Velocity of the sun in the milky way
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Sun's Rotational Velocity in the Milky Way
The velocity of the Sun as it orbits the center of the Milky Way is a key parameter for understanding the structure and dynamics of our galaxy. Multiple studies using different methods and data sources have provided consistent estimates for this value.
Circular Velocity at the Sun's Position
Recent measurements place the Sun's circular velocity—its speed as it moves around the Galactic center—between approximately 218 km/s and 253 km/s. Most studies converge on a value near 230–235 km/s:
- One study using luminous red giant branch stars found the circular velocity at the Sun's location to be 234.04 ± 1.36 km/s .
- Another analysis using trigonometric parallaxes of high-mass star-forming regions determined the Sun's full circular velocity to be about 236 km/s .
- A comprehensive mass model of the Milky Way estimated the circular speed at the Sun to be 232.8 ± 3.0 km/s .
- Using Gaia observations of the Sagittarius stream, the solar reflex velocity was measured at 253 ± 6 km/s, which, after accounting for the Sun's peculiar motion, implies a local circular speed of 229 ± 6 km/s .
- Additional studies using APOGEE data and other surveys report values in the range of 218 ± 6 km/s to 242+10−3 km/s 13.
Variations and Systematic Effects
While the circular velocity curve of the Milky Way is generally flat near the Sun's position, some studies note a gentle decline in velocity with increasing distance from the Galactic center, with gradients of about −1.7 to −1.8 km/s per kpc 35. Systematic uncertainties in these measurements are typically at the 2–5% level 35.
Non-Circular Motions and Local Fluctuations
Non-circular motions—deviations from a perfect circular orbit—are present but generally small near the Sun, typically around 10 km/s or less . However, larger deviations can occur near the Galactic bar or spiral arms 24. Studies mapping local velocity substructure find that the rotation velocity of the disk can vary by up to 20 km/s over short distances, but these are local effects and do not significantly alter the average circular velocity at the Sun's position .
Conclusion
The Sun orbits the center of the Milky Way at a velocity of approximately 230–235 km/s, with most recent and precise measurements clustering in this range. Small variations exist due to local non-circular motions and systematic uncertainties, but the consensus across multiple independent studies is strong. This velocity is a fundamental parameter for models of the Milky Way's mass distribution and dynamics 1345+2 MORE.
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