Astronomers have designed a low-cost technology that allows telescopes on Earth to observe planets beyond our solar system with greater precision. With the new attachment, ground-based telescopes can produce measurements of light intensity that rival the highest quality photometric observations from space, according to the study published online in the Astrophysical Journal.
The custom "beam-shaping" diffusers — carefully structured micro-optic devices that spread incoming light across an image — are capable of minimising distortions from the Earth's atmosphere that can reduce the precision of ground-based observations.
"This inexpensive technology delivers high photometric precision in observations of exoplanets as they transit — cross in front of — the bright stars that they orbit," said Gudmundur Stefansson, graduate student at Pennsylvania State University, and lead author of the paper.
"This technology is especially relevant considering the impending launch of NASA's Transiting Exoplanet Survey Satellite (TESS) early in 2018. It is up to ground-based facilities to rapidly and reliably follow-up on candidate planets that are identified by TESS," Stefansson added.
Diffusers are small pieces of glass that can be easily adapted to mount onto a variety of telescopes. The research team tested the new diffuser technology "on-sky" on the Hale telescope at Palomar Observatory in California, the 0.6m telescope at Davey Lab Observatory at Penn State, and the ARC 3.5m Telescope at Apache Point Observatory in New Mexico.
In all cases, images produced with a diffuser were consistently more stable than those using conventional methods — they maintained a relatively consistent size, shape, and intensity, which is integral in achieving highly precise measurements.
Using a focused telescope without a diffuser produced images that fluctuate in size and intensity. A common method of "defocusing" the telescope -- deliberately taking the image out of focus to spread out light — yielded higher photometric precision than focused observations, but still created images that fluctuated in size and intensity, the researchers found.