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Offline Orionid

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« Odpowiedź #255 dnia: Wrzesień 28, 2017, 10:12 »
The Strange Structures of the Saturn Nebula
27 September 2017 eso1731 — Photo Release

The spectacular planetary nebula NGC 7009, or the Saturn Nebula, emerges from the darkness like a series of oddly-shaped bubbles, lit up in glorious pinks and blues. This colourful image was captured by the powerful MUSE instrument on ESO’s Very Large Telescope (VLT), as part of a study which mapped the dust inside a planetary nebula for the first time. The map — which reveals a wealth of intricate structures in the dust, including shells, a halo and a curious wave-like feature — will help astronomers understand how planetary nebulae develop their strange shapes and symmetries.

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« Odpowiedź #256 dnia: Wrzesień 30, 2017, 23:35 »
Supersonic gas streams left over from the Big Bang drive massive black hole formation
September 29, 2017 Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU)

Figure 1: Projected density distributions of dark matter (background and top panel) and gas (bottom three panels) components when the massive star forms.

An international team of researchers has successfully used a super-computer simulation to recreate the formation of a massive black hole from supersonic gas streams left over from the Big Bang. Their study, published in this week’s Science, shows this black hole could be the source of the birth and development of the largest and oldest super-massive black holes recorded in our Universe.

“This is significant progress. The origin of the monstrous black holes has been a long-standing mystery and now we have a solution to it,” said author and Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) Principal Investigator Naoki Yoshida.

Recent discoveries of these super-massive black holes located 13 billion light years away, corresponding to when the universe was just five per cent of its present age, pose a serious challenge to the theory of black hole formation and evolution. The physical mechanisms that form black holes and drive their growth are poorly understood.

Theoretical studies have suggested these black holes formed from remnants of the first generation of stars, or from a direct gravitational collapse of a massive primordial gas cloud. However, these theories either have difficulty in forming super-massive black holes fast enough, or require very particular conditions.

Yoshida and JSPS Overseas Research Fellow Shingo Hirano, currently at the University of Texas at Austin, identified a promising physical process through which a massive black hole could form fast enough. The key was incorporating the effect of supersonic gas motions with respect to dark matter. The team’s super-computer simulations showed a massive clump of dark matter had formed when the universe was 100 million years old. Supersonic gas streams generated by the Big Bang were caught by dark matter to form a dense, turbulent gas cloud. Inside, a protostar started to form, and because the surrounding gas provided more than enough material for it to feed on, the star was able to grow extremely big in a short amount of time without releasing a lot of radiation.

“Once reaching the mass of 34,000 times that of our Sun, the star collapsed by its own gravity, leaving a massive black hole. These massive black holes born in the early universe continued to grow and merge together to become a supermassive black hole,” said Yoshida.

The number density of massive black holes is derived to be approximately one per a volume of three billion light-years on a side – remarkably close to the observed number density of supermassive black holes,” said Hirano.

The result from this study will be important for future research into the growth of massive black holes. Especially with the increased number of black hole observations in the far universe that are expected to be made when NASA’s James Webb Space Telescope is launched next year.

This research was published in Science on September 28.

Aterui, one of the supercomputers this work used, is operated by the Center for Computational Astrophysics (CfCA) of the National Astronomical Observatory of Japan (NAOJ).

Figure 2: Close up showing gas density distribution around a protostar (centre). The high-speed gas flowing from the top left of the image to the right compresses the central gas cloud, while the yellow to light-green areas show the development of strong turbulence.

Figure 3: Evolution of the temperature and density structure during the protostellar accretion phase. The rapid accretion of a dense gas cloud (white contour) causes the brightening of the star, and photoionized regions are lauched (red).

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« Odpowiedź #257 dnia: Październik 07, 2017, 08:01 »
Surface Helium Detonation Spells End for White Dwarf
October 4, 2017

An international team of researchers has found evidence that the brightest stellar explosions in our Universe could be triggered by helium nuclear detonation near the surface of a white dwarf star. Using Hyper Suprime-Cam mounted on the Subaru Telescope, the team detected a type Ia supernova within a day after the explosion, and explained its behavior through a model calculated using the supercomputer ATERUI.

Figure 1: A type Ia supernova detected within a day after exploding. Taken with Hyper Suprime-Cam mounted on the Subaru Telescope. Figure without the labels is linked here. (Credit: University of Tokyo/NAOJ)

Some stars end their lives with a huge explosion called a supernova. The most famous supernovae are the result of a massive star exploding, but a white dwarf, the remnant of an intermediate mass star like our Sun, can also explode. This can occur if the white dwarf is part of a binary star system. The white dwarf accretes material from the companion star, then at some point, it might explode as a type Ia supernova.

Because of the uniform and extremely high brightness (about 5 billion times brighter than the Sun) of type Ia supernovae, they are often used for distance measurements in astronomy. However, astronomers are still puzzled by how these explosions are ignited. Moreover, these explosions only occur about once every 100 years in any given galaxy, making them difficult to catch.

An international team of researchers led by Ji-an Jiang, a graduate student of the University of Tokyo, and including researchers from the University of Tokyo, the Kavli Institute for the Physics and Mathematics of the Universe (IPMU), Kyoto University, and the National Astronomical Observatory of Japan (NAOJ), tried to solve this problem. To maximize the chances of finding a type Ia supernova in the very early stages, the team used Hyper Suprime-Cam (HSC) mounted on the Subaru Telescope, a combination which can capture an ultra-wide area of the sky at once. Also they developed a system to detect supernovae automatically in the heavy flood of data during the survey, which enabled real-time discoveries and timely follow-up observations.

They discovered over 100 supernova candidates in one night with Subaru/Hyper Suprime-Cam, including several supernovae that had only exploded a few days earlier. In particular, they captured a peculiar type Ia supernova within a day of it exploding. Its brightness and color variation over time are different from any previously-discovered type Ia supernova. They hypothesized this object could be the result of a white dwarf with a helium layer on its surface. Igniting the helium layer would lead to a violent chain reaction and cause the entire star to explode. This peculiar behavior can be totally explained with numerical simulations calculated using the supercomputer ATERUI. "This is the first evidence that robustly supports a theoretically predicted stellar explosion mechanism!" said Jiang.

Figure 2: Artist’s impression of the supernova explosion. The nuclear detonation of the surface helium layer triggered an inward shock wave, and now carbon nuclear fusion has begun at the center. (Credit: University of Tokyo)

This result is a step towards understand the beginning of type Ia supernovae. The team will continue to test their theory against other supernovae, by detecting more and more supernovae just after the explosion. The details of their study are to be published in Nature on October 5, 2017 (Jiang et al. 2017, "A hybrid type la supernova with an early flash triggered by helium-shell detonation", Nature).

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« Odpowiedź #258 dnia: Październik 07, 2017, 19:10 »
Ciekawa sprawa z tym helem na powierzchni białych karłów. Nie było to już wcześniej znane? Wydawało mi się, że od dawna wiadomo, że następuje transfer materii/gazu na takiego białego karła z drugiej gwiazdy w układzie podwójnym.

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« Odpowiedź #259 dnia: Październik 10, 2017, 01:25 »
Glycolaldehyde and ethylene glycol detected around Sagittarius B2
October 9, 2017 by Tomasz Nowakowski

Color-composite image of the Galactic center and Sagittarius B2 as seen by the ATLASGAL survey. Sagittarius B2 is the bright orange-red region to the middle left of the image, which is centered on the Galactic centre. Credit: ESO/APEX & MSX/IPAC/NASA

(—Using the Shanghai Tianma 65m Radio Telescope (TMRT) a team of Chinese astronomers has detected a widespread presence of glycolaldehyde and ethylene glycol around the giant molecular cloud Sagittarius B2. The finding, presented Sept. 29 in a paper published on, could be important for studies of prebiotic molecules in the interstellar medium.

Sagittarius B2 is a giant molecular cloud of gas and dust with a mass of approximately three million solar masses spanning across 150 light years. It is located some 390 light years from the center of the Milky Way and about 25,000 light years away from the Earth. Its enormous size makes it one of the largest molecular clouds in our galaxy.

Sagittarius B2 contains various kinds of complex molecules, including alcohols like ethanol and methanol. Previous studies revealed that this cloud exhibits a weak concentration of emission of glycolaldehyde (CH2OHCHO) and ethylene glycol (HOCH2CH2OH). However, the exact extent of this emission remained unclear. Thus, a team of researchers led by Juan Li of the Shanghai Astronomical Observatory, recently conducted new observations of Sagittarius B2 that independently detected the emission of these two molecules, and provided more detailed information about this process.

The astronomers observed Sagittarius B2 with TMRT in March and November 2016. For these observations, they employed the telescope's digital backend system (DIBAS) with a total bandwidth of 1.2 GHz, and a velocity resolution of 2.0 km/s at a frequency of 13.5 GHz. The team detected widespread glycolaldehyde and ethylene glycol emission, also determining the spatial distribution of these molecules.

"We report the detection of widespread CH2OHCHO and HOCH2CH2OH emission in galactic center giant molecular cloud Sagittarius B2 using the Shanghai Tianma 65m Radio Telescope," the researchers wrote in the paper.

Glycolaldehyde is a sugar-related molecule that can react with propenal to form ribose—a central constituent of RNA.
Ethylene glycol is a dialcohol, a molecule chemically related to ethanol. New observations made by Chinese scientists show that the spatial distribution of these two prebiotic molecules around Sagittarius B2 extends over 117 light years. Notably, this extension is about 700 times greater than usually observed in clouds located in the Milky Way's spiral arms.

Furthermore, the study revealed that the abundance of glycolaldehyde and ethylene glycol decreases from the cold outer region to the central region of the cloud associated with star formation activity. According to the authors, this suggests that most of the emission is not associated with star formation and that the two studied molecules are likely to form through a low temperature process.

In concluding remarks, the researchers emphasize the necessity of additional observations of other molecules in order to determine whether some other process are also engaged in the formation of complex organic molecules in the center of the Milky Way. "Future observations of methyl formate are expected to investigate whether energetic processes also play a role in producing complex organic molecules in the Galactic center," the astronomers concluded.

More information: Widespread Presence of Glycolaldehyde and Ethylene Glycol Around Sagittarius B2, arXiv:1709.10247 [astro-ph.GA]


We report the detection of widespread CH2OHCHO and HOCH2CH2OH emission in Galactic center giant molecular cloud Sagittarius B2 using the Shanghai Tianma 65m Radio Telescope. Our observations show for the first time that the spatial distribution of these two important prebiotic molecules extends over 15 arc-minutes, corresponding to a linear size of approximately 36 pc. These two molecules are not just distributed in or near the hot cores. The abundance of these two molecules seems to decrease from the cold outer region to the central region associated with star-formation activity. Results present here suggest that these two molecules are likely to form through a low temperature process. Recent theoretical and experimental studies demonstrated that prebiotic molecules can be efficiently formed in icy grain mantles through several pathways. However, these complex ice features cannot be directly observed, and most constraints on the ice compositions come from millimeter observations of desorbed ice chemistry products. These results, combined with laboratory studies, strongly support the existence of abundant prebiotic molecules in ices.

© 2017

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« Odpowiedź #260 dnia: Październik 10, 2017, 14:02 »
Scientists discover more about the ingredients for star formation
Scientists discover more about the ingredients for star formation
Tuesday, 10 October 2017

Only hydrogen molecules are thought to directly fuel star formation but research published today shows there are more hydrogen atoms than molecules even in young galaxies that are making a lot of stars.

Astrophysicist Dr Luca Cortese, from The University of Western Australian node of the International Centre for Radio Astronomy Research, said new stars were constantly forming in the Universe.

“New stars are born in dense clouds of gas and dust that are found in most galaxies,” he said.

“Our own Milky Way forms about one new star a year on average.”

In the local Universe close to us about 70 per cent of the hydrogen gas is found in individual atoms, while the rest is in molecules.

Astronomers had expected that as they looked back in time, younger galaxies would contain more and more molecular hydrogen until it dominated the gas in the galaxy. Instead, they found that atomic hydrogen made up the majority of gas in younger galaxies too.

This is true even in galaxies under conditions similar to ‘cosmic noon’, a period about seven billion years after the Big Bang when the rate of star formation in the Universe reached its peak.

Dr Cortese said that in the last decade astronomers had discovered young, star-forming galaxies at cosmic noon with 10 times more hydrogen molecules than the Milky Way.

With such large reservoirs of molecular hydrogen, no room seemed to be left for a comparable amount of cold atomic gas. Unfortunately, it is currently impossible to detect hydrogen atoms at such large distances and verify this expectation.

Instead, Dr Cortese and his team discovered a population of galaxies three billion years younger than the Milky Way hosting gas reservoirs at least as large as those of galaxies at the cosmic noon.

“What we found is that despite hosting 10 billion solar masses of molecular gas these young galaxies turn out to be very, very rich in atomic hydrogen as well,” Dr Cortese said.

“The balance between atomic and molecular hydrogen is pretty much the same as in the Milky Way. In other words, it’s still dominated by atomic gas.”

The research used data from two of the world’s most powerful radio telescopes, the Arecibo Observatory in Puerto Rico and the European Southern Observatory’s Atacama Large Millimeter/submillimeter Array in Chile.

ICRAR astrophysicist Dr Barbara Catinella, a co-author on the research, said the findings had tremendous implications for our understanding of the early Universe.

“It shows that we cannot neglect atomic hydrogen even in galaxies that contain tens of billions of solar masses of molecular hydrogen,” she said.

“Only the advent of future radio telescopes such as the Square Kilometre Array will allow us to get a complete picture of the role of cold gas in the star formation cycle.”

A further finding from the study was that the galaxies rich in molecular hydrogen were not very turbulent.

Usually, these galaxies would be expected to be very turbulent to prevent the collapse of the gas into stars.

The research was published in The Astrophysical Journal Letters.

Original Publication:
‘ALMA reveals no change in the molecular-to-atomic hydrogen mass ratio of star-forming disks during the past three billion years.’, published in The Astrophysical Journal Letters on October 10th, 2017. Available via

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« Odpowiedź #261 dnia: Październik 10, 2017, 19:29 »
Two separate teams of astronomers find evidence of missing Baryonic matter
October 10, 2017 by Bob Yirka

Credit: CC0 Public Domain

(—Two teams working independently have found evidence of the existence of Baryonic matter—particles that link galaxies together. One team was made of members from the Institute of Space Astrophysics, the other was based out of the University of Edinburgh. Both teams have uploaded a paper describing their work to the arXiv preprint server and both are claiming their findings solve the mystery of where so much of the normal matter—protons, neutrons and electrons—in the universe has been hiding.

Once scientists came up with the Big Bang Theory, a problem immediately arose—after calculating how much normal matter should exist in the universe at this point in time, they found approximately 50 percent of it is missing. Since then, scientists have worked on theories to explain where all that matter was hiding—the prevailing theory suggests that it exists as strands of Baryonic matter floating in the space between galaxies and cannot be seen with conventional instruments—this was the theory both teams in this new effort tested.

To get around the problem of not being able to see the Baryonic matter directly, the researchers considered a phenomenon called the Sunyaev-Zel'dovich effect in which light left over from the Big Bang scatters as it passes through hot gas—it should be measurable in the cosmic microwave background. Both teams used data from the Planck satellite launched two years ago to create a map of where Baryonic matter strands might exist. Each selected a pair of galaxies to study, focusing on the space between them. Then, they stacked data from between the two galaxies to magnify data believed to be from Baryonic matter.

Both teams repeated this process for multiple pairs of galaxies to show that their readings were consistent across multiple test sites—one team tested a million pairs, the other 260,000. Both report finding evidence of the theorized filaments between the galaxies. One group found them to be three times as dense as the mean of observable matter, the other group six times—a difference that was expected, the groups explain, due to differences in distances from the galaxies that were studied.

Journal reference: arXiv 
© 2017

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« Odpowiedź #262 dnia: Październik 12, 2017, 21:01 »
Devourer of planets? Princeton researchers dub star ‘Kronos’
Liz Fuller-Wright, Office of Communications
Oct. 12, 2017 1 p.m.

In mythology, the Titan Kronos devoured his children, including Poseidon (better known as the planet Neptune), Hades (Pluto) and three daughters.

So when a group of Princeton astronomers discovered twin stars, one of which showed signs of having ingested a dozen or more rocky planets, they named them after Kronos and his lesser-known brother Krios. Their official designations are HD 240430 and HD 240429, and they are both about 350 light years from Earth.

The keys to the discovery were first confirming that the widely separated pair are in fact a binary pair, and secondly observing Kronos’ strikingly unusual chemical abundance pattern, explained Semyeong Oh, a graduate student in astrophysical sciences who is lead author on a new paper describing Kronos and Krios. Oh works with David Spergel, the Charles A. Young Professor of Astronomy on the Class of 1897 Foundation and director of the Flatiron Institute’s Center for Computational Astrophysics.

Other co-moving star pairs have had different chemistries, Oh explained, but none as dramatic as Kronos and Krios.

Most stars that are as metal-rich as Kronos “have all the other elements enhanced at a similar level,” she said, “whereas Kronos has volatile elements suppressed, which makes it really weird in the general context of stellar abundance patterns.”

In other words, Kronos had an unusually high level of rock-forming minerals, including magnesium, aluminum, silicon, iron, chromium and yttrium, without an equally high level of volatile compounds — those that are most often found in gas form, like oxygen, carbon, nitrogen and potassium.

Kronos is already outside the galactic norm, said Oh, and in addition, “because it has a stellar companion to compare it to, it makes the case a little stronger.”

Kronos and Krios are far enough apart that some astronomers have questioned whether the two were in fact a binary pair. Both are about 4 billion years old, and like our own, slightly older sun, both are yellow G-type stars. They orbit each other infrequently, on the order of every 10,000 years or so. An earlier researcher, Jean-Louis Halbwachs of the Observatoire Astronomique of Strasbourg, had identified them as co-moving — moving together — in his 1986 survey, but Oh independently identified them as co-moving based on two-dimensional astrometric information from the European Space Agency’s Gaia mission.

During a group research discussion at the Flatiron Institute, a colleague suggested pooling their data sets. John Brewer, a postdoctoral researcher from Yale University visiting at Columbia University, had been using data from the Keck Observatory on Mauna Kea, Hawaii, to calculate the spectrographic chemistries and radial velocities of stars.

“John suggested that maybe we should cross-match my co-moving catalogue with his chemical-abundance catalogue, because it’s interesting to ask whether they have the same compositions,” Oh said.

Binary stars should have matching radial velocities, but that information hadn’t been available in the Gaia dataset, so seeing their matching velocities in Brewer’s data supported the theory that Kronos and Krios, though two light years apart, were a binary set.

Then the researchers noticed the extreme chemical differences between them.

“I’m very easily excitable, so as soon as they had the same radial velocities and different chemistry, my mind already started racing,” said Adrian Price-Whelan, a Lyman Spitzer, Jr. Postdoctoral Fellow in Astrophysical Sciences and a co-author on the paper.

Oh took more convincing, both scientists recalled. “Semyeong is careful and was skeptical,” said Price-Whelan, so her first step was to double-check all the data. Once simple error had been ruled out, they began entertaining various theories. Maybe Kronos and Krios had accreted their planetary disks at different times during stellar formation. That one can’t be tested, said Price-Whelan, but it seems unlikely.

Maybe they only started moving together more recently, after trading partners with another pair of binary stars, a process known as binary exchange. Oh ruled that out with “a simple calculation,” she said. “She’s very modest,” Price-Whelan noted.

Stars HD 240430 and HD 240429, better known as Kronos and Krios, as they appear in the Space Telescope Science Institute’s Digitized Sky Survey. Though these binary stars formed together, their chemical abundances are very different, leading researchers to conclude that Kronos had absorbed 15 Earth masses worth of rocky planets.
Image courtesy of the researchers

She immediately observed that all of the minerals that solidify below 1200 Kelvin were the ones Kronos was low in, while all the minerals that solidify at warmer temperatures were abundant.

“Other processes that change the abundance of elements generically throughout the galaxy don’t give you a trend like that,” said Price-Whelan. “They would selectively enhance certain elements, and it would appear random if you plotted it versus condensation temperatures. The fact that there’s a trend there hinted towards something related to planet formation rather than galactic chemical evolution.”

That was her “Aha!” moment, Oh said. “All of the elements that would make up a rocky planet are exactly the elements that are enhanced on Kronos, and the volatile elements are not enhanced, so that provides a strong argument for a planet engulfment scenario, instead of something else.”

Oh and her colleagues calculated that gaining this many rock-forming minerals without many volatiles would require engulfing roughly 15 Earth-mass planets.

Eating a gas giant wouldn’t give the same result, Price-Whelan explained. Jupiter, for example, has an inner rocky core that could easily have 15 Earth masses of rocky material, but “if you were to take Jupiter and throw it into a star, Jupiter also has this huge gaseous envelope, so you’d also enhance carbon, nitrogen — the volatiles that Semyeong mentioned,” he said. “To flip it around, you have to throw in a bunch of smaller planets.”

While no known star has 15 Earth-sized planets in orbit around it, the Kepler space telescope has detected many multi-planet systems, said Jessie Christiansen, an astronomer at the NASA Exoplanet Science Institute at the California Institute of Technology, who was not involved in the research. “I see no problem with there being more than 15 Earth masses of accretable material around a solar-type star.” She pointed to Kepler-11, which has more than 22 Earth masses of material in six planets with close orbits, or HD 219134, which has at least 15 Earth masses of material in its inner four planets.

“At the moment, we are still at the stage of piecing together different observations to determine how and when exoplanets form,” said Christiansen. “It’s difficult to directly observe planet formation around young stars — they are typically shrouded in dust, and the stars themselves are very active, which makes it hard to disentangle any signals from the planets. So we have to infer what we can from the limited information we have. If borne out, this new window onto the masses and compositions of the material in the early stages of planetary systems may provide crucial constraints for planet formation theories.”

The research also has implication for stellar formation models, noted Price-Whelan.

“One of the common assumptions — well-motivated, but it is an assumption — that’s pervasive through galactic astronomy right now is that stars are born with [chemical] abundances, and they then keep those abundances,” he said. “This is an indication that, at least in some cases, that is catastrophically false.”

The Flatiron Institute is the intramural research division of the Simons Foundation. This work has made use of data from the European Space Agency mission Gaia, processed by the Gaia Data Processing and Analysis Consortium, which is funded by the institutions participating in the Gaia Multilateral Agreement. This work also used data products from the Two Micron All Sky Survey, a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, (Caltech), funded by the National Aeronautics and Space Administration (NASA) and the National Science Foundation. This research made use of data products from the Wide-field Infrared Survey Explorer, a joint project of the University of California-Los Angeles, and the Jet Propulsion Laboratory/Caltech, funded by NASA.

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« Odpowiedź #263 dnia: Październik 12, 2017, 22:16 »
Scientists Discover One of the Most Luminous 'New Stars' Ever
Published: October 11, 2017.
Released by University of Leicester 

Astronomers have today announced that they have discovered possibly the most luminous 'new star' ever - a nova discovered in the direction of one of our closest neighboring galaxies: The Small Magellanic Cloud.

Astronomers from the University of Leicester contributed to the discovery by using the Swift satellite observatory to help understand what was likely the most luminous white dwarf eruption ever seen.

A nova happens when an old star erupts dramatically back to life. In a close binary star system consisting of a white dwarf[1] and a Sun-like companion star, material is transferred from the companion to the white dwarf, gradually building up until it reaches a critical pressure. Then uncontrolled nuclear burning occurs, leading to a sudden and huge increase in brightness. It is called a nova because it appeared to be a new star to the ancients.

Novae are usually found in visible light, but often go on to emit higher energy X-rays as well. Together, these different datasets provide information on the white dwarf, such as its temperature and chemical composition.

Using telescopes from South Africa to Australia to South America, as well as the orbiting Swift observatory, a team led by the South African Astronomical Observatory has revealed that the nova SMCN 2016-10a, which was discovered on 14th October 2016, is the most luminous nova ever discovered in the SMC, and one of the brightest ever seen in any galaxy. The observations that they made are the most comprehensive ever for a nova in this galaxy.

The SMC, 200,000 light-years away, is one of our closest companion galaxies; it is a dwarf galaxy, very much less massive than our own. Novae occur frequently in our Galaxy, with a rate of around 35 each year, but SMCN 2016-10a is the first nova to have been detected in the SMC since 2012.

Dr Kim Page, a member of the Swift team at the University of Leicester, led the X-ray analysis, while Paul Kuin, from the Mullard Space Science Laboratory, University College London, organised the UV data.

Dr Page said: "Swift's ability to respond rapidly, together with its daily-planned schedule, makes it ideal for the follow-up of transients, including novae. It was able to observe the nova throughout its eruption, starting to collect very useful X-ray and UV data within a day of the outburst first being reported. The X-ray data were essential in showing that the mass of the white dwarf is close to the theoretical maximum; continued accretion might cause it eventually to be totally destroyed in a supernova explosion."

Dr Kuin added:"The present observations provide the kind of coverage in time and spectral colour that is needed to make progress for gaining understanding of a nova in a neighbouring galaxy. Observing the nova in different wavelengths using world-class telescopes such as Swift and the Southern African Large Telescope help us reveal the condition of matter in nova ejecta as if it were nearby."

Professor Julian Osborne, who leads the Swift team at the University of Leicester, and was also involved in this study, said: "Although it is difficult to measure the distance to novae directly, its position in the SMC on the sky, and everything else we know about this nova point to it being in this dwarf galaxy. This makes the nova as intrinsically bright as the most luminous ever seen, and thus very interesting in trying to understand these explosions."

Zaobserwowano jedną z najjaśniejszych w historii gwiazd nowych

Niezwykle jasną gwiazdę nową zaobserwowali fizycy w jednej z najbliższych galaktyk – Małym Obłoku Magellana. Poinformowało o tym South African Astronomical Observatory (SAAO). W obserwacjach mają udział polscy astronomowie z projektu OGLE.

Wybuch gwiazdy nowej zachodzi, gdy w ciasnym podwójnym układzie gwiazd, składającym się z białego karła i gwiazdy takiej jak Słońce, zachodzi transfer materii na białego karła. Gdy osiągnięte zostaną warunki krytyczne, na powierzchni białego karła następuje wybuch termojądrowy. W efekcie następuje nagłe pojaśnienie gwiazdy. Wybuch nie niszczy systemu i cały proces może kiedyś się powtórzyć. Nazwę "nowa" dla tego typu zjawisk nadano, gdyż dawnym astronomom wydawało się, że na niebie pojawiła się nowa gwiazda, której wcześniej nie dostrzegali.
Międzynarodowy zespół naukowców wykorzystał w swoich obserwacjach teleskopy w RPA, Australii i Ameryce Południowej, także kosmiczne obserwatorium Swift. Wykorzystano dane z polskiego projektu OGLE, prowadzonego przez Uniwersytet Warszawski, którego teleskop znajduje się w Chile. Gwiazda była monitorowana przez OGLE od 2010 roku, dzięki czemu można było określić jej własności sprzed wybuchu.
Gwiazdę nową odkryto 14 października 2016 r. dzięki teleskopowi sieci MASTER, znajdującemu się w Argentynie. Oznaczono ją SMCN 2016-10a, gwiazda szybko przyciągnęła uwagę astronomów z całego świata. Jest to najjaśniejsza nowa dostrzeżona w Małym Obłoku Magellana i jedna najjaśniejszych w ogóle odnotowanych w historii. W maksimum blasku była co najmniej tak jasna, jak Nova CP Pup oraz V1500 Cyg – dwie najjaśniejsze odnotowane nowe.
Mały Obłok Magellana to niewielka galaktyka odległa o około 200 tysięcy lat świetlnych do Drogi Mlecznej. Ma dużo mniejszą masę niż Droga Mleczna. Przy czym o ile w naszej Galaktyce nowe odnotowuje się w tempie około 35 obiektów w ciągu roku, to w przypadku Małego Obłoku Magellana jest to pierwsza nowa od 2012 roku.
Naukowcom udało się przeanalizować dane z różnych zakresów długości fali, w świetle widzialnym, w zakresie ultrafioletowym, a także rentgenowskim. Analizowano dane fotometryczne, spektroskopowe, badano także polaryzację światła.
Wyniki badań opisano w artykule, który ukaże się w "Monthly Notices of Royal Astronomical Society". Wśród autorów publikacji znajdziemy dwa polskie nazwiska: Przemysław Mróz oraz Andrzej Udalski z Obserwatorium Astronomicznego Uniwersytetu Warszawskiego. Pierwszą autorem pracy jest Elias Aydi, doktorant z South African Astronomical Observatory (SAAO) i University of Cape Town (UCT). (PAP)
Nauka w Polsce,460098,zaobserwowano-jedna-z-najjasniejszych-w-historii-gwiazd-nowych.html
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Odp: Astrofizyka - Badania różne (zbiorczo)
« Odpowiedź #264 dnia: Październik 13, 2017, 01:59 »
Algorytmy wykorzystywane do modelowania  pracy helikopterów okazały się pomocne  w badaniach dotyczących powstawania struktur kosmicznych.

A better understanding of space — via helicopter
By Jim Sheltonoctober 12, 2017

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An algorithm that helps engineers design better helicopters may help astronomers more precisely envision the formation of planets and galaxies.

Yale researchers Darryl Seligman and Greg Laughlin have created a new model for understanding how black holes, planets, and galaxies emerge from the vortex-rich environments of space. They drew inspiration from a mechanical engineering algorithm that shows how air flows past a helicopter’s rotor blades.(...)
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« Odpowiedź #265 dnia: Październik 13, 2017, 02:13 »
Astronomers discover unusual spindle-like galaxies 
October 12, 2017

Galaxies are majestic, rotating wheels of stars? Not in the case of the spindle-like galaxies studied by Athanasia Tsatsi (Max Planck Institute for Astronomy) and her colleagues. Using the CALIFA survey, the astronomers found that these slender galaxies, which rotate along their longest axis, are much more common than previously thought. The new data allowed the astronomers to create a model for how these unusual galaxies probably formed, namely out of a special kind of merger of two spiral galaxies. The results have been published in the journal Astronomy & Astrophysics.

An elliptical galaxy in prolate rotation. The galaxy resembles the shape of a cigar, with its stars rotating around the ... [more] Image: J. Chang, PMO / T. Müller, HdA

When most people think of galaxies, they think of majestic spiral galaxies like that of our home galaxy, the Milky Way: billions of stars, rotating in a flat disk similar to the way that a wheel rotates around its central axis. But there is another kind of galaxy, which used to be thought very rare: so-called prolate rotators, each shaped like a cigar, which rotates along its long axis, like a spindle.

Now, a group of astronomers led by Athanasia Tsatsi of the Max Planck Institute for Astronomy has completed a thorough study of these cosmic spindles. Using data from the CALIFA survey, a systematic study that examined the velocity structure of more than 600 galaxies, the astronomers discovered eight new prolate rotating galaxies, almost doubling the total known number of such galaxies (from 12 to 20). Cosmic spindles are considerably less rare than astronomers had thought!

Given the high quality of their data, the astronomers were able to propose a plausible explanation for how these cosmic spindles come into existence. In general, galaxies grow when they merge with other galaxies. Several mergers with smaller galaxies have made our own Milky Way the stately disk it is today. To make a cosmic spindle, two large disk galaxies need to collide at right angles, as shown in this animation:

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Movie: J. Chang, PMO / T. Müller, HdA
The formation of an elliptical galaxy in prolate rotation. The mechanism shown here was proposed by Athanasia Tsatsi and her colleagues in order to explain the recent discoveries of galaxies of this kind with the CALIFA survey. The formation involves a polar merger of two spiral galaxies. One of the spiral galaxies develops a marked elongated structure (a "bar," to use the technical term) before the merger, which gives the resulting elliptical galaxy its cigar-like (prolate) shape. The stars of the second spiral galaxy end up orbiting around the bar of the first companion. Together they form a cigar-shaped elliptical galaxy that rotates like a spindle around its long axis.

As the galaxies begin to interact via gravitational attraction, one of them forms a bar: an elongated structure near the center. That bar becomes the cigar-like shape of the merged galaxy, while the orbiting stars of the other galaxy imbue the merged galaxy with its overall sense of rotation.

The results are an interesting piece of the puzzle, explaining a likely formation scenario for an unusual, but not all that uncommon type of galaxy. Tsatsi's team of researchers having put to good use all the information contained in the CALIFA data, the ball is now in the court of the observing astronomers again: the merger simulations make some additional predictions for the detailed properties of prolate rotators. These cannot be distinguished with the current  observations, but could be tested with instruments like MUSE, the Multi Unit Spectral Explorer at ESO's Very Large Telescope, an 8-meter-telescope at Paranal Observatory in Chile.

Background information

The results here will be published in the journal Astronomy & Astrophysics as Tsatsi et al., "CALIFA reveals prolate rotation in massive early-type galaxies: A polar galaxy merger origin?"

Link to Online Version of the article:
The team members are Athanasia Tsatsi, Glenn van de Ven, and Andrea V. Macciò (also New York University Abu Dhabi) in collaboration with Mariya Lyubenova (University of Groningen, Netherland, now at ESO), J. Chang (Purple Mountain Observatory, Nanjing, China), J. A. L. Aguerri and J. Falcón-Barroso (both Instituto de Astrofísica de Canarias and Universidad de La Laguna, Tenerife, Spain).

Calar Alto Observatory was founded in 1979 and is located in Andalusia, Spain. It is operated jointly by the Max Planck Institute for Astronomy (MPIA) and the Astrophysical Institute of Andalusia (IAA-CSIC, Granada, Spain). The Observatory has granted 250 observing nights over the course of three years, using the 3.5 metre telescope for the CALIFA survey. This project is a joint effort of more than 80 scientists from 25 different research institutes in 13 different countries world wide.

The integral field spectrograph used for the CALIFA survey at Calar Alto Observatory, PMAS (in a special configuration called PPAK), uses more than 350 optical fibres to cover a field of view of one square arcminute (equivalent to the apparent size of a 1 euro coin placed at a distance of approximately 80 metres). This allows a complete extended object, such as a galaxy, to be fully mapped in detail in just one exposure.

For the CALIFA survey, care has been taken to select the possible observation targets at random from the overall population of galaxies. In that way, the galaxies under study should be representative of the whole: Statistical conclusions from the analysis of their data should thus allow astronomers to draw conclusions about local galaxies in general.

The CALIFA member institutions are: Astrophysical Institute, Academy of Sciences of the Czech Republic, Prague; Australian Astronomical Observatory, Australia; Centro Astronómico Hispano Alemán, Spain; Centro de Astrofísica da Universidade do Porto, Portugal; Institut d'Astrophysique de Paris, France; Instituto de Astrofisica de Andalucia, Spain; Instituto de Astrofisica de Canarias, Spain; Instituto de Física de Cantabria, Spain; Laboratoire d'Astrophysique de Marseille, France; Leibniz Institut für Astrophysik, Potsdam, Germany; Max Planck Institute for Astronomy, Heidelberg, Germany; Observatoire de Paris, France; Peking University – Kavli Institute for Astronomy and Astrophysics, China; Royal Military College of Canada, Canada; Tianjin Normal University, China; Universidad Autónoma de Madrid, Spain; Universidad de Complutense de Madrid, Spain; Universidad de Granada, Spain; Universidad de Zaragoza, Spain; University of Bochum, Germany; University of Cambridge, UK; University of Copenhagen – Dark Cosmology Centre, Denmark; University of Edingurgh, UK; University of Groningen – Kapteyn Astronomical Institute, The Netherlands; University of Heidelberg – Landessternwarte Königstuhl, Germany; University of Lisbon, Portugal; University of Missouri-Kansas City, USA; University of Porto, Portugal; University of Sidney, Australia; University of Vienna, Austria

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« Odpowiedź #266 dnia: Październik 13, 2017, 02:24 »
Badanie odległości do innych gwiazd w Galaktyce pozwoli poznać dokładnie jej kształt

VLBA measurement promises complete picture of Milky Way
October 12, 2017

Eastern end of the Very Long Baseline Array (VLBA), St. Croix, U.S. Virgin Islands. Credit: VLBA

(...) The new VLBA observations, made in 2014 and 2015, measured a distance of more than 66,000 light-years to a star-forming region called G007.47+00.05 on the opposite side of the Milky Way from the Sun, well past the Galaxy's center, some 27,000 light-years distant. The previous record for a parallax measurement was about 36,000 light-years.

"Most of the stars and gas in our Galaxy are within this newly-measured distance from the Sun. With the VLBA, we now have the capability to measure enough distances to accurately trace the Galaxy's spiral arms and learn their true shapes," Sanna said. (...)

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« Odpowiedź #267 dnia: Październik 14, 2017, 08:59 »
Astronomers find potential solution into how planets form
13 October 2017

V1247 Orionis, a young, hot star surrounded by a dynamic ring of gas and dust, known as a circumstellar disc.

The quest to discover how planets found in the far reaches of the universe are born has taken a new, crucial twist.

A new study by an international team of scientists, led by Stefan Kraus from the University of Exeter, has given a fascinating new insight into one of the most respected theories of how planets are formed.

Young stars start out with a massive disk of gas and dust that over time, astronomers think, either diffuses away or coalesces into planets and asteroids.

However, scientists are still searching for a complete understanding of how these early formations come together to form asteroid-sized objects. One reason has been that drag in the disk produced by surrounding gas makes the grains move inward toward the star – which can in turn deplete the disk rapidly in a process known as “radial drift.”

In the new research, the team use high powered telescopes to target the star V1247 Orionis -, a young, hot star surrounded by a dynamic ring of gas and dust.

The team produced a detailed image of the star and its surrounding dust disc, shown in two parts: a clearly defined central ring of matter and a more delicate crescent structure located further out.

The region between the ring and crescent, visible as a dark strip, is thought to be caused by a young planet carving its way through the disc. As the planet moves around in its orbit, its motion creates areas of high pressure on either side of its path, similar to how a ship creates bow waves as it cuts through water.

These areas of high pressure could become protective barriers around sites of planet formation; dust particles are trapped within them for millions of years, allowing them the time and space to clump together and grow.
Professor Kraus said: “The exquisite resolution of ALMA allowed us to study the intricate structure of such a dust-trapping vortex for the first time. The crescent in the image constitutes a dust trap that formed at the outer edge of the dark strip.   
“It also reveals regions of excess dust within the ring, possibly indicating a second dust trap that formed inside of the putative planet’s orbit. This confirms earlier computer simulations that predicted that dust traps should form both at the outer edge and inner edge of disc gaps.

“Dust trapping is one potential solution to a major stumbling block in our theories of how planets form, which predicts that particles should drift into the central star and be destroyed before they have time to grow to planetesimal sizes.”
Dust-trapping vortices and a potentially planet-triggered spiral wake in the pre-transitional disk of V1247 Orionis is published in Astrophysical Journal Letters.