"Using telescopes at observatories in Chile and Arizona, Douglas Duncan (Space Telescope Science Institute) determined the spin rates and ages for 40 pre-main-sequence
stars in Orion.
Ramirez and director Lisa Kaltenegger, "The Habitable Zones of Pre-Main-Sequence
Stars" will be published in the Jan.
Each of these nebulae is associated with a pre-main-sequence
star which is still in the process of evolving onto the main sequence.
Jets, believed to be involved in dissipating angular momentum, are often detected and finally the nuclear processes start, leading to T-Tauri and other visible pre-main-sequence
"The well-determined ages of the meteorites, the theories describing the origin of the solar system, improved to fit recent infrared and radio observations of star-forming regions, and the pre-main-sequence
evolutionary calculations have all combined to permit, for the first time, a relatively precise determination of the age of the sun," Guenther says.
38) is not an old, evolved star but rather a T Tauri variable--a pre-main-sequence
star still partially enshrouded in its molecular cloud.
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.
Normally 16th magnitude, this young, pre-main-sequence
star has been fading by three magnitudes every 48.4 days like clockwork, but for ever-increasing durations since regular observations began in 1996.
KH 15D is a T Tauri star, a young, pre-main-sequence
star with between 0.5 and 1 solar mass.
evolutionary models "are on pretty thin ice."
But we can push back the epoch of binary formation much further by considering newly formed, pre-main-sequence
stars, which have ages of just 1 to 10 million years.
This has been confirmed by a recent near-infrared survey by Mark McCaughrean (Max Planck Institute) and Stauffer, in which low-mass, pre-main-sequence
stars are seen in essentially all of the proplyds.