*********************************** The SOCIETY for POPULAR ASTRONOMY *********************************** ==================================================== Electronic News Bulletin No. 285 2010 March 28 ==================================================== 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/ CHANNEL ISLAND FIREBALLS By Alastair McBeath, SPA Meteor Section Director Two notably bright fireballs seem to have been observed from the Channel Isles on March 21-22, one at 20:05 UT, the other around 22:00. However, most of the sightings have come in the form of brief media reports and online comments only, and the information so far has not been clear always as to where some observers were, or what time their sightings were made. Information reaching the Meteor Section directly from witnesses that night suggested there were indeed two separate meteors involved. Most people apparently spotted just the later event. Details on where the objects may have overflown have been rather sketchy too. The 20:05 fireball may have moved roughly north to south, perhaps over the Cotentin Peninsula, or the southern Channel east of there and other parts of Normandy in northern France. The ~22:00 meteor may have passed from somewhere east of Jersey to south of that island. Witness' notes on the events that evening are available on media webpages from Guernsey (at: http://snipurl.com/v3sw4 ) and Jersey (at: http://snipurl.com/v3sxu ) respectively, but note that the media sources, and most early comments, were based on the belief that just a single event was involved, probably that at 22:00. All additional sightings of these or any other fireballs (meteors of magnitude -3 or brighter), made from the British Isles and nearby, would be welcomed by the Section. The minimum details required are: 1) Exactly where you were (give the name of the nearest town or large village and county if in Britain, or your geographic latitude and longitude if elsewhere in the world); 2) The date and timing of the event in UT (remember to subtract one hour from current clock time, BST, to get UT - and don't forget, astronomically the date changes at UT, not BST, midnight!); and 3) Where the fireball started and ended in the sky, as accurately as possible, or where the first and last points you could see of the trail were if you did not see the whole flight. More advice and a fuller set of details to send (including an e-mail report form) are given on the "Making and Reporting Fireball Observations" page of the SPA website, at: http://snipurl.com/v3ss5 . PLANETS By Andrew Robertson, SPA Planetary Section Director A white spot was imaged on Saturn on 2010 March 06 by Tomio Akutsu, and subsequently by Paul Maxon and Chris Go. It is in the southern South Tropical Zone. Akutsu's latest images of March 14 indicate the spot is now quite bright and could potentially be seen visually in moderate-sized amateur telescopes under good conditions. You can access Akutsu's images on the ALPO_Japan web site: http://snipurl.com/v1aje Information courtesy of BAA News Circular. Saturn reached opposition on 22nd March and is ideally placed for observation in the late evening. The above just goes to confirm that there's always something happening on the planets - they're always worth checking out whenever you get the chance. Mercury undergoes it's best evening apparition of the year in the first two weeks of April. It reaches greatest Eastern Elongation on 9th April visible low down in the west after sunset. Between 6th & 11th of April it will be at an altitude of 11 degrees 40 mins after sunset. Venus is getting higher in the west and will be slightly higher and to the left of Mercury. Any observations will be most welcome and can be forwarded to me at: planets@popastro.com JUPITER'S RED SPOT ESO Astronomers have been observing Jupiter's Great Red Spot, an elliptical storm about 25,000 miles across, for hundreds of years. Now, they have been using the Very Large Telescope to take thermal (far-infrared) images of it. They show that the most intense orange-red central part of the spot is about 3 to 4 degrees warmer than the -160C environment around it. That temperature difference might not seem much, but it is enough to allow the storm circulation, usually counter-clockwise, to shift to a weak clockwise circulation in the very middle of the storm. Dark lanes at the edge of the storm appear to mark places where gases are descending into the deeper regions of the planet. We still do not know what chemicals or processes are causing the red colour, which now seems to be related to changes in the environmental conditions right in the heart of the storm. NEW EXOPLANET 'MORE LIKE ONE OF OURS' BBC News A planet that has been named CoRoT-9b has been discovered by the CoRoT satellite (a mission led by the French space agency, Centre National d'Itudes Spatiales) around a star 1500 light-years away. It is the size of Jupiter and has an orbit similar to that of Mercury. More than 400 planets have been discovered outside the Solar System so far, but this is the first one where it even makes sense to apply models developed for planets within our Solar System -- the others are either extremely hot, being very close to the central star, or they are on eccentric orbits, taking them close to and far from the star so they have extreme temperature ranges. The surface temperature is estimated (seemingly with no great accuracy) to be between about -20 and +160C. During its orbit of 95 days it transits (passes in front of) its star for about eight hours. The fact that it transits ought to enable astronomers to obtain much more information about it than they could otherwise. WHITE-DWARF STAR SYSTEM EXCEEDS MASS LIMIT Yale University Cosmologists use Type Ia supernovae -- violent explosions of the dead cores of white-dwarf stars -- as a cosmic yardstick with which to measure distances, in the hope ultimately of understanding the past and future development of the Universe. It has been thought that white dwarfs could not exceed what is known as the Chandrasekhar limit, a critical mass about 1.4 times that of the Sun, before exploding in a supernova. That uniform limit has been considered a key tool in measuring distances to supernovae. Since 2003, however, four supernovae have been discovered that were so bright that cosmologists felt impelled to wonder whether their white dwarfs had surpassed the Chandrasekhar limit. Now a collaboration of American and French physicists claims to have determined the mass of the white dwarf that resulted in one of the rare supernovae, called SN 2007if, and confirmed that it exceeded the Chandrasekhar limit. They also discovered that the unusually bright supernova had not only a central mass, but a shell of material that was ejected during the explosion, as well as a surrounding envelope of pre-existing material. The team has made estimates of the masses of those three components separately. The star itself appears to have had a mass of 2.1 times the mass of the Sun (plus or minus 10%), putting it appreciably above the limit. Scientists think that SN 2007if may have resulted from the merging of two white dwarfs, rather than the explosion of a single white dwarf that was not obeying the rules. Naturally they hope to study the other apparently super-Chandrasekhar supernovae to see whether they, too, could have involved a merger of two white dwarfs, or whether it is necessary to conclude that stars with masses above the limit could somehow exist without collapsing under their own weight. RAPID STAR FORMATION IN EARLY GALAXY RAS Scientists have found that in the early Universe a massive galaxy was creating stars like our Sun up to 100 times faster than the modern-day Milky Way. Owing to the length of time it has taken its light to reach the Earth, the galaxy, known as SMM J2135-0102, is seen now as it would have appeared 10 billion years ago -- three billion years after the Big Bang. The galaxy is seen better than it would ordinarily be, because it is magnified by the 'gravitational lens' of other galaxies in the line of sight between it and us. There were four discrete star-forming regions within it, and each one was more than 100 times brighter than star-forming regions like the Orion Nebula in our own Galaxy. The scientists estimate that the observed galaxy was producing stars at a rate equivalent to 250 Suns per year. This is not the first time that an early galaxy has been observed producing stars at a rate far higher than seems to be the norm now. SPITZER IDENTIFIES PRIMITIVE BLACK HOLES JPL Astronomers using the Spitzer space telescope have come across what appear to be two of the earliest and most primitive quasars, born in a dust-free medium and at the earliest stages of evolution. Quasars are small objects, that emit enormous amounts of energy, seen at the centres of some galaxies, and are supposed to be powered by the infall of material into super-massive black holes in their cores. The present-day Universe is very dusty, but scientists believe that there was no dust in the very early Universe -- so the most primitive quasars should also be dust-free. But nobody had seen such immaculate quasars until now. Spitzer has identified two -- the smallest on record -- about 13 billion light-years away. The quasars, called J0005-0006 and J0303-0019, were first discovered in visible light in the Sloan Digital Sky Survey. The discovery team also observed X-rays from one of the objects. X-rays, ultraviolet and optical light stream out from quasars as the gas surrounding them is swallowed by the black hole. The high luminosity of quasars makes them detectable literally at the edge of the observable Universe. Spitzer measured infrared light from the two objects along with 19 others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a super-massive black hole with a mass of more than 100 million suns. Of the 21 quasars, J0005-0006 and J0303-0019 lacked characteristic signatures of hot dust. Those early black holes were forming around the time when the dust was first forming in the Universe, less than one billion years after the Big Bang. The primordial Universe did not contain any molecules that could coagulate to form dust; the elements necessary for dust were produced later by stars. The astronomers also observed that the amount of hot dust in a quasar increases with the mass of its black hole. As a black hole grows, dust has more time to materialize around it. The black holes at the cores of J0005-0006 and J03031-0019 have the smallest measured masses known in the early Universe, indicating that they are particularly young, at a stage when dust has not yet formed around them. 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/ 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