Astronomers and planet-hunters are constantly faced with a conundrum. Planets are typically found close to their central star, but often they are too close to the star to be seen. The light from their star engulfs them and makes it impossible to see them using a telescope. Astronomers often have to indirectly detect the existance of extrasolar planets, but we can never be sure that the calculations are accurate if we can't directly observe them. Fortunately, some bright minds have been pondering over the problem and have come up with a solution.
The new piece of kit being tested for this purpose is called the "vector-Apodizing Phase Plate" (vector-APP). It cancels out some of the starlight from a star, giving the planet's light a chance to shine. Half of the star is dimmed and photographed first, then the same happens to the other half. The resulting shadow is a semicircle, or a D-shape. The two images of the star are then carefully scrutinized by scientists in search of planets.
The way that this shadow is achieved is very complex: the pattern used to darken a D-shape on the screen requires liquid crystal 3D patterning techniques. When the liquid crystal is layered, it blocks out different wavelengths of light so scientists can look at the star and its secret planets in many wavelengths, including infrared that produces favorable contrast between star and planet.
On May 6th, 2015, a momentous thing happened. The vector-APP was switched on, and it worked! (Many scientists will be green with envy as it is rare to try an experiment and have it just work).
Jared Males is excited about the opportunities of the vector-APP. He commented that "with this new coronagraph we are now looking for planets around nearby stars. We have the capacity to directly detect, or rule out, planets smaller than Jupiter."
Matthew Kenworthy concluded "This new coronagraph technology is also excellent news for the extremely large telescopes currently under construction. Thermal infrared instruments such as the Mid-infrared E-ELT Imager and Spectrograph (METIS) can exploit this new technology and discover new worlds. With a vector-APP coronagraph in the next generation of telescopes, we can search for planets around nearby stars with unprecedented sensitivity."
This is a double image of the star beta Centauri taken through an experimental version of the vector-APP. Leiden University, University of Arizona
Until now, only about 2,000 exoplanets have been detected, and only a handful of those have been observed. This is quite surprising when the NASA Hubble telescope has seen millions of stars; you'd think that there would be more than 2,000 planets out there for us to glimpse. And most of those are only inferred to exist. Hopefully, the vector-APP will solve some of our planet-imaging problems, and help us to discover a wealth of new worlds.
[Via University of Montreal]