... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . ... Risks Comparable to NEOs . ... The Increasing Rate of Discovery of Asteroids . ... Comet and Asteroid Collision Probabilities . ... Extreme albedo comets and the impact hazard (PDF Format) . ... Asteroid Impact Animations . ... Workshop on Scientific Requirements for Mitigation of Hazardous Comets and Asteroids - 2002 . ... The Spaceguard Survey Report, 1992 (PDF) . Tsunami from Asteroid/Comet Impacts . ...

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... 2006 June 3 . Gamma-Ray Earth . ... The Earth's gamma-ray glow is indeed very faint, and this image was constructed by combining data from seven years of exposure during the life of the Compton Gamma Ray Observatory , operating in Earth orbit from 1991 to 2000. ... Astronomers need to understand Earth's gamma-ray glow well as it can interfere with observations of cosmic gamma-ray sources like pulsars, supernova remnants , and distant active galaxies powered by supermassive black holes . ...

... Credit: Dirk Petry ( GLAST Science Support Center), EUD , EGRET , NASA Explanation: The pixelated planet above is actually our own planet Earth seen in gamma rays - the most energetic form of light. ... The Earth's gamma-ray glow is indeed very faint, and this image was constructed by combining data from seven years of exposure during the life of the Compton Gamma Ray Observatory , operating in Earth orbit from 1991 to 2000. ... 1999 2000 . ... Publications with keywords: gamma ray - Earth - CGRO . ...

... Before the modern era of technological astronomy, to know anything about the Universe beyond our planet we relied on light. ... Historically the two rival ideas were that light was either a stream of tiny bullet-like particles or a wave wobbling its way through space. ... The light we see (visible light which is not the tautology it sounds) is only part of the electromagnetic spectrum, a great sweep of radiations which also includes radio, infra-red, ultra-violet, x-rays and gamma rays. ...

... Our Sun is part of a huge wheel-shaped collection of stars. ... Astronomers have long suspected it was a very massive black hole, and that every galaxy had such a central mass, created early in the history of the universe. ... However, unless that object happens to be headed directly at the black hole (a relatively small target) it will just swing around and fly away again, like a comet making a pass at the Sun. The velocity acquired in falling towards the black hole also helps it escape. ...

... General information . ... Staff . Research staff . ... Information . ... Historical highlights . Historical research . ... This process is thought to occur in circumstellar disks of gas and dust around young stars on rather short timescales : infrared surveys show that the number of low mass stars with disks drops dramatically for stars older than 10 Myr, suggesting that in order to form large solids before the disk disperses, the growth process has to take place within a few million years. ...

Star formation is often best manifested by bright H II regions.These are regions of hydrogen which have been ionized by ultraviolet photons which are emitted from massive stars (typically stars more than 20 times the mass of the Sun). ... A narrowband filter image centered on this wavelength will then readily reveal these H II regions and hence the current sites of star formation in a galaxy, The luminous blobs that can be seen here are all H II regions . ... NGC 3558 Visual . NGC 3558 Infrared . ...

... Centaurus A : 15,000,000 light years away, in the constellation Centaurus, the closest AG to Earth . ... Astronomers think that the reason for the unusual shape of this galaxy is because hundreds of millions of years ago two galaxies, one dusty spiral and one bright ellipictal, collided causing a massive black hole in the middle and bright emmision of light. ... Andromeda galaxy: 2.8 million light years away, closest spiral galaxy to earth, farthest object one can see without a telescope. ...

... Supernova showered Earth with radioactive debris . ... The Real Reality Show: Would aliens be anything like us? ... Do other planets have meteor showers like Earth has? ... If so, can we learn anything about the planet's atmosphere by looking at the light as meteors burn? ... RELATED TOPICS: METEOR SHOWER . All planets in our solar system that have atmospheres also have meteor showers. ... Get instant access to subscriber content on Astronomy.com! ...

... Special Reports Giant space cloud may be powered by black holes 17:57 23 April 2007 NewScientist.com news service David Shiga An enormous cloud of roiling plasma in space may be drawing its energy from black holes, new observations suggest. Such clouds might be sources for the mysterious particles that occasionally crash into Earth's atmosphere at ultra - high speed. ... But higher energy particles in the cloud may be able to escape, he says. ...