90568 Goibniu

Discovery

• 
  The 1.2-meter Samuel Oschin telescope that was used to discover Goibniu on 13 April 2004

Goibniu was discovered on 13 April 2004 by the Near-Earth Asteroid Tracking (NEAT) survey,^[14] which was a NASA-directed project for finding near-Earth asteroids in the sky using telescopes at various observatories across the United States.^[15] The telescope that discovered Goibniu was the 1.22-meter (48 in) Samuel Oschin telescope at Palomar Observatory in San Diego County, California.^[14] The people involved in making the discovery observations at Palomar included Steven Pravdo, D. MacDonald, Kenneth Lawrence and Michael D. Hicks.^[14][15] The discovery of Goibniu was announced by the Minor Planet Center (MPC) on 14 April 2004, after several other observatories observed the object.^[14]

Number and name

Classification

Goibniu is located in the classical region of the Kuiper belt 39–48 AU from the Sun,^{[4]: 53 } and is thus classified as a classical Kuiper belt object (sometimes known as a "cubewano").^{[4]: 55 } The high orbital inclination of Goibniu makes it a dynamically "hot" member of the classical Kuiper belt.^{[3]: 3 } The hot classical Kuiper belt objects are believed to have been scattered by Neptune's gravitational influence during the Solar System's early history.^{[22]: 230 }

Size

According to measurements of its infrared thermal emission by the Herschel and Spitzer space telescopes, Goibniu has a diameter of 680 Â± 34 km (423 Â± 21 mi)^[3] Goibniu is large enough that some astronomers including Noemi Pinilla-Alonso and Michael Brown once considered it as a possible dwarf planet.^{[26][28][12][29]}. Gonzalo Tancredi also considered it as a possible dwarf planet in 2010, though he did not propose its official classification to the IAU.^[26] However, its low albedo suggests it has never been resurfaced and thus is unlikely to have the planetary geology thought to be typical of dwarf planets.^[13]

Rotation, shape and density

Based on light curve observations, Goibniu rotates once on its axis every 5.86±0.03 hours. Goibniu has a fairly low light curve amplitude of 0.16±0.03,^[7] which suggests that it could either be a spheroid with small albedo spots or an ellipsoid whose rotation axis is pointed towards Earth.^[7] However light curve studies measured that it has an estimated b to a axis ratio being around b/a=1.16±0.03.^[30] Its mass and density is unknown, because it has no known moons for scientists calculate the exact mass and density of it through Kepler's third law. However, we can still estimate its density through assuming it's a stable Jacobii ellipsoid. Then the results of its density will be approximately between 1.14 to 1.49 g/cm³ with an absolute lowest limit of 0.37 g/cm³.^[30]

Surface and spectra

Goibniu is a moderately red trans-Neptunian object with a measured V-R color index of approximately 0.52.^[8] It has a dark surface with a very low geometric albedo of about 0.077+0.0084
−0.0077.^[3]