An infrared image of a bright, nearly edge-on dusty debris ring around the star HD115600. The ring resembles the Kuiper belt in our own solar system, the region that contains Pluto as well as thousands of remnants of the earliest stages of icy planet formation. The Sun-Pluto distance is projected onto the image for reference. The center of the disk (diamond) appears slightly offset from the location of the star (plus). Credit: Currie et al. 2015
The
Kuiper belt is the region of the solar system situated just beyond
Neptune's orbit, about 40 AU from the Sun (one AU - astronomical unit -
is the Earth's average distance from the Sun). The Kuiper belt is the
location of numerous dwarf planets, such as Pluto, and is also home to
thousands of remnants of the earliest stages of icy planet formation
which provide keys to understanding the early, unevolved solar system.
Beyond the Kuiper belt lies the Oort cloud, a spherical cloud of comets
and icy planetesimals that extends out to perhaps one hundred thousand
AU. Presumably other stellar systems also contain analogs to the Kuiper
belt, and they could help shed light on the Kuiper belt's evolution and
composition. Until now, however, the few such rings that have been
imaged are unreliable analogs; they are seen around nearby stars whose
birth environments are unlike the massive stellar complex where the Sun
was probably formed.
The situation has recently changed with the advent of a new
generation of astronomical imaging instruments on large telescopes that
use adaptive optics to obtain high spatial resolution images. CfA
astronomer Scott Kenyon and his colleagues used the new spectrometer on
the Gemini telescope to study a star slightly larger than the Sun
located about 360 light-years away in a relatively young complex of
massive stars, a region roughly analogous to the Sun’s suspected birth
environment. The star has a large excess of infrared emission, a clear
indication that it hosts a circumstellar dust disk that plausibly is
forming a system of planets.
The astronomers imaged the disk, and found that the debris ring is
confined to a Kuiper belt–like distance from the star. Moreover, they
discovered from the spectrum of its reflected light that its dust has
properties consistent with that of the major constituents of Kuiper belt
bodies -- including water ice. The result provides a promising
reference point for understanding the evolution and composition of the
Kuiper belt, and for the early evolution of the whole solar system.
Reference(s):
"Direct
Imaging and Spectroscopy of a Young Extrasolar Kuiper Belt in the
Nearest OB Association," Thayne Currie, Carey M. Lisse, Marc Kuchner,
Nikku Madhusudhan, Scott J. Kenyon, Christian Thalmann, Joseph Carson,
and John Debes, ApJL 807, L7, 2015.
