disk. Moreover, the study estimates that the
age of the system exceeds 13 billion years,
which would suggest that the thin disk
may be considerably older than generally
believed. However, the age is based on iso-
chrone fitting to the primary star and is sub-
ject to systematic uncertainty.
In addition to setting astronomical records,
2MASS J18082002–5104378 B is a diminu-
tive star with big implications. The study
argues that the existence of this low-mass
object, as well as a known brown dwarf
within an EMP system, implies that low-mass
primordial-composition stars could form
as members of binaries via fragmentation
within the protostellar disks of the supposed
high-mass Pop III stars. If this is the case, al-
though the primary stars would have long
since burnt themselves out, the liberated
low-mass Pop III secondaries could still be
wandering inconspicuously about our Gal-
axy, just waiting to be discovered.
Gemini’s Role in the Discovery
of the Young Planet PDS 70b
This past July as Gemini Observatory was
preparing for its triennial Science Meeting,
our colleagues at the European Southern
Observatory (ESO) announced the discov-
ery of a planet caught in the act of forma-
tion within the transition disk (a debris disk
with a central gap) surrounding the young
low-mass star PDS 70. The star was targeted
because it was known from previously pub-
lished Gemini and Subaru observations to
host a transition disk with a large central
gap, suggestive of ongoing planet forma-
January 2019 / 2018 Year in Review
tion. PDS 70 belongs to the Scorpius-Cen-
taurus association at a distance of 113 par-
secs (determined from Gaia Data Release 2).
It has an estimated age of 5.4 million years
and a mass of about 0.8 M B . The discovery,
based on observations obtained at the Very
Large Telescope (VLT) and Gemini South,
was published in the September 2018 issue
of Astronomy & Astrophysics.
This is the first time that a young planet has
been caught in the act of plowing out the
central region of a transition disk. “Disks
around young stars are the birthplaces of
planets, but so far only a handful of obser-
vations have detected hints of baby planets
in them,” said Miriam Keppler of the Max
Planck Institute for Astronomy. Keppler led
the large team of over 100 astronomers
who made the discovery. Using the Spec-
tro-Polarimetric High-contrast Exoplanet
REsearch instrument (SPHERE) on the VLT,
the team detected a point source about 22
astronomical units from PDS 70 within the
gap of the surrounding disk. The detection
was confirmed at five different epochs us-
ing three different instruments at wave-
lengths ranging from 1.6-3.8 μm (Figure 3).
The astrometry from the multiple epochs
shows that the object has a very similar mo-
tion to that of PDS 70, and thus is likely a
bound planetary companion.
Figure 3.
Direct images of the
exoplanet PDS 70b,
from left to right:
Gemini/NICI L’-band
(2012-03-31), VLT/
SPHERE H2H3-band
(2015-05-03 and 2015-
05-31), VLT/SPHERE
K1K2-band (2016-05-
14), and VLT/NACO
L’-band (2016-06-01).
North is up and east is
to the left in all images.
[Figure from Keppler
et al., A&A, 617: A44,
2018.]
The crucial first epoch was provided by an
archival L’-band image taken in March 2012
with the Near-Infrared Coronagraphic Im-
ager (NICI) on Gemini South. Although the
faint source follows the star, its relative po-
sition measured in the 2012 NICI data does
not coincide precisely with the positions
GeminiFocus
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