Figure 4.
The relative position of
the companion object
PDS 70b. The blue
points show the mea-
sured positions from
the Gemini and VLT
data. The red points
(labeled “BG”) show the
positions that would
have been expected
in the VLT data if the
object detected in
the first-epoch NICI
observations had been
a distant background
object, for which the
relative position would
follow the plotted
curve. The offset in
position between the
NICI and later observa-
tions is consistent with
the expected orbital
motion.
[Figure from Keppler
et al., A&A, 617: A44,
2018.]
faint source follows the star, its relative po-
sition measured in the 2012 NICI data does
not coincide precisely with the positions
derived from the VLT observations taken in
2015 and 2016 (Figure 4). This is likely due
to orbital motion over the four-year baseline
spanned by the Gemini and VLT observa-
tions analyzed in the discovery paper. The
inferred orbital motion is clockwise, which is
in the same direction as the disk rotates. A
second study adds an additional SPHERE ob-
servation from early 2018 and finds a best-fit
circular orbit with a period of 118 years.
John Blakeslee is the Chief Scientist at Gemini
Observatory and is located at Gemini South in
Chile. He can be reached at:
[email protected]
The multi-band photometric analysis com-
bining the VLT and Gemini data indicates
that PDS 70b is likely a gas giant with a
mass a few times that of Jupiter and a
temperature of about 1,200 K. Additional
observations of PDS 70b should allow test-
ing of theoretical predictions of the role of
planet-disk interactions in the evolution of
young planetary systems.
12
GeminiFocus
January 2019