Kepler-440 b is a planet about 1.9 times Earth's width in the habitable zone of an orange dwarf star about 980 light-years away. The habitable zone is the range of distances where a planet could keep liquid water on its surface. It crosses in front of its star every 101 days and receives about 1.2 times the light Earth gets from the Sun, according to the NASA Exoplanet Archive.
It was confirmed in 2015 as one of twelve small Kepler planets in the habitable zone validated by a team led by Guillermo Torres, listed then as candidate KOI-4087.01. Their expected signals in the star's wobble are too small to measure, so the team validated them statistically with a method called BLENDER, which simulates large numbers of possible false alarms and compares them with the Kepler data. They added spectra, adaptive optics images and speckle observations of the stars. The study found all twelve in the habitable zone, and roughly doubled the number of known rocky planets there.
In 2016 a team led by David Armstrong studied the host stars of Kepler's most Earth-like planets, including Kepler-440, using the full Kepler record of their brightness. They measured its rotation period at about 18 days and estimated how well a planet's magnetic field could shield it from its star. Kepler-440 b had the smallest protective magnetic bubble in their sample, assuming an Earth-strength field, but even that was larger than Earth's was about 3.4 billion years ago. Its mass has not been measured; the archive's figure of about 4 Earth masses is an estimate from its size.