TOI-4468 b is a hot Jupiter, a gas giant on a very tight orbit, with an unusual neighbour. It is about the size of Jupiter and about half its mass, and it races around its star, an orange dwarf about 1,200 light-years away, every 2.77 days.
It was discovered in 2026 by a team led by Joseph Livesey. NASA's TESS satellite and several ground-based telescopes caught it crossing in front of its star, which gave its size, and the NEID spectrograph measured its mass from the wobble it gives the star. The same data revealed a second planet, TOI-4468 c, a smaller planet on a 7-day orbit just outside the giant. There is also a hint of a third, a possible giant on an orbit of about 624 days, but that signal could not be confirmed.
That arrangement is what makes the system stand out. The team describes TOI-4468 as unique among known systems in having a close outer companion with no inner one. From the planets' orbits, they argue that the system never went through a particular gravitational resonance thought to tilt the orbits of companions in similar systems, which offers a clue to how hot Jupiters reach such tight orbits. They also discuss the possibility that an inner companion exists but has not been detected. TOI-4468 b is far too hot for liquid water.