Friday, March 23, 2007

The Magnetic Sun

This week, the recently launched "Hinode" satellite returned some stunning new photos and video of our Sun. Focusing near the edge of our star, the space telescope documents the turbulent boiling of the solar surface in exquisite detail. But look a little closer and you will notice that as the hot material flows away from the surface, it does not simply stream off in any direction. It follows the invisible lines of a pervasive and dynamic magnetic field.

Galileo was the first to point a telescope at the Sun, revealing the dark spots that litter the surface. We now know that these "sunspots" are areas where the magnetic field is stronger, inhibiting the boiling motion and keeping the surface cooler -- and thus darker -- than its surroundings. Each spot is enormous, typically the size of our entire planet. But sunspots are only the beginning of the story of our magnetic Sun.

If you watched the Sun closely over many years, and you counted the total number of sunspots regularly, you might notice an interesting pattern. Every 11 years, the Sun seems to show a few sunspots, then many more, and then fewer again. What's more, when there are only a few spots they seem to show up in two bands, about halfway between the Sun's equator and poles. Over the course of this 11 year "solar cycle" they increase in number, migrate toward equator, and gradually fade away.

As the decades go by, you would notice that some of the cycles are stronger than others -- generating far more sunspots during the peak. Best of all, you would undoubtedly notice the huge explosions on the Sun's surface that eject hot gas out into space, sometimes directly at the Earth. When there are many sunspots, these explosions are more frequent and more dangerous. They are powerful enough to threaten astronauts and orbiting satellites, disrupt our communications systems, and occasionally bring down electricity grids.

With this new eye in the sky, astronomers will study the underlying order in these patterns -- eventually helping us predict the explosions and protect ourselves from the boiling magnetic Sun.

Friday, March 9, 2007

Astronomer Surplus

This week, as part of my work with the American Astronomical Society's Committee on Employment, I've been digging up statistics on the relative rates of training and employment of young astronomers. As in many sciences, the production rate of new Ph.D. astronomers by universities is completely decoupled from the global demand for trained scientists. This has created a huge surplus of young astronomers -- there are now about 3 new Ph.D. recipients annually for every new tenure-track job in astronomy.

The job market has responded by creating more and more temporary (2-3 year) "postdoctoral" positions -- a sort of holding pattern for young scientists who are seeking an academic or research career. In the long term, there appears to be no easy solution to the problem, since the incentive of the university system is to use as many graduate students as possible for cheap skilled labor, without regard to their long-term job prospects. Essentially, overproduction appears to be built into the system -- making the mathematical formulation of surplus production of astronomers similar to that for industrial pollution models, an unintended side-effect of the production process.

What I found in the numbers surprised me. Although the current situation is clearly unsustainable, it was much worse a decade ago -- with nearly 7 times as many Ph.D. recipients in 1995 than new tenure-track jobs. While the number of new "permanent" positions steadily increased throughout the late-1990's, the number of new Ph.D. astronomers gradually declined. After the turn of the century, something else happened. The number of new astronomers being produced by the system leveled off, but new postdoctoral positions grew dramatically. With fewer graduate students around, all of those new university professors had to hire postdocs to get the work done.

Of course this only tells part of the story. There has also been recent growth in the number of non-tenure-track lecturer, research, and support positions. This is just one example of the larger cultural shift to temporary employment that is happening throughout society -- it is not unique to astronomy. It may not be in the best interests of science, but there it is.