*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 292 2010 July 18 ==================================================== 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 BOÖTIDS - FURTHER DETAILS By Alastair McBeath, SPA Meteor Section Director It has remained unclear whether any significant June Boötid activity occurred on June 23-24, as had been predicted in advance, further to the preliminary discussion given last time. An examination of the results reaching the Meteor Section directly, coupled with observations reported on the IMO-News and Meteorobs e-mailing lists, has suggested that Zenithal Hourly Rates (ZHRs) between roughly 22h-06h UT on June 23-24 averaged 9 +/- 2, far below the anticipated ~20-50. Video rates for the shower then averaged about two sporadics per June Boötid, which while a rather crude estimated method, did imply quite weak Boötid activity overall. Radio results provided directly, plus those reported in June's Radio Meteor Observation Bulletin (RMOB No. 203), showed little sign of anything unusual on June 23-24, and nothing at all on June 27, another potential date for June Boötid activity based on previous years' events (see ENB 290, archived at: http://snipurl.com/zicst . There was an indication of weak radio-meteor activity potentially due to the Boötids between ~11h-13h UT on June 23 in some of the data collected by observers in North America (European observers had no suitable radiant elevation for the shower then). Unfortunately, the relatively few sets of radio observations not affected by summertime Sporadic-E interference (on which see also ENB 290), and the paucity of data collected by other techniques, made these results tentative only. It is though interesting that none found the kind of easily-detected, sustained rates found with the shower at both its other recent outbursts, in 2004 and 1998. The observers whose data was used in preparing this analysis, including those from the two e-mail lists, RMOB 203 (provided by Editor Chris Steyaert; available at: http://www.rmob.org ), and the North American Meteor Network (NAMN; see http://www.namnmeteors.org ; results and additional discussion from Network leader Mark Davis) were as follows, where "R" means radio, "Vi" video and "V" visual results were provided by that person: Enric Algeciras (Spain; RMOB; R), Orlando Benitez (Canary Islands; RMOB; R), Michael Boschat (Nova Scotia, Canada; RMOB; R), Jeff Brower (British Columbia, Canada; R; some data also in RMOB), Willy Camps (Belgium; RMOB; R), Johan Coussens (Belgium; RMOB; R), Gaspard De Wilde (Belgium; RMOB; R), Kurt Fisher (Utah, USA; RMOB; R), Karl-Heinz Gansel (Germany; RMOB; R), Patrice Guérin (France; RMOB; R), Javor Kac & colleagues (Slovenia; Vi + V), Paul Martsching (Iowa, USA; NAMN; V), Mike Otte (Illinois, USA; RMOB; R), Jürgen Rendtel (Germany; V), Steve Roush (Arizona, USA; RMOB; R), Wayne Sanders (British Columbia, Canada; RMOB; R), Andy Smith (England; RMOB; R), Chris Steyaert (Belgium; RMOB; R), Enrico Stomeo (Italy; Vi), Dave Swan (England; RMOB; R), Istvan Tepliczky (Hungary; RMOB; R + Vi), Michel Vandeputte (Belgium; V), Felix Verbelen (Belgium; RMOB; R). My grateful thanks go to all involved for their efforts, and also to Rich Taibi in Maryland, USA, for additional discussions of some of the early radio results especially. Any further June Boötid observations would be very welcome still! JUNE'S DAYTIME METEOR SHOWERS By Alastair McBeath, SPA Meteor Section Director Three major, annual showers have maxima due in June, all with radiants near the Sun, and detectable from Britain only by radio in the daytime. Details are given each year for them in our June meteor activity webpage. In general, radio observers have managed to follow something of them for many years, when summertime interference has permitted. All three were discovered by radar from Jodrell Bank in 1947. Theoretically, the Arietids should peak on June 7, with past estimates implying their equivalent visual ZHRs could be around 60. Similarly, the Zeta Perseids should reach maximum on June 9 (visual-equivalent ZHRs ~40). Both these radiants are so close together in the sky, and their maxima follow one another so quickly, it is impossible for amateur radio-meteor systems to separate the two. The final major daytime shower in June is the Beta Taurids, with an often ill-defined peak around June 28, best visual-equivalent ZHRs about 25. This is the Earth's second annual encounter with the Taurid showers we see visually overnight each year in the autumn. Drawing on extra data provided by Jeff Brower in Canada, and the observers listed above from RMOB 203, analyses were carried out to try to establish the more likely near-maximum activities for all three sources. A disappointingly large number of European radio datasets were badly affected by Sporadic-E throughout the first half of June especially, leading sometimes to entire days'-worth of results being lost, a great frustration for both observers and analysts. Consequently, the findings here are not as securely-established as might be preferred. With that caveat in mind, a generally heightened level of radio meteor activity was found in the majority of the surviving results between June 6 and 12, due to daytime activity. The most probable daylight peaks fell on June 8 and 11 within that time, but neither was particularly obvious. These more probable peak dates were in-line with the Section's analyses from previous years, using results going back to the early 1990s, which have often indicated the Arietid and Zeta Perseid peaks could be happening around a day later than predictions suggested (which predictions were based chiefly on radar results collected sporadically during the late 1940s to early 1970s). Gaps in the data created continued difficulties for the Beta Taurid analysis, though a daylight peak can be inferred as falling between June 24 and 28, likely due chiefly to this radiant or one nearby. Within that period, a majority of the systems less-affected by interference gave a probable peak on June 25 or 26. There were also indications activity may have been rising again on June 30, something which will need checking once all July's radio data is available. As noted already, an ill-defined peak has seemed to be a feature of the Beta Taurids, and previous examinations have hinted that there may be more than one possible maximum date in late June to early July. Again, my most grateful thanks go to all the observers involved, with commiserations to those whose data was badly-affected by Sporadic-E. VERY SLOW FIREBALL IMAGED OVER FRANCE By Alastair McBeath, SPA Meteor Section Director An unusually long-lasting, very slow fireball that remained visible for around 7-10 seconds, occurred over southern France on June 5-6, at 22:37 UT. It was reported to the Section directly, but French meteor and fireball analyst Karl Antier received a great many more reports of it, including news that the event had been caught on video by the Italian Video Meteor Network. The video record is available at: http://snipurl.com/zivw5 . Ordinarily, the SPA Meteor Section collects data chiefly on fireball events spotted from the British Isles and places nearby, but any British holidaymakers who were in France at the time and saw this event are welcome to send-in a full report, if they have not already provided details to Karl or the Section. Copies of such sightings will be forwarded to Karl as well, to assist with his analysis. Details on what to report, including an e-mail fireball report form, can be found on the "Making and Reporting Fireball Observations" webpage, at: http://snipurl.com/u8aer . MAIN METEOR PROSPECTS FOR JULY-AUGUST By Alastair McBeath, SPA Meteor Section Director July-August brings one of the stronger near-ecliptic meteor showers during the year, the Delta Aquarids, whose maximum ZHRs of about 15-20 are usually achieved for a day or two around July 28-30. Regrettably, the shower radiant's southerly Declination (not unexpectedly, it lies near the star Delta Aquarii in late July), means observed meteor numbers are always much lower than the ZHRs from Britain, though rare Delta Aquarid meteors can be very bright at times. Full Moon on July 26 ruins any possibility for dark-sky coverage of the likely peak from the UK this summer, though lower activity of these medium-speed meteors is usually seen from circa July 12 till August 19. For more information and a radiant chart, see July's meteor activity webpage at: http://snipurl.com/zjivm . By contrast, the Perseid maximum fares much better, thanks to new Moon on August 10. It is due between 18:30 UT on August 12 to 07:00 UT on August 13 this year, most likely at some stage from about 23:30 to 02:00 UT. It should produce ZHRs of around 100. This most plausible peak interval is very favourable for Britain, as the Perseid radiant, a few degrees northeast of the "Double Cluster" near the maximum, can be usefully-observed from roughly 22h UT onwards, culminating after dawn. Perseids are swift, often bright, and commonly trained meteors, and those hoping to image some may find their capture rates enhanced by aiming towards And-Cas-Peg-Cyg. The shower is active from July 17 or so through to August 24, and although rates are always lower away from the peak, observed activity is usually good to very good for a couple of days before the maximum plus a day or so afterwards. This is important to remember if it seems the actual peak night may be clouded-out. Further information and a Perseid radiant chart is on the August meteor activity webpage, http://snipurl.com/zjjbd . Good luck, and clear skies! PLANETS By Andrew Robertson, SPA Planetary Section Director I have had no reports of planetary observations since my last notice, which is hardly surprising since it doesn't get reasonably dark until after many people have gone to bed and there haven't been any planets on prominent display. You can see Venus low in the west after sunset, and Mars & Saturn as it gets a bit darker, but they're all low down and don't really offer much detail although they are still nice to see with the unaided eye and binoculars. On July 30, Mars and Saturn are in conjunction less than 2 degrees apart, with the much brighter Venus 8 degrees away below and to the right. Compared to Venus's brilliance of mag -4.1 though, Saturn is only mag 1.1 and Mars 1.5. By August 7 all three are within 3 or 4 degrees of each other but are only about 8 degrees above the horizon half an hour after sunset so still in a brightish sky; they then effectively fade from view for this apparition. Jupiter, however, is coming to prominence, rising in the east in the early hours. I had a reasonable view of it. albeit low down still. at 1am BST on July 15. The NEB (north equatorial belt) is very prominent and there is a trace of the 'vanished' SEB. I am also starting to see observations from other sources, what I would describe as the die-hard amateurs who observe at every opportunity and produce semi-professional results. At 2am BST Jupiter will have risen to 22 degrees altitude on July 18, 28 degrees on July 31 and 33 degrees on August 14. Worth making an effort, as you can never know when that SEB is going to make a dramatic re-appearance! Uranus is not far from Jupiter throughout this next 4-week period, just under 3 degrees to Jupiter's right (west). At high power through a telescope you can see a tiny greenish to slightly bluish disc and during moments of good seeing you can see limb darkening which I observed myself a few nights ago in the early hours. Neptune comes to opposition on August 20, but as it is low down in Capricornus and presents a tiny blue disc about 2".5 in diameter there is not much to be seen. Any reports of observations would be most welcome via: http://popastro.com/planet/contact/ I post a selection of members' observations on the SPA web site, and they can be viewed on the Planetary Section's web page at: http://popastro.com/planet/category/observations/ WAS VENUS ONCE A HABITABLE PLANET? ESA If Venus once had oceans, it might have been a habitable planet similar to the Earth. The Earth and Venus seem completely different today: here, we have a lush, clement world teeming with life, while Venus is hellish, its surface roasting at high temperatures. But the two planets are nearly identical in size, and now, thanks to the Venus Express orbiter, planetary scientists are seeing other similarities. One difference stands out: Venus has very little water. Were the contents of the Earth's oceans to be spread evenly across the world, they would create a layer 3 kilometres deep. If you could condense the amount of water vapour in Venus' atmosphere onto its surface, it would create a global puddle just 3 centimetres deep. Yet, billions of years ago, Venus probably had more water. Venus Express has found that the planet has lost a large quantity of water into space. The loss occurs because ultraviolet radiation from the Sun streams into Venus' atmosphere and breaks up the water molecules into atoms, which then escape into space. Venus Express has measured the rate of escape and found that roughly twice as much hydrogen as oxygen is escaping. It is believed that water is the source of the escaping ions. It has also shown that deuterium, a heavy isotope of hydrogen, is progressively enriched in the upper layers of Venus' atmosphere because the heavier isotope does not escape so easily. Everything points to there having been large amounts of water on Venus in the past, but that does not necessarily mean that there were oceans on the planet's surface. A newly developed a computer model suggests that the water was largely atmospheric and existed only during the earliest times when the surface of the planet was completely molten. Whether that is true or not is a key question. If Venus ever did possess surface water, it may possibly have had an early habitable phase. It is also possible that colliding comets brought additional water to Venus after the surface crystallized, and that they created bodies of standing water in which life might have been able to form. ROSETTA TRIUMPHS AT ASTEROID LUTETIA Science Daily ESA's Rosetta mission has returned the first close-up images of the asteroid Lutetia, showing that it is probably a primitive survivor from the violent birth of the Solar System. The images show that Lutetia is heavily cratered, having suffered many impacts during its 4.5 billion years of existence. As Rosetta drew close, a bowl-shaped depression stretching across much of the asteroid rotated into view. The images show that Lutetia is an elongated body, with its longest dimension around 130 km. The pictures come from Rosetta's OSIRIS instrument, which combines a wide-angle and a narrow-angle camera. At closest approach, details down to a size of 60 m can be seen over the entire surface of Lutetia. Rosetta raced past the asteroid at 15 km/s, completing the fly-by in just a minute, but the cameras and other instruments had been working for hours and in some cases days beforehand, and will continue afterwards. Ground telescopes have shown Lutetia to present confusing characteristics. In some respects it resembles a 'C-type' asteroid, a primitive body left over from the formation of the Solar System. In others, it looks like an 'M-type', which have been associated with iron meteorites, are usually reddish and are thought to be fragments of the cores of much larger objects. The fly-by marks the attainment of one of Rosetta's main scientific objectives. The spacecraft will now continue to a 2014 rendezvous with its primary target, Comet Churyumov-Gerasimenko. It will then accompany the comet for months, from near the orbit of Jupiter down to its closest approach to the Sun. In 2014 November Rosetta will release its Philae lander to land on the comet nucleus. PROCESSES OF MASSIVE-STAR FORMATION Joint Astronomy Center, Hilo, Hawaii Astronomers using the United Kingdom Infrared Telescope (UKIRT) believe that they have identified the leading mechanism by which massive stars form in our Galaxy: by collecting matter via discs around their equatorial regions. That was revealed by the detection of gas outflows and shocked regions associated with massive young stars in formation, located in clouds of gas and dust. Scientists know that lower-mass stars like our Sun form by gravitational collapse of material inside clouds of gas and dust in space. The gas and dust spiral down onto the equatorial regions of the young star by a process known as accretion. At the same time, the accreting young stars drive high-velocity jets of gas ('outflows') which radiate at infrared wavelengths, so astronomers can use observations in the infrared to search for not only the youngest stars, but also evidence of the accretion process. There have been misgivings over whether stars with masses larger than 10 times the mass of our Sun form in the same way, as it has been supposed that the extreme energy output of such stars, which start nuclear burning in their cores even before they complete their growth through accretion, would prevent further growth by blowing away the accretion discs. Hence, alternative mechanisms such as mergers of lower-mass stars have been suggested as the main way in which massive stars form. The presence or absence of outflows from massive young stars should tell us whether accretion or some other method leads to their formation. Most of the massive young stars being formed are confined to the Galactic plane and are located in molecular clouds extending over several or even tens of light-years. They are hidden behind large amounts of gas and dust, which hamper their detection at visible wavelengths but are penetrated by infrared light. The UKIRT observers looked at 50 bright young stellar objects; 38 of them showed molecular line emission, in most cases arising from outflows. Within the sample, the outflows are seen to be well-defined irrespective of the energy output of their central young stars and are nearly as well-defined as those from low-mass stars. The outflows appear to be driven by jets like those from low-mass stars. The astronomers have concluded that massive stars up to at least 30 times the mass of the Sun form through disc accretion. ORIGIN OF MILKY WAY'S ANCIENT STARS RAS Scientists at Durham and collaborators at the Max Planck Institute and Groningen University in Holland have tried to make computer simulations of the beginnings of our Galaxy. The simulations have suggested that ancient stars found in a stellar halo of debris surrounding the Milky Way were ripped from smaller galaxies by the gravitational forces generated by colliding galaxies. Cosmologists think that the early Universe was full of small galaxies which led short and violent lives, colliding with one another and leaving behind debris which eventually settled into more familiar-looking galaxies like the Milky Way. UNRAVELLING THE NATURE OF HANNY'S VOORWERP ASTRON, Dwingeloo, Netherlands A group of researchers has made high-resolution radio observations of the region of space around Hanny's Voorwerp (Hanny's Object), the curious, greenish gas cloud discovered by Dutch schoolteacher Hanny van Arkel. The astronomers undertook an observational campaign at radio wavelengths in which several radio telescopes across Europe and the United Kingdom were linked together in real time in order to obtain a detailed picture of the central region of the adjacent galaxy IC 2497. They observed a field a few arcseconds across, with a spatial resolution of about 70 milliseconds. The observations show two bright and very compact sources with broadband spectra that argue for the existence of an active galactic nucleus (AGN) at the centre of IC 2497. One of the sources appears to be identifiable with a supposed black hole at the centre of the AGN itself, while the other is likely to be the result of an energetic jet expelled by the black hole and now interacting with dense gas that surrounds IC 2497. The radiation from the AGN is believed to heat Hanny's Voorwerp to a temperature above 10,000°. It also appears that surrounding the AGN is a lot of extended radio emission. The researchers argue that it is associated with a nuclear starburst. Astronomers knew that IC 2497 is forming stars, but were surprised to find that the star formation seems to be concentrated in a very small central region, only 1000 parsecs across. It is fairly unusual to find both vigorous star formation and AGN radio activity in the same system and on similar scales. The radio observations indicate that in the central region IC 2497 is producing stars with a total mass of the order of 70 Suns every year -- a high rate, about 6 times higher than in the nearby starburst galaxy M82. The observations support the group's earlier hypothesis that a hidden AGN in the centre of IC 2497 is ionizing a distinct region of gas that surrounds that galaxy. That distinct region is what is known as Hanny's Voorwerp. Such phenomena must be rare in the local Universe because they depend on a specific geometry of the observer, galaxy, and gas, plus the interaction of several galaxies in the field in order to fuel the AGN and the starburst, and to create the gas reservoir that forms part of the Voorwerp. VOYAGER SPACECRAFT AT 12,000 DAYS Science Daily On June 28, the Voyager 2 spacecraft had been operating continuously for 12,000 days. For nearly 33 years, the venerable spacecraft has been returning data about the outer planets, and the characteristics and interaction of the solar wind between and beyond the planets. Among its findings, Voyager 2 discovered Neptune's Great Dark Spot and its 450-m/s winds. The two Voyager spacecraft have been the longest continuously operating spacecraft in deep space. Voyager 2 was launched on 1977 August 20; Voyager 1 was a little later, on 1977 September 5, so it reached its 12,0000 days on July 14. The two spacecraft are the most distant man-made objects, out at the edge of the heliosphere -- the bubble that the Sun creates around the Solar System. Having travelled more than 21 billion kilometres on its winding path among the planets towards interstellar space, Voyager 2 is now nearly 14 billion kilometres away; a signal from the ground, travelling at the speed of light, takes about 12.8 hours one-way to reach it. Voyager 1 is even further away, more than 17 billion kilometres. Owing to holidays, the next scheduled edition of the bulletin will appear on August 15. 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/