The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 376 2014 May 25 Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is Britain's liveliest astronomical society, with members all over the world. We accept subscription payments online at our secure site and can take credit and debit cards. You can join or renew via a secure server or just see how much we have to offer by visiting http://www.popastro.com/ ASTRONOMERS FIND SUN'S SIBLING University of Texas at Austin A team of researchers has identified the first 'sibling' of the Sun -- a star that was almost certainly born from the same cloud of gas and dust as our star. It is called HD 162826, a star 15% more massive than the Sun, located 110 light-years away in the constellation Hercules. The star is not visible to the unaided eye, but can easily be seen with low-power binoculars, not far from Vega. The team identified HD 162826 as the Sun's sibling from among 30 candidates found by several groups around the world looking for solar siblings. It studied 23 of those stars by high-resolution spectroscopy with the 107-inch telescope at McDonald Observatory, and the remaining stars (visible only from the southern hemisphere) with the Clay Magellan Telescope at Las Campanas Observatory in Chile. In addition to chemical analysis, the team also included information about the stars' orbits -- their paths around the centre of the Milky Way galaxy. Combining information on both chemical make-up and dynamics of the candidates narrowed the field down to one: HD 162826. By coincidence, that star has been studied by the McDonald Observatory Planet Search team for more than 15 years. The studies have ruled out any 'hot Jupiters' -- massive planets orbiting close to the star -- and indicate that it is unlikely that a Jupiter analogue orbits the star, either, but they do not rule out the presence of smaller terrestrial planets. While the finding of a single solar sibling is intriguing, the project is also a preparatory exercise in how to identify solar siblings, in preparation for the flood of data expected soon from surveys like Gaia. The idea is that the Sun was born in a cluster with a thousand or a hundred thousand stars, which formed more than 4500 million years ago and has since broken up. The member stars have dispersed into their own orbits around the Galactic Centre, taking them to different parts of the Milky Way today. A few, like HD 162826, are still nearby. The data coming soon from Gaia are not going to be limited to the solar neighbourhood since Gaia will provide accurate distances and proper motions for a (US) billion (10*9) stars, allowing astronomers to search for solar siblings all the way to the centre of our Galaxy. The number of stars that we can study will increase by a factor of 10,000. Astronomers can concentrate on certain key chemical elements, ones whose abundances vary greatly among stars which otherwise have very similar chemical compositions and depend on where in the Galaxy the star formed. The team has identified the elements barium and yttrium as particularly useful. Once many more solar siblings have been identified, astronomers will be one step closer to knowing where and how the Sun formed. To reach that goal, the dynamics specialists will try to make models that run the orbits of solar siblings backward in time, to find where they intersect: their birthplace. JUPITER'S GREAT RED SPOT SHRINKS Space Telescope Science Institute (STScI) Jupiter's Great Red Spot -- a swirling anticyclonic storm feature larger than the Earth -- has shrunk to the smallest size ever measured. Astronomers have followed its shrinkage since the 1930s. Historic observations as far back as the late 1800s gauged the GRS to be as much as 25,500 miles on its long axis. The Voyager 1 and Voyager 2 flybys of Jupiter in 1979 measured it at 14,500 miles across. Starting in 2012, amateur observations revealed a noticeable acceleration in the spot's shrinkage rate. The GRS's 'waistline' is getting smaller by 580 miles per year and is now 10,250 miles. The shape of the GRS has changed from an oval to a circle. The cause has yet to be explained. In new observations it is apparent that very small eddies are feeding into the storm, and astronomers hypothesize that they may be responsible for the sudden change by altering the internal dynamics and energy of the Great Red Spot. Researchers plan to study the motions of the small eddies and also the internal dynamics of the GRS to determine if the eddies can feed or sap momentum entering the upwelling vortex. LENGTH OF EXOPLANET DAY MEASURED ESO Observations from the Very Large Telescope (VLT) have, for the first time, determined the rotation rate of an exoplanet, from the rotational broadening of its spectral lines. The planet orbits the naked-eye star Beta Pictoris, which lies about 63 light-years from the Earth in the southern constellation Pictor. It was discovered nearly six years ago and was one of the first exoplanets to be directly imaged. It orbits its host star at a distance of eight times the Earth-Sun distance, making it the closest exoplanet to its star to be directly imaged. Its equator is moving at almost 100 000 km/h. For comparison, Jupiter's equator has a speed of about 47 000 km/h, while the Earth's is only 1700 km/h. Beta Pictoris b is more than 16 times larger and 3000 times more massive than the Earth, yet a day on the planet lasts only 8 hours. It is not known why planets spin at different rates, but this first measurement of an exoplanet's rotation is consonant with the trend seen in the Solar System, where the more massive planets spin faster. Beta Pictoris b is a very young planet, only about 20 million years old (compared to 4.5 billion years for the Earth). Over time, the exoplanet is expected to cool and shrink, which will make it spin even faster. On the other hand, other processes might be at play that change its spin. For instance, the spin of the Earth is slowing down owing to tidal interaction with the Moon. NEAREST 'HYPER-VELOCITY STAR' FOUND University of Utah Astronomers have discovered a 'hyper-velocity star' that is the closest, second-brightest and among the largest of 20 found so far. Hypervelocity stars appear to be former components of binary stars that once orbited each other but got too close to the supermassive black hole at the Galaxy's centre. The gravity of the black hole -- which has the mass of 4 million Suns -- captures one star so it orbits the hole closely, and ejects the other on a trajectory headed beyond the Galaxy. The new hypervelocity star was discovered with the 'Large Sky Area Multi-Object Fibre Spectroscopic Telescope, or LAMOST, located at the Xinglong Observing Station of the National Astronomical Observatories of China, about 110 miles northeast of Beijing. LAMOST has a 7-m aperture and has 4,000 optical fibres, which capture spectra of as many as 4,000 stars at once. The star -- named LAMOST-HVS1 -- stood out because its speed is about 600 km/s relative to the Solar System (500 km/s with respect to the centre of the Milky Way). Despite being the closest hypervelocity star, it is nonetheless 13 kpc (42,000 light years) from the Earth. It has a magnitude of about 13, and is nine times the mass of the Sun, rather less than another hypervelocity star, HD 271791, which was discovered in 2008 and is 11 times the mass of the Sun. As seen from the Earth, among the hypervelocity stars only HD 271791 is brighter than LAMOST-HVS1. A cluster of known hypervelocity stars, including the new one, is located above the disc of our Milky Way galaxy, and their distribution in the sky suggests that they originated near the Galaxy's centre. MAGNETAR FORMATION SOLVED? ESO Magnetars are the bizarre super-dense remnants of supernova explosions. They are the strongest magnets known in the Universe -- millions of times more powerful than the strongest magnets on Earth. A team of astronomers using the Very Large Telescope (VLT) now believes it has found the partner star of a magnetar for the first time. The discovery helps to explain how magnetars form -- a conundrum dating back 35 years -- and why that particular star did not collapse into a black hole as astronomers might expect. When a massive star collapses under its own gravity during a supernova explosion it forms either a neutron star or black hole. Magnetars are an unusual form of neutron star. They are tiny and extraordinarily dense -- a teaspoonful of neutron-star material would have a mass of about a billion tons -- but they also have extremely powerful magnetic fields. Magnetar surfaces release vast quantities of gamma rays when they undergo a sudden adjustment known as a starquake as a result of the huge stresses in their crusts. The Westerlund 1 star cluster, 16 000 light-years away in the southern constellation of Ara, hosts one of the two dozen magnetars known in the Milky Way. It is called CXOU J164710.2-455216 and it has greatly puzzled astronomers. Earlier work showed that it must have been born in the explosive death of a star about 40 times as massive as the Sun. But that presents its own problem, since stars so massive are expected to collapse to form black holes after their deaths, not neutron stars. Researchers did not understand how it could have become a magnetar. A possible solution was that the magnetar formed through the interactions of two very massive stars orbiting one another in a binary system so compact that it would fit within the orbit of the Earth around the Sun. But, up to now, no companion star was detected at the location of the magnetar in Westerlund 1, so astronomers used the VLT to search for it in other parts of the cluster. They hunted for runaway stars -- objects escaping the cluster at high velocities -- that might have been ejected by the supernova explosion that formed the magnetar. One star, known as Westerlund 1-5, was found to be doing just that. Not only does it have the high velocity expected if it is recoiling from a supernova explosion, but the combination of its low mass, high luminosity and carbon-rich composition appear impossible to replicate in a single star -- a 'smoking gun' that suggests that it must have originally formed with a binary companion. That discovery allowed the astronomers to reconstruct the stellar life story that permitted the magnetar to form, in place of the expected black hole. In the first stage of that process, the more massive star of the pair begins to run out of fuel, transferring its outer layers to its less massive companion (which is destined to become the magnetar), causing it to rotate more and more quickly. Rapid rotation appears to be the essential ingredient in the formation of the magnetar's ultra-strong magnetic field. In the second stage, as a result of the mass transfer, the companion itself becomes so massive that it in turn sheds a large amount of its recently-gained mass. Much of that mass is lost but some is passed back to the original star that we still see shining today as Westerlund 1-5. It is that process of swapping material that has imparted the unique chemical signature to Westerlund 1-5 and allowed the mass of its companion to fall to low enough levels that a magnetar was born instead of a black hole. It seems that being a component of a double star may therefore be an essential ingredient in the recipe for forming a magnetar. The rapid rotation created by mass transfer between the two stars appears necessary to generate the ultra-strong magnetic field and then a second mass-transfer phase allows the magnetar-to-be to slim down sufficiently so that it does not collapse into a black hole at the moment of its death. ENTIRE STAR CLUSTER THROWN OUT OF ITS GALAXY Harvard-Smithsonian Center for Astrophysics The galaxy M87 has thrown an entire star cluster towards us at more than 1000 km/s. Astronomers have found runaway stars before, but this is the first time they have found a runaway star cluster. The newly discovered cluster has been named HVGC-1; the acronym stands for 'hypervelocity globular cluster'. Globular clusters are relics of the early Universe. Such groupings usually contain thousands of stars crammed into a ball a few dozen light-years across. The Milky Way galaxy has about 150 globular clusters, but the giant elliptical galaxy M87 has thousands. It took a stroke of luck to find HVGC-1. The discovery team has been studying the space around M87. It first sorted objects by colour to separate stars and galaxies from globular clusters. Then it used the Hectospec instrument on the MMT in Arizona to examine hundreds of globular clusters in detail. A computer automatically analyzed the data and calculated the speed of every cluster. Any oddities were examined by hand and most of them turned out to be glitches, but HVGC-1 was different -- its surprisingly high velocity was real. Astronomers are not sure how HVGC-1 was ejected at such a high speed but say that one scenario depends on M87 having a pair of supermassive black holes at its core. The star cluster passed too close to those black holes. Many of its outer stars were plucked off, but the dense core of the cluster remained intact and was flung away at tremendous speed. HVGC-1 is moving so fast that it will escape from M87 altogether. In fact, it may have already left the galaxy and be sailing out into intergalactic space. NEARBY GALAXY IS A 'FOSSIL' FROM THE EARLY UNIVERSE Carnegie Institution A team of scientists has analyzed the chemical elements in the faint galaxy called Segue 1, and determined that it is effectively a fossil galaxy left over from the early Universe. Astronomers hoping to learn about the first stages of galaxy formation after the Big Bang use the chemical compositions of stars to help them unravel the histories of the Milky Way and other nearby galaxies, and were able to categorize Segue 1's uniquely ancient composition. Stars form from gas clouds, and their composition mirrors the chemical composition of the gas from which they were born. Only a few million years after stars begin burning, the most-massive stars explode in titanic blasts called supernovae. Those explosions seed the nearby gas with heavy elements produced by the stars during their lifetimes. The very oldest stars consist almost entirely of the two lightest elements, hydrogen and helium, because they were born before ancient supernova explosions built up significant amounts of heavier elements. In most galaxies, the process is cyclical, with each generation of stars contributing more heavy elements to the raw material from which the next set of stars will be born. But not in Segue 1 -- in contrast to all other galaxies, the new analysis shows that Segue 1's star formation ended at what would ordinarily be an early stage of a galaxy's development. Segue 1 may have failed to progress further because of its unusually small size. Research suggests that Segue 1 is the least-chemically-evolved galaxy known. After the initial few supernova explosions, it appears that only a single generation of new stars formed, and then for the last 13 billion years the galaxy has not been creating stars. Because it has stayed in the same state for so long, Segue 1 offers unique information about the conditions in the Universe shortly after the Big Bang. Other galaxies have undergone multiple supernova explosions since their formation. The first supernovae to blow up, from the most massive stars, produce elements like magnesium, silicon, and calcium. Later explosions of smaller stars primarily make iron. Segue 1's uniquely low iron abundance relative to other elements shows that its star formation must have stopped before any of the iron-forming supernovae occurred. Its truncated evolution means that the products of the first explosions in Segue 1 have been preserved. Intriguingly, very heavy elements like barium and strontium are nearly absent from Segue 1's stars. The heaviest elements in that galaxy are at the lowest levels ever found, and that gives us clues about what those first supernovae looked like. Studying individual stars in dwarf galaxies can be difficult, and Segue 1, which orbits our own Milky Way, is particularly small, containing only about a thousand stars. Just seven stars in the entire galaxy are in the red-giant phase of their evolution, making them bright enough for modern telescopes to detect the features astronomers use to measure the abundance of each chemical element. Three of the seven red giants have heavy-element abundances more than 3,000 times lower than that of the Sun, highlighting the primitive nature of the galaxy. The team used one of the 6.5-m Magellan telescopes in Chile to observe five of the Segue 1 stars, while one was studied with the 10-m Keck I telescope in Hawaii. The final star was identified and measured by a competing team using ESO's 8.2-m VLT. NEW ELEMENT CONFIRMED Science Daily The periodic table has been extended, with the announcement of the confirmation of the yet-to-be-named element 117. In 2010 a US--Russian collaboration announced that it had produced atoms of an element with 117 protons, filling a gap that appeared when 118 was made four years earlier. However, the International Union of Pure and Applied Chemistry (IUPAC) insists on corroboration by two independent teams before it allows new elements to be added to the Periodic Table, although a temporary name of Ununseptium is in use until confirmation has been made. It has taken four years, but confirmation appears finally to have arrived. The discovery was made by a team at the GSI laboratory in Germany which fused calcium 48 and berkelium 249. That is not easy, because berkelium 249 is both hard to produce in substantial quantities and has a half life of only 320 days -- less than half of any amount produced will still exist a year after it was made. By watching the alpha particles emitted, the team concluded that they were the product of two decay chains, both originating with 294117, that is an atom with 117 protons and 177 neutrons. One of the chains included the isotopes 270Db and 266Lr, the latter adding four neutrons to the previous highest isotope of lawrencium. In general large atoms have shorter half lives (they decay more quickly through radiation) as their masses become greater. However, what are known as 'islands of stability' exist, and the authors believe that the one-hour half-life of 270Db marks an important step towards the identification of even-more-long-lived nuclei of superheavy elements. The manufacturing process was hardly efficient. More than 1000 atoms of 48Ca, not a common isotope in its own right, were fired at the berkelium to produce just four atoms of 117. Nevertheless it is likely that element 117 will be accepted. Element 117 is the most recent of six elements first announced by the Joint Institute for Nuclear Research in Russia. Of them, 113, 115 and 118 remain unconfirmed, although claims have been made for the first two. Such a small sample does not allow us to learn much about the chemistry of element 117. Ununseptium's position in the periodic table places it under the halogen elemnts such as fluorine and chlorine, but the strong capacity to capture electrons that makes those elements so reactive weakens as one goes down the table, and in fact it is thought if one could ever produce enough 117 to observe chemical interactions it would be more likely to lose electrons than gain them. The next question is, how can we create elements 119 and 120? To do that, however, a projectile heavier than 48Ca will need to be found; researchers are working on identifying the best candidate. SPA SOLAR SECTION 2014 March By Geoff Elston, SPA Solar Section Director We normally associated strong solar flares with large complex sunspot groups, but it seems that that is not always so. Two recent X-class flares, one in February (within AR 1990) the other in March (within AR 2017), appeared in sunspot groups that covered little more than an area similar to the total of the Earth's surface, which by solar standards is not large. It seems that part of the reason for some smaller groups creating such powerful flares is that the points of opposite magnetic polarity are much closer together in those sunspots, and that can lead to strong flaring activity. Rotation Nos. 2147 - 2148 There was a slight rise in sunspot activity in March. The Mean Daily Frequency climbed to 5.36 but there was a decrease in the Relative Sunspot Number to 74.98. WHITE-LIGHT ACTIVITY There was a scattering of sunspots on view as March began. The three highly active regions (AR 1981, 1982 and 1984), that had crossed the solar disc in the last week of February, were nearing the west (W) limb and were far less active. They were accompanied by bright faculae that showed up well against the slightly darker solar-limb region. Nearer the Central Meridian (CM) were AR 1987 and 1989 with AR 1992 and 1993 almost on the CM. Meanwhile, on the eastern half of the solar disc AR 1990 and 1991 had appeared. You *may* recall that AR 1990 was the large active sunspot group designated AR 1967 on a previous appearance, that was responsible for the auroral display seen over many parts of the UK and Europe at the end of February. AR 1991 had undergone a resurgence of activity by the 3rd: the leader and follower spots had grown in size and a small number of spots/pores had appeared between them. AR 1990 and 1991 were last seen nearing the W limb on the 7th (with AR 1993 further along the limb) surrounded by bright faculae. Further east were AR 1996, a cluster of numerous small spots, and towards the E limb some small spots (AR 1998 and 2000). AR 1996 had developed in size as it headed towards the W limb around the 9th and 10th. AR 1998 remained much the same but AR 2000 showed some development and was followed by some extensive bright faculae near the E limb. AR 2002 had appeared over the E limb around the 8th and within days had rapidly developed into a highly active region. There were some solar flares but none of the strength expected. Nevertheless, the group with its almost round leader spot was a fine sight as it crossed the CM around the 14th. Another round spot, AR 2005, had come over the E limb around the 12th. It was not that active but over the next few days it was the most prominent feature on the disc as it passed over the CM and went westwards. By the 23rd we had another spotted disc. AR 2005 was then close to the W limb followed by bright faculae, and the two most prominent groups were AR 2010 (at the CM) and following quite close behind AR 2014, which produced a minor but a long-duration flare that day. Both groups had highly complex magnetic structure according to the Spaceweather.com (www.spaceweather.com) website but as the days passes neither produced the strong flares expected. However, on the 29th AR 2017 produced a brief intense X-Class flare (mostly in the ultraviolet it seems) that caused great disturbance to the Earth's upper atmosphere and disrupted the normal propagation of terrestrial radio transmissions for a while. MDF: 5.36 R: 74.98 H-ALPHA ACTIVITY The first week of March showed a lot of activity. On the 1st the SE limb and particularly the SW limb showed some intricate prominences and a dark filament leading to a bright prominence on the NE limb. The following day both the E and W limbs had some attractive prominences. Plages and filaments were evident around AR 1987, 1990, 1991 and 1995. A long dusky filament was also clearly seen on the SW. The 3rd and 4th saw plenty of activity, with plages seen around all of the sunspot groups and some quite lengthy filaments; on the SW limb some extensive prominences were visible. A flare was seen within AR 1991 at 1024 UT on the 4th; elsewhere there were numerous long and elaborate filaments to be seen and some diverse and complex prominences along the SW and NE limbs. The 5th saw continued filament activity but not much in the way of prominences. This seemed to be the trend up until the 10th, when AR 1996, 1998 and 2002 all showed plages (particularly 2002 which had some very bright plages near to it) and conspicuous filament activity extending from the E limb where a group of prominences was located. The 11th was very active with plages around all the sunspot groups and numerous filaments, one of long and curved appearance on the SW and another reaching from AR 2002 towards the E limb. We saw some fairly long filaments on the 15th. On the 21st, when AR 2010 was nearing the CM, all sunspot groups showed plages around or near them, particularly AR 2010 which was extensive. The E limb showed a large complex prominence. When AR 2010 and 2014 crossed the disc in the last week of March they both had bright plages around them. There was also a long filament in the SW that persisted until it started to fade as it neared the SW limb. A bright eruptive prominence was seen on the NW limb on the 26th. The 29th saw another burst of plage and filament activity over many parts of the disc. The most noticeable prominences were on the W limb (near AR 2014) and the E limb. MDF (P): 8.69 Bulletin compiled by Clive Down (c) 2014 the Society for Popular Astronomy |
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Good Clear Skies
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Astrocomet
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Colin James Watling
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Astrocomet
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Colin James Watling
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Various Voluntary work-Litter Picking for Parish Council (Daytime) and also a friend of Kessingland Beach (Watchman)
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Profile: http://www.google.com/profiles/astrocomera
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Lyra Website: https://sites.google.com/site/lyrasociety/
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Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
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Information
Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork)
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Information
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