30 Arietis (abbreviated 30 Ari) is a 6th-apparent-magnitude multiple star system in the constellation of Aries. 30 Arietis is the Flamsteed designation. 30 Arietis A and B are separated by , or about at a distance of 145 light-years away. The main components of both systems are both binaries with composite spectra belonging to F-type main-sequence stars, meaning they are fusing hydrogen in their cores. 30 Arietis B also has a second stellar companion, making a total of five stars. The 30 Arietis system is 910 million years old, one fifth the age of the Sun.
30 Arietis A and B are separated by 38.1", corresponding to 1,700 AU at a distance of 145 light-years. The pair are at almost the same distance, have very similar proper motions, and are considered almost certain to be gravitationally bound with a likely period around 34,000 years. The main components of both systems are both binaries with composite spectra belonging to F-type main-sequence stars, meaning they are fusing hydrogen in their cores.
30 Arietis A is a spectroscopic binary with an orbital period of 1.1 days. The primary Aa is an F-type main sequence star about 31% more massive than the Sun, while the companion Ab is a faint red dwarf only about 15% the mass of the Sun.
30 Arietis B has been reported to have a red dwarf companion C at a distance of , and another companion Bb at about . 30 Arietis Bb has a minimum mass consistent with a giant planet, but in 2020, after the orbital inclination was measured, the "planet" was found to fall in the mass range of a red dwarf star. The more distant companion is referred to as C to distinguish it from Bb, and at about 0.5" it has been imaged using adaptive optics.
30 Arietis Bb (sometimes abbreviated 30 Ari Bb) is a red dwarf which orbits the F-type main sequence star 30 Arietis Ba. The red dwarf, initially believed to be a massive planet or brown dwarf, was announced in a paper published online on September 24, 2009. It was discovered by using precision radial velocity measurements from the echelle spectrograph installed on the Alfred-Jensch Telescope in Karl Schwarzschild Observatory. The object has a minimum mass of nearly 10 times that of Jupiter. In 2020, after the inclination of the planetary orbit was measured to be just 4.14ð, the "planet" was found to fall in the mass range of red dwarf stars.