astronomer Eric Mamajek reported that an extremely magnetically active M dwarf (having strong coronal X-ray emission), 1.16 degrees south of Canopus, appears to share a common proper motion with Canopus. The projected separation of the M dwarf 2MASS J06234738-5351131 ("Canopus B") is approximately 1.9 parsecs. However, despite this large separation, it is still within the estimated tidal radius (2.9 parsecs) for the massive star Canopus. No star closer than Canopus is more luminous than it, and it has been the brightest star in Earth's night sky during three epochs over the past four million years. Other stars appear brighter only during relatively temporary periods, during which they are passing the Solar System much closer than Canopus. About 90,000 years ago, Sirius moved close enough that it became brighter than Canopus, and that will remain so for another 210,000 years. But in 480,000 years, as Sirius moves further away and appears fainter, Canopus will once again be the brightest, and will remain so for a period of about 510,000 years. Role in navigation The southeastern wall of the Kaaba in Mecca is aligned with the rising point of Canopus, and is also named Janūb. The Bedouin people of the Negev and Sinai knew Canopus as Suhayl, and used it and Polaris as the two principal stars for navigation at night. Because it disappears below the horizon in those regions, it became associated with a changeable nature, as opposed to always-visible Polaris, which was circumpolar and hence 'steadfast'. The south celestial pole can be approximately located using Canopus and another bright star, Achernar, as the three make an equilateral triangle. Canopus sits on an imaginary line that extends one way to Sirius and to the south celestial pole. Canopus's brightness and location well off the ecliptic make it useful for space navigation. Many spacecraft carry a special camera known as a "Canopus Star Tracker" plus a Sun sensor for attitude determination. Mariner 4 used Canopus for second axis stabilisation (after locking on the Sun) in 1964, the first time a star had been used. Spectrum Canopus was little-studied by western scientists before the 20th century. It was given a spectral class of F in 1897, an early use of this extension to Secchi class I, applied to those stars where the hydrogen lines are relatively weak and the calcium K line relatively strong. It was given as a standard star of F0