Using high-resolution, adaptive optics observations in the polarized light, an international group of astronomers led by Hauyu Liu from European Space Observatory (Garching, Germany) has verified the presence of the key features associated with the disk fragmentation model -- large-scale arms and arcs surrounding four young stars undergoing luminous outbursts, including the prototype
FU Orionis star itself.
Z Canis Majoris is a unique pre-main-sequence binary system consisting of an
FU Orionis star and a young Herbig Be star still embedded in a dust cocoon.
Astronomers in the 1930s saw an unexplained light burst in a star known as
FU Orionis, and since then researchers have observed a sudden and dramatic brightening in five more stars in other constellations.
One such object is the star/disk combination known as FU Orionis and its associated nebula Cederblad 59.
FU Orionis and Cederblad 59 sit 2.1[degrees] east of deep yellow [Phi.sup.2] ([[phi].sup.2]) Orionis.
T Tauri stars show outbursts of this kind, and so do
FU Orionis stars, but
FU Orionis spectra show absorption of light by calcium, whereas Object 50 shows emission by calcium.
Spectroscopic observations with the 8-meter Gemini North telescope on Mauna Kea last November 6th indicate that the highly reddened object is undergoing a rare, violent accretion episode known as an
FU Orionis eruption.
Second, the nebula flares into view only when its illuminating star (possibly an
FU Orionis variable) experiences an outburst.
Sixty years ago, a modest 16th-magnitude T Tauri star (or so we believe) now named
FU Orionis brightened by 6 magnitudes over a period of a year.
T Tau S flared in the late 1980s in an outburst that may have been like that of the famous young, eruptive variable
FU Orionis. Its infrared flux has since decreased.
A handful of Class II objects appear to be
FU Orionis stars.