August 24, 2000
Photo No: H2000-19a
Hubble Spies Brown Dwarfs in Nearby Stellar Nursery
Probing deep within a neighborhood stellar nursery, NASA's Hubble
Space Telescope uncovered a swarm of newborn brown dwarfs. The
orbiting observatory's near-infrared camera revealed about 50 of
these objects throughout the Orion Nebula's Trapezium cluster ,
about 1,500 light-years from Earth.
Appearing like glistening precious stones surrounding a setting of
sparkling diamonds, more than 300 fledgling stars and brown dwarfs
surround the brightest, most massive stars [center of picture] in
Hubble's view of the Trapezium cluster's central region. All of
the celestial objects in the Trapezium were born together in this
hotbed of star formation. The cluster is named for the trapezoidal
alignment of those central massive stars.
Brown dwarfs are gaseous objects with masses so low that their
cores never become hot enough to fuse hydrogen, the thermonuclear
fuel stars like the Sun need to shine steadily. Instead, these
gaseous objects fade and cool as they grow older. Brown dwarfs
around the age of the Sun (5 billion years old) are very cool
and dim, and therefore are difficult for telescopes to find. The
brown dwarfs discovered in the Trapezium, however, are youngsters
(1 million years old). So they're still hot and bright, and easier
This finding, along with observations from ground-based telescopes,
is further evidence that brown dwarfs, once considered exotic
objects, are nearly as abundant as stars. The image and results
appear in the Sept. 20 issue of the Astrophysical Journal.
The brown dwarfs are too dim to be seen in a visible-light image
taken by the Hubble telescope's Wide Field and Planetary Camera 2.
That view also doesn't show the assemblage of
infant stars seen in the near-infrared image. That's because the
young stars are embedded in dense clouds of dust and gas. The
Hubble telescope's near-infrared camera, the Near Infrared Camera
and Multi-Object Spectrometer, penetrated those clouds to capture
a view of those objects. The brown dwarfs are the faintest objects
in the image. Surveying the cluster's central region, the Hubble
telescope spied brown dwarfs with masses equaling 10 to 80 Jupiters.
Researchers think there may be less massive brown dwarfs that are
beyond the limits of Hubble's vision.
The near-infrared image was taken Jan. 17, 1998. Two near-infrared
filters were used to obtain information on the colors of the stars
at two wavelengths (1.1 and 1.6 microns). The Trapezium picture is
1 light-year across. This composite image was made from a "mosaic"
of nine separate, but adjoining images. In this false-color image,
blue corresponds to warmer, more massive stars, and red to cooler,
less massive stars and brown dwarfs, and stars that are heavily
obscured by dust.
Credits for near-infrared image: NASA; K.L. Luhman
(Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.);
and G. Schneider, E. Young, G. Rieke, A. Cotera, H. Chen, M. Rieke,
R. Thompson (Steward Observatory, University of Arizona, Tucson,