True mass

The term true mass is synonymous with the term mass, but is used in astronomy to differentiate the measured mass of a planet from the lower limit of mass usually obtained from radial velocity techniques.cite web | url=http://www.utexas.edu/opa/news/04newsreleases/nr_200408/nr_astronomy040831.html | title=McDonald Observatory astronomers discover Neptune-sized planet with Hobby-Eberly Telescope | publisher=University of Texas at Austin | date=31 August 2004 | accessdate=2007-09-04] Methods used to determine the true mass of a planet include measuring the distance and period of one of its satellites, [cite journal|title=The Mass of Dwarf Planet Eris|author=M.E. Brown and E.L. Schaller|journal= Science|year=2007|volume=316|issue=5831|doi=10.1126/science.1139415|url=http://www.sciencemag.org/cgi/content/full/316/5831/1585|pages=1585] advanced astrometry techniques that use the motions of other planets in the same star system, combining radial velocity techniques with transit observations (which indicate very low orbital inclinations), [cite web| url=http://curious.astro.cornell.edu/question.php?number=710 | title=How do we know the density of some extrasolar planets? | publisher=Curious About Astronomy? | accessdate=2007-09-08] and combining radial velocity techniques with stellar parallax measurements (which also determine orbital inclinations). [cite journal | url=http://www.journals.uchicago.edu/doi/full/10.1086/318927 | title=Preliminary Astrometric Masses for Proposed Extrasolar Planetary Companions | author=Han, I. et al. | journal=The Astrophysical Journal Letters | volume=548 |issue=1 | pages=L57–L60| year=2001 | doi=10.1086/318927 ]

ee also

*Rest mass
*Minimum mass

References