Discovery of a jet from the single HAe/Be star HD 100546
  Young accreting stars drive outflows that collimate into jets, which can be
seen hundreds of au from their driving sources. Accretion and outflow activity
cease with system age, and it is believed that magneto-centrifugally launched
disk winds are critical agents in regulating accretion through the
protoplanetary disk. Protostellar jets are well studied in classical T~Tauri
stars ($M_\star\lesssim2\,M_\odot$), while few nearby ($d\lesssim150\,$pc)
intermediate-mass stars ($M_\star=2-10\,M_\odot$), known as Herbig Ae/Be stars,
have detected jets. We report VLT/MUSE observations of the Herbig~Ae/Be star
HD~100546 and the discovery of a protostellar jet. The jet is similar in
appearance to jets driven by low-mass stars and compares well with the jet of
HD~163296, the only other known optical jet from a nearby Herbig~Ae/Be star. We
derive a (one-sided) mass-loss rate in the jet of $\log \dot{M}_{jet} \sim
-9.5$ (in $M_\odot$\,yr$^{-1}$) and a ratio of outflow to accretion of roughly
$3\times10^{-3}$, which is lower than that of CTTS jets.
  The discovery of the HD~100546 jet is particularly interesting because the
protoplanetary disk around HD~100546 shows a large radial gap, spiral
structure, and might host a protoplanetary system. A bar-like structure
previously seen in H$\alpha$ with VLT/SPHERE shares the jet position angle,
likely represents the base of the jet, and suggests a jet-launching region
within about 2\,au. We conclude that the evolution of the disk at radii beyond
a few au does not affect the ability of the system to launch jets.
