28
Feb 10

New Star Forming Galaxies at approximatelly redshift z=7

Source: arXiv

The addition of Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) has led to a dramatic increase in our ability to study the z > 6 Universe. The increase in the near-infrared (NIR) sensitivity of WFC3 over previous instruments has enabled us to reach apparent magnitudes approaching 29 (AB).  This allows us to probe the rest-frame ultraviolet (UV) continuum, redshifted into the NIR at z >6.

In this research the authors study the rest-UV luminosity function, and hence estimate the integrated star formation rate within 800Myr after Big Bang. Understanding the global star formation history at these redshifts is crucial in answering the question whether the UV photons produced by the short-lived OB stars were sufficient to reionize the Universe.

The studied leads to the conclusion that some reionization of the the primordial Universe seems to have been possible.

This paper was submitted to MNRAS on February 25th, 2010. (read more)

Link:

Paper submitted to MNRAS

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28
Feb 10

How do small asteroids form and evolve?

Source: Universe Today


Itokawa, a dusty asteroid. Credit: JAXA.

Images sent back from space missions suggest that smaller asteroids are not pristine chunks of rock, but are instead covered in rubble that ranges in size from meter-sized boulders to flour-like dust. Indeed some asteroids appear to be up to 50% empty space, suggesting that they could be collections of rubble with no solid core.

But how do these asteroids form and evolve? And if we ever have to deflect one, to avoid the fate of the dinosaurs, how to do so without breaking it up, and making the danger far greater?

Johannes Diderik van der Waals (1837-1923), with a little help from Daniel Scheeres, Michael Swift, and colleagues, to the rescue. (Read more)

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