[Music throughout] A coronagraph is
a way to see distant planets hidden by the glare of the star they orbit.
The coronagraph reduces the light coming directly from the star to separate it from
the light reflected by the planet. WFIRST
doesn’t block the star’s light with an opaque disk as a simple coronagraph might.
Instead, it uses a combination of disks with complex
patterns and light-blocking stops to create destructive interference
with the star’s light, effectively making it disappear,
while allowing the light from planets to pass through.
A complicating factor is that the light picks up small distortions as it reflects off the
telescope’s series of mirrors, and these distortions can reduce the effectiveness
of the destructive interference. Collecting more light
increases the image signal, but the planets are still hidden under blobs of leftover
distorted starlight. To remove these blobs, the
coronagraph has special deformable mirrors that can change shape by using
hundreds of tiny pistons. This corrects distortions in the light beam.
As the mirrors deform, the blobs of light slowly begin to
disappear, revealing brighter planets. Further adjustment
brings fainter planets into view. Advanced software
processes this data, further improving the contrast and clarity of the
image. This processing makes objects more than a billion times
fainter than the star visible. As a result,
WFIRST will provide the first look at individual planets in star systems
that might be similar to our own.
[Explore: Solar system & beyond]
[NASA]