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The April 2010 issue of Astronomy Now, the UK's best-selling astronomy magazine, is now on sale at all good newsagents.



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The five-minute white dwarf waltz
...Utilising the resolving power of the ten-metre Keck telescope in Hawaii, astronomers from the University of Warwick and Radboud University in the Netherlands have confirmed the existence of a double white dwarf system where the two stars orbit one another every 5.4 minutes...
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Gamma-ray glow steeped in mystery
...An omnipresent fog of high energy gamma-ray radiation that bathes the entire Universe is being produced mostly by a mysterious, unknown source, revealed scientists this week at a meeting of the American Astronomical Society’s High-Energy Astrophysics Division...
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Lava likely made river-like channel on Mars
...Dried-up river channels on Mars are some of the best evidence that water once flowed on the surface of the red planet, but new analysis of a channel once thought to have been carved by water shows that it was in fact formed from lava...
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Sagittarius A* goes on diet
DR EMILY BALDWIN
ASTRONOMY NOW
Posted: 06 January 2010


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Scientists have long known that the supermassive black hole lurking in the belly of the Milky Way ingests very little matter, but previous estimates of a one percent consumption rate of fuel could be a significant overestimate.

This Chandra image of Sgr A* and the surrounding region is based on data from a series of observations lasting almost two weeks. The image is 15 arcminutes across. NASA/CXC/MIT/F.K. Baganoff et al.

The fuel for Sagittarius A* (or Sgr A* for short) is provided by local massive young stars but because these stars are located some distance from the hungry black hole where its gravity is significantly weaker, it struggles to capture and swallow the high-velocity stellar winds. Scientists had estimated that it feeds on about one percent of this stellar fuel, but a new model based on Chandra X-ray Observatory observations suggest it could be as little as one percent of that one percent.

The new model considers the flow of energy between an inner region near to the black hole's event horizon – the boundary beyond which even light cannot escape – and an outer region some million times further out that contains the young stars. Collisions between particles in the hot inner region transfer energy to particles in the cooler outer region, which in turn creates a pressure that makes most of the gas in the outer region flow away from the black hole.

The model appears to explain well the extended shape of hot gas detected around Sgr A* in X-rays as well as features seen in other wavelengths. Lobes of hot gas extending for 12 light years on either side of the black hole are seen in the new deep image taken by Chandra, and show evidence for powerful eruptions occurring several times over the last ten thousand years.

Mysterious X-ray filaments are also seen in the image, and may mark the locations where huge magnetic structures are interacting with streams of energetic electrons produced by rapidly spinning neutron stars – features known as pulsar wind nebulas.

2010 Yearbook
Our latest 132-page Astronomy Now special edition is an extravaganza of astronomy for the year ahead, with a complete 30-page guide to observing the planets, moon, meteor showers, two solar eclipses, and the deep sky in 2010.
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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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Infinity Rising
This special publication features the photography of British astro-imager Nik Szymanek and covers a range of photographic methods from basic to advanced. Beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and CCD imaging.
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Starry Night
Explore the Universe with these new versions of the award-winning Starry Night Software. Available now from the Astronomy Now Store.
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Exploring Mars
Astronomy Now is pleased to announce the publication of Exploring Mars. The very best images of Mars taken by orbiting spacecraft and NASA's Spirit and Opportunity rovers fill up the 98 glossy pages of this special edition!
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Mars rover poster
This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
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