'Groundbreaking' Sharp Images of Distant Planetary System Show 3 Planets Are Missing

Astronomers have obtained stunning new images of a young star system that reveal a surprising twist: three planets that were previously detected are now missing. 

The images, taken by two powerful telescopes in Hawaii, show the system with unprecedented clarity and detail, shedding new light on the process of planet formation.

The star system, called LkCa 15, is located about 473 light-years away from Earth. It is a Sun-like star surrounded by a disc of dust and gas, which is the raw material for building planets. In 2015, a team of astronomers claimed to have found evidence of three giant planets, each about 10 times more massive than Jupiter, orbiting within a gap in the disc.

However, a new study, published in The Astrophysical Journal Letters, challenges this claim and shows that the planets were actually an illusion caused by the complex structure of the disc itself. The study is based on new observations made by the Subaru Telescope and the WM Keck Observatory, both located on Maunakea in Hawaii.

The Subaru Telescope used a state-of-the-art instrument called SCExAO (Subaru Coronagraphic Extreme Adaptive Optics), which can block out the bright light of the star and reveal fainter objects around it. SCExAO was coupled with another instrument called CHARIS (Coronagraphic High Angular Resolution Imaging Spectrograph), which can take images of the disc in different colors of near-infrared light.

The WM Keck Observatory used an instrument called NIRC2 (Near-Infrared Camera), which can also block out the starlight and take images at longer infrared wavelengths that are emitted by warm objects, such as young planets. The researchers also analyzed archival data from NIRC2 taken in 2009.

By combining these data sets, the researchers were able to create sharp and detailed images of LkCa 15 and its disc. They found that most of the light that was previously attributed to planets actually came from the edge of a section of the disc that is tilted with respect to the rest of the disc. This edge appears bright because it reflects more starlight than other parts of the disc.

The researchers also performed simulations to show how this edge could mimic the appearance of planets when observed with a technique called sparse aperture masking interferometry, which was used by the previous team to detect planets. This technique combines light from different parts of a telescope's mirror to create an image with higher resolution than possible with a single telescope.

The new study demonstrates that LkCa 15 is a highly complex system that can fool even sophisticated methods of planet detection. It also shows that SCExAO and CHARIS are powerful tools for studying protoplanetary discs and searching for planets around young stars.

The researchers emphasize that their results do not mean that there are no planets around LkCa 15. In fact, they suggest that there may be smaller planets hidden within the disc that are too faint to be detected with current instruments. They also point out that planet formation is still ongoing in this system, and that future observations may reveal new surprises.

"This is a groundbreaking result that shows how far we have come in imaging protoplanetary discs and planetary systems," said Dr. Thayne Currie, lead author of the study and an astrophysicist at NASA-Ames Research Center and the Subaru Telescope. "We are now able to see features in discs that we could only dream of before, and we can use this information to better understand how planets form and evolve."