Bright, bold blazars intrigue astrophysicists
Nov. 16, 2010
Supermassive black holes churn in the centers of some galaxies near the universe’s edge. As disks of gas and dust spiral toward the point of no return, matter shoots out in opposite directions at nearly the speed of light, like steam from an angry cartoon character’s ears.
Sometimes, these jets happen to be pointed almost right toward Earth. In that case, these active galaxies are called blazars. Ohio University astrophysicist Markus Böttcher likes studying them because their energy is “so far beyond our experience on Earth. We have particles being accelerated to energies that are 100 million times more powerful than any accelerator on Earth can achieve.”
Markus Böttcher, associate professor of astrophysics.
Böttcher believes that studying blazars could help us understand galactic evolution. Since most, if not all, galaxies have supermassive black holes at their cores—including the Milky Way-active galaxies might represent one stage in the life cycle of all galaxies.
Blazars allow scientists to explore conditions near black holes and better understand how they convert matter into incredibly powerful jets.
When those jets point toward Earth, they provide the brightest sources of high-energy gamma rays in the sky. But they waver in brightness on timescales of months to hours, and astronomers don’t yet know why.
The answer may lie in the blazars’ magnetic ﬁelds, according to a recent paper published in the journal Nature by a worldwide team of astronomers that included Böttcher.
The team studied a blazar called 3C 279 in the constellation Virgo. They used telescopes on Earth and in space to observe the full spectrum of light, from radio waves to X rays and gamma rays.
“The brightness was shooting up and down,” says Böttcher, who observed 3C 279’s visible light with the MDM Observatory on Kitt Peak near Tucson, Arizona. The light was polarized and the research team saw that the direction “was swinging around. That was a very new ﬁnding,” adds Böttcher, who is continuing to do more analysis of the galaxy’s optical light.
Böttcher and his co-authors believe part of 3C 279’s magnetic ﬁeld is altered by shocks traveling through the jet. That could put “a little bit of kink” in the beam, producing the changes in polarization and brightness.
by Stephanie Dutchen
This article appears in the Autumn/Winter 2010 issue of Perspectives magazine.