Press Release
Subaru Stares into a Cradle of Stars
February 13, 2001
Low Res. (134 KB) High Res. (1.4 MB) Caption |
Object Name: Star-formation Region S106 IRS4 Telescope: Subaru Telescope / Cassegrain Focus Instrument: CISCO Filter: J (1.25 micron) , H (1.65 micron) , K' (2.15 micron) Color: Blue (J), Green (H) , Red (K') Date: UT1999 May 25, June 5, 6 Exposure: 6 min (J) , 4 min (H, K') Field of View: 5 arcmins Orientation: North up, east left Position: RA(J2000.0)=20h27m, Dec(J2000.0)=+37d (Cygnus) |
Explanation:
Subaru Telescope has successfully taken a sharp and deep
infrared image of the star-forming region, S106. In addition,
many objects with masses less than that of an ordinary star
have been discovered in this region.
S106 is at a distance of approximately 2000 light-years
from the Earth. There is a large massive star called IRS4
(Infrared Source 4) at the center of S106. The star is approximately
one hundred thousand years old, and its mass is approximately
20 times that of the Sun. The hourglass appearance of S106
is thought to be the result of the way material is flowing
outwards from the central star. A huge disk of gas and dust
surrounding IRS4 produces the constriction at the center.
Ultraviolet rays emitted from IRS4 ionize the surrounding
hydrogen gas, creating what astronomers call an HII region.
As the excited hydrogen gas relaxes, it emits the blue glow
we see in the inner part of the nebula. We call this an
emission nebula. The red region towards the edge of the
nebula is a reflection nebula, made as surrounding dust
particles directly reflect the light emitted from IRS4.
Since this infrared image is extremely sharp, we can see
subtle details like ripples inside the emission nebula.
Furthermore, the differences in color and structure between
the emission and reflection nebulae are beautifully displayed.
In comparison, a visible-light image of the same region
taken with the Hubble Space Telescope barely shows any detail
in the upper part of the nebula because visible light is
strongly absorbed by the region's dust.
A study of this deep S106 image has revealed hundreds of
faint young objects around IRS4 and throughout the surrounding
nebula. The mass of these objects is less than 0.08 times
that of our Sun, too small to sustain the nuclear burning
of hydrogen gas that causes a normal star to shine. They
are considered to be young brown dwarfs.
The lightest and faintest objects discovered have an estimated
mass of only a few times that of Jupiter. A joint group
of astronomers from the National Astronomical Observatory
of Japan and the University of Tokyo have observed similar
light objects elsewhere in the sky, in the nearby star-forming
regions towards the constellation of Taurus and Chameleon.
Other researchers have seen such objects in the constellation
of Orion. While such objects would be called "planets"
if they orbited a star, this is not appropriate for these
independent objects. For this reason, we would refer to
them as "floating small objects."
From the observation with Subaru Telescope, it's clear that
many light objects are born out in space along with the
ordinary stars we see, and that the relative number of such
objects differs from place to place. But the birth mechanism
for these objects is still unclear.