We discuss astrophysical puzzles presented by the Sirius system, including the probability that the two stars must have interacted in the past, even though there is no direct evidence for this and the orbital eccentricity remains high.īased in part on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, and from the Mikulski Archive for Space Telescopes at STScI, which are operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The age of Sirius A based on these models is about 237-247 Myr, with uncertainties of ☑5 Myr, consistent with that of the WD companion. Combined with the parallax and the motion of the A component, these elements yield dynamical masses of 2.063+/- 0.023 ⊙, to fit its location on the luminosity-radius plane. A modified version of the PlaSim 3D climate model, designed to simulate planets with Earth-like atmospheric compositions across a wide parameter space, including tidally-locked rotation, 0.1-10 bars surface pressure, and a range of stellar spectra. Using images obtained over nearly two decades with the Hubble Space Telescope (HST), along with photographic observations covering almost 20 years and nearly 2300 historical measurements dating back to the 19th century, we determine precise orbital elements for the visual binary. This threshold has been adopted by the International Astronomical Union as the official transition between planets and brown dwarfs.
HD 38529 c is clearly more massive than 13 Jupiter masses, the threshold above which deuterium fuses to helium. Sirius, the seventh-nearest stellar system, is a visual binary containing the metallic-line A1 V star Sirius A, the brightest star in the sky, orbited in a 50.13 year period by Sirius B, the brightest and nearest white dwarf (WD). Results from HST astrometry are presented in the Table above.
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