Observatory achieves ‘first light’ with new planet detector

A new planet-hunting instrument at the WM Keck Observatory has achieved ‘first light’, capturing its first data from the sky and marking an exciting chapter in the search for Earth-sized planets around other stars, which are extremely difficult to detect due to their small size . Operating at the Keck I telescope in Maunakea, Hawaii, the Keck Planet Finder (KPF) is the world’s most advanced high-resolution spectrometer for visible wavelengths.

“The arrival of the KPF marks an important and exciting step forward in our ability to advance the search to eventually find habitable Earth-like planets around other stars,” said Keck Observatory director Hilton Lewis. “We have been awaiting the arrival of the KPF for nearly a decade and are excited to be able to take our already very successful exoplanet discovery program to the next level.”

“Seeing KPF’s first astronomical spectrum was an exciting experience,” said Andrew Howard, KPF principal investigator and professor of astronomy at Caltech. “I am excited to use the instrument to study the great diversity of exoplanets and unravel the mysteries of how they formed and evolved to their present state.”

Last night, Wednesday 9 November, the KPF team successfully captured a first light spectrum of Jupiter with the Next Generation Instrument, followed by a spectrum of KPF’s first star, 51 Pegasi, which hosts 51 Pegasi b — the first planet orbiting a sun-like star discovered by the Doppler method. Now it is ready to begin observing distant worlds with great precision in an attempt to answer one of the most pressing questions in astronomy: are we alone?

“Before the recent explosion of exoplanet discovery over the past two decades, we didn’t really know what other planets were out there. We didn’t know if our own solar system or our own Earth were common,” said Sherry Yeh, associate instrument scientist. for KPF at Keck Observatory. “We are the first generation to actually understand other planets in our galactic neighborhood.”

About one in five sun-like stars has an Earth-sized planet in the habitable zone where atmospheric temperatures favor liquid water—the most important precursor to life as we know it.

Using the Doppler technique – a measurement pioneered at the Keck Observatory – KPF will examine and measure exoplanets through the behavior of their stars. When a planet orbits a star, it exerts a gravitational force that causes the star to “wobble.” The KPF will look for this stellar wobble, which astronomers can then measure to infer the mass and density of the planet pulling on the star.

The less massive the planet, the smaller the star’s wobble, and the harder it is to catch the starlight shifting back and forth. KPF is designed to address this challenge. Once fully operational, it will be able to detect stars moving back and forth at a speed of only 30 cm/second. To put the KPF’s power into perspective, its predecessor, the Keck Observatory’s current planet-hunting instrument called the High-Resolution Echelle Spectrometer (HIRES), detects stellar motions of 200 cm/s.

“The challenges of making measurements like this would have been considered insurmountable just a few decades ago,” said Josh Walawender, instrument scientist for KPF at Keck Observatory. “KPF is the result of an amazing amount of human ingenuity that has been applied to solving problems and overcoming obstacles to understanding the universe around us.”

What sets this state-of-the-art spectrometer apart is that it is made of an unusual type of glass-ceramic hybrid material called Zerodur—the same material used to make the iconic parts of the Keck Observatory’s primary mirror. Manufactured by Schott AG, Zerodur maintains its shape regardless of temperature fluctuations. This thermal stability is key to the KPF because any motion in the instrument can lead to spurious signals that appear to be Doppler shifts from stars. By reducing thermal motions, the KPF can detect and characterize exoplanets with unparalleled efficiency.

“This is the first spectrometer to incorporate Zerodur into its design,” said Howard. “The material, which comes in giant slabs, is very brittle and difficult to work with, but it’s what makes the KPF so sensitive to smaller planets.”

Conceived in 2014, the KPF is designed specifically for the Keck Observatory as a critical complement to NASA’s existing planet-hunting telescopes such as Kepler, TESS (Transiting Exoplanet Survey Satellite) and the Nancy Grace Roman Space Telescope, which surveys thousands of exoplanets in world search. like ours. The most likely candidates will then be studied more closely using ground-based telescopes like the Keck Observatory, which can gather detailed images and spectra to better understand atmospheric biosignatures — key indicators of temperature and what kinds of gases are present.

Scientists and engineers have spent the past few months installing and calibrating the new spectrograph at the Keck Observatory facility in Maunakea. Prior to that, parts of the KPF were assembled at UC Berkeley’s Space Science Laboratory and Caltech.

“To me, KPF represents one of the best traits of humanity: the humble desire to see and learn about the universe around us and thus better understand the place where we live,” Walawender said.

The KPF will be available to the scientific community for exoplanet research from spring 2023.