by Maria Drout | Aug 24, 2011 | Daily Paper Summaries
Three-dimensional Hydrodynamic Core-Collapse Supernova Simulations for a 11.2 M⊙ Star with Spectral Neutrino Transport Tomoya Takiwaki, Kei Kotake, Yudai Suwa First author’s institution: Center for Computational Astrophysics, National Astronomical Observatory of Japan Core-collapse supernovae are some of the most energetic explosions in the universe and astronomers have devoted an incredible amount of both brain power and computational power to unraveling this astrophysical phenomenon. Despite this fact, the problem is far from solved.The ‘standard model’ for these explosions begins when a star with an initial mass greater than ~8 solar masses has progressed through a series of nuclear fusion processes in its core, culminating in the burning of silicon into iron-56. At this stage, fusion can proceed no further and the outward pressure supplied by the energy produced during nuclear burning ceases. If the overlying star is massive enough, the core will be unable to support itself and begins to collapse. In this high energy environment photodisintegration (effectively the reverse of nuclear fusion) and electron capture convert the iron core into free neutrons. When the core reaches approximately nuclear density, pressure exerted by the strong nuclear force and neutron degeneracy cause the collapse to halt. The remaining infalling matter then “bounces” off the proto-neutron star, causing an outward propagating shock wave.Ok, now hang with me. This is where it starts to get complicated… Simulations indicate that this initial shock is NOT what causes the supernova explosions we observe. Rather, additional photodisintegration and neutrino release cause the wave to lose energy and halt after less than a second. This produces a “standing shock” approximately 150 km from the proto-neutron star. In order...
by Elisabeth Newton | Aug 17, 2011 | Daily Paper Summaries
If there’s one type of star you’d think astronomers would know a lot about, it’s probably solar-type stars. After all, humans have been staring at our very near neighbor for millennia and in the recent century have dedicated entire space missions to studying this archetype. But there is always more to be learned and new tools like asteroseismology continue to open up avenues of study previously closed.
by Nathan Goldbaum | Aug 14, 2011 | Daily Paper Summaries
In this paper, the author proposes that the departure from this simple scaling with mass arises because of a simple fact: the natal molecular cloud must first fragment into clumps, which must in turn fragment into stars.
by Courtney Dressing | Aug 3, 2011 | Daily Paper Summaries
McLean et al. observe a new sample of late-M and L dwarfs with the Very large Array to search for a relation between rotation rate and radio activity for ultracool dwarfs.
by Courtney Dressing | Jul 6, 2011 | Daily Paper Summaries
What happens when redshifted quasars masquerade as stars? How do astronomers isolate them from the stellar population?
by Katherine Rosenfeld | Jun 29, 2011 | Daily Paper Summaries
Corroboration and confirmation is the name of this game. Making the same measurement twice — using a different technique — is a powerful way not only to confirm the initial result, but also the method used. This paper confirms a recent detection of a binary system using light-travel time techniques.
