{"release":{"id":"DR1","released_on":"2026-08-21","doi":null,"url":"https://spacecatalog.org/releases#dr1"},"epoch":{"requested":"now","label":"J2026.681","julian_year":2026.681,"time":"2026-09-06T17:55:32.378Z","years_from_j2000":26.681,"frame":"date","applied":"Proper motion, then precession and nutation. The catalogued J2000 position is carried along the great circle the object's own published motion puts it on, at a constant velocity, and the result is referred to the true equator and equinox of this instant. Those are separate things: the motion moves the object, and the rotation turns the grid under it by about fifty arcseconds a year, with nutation adding up to another seventeen.","excluded":"Parallax, the radial-velocity perspective term, aberration and refraction; each is below the accuracy of the catalogued positions themselves. An object with no published proper motion comes back where the catalogue has it rather than at a fabricated zero, and says so with a null pm_ra_mas_yr. A body with no fixed position is not propagated at all — its place comes from an ephemeris, which is what /api/v1/visible answers with."},"slug":"hd-155918-b","name":"HD 155918 b","class":"neptune_like_planet","category":"exoplanet","object_type":"Neptune-like planet","mag":null,"mag_band":null,"abs_mag":null,"abs_mag_band":null,"distance_ly":89.89195926251165,"distance_method":"NASA Exoplanet Archive sy_dist (TICv8, 2019AJ....158..138S)","ra_deg":260.5364025,"dec_deg":-75.349239,"epoch_ra_deg":261.444814,"epoch_dec_deg":-75.374926,"epoch_moved_arcsec":null,"pm_ra_mas_yr":null,"pm_dec_mas_yr":null,"orbits":"HD 155918","semi_major_axis_km":4487936.120999999,"periapsis_km":null,"mass_kg":4.555499040610563e+25,"mass_msun":0.0000229103,"constellation":"Apus","discovered":"2022","featured":false,"url":"https://spacecatalog.org/object/hd-155918-b","radius_km":17029.527000000002,"radius_kind":null,"data_quality":null,"description":null,"properties":{"host_star":"HD 155918","host_v_mag":7,"eccentricity":0.194,"uncertainties":{"mass_kg":[7.592498410971219e+24,5.694373793297995e+24],"distance_ly":[0.07371134136398401,0.07403749774170076],"eccentricity":[0.129,0.197],"host_mass_solar":[0.132,0.132],"host_radius_solar":[0.046504,0.041315],"host_temperature_k":[104.37,107.21],"semi_major_axis_km":[149597.8707,149597.8707],"orbital_period_days":[0.00004,0.00004],"argument_of_periastron_deg":[87.904,140.584]},"host_mass_solar":1.03,"stars_in_system":1,"discovery_method":"Radial Velocity","host_radius_solar":1.01906,"planets_in_system":2,"discovery_facility":"Multiple Observatories","host_spectral_type":"G2V","host_temperature_k":5771.84,"orbital_period_days":1.87567,"periastron_epoch_bjd":2452387.913,"equilibrium_temperature_k":1622.13,"argument_of_periastron_deg":92.251},"designations":[{"catalog":"Exoplanet","designation":"HD 155918 b"}],"source":{"id":"exoplanet_archive","name":"NASA Exoplanet Archive (Planetary Systems Composite Parameters)","url":"https://exoplanetarchive.ipac.caltech.edu/cgi-bin/TblView/nph-tblView?app=ExoTbls&config=PSCompPars","license":"Public domain (NASA)"},"updated_at":"2026-09-02T19:50:56.720Z","attribution":"Data from SpaceCatalog.org. Individual records carry their source and license in `source`; attribution is required for CC-BY and CC-BY-SA rows."}