Some Data about Data

by | Nov 17, 2011 | Daily Paper Summaries

I’m sure you’ve heard the expression “5 hours in the library can save 5 months in the lab.” It’s true. Productive scientists are aware of what other scientists have done before them, that way they may “stand on the shoulders of giants” so that they might see farther. Linking datasets to papers improves the usability of previously published research and is one major way to increase the overall productivity of the scientific field.

Jupiter: Friend or Foe?

Jupiter: Friend or Foe?

by | Nov 16, 2011 | Daily Paper Summaries

Paper title: Jupiter: Friend or Foe IV: The Influence of Orbital Eccentricity and Inclination (arXiv:1111.3144) Authors: J. Horner, B. W. Jones  First Author’s Affiliation: University of New South Wales, Sydney, Australia MotivationThe hunt is on to find habitable exo-Earths, but what does “habitable” actually mean? The traditional definition of habitability focuses on the surface temperature of the planet: specifically, is it in the correct range to support liquid water? However, there are many other components to habitability. For example, if the star is too active and the planet too close to it, stellar activity and radiation may create a hostile environment for life to form. Another constraint on habitability comes from meteorite impacts: if the planet is hit by the equivalent of a Yucatan impactor (i.e. the one that killed the dinosaurs) every few millenia, it will be challenging for complex life to evolve there!In this paper, Horner and Jones focus on the impactor constraint for habitability. The existence of Jupiter is often cited as a factor in Earth’s habitability because the larger planet gravitationally shields Earth from most asteroid and cometary impacts. However, Jupiter is on a very sedate, low-eccentricity, low-inclination orbit, and the search for exoplanets has turned up gas giants with a wide range of inclinations and eccentricities. How would varying the eccentricity and inclination of Jupiter affect the impact rate on Earth? This is the question this paper asks. By understanding the influence of co-systemic giant planet eccentricity and inclination on the rate of impacts onto potentially habitable planets, it will be possible to more tightly focus the search for habitable exoplanets on systems that...
Were the First Stars Actually Hypermassive?

Were the First Stars Actually Hypermassive?

by | Nov 13, 2011 | Daily Paper Summaries

Paper title: Protostellar Feedback Halts the Growth of the First Stars in the Universe Authors: Takashi Hosokawa, Kazuyuki Omukai, Naoki Yoshida, Harold W. Yorke Author’s Affiliation: Jet Propulsion Laboratory; Department of Physics, Kyoto UniversityThe problem of understanding the formation and evolution of the first to form stars in the universe lies at the intersection of many fields of astrophysics. Since the first stars could only have formed once their host dark matter halos had begun to collapse, one must understand the formation of these stars in a cosmological context, tracking gas from extremely low intergalactic densities (~10-27 g cm-3), to extremely high, stellar densities (~1 g cm-3). Since all the metal content of the universe had not yet been synthesized in the cores of stars, the gas that collapsed to form the first stars would have been metal-free and thus possessed very different thermal properties compared to the interstellar and intergalactic gas in the local universe that can cool via metal line emission.Many studies of first star formation have focused on the cosmological piece of the puzzle: starting with a simulation of cold dark matter and gas in a ΛCDM cosmology, they look for the first ~106 solar mass dark matter halo to collapse, and then follow the collapse of first the dark matter and then the gas to very high densities. Due to the extremely large dynamic range in these simulations, it becomes prohobitively expensive to reach stellar densities and impossible to directly model the evolution of the first star. For reference, a recent simulation of the formation of the first stars followed the collapse to densities just above 10-8 g cm-3, far below typical stellar...