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Wall of gas divides
cosmic metropolis

...A new study from the Chandra X-ray Observatory unveils the star-forming factory NGC 604 as a divided neighbourhood...

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Supermassive black holes not guilty of shutting down star formation

...Galaxies cease star formation long before their supermassive black holes have the power to do the job themselves...

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C1XS takes first taste of lunar X-rays

...The UK-built C1XS instrument flying aboard the Chandrayaan-1 orbiter has successfully detected its first X-ray signature from the Moon...

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STS-120 day 2 highlights

Flight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.

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STS-120 day 1 highlights

The highlights from shuttle Discovery's launch day are packaged into this movie.

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STS-118: Highlights

The STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.

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STS-120: Rollout to pad

Space shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.

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Dawn leaves Earth

NASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.

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Dawn: Launch preview

These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.

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Powerful new technique to measure asteroids

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 11 February, 2009

A team of French and Italian astronomers have devised a new method for measuring the size and shape of asteroids that are too small or too far away for traditional techniques, increasing the number of asteroids that can be measured by a factor of several hundred.

Artist's impression of asteroid (234) Barbara, which is best modelled as two bodies that may possibly be in contact. Image: ESO/L. Calcada.

Knowing the sizes and shapes of asteroids is vital for not only understanding the evolution of such bodies in the early Solar System, but for quantifying the size distribution of potentially hazardous asteroids.

"Knowledge of the sizes and shapes of asteroids is crucial to understanding how, in the early days of our Solar System, dust and pebbles collected together to form larger bodies and how collisions and re-accumulation have since modified them," says Marco Delbo from the Observatoire de la Cote d'Azur, France, who led the study.

Direct imaging, using ground- or space- based telescopes, or radar imaging, is the standard method of determining the properties of asteroids, but even with adaptive optics these techniques are usually limited to the largest objects or those that experience close counters with the Earth. Delbo and colleagues have devised a new method that uses interferometry to resolve asteroids as small as about 15 kilometres in diameter and located in the main asteroid belt 200 million kilometres away - the equivalent of being able to measure the size of a tennis ball from a distance of a thousand kilometres.

"This is equivalent to having vision as sharp as that of a telescope with a diameter equal to the separation between the two VLT Unit Telescopes used, in this case, 47 metres," says co-author Sebastiano Ligori, from INAF-Torino, Italy. The technique will add significantly to the inventory of near Earth objects, bringing small asteroids into the light for the first time. This is especially important as their physical characteristics may vary from well-studied larger objects.

The researchers demonstrated their technique by observing main belt asteroid (234) Barbara, which was revealed to have a rather peculiar shape. The best fit model suggests that it is composed of two bodies with diameters of 37 and 21 kilometres respectively, and separated by at least 24 kilometres.

"The two parts appear to overlap," says Delbo, "so the object could be shaped like a gigantic peanut or, it could be two separate bodies orbiting each other."

If Barbara proves to be a double asteroid, this is will allow further properties to be deduced, since by combining the diameter measurements with the parameters of the orbits, the asteroid's density can be computed. "Barbara is clearly a high priority target for further observations," concludes Ligori.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
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Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
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3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
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