Tau Ceti (タウ星, Tau Sei) is a star in the Milky Way's Orion Arm, with a solar system of eight orbiting planets, known as the Tau Ceti system (タウ星系, Tau Seikei). One of the planets inhabiting this system is Sea of the Morning Star, Marika Kato's home planet.
Tau Ceti is a G-type main-sequence star in the constellation Cetus. It is spectrally similar to the Earth's Sun, though it only has about 78% of the Sun's mass. It is considered a relatively nearby star, being just under 12 light-years from Earth and the Solar System.
(in order of distance from Tau Ceti)
- Sand of the Red Star
- Stone of the White Star
- Sea of the Morning Star
- Shining Blue Star (輝青星, Kagayaku Aohoshi) 
(after Shining Blue Star, order unknown)
- 1 unnamed planet
- 1 gas giant (largest) White Wind Star (白の風星, Shiro no Kazehoshi)
- The 6th planet is a gas giant called Rainbow of the Cloud Star (虹雲星, Niji no Kumohoshi)
- 1 frozen outermost planet End of the North Star (北の涯星, Kita no Hatehoshi)
- The names used for the Star and the constellation in Japanese are a little different from the real Tau Ceti. Tau is rendered in Hiragana instead of Katakana, while Kujira (Whale) for Ceti is rendered in Kanji instead of Hiragana. Although it is still said to be in the Orion Arm.
- The real Tau Ceti has recently been found to have five planets - one of which (the fourth) is within the habitable zone.
- In Volume 7, the Silent Whisper started its FTL jump beyond the sixth planet's orbit - presumably this is where the gravitational pull of Tau Ceti is low enough to perform jumps.