HD 240237 is a star in the northern constellation of Cassiopeia.^[5] It is an orange star that can be viewed with binoculars or a small telescope, but is too faint to be seen with the naked eye at an apparent visual magnitude of 8.19.^[2] This object is located at a distance of approximately 3,100 light years away from the Sun based on parallax, but is drifting closer with a radial velocity of −25 km/s.^[1]

This is an aging giant star with a stellar classification of K2III;^[3] a star that has exhausted the supply of hydrogen at its core and expanded to 78 times the radius of the Sun.^[1] S. Gettel and associates (2011) estimate the star is around 270 million years old with 1.7 times the mass of the Sun.^[3] However, S. G. Sousa and associates found a much lower mass of 0.61 times the mass of the Sun.^[4] It is radiating 1,244 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,878 K.^[1]

In 2011, Gettel et al. announced the discovery of a planet orbiting this star. They estimated a mass around 5 times that of Jupiter, with an orbital period of 2.042 years and a moderate eccentricity. Sousa et al. (2015) gave a much lower estimate of 1.53 M_J.^[4] The designation b for this object, derives from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet.^[6] In the case of HD 240237, there was only one planet, so only the letter b is used.