contrast allow probing more distant Sun-like
systems than previously possible. GPI provides spectra along with the images, and the
results are consistent with a significant water
ice component. The complete work will be
published in The Astrophysical Journal Letters,
and a preprint is now available.
The observed distribution of older (latetype) stars is consistent with earlier results
showing a power law distribution that
breaks at a similar radius, though lacking the
very sharp drop-off the young stars show.
Full results will appear in The Astrophysical
Journal, and a preprint is now posted.
Finding the Outer Edge
of Young Stars Near the
Galactic Center
Catching Supernovae
in Advance
The very center of the Milky Way Galaxy
contains a number of massive stars — despite either the inhospitable environment
for their formation in the vicinity of a supermassive black hole or the short time available for them to relocate there after formation elsewhere. New observations, obtained
using the Near-Infrared Integral Field Spectrometer (NIFS) with laser and natural guide
star adaptive optics, rule out at least one
formation scenario (infall of a young stellar
cluster) and help set the physical scale (0.5
parsecs (pc) or 1.6 light-years) for the extent
of in situ formation.
Morten Støstad (University of Toronto) and
colleagues take advantage of NIFS’s spatial
resolution, along with the simultaneous
spectroscopy it provides, to classify the observed stars. The distribution of early-type
(young) stars exhibits a sharp decline at a radius of about 0.5 pc, which is not a limit due
to the observations.
The earliest observations of supernovae can
distinguish among their formation mechanisms. For Type Ia (SN Ia) events, the progenitor white dwarf may be pushed to become
a supernova by accretion from a companion
or by merger with another white dwarf. Besides being useful to account more fully for
the end stages of stellar evolution, understanding the SN Ia mechanism is extremely
important in their application to cosmology
as standard (or standardizable) light sources.
Two new results find evidence for both of
these SN Ia formation processes in different examples. In both papers, led by Yi Ciao
(California Institute of Technology) and Rob
Olling (University of Maryland), observations
from Gemini and other ground-based facili-
Figure 2.
The NIFS image in the
K band of one of nine
regions analyzed.
The field measures 3
arcseconds across and
is located about 0.4
pc from the Galactic
center. Symbols
indicate spectral types:
Blue triangles (early);
green c