Short answers, pulled from the story.
Detached objects form a dynamical class of minor planets where their closest approach to the Sun remains far beyond Neptune's gravitational reach. Their perihelion distances exceed 40 astronomical units, creating a buffer zone between them and the giant planets.
Astronomers discovered an object named Sedna in the year 2003 that did not fit any known category of trans-Neptunian objects. Michael Brown originally classified Sedna as an inner-Oort-cloud object due to its 76 AU perihelion distance.
As of 2025, four known sednoids exist including Leleākūhonua which was identified in 2019. These objects share highly elliptical orbits with semi-major axes reaching several hundred astronomical units.
Scientists have proposed multiple explanations for how detached objects acquired their extreme orbital configurations without direct scattering by Neptune. One theory involves encounters with passing stars during the early formation of the Solar System while another possibility includes Neptune migration that once featured a much more eccentric orbit capable of tugging objects into current positions.
Mike Brown who discovered Sedna later proposed the existence of a hypothetical massive planet beyond Neptune called Planet Nine. This hypothesis suggests gravitational influence from an unobserved body between two hundred and twelve hundred astronomical units explains clustered orbits of distant objects.