 581c’s diameter is 1. 5 times bigger than our Earth and is 5 times more massive (The Economist). It completes a full 10. 9 million kilometer orbit in a span of 13 days compared to our planet which accomplishes this in 365 days (Layton). This means that a year on Gliese 581c is equal to just about a week on Earth.
It travels round in between two other planets – Gliese 581d which is farther away and Gliese 581b which is nearer to their parent star (BBC News). Initial information reveals that Gliese 581c does not rotate (The Seattle Times). Unlike here on Earth where days consist of alternating night and day, one side of this planet is always day and the other always night. Gravity is also 1. 6 times stronger there so that if a person weighing 150lbs on Earth would stand on Gliese 581c’s surface, his weight would increase to 240lbs (The Seattle Times).
The new discovery is very significant because it features the first extrasolar planet with the potential to support extraterrestrial life. The initial criterion used in seriously considering this probability rested on theoretical calculations revealing that the planet’s location is within an ideal zone around its parent star. Compared to Earth, the planets around Gliese 581 orbit much closer around it but because the star is cooler, this distance is still favorable to water formation. Known as the Goldilocks zone or habitable zone, temperatures allow for water not to be frozen or in vapor form but in its liquid state.
Water is important in the formation and sustenance of life. The estimated range of temperatures on Gliese 581c is 0 – 40oC or equivalent to 32 – 104oF (The Economist). The average temperature on the side of the planet facing the star would be 20oC. The melting point of water is known to be from 0oC and above. Aside from being in the habitable zone, Gliese 581c can also be able to maintain life based on the presence and characteristics of its atmosphere. The occurrence of life related gases such as methane and oxygen would be a step further in this direction.
The parent star Gliese 581 is classified as a red dwarf which at 3,000oC, is 50 times less than the brightness and energy of our sun (Than & Sample). It is also a third smaller and way older. Yet, it is stable and has a relatively longer lifespan. The latter is based on the fact that red dwarfs have enough hydrogen to burn as energy, enabling them to last far into the geological future (Haas). Since it took billions of years on Earth for human beings to evolve, the parent star’s longer lifespan is favorable if evolutionary processes were to take place on the planet.
Further information has to be obtained to find out the other features of the planet because for now, its small size prevents it from being seen using even the most advanced telescopes such as the Hubble. It is a recognized need that more sensitive instruments have to be developed for direct study to be possible. The HARPS used in the discovery of Gliese 581c is a spectrograph. It merely splits the light emitted by stars where particular patterns reveal the pull of existing planets around it, an indirect way of astronomical investigation (Begley).
Subsequent theoretical calculations then yielded the presumed characteristics of the planet. Computer imaging software, based on planet-formation models, predicts that the planet’s surface may either be rocky or completely covered by oceans (Than). The latter is less likely according to astrobiologists so that Gliese 581c is regarded more as terrestrial or a planet composed of silicate rocks similar to the Earth and moon. If this would be established, the environment in Gliese 581c is anticipated to exhibit exceptional diversity.
Some regions would be dry with no air whereas in others, water and gases would abound a lot more compared to our planet (Science Daily). As the more than 250 previously discovered extrasolar planets were either too near or too far from their parent star or much like Jupiter whose dense, hot gases are hostile to life, the primary aim for scientists is to determine the certainty of biological life on Gliese 581c. Current space related projects such as the Terrestrial Planet Finder of the U. S. and the Darwin Mission of Europe were initiated to serve this purpose (The Economist).
Works Cited Begley, Sharon. “Looking For Life? Try Gliese 581c”. Newsweek 149(19), p. 13. 7 May 2007. 13 April 2009 < http://web. ebscohost. com article database>. British Broadcasting Corporation (BBC) News. New “Super Earth” Found in Space. One Minute World News. 25 April 2007. 13 April 2009 < http://news. bbc. co. uk/2/hi/science/nature/6589157. stm >. CTV. ca. Earth-like Planet Found That May Support Life. Science and Technology Section. 25 April 2007. 13 April 2009 < http://www. ctv. ca/servlet/ArticleNews/story/CTVNews/20070424/new_planet
_070424/20070425? hub=SciTech>. Haas, Johnson R. The Neighbor: Gliese 581c. Geochemical Society. Geochemical News. April 2007. 13 April 2009 <http://www. geochemsoc. org/publications/geochemicalnews/gn131apr07/theneighborgliese581c. htm>. Layton, Laura. “Super-Earth Found in Habitable Zone”. Astronomy 35(8), 2007 August. 13 April 2009 < http://web. ebscohost. com article database>. National Astronomical and Space Association. Astronomers Discover 1st Potentially Habitable Planet. Jet Propulsion Laboratory: California Institute of Technology. 25 April 2007.
13 April 2009 < http://planetquest. jpl. nasa. gov/news/superEarth. cfm>. Sample, Ian. “Second Earth” Found: 20 Light Years Away. The Guardian. 25 April 2007. 13 April 2009 < http://www. guardian. co. uk/science/2007/apr/25/starsgalaxiesandplanets. spaceexploration >. Science Daily. Gliese 581: Extrasolar Planet Might Indeed by Habitable. Science News. 14 December 2007. 13 April 2009 <http://www. sciencedaily. com/releases/2007/12/071213101403. htm>. The Economist. Sister Earth. 383(8526), p. 93. , 28 April 2007. Science and Technology Section.
13 April 2009 < http://web. ebscohost. com article database>. The Economist. The Planet Hunters. 383(8531), 2 June 2007. Briefing: Exoplanets Section. 13 April 2009 < http://web. ebscohost. com article database>. Than, Ker. Scientists Find Most Earthlike Planet Yet. MSNBC: Technology and Science. 25 April 2007. 13 April 2009 < http://www. msnbc. msn. com/id/18293978/>. The Seattle Times. New Planet May be Habitable but Don’t Start Packing. Nation and World. 25 April 2007. 13 April 2009 <http://seattletimes. nwsource. com/html/nationworld/2003680170_planet25. html>.Sample Essay of EduBirdie.com | 0.929625 | 3.628199 |
NASA’s Curiosity rover is on the Martian road to soon start the first ever study of currently active sand dunes anywhere beyond Earth. The dunes are located nearby, at the foothills of Mount Sharp, and Curiosity is due to arrive for an up close look in just a few days to start her unique research investigations.
The eerily dark dunes, named the “Bagnold Dunes,” skirt the northwestern flank of Mount Sharp. Ascending and diligently exploring the sedimentary layers of Mount Sharp is the primary goal of the mission.
“The ‘Bagnold Dunes’ are tantalizingly close,” says Ken Herkenhoff, Research Geologist at the USGS Astrogeology Science Center and an MSL science team member, in a mission update on Wednesday, Nov. 18.
The “Bagnold Dunes” have been quite noticeable in numerous striking images taken from Mars orbit, during the vehicles nail biting ‘7 Minutes of Terror’ descent from orbit, as well as in thousands upon thousands of images taken by Curiosity herself as the robot edged ever closer during her over three year long traverse across the floor of the Gale Crater landing site.
Curiosity must safely cross the expansive dune field before climbing Mount Sharp.
Although multiple NASA rovers, including Curiosity, have studied much smaller Martian sand ripples or drifts, none has ever visited and investigated up close these types of large dunes that range in size as tall as a two story building or more and as wide as a football field or more.
Moreover the Martian dunes are shifting even today.
“Shifting sands lie before me,” Curiosity tweeted. “Off to image, scoop and scuff active dunes on Mars. I’ll be the first craft to visit such dunes beyond Earth!”
“The Bagnold Dunes are active: Images from orbit indicate some of them are migrating as much as about 3 feet (1 meter) per Earth year. No active dunes have been visited anywhere in the solar system besides Earth,” notes NASA.
Curiosity is currently only some 200 yards or meters away from the first dune she will investigate, simply named “Dune 1.”
As the rover approaches closer and closer, the dune research campaign is already in progress as she snaps daily high resolution images and gathers measurements of the area’s wind direction and speed.
“We’ve planned investigations that will not only tell us about modern dune activity on Mars but will also help us interpret the composition of sandstone layers made from dunes that turned into rock long ago,” said Bethany Ehlmann of the California Institute of Technology and NASA’s Jet Propulsion Laboratory, in Pasadena, California, in a statement.
After arriving at the dune, the team will command Curiosity to scoop up samples for analysis by the rover’s pair of miniaturized chemistry instruments inside its belly. It will also scuff the dune with a wheel to examine and compare the surface and interior physical characteristics.
The dark dunes are informally named after British military engineer Ralph Bagnold (1896-1990), who conducted pioneering studies of the effect of wind on motion of individual particles in dunes on Earth. Curiosity will carry out “the first in-place study of dune activity on a planet with lower gravity and less atmosphere.”
Although the huge Bagnold dunes are of great scientific interest, the team will also certainly exercise caution in maneuvering the car sized six wheel robot.
Recall that NASA’s smaller golf cart Spirit Mars rover perished a few years back – albeit over 6 years into her 3 month mission – when the robot became unexpectedly mired in a nearly invisible sand ripple from which she was unable to escape.
Likewise, sister Opportunity got stuck in a sand ripple earlier in her mission that took the engineering team weeks of painstaking effort to extricate from a spot subsequently named ‘Purgatory’ that resulted in many lessons learned for future operations.
Opportunity is still hard at work – currently exploring Marathon Valley – nearly a dozen years into her planned 3 month mission.
Based on orbital observations by the CRISM and HiRISE instruments aboard NASA’s Mars Reconnaissance Orbiter, the science team has concluded that the Bagnold Dunes are mobile and also have an uneven distribution of minerals, such as olivine.
“We will use Curiosity to learn whether the wind is actually sorting the minerals in the dunes by how the wind transports particles of different grain size,” Ehlmann said.
“If the Bagnold campaign finds that other mineral grains are sorted away from heavier olivine-rich grains by the wind’s effects on dune sands, that could help researchers evaluate to what extent low and high amounts of olivine in some ancient sandstones could be caused by wind-sorting rather than differences in alteration by water,” say researchers.
“These dunes have a different texture from dunes on Earth,” said team member Nathan Bridges, of the Johns Hopkins University’s Applied Physics Laboratory, Laurel, Maryland.
“The ripples on them are much larger than ripples on top of dunes on Earth, and we don’t know why. We have models based on the lower air pressure. It takes a higher wind speed to get a particle moving. But now we’ll have the first opportunity to make detailed observations.”
Last month Curiosity conducted her eighth drill campaign for sample chemical analysis at the ‘Big Sky’ site, before moving on to ‘Greenhorn’. Big Sky was an area of cross-bedded sandstone rock in the Stimson geological unit on the lower slopes of Mount Sharp.
Curiosity has already accomplished her primary objective of discovering a habitable zone on the Red Planet – at the Yellowknife Bay area – that contains the minerals necessary to support microbial life in the ancient past when Mars was far wetter and warmer billions of years ago.
As of today, Sol 1168, November 19, 2015, she has driven over 6.9 miles (11.1 kilometers) kilometers and taken over 282,100 amazing images.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Learn more about Orbital ATK Cygnus, ISS, ULA Atlas rocket, SpaceX, Boeing, Space Taxis, Mars rovers, Orion, SLS, Antares, NASA missions and more at Ken’s upcoming outreach events:
Dec 1 to 3: “Orbital ATK Atlas/Cygnus launch to the ISS, ULA, SpaceX, SLS, Orion, Commercial crew, Curiosity explores Mars, Pluto and more,” Kennedy Space Center Quality Inn, Titusville, FL, evenings
Dec 8: “America’s Human Path Back to Space and Mars with Orion, Starliner and Dragon.” Amateur Astronomers Assoc of Princeton, AAAP, Princeton University, Ivy Lane, Astrophysics Dept, Princeton, NJ; 7:30 PM. | 0.879416 | 3.509686 |
How Did Structure Form in the Universe?
The Big Bang theory is widely considered to be a successful theory of cosmology, but the theory is incomplete. In its simplest form, the Big Bang theory assumes that matter and radiation are uniformly distributed throughout the universe and that general relativity is universally valid. While this can account for the existence of the cosmic microwave background radiation and explain the origin of the light elements, it does not explain the existence of stars, galaxies and large-scale structure. The famous "Deep Field Image" taken by the Hubble Space Telescope, shown below, provides a stunning view of such structure. How did these structures form? Most cosmologists believe that the galaxies that we observe today grew from the gravitational pull of small fluctuations in the nearly-uniform density of the early universe. These fluctuations leave an imprint in the cosmic microwave background radiation in the form of temperature fluctuations from point to point across the sky. The WMAP satellite measures these small fluctuations in the temperature of the cosmic microwave background radiation and in turn probe the early stages of structure formation.
The solution of the structure problem must be built into the framework of the Big Bang theory. WMAP's observations provide the type of data needed to form detailed theories to answer these questions. | 0.850477 | 3.718887 |
eso1252 — Publikim shkencor
Stars Reveal the Secrets of Looking Young
19 Dhjetor 2012
Some people are in great shape at the age of 90, while others are decrepit before they’re 50. We know that how fast people age is only loosely linked to how old they actually are — and may have more to do with their lifestyle. A new study using both the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory and the NASA/ESA Hubble Space Telescope reveals that the same is true of star clusters.
Globular clusters are spherical collections of stars, tightly bound to each other by their mutual gravity. Relics of the early years of the Universe, with ages of typically 12–13 billion years (the Big Bang took place 13.7 billion years ago), there are roughly 150 globular clusters in the Milky Way and they contain many of our galaxy’s oldest stars.
But while the stars are old and the clusters formed in the distant past, astronomers using the MPG/ESO 2.2-metre telescope and the NASA/ESA Hubble Space Telescope have found that some of these clusters are still young at heart. The research is presented in the 20 December 2012 issue of the journal Nature.
“Although these clusters all formed billions of years ago,” says Francesco Ferraro (University of Bologna, Italy), the leader of the team that made the discovery, “we wondered whether some might be aging faster or slower than others. By studying the distribution of a type of blue star that exists in the clusters, we found that some clusters had indeed evolved much faster over their lifetimes, and we developed a way to measure the rate of aging.”
Star clusters form in a short period of time, meaning that all the stars within them tend to have roughly the same age. Because bright, high-mass stars burn up their fuel quite quickly, and globular clusters are very old, there should only be low-mass stars still shining within them.
This, however, turns out not to be the case: in certain circumstances, stars can be given a new burst of life, receiving extra fuel that bulks them up and substantially brightens them. This can happen if one star pulls matter off a close neighbour, or if they collide. The re-invigorated stars are called blue stragglers , and their high mass and brightness are properties that lie at the heart of this study.
Heavier stars sink towards the centre of a cluster as the cluster ages, in a process similar to sedimentation. Blue stragglers’ high masses mean they are strongly affected by this process, while their brightness makes them relatively easy to observe .
To better understand cluster aging, the team mapped the location of blue straggler stars in 21 globular clusters, as seen in images from the MPG/ESO 2.2-metre telescope and Hubble, among other observatories . Hubble provided high resolution imagery of the crowded centres of 20 of the clusters, while the ground-based imagery gave a wider view of their less busy outer regions.
Analysing the observational data, the team found that a few clusters appeared young, with blue straggler stars distributed throughout, while a larger group appeared old, with the blue stragglers clumped in the centre. A third group was in the process of aging, with the stars closest to the core migrating inwards first, then stars ever further out progressively sinking towards the centre.
“Since these clusters all formed at roughly the same time, this reveals big differences in the speed of evolution from cluster to cluster,” said Barbara Lanzoni (University of Bologna, Italy), a co-author of the study. “In the case of fast-aging clusters, we think that the sedimentation process can be complete within a few hundred million years, while for the slowest it would take several times the current age of the Universe.”
As a cluster’s heaviest stars sink towards the centre, the cluster eventually experiences a phenomenon called core collapse, where the centre of the cluster bunches together extremely densely. The processes leading towards core collapse are quite well understood, and revolve around the number, density and speed of movement of the stars. However, the rate at which they happened was not known until now . This study provides the first empirical evidence of how quickly different globular clusters age.
Red giant stars are brighter, but they have a much lower mass, and therefore are not affected by the sedimentation process in the same way. (It is easy to distinguish these from blue stragglers because their colour is very different.)
Neutron stars, the extremely dense cores of stars much bigger than the Sun that exploded billions of years ago in the early history of globular clusters, have a similar mass to blue stragglers, and are affected by the sedimentation process, but they are incredibly difficult to observe and therefore do not make a useful subject for this study.
Blue stragglers are the only stars within clusters that combine high mass and high brightness.
Of the 21 clusters covered by this research, 20 were studied with Hubble, 12 with the MPG/ESO 2.2-metre telescope, eight with the Canada-France-Hawaii telescope and one with NAOJ’s Subaru Telescope.
Such a rate depends in a complex manner on the number of stars, their density and their velocity within a cluster. While the first two quantities are relatively easy to measure, velocity is not. For these reasons, previous estimates of the rate of globular cluster dynamical aging were based only on theoretical arguments, while the new method allows a totally empirical measurement.
Më shumë informacion
This research was presented in a paper, “Dynamical age differences amongst coeval star clusters as revealed by blue stragglers“, by F. R. Ferraro et al., to appear in the journal Nature on 20 December 2012.
The team is composed of F. R. Ferraro (University of Bologna, Italy), B. Lanzoni (University of Bologna), E. Dalessandro (University of Bologna), G. Beccari (ESO, Garching, Germany), M. Pasquato (University of Bologna), P. Miocchi (University of Bologna), R. T. Rood (University of Virginia, Charlottesville, USA), S. Sigurdsson (Pennsylvania State University, USA), A. Sills (McMaster University, Hamilton, Canada), E. Vesperini (Indiana University, Bloomington, USA), M. Mapelli (INAF-Osservatorio Astronomico di Padova, Italy), R. Contreras (University of Bologna), N. Sanna (University of Bologna), A. Mucciarelli (University of Bologna).
This research is part of the Cosmic-Lab project (www.cosmic-lab.eu) funded by the ERC (European Research Council) for a total amount of € 1.8 million for 5 years. Set up in 2007 by the European Union, the ERC aims to stimulate scientific excellence in Europe by encouraging competition for funding between the very best, creative researchers of any nationality and age. Since its launch, the ERC has funded over 2 500 researchers and their frontier research projects across Europe. The ERC operates according to an "investigator-driven", or "bottom-up", approach, allowing researchers to identify new opportunities in all fields of research (Physical Sciences and Engineering, Life Sciences, and Social Sciences and Humanities). It has also become a benchmark of the competitiveness of national research systems and complements existing funding schemes at national and European levels. The ERC, which is the newest component of the EU's Seventh Research Framework Programme, has a total budget of €7.5 billion from 2007 to 2013. Last year, the European Commission proposed a substantial increase in the ERC's budget for 2014 to 2020 under the new framework programme ('Horizon 2020'). The ERC is composed of an Executive Agency and a Scientific Council. The Scientific Council is made up of 22 top researchers and sets the ERC's scientific strategy. The ERC is led by President Prof. Helga Nowotny and the Scientific Council is represented in Brussels by Secretary General Prof. Donald Dingwell. The ERC Executive Agency implements the "Ideas" Specific Programme and is led by Director (ad int.) Pablo Amor.
The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning the 39-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
- Research paper
- Hubble press release
- Photos of the MPG/ESO 2.2-metre telescope
- Other photos taken with the MPG/ESO 2.2-metre telescope
- Photos of La Silla
University of Bologna
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University of Bologna
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ESO, La Silla, Paranal, E-ELT & Survey Telescopes Press Officer
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Tel: +49 89 3200 6855 | 0.801264 | 3.819041 |
Space is so amazingly vast that it’s just about impossible to study everything in a short period of time. That’s why we seemingly continue to land on more discoveries about the universe around us all the time.
Modern astronomy, even with high-powered technical equipment, is no different. New findings published in the Monthly Notices Letters of the Royal Astronomical Society detail the first pulsar ever discovered in the Andromeda galaxy, a galaxy that is popular for study because it’s so close to our Milky Way and has a lot of similar characteristics to our galaxy.
A pulsar is a highly-magnetized spinning neutron star that emits a beam of electromagnetic radiation on either side. These are created when a star explodes into a supernova, and are essentially the remnants of a dead star. The effects of its spinning produce a pulsing effect, hence why it is given the name it has.
The discovery was made with the European Space Agency’s XMM-Newton Space Telescope.
“We were expecting to detect periodic signals among the brightest X-ray objects in Andromeda, in line with what we already found during the 1960s and 1970s in our own Galaxy,” says Gian Luca Israel, an author of the paper.
“We looked through archival data of Andromeda spanning 2000–13, but it wasn’t until 2015 that we were finally able to identify this object in the galaxy’s outer spiral in just two of the 35 measurements.”
The ESA notes in a statement that the Pulsar spins every 1.2 seconds and is a part of a binary system where the secondary star rotates around it every 1.3 days.
There hasn’t been a lot of time spent observing the binary system just yet, but so far it seems like it could be an encyclopedia of new information that scientists are just waiting to observe up close to try to understand in more detail.
Source: ESA, Wikipedia | 0.845018 | 3.521393 |
Pictured: An artist’s impression of the trio of super-Earths discovered by a European team using the HARPS spectrograph on the ESO 3.6-metre telescope at La Silla, Chile, after 5 years of monitoring. The three planets, having 4.2, 6.7, and 9.4 times the mass of the Earth, orbit the star HD 40307 with periods of 4.3, 9.6, and 20.4 days, respectively. Credit: ESO.
A star about 100 light-years from Earth, called GJ 9827, hosts what may be one of the most massive and dense super-Earth planets detected to date according to new research led by the Carnegie Institution for Science’s Johanna Teske.
This new information provides evidence to help astronomers better understand the process by which such planets form.
The GJ 9827 star actually hosts a trio of planets, discovered by NASA’s exoplanet-hunting Kepler/K2 mission, and all three are slightly larger than Earth. This is the size that the Kepler mission determined to be most common in the galaxy with periods between a few and several-hundred days.
Intriguingly, no planets of this size exist in our Solar System. This makes scientists curious about the conditions under which they form and evolve.
One important key to understanding a planet’s history is to determine its composition. Are these super-Earths rocky like our own planet? Or do they have solid cores surrounded by large, gassy atmospheres?
To try to understand what an exoplanet is made of, scientists need to measure both its mass and its radius, which allows them to determine its bulk density.
When quantifying planets in this way, astronomers have noticed a trend. It turns out that planets with radii greater than about 1.7 times that of Earth have a gassy envelope, like Neptune, and those with radii smaller than this are rocky, like our home planet.
Some researchers have proposed that this difference is caused by photoevaporation, which strips planets of their surrounding envelope of so-called volatiles — substances like water and carbon dioxide that have low boiling points — creating smaller-radius planets. But more information is needed to truly test this theory.
This is why GJ 9827’s three planets are special — with radii of 1.64 (planet b), 1.29 (planet c) and 2.08 (planet d), they span this dividing line between super-Earth (rocky) and sub-Neptune (somewhat gassy) planets.
Luckily, teams of Carnegie scientists including co-authors Steve Shectman, Sharon Wang, Paul Butler, Jeff Crane, and Ian Thompson have been monitoring GJ 9827 with their Planet Finding Spectrograph (PFS), so they were able to constrain the masses of the three planets with data in hand, rather than having to scramble to get many new observations of GJ 9827.
“Usually, if a transiting planet is detected, it takes months if not a year or more to gather enough observations to measure its mass,” Teske explained. “Because GJ 9827 is a bright star, we happened to have it in the catalogue of stars that Carnegie astronomers been monitoring for planets since 2010. This was unique to PFS.”
The spectrograph was developed by Carnegie scientists and mounted on the Magellan Clay Telescopes at Carnegie’s Las Campanas Observatory.
The PFS observations indicate that planet b is roughly eight times the mass of Earth, which would make it one of the most-massive and dense super-Earths yet discovered. The masses for planet c and planet d are estimated to be about two and a half and four times that of Earth respectively, although the uncertainty in these two determinations is very high.
This information suggests that planet d has a significant volatile envelope, and leaves open the question of whether planet c has a volatile envelope or not. But the better constraint on the mass of planet b suggests that that it is roughly 50 percent iron.
“More observations are needed to pin down the compositions of these three planets,” Wang said. “But they do seem like some of the best candidates to test our ideas about how super-Earths form and evolve, potentially using NASA’s upcoming James Webb Space Telescope.”
Adapted from information issued by the Carnegie Institution for Science. | 0.899846 | 3.87886 |
By looking deeper into space (and farther back in time), astronomers and cosmologists continue to push the boundaries of what is known about the Universe. Thanks to improvements in instrumentation and observation techniques, we are now at the point where astronomers are able to observe some of the earliest galaxies in the Universe – which in turn is providing vital clues about how our Universe evolved.
It allowed us to spot auroras on Saturn and planets orbiting distant suns. It permitted astronomers to see galaxies in the early stages of formation, and look back to some of the earliest periods in the Universe. It also measured the distances to Cepheid variable stars more accurately than ever before, which helped astrophysicists constrain how fast the Universe is expanding (the Hubble Constant).
It did all of this and more, which is why no space telescope is as recognized and revered as the Hubble Space Telescope. And while it’s mission is currently scheduled to end in 2021, Hubble is still breaking new ground. Thanks to the efforts of a research team from the Instituto de Astrofísica de Canarias (IAC), Hubble recently obtained the deepest images of the Universe ever taken from space.
In their pursuit of learning how our Universe came to be, scientists have probed very deep into space (and hence, very far back in time). Ultimately, their goal is to determine when the first galaxies in our Universe formed and what effect they had on cosmic evolution. Recent efforts to locate these earliest formations have probed to distances of up to 13 billion light-years from Earth – i.e. about 1 billion years after the Big Bang.
From this, scientist are now able to study how early galaxies affected matter around them – in particular, the reionization of neutral atoms. Unfortunately, most early galaxies are very faint, which makes studying their interiors difficult. But thanks to a recent survey conducted by an international team of astronomers, a more luminous, massive galaxy was spotted that could provide a clear look at how early galaxies led to reionization.
In accordance with Big Bang model of cosmology, reionization refers to the process that took place after the period known as the “Dark Ages”. This occurred between 380,000 and 150 million years after the Big Bang, where most of the photons in the Universe were interacting with electrons and protons. As a result, the radiation of this period is undetectable by our current instruments – hence the name.
Just prior to this period, the “Recombination” occurred, where hydrogen and helium atoms began to form. Initially ionized (with no electrons bound to their nuclei) these molecules gradually captured ions as the Universe cooled, becoming neutral. During the period that followed – i.e. between 150 million to 1 billion years after the Big Bang – the large-scale structure of the Universe began to form.
Intrinsic to this was the process of reionization, where the first stars and quasars formed and their radiation reionized the surrounding Universe. It is therefore clear why astronomers want to probe this era of the Universe. By observing the first stars and galaxies, and what effect they had on the cosmos, astronomers will get a clearer picture of how this early period led to the Universe as we know it today.
Luckily for the research team, the massive, star-forming galaxies of this period are known to contain a great deal of dust. While very faint in the optical band, these galaxies emit strong radiation at submillimeter wavelengths, which makes them detectable using today’s advanced telescopes – including the South Pole Telescope (SPT), the Atacama Pathfinder Experiment (APEX), and Atacama Large Millimeter Array (ALMA).
For the sake of their study, Strandet and Weiss relied on data from the SPT to detect a series of dusty galaxies from the early Universe. As Maria Strandet and Axel Weiss of the Max Planck Institute for Radio Astronomy (and the lead author and co-authors on the study, respectively) told Universe Today via email:
“We have used light of about 1 mm wavelength, which can be observed by mm telescopes like SPT, APEX or ALMA. At this wavelength the photons are produced by the thermal radiation of dust. The beauty of using this long wavelength is, that for a large redshift range (look back time), the dimming of galaxies [caused] by increasing distance is compensated by the redshift – so the observed intensity is independent of the redshift. This is because, for higher redshift galaxies, one is looking at intrinsically shorter wavelengths (by (1+z)) where the radiation is stronger for a thermal spectrum like the dust spectrum.”
This was followed by data from ALMA, which the team used to determine the distance of the galaxies by looking at the redshifted wavelength of carbon monoxide molecules in their interstellar mediums (ISM). From all the data they collected, they were able to constrain the properties of one of these galaxies – SPT0311-58 – by observing its spectral lines. In so doing, they determined that this galaxy existed just 760 million years after the Big Bang.
“Since the signal strength at 1mm is independent of the redshift (look back time), we do not have an a priori clue if an object is relatively near (in the cosmological sense) or at the epoch of reionization,” they said. “That is why we undertook a large survey to determine the redshifts via the emission of molecular lines using ALMA. SPT0311-58 turns out to be the highest redshift object discovered in this survey and in fact the most distant massive dusty star-forming galaxy so far discovered.”
From their observations, they also determined that SPT0311-58 has a mass of about 330 billion Solar-masses, which is about 66 times as much as the Milky Way Galaxy (which has about 5 billion Solar-masses). They also estimated that it is forming new stars at a rate of several thousand per year, which could as be the case for neighboring galaxies that are dated to this period.
This rare and distant object is one of the best candidates yet for studying what the early Universe looked like and how it has evolved since. This in turn will allow astronomers and cosmologists to test the theoretical basis for the Big Bang Theory. As Strandet and Weiss told Universe Today about their discovery:
“These objects are important to understanding the evolution of galaxies as a whole since the large amounts of dust already present in this source, only 760 million years after the Big Bang, means that it is an extremely massive object. The mere fact that such massive galaxies already existed when the Universe was still so young puts strong constraints on our understanding of galaxy mass buildup. Furthermore the dust needs to form in a very short time, which gives additional insights on the dust production from the first stellar population.”
The ability to look deeper into space, and farther back in time, has led to many surprising discoveries of late. And these have in turn challenged some of our assumptions about what happened in the Universe, and when. And in the end, they are helping scientists to create a more detailed and complete account of cosmic evolution. Someday soon, we might even be able to probe the earliest moments in the Universe, and watch creation in action!
In about 4 billion years, scientists estimate that the Andromeda and the Milky Way galaxies are expected to collide, based on data from the Hubble Space Telescope. And when they merge, they will give rise to a super-galaxy that some are already calling Milkomeda or Milkdromeda (I know, awful isn’t it?) While this may sound like a cataclysmic event, these sorts of galactic collisions are quite common on a cosmic timescale.
As an international group of researchers from Japan and California have found, galactic “hookups” were quite common during the early universe. Using data from the Hubble Space Telescope and the Subaru Telescope at in Mauna Kea, Hawaii, they have discovered that 1.2 billion years after the Big Bang, galactic clumps grew to become large galaxies by merging. As part of the Hubble Space Telescope (HST) “Cosmic Evolution Survey (COSMOS)”, this information could tell us a great about the formation of the early universe. | 0.882802 | 4.112887 |
Two huge planets found orbiting a star 375 light-years away are the oldest alien worlds yet discovered, scientists say.
With an estimated age of 12.8 billion years, the host star—and thus the planets—most likely formed at the dawn of the universe, less than a billion years after the big bang.
“The Milky Way itself was not completely formed yet,” said study leader Johny Setiawan, who conducted the research while at the Max-Planck Institute for Astronomy in Heidelberg, Germany.
(Related: “Oldest Material in Solar System Found.”)
During a recent survey, Setiawan and colleagues found the signatures of the two planets orbiting the star, dubbed HIP 11952.
Based on the team’s calculations, one world is almost as massive as Jupiter and completes an orbit in roughly seven days. The other planet is nearly three times Jupiter’s mass and has an orbital period of nine and a half months.
It’s possible the planets are much younger than they seem if the worlds formed long after their star was born—but such a scenario is unlikely, the team says.
“Usually planets form just shortly after the star formation,” Setiawan said. “Second-generation planets might also form after a star has died, but this is still under debate.”
Ancient Planets Defy Theory
Setiawan and colleagues found the ancient planets using a technique called radial velocity, in which astronomers watch for periodic wobbles in a star’s light due to the gravitational tugs of orbiting worlds.
The discovery indicates that planet formation in the early universe was possible despite the fact that stars in existence back then were metal-poor—the astronomy term for stars lacking in elements heavier than hydrogen and helium.
In the case of HIP 11952, “its iron abundance is only about one percent that of our sun,” Setiawan said.
The idea of planets springing from such a stellar makeup runs counter to a widely accepted theory called the accretion model, which says that heavy elements are needed to form planets.
Even gas giants like Saturn and Jupiter require heavy elements to take shape, the thinking goes, because they are built upon solid cores. (Related: “New Model of Jupiter’s Core Ignites Planet Birth Debate.”)
The accretion theory has so far been backed up by observations: Most of the planet-harboring stars discovered to date are relatively young and have moderate to high amounts of metals.
But there may be an observational bias, Setiawan said: Astronomers may think the accretion model is correct because planet hunters have been targeting mostly young, sunlike stars.
“To verify this issue, it is necessary to do a planet-search survey around [older] metal-poor stars,” Setiawan said.
(Also see “New ‘Super Earth’ Found at Right Distance for Life.”)
Clock Ticking for Oldest Worlds
Despite the newfound planets’ longevity, it’s unlikely the worlds will survive for another 13 billion years.
The parent star will soon transform into a red giant, Setiawan said, one of the last stages of a sunlike star’s life. (Related: “New ‘Deep Fried’ Planets Found—Survivors of Star Death.”)
During this stage, the star will swell in size and most likely engulf any nearby planets. | 0.889477 | 3.941807 |
This next project uses two of my favorite topics. Machine learning and crowdfunding. The brains at MIT are taking a new approach in the analysis of space data.
As part of an effort to identify distant planets hospitable to life, NASA has established a crowdsourcing project in which volunteers search telescopic images for evidence of debris disks around stars, which are good indicators of exoplanets.
Using the results of that project, researchers at MIT have now trained a machine-learning system to search for debris disks itself. The scale of the search demands automation: There are nearly 750 million possible light sources in the data accumulated through NASA’s Wide-Field Infrared Survey Explorer (WISE) mission alone.
In tests, the machine-learning system agreed with human identifications of debris disks 97 percent of the time. The researchers also trained their system to rate debris disks according to their likelihood of containing detectable exoplanets. In a paper describing the new work in the journal Astronomy and Computing, the MIT researchers report that their system identified 367 previously unexamined celestial objects as particularly promising candidates for further study.
The work represents an unusual approach to machine learning, which has been championed by one of the paper’s coauthors, Victor Pankratius, a principal research scientist at MIT’s Haystack Observatory. Typically, a machine-learning system will comb through a wealth of training data, looking for consistent correlations between features of the data and some label applied by a human analyst – in this case, stars circled by debris disks.
But Pankratius argues that in the sciences, machine-learning systems would be more useful if they explicitly incorporated a little bit of scientific understanding, to help guide their searches for correlations or identify deviations from the norm that could be of scientific interest.
“The main vision is to go beyond what A.I. is focusing on today,” Pankratius says.
Today, we’re collecting data, and we’re trying to find features in the data. You end up with billions and billions of features. So what are you doing with them? What you want to know as a scientist is not that the computer tells you that certain pixels are certain features. You want to know ‘Oh, this is a physically relevant thing, and here are the physics parameters of the thing.
The new paper grew out of an MIT seminar that Pankratius co-taught with Sara Seager, the Class of 1941 Professor of Earth, Atmospheric, and Planetary Sciences, who is well-known for her exoplanet research. The seminar, Astroinformatics for Exoplanets, introduced students to data science techniques that could be useful for interpreting the flood of data generated by new astronomical instruments. After mastering the techniques, the students were asked to apply them to outstanding astronomical questions.
For her final project, Tam Nguyen, a graduate student in aeronautics and astronautics, chose the problem of training a machine-learning system to identify debris disks, and the new paper is an outgrowth of that work. Nguyen is first author on the paper, and she’s joined by Seager, Pankratius, and Laura Eckman, an undergraduate majoring in electrical engineering and computer science.
From the NASA crowdsourcing project, the researchers had the celestial coordinates of the light sources that human volunteers had identified as featuring debris disks. The disks are recognizable as ellipses of light with slightly brighter ellipses at their centers. The researchers also used the raw astronomical data generated by the WISE mission.
To prepare the data for the machine-learning system, Nguyen carved it up into small chunks, then used standard signal-processing techniques to filter out artifacts caused by the imaging instruments or by ambient light. Next, she identified those chunks with light sources at their centers, and used existing image-segmentation algorithms to remove any additional sources of light. These types of procedures are typical in any computer-vision machine-learning project.
But Nguyen used basic principles of physics to prune the data further. For one thing, she looked at the variation in the intensity of the light emitted by the light sources across four different frequency bands. She also used standard metrics to evaluate the position, symmetry, and scale of the light sources, establishing thresholds for inclusion in her data set.
In addition to the tagged debris disks from NASA’s crowdsourcing project, the researchers also had a short list of stars that astronomers had identified as probably hosting exoplanets. From that information, their system also inferred characteristics of debris disks that were correlated with the presence of exoplanets, to select the 367 candidates for further study. | 0.847192 | 3.272365 |
NASA’s Voyager 1 spacecraft has entered the last region it has to cross before reaching interstellar space.
The team describes this new region as a ‘magnetic highway’ for charged particles. Our sun’s magnetic field lines are connected to interstellar magnetic field lines, allowing lower-energy charged particles originating inside our heliosphere to zoom out and allows higher-energy particles from outside to stream in.
Until they enter this region, the charged particles simply bounce around in all directions.
The Voyager team reckons that this region must still be inside our solar bubble, as the direction of the magnetic field lines hasn’t changed – which it will do, they believe, when Voyager breaks through to interstellar space.
“Although Voyager 1 still is inside the sun’s environment, we now can taste what it’s like on the outside because the particles are zipping in and out on this magnetic highway,” says Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena.
“We believe this is the last leg of our journey to interstellar space. Our best guess is it’s likely just a few months to a couple years away. The new region isn’t what we expected, but we’ve come to expect the unexpected from Voyager.”
Since December 2004 when Voyager 1 crossed a point in space called the termination shock, it’s been exploring the heliosphere’s outer layer, or heliosheath. Here, the solar wind abruptly slowed down from supersonic speeds and became turbulent.
Voyager 1 spent about five and a half years in this environment before the outward speed of the solar wind slowed to zero, at which point the intensity of the magnetic field also began to increase.
Voyager data from two onboard instruments that measure charged particles showed the spacecraft first entered this magnetic highway region on July 28, 2012. The region ebbed away and flowed toward Voyager 1 several times. The spacecraft entered the region again August 25, and the environment has been stable since.
“We are in a magnetic region unlike any we’ve been in before – about 10 times more intense than before the termination shock – but the magnetic field data show no indication we’re in interstellar space,” says Voyager magnetometer team member Leonard Burlaga.
“The magnetic field data turned out to be the key to pinpointing when we crossed the termination shock. And we expect these data will tell us when we first reach interstellar space.” | 0.817412 | 3.792885 |
Astronomers outline how and where to find wormholes in our galaxy
Wormholes are a staple of science fiction – but could they be science fact? Surprisingly, a bridge between two distant points in space and time fits into current physics models, although no evidence that they do exist has ever been found. Now, researchers from the University at Buffalo have outlined how we might go about looking for them in our own galaxy.
Star Trek, Dr. Who, Stargate, Interstellar, Sliders and countless other movies, TV shows, novels and video games have all dealt with wormholes in some way. Usually they’re depicted as tunnels that instantly connect two points separated by huge distances, allowing for a convenient way for ships and people to travel across the cosmos. Sometimes they allow for time travel, and other times characters use them to slide into other universes or dimensions.
While they might seem like little more than handy narrative devices, wormholes are surprisingly plausible in the real world. They’re consistent with Einstein’s general theory of relativity, and could conceivably offer the same kinds of benefits as their fictional counterparts – namely, faster-than-light space travel, time travel or jumps through the multiverse.
Of course, just because their existence is technically possible doesn’t mean they actually exist. So far, no astronomers have ever spotted any kind of evidence of a wormhole, but maybe that’s because we don’t know what to look for. Now, scientists from the University of Buffalo, Yangzhou University and Case Western Reserve University have outlined how and where we might find that evidence.
The team suggests that the best place to start looking is the center of the Milky Way galaxy. That’s where a supermassive black hole called Sagittarius A* lurks, providing the kind of extreme gravitational environment that a wormhole requires. And if there is a wormhole there, it should have a noticeable effect on nearby stars.
“If you have two stars, one on each side of the wormhole, the star on our side should feel the gravitational influence of the star that’s on the other side,” says Dejan Stojkovic, an author on the study. “The gravitational flux will go through the wormhole. So if you map the expected orbit of a star around Sagittarius A*, you should see deviations from that orbit if there is a wormhole there with a star on the other side.”
The researchers single out a star called S2, which orbits the black hole, as the best bet. Perturbations in the expected path of this star could provide the first evidence of wormholes, if it’s observed for a long-enough period of time.
That said, there are a few problems with the idea. Current technology most likely isn’t powerful enough to detect the kind of disturbances in S2’s orbit that might indicate a wormhole, but the team says that advanced techniques on the horizon could do the trick.
Another major issue though is that even if some weirdness is found in the orbit of S2, it doesn’t necessarily mean a wormhole is to blame. There could be other explanations that would need to be investigated.
But even if we do discover evidence that wormholes exist, they might not be the incredible shortcuts sci-fi promises. Although technically traversable, they probably aren’t stable enough to let large objects through.
“Even if a wormhole is traversable, people and spaceships most likely aren’t going to be passing through,” says Stojkovic. “Realistically, you would need a source of negative energy to keep the wormhole open, and we don’t know how to do that. To create a huge wormhole that’s stable, you need some magic.”
The final nail in the coffin is the little matter of the distance between Earth and the center of the galaxy – over 26,000 light-years. That’s a long way to go for a so-called “shortcut.”
The research was published in the journal Physical Review D.
Source: University at Buffalo | 0.873104 | 3.755819 |
Scientists have searched the universe for a long time, but a recent study suggests that ancient asteroid influences have produced "important components of life" right next door ̵
Researchers were able to mimic the early Martian atmosphere by blending mixtures of varying levels of hydrogen and nitrogen and bottled carbon dioxide, which were then hit with infrared laser pulses to determine the amount of nitrate formed. A great surprise was that nitrate yields increased , as hydrogen was included in the laser-shocked experiments simulating asteroid impacts, "the study's lead author, Dr. Rafael Navarro-González, said in a statement.
Navarro-González continued," This was not intuitive, Hydrogen leads to an oxygen-deficient environment, whereas the formation of nitrate requires oxygen, but the presence of hydrogen resulted in a faster cooling of the shock-heated gas, capturing nitrate, the precursor of nitrate, at higher temperatures with higher yields. " As Space.com notes, this is The Martian atmosphere is only 1 percent as thick as Earth, but four billion years ago it was much thicker. The ancient planet once had vast lakes and seas, but due to the weakened atmosphere, they have largely evaporated.
The prospect of significant amounts of hydrogen in the ancient Martian atmosphere could mean that the planet once supported life.
"Hydrogen as a greenhouse gas in the atmosphere is interesting for both the climate history of Mars and for habitability," said co-author Jennifer Stern, a planetary geochemist at NASA's Goddard Space Flight Center in Greenbelt, MD
LIFE ON THE EARTH CAN COME FROM COLLISION WITH THE OLD PLANET MORE THAN 4 BILLION YEARS AGO with liquid surface water and an increased production of nitrates, which are vital – it is very exciting, "she continued. "The results of this study suggest that these two things that are important to life fit together, and one reinforces the other's presence."
A study at the end of 2018 suggested that a life could hide beneath the surface of Mars Salty, Underground Lakes.
CLICK HERE TO OBTAIN THE FOX NEWS APP | 0.83704 | 3.604692 |
“Like a comet burn’d
That fires the length Ophiuchus huge
In the Arctic sky, and from his horrid hair
Shakes pestilence and war” (Milton, Paradise Lost)
With the ISON comet drawing eyes to the night sky, I started thinking a lot about the superstitions and magical beliefs surrounding the appearance of comets in the sky. Comets have long inspired people in strange, occasionally beautiful, and sometimes disturbing ways. Mark Twain’s life was framed by the appearance of Haley’s Comet, a point the author himself noted. The Heaven’s Gate cult engaged in a group suicide surrounding the arrival of the Hale-Bopp comet.
Increase Mather, famed early American religious writer, dedicated an entire work to explaining the spiritual importance of comets in his Kometographia of 1683. He was responding to the presence of the Great Comet of 1680, which had captured the attention of most of the Western world, and felt that many people would be afraid at this sign and misunderstand it as a phenomenon which directly influenced the course of events on earth, rather than a sign from God of some important event to come (see more here). Generally speaking, comets have historically been associated with strife and woe to come. My Opie/Tatem Dictionary of Superstitions gives a laundry list of examples of ill-omen presaged by what the Venerable Bede called “long-haired stars”:
- A comet as portending a change in governance (Tacitus, Annals)
- Famine or pestilence or war or “fearful storms” (Byrhtferth, Manual)
- A comet [the Great Comet of 1680] appeared two days before the Duke of Monmouth died, and all over Europe before the death of Charles II (J. Case, Angelical Guide)
- An appearance before the plague struck London (Defoe, Journal of a Plague Year)
- A wry observation that those who laugh at comets as tokens of disaster will studiously insist on “times and situations proper for intellectual performances” (Johnson, The Idler)
In the New World, comets seem to have retained much of their wicked reputation. In some cases the danger foretold by the comet is vague and ill-defined: “When a comet appears there will be trouble” (Roberts, “Louisiana Superstitions”). In other places, the significance of the hairy star was more direct and its consequences very clearly understood: “A comet is a sign of war” (Thomas, Kentucky Superstitions). Why should these astronomical phenomena, which had been showing up in night skies for ages, have such a bad rap? Considering even Classical authors like Tacitus cite the comet as woeful, the impulse must run deep. The unique cosmological view of Calvinism, though, which influenced much of Atlantic American colonization, both denigrated occult practices like witchcraft and supported an enchanted view of a univers under Divine direction:
“The Calvinism of the colonial awakenings also paralleled important occult ideas. The fatalism inherent in Calvinism’s concept of predestination found an occult equivalent in the idea fundamental to astrology that motions of star and planets revealed a future that individuals could not control. Calvinist evangelists and occult practitioners also explained catastrophes in similar ways. Believers in occult ideas thought the coming of comets and eclipses had inescapable and usually disastrous consequences; not even kings and queens escaped their verdicts. No one escaped judgment by the Calvinist God either. Sometimes He damned seemingly model Christians simply to demonstrate His sovereign” (Butler, “Magic, Astrology, & the Early American Religious Heritage”).
The shared cosmology of the colonists saw the universe as inhabited by spiritual consciousness, and an intelligence that wished to convey its meaning to human beings for one reason or another. Signs, omens, and portents were one such method. Comets, with their placement among the stars, their strange and ill-understood movement, and temporary nature made perfect fodder for prognosticators of all stripes—religious, occult, and both (they did exist, even during the Colonial period).
Lest we make the mistake of thinking that the observation of comets was the purview of only a few dusty old white occultists or a lot of fiery former Englishmen with strong religious convictions, I’d also like to point out that the cosmology which imbued comets with significance stretched across a broad swath of New World denizens, including Native Americans, Spanish and French colonists, and of course, the imported Black slaves.
“English Protestants often read unusual events as evidence of the divine presence in everyday life, acknowledging the activity of a creator deity who operated through omens and portents within the natural order, or signs and wonders in the heavens, philosophy known as Providentialism. “Comets, hailstorms, monster births and apparitions” and other disruptions of the ordinary were demonstrations that foretold God’s will or signaled His displeasure withhumankind. Africans’ understandings of the universe were also inspired by visible manifestations of spiritual forces within nature. They too viewed thunder, lightning, and other elements as heralds of sacred hierophanies,the awesome presence of numerous divine beings.” (Chireau, Black Magic).
The Providentialism Chireau notes fits the cosmology of the English and other European settlers, but it is clearly not unique to them. A world with Divine presence not only innate to its component parts, but in which those component parts act as mediums for communicating with humans, is also very much an African perspective. And while it is tempting to think that such beliefs can be relegated to history’s dustbin, we should also remember that in our time comets stir up a lot of strange excitement. Religious scholar Camile Paglia notes, for example:
“The Children of God, founded in 1968 as Teens for Christ by “Moses” David Berg in Huntington Beach, California, were negligible in number but came to public attention when they loudly prophesied that the us would be destroyed by Comet Kohoutek in January 1974. The group continues under the name “The Family” and is regularly excoriated by conserva tive Christian watchdog groups for its practice of free love (called “Flirty Fishing”) as well as its heretical beliefs that Jesus was sexually active and that God is a woman. (Paglia, “Cults and Cosmic Consciousness”)
Paglia also references the Hale-Bopp comet mentioned earlier, and Marshall Applewhite’s Heaven’s Gate cult. I have, so far, not heard of any particularly distressing phenomena surrounding ISON’s appearance, but if nuclear war breaks out, I may have to blame that particular “long-haired star.”
If you have comet lore you’d like to share, please do so in the comments!
As always, thanks for reading! | 0.833191 | 3.262523 |
Tonight, look up at the night sky and you just might be lucky enough to see a bright, blurry ball with a visible greenish-gray shade. That greenish-gray shade object is a comet that orbits between the Sun and Jupiter will make its nearest approach to Earth in centuries. And this all will be happening right on the heels of this year’s most beautiful meteor shower of 2018
Tony Farnham, is a research scientist in the astronomy department at the University of Maryland. He appeared on Saturday morning after a long night observing the comet at the Discovery Channel Telescope. Discovery Channel Telescope is located about 40 miles southeast of Flagstaff, Ariz. Tony Farnham said “The fuzziness is just because it’s a ball of gas basically,” “You’ve got a one-kilometer solid nucleus in the middle, and gas is going out hundreds of thousands of miles.”
The Green Comet 46P appears green due to the gases it emits light. The ball of gas and dust, also called as the “Christmas comet,” was nicknamed 46P/Wirtanen, after the astronomer Carl Wirtanen, who found it back in 1948. It circles the sun once every 5.4 Earth years It passes by Earth roughly every 11 years, but its distance alter and it is rarely this close.
A map from Sky & Telescope demonstrating Comet 64P/Wirtanen’s path through the sky. Credit: Courtesy of Sky & Telescope
The closeness of 46P/Wirtanen give astronomers a chance to study the tail of the comet and see farther into the nucleus. This amazing article by Rao will help you get more information about where to look, depending on when you are able to go outside for the show. Tonight it will be its closest approach to the Earth in 20 years. And it won’t be this close again for centuries or perhaps even in a thousand years. | 0.866927 | 3.161946 |
Liquid brine can hang around on Mars’ surface, a new study suggests, but conditions may not be great for life as we know it.
That’s bad news for any Earth-based microorganisms determined to colonize the Red Planet, but good news for humans who don’t want to contaminate Mars with microbes hitching a ride on robot explorers.
Pure liquid water can’t last on Mars’ frigid surface. But mix in some salts, and H2O might stick around for a bit. NASA’s Curiosity and Phoenix landers have detected salts known as perchlorates in the Martian soil, and researchers have suggested that such salts might make transient brines possible (SN: 3/20/09).
No salty liquid water has been definitively found on Mars. But there have been hints of water dribbling out from underground (SN: 9/28/15), and a controversial report of a buried lake near the Red Planet’s south pole (SN: 12/17/18).
To learn more about how brines would behave in contemporary Martian conditions, Edgard Rivera-Valentín, a planetary scientist at the Lunar and Planetary Institute in Houston, and colleagues ran computer simulations. They found that one type of brine could remain liquid on the planet’s surface and a few centimeters below for up to six consecutive hours across 40 percent of the planet, mostly at middle to high northern latitudes. However, those brines would never get warmer than about –48° Celsius, about 25 degrees below the known tolerance for life on Earth, the team reports online May 11 in Nature Astronomy.
This finding is useful for anyone planning a mission to Mars, the researchers say. Expeditions to locales with the potential for liquid water are subject to strict protection protocols (SN: 10/29/19) to reduce the risk of contamination from Earth. If Martian brines are truly uninhabitable by any known organism from our planet, that may ease restrictions on future exploration. | 0.863588 | 3.308122 |
Pulsating stars have been one of the most intriguing objects in our universe and provide insightful value to how we can map out distances. Astronomers discover a new class of X-ray variable stars that have been in question for the last decade. The team that discovered this is from Canada and the United States. It includes universities such as Villanova, University of Colorado, Harvard, University of Texas, and University of Toronto.
To understand why this discovery is amazing we should clear out some of the main pieces here. For one variable stars. These are stars that change in brightness as seen from Earth. However, variable stars have their own sub-classifications and this discovery is specifically looking at Cepheid variable stars. These stars have periodic changes in brightness and pulsates radially like a cosmic lighthouse.
These are very important to astronomers because we use them to measure distances to galaxies or even calculate the expansion of the universe and compare it to the famous Hubble’s constant.
The Cepheid star that led to this discovery is located 890 light years from Earth and is one of the closest of its type. When scientists observed the star they noticed in the 5.4 day cycle the supergiant star would change the intensity of X-ray emissions at different points of the pulsation cycle. What’s fascinating is this Cepheid star would rise by ~400% near the time the star grows to its maxima. This is about 45 times greater in diameter than our Sun!
Villanova University’s Scott Engle says, “Our first X-ray observations of Cepheids were made in 2006, and our first detections were met with a good bit of skepticism. The notion that Cepheids could be X-ray active seemed far-fetched because these stars are only a few times more massive and a little hotter than the Sun. Over a decade later, we’ve finally shown that they can in fact be X-ray variable, but the work is far from over. Now we need to understand just how they generate and modulate their X-ray emissions, and what effect this could have on the Leavitt Period-Luminosity Law.”
What’s cool is to think about the fact astronomers have been studying Cepheid stars for the last two centuries and we’re still finding new discoveries like this.
On this supergiant star d Cep, astronomers also found that the wind speeds on this star travels at about 130,000 kilometers per hour. And this isn’t even the craziest part. The crazy part is when this star grows and gets larger it expands to over 3 million kilometers each pulsation period!
More research still needs to be done on how these X-ray emission originate from the Cepheid stars as well as testing this against the theory that the longer the pulsations are the brighter the star is.
Latest posts by Zain Husain (see all)
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- Stunning View of the Famous (M27) Dumbbell Nebula - February 9, 2020 | 0.854766 | 3.988901 |
A hole at the heart of a stunning rose-like interstellar cloud has puzzled astronomers for decades. But new research, led by the University of Leeds, offers an explanation for the discrepancy between the size and age of the Rosetta Nebula's central cavity and that of its central stars.
The Rosette Nebula is located in the Milky Way Galaxy roughly 5,000 light-years from Earth and is known for its rose-like shape and distinctive hole at its centre. The nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases with several massive stars found in a cluster at its heart.
Rosette Nebula image is based on data obtained as part of the INT Photometric H-Alpha Survey of the Northern Galactic Plane, prepared by Nick Wright, Keele University, on behalf of the IPHAS Collaboration
Credit: Nick Wright, Keele University
This is a 3-D visualization of the simulated nebula, showing the dense disc-like molecular cloud in red, the tenuous stellar wind focused away from the disc in blue and the magnetic field lines in grey. The magnetic field is of key importance in forming a disc-like, not spherical, molecular cloud.
Credit: C. J. Wareing et al., 2018, MNRAS
Stellar winds and ionising radiation from these massive stars affect the shape of the giant molecular cloud. But the size and age of the cavity observed in the centre of Rosette Nebula is too small when compared to the age of its central stars.
Through computer simulations, astronomers at Leeds and at Keele University have found the formation of the Nebula is likely to be in a thin sheet-like molecular cloud rather than in a spherical or thick disc-like shape, as some photographs may suggest. A thin disc-like structure of the cloud focusing the stellar winds away from the cloud's centre would account for the comparatively small size of the central cavity.
Study lead author, Dr Christopher Wareing, from the School of Physics and Astronomy said: "The massive stars that make up the Rosette Nebula's central cluster are a few millions of years old and halfway through their lifecycle. For the length of time their stellar winds would have been flowing, you would expect a central cavity up to ten times bigger.
"We simulated the stellar wind feedback and formation of the nebula in various molecular cloud models including a clumpy sphere, a thick filamentary disc and a thin disc, all created from the same low density initial atomic cloud.
"It was the thin disc that reproduced the physical appearance - cavity size, shape and magnetic field alignment -- of the Nebula, at an age compatible with the central stars and their wind strengths.
"To have a model that so accurately reproduces the physical appearance in line with the observational data, without setting out to do this, is rather extraordinary.
"We were also fortunate to be able to apply data to our models from the ongoing Gaia survey, as a number of the bright stars in the Rosette Nebula are part of the survey.
Applying this data to our models gave us new understanding of the roles individual stars play in the Rosette Nebula. Next we'll look at the many other similar objects in our Galaxy and see if we can figure out their shape as well."
The simulations, published today in the Monthly Notices of the Royal Astronomical Society, were run using the Advanced Research Computing centre at Leeds. The nine simulations required roughly half a million CPU hours -- the equivalent to 57 years on a standard desktop computer.
Martin Callaghan, a member of the Advanced Research Computing team, said: "The fact that the Rosette Nebula simulations would have taken more than five decades to complete on a standard desktop computer is one of the key reasons we provide powerful supercomputing research tools. These tools enabled the simulations of the Rosette Nebula to be done in a matter of a few weeks."
Download images and captions from: https:/
Rosette Nebula image is based on data obtained as part of the INT Photometric H-Alpha Survey of the Northern Galactic Plane, prepared by Nick Wright, Keele University, on behalf of the IPHAS Collaboration. http://www.
The research paper, A new mechanical stellar wind feedback model for the Rosette Nebula is published in the Monthly Notices of the Royal Astronomical Society 13 February 2018 (DOI: 10.1093/mnras/sty148)
For additional information and to request interviews please contact Anna Harrison, Press Officer at the University of Leeds, on +44 (0)113 34 34196 or [email protected]
University of Leeds
1The University of Leeds is one of the largest higher education institutions in the UK, with more than 33,000 students from more than 150 different countries, and a member of the Russell Group of research-intensive universities.
We are a top ten university for research and impact power in the UK, according to the 2014 Research Excellence Framework, and are in the top 100 for academic reputation in the QS World University Rankings 2018. Additionally, the University was awarded a Gold rating by the Government's Teaching Excellence Framework in 2017, recognising its 'consistently outstanding' teaching and learning provision. Twenty-six of our academics have been awarded National Teaching Fellowships - more than any other institution in England, Northern Ireland and Wales - reflecting the excellence of our teaching. http://www.
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* Keele was recently awarded Gold in the Teaching Excellence Framework
* Keele is ranked No.1 in England for Course Satisfaction (Guardian University Guide 2018)
* 97% of the University's research was deemed to be world-leading, or of international importance, in the latest Research Excellence Framework
Anna Harrison | EurekAlert!
ATLAS telescope discovers first-of-its-kind asteroid
25.05.2020 | University of Hawaii at Manoa
New gravitational-wave model can bring neutron stars into even sharper focus
22.05.2020 | University of Birmingham
Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.
When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...
Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.
Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...
Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.
A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...
By studying the chemical elements on Mars today -- including carbon and oxygen -- scientists can work backwards to piece together the history of a planet that once had the conditions necessary to support life.
Weaving this story, element by element, from roughly 140 million miles (225 million kilometers) away is a painstaking process. But scientists aren't the type...
Study co-led by Berkeley Lab reveals how wavelike plasmons could power up a new class of sensing and photochemical technologies at the nanoscale
Wavelike, collective oscillations of electrons known as "plasmons" are very important for determining the optical and electronic properties of metals.
19.05.2020 | Event News
07.04.2020 | Event News
06.04.2020 | Event News
25.05.2020 | Medical Engineering
25.05.2020 | Information Technology
25.05.2020 | Information Technology | 0.802372 | 3.927345 |
A good astronomer prepares for an upcoming starry night by studying astronomical maps and noting the stars and planet’s ascensions to get an idea of when the targets will be visible at his/her sky. The geek astronomer today though, uses software to do this faster and easier. While it is not recommended to learn observational astronomy using automated software tools, the time and effort that can be saved certainly helps to keep people interested as well as draw in newcomers, including those who previously never thought of looking up at the sky. In this post, let’s look at two open source tools with which you can enhance your starry night experience, free of charge.
I want to learn about the night sky.
Getting to know your night sky requires a lot of time and devotion, reading astronomical maps, and experiencing neck pain trying to locate what you see on paper. The alternative that I suggest is using Stellarium virtual planetarium software. This tool allows you to set your location (anywhere in the world) and manipulate time at will. This way you can note what stars and constellations will be visible from your location at the time of your observation. Moreover, you can also remove the atmospheric light refraction and get a clear picture of what you should be able to see if all that city-light pollution was removed.
Now to get things even more interesting, you can even foresee how your targets will look through your own scope. Using the Oculars Plugin, you can add your scope’s and eyepiece’s characteristics and choose your targets. By enabling the plugin you will get a picture of what the selected field of view and magnification will contain. This is especially useful for astro-photographers who want to save some time searching for the right eyepiece. The ability to change mounting to equatorial will also help you search more realistically (as you would do with your own equipment).
Stellarium works in Windows, Mac, and Linux, and you can also take it with you on your observations by installing it on your Android device at the cost of $2.49 (the price may vary for your country’s currency).
What if you’re interested in the Moon.
The Moon is the largest and most impressive celestial body that amateur astronomers enjoy viewing. If you want to focus on the Moon, then you must download and install Virtual Moon Atlas. This piece of software contains all available up-to-date information about Earth’s only moon by connecting to the internet and downloading extra pictures/textures and data. The high fidelity 3D maps featured in this application will help you locate any crater or valley and learn more about it (diameter, historical facts, location, description etc.)
You can even see where the various Apollo missions landed, review old lunar maps, and use scientific overlays to determine surface soil slope and roughness, locate silicates, and learn about day and night temperatures on the Moon. All these data are derived from real lunar orbiters and visiting probes. VMA works in Mac, Windows, and Linux and its latest stable version was released not long ago, so the project is thankfully, still under active development.
If you’re a total astronomy novice, hopefully, these free software will help ease you into the field without much of the previously associated cost and time. Although software cannot replace what our eyes can see through telescopes, their usefulness as tools have always been obvious, and today, more than ever, people are getting their feet wet in amateur astronomy by the very means of such digital tools.Share This: | 0.810574 | 3.351977 |
Newly created strontium, an element used in fireworks, detected in space for the first time following observations with ESO telescope.
For the first time, a freshly made heavy element, strontium, has been detected in space, in the aftermath of a merger of two neutron stars. This finding was observed by ESO’s X-shooter spectrograph on the Very Large Telescope (VLT) and is published October 23, 2019, in Nature. The detection confirms that the heavier elements in the Universe can form in neutron star mergers, providing a missing piece of the puzzle of chemical element formation.
In 2017, following the detection of gravitational waves passing the Earth, ESO pointed its telescopes in Chile, including the VLT, to the source: a neutron star merger named GW170817. Astronomers suspected that, if heavier elements did form in neutron star collisions, signatures of those elements could be detected in kilonovae, the explosive aftermaths of these mergers. This is what a team of European researchers has now done, using data from the X-shooter instrument on ESO’s VLT.
Following the GW170817 merger, ESO’s fleet of telescopes began monitoring the emerging kilonova explosion over a wide range of wavelengths. X-shooter in particular took a series of spectra from the ultraviolet to the near infrared. Initial analysis of these spectra suggested the presence of heavy elements in the kilonova, but astronomers could not pinpoint individual elements until now.
“By reanalyzing the 2017 data from the merger, we have now identified the signature of one heavy element in this fireball, strontium, proving that the collision of neutron stars creates this element in the Universe,” says the study’s lead author Darach Watson from the University of Copenhagen in Denmark. On Earth, strontium is found naturally in the soil and is concentrated in certain minerals. Its salts are used to give fireworks a brilliant red color.
Astronomers have known the physical processes that create the elements since the 1950s. Over the following decades, they have uncovered the cosmic sites of each of these major nuclear forges, except one. “This is the final stage of a decades-long chase to pin down the origin of the elements,” says Watson. “We know now that the processes that created the elements happened mostly in ordinary stars, in supernova explosions, or in the outer layers of old stars. But, until now, we did not know the location of the final, undiscovered process, known as rapid neutron capture, that created the heavier elements in the periodic table.”
Rapid neutron capture is a process in which an atomic nucleus captures neutrons quickly enough to allow very heavy elements to be created. Although many elements are produced in the cores of stars, creating elements heavier than iron, such as strontium, requires even hotter environments with lots of free neutrons. Rapid neutron capture only occurs naturally in extreme environments where atoms are bombarded by vast numbers of neutrons.
“This is the first time that we can directly associate newly created material formed via neutron capture with a neutron star merger, confirming that neutron stars are made of neutrons and tying the long-debated rapid neutron capture process to such mergers,” says Camilla Juul Hansen from the Max Planck Institute for Astronomy in Heidelberg, who played a major role in the study.
Scientists are only now starting to better understand neutron star mergers and kilonovae. Because of the limited understanding of these new phenomena and other complexities in the spectra that the VLT’s X-shooter took of the explosion, astronomers had not been able to identify individual elements until now.
“We actually came up with the idea that we might be seeing strontium quite quickly after the event. However, showing that this was demonstrably the case turned out to be very difficult. This difficulty was due to our highly incomplete knowledge of the spectral appearance of the heavier elements in the periodic table,” says University of Copenhagen researcher Jonatan Selsing, who was a key author on the paper.
The GW170817 merger was the fifth detection of gravitational waves, made possible thanks to the NSF’s Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US and the Virgo Interferometer in Italy. Located in the galaxy NGC 4993, the merger was the first, and so far the only, gravitational wave source to have its visible counterpart detected by telescopes on Earth.
With the combined efforts of LIGO, Virgo and the VLT, we have the clearest understanding yet of the inner workings of neutron stars and their explosive mergers.
This research was presented in a paper published in Nature on October 23, 2019.
Reference: “Identification of strontium in the merger of two neutron stars” by Darach Watson, Camilla J. Hansen, Jonatan Selsing, Andreas Koch, Daniele B. Malesani, Anja C. Andersen, Johan P. U. Fynbo, Almudena Arcones, Andreas Bauswein, Stefano Covino, Aniello Grado, Kasper E. Heintz, Leslie Hunt, Chryssa Kouveliotou, Giorgos Leloudas, Andrew J. Levan, Paolo Mazzali and Elena Pian, 23 October 2019, Nature.
The team is composed of D. Watson (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), C. J. Hansen (Max Planck Institute for Astronomy, Heidelberg, Germany), J. Selsing (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. Koch (Center for Astronomy of Heidelberg University, Germany), D. B. Malesani (DTU Space, National Space Institute, Technical University of Denmark, & Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. C. Andersen (Niels Bohr Institute, University of Copenhagen, Denmark), J. P. U. Fynbo (Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), A. Arcones (Institute of Nuclear Physics, Technical University of Darmstadt, Germany & GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany), A. Bauswein (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany & Heidelberg Institute for Theoretical Studies, Germany), S. Covino (Astronomical Observatory of Brera, INAF, Milan, Italy), A. Grado (Capodimonte Astronomical Observatory, INAF, Naples, Italy), K. E. Heintz (Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Reykjavík, Iceland & Niels Bohr Institute & Cosmic Dawn Center, University of Copenhagen, Denmark), L. Hunt (Arcetri Astrophysical Observatory, INAF, Florence, Italy), C. Kouveliotou (George Washington University, Physics Department, Washington DC, USA & Astronomy, Physics and Statistics Institute of Sciences), G. Leloudas (DTU Space, National Space Institute, Technical University of Denmark, & Niels Bohr Institute, University of Copenhagen, Denmark), A. Levan (Department of Physics, University of Warwick, UK), P. Mazzali (Astrophysics Research Institute, Liverpool John Moores University, UK & Max Planck Institute for Astrophysics, Garching, Germany), E. Pian (Astrophysics and Space Science Observatory of Bologna, INAF, Bologna, Italy). | 0.881344 | 4.051088 |
The reason is delta-v, which is a crucial concept in Spaceflight. It means change in velocity, and is the primary 'currency' that space mission have to expend in order to reach places in the solar system. On earth, if you want to go anywhere, you can get there at any speed, it just takes longer. Unfortunately, that is not how it works in space, because the body you come from and the body you want to reach both cycle the sun at very large speeds. After getting into orbit, you need to accelerate by another 3.21 kilometers per second to escape the gravity influence of the earth completely.
In order to get to Mars from this point, you would need to accelerate another 1.06 km/s, so that the orbit of your spacecraft crosses the orbit of Mars. Alternatively, to achieve the same with Venus you would need to accelerate by only 640 meters per second. Already, it is cheaper to go to Venus than Mars, but it gets better:
As I said above, your spacecraft's orbit now crosses the orbit of your target planet in one point. However, the orbital speed is still quite different. With Mars, the spacecraft would crash right into the surface, and you need to accelerate another 4.28 kilometers per second in order to reach the surface safely*. If you went to Venus, you can enter the planet's dense atmosphere to cushion the impact. As a result, you don't need to carry any rocket fuel to make a landing.
This makes Venus a low hanging fruit. At a favorable constellation, Venus is the planetary body that takes the least delta-v to reach. That even includes our moon. Heck, it takes less delta-v to reach than geostationary orbit.
In fact, the Russian Venera Probes slammed right into the Venerean atmosphere from an interplanetary trajectory (11km/s). This caused a deceleration exceeding 300G and a heat shield temperature of 11,000 °C, but that didn't destroy those probes.
The diagram below shows different places in the solar system and rough estimates of how much delta-v you need to reach them. It all still depends on the exact constellation and the maneuver you use, so use these as ballpark estimates.
Copyright as noted in the image.
*Actually a bit less, because Mars also has some atmosphere that can help you with the landing. | 0.853734 | 3.672519 |
The only known repeating Fast Radio Bursts (FRBs) have only become more interesting by giving astronomers more clues about their home.
Fast Radio Bursts are flash-like bursts of radio energy with an extragalactic origin that only last a few milliseconds. Astronomers only know of about 30 FRBs since the discovery of the first one in 2007. They originally thought these intense bright bursts were caused by explosions, collisions, or collapses, until the first repeating FRB, FRB121102, was discovered by the Canadian Paul Scholz, while he was a PhD student at McGill University.
Last year, researchers discovered that FRB121102 is in a star-forming region of a dwarf galaxy, over 3 billion light years away from Earth. The extremely far distance of this source means that each burst contains a lot of energy, and perhaps each millisecond of these flash-like bursts contains as much energy as the Sun releases in an entire day. However, the physical nature of these FRBs remains unknown and mysterious, rendering them a hot topic in astronomy.
In a new study published in Nature, Daniele Michilli, a PhD Candidate from the University of Amsterdam and ASTRON, the Netherlands Institute for Radio Astronomy, and his international team of colleagues, present more clues about the source of the repeating FRB121102. This international team includes McGill University’s Victoria Kaspi and Shriharsh Tendulkar. At the recent American Astronomical Society meeting, the team revealed evidence for why they think FRB121102 comes from an extremely magnetic environment, suggesting that the source of this FRB is most likely located near a massive black hole.
Data from Arecibo Observatory in Puerto Rico and Green Bank Observatory in West Virginia reveal that these repeating radio bursts are highly polarized. When radio waves, or any light waves, are transmitted, they have an electric and a magnetic field. In polaridiscovering more FRBszed light, the electric field only points in one direction. “We use polarization every day, such as polarized glasses to remove annoying glare of the opposite polarization,” said Dr. Kaspi, a professor of physics at McGill University.
The team of astronomers have observed that these highly polarized radio waves are twisted, meaning that the angle of polarization changes depending on what radio frequency they are observing at. Twisted polarization is explained by the Faraday rotation, discovered by a British physicist named Michael Faraday. Faraday rotation is a magneto-optical effect caused as light travels through a magnetic environment.
“Sometimes you can have a little bit of Faraday rotation, but we saw this huge number in the units of 100,000, which you never hear of! It’s usually 10, 20, so when you say 100,000, it’s a lot,” Dr. Kaspi told SpaceQ in an interview. The huge amount of Faraday rotation is suggestive of an extreme magnetic field in a dense plasma. Previously, such highly magnetic plasmas had only been observed around a massive black hole near the center of the Milky Way.
The high Faraday rotation values of FRB121102, which show up as a twist, suggests that the source of these FRBs is located close to a massive black hole. Black holes themselves aren’t the cause of high magnetization. The region around black holes where material falls into them and gets heated to really high temperatures forms currents and jets. “A black hole alone wouldn’t have a magnetic field, but if you put stuff around it, magnetic field gets generated in them because of different plasma instabilities as they get heated so high when they fall in and towards the black hole,” says Dr. Kaspi.
Some astronomers believe that the cause of the bursts themselves are rapidly spinning neutron stars. Neutron stars are the small, dense, collapsed cores of large stars that die in supernovas. First, the neutron stars send out radio bursts, then when they propagate through magnetized regions, they get twisted. “You first need the source to make the bright radio waves, and then understand why they get twisted. You need two crazy things: a crazy neutron star to make the bursts in the first place, then the crazy black hole to cause all the rotation,” Dr. Kaspi told SpaceQ. “Neither of those crazy ideas are secure. These are hypotheses.”
Michilli and his team also speculate that the source of FRB121102 could be located in a powerful nebula or amongst the remains of a dead star, instead of close to a black hole, which could also explain the twist of these radio bursts. “It doesn’t mean that nature isn’t creative and doesn’t make magnetic fields in other areas. These FRBs could be coming from something that we don’t understand yet,” says Dr. Kaspi. What is known is that the source of these FRBs is in an extremely magnetic field, one that is at least 200 times stronger than the average magnetic field in our galaxy.
The source of FRB121102 emits a wide variety of bursts. “Every burst comes out looking different,” says Dr. Kaspi. This variation could be caused by the object that creates them, meaning the source emits each burst differently, or it could be that all bursts are emitted the same, but the signals gets distorted as they travel from the source to us.
Since FRB121102 is the only known repeating FRB, astronomers are still unsure if it shares a similar origin to the non-repeating FRBs. Although astronomers have caught a glimpse of FRB121102’s environment, the true physical nature of all discovered FRBs still remains a mystery. New telescopes could hold the answer to all of these questions. The CHIME Telescope (Canadian Hydrogen Intensity Mapping Experiment) in Penticton, British Columbia, is promising for discovering more FRBs.
Currently, the naming system for FRBs is the term “FRB” followed by the discovery date. For example, FRB121102 was discovered on November 02, 2012. Astronomers might need to change their naming system soon, since CHIME is capable of detecting multiple FRBs every day!
One of FRB 121102’s radio bursts, as detected with the Arecibo telescope. The colour panel shows the brightness of the burst as a function of radio frequency and time, whereas the curve above shows the brightness of the burst summed across all observed radio frequencies. This movie illustrates how detecting the bursts at the highest possible time resolution has been critical in resolving their complex structures. Credit: Andrew Seymour, NAIC, Arecibo. | 0.836514 | 4.04306 |
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