Author: Jared Males

During our recent observing run we tested a new set of coronagraphs (devices for blocking star light so we can see planets!), which were developed by our friends Gilles Otten, Frans Snik, and Matt Kenworthy at Leiden University, in the Netherlands. Today Gilles gave a talk at the Spirit of Lyot Conference in Montreal, Canada. The new coronagraphs work spectacularly well! You can read about these results in Dutch, French, and in English.

Here is our announcement of this great news:

Astronomers develop breakthrough optical component for detecting exoplanets close to their host stars

Astronomers from Leiden University (the Netherlands) and the University of Arizona (USA) have successfully commissioned a new type of optic that can reveal the image of an exoplanet next to its parent star. The ‘vector Apodizing Phase Plate’ (vector-APP) coronagraph was installed at the 6.5-m Magellan Clay telescope in Chile in May 2015, and the first observations demonstrated an unprecedented contrast performance very close to the star, where planets are more likely to reside. These results will be presented by PhD student Gilles Otten (Leiden) this Monday to the scientific community at the “Spirit of Lyot” conference in Montreal.

Almost 2000 exoplanets have been detected to date, but only a handful of those have been imaged directly. Exoplanets are typically more than a million times fainter than and are lost in the glare of their parent star as seen from Earth. To directly image exoplanets and to characterize their atmospheres, astronomical instruments at the world’s largest telescopes use coronagraphs to suppress the overwhelming halo of light from the star.
The vector-APP coronagraph[1] uses the wavelike nature of light to cancel out the starlight whilst allowing the planet’s light to shine through.

This manipulation is implemented through a complex phase pattern that can only be manufactured using advanced liquid crystal 3D patterning techniques [2]. This technique creates two images of the star, for which dark D-shaped regions are located on opposite sides of each star image (see Figure 1). In this way, the whole region around the star can be scrutinized for planets. By combining several layers of liquid crystals, the device can be used over a wide range of wavelengths, including the infrared where the contrast between planet and star is more favorable.

On May 6, 2015 a vector-APP coronagraphic device saw first light (at 3.9 um wavelength, in the infrared range of the spectrum) at the MagAO[3] instrument, attached to the 6.5-m diameter Magellan Clay telescope in Chile. The telescope’s integrated adaptive optics system provided the instrument with sharp images of stars, which were consequently split up and modified by the coronagraph to exhibit dark holes in which much fainter planets could be imaged than without the vector-APP coronagraph.

Frans Snik (Leiden University), who invented the principle behind the new vector-APP coronagraph, says: “It is fantastic to see that after all our design work and lab testing, this new approach works perfectly at the telescope on the very first night!” Gilles Otten adds: “We knew that we were in business as soon as we saw the first picture on the screen in the telescope control room.”

Jared Males (NASA Sagan Fellow, University of Arizona) is excited about the opportunities of the vector-APP: “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 (Leiden) concludes: “This new coronagraph technology is also excellent news for the extremely large telescopes currently under construction. With a vector-APP coronagraph in the next generation of telescopes, we can search for planets around nearby stars with unprecedented sensitivity.”

The advanced liquid crystal technology that the team adopted also permitted the production of extreme vector-APP designs that are not possible with more traditional manufacturing technologies. These new designs produce dark holes that cover the full 360 degrees around the target stars. The first data from an experimental device already shows the viability of this novel approach (see Figure 2).

Support from the William F. and Elizabeth Lucas Junior Faculty Astronomy Award and the NASA Origins of Solar Systems program made this exciting commissioning possible at the MagAO instrument in Chile. This work was performed in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

[1] For an introduction to the principles behind the vector-APP coronagraph, see Snik et al. (2012) and Otten el al. (2014). The name “vector-APP” stems from “Apodizing Phase Plate” based on polarization (vector) techniques. The original optical theory was developed by Johanan Codona at the University of Arizona.

[2] The vector-APP coronagraph devices for MagAO were developed in collaboration with the group of Dr. Michael Escuti at North Carolina State University, and were produced by ImagineOptix.

[3] The MagAO instrument is introduced in Morzinski et al. (2014). See //

Contacts:
Dr. Frans Snik (in the Netherlands)
Leiden Observatory, Leiden University
snik@strw.leidenuniv.nl

Dr. Matthew Kenworthy (at the “Spirit of Lyot”) conference
Leiden Observatory, Leiden University
Kenworthy@strw.leidenuniv.nl

Dr. Jared Males
University of Arizona
jrmales@email.arizona.edu