Fig 1. Left: J-band polarized intensity (P⊥) images. Right: P⊥ scaled by r2,
where r is the distance in pixels from the central binary, corrected
for projection effects. Both images are shown on a linear scale and
oriented north up and east left. The coronagraph is represented by the
black filled circles.
Astronomers using the Gemini South telescope in Chile have discovered
striking new evidence for planet formation in a dusty disk surrounding a
pair of stars in Sagittarius. The team took advantage of an offering
for Early Science using the Gemini Planet Imager to study infrared light
scattered off dust grains in the disk around the binary system V4046
Sgr. "The Gemini Planet Imager allows us to study nearby planet forming
disks in sufficient detail that we can obtain direct-image evidence for
young planets in orbits similar to those of the giant planets in our
own solar system," says Valerie Rapson of the Rochester Institute of
Technology, who led the research team. Indeed, the GPI imaging reveals
an intriguing double ring structure around the V4046 Sgr binary that is
most likely due to the formation of a giant planet (or planets) at some
4-12 times the Earth-Sun distance (approximately between Jupiter and
Uranus, if orbiting our Sun)."This is perhaps the best such evidence yet
for planet formation so close to a binary system," says Rapson.
Analysis of the data also indicates that the dust grains orbiting the
star are sorted by particle size, as predicted by recent planet
formation models. The result is published in The Astrophysical Journal
Letters and the preprint is at http://arxiv.org/abs/1503.06192, see abstract below.
Abstract:
We report the presence of scattered light from dust grains located in
the giant planet formation region of the circumbinary disk orbiting the
∼20-Myr-old close (∼0.045 AU separation) binary system V4046 Sgr AB
based on observations with the new Gemini Planet Imager (GPI)
instrument. These GPI images probe to within ∼7 AU of the central binary
with linear spatial resolution of ∼3 AU, and are thereby capable of
revealing dust disk structure within a region corresponding to the giant
planets in our solar system. The GPI imaging reveals a relatively
narrow (FWHM ∼10 AU) ring of polarized near-infrared flux whose
brightness peaks at ∼14 AU. This ∼14 AU radius ring is surrounded by a
fainter outer halo of scattered light extending to ∼45 AU, which
coincides with previously detected mm-wave thermal dust emission. The
presence of small grains that efficiently scatter starlight well inside
the mm-wavelength disk cavity supports current models of planet
formation that suggest planet-disk interactions can generate pressure
traps that impose strong radial variations in the particle size
distribution throughout the disk.
Source: Gemini Observatory
