*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 262 2009 March 1 ==================================================== 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/ FIREBALLS & METEORITES ROUND-UP By Alastair McBeath, SPA Meteor Section Director Although February has been fairly quiet for UK fireball observations, as indicated by our Recent Fireball Sightings webpage (at http://snipurl.com/cthdv ), this has not been the case elsewhere. Indeed February 13-14 especially proved quite a global date for imaged fireballs, with spectacular events caught at 20:03 (from Italy; magnitude about -17!), 20:26 (Italy), 21:52 (Italy), 02:11 (France), around 03h (Texas, USA) and 05:16 UT (Italy once more). The 20:03 UT Italian meteor and the Texas fireball at least were both initially suspected of having dropped meteorites, and it seems now the first meteorites may have been recovered from the Texan fall. The French image was made from Normandy, and with visual sightings from Paris and the area north of there, it is possible this 02:11 UT event might have been seen from southern Britain as well, but no reports of it have arrived from here so far. Links to sites with images of all these fireballs, plus more details (notably on the Texas event) can be found on the SPA's General Chat Forum, at http://snipurl.com/cthgr . Another possible meteorite-dropping brilliant fireball came down over Finland at 21:39 UT on February 16-17. Again this was recorded on video, and searches were underway soon afterwards in the hopes of recovering any meteorites before fresh snow fell there. As with the cluster of fireballs in mid January (see ENB 260, archived at http://snipurl.com/cthhd ), there is no evidence as yet to suggest any of the February fireballs were related to one another, other than by their coincidentally happening relatively close together in time. Grateful thanks go to our meteor-expert correspondents Ferruccio Zanotti (also one of the lucky Italian video observers!), Karl Antier and Esko Lyytinen (who caught the Finnish fireball on video) for details and comments on the Italian, French and Finnish events respectively. Assistant Meteor Director David Entwistle has posted some additional notes to the Observing Forum's topic on the Canadian fireball and meteorite fall of last November 20, at http://snipurl.com/ctli4 . The fall is now called the Buzzard Coulee meteorite, from the place near which the objects fell, and David drew attention to three professional papers to be presented at the 40th Lunar and Planetary Science Conference in Texas in late March, concerning the chemistry and structure of the H4 chondrites recovered, and the observed characteristics of the originating fireball. This fireball last featured in ENB 258 ( http://snipurl.com/bwzgd ). David added a note to the Forum's topic on the predicted fireball over Sudan of last October 7 too (this was most recently mentioned in ENB 255, http://snipurl.com/ctlle ; the Forum topic is at: http://snipurl.com/ctlqq [www_popastro_com] ), with a link to a preliminary report in the online New Scientist that suggested meteorite fragments had been recovered associated with this fireball. A team of searchers led by Dr Muawia Shaddad from Khartoum University was credited with the find, using data from NASA to locate the probable fall region. No details on the nature of the fragments are yet available, however. Fireball reports made from the British Isles and nearby are always welcomed by the Meteor Section. A fireball is any meteor that reaches at least magnitude -3; Venus, the brilliant planet currently dominating the evening sky, is presently magnitude -4.8. The information to send me is described on the new-look "Making and Reporting Fireball Observations" page of the SPA website, at: http://snipurl.com/cto9m . A verbal description which contains all the essential details is fine, but for those who prefer a more structured approach, a new e-mailable fireball report form is also available. STARS WERE CROWDED IN THE EARLY UNIVERSE RAS Here and now, we are used to the idea that even the nearest stars are light-years away from the Sun, but scientists at the University of Bonn think that things were very different in the early Universe. In particular, ultra-compact dwarf galaxies (UCDs), a recently discovered class of object, may have had stars packed together a thousand times more closely than in the solar neighbourhood. UCDs were discovered in 1999. They are about 60 light-years across, which is less than 1/1000th the diameter of the Milky Way. Astronomers believe that UCDs were created when more normal galaxies collided in the early Universe. But oddly, UCDs clearly have more mass than the light from the stars that they contain would imply. Sometimes, exotic dark matter has been suggested to explain the apparently missing mass, but it is now not thought to gather in sufficient quantities within a UCD. The astronomers think that at one time, each UCD had an incredibly high density of stars, with perhaps a million in each cubic light-year. The stars would have been close enough to merge from time to time, creating many much more massive stars in their place. Those more massive stars consume hydrogen much more rapidly, before ending their lives in supernova explosions. All that then remains is either a super-dense neutron star or sometimes a black hole. So in today's UCDs, a good part of their mass is made up of such dark remnants, largely invisible to Earth-based telescopes but fossils of a more dramatic past. To have such vast numbers of stars packed closely together is quite unlike anything we see today. An observer on a hypothetical planet inside a UCD would have seen a 'night' sky as bright as day on Earth. EXTREME GAMMA-RAY BURST NASA The first gamma-ray burst to be seen at high resolution from the Fermi gamma-ray space telescope had the greatest total energy, the fastest motions and the highest-energy initial emissions ever seen. That explosion, designated GRB 080916C, occurred on 2008 Sept. 16 in the constellation Carina. Fermi's other instrument, the gamma-ray burst monitor, simultaneously recorded the event. Together, the two instruments provided a view of the blast's initial, or prompt, gamma- ray emission at energies between 3,000 to more than 5 billion times that of visible light. Gamma-ray bursts are the Universe's most luminous explosions. Astronomers believe most of them occur when massive stars run out of nuclear fuel. As a star's core collapses into a black hole, jets of material blast outward at nearly the speed of light. The jets bore all the way through the collapsing star and continue into space, where they interact with gas previously shed by the star and generate bright afterglows that fade quickly. The first thing astronomers try to do after a gamma-ray burst is scramble to detect the fading afterglow, whose optical spectrum can indicate the distance to the blast site. That is crucial information to enable calculation of a burst's power. Nearly 32 hours after the blast, a group at the Max-Planck Institute found the afterglow of GRB 080916C. Working quickly, before it could fade away, they measured the afterglow's spectrum with the 2.2-m telescope at the European Southern Observatory in Chile. According to their data, the explosion took place 12.2 billion light-years away. With the distance known, Fermi team members calculated that the blast would have exceeded the power of approximately 9,000 ordinary supernovae if the energy were emitted equally in all directions. That is a standard way for astronomers to compare events even though gamma-ray bursts emit most of their energy in tight jets. Coupled with the Fermi measurements, knowledge of the distance also helps determine the speed of the gamma-ray-emitting material. Within the jet of this burst, gas bullets must have moved at least 99.9999 percent the speed of light. This burst's tremendous power and speed make it the most extreme recorded to date. 25-METRE GIANT MAGELLAN TELESCOPE Carnegie Institution The Giant Magellan Telescope (GMT) Corporation has announced that an agreement has been made to construct and operate the GMT at Las Campanas Observatory in the Chilean Andes. It is to have seven co-mounted 8.4-metre primary mirrors and an adaptive secondary system, which should give it the resolving power of a single 24.5-metre (nearly 1000-inch) primary mirror. Construction will begin in 2012 and is scheduled for completion around 2019. JUPITER IN SPACE AGENCIES' SIGHTS BBC News NASA and the European Space Agency have decided to forge ahead with an ambitious plan to send a probe to Jupiter and its icy moons Europa and Ganymede. The proposal could be the agencies' next 'flagship' endeavour, to follow on from the successful Cassini-Huygens mission to Saturn. Officials had been considering the Jupiter mission along with a venture to Saturn's moons Titan and Enceladus. Although the Jupiter-system mission has been chosen for an earlier flight opportunity, a Saturn-system mission clearly remains a high priority for the scientific community. The team suggests that the US and Europe both send orbiters. NASA would despatch the Europa orbiter and ESA the Ganymede one. The two spacecraft would occasionally conduct joint observations, but only NASA's probe would spend time around Europa, which is known to have a severe radiation environment. A previous ESA feasibility study into a Europa mission gave spacecraft orbiting that moon a lifetime of just 66 days. NASA plans to use specific shielding to protect sensitive electronic systems; it is confident now that its spacecraft could operate for several months in orbit and obtain complete coverage both of the surface and the interior. The two spacecraft would end their missions by crashing into their respective moons. SKYLON GETS CASH BOOST BBC News An innovative UK launcher concept is to get 1m euros from the European Space Agency. The Skylon space-plane would take off from a conventional aircraft runway, carry over 12 tons into orbit and then return to land on the same runway. The money will help prove the vehicle's core technologies, including its Sabre air-breathing rocket engine. Alan Bond, owner of the company behind the project, believes that its reusable launcher could fly within 10 years. The Holy Grail to transform the economics of getting into space is to use a truly re-useable space-plane capable of taking off from an airport and climbing directly into space, delivering its satellite payload and automatically returning safely to Earth. The Skylon technology is part jet engine, part rocket engine. It burns hydrogen and oxygen to provide thrust, but in the lower atmosphere the oxygen is taken from the atmosphere. At high speeds, that requires the engine to cope with 1,000-degree gases entering its intake. 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/