New Technique Can Spot Smaller Exoplanets

Image comment: This image of the planets in the HR8799 system were found using vortex coronagraph
Image credits: NASA / JPL-Caltech / Palomar Observatory

Up until now, methods of detecting exoplanets beyond our solar system could only see space rocks that were very large, and also fairly far away from their parent stars. These limitations occur on account of the fact that the brightness of exoplanets can rarely be observed directly, due to the light the stars they orbit emit. This means that small planets, about the size of Earth, can only be detected with incredible difficulties. However, this class of celestial objects is thought to be the most likely to support alien life. Now, a new observations technology could surpass the previous limitations.

According to the investigators behind the new method, the technique is especially suitable for detecting small exoplanets, that orbit their parent star closer to, or even within, their respective habitable zones. The method can also detect these bodies at larger distances from our solar system than ever before, which could significantly increase the chances of astronomers finding planets that have temperatures suitable for maintaining liquid water on their surface. Experts plan to find these objects using a small instrument called a “vortex coronagraph.”

Unlike other detection methods, which rely on the use of impressively-large telescopes, this device only uses a small portion of an observatory. In a demonstrative study, the technique was used on the 1.5-meter (5-foot) Hale Telescope, located at the Palomar Observatory, in San Diego. The study team, led by NASA Jet Propulsion Laboratory (JPL) expert Gene Serabyn, managed to find three already-discovered planets using this small telescope. The space rocks orbit the star called HR 8799, and they are all gas giants similar to Jupiter, though more massive.

Initially, these bodies were found using the Mauna Kea, Hawaii-based 10-meter (33-foot) telescopes of the W.M. Keck Observatory, and the 8.0-meter (26-foot) Gemini North Observatory. “We managed to see these planets with a telescope that's smaller than one panel on the Keck telescope. What this [vortex coronagraphy] does is it allows you to consider using a much smaller telescope, and something that's much more affordable, to look for Earth-like planets,” the JPL expert tells Space. Details of how the device works can be found in the April 15 issue of the esteemed scientific publication Nature.