Astronomers Capture Sharp Images of Star LkCa 15, Changing the Way We Detect Forming Planets
TL;DR
Using Hawaii’s Subaru and Keck telescopes, astronomers captured detailed images of the LkCa 15 star system, providing new insights into planet formation. Earlier observations had suggested the presence of three super-Jupiter planets in the system’s disk, but this new analysis revealed that the light previously attributed to planets was actually from the disk itself. However, astronomers believe smaller, undetected planets likely exist and are similar in size to Jupiter or Saturn. This refined technique could help detect planets still forming and deepen our understanding of planetary development.
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With the help of two of Hawaii’s most powerful telescopes, astronomers have captured what they describe as “groundbreaking” sharp images of a planetary system in the process of formation.
They also didn’t find the three planets that were previously detected. The star in question is LkCa 15, a young Sun-like T Tauri star located 473 light-years away, and the absence of these planets isn’t a bad sign. Nor does it suggest that planet formation isn’t happening.
Instead, the findings reflect a more refined technique that could help improve the accuracy of detecting still-forming planets in the future, as well as advancing our understanding of how planets are created.
We know that when stars form, they’re surrounded by a rotating disc of dust, gas, and rocks. Planetary formation occurs when particles within this disc collide, grow, and gradually pull in more material due to increasing gravity, eventually forming a planet and clearing the material from their orbit.
In the past, astronomers have captured some spectacular images of these protoplanetary disks and have found strong evidence of material being cleared away in orbit.
Additionally, previous research teams believed they had detected three ‘super-Jupiter’ planets orbiting within a Solar System-sized gap in LkCa 15’s disc. They used a method known as sparse aperture masking interferometry to distinguish the planets’ light from that of the star.
However, by using the Subaru Telescope and the WM Keck Observatory, an international research team has determined that what was thought to be planetary light was actually light from the disc itself. This, it turns out, was an easy mistake to make.
“LkCa 15 is a highly complex system,” explained astrophysicist Thayne Currie from NASA-Ames Research Center and the Subaru Telescope.
“Prior to analysing our Keck and Subaru data and given the same prior aperture masking data, we also would have concluded that LkCa 15 has three detected superjovian planets.”
The research was very detailed. Using Subaru, the team employed a state-of-the-art planet imaging tool, the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO), attached to the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), to capture near-infrared images of the disc.
At the WM Keck Observatory, they used the Near-Infrared Camera (NIRC2) to capture images in the longer wavelengths that are emitted by young planets. They also found images of the system taken by NIRC2 in 2009 in the Keck archives for comparison.
This data, both the older images and the new ones, revealed that most of the light surrounding LkCa 15 actually comes from the visible edge of the disc, which had the same brightness previously attributed to protoplanets.
But that doesn’t mean there aren’t any planets there. The team believes they probably exist but are smaller and dimmer than what’s detectable – perhaps around the size of Jupiter or Saturn rather than massive super-Jupiters.
If we manage to find these planets, they could offer invaluable insights into the process of planetary formation, not just in general, but particularly as it relates to our own Solar System.
“The planets in this infant solar system could actually be much more like our own Solar System than previously thought,” Currie said.
“They’re likely there, possibly embedded within the disc. We’ll keep trying to find them.”
The research has been accepted into The Astrophysical Journal Letters and has been published on arXiv.
