The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color, and rich in water ice.

Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

[18] Orcus was discovered on 17 February 2004, by American astronomers Michael Brown of Caltech, Chad Trujillo of the Gemini Observatory, and David Rabinowitz of Yale University.

Precovery images taken by the Palomar Observatory as early as 8 November 1951 were later obtained from the Digitized Sky Survey.

Accordingly, the discoverers suggested naming the object after Orcus, the Etruscan god of the underworld and punisher of broken oaths.

The name was also a private reference to the homonymous Orcas Island, where Brown's wife had lived as a child and that they visit frequently.

[9] Simulations by the Deep Ecliptic Survey show that over the next 10 million years Orcus may acquire a perihelion distance (qmin) as small as 27.8 AU.

[26][27] Astronomer José Luis Ortiz and colleagues have derived a possible rotation period of about 10.5 hours, assuming that Orcus is not tidally locked with Vanth.

[11] Orcus appears to have an albedo of about 21–25%,[11] which may be typical of trans-Neptunian objects approaching the 1,000 km (620 mi) diameter range.

[12] The first spectroscopic observations in 2004 showed that the visible spectrum of Orcus is flat (neutral in color) and featureless, whereas in the near-infrared there were moderately strong water absorption bands at 1.5 and 2.0 μm.

[38] Further infrared observations in 2004 by the European Southern Observatory and the Gemini telescope gave results consistent with mixtures of water ice and carbonaceous compounds, such as tholins.

[39] Later in 2008–2010 new infrared spectroscopic observations with a higher signal-to-noise ratio revealed additional spectral features.

On the other hand, a mixture of only ammonia hydrate, tholins and water ice failed to provide a satisfactory match.

[26] As of 2010, the only reliably identified compounds on the surface of Orcus are crystalline water ice and, possibly, dark tholins.

[26] The reflectance spectrum of Orcus shows the deepest water-ice absorption bands of any Kuiper belt object that is not associated with the Haumea collisional family.

[26] Crystalline water ice on the surfaces of trans-Neptunian objects should be completely amorphized by the galactic and Solar radiation in about 10 million years.

[13] The 1.65 μm band on Orcus is broad and deep (12%), as on Charon, Quaoar, Haumea, and icy satellites of the giant planets.