Cupid (moon)

{{Short description|Moon of Uranus}}

{{distinguish|763 Cupido}}

{{Infobox planet

| name = Cupid

| mpc_name = Uranus XXVII

| alt_names =

| pronounced = {{IPAc-en|ˈ|k|juː|p|ə|d}}

| adjectives = Cupidinian{{IPAc-en|k|juː|p|ɪ|ˈ|d|ɪ|n|i|ə|n}}Gifford & Dyce (1833) Some account of Shirley and his writings, p. 46

| image = Cupidmoon.png

| caption =

| discoverer = Mark R. Showalter and Jack J. Lissauer

| discovered = August 25, 2003

| semimajor = 74,392 km

| orbital_speed =

| eccentricity = 0.0013

| period = 0.618 d

| inclination = 0.1° (to Uranus' equator)

| satellite_of = Uranus

| mean_radius = {{val|8.9|0.7|u=km}}{{refn|Showalter & Lissauer (2006), as cited in Ćuk et al. (2022).}}

| surface_area = ~1,000 km²

| volume = ~3,000 km³

| mass = ~{{val|1.5|-|3.5|e=15|u=kg}}

| density = {{val|0.5|-|1.2|u=g/cm3}}

| surface_grav = ~{{Gr|1.5e-6|8.9|4}}–{{Gr|3.5e-6|8.9|4}} m/s²

| escape_velocity = ~{{V2|1.5e-6|8.9|4}}–{{V2|3.5e-6|8.9|4}} km/s

| rotation = synchronous

| axial_tilt = 0

| albedo = 0.08 (assumed)

| magnitude =

| single_temperature = ~64 K

}}

Cupid is an inner satellite of Uranus. It was discovered by Mark R. Showalter and Jack J. Lissauer in 2003 using the Hubble Space Telescope. It was named after a character in William Shakespeare's play Timon of Athens.

Cupid is the smallest known inner Uranian satellite (apart from possibly Mab), crudely estimated to be only about 18 km in diameter. This and the dark surface made it too dim to be detected by the Voyager 2 cameras during its Uranus flyby in 1986.

The orbit of Cupid is separated by only 863 km from the orbit of the larger moon Belinda. Unlike Mab and Perdita—two Uranian satellites also discovered in 2003—it does not seem to be perturbed. Despite this, it has the least stable orbit of Uranus's inner moons—it is likely to collide with Belinda in the next 100,000–10 million years, due to resonance interactions that cause the smaller Cupid to drift into a more dangerous orbit over this timescale.{{cite journal |last1=French |first1=Robert S. |last2=Showalter |first2=Mark R. |title=Cupid is doomed: An analysis of the stability of the inner uranian satellites |journal=Icarus |date=August 2012 |volume=220 |issue=2 |pages=911–921 |doi=10.1016/j.icarus.2012.06.031|arxiv=1408.2543 |bibcode=2012Icar..220..911F |s2cid=9708287 }}

Cupid is at most 500 million years old.

Following its discovery, Cupid was given the temporary designation S/2003 U 2. It is also designated Uranus XXVII.