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Andromeda’s once and future stars

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Two ESA observatories have combined forces to show the Andromeda Galaxy in a new light. Herschel sees rings of star formation in this, the most detailed image of the Andromeda Galaxy ever taken at infrared wavelengths, and XMM-Newton shows dying stars shining X-rays into space.

During Christmas 2010, ESA’s Herschel and XMM-Newton space observatories targeted the nearest large spiral galaxy M31. This is a galaxy similar to our own Milky Way – both contain several hundred billion stars. This is the most detailed far-infrared image of the Andromeda Galaxy ever taken and shows clearly that more stars are on their way.

Sensitive to far-infrared light, Herschel sees clouds of cool dust and gas where stars can form. Inside these clouds are many dusty cocoons containing forming stars, each star pulling itself together in a slow gravitational process that can last for hundreds of millions of years. Once a star reaches a high enough density, it will begin to shine at optical wavelengths. It will emerge from its birth cloud and become visible to ordinary telescopes.

Many galaxies are spiral in shape but Andromeda is interesting because it shows a large ring of dust about 75 000 [...]

X-ray evidence supports possible new class of supernova


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Evidence for a significant new class of supernova has been found with the European Space Agency’s XMM-Newton and NASA’s Chandra X-ray Observatory. These results strengthen the case for a population of stars that evolve rapidly and are destroyed by thermonuclear explosions. Such ‘prompt’ supernovas could be valuable tools for probing the early history of the cosmos.

A team of astronomers uncovered a puzzling situation when they examined X-ray data from DEM L238 and DEM L249, the remnants of two supernovas in a nearby galaxy. On the one hand, the unusually high concentration of iron atoms implied that the remnants are the products of thermonuclear explosions of white dwarf stars, a well-known type of supernova known as ‘Type Ia’. On the other hand, the hot gas in the remnants was much denser and brighter in X-rays than typical Type Ia remnants.

A white dwarf, the dense final stage in the evolution of a sun-like star, is a very stable object and will not explode on its own. However, if a white dwarf has a close companion star it can grow beyond a critical mass by pulling gas off the companion and explode.

Computer simulations of Type Ia supernova remnants [...]

Integral catches a new erupting black hole


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ESA’s gamma-ray observatory, Integral, has spotted a rare kind of gamma-ray outburst. The vast explosion of energy allowed astronomers to pinpoint a possible black hole in our Galaxy.

The outburst was discovered on 17 September 2006 by staff at the Integral Science Data Centre (ISDC), Versoix, Switzerland. Inside the ISDC, astronomers constantly monitor the data coming down from Integral because they know the sky at gamma-ray wavelengths can be a swiftly changing place.

“The galactic centre is one of the most exciting regions for gamma ray astronomy because there are so many potential gamma-ray sources,” says Roland Walter, an astronomer at the ISDC, and lead author of these results.

To reflect the importance of this region, Integral is now running a Key Programme, in which almost four weeks of its observing time is given over to the study of the galactic centre. This is allowing astronomers to understand the gamma-ray characteristics of the galactic centre and its celestial objects, better than ever before.

XMM-Newton’s image of X-ray nova IGR J17497-2821 It was during one of the first of these observations that astronomers saw the outburst take place. An unexpected event of this kind is known as a ‘target [...]

ESA’s XMM-Newton gains deep insights into the distant Universe


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Using XMM-Newton, astronomers have obtained the world’s deepest ‘wide screen’ X-ray image of the cosmos to date. Their observations show newly discovered clusters of galaxies and provide insights into the structure of the distant Universe…

Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies like our own which themselves congregate into clusters. These clusters are ‘strung’ throughout the Universe in a web-like structure. Astronomers have studied this large-scale structure of the nearby Universe but have lacked the instruments to extend the search to the large volumes of the distant Universe.

Thanks to its unrivalled sensitivity, in less than three hours, ESA’s X-ray observatory XMM-Newton can see back about 7000 million years to a cosmological era when the Universe was about half its present size, and clusters of galaxies more tightly packed. Marguerite Pierre, CEA Saclay, France, with a European and Chilean team, used this ability to search for remote clusters of galaxies and map out their distribution.

The work heralds a new era of studying the distant Universe. The optical identification of clusters shows only the galaxies themselves. However, X-rays show the gas in between [...]

Rapid heartbeat in Andromeda indicates a new kind of object


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There are many kinds of celestial objects in the Universe but we are far from knowing them all. XMM-Newton may have discovered a new one: a very luminous soft X-ray source that is pulsating extremely rapidly in the central region of the Andromeda galaxy. This unusual object could be a new kind of accreting white dwarf.

The spiral Andromeda galaxy (M31), only 2.5 million light years away, is in many respects similar to our own. Because it is inclined to our line-of-sight there is less intervening material in the way and thus the many hundreds of X-ray sources that it contains can easily be observed.

Previous X-ray missions, such as Einstein and ROSAT, and NASA’s Chandra observatory, which is currently operating, had together detected several hundred sources throughout the Andromeda galaxy. In two recent observations, XMM-Newton’s EPIC-pn and EPIC-MOS cameras detected most of the previously known sources in Andromeda’s central region, but also found 10 objects that have significantly brightened or dimmed between June and December 2000.

To find out more about these objects, and to read the rest of this article, go to the ESA Science site.

Unveiling the nature of a dusty galaxy


The ESA/NASA Hubble Space Telescope has made the first detailed optical observations of an example of a remarkable class of galaxies by using the additional magnifying power of a huge galaxy cluster to extend its range. The galaxy, named J1/J2, belongs to a remote population of galaxies. Although extremely luminous, the galaxies are obscured by enormous quantities of dust – the smoky residue of the life cycle of massive stars – and have so far only been seen by sub-millimetre telescopes. buy com domain . The Hubble observation has enabled astronomers to investigate the connection between this distant population of ‘hidden’ dust-enshrouded, intensely star-forming galaxies and the less dusty galaxies that are readily observed with optical telescopes.

Clusters of galaxies can act as a gravitational lens, magnifying and distorting the galaxies behind them and so are also known as ‘natural telescopes’. The well-known ‘gravitational arcs’ are a result of gravitational lensing by large clusters. Galaxy clusters can amplify the light from background objects by up to 100 times, but generally the magnification power is an order of magnitude less – comparable to that of a pair of binoculars.

A group of European and American astronomers led by Jean-Paul Kneib [...]