http://www.skyandtelescope.com.au 31POLAR VORTEX: NASA’S GODDARD SPACE FLIGHT CENTER SCIENTIFIC VISUALIZATION STUDIO
between the balloon and the science payload, sending the
telescope into free fall. After a few seconds, the parachute
rapidly spreads out to slow the telescope’s descent. When
the instrument eventually reaches the ground, its speed is a
relatively gentle 7 metres per second. These days, NASA has
the parachute release automatically upon landing, but back
in 2006 the engineers had to send a second radio signal to
separate the parachute from the balloon once it had landed.
But for BLAST, sitting on the Antarctic plateau after
landing, this second signal didn’t get through.
Antarctica is known for extremely high winds — indeed,
adventurers attempting to cross the continent on skis often
bring wind sails. BLAST’s parachute acted like a giant sail. A
plane sent to find BLAST saw the 2,000-kg telescope being
dragged across the Antarctic plateau, leaving a scarred trail
of ice peppered with occasional debris where pieces of the
experiment had been ripped off.
After the wind had dragged BLAST almost 200 km,
what was left of the instrument entered a crevasse field. It
lodged in one of these chasms, where it remains stuck and
inaccessible to this day.
But luck was on the researchers’ side. The vessel
containing BLAST’s hard drives — which held all the science
data — was torn off the telescope a few kilometres before it
entered the crevasse field. Mountaineers from the National
Science Foundation Polar Program skied in to recover the
drives and return them to the grateful science team.BLAST comes back
Even though the original BLAST telescope was destroyed, the
far-infrared maps it made of hundreds of star-forming regions
were groundbreaking. BLAST charted young, cold clouds of
gas and dust crisscrossed by long filamentary structures,
wherein stars may be starting to form. In addition, it spotted
young star clusters emitting so much radiation that they are
destroying their parent cloud.
BLAST also made much deeper images of the distantuniverse, mapping small patches of sky that contained so
many sources, the individual galaxies blended together. In
this case, the three BLAST bands were used to assess the
galaxies’ apparent dust temperatures and thereby their
redshift. Younger galaxies in the early universe appear
redder and cooler because of their higher redshift, while
older, nearby galaxies appear somewhat more blue and
warm because of their lower redshift. Combining the BLAST
maps with other infrared data that probes the light from
young stars directly, BLAST found that star formation
in the universe peaked about 10 billion years ago. These
observations have since been confirmed and extended by
many studies from the ground and space.
More recently, we rebuilt the BLAST telescope as BLAST-Pol
(‘Pol’ for polarisation), mainly using pieces of the original
telescope that fell off as it was dragged along the Antarctic
plateau. This time, we added special optics that enabled
BLAST to detect not only the brightness of the glowing dust
but also the light’s polarisation.
This extra information gives us a measure of the light
waves’ orientation. In most cases, light waves are orientated
randomly, cancelling out any polarisation; however, spinningSPOLAR VORTEX During the Antarctic summer, high-altitude winds
carry balloons on longer flights of a week or more. The Cosmic Ray
Energetics And Mass (CREAM) project flew for 42 days in a single flight.
Its three orbits about the polar vortex are shown here.