The geology and geophysics of Kuiper Belt object (486958) Arrokoth.

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers.

Detailed images of asteroid 25143 Itokawa from Hayabusa.

Rendezvous of the Japanese spacecraft Hayabusa with the near-Earth asteroid 25143 Itokawa took place during the interval September through November 2005. The onboard camera imaged the solid surface of this tiny asteroid (535 meters by 294 meters by 209 meters) with a spatial resolution of 70 centimeters per pixel, revealing diverse surface morphologies. Unlike previously explored asteroids, the surface of Itokawa reveals both rough and smooth terrains.

The recent expansion of Pluto's atmosphere.

Stellar occultations--the passing of a relatively nearby body in front of a background star--can be used to probe the atmosphere of the closer body with a spatial resolution of a few kilometres (ref. 1). Such observations can yield the scale height, temperature profile, and other information about the structure of the occulting atmosphere.

The binary Kuiper-belt object 1998 WW31.

The recent discovery of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth, main-belt and Trojan asteroids have subsequently been discovered. The Kuiper belt-the region of space extending from Neptune (at 30 astronomical units) to well over 100 AU and believed to be the source of new short-period comets-has become a fascinating new window onto the formation of our Solar System since the first member object, not counting Pluto, was discovered in 1992 (ref.

Radar and optical observations of asteroid 1998 KY26.

Observations of near-Earth asteroid 1998 KY26 shortly after its discovery reveal a slightly elongated spheroid with a diameter of about 30 meters, a composition analogous to carbonaceous chondritic meteorites, and a rotation period of 10.7 minutes, which is an order of magnitude shorter than that measured for any other solar system object. The rotation is too rapid for 1998 KY26 to consist of multiple components bound together just by their mutual gravitational attraction.

Solid C triple bond N bearing material on outer solar system bodies.

Using telescopic observations by ourselves and other observers, we have identified cyano-group containing molecules in the very dark solids on the surfaces of a few D-class asteroids, the dust of some comets, and low-albedo hemisphere of Iapetus, and the rings of Uranus, through spectroscopic detection of the 2.2-micrometers overtone of the C triple bond N stretching fundamental mode. The occurrence of this band on all four classes of small Solar System bodies may be diagnostic of the duration of exposure and degree of modification of surface materials, and may also establish a link between outer Solar System and interstellar materials.

Improved orbital and physical parameters for the pluto-charon system.

Analysis of the observations of several Pluto-Charon occultation and transit events in 1985 and 1986 has provided a more detailed knowledge of the system. The sum of the radii of Pluto and Charon is 1786 +/- 19 kilometers, but the individual radii are somewhat more poorly determined; Pluto is 1145 +/- 46 kilometers in radius and Charon is 642 +/- 34 kilometers in radius. The mean density of the system is 1.

The detection of eclipses in the pluto-charon system.

The first eclipses between Pluto and its satellite ("Charon") were detected in January and February 1985, confirming the satellite's existence. Eclipses lasting a few hours will now occur at 3.2-day intervals for the next 5 to 6 years and then will cease for about 120 years.

Occultation by a possible third satellite of neptune.

The 24 May 1981 close approach of Neptune to an uncataloged star was photoelectrically monitored from two observatories separated by 6 kilometers parallel to the occultation track. An 8.1-second drop in signal, recorded simultaneously at both sites, is interpreted as resulting from the passage of a third satellite of Neptune in front of the star.