At 100 light years from Earth, a low-mass star was sending signals in a pattern that suggested that an exoplanet was orbiting the star. NASA’s Kepler mission observed a dip in the host star’s light, suggesting that the planet was crossing in front of the star during its orbit. To confirm, researchers turned to an instrument called Habitable-zone Planet Finder (HPF). It has confirmed that there is indeed an exoplanet.
HPF is an astronomical spectrograph, built by Penn State University scientists, and recently installed on the 10m Hobby-Eberly Telescope at McDonald Observatory in Texas. The instrument is designed to detect and characterise planets in the habitable-zone — the region around the star where a planet could sustain liquid water on its surface — around nearby low-mass stars.
The newly confirmed planet, called G 9-40b, is the first one validated by HPF. It is about twice the size of Earth, and orbits its star once every six Earth-days.
How it works
A spectrograph is an instrument that splits light into its component wavelengths. Scientists then measure the properties of light over a specific portion of the spectrum, and draw conclusions on what is responsible for the trends they observe.
Kepler’s observations alone were not enough to confirm a planet. It was possible that a close stellar companion was responsible for the dip in the star’s light. Precision spectroscopic observations from HPF ruled out this possibility. Shooting a high-power laser into the air, researchers generated a “laser guide star”, and subsequent observations found no evidence of blending of light or other stellar companions.
At Apache Point Observatory, researchers plotted a ground-based transit of the proposed planet using a process called diffusion-based photometry. They found that the plot agrees with the transits observed by Kepler.
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Finally, using HPF, an analysis of a set of radial velocities helped provide estimates for the planet’s mass.
The details of the findings appear in the Astronomical Journal.
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