Archive for January, 2009

Muons reveal upper atmosphere’s temperature

Published in Physics World, 23 Jan 2009

Scientists interested in the upper atmosphere should turn their attention to measurements made deep underground — says an international team of physicists who have noticed that the number of cosmic-ray remnants hitting Earth is linked to freak warming events in the upper atmosphere. The link implies that measurements of cosmic rays — both future and past — could help scientists improve climate and weather forecast models.

Cosmic rays are mostly high-energy protons and are constantly bombarding atoms in Earth’s atmosphere to create pions. These pions either decay into lighter muons or continue to interact with nearby atoms and avoid decaying into muons. If the atmosphere is cool and thick then the chance of continued interactions is much higher, and the number of muons generated is therefore far fewer than when the atmosphere is warmer. [...]

The rest of this article is available here.

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Sand pushes Martian rocks into place

Published in Physics World, 13 Jan 2009

Can you spot the pattern in this photo of Martian rocks? If not, then don’t feel bad: according to researchers in the US and Canada the very lack of a pattern means that there must be some mechanism driving the rocks that way. Studying this process, in which built-up sand levers rocks away from one another, could help geophysicists to understand how climate has steadily transformed the surface of the red planet.

“Rather than look at patterns on the Martian surface, we were looking at a pronounced absence of any patterns at some sites,” Andrew Leier of the University of Calgary, Canada, told physicsworld.com. “We had noticed similar features in desert settings on Earth and tried to understand how this distribution came about.” [...]

The rest of this article is available here.

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Stars born into Milky Way’s violent centre

Published in Physics World, 7 Jan 2009

Star formation is a steady process, requiring vast clouds of cold gas to gradually accumulate and compact. So in the region around the supermassive black hole at the centre of our galaxy, which is awash with violent gravitational “tidal” forces, one would expect stars to be few and far between.

Over the years, however, many stars have been spotted near the galactic centre — which raises the question: were the stars able to survive a perilous birth, or did they somehow migrate inwards from elsewhere?

Now, a group of astronomers from the Harvard–Smithsonian Center for Astrophysics, US, and the Max Planck Institute for Radio Astronomy, Germany, has evidence that stars can indeed be born near the galactic centre. Using the Very Large Array of radio telescopes in New Mexico, they have discovered two baby stars, or “protostars”, just a few light-years from the Milky Way’s black hole. [...]

The rest of the article is available here.

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