Atom & Cosmos

Saturn storm’s aftermath
Planetary scientists have for the first time documented in detail the effects of a Saturnian storm on the planet’s atmosphere. Combining data from satellites and ground-based telescopes, an international team of researchers found that within a month of the onset of a storm last December, the disturbance had penetrated hundreds of kilometers into Saturn’s stratosphere, altering temperature, winds and composition over an entire hemisphere. The storm also created brilliant beacons of infrared light and generated a new, cold vortex in the middle of the disturbance, the team reports online May 19 in Science. —Ron Cowen

 

Atmospheric smash
A once-a-decade cosmic collision was heard halfway around the world, scientists have found. In October 2009 a small asteroid entered the atmosphere over Indonesia and disintegrated spectacularly. Scientists detected the sound waves that the fireball sent reverberating through the atmosphere as far away as Bolivia, say Elizabeth Silber of the University of Western Ontario and her colleagues. The blast was one of the most energetic ever recorded, the researchers report in a paper to appear in an upcoming Geophysical Research Letters. —Alexandra Witze

 

Hole-y halted star formation
Astronomers have found direct evidence that galaxy mergers, although initially triggering strong star formation and black hole growth, ultimately bring both processes to a halt. The findings are based on some of the first observations of molecular gas — the raw material for making stars — rushing out of the centers of several galaxies. Most of the galaxies house black holes and had been involved in violent mergers. The outflows, powered by stellar winds or radiation associated with the black holes, are strong enough to expel the gas in an astronomically brief 100 million years or less, stopping star formation, an international team reports in the May 20 Astrophysical Journal Letters. —Ron Cowen

 

Bathtubs and black holes
Watching water drain from a bathtub is a lot safer than watching photons orbit just outside a rotating black hole, but the result could be just as instructive. A new mathematical analysis details how sounds waves that orbit within the draining fluid — either in the direction of the fluid’s rotation or against it — resemble the paths of photons circling a spinning black hole. Scientists first suggested three decades ago that water going down a drain might be a good analog for a spinning black hole (SN: 12/18/10, p. 28), but the new study strengthens the model’s validity, an international team of researchers reports in an article posted at arXiv.org on May 10. —Ron Cowen 

 

Investigating Iapetus
One long-ago wallop may explain two current puzzles about Saturn’s moon Iapetus: its slow rotation and equatorial ridge. Planetary scientists suggest that early in the moon’s history, Iapetus was struck by another body. Some of the debris kicked up by the impact formed a ring around Iapetus while debris further out formed a small satellite. The satellite rapidly pushed the ring onto the surface of Iapetus, forming the ridge. And as the satellite migrated outwards, its gravitational interactions with Iapetus slowed the moon’s spin. Hal Levison and his colleagues at the Southwest Research Institute in Boulder, Colo., describe their simulation in an upcoming Icarus. —Ron Cowen