Demonstration of exoplanet detection using an infrared telescope array

Abstract

Context. Technology is being developed for the characterization and detection of small, Earth-size exoplanets by nulling interferometry in the mid-infrared waveband. While high-performance nulling experiments have shown the possibility of using the technique, to achieve these goals, nulling has to be done on multiple beams, with high stability over periods of hours. To address the issues of the perceived complexity and difficulty of the method, a testbed was developed for the Terrestrial Planet Finder Interferometer (TPF-I) project which would demonstrate four beam nulling and faint exoplanet signal extraction at levels traceable to flight requirements. Containing star and planet sources, the testbed would demonstrate the principal functional processes of the TPF-I beam-combiner by generating four input beams of star and planet light, and recovering the planet signature at the output. Aims. Here we report on experiments designed with traceability to a flight system, showing faint exoplanet signal detection in the presence of strong starlight. The experiments were designed to show nulling at the flight level of ≈10 −5 , starlight suppression of 10 −7 or better, and detection of an exoplanet at a contrast of 10 −6 compared to the star. This performance level meets the flight requirements for the parts of the detection process that can be demonstrated using a monochromatic source. To achieve these results, the testbed would have to operate stably for several hours, showing control of disturbances at levels equivalent to the flight requirements. Methods. A test process was designed which would show that the necessary performance could be achieved. To show reproducibility, the tests were run on three separate occasions, separated by several days. The tests were divided into three main parts which would show first, starlight suppression, second, a realistic faint exoplanet signal production, and finally, exoplanet signal detection in the presence of the starlight. Results. A number of data sets were acquired showing the achievement of the required performance. The data reported here show nulling at levels between about 5.5 and 8.5 × 10 −6 , starlight suppression between 8.4 × 10 −9 and 1.4 × 10 −8 , and detection of planet signals with contrast to the star between 3.8 × 10 −7 and 4.4 × 10 −7 . The signal to noise ratios for the detections were between 14.0 and 26.9. These data met all the criteria of the demonstration, showing reproducible stable performance over several hours of operation. Conclusions. These data show the successful execution, at flight-like performance levels, of almost the whole exoplanet detection process using a four beam, nulling beam-combiner.

Space interferometry beyond exoplanetology: Can interdisciplinary collaboration contribute to the future of this technique?

“…At some point, however, the field will only be able to advance if efficient direct imaging (including spectroscopy) becomes available. The feasibility of the concept has been demonstrated quite satisfactorily by Peters et al (2010) and Martin & Booth (2010). In the eyes of many it was the clear choice for a flagship space mission (cf.…”

TPF-Interferometer: a decade of development in exoplanet detection technology

“…The testbed was very successful in proving the effectiveness of the TPF-I combination of nulling and phase chopping at suppressing starlight and drawing a faint planet signal out of the noise. TPF-I Milestone 4 tests demonstrated starlight suppression of 10 -8 (while nulling at 10 -5 ) and detection of a planet having intensity less than 5×10 -7 of that of the star [65], [66] .…”

Characterizing the atmosphere of Proxima b with a space-based mid-infrared nulling interferometer

“…needed for the space mission. 31 At 10 µm with 10% bandwidth, this has achieved nulling of 8 × 10 −6 (the flight requirement is 10 −5 ), starlight suppression of 10 −8 after post-processing, and actual planet detection at a planet-to-star contrast of 3 × 10 −7 , i.e., the Earth-Sun contrast. The phase chopping technique 32 has also been implemented and validated on-sky with the Keck Nuller Interferometer.…”