Characteristics
HD 40307, being a K-type star, emits orange-tinted light. Additionally, at approximately three-fourths the Sun's radius and mass, it is smaller and less massive than the Sun. HD 40307's temperature has been observed to be slightly under 5000 K. This is relatively high for a K-type star and approaches the temperatures normally found in G-type stars such as the Sun.
The astronomers who discovered the planets orbiting HD 40307 suggested that the metallicities of stars determine whether or not the planetary bodies that orbit them will be terrestrial, like Earth, or gaseous, like Jupiter and Saturn.
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