The full set of rings, imaged as Saturn eclipsed the Sun from the vantage of the Cassini spacecraft. Earth is visible as a “pale blue dot” at about the 4 o’clock position. From http://en.wikipedia.org/wiki/Rings_of_Saturn.
For our inaugural journal club at BSU physics, we discussed a very interesting paper led by Prof. Matt Hedman, now at University of Idaho Physics.
Hedman and Nicholson studied subtle density perturbations in Saturn’s ring system. If you look at images of the rings, you’ll see lots of patterns, many of which are caused by gravitational interactions with Saturn’s many satellites — the inner edge of the Cassini division, for example, is sculpted by gravitational tugs from Mimas.
However, the ring patterns studied by Hedman and Nicholson seem to result from gravitational perturbations with periods much shorter than the orbital periods of any Saturnian satellite, meaning the satellites aren’t the cause.
The periods actually correspond to those expected for oscillations within Saturn itself. Just like stars exhibit oscillations, Saturn oscillates, producing periodic variations in its gravitational field. And, as for stars, the periods of these oscillations depend on its interior. So by studying these subtle ring patterns, Hedman can tease out information about Saturn’s internal structure.
Hedman has coined the term “Kronoseismology” for this new approach to studying Saturn’s interior, analogous to “asteroseismology” for stars and “seismology” for the Earth. And just like those fields, Kronoseismology promises to lead to profound new insights about the second biggest planet in our solar system.
The density of Bose-Einstein condensates, exhibiting interference of their quantum mechanical wave functions. From https://sites.google.com/site/bigelowcatgroup/bec.
BSU’s Materials Science and Engineering Dept had a guest today from the University of Rochester, Prof. Nick Bigelow. Prof. Bigelow spoke this afternoon in the physics department about his experiments producing Bose-Einstein condensates in his optics lab. He did a great job of explaining their subtle physics at a level that our undergrads and even our lowly astronomers could understand.
In his lab, he uses lasers to cool small pockets of low-density rubidium gas to a Bose-Einstein condensation state and then spins up a torus of the gas with variously polarized laser beams. The quantum mechanical wave function describing the gas torus must then have an integer number of oscillations over its circumference.
By putting the spinning torus of gas into contact with other Bose-Einstein condensates with known wave functions (either spinning or not), Bigelow’s group can demonstrate the effects of interference between the quantum mechanical wave functions for the two condensates. The figure at top left shows the clouds of gas that form, exhibiting graceful density enhancements (warmer colors) that result from interference of the wavefunctions.
As lucid and compelling as Bigelow’s talk was, it highlighted again for me how strange and counter-intuitive quantum mechanical systems are. It reminded me of Richard Feynman‘s famous quote, “If you think you understand quantum mechanics, you don’t understand quantum mechanics” (which, I just learned, is not a Feynman quote at all, but a paraphrase of a Bohr quote).