55 Cancri is a binary star system located 41[1] light-years away from the Sun in the zodiac constellation of Cancer.

In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars.

[21] In December 2015, the IAU announced the winning names were Copernicus for 55 Cancri A and Galileo, Brahe, Lipperhey, Janssen and Harriot for its planets (b, c, d, e and f, respectively).

They honor the astronomers Nicolaus Copernicus, Galileo Galilei, Tycho Brahe and Thomas Harriot and the spectacle makers and telescope pioneers Hans Lipperhey and Jacharias Janssen.

[1] 55 Cancri A has an apparent magnitude of 5.95, making it just visible to the naked eye under very dark skies.

Despite their wide separation, the two stars appear to be gravitationally bound, as they share a common proper motion.

[27] It is more enriched than the Sun in elements heavier than helium, with 186% the solar abundance of iron; it is therefore classified as a rare "super metal-rich" (SMR) star.

[10] A hypothesis for the high metal content in SMR dwarf stars is that material enriched in heavy elements fell into the atmosphere from a protoplanetary disk.

The lack of a deep convection zone would mean that the outer layers would retain higher abundance ratios of these heavy elements.

[30] Observations of 55 Cancri A in the submillimeter region of the spectrum have thus far failed to detect any associated dust.

These radial velocity measurements still showed a drift unaccounted for by this planet, which could be explained by the gravitational influence of a more distant object.

[35] Calculations gave the disk radius at least 40 AU, similar to the Kuiper belt in the Solar System, with an inclination of 25° with respect to the plane of the sky.

[39] However, Dawson and Fabrycky (2010)[33] concluded that the 2.8-day planet was indeed an alias, as suggested by Wisdom (2005), and that the correct period was 0.7365 of a day.

Astrometric observations with the Hubble Space Telescope measured an inclination of 53° of the outer planet d,[37] though this result relies on the precise orbital parameters which have been substantially revised since this was published.

[45] A study released in 2019 showed that undiscovered terrestrial planets may be able to orbit safely in this region at 1 to 2 AU; this space includes the outer limits of 55 Cancri's habitable Zone.

[46] In 2021, it was found that terrestrial planets with comparable water content to Earth may have indeed been able to form and survive between the planets f and d.[47] As for the space outside d's orbit, its stability zone begins beyond 10 AU, though there is a stability zone between 8.6 and 9 AU due to a 2:1 resonance.