Title: Astronomers Capture Direct Images of Low-Mass Planet Using Keck Observatory
Published: July 3, 2023
A team of astronomers led by Kyle Franson at the University of Texas at Austin has made a groundbreaking discovery using the W. M. Keck Observatory in Hawaiʻi. They have successfully captured direct images of AF Lep b, one of the lowest-mass planets ever observed. This remarkable finding, published in the Astrophysical Journal Letters, highlights the first use of the astrometry technique in detecting a giant planet orbiting a young Sun-like star.
The technique of astrometry involves measuring the subtle movements of a host star over an extended period of time to identify any gravitational tugs caused by orbiting companions, such as planets. This method could revolutionize the way scientists discover extrasolar planets, particularly those that are challenging to detect due to their distance, mass, or orientation relative to Earth.
The planet in question, AF Lep b, is among the first of its kind to be discovered using astrometry. By directly imaging the planet, astronomers were not only able to determine its mass but also confirm that its orbit is similar to the giant planets in our own solar system. AF Lep b is approximately three times the mass of Jupiter and orbits a young Sun-like star known as AF Leporis, located 87.5 light-years away.
In order to capture direct images of the planet, the team used Keck Observatory’s adaptive optics system, which corrects for atmospheric turbulence, along with the Near-Infrared Camera 2 (NIRC2) Vector Vortex Coronagraph. These advanced technologies allowed astronomers to suppress the light from the host star, enabling a clearer view of AF Lep b. Notably, the planet is about 10,000 times fainter than its host star and is situated approximately eight times the distance between the Earth and the Sun.
“This is the first time this method has been used to find a giant planet orbiting a young analog of the Sun,” stated Brendan Bowler, an assistant professor of astronomy at UT Austin and senior author of the study. “This opens the door to using this approach as a new tool for exoplanet discovery.”
While direct imaging of planets presents significant challenges, the team believes that the “dynamically informed” approach facilitated by Keck Observatory’s advanced technology will be more efficient compared to previous blind surveys. The ability to directly measure a planet’s mass offers valuable insights into its physical properties and atmospheric chemistry.
The research team plans to conduct further studies on AF Lep b, aiming to characterize it using instruments such as the James Webb Space Telescope and the upcoming Giant Magellan Telescope and Thirty Meter Telescope. These future observations will help enhance our understanding of this intriguing low-mass planet and its unique characteristics.
This breakthrough discovery paves the way for the broader application of astrometry, offering hope for the detection of extrasolar planets that were previously challenging to observe due to their distance, mass, or orientation. With the potential to directly image and measure the masses of these elusive planets, scientists are poised to gain valuable insights into the vast diversity of planetary systems beyond our own.
Reference: “Astrometric Accelerations as Dynamical Beacons: A Giant Planet Imaged inside the Debris Disk of the Young Star AF Lep” by Kyle Franson, Brendan P. Bowler, et al., Astrophysical Journal Letters, 22 June 2023, DOI: 10.3847/2041-8213/acd6f6.