Palomar–Leiden Trojan survey

While the discovery date aligns with the second Palomar–Leiden Trojan survey, Euneus has not received a "T-2" prefixed survey designation, which was assigned to the discoveries made by the fruitful collaboration between the Palomar and Leiden observatories in the 1960s and 1970s. Gehrels used Palomar's Samuel Oschin telescope (also known as the 48-inch Schmidt Telescope), and shipped the photographic plates to Ingrid and Cornelis van Houten at Leiden Observatory where astrometry was carried out. The trio are credited with the discovery of several thousand asteroids.^[9]

Rotation period

In January 2013, Robert Stephens at the Center for Solar System Studies attempted to obtain a rotational lightcurve of Euneus from photometric observations. However, during three consecutive nights of observations, no rotation period could be determined as the lightcurve's brightness did not vary by more than 0.01 magnitude (U=n.a.).^[11]

In April 2015, follow-up observations by Stephens gave a period of 9.73±0.02 hours, still with a low brightness amplitude of 0.09 magnitude, indicating that the body is likely of spherical shape (U=2). Stephens also reanalyzed his data from 2013 using the newly obtained period which still resulted in an essentially flat lightcurve. He concluded that the body was possibly observed near pole-on during the 2013-opposition.^{[7][8][lower-alpha 1]}

Diameter and albedo

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Euneus measures 39.77 kilometers in diameter and its surface has an albedo of 0.093,^[6] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 48.48 kilometers based on an absolute magnitude of 10.3.^[7]