Astronomy:Local standard of rest

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Short description: Astronomical reference frame defined by motion of near-Sun stars around Galactic Centre


In astronomy, the local standard of rest or LSR is a reference frame which follows the mean motion of material in the Milky Way in the neighborhood of the Sun (stars in radius 100 pc from the Sun),[1] on average sharing the same velocity around the Milky Way as the Sun.[2] The path of this material is not precisely circular.[3] The Sun follows the solar circle (eccentricity e < 0.1) at a speed of about 255 km/s in a clockwise direction when viewed from the galactic north pole at a radius of ≈ 8.34 kpc[4] about the center of the galaxy near Sgr A*, and has only a slight motion, towards the solar apex, relative to the LSR.[5][6]

LSR could be understood by analogy to a group of cars traveling at similar speed on a highway i.e. at LSR. If a faster car passes by or they pass a slower car then the faster and slower cars could be considered at not traveling at LSR. Typically a large variation of speed in astronomical bodies could be considered as indicator of their extraterrestrial nature. This analogy was used by theoretical physicist Avi Loeb in his 2021 book Extraterrestrial: The First Sign of Intelligent Life Beyond Earth.

The LSR velocity is anywhere from 202–241 km/s.[7] In 2014, very-long-baseline interferometry observations of maser emission in high-mass star-forming regions (HMSFR) placed tight constraints on combinations of kinematic parameters such as the circular orbit speed of the Sun (Θ0 + V☉ = 255.2 ± 5.1 km/s).[4] There is significant correlation between the circular motion of the solar circle, the solar peculiar motion, and the predicted counterrotation of star-forming regions.[8] Additionally, local estimates of the velocity of the LSR based on stars in the vicinity of the Sun[9] may potentially yield different results than global estimates derived from motions relative to the Galactic Center.[10]

See also

References

  1. ↑ Frank H Shu (1982). The Physical Universe. University Science Books. p. 261. ISBN 0-935702-05-9. https://archive.org/details/physicaluniverse00shuf. 
  2. ↑ "LOCAL STANDARD OF REST definition and meaning". November 25, 2023. https://www.collinsdictionary.com/dictionary/english/local-standard-of-rest. 
  3. ↑ James Binney; Michael Merrifield (1998). Galactic Astronomy. Princeton University Press. p. 536. ISBN 0-691-02565-7. https://books.google.com/books?id=arYYRoYjKacC&pg=PA536. 
  4. ↑ 4.0 4.1 Reid, M. (10 March 2014). "Trigonometric Parallaxes of High Mass Star Forming Regions: The Structure and Kinematics of the Milky Way". The Astrophysical Journal 783 (2): 130 (14pp). doi:10.1088/0004-637X/783/2/130. Bibcode: 2014ApJ...783..130R. 
  5. ↑ Mark Reid (2008). "Mapping the Milky Way and the Local Group". Mapping the Galaxy and Nearby Galaxies. Springer. pp. 19–20. ISBN 978-0-387-72767-7. https://books.google.com/books?id=bP9hZqoIfhMC&pg=PA19. 
  6. ↑ The Sun's peculiar motion relative to the LSR is 13.4 km/s. See, for example, Binney, J.; Merrifield, M. (6 September 1998). "§10.6". op. cit.. Princeton University Press. ISBN 0-691-02565-7.  or E.E. Mamajek (2008). "On the distance to the Ophiuchus star-forming region". Astron. Nachr. AN 329 (1): 12; §2.3. doi:10.1002/asna.200710827. Bibcode: 2008AN....329...10M. 
  7. ↑ Steven R. Majewski1 (2008). "Precision Astrometry, Galactic Mergers, Halo Substructure and Local Dark Matter". Proceedings of IAU Symposium 248 3: 450–457. doi:10.1017/S1743921308019790. Bibcode: 2008IAUS..248..450M. 
  8. ↑ Reid, M. (20 July 2009). "Trigonometric Parallaxes of High Mass Star Forming Regions. VI. Galactic Structure, Fundamental Parameters, and Noncircular Motions". The Astrophysical Journal 700 (1): 137–148. doi:10.1088/0004-637X/700/1/137. Bibcode: 2009ApJ...700..137R. 
  9. ↑ Dehnen, W.; Binney, J.J. (October 1998). "Local stellar kinematics from HIPPARCOS data". Monthly Notices of the Royal Astronomical Society 298 (2): 387–394. doi:10.1046/j.1365-8711.1998.01600.x. Bibcode: 1998MNRAS.298..387D. 
  10. ↑ Bovy, J. (10 November 2012). "The Milky Way's Circular-velocity Curve between 4 and 14 kpc from APOGEE data". The Astrophysical Journal 759 (2): 131 (20pp). doi:10.1088/0004-637X/759/2/131. Bibcode: 2012ApJ...759..131B. 

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