Centaurs, distant small bodies, and what brief stellar disappearances reveal about sizes, rings, and atmospheres.
Some Centaurs release gas and dust too far from the Sun for ordinary water-ice sublimation to explain their activity efficiently. More volatile species, release of trapped gas during ice restructuring, and the way gas moves through a porous nucleus are important alternatives. No single mechanism has been demonstrated for every active Centaur. First check what … Read more
Centaurs help connect distant icy reservoirs with the comets that enter the inner Solar System. Their temporary orbits among the giant planets let researchers study both gravitational transport and the physical changes caused by a new thermal environment. They are valuable transitional populations, not guaranteed pristine samples with a uniquely recoverable past. A dynamical category, … Read more
A stellar occultation can reveal a dwarf planet’s atmosphere by measuring how a background star fades as its light passes through the body’s limb. Gas can refract the light before the solid surface blocks it. The light curve constrains an atmosphere through a physical model; it is not a direct pressure gauge or a complete … Read more
A ring around a small Solar System body can be too faint and too close to its parent object to resolve in an ordinary image. A stellar occultation offers another route: use a distant star as a backlight and record what passes in front of it. The evidence comes from the timing and geometry of … Read more
A grazing stellar occultation happens when our line of sight to a star skims the apparent edge of a foreground body. In a lunar graze, mountains can hide the star while nearby valleys let it reappear. The resulting sequence of disappearances is a moving silhouette of lunar terrain, not a star switching on and off. … Read more
An asteroid occultation turns a brief disappearance of starlight into a measurement of an asteroid’s projected outline. The basic inputs are the disappearance and reappearance times, the observer’s location, and the shadow’s motion. The crucial qualification is that one observer normally measures a chord through the outline, not the asteroid’s full diameter. This guide follows … Read more
A tiny asteroid can be too faint to study in reflected sunlight yet still interrupt a much brighter background star. A stellar occultation uses that interruption to measure a silhouette. Its advantage is geometric: the asteroid need not be resolved into a disk. Its difficulty is temporal: the signal may last only a fraction of … Read more