*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 291 2010 June 27 ==================================================== 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/ JUNE BOVTIDS - INITIAL IMPRESSIONS By Alastair McBeath, SPA Meteor Section Director As noted last time, the June Bovtids were predicted to produce some fresh activity on June 23-24, with Zenithal Hourly Rates (ZHRs) perhaps comparable to the ~20-50 level that happened at their previous significant return in 2004. Early indications are that some observers did detect visual activity from the shower over parts of Europe then, and several video meteor systems recorded a number of June Bovtids as well. Probable Bovtid rates were reported from around 20h UT on June 23 to 02:30 on June 24. Four potential peaks were predicted, centred at 22:40, 00:07, 01:22 and 03:53 UT that night. So far, there is no good indication that any of those specific timings produced unusual Bovtid numbers. Bovtid ZHRs have been difficult to compute so far, because observers seem to have struggled with conditions -- including problems due to the bright Moon, and sometimes clouds and haze. Intriguingly, not all the visual observers reported seeing some June Bovtids during the interval noted above either. My initial impression, based on details reported to the IMO-News and Meteorobs electronic mailing lists (archived via their respective home pages, http://www.imo.net , and http://www.meteorobs.org ), as well as more directly, could imply that even where Bovtid rates were claimed, ZHRs may not have been impressive, perhaps just 10 or so. Video Bovtid numbers also seem to have been quite low, somewhere between similar to, to well below, the sporadic numbers recorded during the same time. It is too soon to comment on how accurate or representative these very preliminary estimates may have been. However, if correct, the overall pattern could suggest that the dust trails may have been less concentrated than expected, and given a broader, but less active, maximum around and across the four timing predictions. No positive UK visual reports from June 23-24 have reached the Meteor Section as yet, with the usual weather problems at fault, according to the few people to get in touch soon after the expected event. Accordingly, all further June Bovtid data would be gratefully received! MAY 14-15 FIREBALL By Alastair McBeath, SPA Meteor Section Director More details have been established now for the 01:18 UT fireball on May 14-15, noted last time, seen from Warwickshire and imaged from the Netherlands by Klaas Jobse's all-sky fireball camera system. Although no very precise analysis was possible, it is likely the fireball flew on a roughly southeast to northwest trajectory above East Anglia, possibly starting from a point around 90-100 km altitude above central-northern Essex, somewhere between ~10 km south of Colchester to ~20 km west of that city. The last imaged point on the trail, which was almost certainly not the true end, could have been 10 km or so south of Peterborough in Cambridgeshire, at an altitude of ~50 km. Extrapolating from these rough estimates could imply the true end was maybe at 45 ± 5 km altitude above a point ~20 km northwest of Peterborough. Taking these values as approximately correct would lead to an atmospheric path length for the fireball of ~120-125 km, descending at an angle of 200-300 from the horizontal. The visual observer's estimate for the event's duration of three to four seconds would in turn infer an atmospheric velocity, not allowing for deceleration, of ~35 ± 7 km/s, thus about medium-speed on the 11 to 72 km/sec meteor atmospheric velocity scale. Although additional data would be needed to confirm all these points, they do fit plausibly within the expected ranges for fireball-class meteors. There is no evidence to suggest that a meteorite fall happened following this meteor, but continuing the estimated trajectory to the surface might have suggested a speculative arrival zone roughly on or east of a line from about Nottingham north-northwest to the Leeds area of central England. Fireball observations from the British Isles and nearby are always welcomed by the Meteor Section. (A fireball is any meteor that reaches at least magnitude -3 at its brightest.) Information on what to send and where to is available on the "Making and Reporting Fireball Observations" webpage, at:http://snipurl.com/u8aer , which includes a report form suitable for e-mailing. SOME COMETS MAY HAVE COME FROM OTHER STARS SwRI, Many comets may have been born in orbit around other stars, according to astronomers from the Southwest Research Institute (SwRI) in Boulder, Colorado. The team's computer simulations suggested that the Sun may have captured small icy bodies from other stars while it was in its birth star cluster. While the Sun currently has no companion stars, it is believed to have formed, with many other stars, from a dense cloud of interstellar gas. In the early stages, many of the stars may have formed lots of small icy bodies -- comets -- in discs from which planets may have formed. Most of the comets could have been ejected gravitationally from their original systems by newly forming giant planets, becoming free-floating members of the cluster. The Sun's cluster came to a violent end, however, when the hottest young stars blew away its remaining gas. The new models indicate that the Sun could have captured a large cloud of comets as the cluster dispersed. The process of capture is surprisingly efficient and leads to the possibility that the cloud consists of a potpourri of material from other stars that formed with the Sun. ANCIENT OCEAN MAY HAVE COVERED ONE-THIRD OF MARS University of Colorado, Boulder An ocean may have covered one-third of the surface of Mars some 3.5 billion years ago, according to a new study conducted by scientists at the University of Colorado in Boulder. The study is the first to combine the analysis of water-related features, including scores of delta deposits and thousands of river valleys, to test for the occurrence of an ocean sustained by a global hydrosphere on early Mars. While the notion of a large, ancient ocean on Mars has been repeatedly proposed and challenged, the new study provides support for the idea that a sustained sea existed on Mars more than 3 billion years ago. More than half of the 52 river delta deposits identified by the researchers in the new study -- each of which was fed by numerous river valleys -- probably marked the boundaries of the proposed ocean, since all were at about the same elevation. Twenty-nine of the 52 deltas were connected either to the ancient Mars ocean or to the ground-water table of the ocean and to several large adjacent lakes. The study implies that ancient Mars probably had an Earth-like hydrological cycle, including precipitation, runoff, cloud formation, and ice and ground-water accumulation. Researchers concluded that the ocean might have covered about 36% of the planet and contained about 124 million cubic kilometres of water, about a tenth of the total in the Earth's oceans. METEOR PROBABLY CAUSED FLASH ON JUPITER STScI Observations made by the Hubble telescope have failed to find an origin for the flash of light seen on Jupiter on June 3. The only plausible explanation seems to be that it came from a meteor that burnt up above Jupiter's cloud tops and did not plunge deep enough into the atmosphere to explode and leave behind any telltale clouds of debris such as have been seen after previous Jupiter collisions. Australian amateur astronomer Anthony Wesley saw the flash when he was watching a live video feed of Jupiter from his telescope. In the Philippines, amateur astronomer Christopher Go confirmed that he had simultaneously recorded the transitory event on video. The two-second flash of light in the videos of Jupiter was presumably created in the same way as a meteor trail on Earth. A shock wave generated by ram pressure as the meteor speeds into the planet's atmosphere heats the impacting body to a high temperature, and as the hot object streaks through the atmosphere, it leaves behind a glowing trail of superheated atmospheric gases and vaporized meteor material that rapidly cools and fades in just a few seconds. Though astronomers are very uncertain about the rate of large meteoroid impacts on the planets, the best guess for Jupiter is that the smallest detectable events may happen as frequently as every few weeks. The meteor flashes are so brief that they are easily missed, even in video recordings, or perhaps misidentified as detector noise or cosmic-ray hits on imaging devices. Obviously something must have hit the planet to produce a flash bright enough to be seen from here. Images taken by Hubble 3 days after the flash was sighted showed no sign of debris above Jupiter's cloud tops. That has been interpreted to mean that the object did not penetrate beneath the clouds and explode as a fireball. If it did, previous events would lead to an expectation that dark blast debris would have been ejected and would have rained down onto the cloud tops, and the impact site would have appeared dark. Dark smudges marred Jupiter's atmosphere when a series of comet fragments hit the planet in 1994. A similar phenomenon occurred last July when a suspected asteroid collided with Jupiter. The latest impactor is thought to have been smaller than those earlier ones. EXO-PLANET SEEN TO HAVE MOVED ESO For the first time, astronomers have been able to follow the motion of an exo-planet (that of Beta Pictoris) as it moves from one side of its host star to the other. Images are available for approximately 10 exo-planets, and the planet around Beta Pictoris has the smallest orbit known so far. It is at a distance between 8 to 15 astronomical units -- about the distance of Saturn from the Sun. Only 12 million years old, Beta Pictoris is 75% more massive than the Sun. It is about 20 parsecs away (1 parsed is about 3.26 light-years) and is one of the best-known examples of a star surrounded by a dusty debris disc. Earlier observations showed a warp of the disc, a secondary inclined disc, and some evidence of comets falling onto the star. Those were indirect but telltale signs that suggested the presence of a massive planet, whose existence is now supported by new observations. Because the star is young, the discovery shows that gas-giant planets can form in only a few million years, a short time in cosmic terms. The team used one of the 8.2-metre VLT telescopes to study the immediate surroundings of Beta Pictoris in 2003, 2008 and 2009. In 2003, a faint source was seen inside the disc, but it was not possible to exclude the remote possibility that it was a background star. In images taken in 2008 and spring 2009 the source had disappeared. The most recent observations, taken in late 2009, showed an object (presumed to be the same one as in 2003) on the other side of the disc, so it seems certain that the source is a planet and that it is orbiting the star. The short period will allow astronomers to record the full orbit within 15 to 20 years. The planet has a mass of about 9 Jupiter masses and the right mass and location to explain the observed warp in the inner parts of the disc. ANTHRACENE FOUND IN INTERSTELLAR SPACE RAS Anthracene molecules have been identified in an interstellar cloud in the direction of the star BD +31 540 in Perseus, about 200 parsecs away. Anthracene is one of the most complex carbon-containing molecules yet found in the interstellar medium. It consists of three fused benzene rings, containing a total of 14 carbon atoms, with a hydrogen atom at each of the ten 'free' corners. Until now, anthracene had been detected only in meteorites and never in the interstellar medium. DOUBTS ABOUT THE DARK SIDE RAS Research by astronomers using observations from the Wilkinson Microwave Anisotropy Probe (WMAP) suggests that the recent allegations about the content of the Universe may be wrong. The scientists found evidence that the errors in the data may be much larger than previously thought, which in turn makes the conclusions drawn from them open to question. Launched in 2001, WMAP measures the small differences in intensity between different directions in the Cosmic Microwave Background (CMB) radiation, the residual heat of the Big Bang that fills the Universe and appears over the whole of the sky. The angular size of the ripples in the CMB is thought to be connected with the composition of the Universe. The observations of WMAP showed that the ripples were about twice the size of the full Moon, or around a degree across. Just from those results, some scientists concluded that the cosmos is made up of 4% normal matter, 22% 'dark' or invisible matter and 74% "dark energy" -- simply a name for what was otherwise unaccounted for. The team used astronomical objects that appear as unresolved points in radio telescopes to test the way the WMAP telescope smoothes its maps. They find that the smoothing is much larger than previously believed, suggesting that its measurement of the size of the CMB ripples is not as accurate as was thought. If true, that could mean that the ripples are significantly smaller, which could imply that dark matter and "dark energy" are not present after all. In addition, the astronomers recently collaborated in an international team whose research suggested that the structure of the CMB may not provide the independent check on the presence of "dark energy" that it was thought to do. If "dark energy" were to exist, then it has been thought to cause the expansion of the Universe to accelerate. On their journey from the CMB to WMAP, photons travel through superclusters of galaxies. The photon is first blueshifted when it enters the supercluster and then redshifted as it leaves, so the two effects cancel. However, if the supercluster galaxies are accelerating away from each other because of dark energy, the cancellation is not exact, so photons stay slightly blueshifted after their passage. Slightly higher temperatures should appear in the CMB where the photons have passed through superclusters. However, the new results, based on the Sloan Digital Sky Survey which surveyed 1 million luminous red galaxies, suggest that no such effect is seen, again threatening the recent models of the Universe. If the result is repeated in new surveys of galaxies in the southern hemisphere then it will pull the rug out from under dark energy. If the Universe really has no 'dark side', it will come as a relief to some theoretical physicists. Having a model that depends on as-yet- undetected exotic particles that might make up dark matter and the completely unexplained dark energy has left real scientists feeling uncomfortable. It also throws up problems for the birth of stars in galaxies, with as much 'feedback' energy needed to prevent their creation as gravity provides to help them form. The European PLANCK satellite, currently collecting more CMB data, is expected to provide new information and help to answer fundamental questions about the nature of the Universe we live in. HAYABUSA RETURNS TO EARTH NASA The sample capsule from the asteroid explorer Hayabusa, launched in 2003 by the Japan Aerospace Exploration Agency (JAXA) has returned to Earth. With Hayabusa, JAXA scientists and engineers hoped to obtain detailed information on electrical propulsion and autonomous navigation, as well as an asteroid sampler and sample re-entry capsule. The 510-kg Hayabusa spacecraft reached the asteroid Itokawa in 2005 September. Over the next 2.5 months, it made scientific observations of the asteroid's shape, surface, surface altitude distribution, mineral composition, gravity, and the way it reflected the Sun's radiation. On November 25 of that year, the craft briefly touched down on the surface of Itokawa and attempted to sample asteroid surface material, but there seemed to be a malfunction in the sample-collection process. Nevertheless, scientists hope to find some of the asteroid's surface material in the capsule. ROSETTA SET TO ENCOUNTER ASTEROID LUTETIA Science Daily The European Space Agency's comet-chaser Rosetta is expected to pass to within 3300 km of asteroid Lutetia on July 10. Rosetta started taking navigational sightings of Lutetia at the end of May so that ground controllers could determine any course corrections required to achieve their intended fly-by distance. The close pass will allow around 2 hours of good imaging. The spacecraft will instantly begin beaming the data back to Earth and the first pictures will be released later that evening. Rosetta flew by asteroid Steins in 2008 and other space missions have encountered a number of asteroids, each of which has proven to have its individual character. At present, no one knows what Lutetia looks like. Orbiting in the main belt of asteroids between Mars and Jupiter, it appears just as a point of light to ground telescopes, although its magnitude suggests that it has dimensions of the order of 100 km. A continuous variation in its brightness makes it clear that Lutetia is rotating and has an uneven surface. Owing to holidays, the next scheduled bulletin will be issued on July 18. Bulletin compiled by Clive Down (c) 2010 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/