Astronomy from the Stratosphere

Studying magnetic fields, star formation, and interstellar dust from a stratospheric balloon platform.


© Laura Fissel 2016

BLASTPol 500 micron map of the Vela C Molecular cloud, with magnetic field orientation overlaid.

Our galaxy is threaded with magnetic field lines. These magnetic field lines couple to the partially ionized gas that lies between the stars and can thereby affect the motion of the gas in our galaxy. These magnetic fields can play an important role in the direction of gas into forming dense molecular clouds, where the next generations of stars may form. If the magnetic fields in these clouds are sufficiently strong they can also inhibit or slow down star formation, by preventing the collapse of dense gravitationally unstable cloud sub-structures in the direction perpendicular to the magnetic field lines.

© Steven Benton 2016

BLASTPol and the BLASTPol Antarctic crew a few weeks before our launch in December 2012. (Photo credit: Steve Benton).

For my PhD work, I helped build a special telescope called BLASTPol (the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry), seen in the picture on the left. BLASTPol was designed to map out magnetic fields in nearby star forming regions, by measuring the glow from cold dust grains in these regions. These dust grains tend to align with the magnetic field, and we can measure the alignment and therefore the magnetic field direction by looking at the polarization of the glow they emit. The dust is extremely cold (about -260 degrees Celsius!), so the glow from the dust is extremely red: what we call far-infrared or microwave radiation.

However the Earth’s atmosphere actually absorbs most of the light in these colours before it makes its way down to telescopes at ground level. This is why we designed BLASTPol to operate from a balloon where it is above almost all of the atmosphere. We launched BLASTPol from Antarctica twice: once in December 2010 and once in December 2012. (See this site run by Steve Benton at Princeton for more pictures of our ballooning adventures).

© Laura Fissel 2016

BLASTPol a few minutes after launch on December 26th 2012. Most of what you see is the balloon, and the flight train (including our crucial red parachute). The telescope is the little speck at the very end. (Photo credit: Steve Benton)

After the 2012-2013 BLASTPol flight I moved to Northwestern University as a CIERA Postdoctoral Fellow. There I worked on software to convert the raw data from BLASTPol into calibrated science maps, including the map of the Vela C star forming region shown above. This map contains over 1,200 independent detections of magnetic field orientation, making it the most detailed magnetic field map ever made of a high mass star forming region! In a 2016 paper on the Vela C 500 micron map, I showed that regions where we see sharp changes in the magnetic field direction (measured over 0.5 parsec scales) generally do not tend to occur at the locations of dense cloud substructures.

I am also an active member of a team building a Next-Generation BLAST Polarimeter (BLAST-TNG). BLAST-TNG observes the same colour bands as BLASTPol, but has a larger primary mirror (we expect a best resolution six times that of BLASTPol), and new MKIDs detector arrays, such that BLAST-TNG should be able map the same area covered by BLASTPol in a tenth of the time. With this new telescope we will be able to map dozens of molecular clouds, make detailed comparisons of our observations of magnetic fields with computer simulations of star formation, and learn more about the strength of magnetic fields in star forming regions and how they influence the formation of stars and planets. For more information about BLAST-TNG please see our new website.