Universe shines twice as bright

The universe is shining twice as brightly as previously thought, astronomers have discovered. A team of British, Australian and German scientists found that half the light is being obscured by clouds of dust. Astronomers have long been aware that much of the universe is made up of dust. But they had not realised the extent to which it was masking what we see. The team was led by Dr Simon Driver of the University of St Andrews, in Scotland. He said: "For nearly two decades we've argued about whether the light that we see from distant galaxies tells the whole story or not. "It doesn't. In fact only half the energy produced by stars actually reaches our telescopes directly. The rest is blocked by dust grains." The dust absorbs starlight, then re-emits it in a glow. Astronomers realised their old ideas about the universe were flawed because the dust seems to be emiting more energy than possible with the stars known to exist. Dr Driver added: "You can't get more energy out than you put in so we knew something was very wrong. Even so, the scale of the dust problem has come as a shock. It appears that galaxies generate twice as much starlight as previously thought." The team made their discovery using data from the Millennium Galaxy Catalogue, a high-resolution catalogue of 10,000 galaxies assembled by Driver and his team using the Isaac Newton Telescope in the Canary Islands and others. They used this to test a new model for dust distribution in galaxies developed by scientists in the UK and Germany which allowed them to calculate precisely the fraction of starlight blocked by the dust. The key test that the new model passed was whether the energy of the absorbed starlight equated to that detected from the glowing dust. "The equation balanced perfectly," said Dr Cristina Popescu, of the University of Central Lancashire, who helped draw up the model. "For the first time we have a total understanding of the energy output of the Universe over a monumental wavelength range." The photo shows the spiral galaxy NGC891 edge on, revealing a dark lane of dust. Photo by Robert Gendler. You can see more great photos of galaxies here. • What do you think? Skymania welcomes your comments and views. You can support this site by visiting Skymania's stores in the USA, the UK, Canada and France. They are powered by Amazon so you can buy with confidence. ©PAUL SUTHERLAND, Skymania.com

Missing supernova is found at last

One of the biggest blasts in our galaxy went off without anyone spotting it because it was hidden behind a cloud of dust, astronomers revealed today. The explosion, a suicidal star called a supernova, was brighter than all the stars in the Milky Way combined and might normally have been visible in daylight. However, Victorian stargazers saw nothing of the blast around 150 years ago due to a dense region of obscuring dust and gas. Remnants of its expanding shell have finally been identified by UK scientist Dr Dave Green, of the University of Cambridge, with colleague Dr Stephen Reynolds of North Carolina State University. Experts had often remarked on the fact that no supernova had been recorded within our galaxy since the 17th Century, although they are regularly spotted going off in other galaxies deep in the universe. The two scientists compared an X-ray "photo" of the blast's remains taken using the Chandra satellite in 2007 with another image made with a group of US radio telescopes called the Very Large Array in 1985. They found the supernova remnant, called G1.9+0.3, had expanded at an unprecedented rate, growing in size by 15 per cent in just 23 years. Working backwards, they confirmed that the blast that created them must have happened about 150 years ago. This finding makes the supernova easily the youngest known in our Milky Way galaxy. Although its precise distance is not known, the astronomers believe it lies near the centre of the galaxy. Radio waves and Xrays are able to penetrate dense clouds of dust whereas light cannot. Dr Green said: "The discovery that G1.9+0.3 is so young is very exciting. It fits into a large gap in the known ages of supernova remnants, and since it is expanding so quickly, we will be able to follow its evolution over the coming years." Details of the discovery will appear in the journal Monthly Notices of the Royal Astronomical Society. Planets like our own are believed to form from dust left by supernova blasts. The closest supernova to us in recent years was seen to explode in 1987 in a satellite galaxy of the Milky Way called the Large Magellanic Cloud. It became easily visible with the naked eye and its debris was later pictured shining like a ring of pearls. Last month, astronomers identified clusters of other candidates for supernovae. • What do you think? Skymania welcomes your comments and views. You can support this site by visiting Skymania's stores in the USA, the UK, Canada and France. They are powered by Amazon so you can buy with confidence. ©PAUL SUTHERLAND, Skymania.com

Amateurs monitor storm on Saturn

Nasa scientists have acknowledged the value of amateur observations in supporting their exploration of Saturn. They are using studies by hobbyists to help keep track of a powerful thunderstorm that has been raging for five months on the ringed planet. The storm, thousands of miles wide, produces lightning bolts 10,000 times more powerful than those here on Earth. The spaceprobe Cassini, whose mission was extended last month, has been taking colour pictures of the storm, like those shown here. But when Cassini is on the other side of Saturn, the scientists have turned to modern CCD images - taken with exotic versions of the webcam - to keep up with developments. Georg Fischer, of the University of Iowa, has been studying electrostatic discharges from the storm which produce radio signals. He said: "Since Cassini's camera cannot track the storm every day, the amateur data are invaluable. I am in continuous contact with astronomers from around the world." The new storm, first detected on November 27 last year, is raging in Saturn's southern hemisphere, in a region that has been dubbed Storm Alley by mission scientists, following previous bad weather there. You can listen to a previous storm here. Fischer said: "The electrostatic radio outbursts have waxed and waned in intensity for five months now. We saw similar storms in 2004 and 2006 that each lasted for nearly a month, but this storm is longer-lived by far. And it appeared after nearly two years during which we did not detect any electrical storm activity from Saturn." Ulyana Dyudina, of the Cassini imaging team, said: "In order to see the storm, the imaging cameras have to be looking at the right place at the right time, and whenever our cameras see the storm, the radio outbursts are there." The scientists hope their studies will help them learn what causes the amazing storms. They have also been fascinated by a monster storm over Saturn's south pole. • What do you think? Skymania welcomes your comments and views. You can support this site by visiting Skymania's stores in the USA, the UK, Canada and France. They are powered by Amazon so you can buy with confidence. ©PAUL SUTHERLAND, Skymania.com

Hubble presents some smash hits

Pictures of the week must be Hubble's latest release which you could call a crash course in the phenomenon of colliding galaxies. The space telescope team have isssued a collection of 59 new colour images of these vast star cities running into each other to mark the 18th anniverary of Hubble's launch. They show a fascinating array of intricate structures as the galaxies interact, and tidal effects change the forms of their wisps and loops. Contrary to what one might imagine, galactic collisions do not result in enormous explosions. They are not like a cosmic car crash. The reason is the vast distance between the stars which means that they simply pass each other as they sail through space in different directions. The Hubble team note that interacting galaxies are found throughout the universe and can trigger bursts of star formation or even form new galaxies. Such mergers, which were more common in the early universe than today, are thought to be one of the main driving forces for cosmic evolution. They switch on quasars, spark frenetic star births and prompt explosive stellar deaths. Even apparently isolated galaxies will show signs in their internal structure that they have experienced one or more mergers in their past, say the astronomers. The merging galaxies captured in the released series of images are snapshots of different moments in the long interaction process. Our own Milky Way contains the debris of the many smaller galaxies it has encountered and devoured in the past, and it is currently absorbing the Sagittarius dwarf elliptical galaxy. In turn, it looks as if our Milky Way will be absorbed by its giant neighbour, the Andromeda galaxy. They are rushing towards each other at a staggering 500,000 km per hour - yet the collision will still not happen until around two billion years time, forming a new super galaxy which wags have dubbed Milkomeda. Picture: NASA, ESA and the Hubble Heritage Team. • What do you think? Skymania welcomes your comments and views. You can support this site by visiting Skymania's stores in the USA, the UK, Canada and France. They are powered by Amazon so you can buy with confidence. ©PAUL SUTHERLAND, Skymania.com

Nasa challenge boy, 13, on asteroid

Nasa has got caught up in an astonishing clash with a 13-year-old schoolboy over the threat of an asteroid impact, though they were reacting to some rather wild press reports rather than the lad's own dubious maths. The German student calculated that a 350-yard wide space rock called Apophis has a one-in-450 chance of colliding with the Earth in 2036, contradicting Nasa's own estimate that the odds are a low one-in-45,000. Nico Marquardt based his results on the possibility that the deadly asteroid could smash into satellites orbiting the Earth, deflecting its course, as it makes a previous close pass on Friday 13th of April, 2029. Apophis is expected to come inside the orbits of communications satellites such as those used by Sky TV. But Nasa say the chance of any collision is "exceedingly remote". In an unprecedented statement, Nasa's Jet Propulsion Laboratory in California said it "has not changed its current estimates for the very low probability (1 in 45,000) of an Earth impact by the asteroid Apophis in 2036." The space scientists added: "Contrary to recent press reports, NASA offices involved in near-Earth object research were not contacted and have had no correspondence with a young German student, who claims the Apophis impact probability is far higher than the current estimate. "This student's conclusion reportedly is based on the possibility of a collision with an artificial satellite during the asteroid's close approach in April 2029. However, the asteroid will not pass near the main belt of geosynchronous satellites in 2029, and the chance of a collision with a satellite is exceedingly remote. "Therefore, consideration of this satellite collision scenario does not affect the current impact probability estimate for Apophis, which remains at 1 in 45,000." The US-based Planetary Society has put up a $50,000 prize for whoever comes up with the best scheme to tackle the threat that Apophis poses. Last year, scientists revealed they had discovered the type of rock that makes up Apophis - a "know your enemy" finding that could help them deal with it. Picture: A Nasa artist's impression of an asteroid impact. • What do you think? Skymania welcomes your comments and views. You can support this site by visiting Skymania's stores in the USA, the UK, Canada and France. They are powered by Amazon so you can buy with confidence. ©PAUL SUTHERLAND, Skymania.com