Parallaxes and proper motions of 134 southern late M, L and T dwarfs

groombridge1830_720x956Stars in nearby solar space exhibit large proper motions because they are moving against a background of more distant stars. All stars have their own motion through space and most stars in the solar vicinity share approximately the velocity and direction of motion of the Sun. In the case where a parallax as well as the transverse velocity are known, the knowledge of the exact distance together with the radial velocity yields the precise motion of the star relative to the Sun. The image shows the motion of the nearby star Groombridge 1830, using two images taken a year apart. The ability to determine these basic facts is especially interesting for investigating young brown dwarfs near the Sun, as  a new paper by Weinberger et al., accepted to the Astronomical Journal, elaborates:

We report trigonometric parallaxes for 134 low mass stars and brown dwarfs, of which 38 have no previously published measurement and 79 more have improved uncertainties. Our survey targeted nearby targets, so 119 are closer than 30 pc. Of the 38 stars with new parallaxes, 14 are within 20 pc and seven are likely brown dwarfs (spectral types later than L0). These parallaxes are useful for studies of kinematics, multiplicity, and spectrophotometric calibration. Two objects with new parallaxes are confirmed as young stars with membership in nearby young moving groups: LP 870-65 in AB Doradus and G 161-71 in Argus. We also report the first parallax for the planet-hosting star GJ 3470; this allows us to refine the density of its Neptune-mass planet. One T-dwarf, 2MASS J12590470-4336243, previously thought to lie within 4 pc, is found to be at 7.8 pc, and the M-type star 2MASS J01392170-3936088 joins the ranks of nearby stars as it is found to be within 10 pc. Five stars that are over-luminous and/or too red for their spectral types are identified and deserve further study as possible young stars.

In other news the location of the still putative Planet Nine has been refined to within a twenty degree area centred on RA 2h 40m and declination -15°.

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