*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 270 2009 July 12 ==================================================== 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/ IMAGED FIREBALLS IN JUNE-JULY By Alastair McBeath, SPA Meteor Section Director No fresh information has come in regarding the ~20:30 UT fireball on June 15-16 since the previous ENB, but details on three fireballs imaged from Europe since then have. The first was actually on June 15-16, a magnitude -6 event imaged from western France at 23:57 UT, which at least suggests more than one fireball passed not far from the British Isles that night, though this one was not reported from the UK. Karl Antier forwarded details about it, and the image can seen at http://snipurl.com/n2uit . The second event was still more spectacularly brilliant, and was imaged from Italy on June 20-21, at 21:10 UT. The lucky imager commented it was a little like a scene from the movie "Independence Day"! Ferruccio Zanotti sent in notes about it, and you can find more comments, some in English, some Italian, at: http://snipurl.com/n2uls while the images are available here: http://snipurl.com/n2unf . July 3-4 brought the third event, of about magnitude -6/-7 or more, whose image was secured by Klaas Jobse's all-sky camera system at Oostkapelle in the Netherlands, at 22:55 UT. It can be seen here: http://snipurl.com/n2uow , including a close-up of the fireball's trail. This event was also observed visually from England. Two observers, one in Kent, the other the West Midlands, have reported seeing it so far - see http://snipurl.com/n2vnc on the SPA's Observing Forum for some preliminary comments, including from one of the lucky British witnesses. Unfortunately, it has not been possible to determine a clear trajectory for the object from these observations, but the meteor was likely out high over the southern North Sea between southeast England and western Holland, probably heading in a direction between roughly southwest-northeast to south-north. It seems to have been slow-moving, as one visual witness and Klaas' image, suggested it was visible for around 5 to 6 seconds. Many thanks go to all who provided details on these impressive events. Sightings of fireballs (meteors of at least magnitude -3) made from the British Isles and places nearby are always welcomed by the Meteor Section. The details to report, including an e-mail report form, are described on the "Making and Reporting Fireball Observations" page of the SPA website, at: http://snipurl.com/kzlh7 . "SKY LANTERNS" ARE STILL NOT FIREBALLS! By Alastair McBeath, SPA Meteor Section Director Back in ENB 228 (see http://snipurl.com/n2tp6 ), I gave some notes on the increasing problems created by "sky lanterns" being misidentified as meteoric fireballs. Since that notice appeared in late 2007, the problems have grown significantly worse. Between January 1 and July 4 this year, 43 genuine fireball-class meteors had been reported to us from Britain and nearby, away from the main shower maxima, plus 23 "lantern" sightings. In the whole of 2008, 72 fireballs were similarly reported, plus just 7 "lanterns"! A recent discussion on the SPA's Observing Forum (at: http://snipurl.com/n2xmq ) has helped highlight what the things are and the difficulties they're now creating for observers, plus the hazards they pose for aviation, their obvious fire risk, and the false alarms they have caused for coastguards, when mistaken for red distress flares over the sea. "Sky lanterns" are roughly metre-high, paper hot air balloons, powered by a burning wick suspended below them. Recent reports have suggested some may be larger than this, however. Released singly or sometimes in groups to go wherever the wind takes them, they first started to appear as objects mistaken for meteoric fireballs in the summer of 2007 over Britain. They can look like literal "balls of fire", frequently yellow, orange or red in colour, sometimes showing a flickering appearance, or even with clear flames seen, and a few have apparently dropped burning material vertically below them. They drift with the wind (remembering the surface wind is not always a guide to how the wind may be behaving some tens to hundreds of metres above ground-level), and remain visible for between tens of seconds up to several minutes. Occasionally, they have been observed to disappear into low cloud, and some have left a dark, smoky trail in the sky for a short time. They can be very bright. Much of this behaviour is quite unlike that of genuine meteors, which follow straight-line paths, are always above even the very highest tropospheric clouds, and rarely remain visible for more than a few seconds as they streak across part of the sky. Man-made re-entry fireballs, which are much slower than natural meteors, can occasionally last up to a minute or two, but again they usually show a glowing streak across the sky. Any train left after a meteoric object has disappeared, a column of ionized gas, will glow rather than be dark. A very large meteoroid can leave a dark smoke trail which is not self-luminous, but this is opaque, and has the appearance of roiling clouds, something like the effect seen in volcanic dust clouds, or more commonly the "cauliflower" appearance of "fluffy" cumulus clouds, and it always lies along the original straight-line path only at first (though it may drift away from that area, and spread, with time). The smoky trails left by "sky lanterns" seem to be quite thin to transparent in parts, by contrast. In theory, mass-releases of "sky lanterns" are supposed to be notified to the aviation authorities in advance, and coastguards have begun asking for similar information on ANY such near-coastal releases (not just for groups of "lanterns"). It is though already clear this notification to the aviation authorities does not always happen - indeed such advance warnings seem rather the exception, judging by the numerous "UFO" reports in the media recently, almost all of which seem to have been due to these "sky lanterns". The best way to tell "sky lanterns" apart from genuine fireballs or other astronomical targets like artificial satellites, is to examine them with good, firmly-held, properly-focused, binoculars. This should enable an easy confirmation of what they were. If the object vanished before you could swing your binoculars into action, even when they were slung ready around your neck, chances-are that object was meteoric, though it may also have been a brief satellite flare, or aircraft lights. To check for those, keep watching the same area of sky for any repeat flashes of light over the next half minute or so. If, even after careful checking, you couldn't be sure whether what you saw was a meteor or something else, please send a fully-detailed sighting to the Meteor Section. Of course, if your object was a genuine fireball-class meteor, I would be delighted to have a similarly-detailed observation of that from you too! LATE JULY'S METEOR ACTIVITY By Alastair McBeath, SPA Meteor Section Director As the Perseid maximum in mid-August will have a bright waning Moon to contend with this summer, the lower-activity southern-sky showers that peak with fewer moonlight problems near the end of July become a more appetizing prospect than normal. The stronger source is the Delta Aquarids, whose maximum Zenithal Hourly Rates (ZHRs) should be about 15-20, usually achieved for a day or two around July 28-30. However, their radiant lies sixteen degrees below the equator then, so the shower is never seen at its best from Britain, and observed rates will be well below the ZHR as a result. The radiant though is above the horizon all night, while the Moon, at first quarter on July 28, will set during the late evening hours UT for the peak, and by midnight even as late as August 1. This early-setting Moon favours the other leading, if much less active, late July shower peak, that of the Alpha Capricornids, around July 30-31. Highest ZHRs are usually only ~5, though a minor enhancement to ~10, with several fireballs, was observed from Europe - including Britain - in 1995, and the shower is noted for occasionally producing wonderfully bright, slow meteors. Be aware during your observations that the Antihelion Source is active simultaneously, near both these radiants (indeed it partly overlaps that of the Alpha Capricornids), centred on the ecliptic about 12° east of the point opposite the Sun in the sky, but extending in a roughly oval region away from that centre-point for about 30° in RA (two hours) and 15° in Dec. The centre culminates around 01h UT. Antihelion ZHRs are liable to be about one or two for most of the month, rising to perhaps 2-3 by late July. As with the Delta Aquarids, their deep southerly radiant will likely reduce observed numbers from the UK to negligible proportions other than in late July. Don't forget too that some early Perseids should be present from July 17 onwards, radiating from "below" the "W" of Cassiopeia. Activity will not be plentiful from them either - their ZHRs usually do not rise above ~10 until the first week of August - though the combined effect of all these sources, plus the omnipresent sporadic meteors, can produce quite healthy observed hourly meteor counts, under clear, dark skies. More details, including radiant charts for all these sources, are available on the monthly meteor webpage of the SPA site, off the homepage at: http://snipurl.com/n2url . Good luck! TUNGUSKA EVENT CAUSED BY COMET Geophysical Research Letters In recent years there has increasingly been a consensus that the object that caused the 1908 Tunguska explosion that levelled a large area of Siberian forest was of the nature of a comet. That conclusion is supported by Cornell University research from an unlikely direction --- the exhaust plume from the space shuttle launched a century later. The research connects the two events by what followed each about a day later: bright night-visible clouds, or noctilucent clouds, that are made up of ice particles and form only at very high altitudes and in extremely cold temperatures. The researchers contend that the massive amount of water vapour thrown into the atmosphere by the comet's icy nucleus was caught up in eddies by a process called two-dimensional turbulence, which explains why the noctilucent clouds formed a day later many thousands of miles away. Noctilucent clouds are the highest type of clouds, forming naturally in the mesosphere at about 55 miles over the polar regions during the summer months when the mesosphere is around -117 C. A single space-shuttle flight injects 300 tons of water vapour into the Earth's thermosphere, and the water particles have been found to travel to the Arctic and Antarctic regions, where they form the clouds after settling into the mesosphere. Researchers saw the noctilucent- cloud phenomenon days after the space shuttle Endeavour was launched on 2007 August 8. Similar cloud formations had been observed after launches in 1997 and 2003. Following the 1908 explosion, known as the Tunguska Event, the night skies shone brightly in the north for several days across Europe, particularly Great Britain. LANDFORMS INDICATE 'RECENT' WARM CLIMATE ON MARS Science and Technology Facilities Council New research indicates that Mars had a significantly warmer climate in its recent past than previously thought. Scientists came to that conclusion by studying high-resolution images, obtained by the Mars Reconnaissance Orbiter, of equatorial landforms that formed by melting of ice-rich soils. The work indicates that the Martian surface experienced freeze-thaw cycles as recently as 2 million years ago, and that Mars has not been locked in permafrost conditions for billions of years as had been previously thought. The features were previously interpreted to be the result of volcanic processes but are now attributed to the expansion and contraction of ice, and by thawing of ice-rich ground, and suggest a climate very different from what we find today. All of the landforms observed are in an outflow channel, thought to have been active as recently as 2 to 8 million years ago. Since the landforms exist within, and cut across, the pre-existing features of the channel, they too must be supposed to have been created within that time. The pictures show polygonally patterned surfaces, branched channels, blocky debris and mound/cone structures, all of which are similar to landforms on Earth typical of areas where permafrost terrain is melting. The observations demonstrate not only that there was ice near the Martian equator in the last few million years, but also that the ice melted to form liquid water and then re-froze, probably for many cycles. LARGEST MAP OF COLD DUST REVEALED ESO A new atlas has been produced, showing the inner regions of the Milky Way at sub-millimetre wavelengths. It covers a strip about two degrees wide and over 40 degrees long along the galactic plane, and was created from observations made with the APEX telescope in Chile. APEX is located at an altitude of 5100 m on the arid plateau of Chajnantor in the Chilean Andes -- a site that permits observations in the sub-millimetre wavelength range. The Universe is relatively unexplored at sub-millimetre wavelengths, as extremely dry atmospheric conditions and advanced detectors are required for such observations. Images at those wavelengths are useful for studies of the birthplaces of stars and the structure of the crowded Galactic core. The new atlas, known as the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL), offers a fresh view of the Milky Way. It should give us an overview of the large-scale structure of our Galaxy, and provide a guide for observations to be made with the forthcoming ALMA telescope and with the recently launched Herschel space telescope. The interstellar medium is composed of gas and grains of cosmic dust, rather like fine sand or soot. The gas is mostly hydrogen, which is difficult to detect, so the dense regions are often identified instead from the faint heat glow of the cosmic dust grains. Sub-millimetre radiation shows the dust clouds as shining, even though they obscure the view of the Universe at visible-light wavelengths. Accordingly, the ATLASGAL map includes the denser central regions of our Galaxy, in the direction of the constellation Sagittarius, that are otherwise hidden behind a dark shroud of dust clouds. The map also shows thousands of dense dust clumps, many never seen before, which mark the future birthplaces of massive stars. The clumps are typically a couple of light-years in size and have masses of between ten and a few thousand times the mass of our Sun. THE NATURE OF 'BLOBS' AND THE LIMIT TO THE SIZES OF GALAXIES Chandra X-Ray Center About ten years ago, astronomers who were making surveys of young distant galaxies found great reservoirs of hydrogen gas, which they called 'blobs', near them. The blobs glowed brightly in optical light, but their nature and the source of the energy that powered the glow and were unknown. It is thought that recent observations by the Chandra X-ray satellite, the Spitzer infrared satellite, and other instruments have answered the main questions. They have observed 29 blobs in one particular field. The blobs appear to be galaxies in course of formation, several hundred thousand light-years across, and are seen as they were when the Universe was only about two billion years old. In five of the blobs, Chandra saw a point-like source of X-ray emission, which has been taken to be the signature of a growing super-massive black hole. Other observations indicate that there is a lot of star-formation going on in the blobs. The radiation and outflows from the black holes and the star formation is calculated to be sufficient to light up the surrounding hydrogen in the blobs. It may also be enough to arrest the infall of further gas and prevent the blobs growing indefinitely into galaxies much larger than are actually observed; some such process must be at work to limit the sizes of individual galaxies. ULYSSES SPACECRAFT ENDS MISSION JPL Ulysses, a joint NASA/ESA mission, ceased operations on June 30. The spacecraft charted the unexplored regions of space above the poles of the Sun for more than 18 years. When the space shuttle Discovery launched Ulysses in 1990, the spacecraft had an expected lifetime of 5 years. It gathered information about the heliosphere -- the bubble carved in space by the solar wind -- and made nearly three complete orbits of the Sun in a plane almost perpendicular to the ecliptic.. The probe revealed for the first time the three-dimensional character of Galactic cosmic radiation, energetic particles produced in solar storms and the solar wind. In addition to measuring the solar wind and charged particles, Ulysses measured small dust particles and neutral gases that penetrate into the heliosphere from local interstellar space. It also had three chance encounters with comet tails, registered more than 1,800 cosmic gamma-ray bursts, and provided findings for more than 1,000 scientific articles and two books. On June 10, Ulysses became the longest-running ESA-operated spacecraft, overtaking the International Ultraviolet Explorer, which logged 18 years and 246 days of operations. Ulysses' orbital path is carrying the spacecraft away from the Earth. The ever-widening gap has progressively limited the amount of data transmitted, and the project managers, with the concurrence of ESA and NASA, decided that it was an appropriate time to end the mission.. 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/ Astronomica is sponsoring the SPA Electronic News Bulletin. SPA MEMBERS -- Get 10% off all purchases -- simply use voucher code SPA10 when you buy from our website http://www.astronomica.co.uk Astronomica is a firm set up by astronomers to sell astronomical equipment at affordable prices, and offers SPA members a 10% discount on all products. Details of any special offers can be found at http://www.astronomica.co.uk