High-energy astrophysics meeting: Future articles and the “Fermi bubbles”

Posted by Liz Kruesi
on Thursday, April 11, 2013

Sitting in all these science talks and speaking with the researchers at the meeting of the High Energy Astrophysics Division of the American Astronomical Society is giving me some great ideas for future articles. High-energy astrophysics is a field that doesn’t always get a lot of media (and public) attention. I can certainly understand the reason: It’s difficult stuff and doesn’t always seem as accessible to people as extrasolar planets and solar system science — mostly because our eyes can’t see X-rays, gamma rays, neutrinos, and cosmic rays. But the field involves black holes and other extreme objects/events in the universe, which are fascinating subjects. Plus, they push the understanding of physics because they probe energies that can’t be created on Earth.

Astronomers spotted two huge structures, each extending about 25,000 light-years into the galaxy, emanating form the Milky Way’s center. This was one of the first images released in 2010 to show these bubbles. A new analysis of 4.5 years of Fermi Gamma-ray Space Telescope data suggests gamma-ray jets might be embedded in the data. // photo by NASA/DOE/Fermi LAT/D. Finkbeiner, et al.
Aside from article ideas and learning about possible future missions, I attended another interesting talk about the huge structures seen to emanate from the center of our Milky Way. Scientists call them the “Fermi bubbles” because they were discovered with the Fermi Gamma-ray Space Telescope. Astronomers have spied these 25,000 light-year-long bubbles in radio and microwave radiation as well. During a plenary talk yesterday, Doug Finkbeiner of Harvard showed how Fermi’s 4.5-year data display even sharper details of the bubbles compared to the 1.5-year observations when he and colleagues first discovered them.

Scientists aren’t sure what causes these bubbles, and they propose a number of ideas, including past bursts of star formation or a recently active central supermassive black hole. They know some type of large energetic event must be the cause because the bubbles have sharp edges.

In a paper published June 4, 2012, in The Astrophysical Journal, Finkbeiner and Meng Su argued for the presence of gamma-ray jets coming from our galaxy’s center. They analyzed three years of Fermi data for that paper. A new analysis shows a stronger signal on the east (left) side of the south bubble, which would be a “cocoon” holding the southern jet. And I admit, it does look suspicious — it certainly is a strong signal. (However, there’s a lot of data-processing involved, so this apparent jet and cocoon might just be something odd in the processing and might not actually exist.) This research is definitely a topic to continue following! 

Chair Joel Bregman (center) and Secretary Randall Smith (right) of the High Energy Astrophysics Division of the American Astronomical Society presented me with the 2013 David N. Schramm science journalism award. // photo courtesy Liz Kruesi
After the last science session of the day and checking out a few more posters, I headed to the banquet. In addition to receiving my award — a very exciting honor — I was lucky enough to sit with some of the scientists who really helped the field of high-energy astrophysics get started decades ago, such as Hale Bradt of MIT and Jeffrey McClintock of Harvard. It made for wonderful conversation.

Tomorrow is the last day of the meeting, but I’ll miss it because I need to head back to cold and rainy Wisconsin. It’s been a great few days of immersing myself in high-energy astrophysics, and you can expect to read more about the research in upcoming issues of Astronomy.

Read about some of the other talks at the meeting in my blog from yesterday.

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