The
spectrum of HD 181720 presents as an ordinary
G-type main-sequence star with a
stellar classification of G1V.[3] It is an older star with an estimated age of roughly 12 billion years[5] and a minimal level of
magnetic activity in its
chromosphere.[3] The star has 87% of the mass of the Sun but the radius is now 42% larger than the Sun's.[5] Its
metallicity content, as measured by the abundance of iron, is three-tenths as much as in the Sun. HD 181720 is radiating more than double the luminosity of the Sun from its
photosphere at an
effective temperature of 5,781 K.[3]
The star HD 181720 is named Sika. The name was selected in the
NameExoWorlds campaign by
Ghana, during the 100th anniversary of the
IAU. Sika means
gold in the
Ewe language.[8][9]
Planetary system
In 2009, a
gas giant planet was found in orbit around the star.[3] It was named "Toge" in 2019.[8][9] The planets around such metal-poor stars are rare (only two known similar cases are
HD 111232 and
HD 22781, as of 2019).[10] The upper bound on the mass of this component is 32 times the mass of Jupiter, which would place it in the
brown dwarf range.[11]