GeminiFocus January 2019 | Page 14

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