*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 261 2009 February 15 ==================================================== 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/ QUADRANTIDS UPDATE By Alastair McBeath, SPA Meteor Section Director Additional data on IYA2009's first major shower has continued to come through since the preliminary round-up in ENB 259 (at http://snipurl.com/bvmg2 ), including fresh visual data from George Gliba (West Virginia, USA), who caught a magnitude -3 Quadrantid at 09:50 UT which was also seen by Rich Taibi in Maryland, plus automated video results from Enrico Stomeo (Scorze, Italy) for January 3-4, and Ferruccio Zanotti (Ferrara, Italy) for January 2-3. Ferruccio's results were limited by poor weather early in the night, but he caught the strongly-rising activity towards dawn very nicely, with up to two or three Quadrantids per minute at times between 04:50-06:00 UT. Enrico's data showed a most intriguingly strong Quadrantid video rate right at the start of the night on January 3-4. Between 16:43-17:44 UT he caught 5 Quadrantids, which allowing for the low radiant elevation then was possibly a similar level of real activity to what he caught right at the end of the previous night! He recorded lower Quadrantid video numbers through till the hour ending at 19:46 UT, but then nothing more from the shower till about 22h UT, by when the radiant was reaching a useful elevation from his location once more. The radio results have been added to too since ENB 259 thanks to the arrival of Radio Meteor Observation Bulletin 186 (January 2009; see http://www.rmob.org ), courtesy of Editor and observer Chris Steyaert in Belgium. The other Quadrantid RMOB radio observers included: Enric Algeciras (Spain), Orlando Benitez (Canary Islands), Mike Boschat (Nova Scotia, Canada), Jeff Brower (British Columbia, Canada, who helpfully provided separately more detailed information from his January radio data than was featured in the RMOB), Willy Camps (Belgium), Gaspard De Wilde (Belgium), SPA Assistant Meteor Director David Entwistle (England), Alex Guzanoff (Oktyabrsky, Russian Federation), Alfred Krohmal (Syzran, Russian Federation), Ed Majden (British Columbia, Canada), Mike Otte (Illinois, USA), Ivan Sergey (Belarus), Andy Smith (England), Dave Swan (England), Maarten Vanleenhove (Belgium), Felix Verbelen (Belgium) and John Wardle (England). Discussion of these has continued with Jeff and David in recent weeks as well, and the following notes reflect this, as well as my own detailed analysis of all the available radio data (including the Japanese summary mentioned previously) in the last few days. Substantial activity due to the Quadrantids was found in all the viable datasets on January 3, significantly more obviously than is sometimes the case, which would fit with the initial International Meteor Organization's (IMO's) findings of unusually protracted, strong Quadrantid rates overall. A significant number of radio observers detected well-above-normal meteor echo counts from 23h UT on January 2 to 20h UT on January 3, with an especial core period lasting from roughly 03h to 17h UT on the 3rd. Within that core, there were two distinct main peak phases, one from roughly 04h to 08h (especially during the one-hour data collection bin from 06h-07h), the other fairly consistently from 13h to 15h UT. As far as the results allowed, both these peak episodes seemed equally strong at their best. The relatively lowest activity between them was from roughly 08h to 10h UT, but even that was well above the usual background. There was though no distinct peak around 18h UT, as was suspected from some of the early radio results. Although Enrico's video data did suggest some possible support for this initially, it now seems he was lucky in catching the very tail-end of the UT afternoon Quadrantid peak, part of the falling activity seen in the radio analysis till about 20h UT. The preliminary IMO short-interval visual analysis (off the http://www.imo.net homepage) has continued to be updated since ENB 259 as well, suggesting that Zenithal Hourly Rates (ZHRs) of 100+ were present from roughly 04:30 to 18h UT on January 3, possibly with ZHR peaks of ~115 around 05h-06h, ~130-150 from 09h-12h, and ~160 in the hour centred on 13:00 UT. There remain some quite substantial gaps in its coverage however, especially between 06h-09h and 14h-17:30 UT, which the radio analysis has now indicated may be important for determining how the shower performed this year. As always, many thanks and congratulations are due to all the named observers here and in ENB 259 for their splendid observing efforts, as well as for their comments, and in some cases detailed discussions. In particular, the radio analysis this time, so often a difficult and inconclusive task, has produced an unusually clear pattern, one which perhaps in time enough visual and other video observations may be able to confirm (or not!). URSIDS UPDATE By Alastair McBeath, SPA Meteor Section Director A little more information on last December's Ursids has become available since the previous notes on the shower in ENB 259. Some visual data from Robin Gray in Nevada, USA for December 22-23 was kindly forwarded to us by Rich Taibi, Robin spotting no Ursids the night after the maximum, helping confirm the previously-established brevity of the source at an easily-detectable level. Jeff Brower also provided some additional details from his radio reports made across the shower, which largely confirmed his earlier findings reported previously. Sirko Molau's summary of the IMO video reports, chiefly made from Europe, circulated on the IMO-News e-mail group on January 22, mentioned locating an Ursid peak probably less active than in either 2006 or 2007 around 02h-03h UT on December 22, but he made no comment about the peak seen later that UT morning over North America. The IMO's visual data estimates (see http://www.imo.net/live/ursids2008/ ) suggested ZHRs were no higher than 10 on December 22, although there were only two adjacent datapoints showing this, at 00:01 and 10:17 UT, which could suggest at least an unusually protracted period of better Ursid rates. It is unclear why the ZHRs were so far below some of the earlier estimates. For example, variable ZHRs of 15-30 were found from December 22 results submitted to the SPA during the 00h-03h UT interval, perhaps rising again to levels of 15-35 around 06h-09h UT over North America, as noted in ENB 258 at http://snipurl.com/bwzgd , while the radio results suggested peaks around 01h-03h, 07h-08h and 09h-10h UT in ENB 259. The IMO results may have been derived by combining data from too large a time-span perhaps, thus losing the significance of some of the detected higher activity in between the two combined datapoints. My grateful thanks go again to everyone who has contributed observations and comments from the shower to the Section. METEOR SECTION WEBPAGES UPGRADE By Alastair McBeath, SPA Meteor Section Director As part of the SPA's activities during IYA2009, the Meteor Section's webpages are undergoing a thorough overhaul at present. The first of the upgraded webpages have just gone "live" online, with other changes and improvements to follow during the rest of this year. The new-look homepage remains where it always has been, at http://www.popastro.com/sections/meteor.htm , which allows access to all the other Meteor Section pages. Probably the single biggest change is that for the very first time, the Section's instruction booklet "Observing Meteors" which only SPA members who joined the Section used to receive, is now freely available complete online. To accompany this, another new page has been prepared with additional advice for those wishing to try out meteor imaging, while a further page on radio meteor observing will be provided soon. Not everything has or will be changed, of course. The monthly meteor activity pages will continue to appear regularly, and the Recent Fireball Sightings page will be updated as fresh information becomes available, as normal. The annually-updated Meteor Showers List will continue, and the 2009 to January 2010 version will be online shortly. The archived reports from previous years will stay as well, but have moved to a new entry-page. Additions will be made to these with links to Forum and ENB reports later on. Links to such reports from the current year are also available via their own separate gateway page. The Fireball Observing page has been rewritten, and includes a new report form, available from its usual address, http://www.popastro.com/sections/meteor/fireball_sightings.htm . GREEN COMET APPROACHES EARTH NASA The greenish-looking Comet Lulin, named after the observatory in Taiwan where the discovery photo was taken, will make its closest approach to the Earth (0.41 AU) on Feb. 24. Current estimates give the maximum brightness as 4th or 5th magnitude, which means that dark skies would be required to see it. No one can say for sure, however, because this appears to be Lulin's first visit to the inner Solar System and its first exposure to intense sunlight. Lulin's green colour comes from the gases that make up its Jupiter-sized atmosphere. Jets from the comet's nucleus contain cyanogen (CN -- observed in many comets) and diatomic carbon (C2); both substances glow green when illuminated by sunlight in the near-vacuum of space. The comet rises a few hours before the Sun and will be at about 30 degrees altitude in the southern sky before dawn. It may be easiest to find on Feb. 16, when it passes near Spica, and on Feb. 24, when it will be just a few degrees from Saturn in the constellation Leo. NEW TECHNIQUE TO MEASURE ASTEROIDS ESO Interferometry employing multiple telescopes can determine the sizes and shapes of asteroids that are too small or too far away to be resolved by other techniques, and may increase by a large factor the number of asteroids that can be measured. Direct imaging with adaptive optics on the largest ground-based telescopes such as the Very Large Telescope (VLT) in Chile, space telescopes, or radar measurements are the currently used methods of asteroid measurement. However, direct imaging, even with adaptive optics, is generally limited to the largest asteroids of the main belt, while radar measurements are mostly limited to observations of near-Earth asteroids that have close encounters with our planet. In recent experiments with the VLT interferometer, the light from two of the 8.2-metre 'unit telescopes' was combined, affording a resolving power equivalent to that of a telescope having an aperture equal to the separation between the two telescopes used, in this case 47 metres. In principle the interferometer ought to be able to resolve asteroids as small as about 15 km in diameter in the main asteroid belt, 200 million kilometres away. In the only actual result so far reported, the researchers observed the main-belt asteroid (234) Barbara, which was earlier found to have rather unusual properties. The observations indicated that that object has indeed a peculiar shape. The best model (still only tentative) suggests that the asteroid consists of two bodies with diameters of 37 and 21 km, separated by at least 24 km. HYDROCARBON RAINS MAY FILL TITAN LAKES Cassini Imaging Laboratory Saturn's largest satellite, Titan, is the only satellite in the Solar System with a thick atmosphere in which complex chemistry occurs. For several years, Cassini scientists have suspected that dark areas near Titan's poles might be liquid-filled lakes. Recent pictures of the south-polar region show new lake features that were not seen in images taken a year ago of the same area. The fact that extensive cloud systems covered the area in the intervening year suggests that the new lakes could be the result of a heavy rain of hydrocarbons, and that lakes may owe their presence, size and distribution across Titan's surface to the moon's weather and changing seasons. Cassini has now surveyed nearly all of Titan's surface at high resolution. The observations suggest that there is more liquid methane in the northern hemisphere than in the southern. Cassini scientists think that, as the northern hemisphere moves toward summer, large convective cloud systems will form there, and precipitation greater than that inferred in the south could extend the northern lakes. Some of the north-polar lakes are large. If full, Kraken Mare, at 400,000 square kilometres, would be almost five times the size of North America's Lake Superior. The north-polar dark 'lake' areas observed by Cassini total more than 510,000 square kilometres -- almost 40% larger than the Earth's largest lake, the Caspian Sea. However, it does not seem likely that evaporation from the lakes could be enough to replenish the methane lost from the atmosphere by rainfall and by the formation and eventual deposition on the surface of methane-derived haze particles. Combined with previous analyses, the observations suggest that underground methane reservoirs must exist. MANY BROWN DWARFS IN STAR-FORMING REGION Subaru Telescope facility Approximately 6,000 light-years away in the constellation Cassiopeia, there is a very active and massive star-forming region called W3 Main. Recently a team of Japanese and Indian astronomers has been using the Subaru telescope in Hawaii to look for dim low-mass stars, and has found a considerable number of brown dwarfs in the W3 Main region. That result is significantly different from the one obtained in the cases of the Trapezium and IC 348, where the relative number of brown dwarfs is fewer. TELESCOPE SEES SMALLEST EXOPLANET BBC News The smallest exo-planet yet found has been detected by the French space telescope Corot. The object is less than twice the size of the Earth and is one of only a few planets so far found with masses comparable with that of the Earth. About 330 exo-planets have been discovered so far, but most of them are gas giants similar to Jupiter or Neptune. The new find, Corot-Exo-7b, orbits a Sun-like star once every 20 hours and has a temperature between 1,000 and 1,500C. The vast majority of exo-planets has been discovered by the radial- velocity method, which was initially developed by the person who edits these Bulletins. That method favours the detection of large planets orbiting close to their parent stars. The new planet was detected photometrically by the transit method, as it crossed the face of the star, blocking a small fraction of the star's light as it passed in front. The transit method, too, favours the detection of big planets, because they block out more light from the parent star, but in a case -- such as this one -- of a small star then a moderate-sized planet can be enough to block out enough light for the dimming to be detected. GAMMA-RAY FLARE STAR NASA The Swift and Fermi spacecraft are monitoring a neutron star, 30,000 light-years from the Earth, that is drawing attention to itself with a series of powerful gamma-ray flares. At times, that remarkable object has erupted with more than a hundred flares in as little as 20 minutes; the most intense flares emitted more total energy than the Sun does in 20 years. The star, known as SGR J1550-5418, lies in the southern constellation Norma. It began a series of modest eruptions on 2008 Oct. 3, settled down for a while, then had an intense episode on 2009 Jan 29. Because of its rapid outbursts and gamma-ray spectrum, astronomers classify the object as a 'soft-gamma-ray repeater' -- only the sixth known. In 2004, a giant flare from another soft-gamma-ray repeater was so intense that it ionized the Earth's upper atmosphere from 50,000 light-years away! Using data from an X-ray telescope on Swift, astronomers saw the first 'light echoes' to have been observed from a soft-gamma-ray repeater. Images acquired when the latest flaring episode began show what appear to be expanding haloes around the source. Multiple rings form as X-rays interact with dust clouds at different distances. Scientists think the source of the flares is a spinning 'magnetar', a neutron star with an incredibly intense magnetic field. One theory of soft- gamma-ray repeaters holds that the flares are caused by 'starquakes' in the outer rigid crust of the magnetar. As a magnetar's colossal magnetic field shifts, it strains the crust with enormous magnetic forces, often breaking it. When the crust snaps, it vibrates with seismic waves as in an earthquake and emits a flash of gamma-rays. STARS FORMING AT MAXIMUM SPEED Science Daily Galaxies, such as our own Milky Way, contain billions of stars. Theoreticians would like to know how such gigantic systems came into being -- did the central region form first and then grow, or did the stars form at the same time throughout the entire galaxy? An international team led by the Max Planck Institute for Astronomy is now a bit closer to the answer to those questions. The researchers studied one of the most distant known galaxies, a quasar with the designation J1148+5251. Light from it has taken 12.8 billion years to reach the Earth, so the observations show the galaxy as it was all that time ago, providing a glimpse of the very early stages of galactic evolution, less than a billion years after the Big Bang. With the IRAM interferometer, a German/French/Spanish radio telescope, the observers recorded the infrared radiation emitted by J1148+5251 at a specific frequency associated with ionized carbon atoms, which is a reliable indicator of ongoing star formation. The resulting images show sufficient detail to allow, for the first time, the measurement of the size of a very early star-forming region. The researchers concluded that, at that time, stars were forming in the core region of J1148+5251 at record rates. Every year, that galaxy's central region produced new stars with a combined mass of more than a thousand Suns. By contrast, the rate of star formation within our own galaxy, the Milky Way, is roughly one solar mass per year. It has been known for some time that young galaxies can produce impressive amounts of new stars, but overall activity is only part of the picture. Without knowing the star-forming region's size, it is impossible to compare star formation in early galaxies with theoretical models, or with star-forming regions in our own galaxy. With a diameter of only 4000 light-years (for comparison, the Milky Way galaxy's overall diameter is something like 100,000 light-years), the star-forming core of J1148+5251 is extremely productive. In fact, it is close to the limit imposed by physical laws. Stars are formed when cosmic clouds of gas and dust collapse under their own gravity. As they collapse, temperatures rise, and internal pressure starts to build up. Once that pressure has reached certain levels, all further collapse is brought to a halt, and no additional stars can form. The result is an upper limit on how many stars can form in a given volume of space in a given period of time. Remarkably, the star-forming core of J1148+5251 appears to be operating at that absolute limit. Bulletin compiled by Clive Down (c) 2009 the Society for Popular Astronomy The Society for Popular Astronomy has been helping beginners to amateur astronomy -- and more experienced observers -- for more than 50 years. If you are not a member then you may be missing something. Membership rates are extremely reasonable, starting at just £16 a year in the UK. You will receive our bright quarterly magazine Popular Astronomy, regular printed News Circulars, help and advice in pursuing your hobby, the chance to hear top astronomers at our regular meetings, and other benefits. The best news is that you can join online right now with a credit card or debit card at our lively website: http://www.popastro.com/