The Problem of Exascale Computing

The Problem of Exascale Computing

Computational physicists are already looking to the next milestone on the horizon: exascale computing, or supercomputers whose performance peaks in the exaflop range. But we need to get a lot better at parallelization before we can successfully compute at the exascale level.

Stuff Hitting Jupiter: A Retrospective

Fact: Jupiter is the best planet. What’s not to like? Big, beautifully stripey, four exciting moons, hurricane three times the size of the Earth, lots of fascinating hydrodynamics…I could go on. But Jupiter isn’t just awesome on its own. It was also the site of the first observed extraterrestrial impact event, and is routinely struck by asteroids and comets. Last week on Monday the 10th another piece of cosmic debris impacted the planet, producing a brief fireball spotted by amateur astronomers and providing an excellent opportunity to reflect on the history of impacts in Jupiter and the solar system at large.Jupiter has 67 known satellites, but only 8 are considered regular, i.e. they have stable, prograde, roughly circular, roughly planar orbits. The rest of the satellites are irregular and are likely captures. Jupiter’s mass means that it scoops up nearly everything that passes near it. The area of gravitational influence around a body orbiting another, much larger body is called the Hill sphere. Within the Hill sphere a satellite can be considered to orbit the smaller object (the planet) rather than the central one (the Sun). The Earth has a Hill sphere radius of about 1.5 million km, or 1% of the distance between it and the Sun. Jupiter, on the other hand, has a Hill sphere radius of about 53 million km – 0.355 AU, or nearly 7% of the distance between it and the Sun. This radius is well away from the bulk of the main asteroid belt, but close enough to pick up strays – and anything foolish enough to come close to the giant planet.In 1993 astronomers Carolyn and Eugene Shoemaker...