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How the Milky Way Killed Off Its Satellites

October 18, 2011 Leave a comment

Two researchers from Observatoire Astronomique de Strasbourg have revealed for the first time the existence of a new signature of the birth of our galaxy’s first stars. More than 12 billion years ago, their intense light dispersed the gas of the Milky Way’s satellite galaxies. By computing the observable consequences of this process, Pierre Ocvirk and Dominique Aubert demonstrated their prevailing role. This result confirms that reionisation is indeed an essential process in the standard model of galaxy formation. The study took place within the LIDAU collaboration (Light In the Dark Ages of the Universe). It is published in the october issue of the letters of the Monthly Notices of the Royal Astronomical Society.

The first stars of the Universe appeared about 150 million years after the Big Bang. Back then, the hydrogen and helium gas filling the universe was cold enough to have its atoms be electrically neutral. As the intense light of the first stars propagated through this gas, it broke the hydrogen atoms, returning them to the plasma state they experienced in the first moments of the Universe. This process, known as reionisation, also results in significant heating, which can have dramatic consequences: the gas becomes so hot that it escapes the weak gravity of the lowest mass galaxies, thereby depriving them of the material needed to form stars. It is now widely admitted that this photo-evaporation process explains the small number and large ages of the stars seen in the dwarf galaxies satellites of the Milky Way. It also offers a credible solution to the missing satellites problem. On the other hand, their sensitivity to UV radiation means satellite galaxies are good probes of the reionisation epoch. Moreover, they are relatively nearby, from 30000 to 900000 light-years, which allows us to study them in great details, especially with the forthcoming generation of telescopes. In particular, the study of their stellar content with respect to their position could give us precious insight into the structure of the local UV radiation field during the reionisation epoch.

Full Story: http://astro.u-strasbg.fr/~ocvirk/PR1.html

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Astronomy & Geophysics Bring Women into Science

October 10, 2011 Leave a comment

Women are better represented in astronomy and solid-Earth geophysics research than in other areas of physics, according to a major study by the Royal Astronomical Society, with a summary published in the October edition of the journal Astronomy and Geophysics. The RAS Demographic Survey of Astronomy and Geophysics collected data on more than 2000 research employees and students in astronomy and solid-Earth geophysics in the UK to establish the composition of this community and better understand its work. Less encouragingly, the survey results show how these research areas are poor at recruiting people from black and minority ethnic (BME) groups and that addressing this deficit remains a significant challenge.

The last comparable exercise took place in 1998 and at that time covered a slightly smaller community. This time the RAS commissioned Sean McWhinnie of Oxford Research and Policy to carry out the work, gathering data using both online questionnaires and internet research of departmental websites. The survey was carried out in the autumn of 2010 and spring of 2011.

Full Story: http://www.ras.org.uk/news-and-press/217-news2011/2017-astronomy-and-geophysics-bring-women-into-science

From the Comfort of Home, Web Users May Have Found New Planets

September 22, 2011 Leave a comment

Since the online citizen science project Planet Hunters launched last December, 40,000 web users from around the world have been helping professional astronomers analyze the light from 150,000 stars in the hopes of discovering Earth-like planets orbiting around them.

Users analyze real scientific data collected by NASA’s Kepler mission, which has been searching for planets beyond our own solar system — called exoplanets — since its launch in March 2009.

Now astronomers at Yale University have announced the discovery of the first two potential exoplanets discovered by Planet Hunters users in a new study to be published in the Monthly Notices of the Royal Astronomical Society.

Full Story: http://opac.yale.edu/news/article.aspx?id=8898

How Single Stars Lost Their Companions

September 15, 2011 Leave a comment

Not all stars are loners. In our home galaxy, the Milky Way, about half of all stars have a companion and travel through space in a binary system. But explaining why some stars are in double or even triple systems while others are single has been something of a mystery. Now a team of astronomers from Bonn University and the Max-Planck-Institute for Radio astronomy (also in Bonn) think they have the answer – different stellar birth environments decide whether a star holds on to its companion. The scientists publish their results in a paper in the journal Monthly Notices of the Royal Astronomical Society.

Stars generally do not form in isolation but are born together in groups within clouds of gas and dust or nebulae. These stellar labour rooms produce binary star systems, which means that virtually all newborn stars have a companion. Most of these groups of stars disperse quickly so that their members become part of the Galaxy. But why, then, are not all stars seen in the sky binaries, but only half of them?

Full Story: http://www.ras.org.uk/news-and-press/217-news2011/2011-how-single-stars-lost-their-companions