The correct answer is Goldilocks zone.

• Goldilocks Zone:
  • A habitable zone, also called the “Goldilocks zone”, is the area around a star where it is not too hot and not too cold for liquid water to exist on the surface of surrounding planets.
  • Our Earth is in the Sun’s Goldilocks zone.
  • If Earth were where the dwarf planet Pluto is, all its water would freeze; on the other hand, if Earth were where Mercury is, all its water would boil off.
  • Life on Earth started in water, and water is a necessary ingredient for life as we know it.

• Habitable-zone Planet Finder:
  • HPF is an astronomical spectrograph, built by Penn State University scientists, and recently installed on the 10m Hobby-Eberly Telescope at McDonald Observatory (US).
  • The HPF searches for exoplanets by using the Doppler effect.
  • A spectrograph is an instrument that splits light into its component wavelengths. Scientists measure the properties of light over a specific portion of the spectrum, and draw conclusions on what is responsible for the trends they observe.
  • The HPF provides the highest precision measurements of infrared signals from nearby low-mass stars, and astronomers use it to validate the candidate planet by excluding all possibilities of contaminating signals to a very high level of probability.
  • HPF is currently surveying the nearest low-mass stars, also called M-dwarfs, which are the most common stars in the galaxy - with the goal of discovering exoplanets in our neighborhood.