Pre-main-sequence star in the constellation Sagittarius
HD 169142
VLT/SPHERE image of the circumstellar disk and protoplanet candidate b around HD 169142. Credit:ESO VLT/SPHERE - Monash University - Iain Hammond et al., adapted and mixed by Meli_thev
HD 169142 is a singleHerbig Ae/Be star. Its surface temperature is 7650±150K. HD 169142 is depleted of heavy elements compared to theSun, with ametallicity Fe/H index of−0.375±0.125, but is much younger at an age of 7.5±4.5 million years.[2] The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star.[3]
A study using ALMA data found that thewater (H2O)snow line is at around 20astronomical units and the planet b is forming in beyond the water andcarbon dioxide (CO2) snow lines, but within the carbon monoxide (CO) snow line. The CO snow line lies at around 150 AU.[10]
The annular gap and inner cavity observed in this protoplanetary disk both suggested the presence of embedded planets.[2] Several protoplanet candidates have been suggested in the literature starting from 2014.[11][12]
Nonetheless, a particularprotoplanet candidate detected in 2015 and 2017 with theSPHERE instrument on theVLT appears to stand out, hereafter HD 169142 b.[13] A paper from 2023[5] confirmed that the motion of this protoplanet candidate was consistent withKeplerian motion. The object shifted with a change of theposition angle of 10.2±2.8° between 2015 and 2019. The researchers point out three lines of evidence arguing in favour of this object being a protoplanet:
The object is found in annular gap separating the two bright rings of the disc, as predicted in theory
The protoplanet moved between 2015, 2017 and 2019 consistent with Keplerian motion of an object at a distance of about 37 astronomical units from its star.
A spiral-shaped signal consistent with the expected outer spiral wake triggered by a planet in the gap, based on simulations of the system.
The researchers also found the near-infrared colors of the object are consistent with starlight scattered bydust around the protoplanet. This dust could be acircumplanetary disk or a dusty envelope around the protoplanet.[5]
A study from June 2023, using archivedALMA data foundsulfur monoxide andsilicon monosulfide in the disk at the position of planet b. The paper also found compact12CO and13CO emission at the position of the planet. Carbon monoxide and sulfur monoxide were detected in other disks in the past and they are thought to be connected to protoplanets. Silicon monosulfide on the other hand was never before detected in any other disk and can only be detected ifsilicates are released from nearbydust grains in massiveshock waves caused by gas travelling at high velocities. It is thought that planet b is driving anoutflow causing these high velocities.[14][15] Outflows fromproto-jovian planets were hypothesised since 1998.[16]
Outflows are known around isolated young proto-brown dwarfs,[17] but HD 169142 b could be the first confirmed protoplanet around a star showing clear evidence of an outflow. Evidence for inflow or outflows suspected to be caused by planets exist for other disks, such as a signature in theCI gas ofHD 163296.[15]
^abcdeQuanz, Sascha P.; Avenhaus, Henning; Buenzli, Esther; Garufi, Antonio; Schmid, Hans Martin; Wolf, Sebastian (2013), "Gaps in the Hd 169142 Protoplanetary Disk Revealed by Polarimetric Imaging: Signs of Ongoing Planet Formation?",The Astrophysical Journal,766 (1): L2,arXiv:1302.3029,Bibcode:2013ApJ...766L...2Q,doi:10.1088/2041-8205/766/1/L2,S2CID118643209
^Wagner, Kevin R.; Sitko, Michael L.; Grady, Carol A.; Swearingen, Jeremy R.; Champney, Elizabeth H.; Johnson, Alexa N.; Werren, Chelsea; Whitney, Barbara A.; Russell, Ray W.; Schneider, Glenn H.; Momose, Munetake; Muto, Takayuki; Inoue, Akio K.; Lauroesch, James T.; Hornbeck, Jeremy; Brown, Alexander; Fukagawa, Misato; Currie, Thayne M.; Wisniewski, John P.; Woodgate, Bruce E. (2014), "Variability of Disk Emission in Pre-Main Sequence and Related Stars. III. Exploring Structural Changes in the Pre-Transitional Disk in Hd 169142",The Astrophysical Journal,798 (2): 94,arXiv:1410.8606,doi:10.1088/0004-637X/798/2/94,S2CID118745797
^MacÍas, Enrique; Anglada, Guillem; Osorio, Mayra; Torrelles, José M.; Carrasco-González, Carlos; Gómez, José F.; Rodríguez, Luis F.; Sierra, Anibal (2017), "Imaging a Central Ionized Component, a Narrow Ring, and the CO Snowline in the Multigapped Disk of HD 169142",The Astrophysical Journal,838 (2): 97,arXiv:1703.02957,Bibcode:2017ApJ...838...97M,doi:10.3847/1538-4357/aa6620,S2CID119267132
^abBooth, Alice S.; Law, Charles J.; Temmink, Milou; Leemker, Margot; Macias, Enrique (2023-08-13). "Tracing snowlines and C/O ratio in a planet-hosting disk".Astronomy & Astrophysics.678: 13.arXiv:2308.07910.doi:10.1051/0004-6361/202346974.
^Reggiani, Maddalena; Quanz, Sascha P.; Meyer, Michael R.; Pueyo, Laurent; Absil, Olivier; Amara, Adam; Anglada, Guillem; Avenhaus, Henning; Girard, Julien H.; Gonzalez, Carlos Carrasco; Graham, James; Mawet, Dimitri; Meru, Farzana; Milli, Julien; Osorio, Mayra; Wolff, Schuyler; Torrelles, Jose-Maria (2014). "Discovery of a Companion Candidate in the Hd 169142 Transition Disk and the Possibility of Multiple Planet Formation".The Astrophysical Journal.792 (1): L23.arXiv:1408.0813.Bibcode:2014ApJ...792L..23R.doi:10.1088/2041-8205/792/1/L23.S2CID37427761.
^Osorio, Mayra; Anglada, Guillem; Carrasco-González, Carlos; Torrelles, José M.; Macías, Enrique; Rodríguez, Luis F.; Gómez, José F.; D'Alessio, Paola;Calvet, Nuria; Nagel, Erick; Dent, William R. F.; Quanz, Sascha P.; Reggiani, Maddalena; Mayen-Gijon, Juan M. (7 August 2014). "IMAGING THE INNER AND OUTER GAPS OF THE PRE-TRANSITIONAL DISK OF HD 169142 AT 7 mm".The Astrophysical Journal.791 (2): L36.arXiv:1407.6549.Bibcode:2014ApJ...791L..36O.doi:10.1088/2041-8205/791/2/L36.eISSN2041-8213.S2CID119255686.
^Gratton, R.; Ligi, R.; Sissa, E.; Desidera, S.; Mesa, D.; Bonnefoy, M.; Chauvin, G.; Cheetham, A.; Feldt, M.; Lagrange, A. M.; Langlois, M.; Meyer, M.; Vigan, A.; Boccaletti, A.; Janson, M.; Lazzoni, C.; Zurlo, A.; De Boer, J.; Henning, T.; d'Orazi, V.; Gluck, L.; Madec, F.; Jaquet, M.; Baudoz, P.; Fantinel, D.; Pavlov, A.; Wildi, F. (2019). "Blobs, spiral arms, and a possible planet around HD 169142".Astronomy & Astrophysics.623: A140.arXiv:1901.06555.Bibcode:2019A&A...623A.140G.doi:10.1051/0004-6361/201834760.S2CID118873911.
